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International Hydrofoil Society Correspondence Archives…

Hydrofoil, Rudder, and Strut Design Issues
(See also links to design texts and other technical information sources on the IHS Links Page)
(Last Update: 11 Nov 03)Return to the Archived Messages Contents Page
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Where is Foil Design Data?

[11 May 03] Where do I go for specifics about foil design? As in how do I determine the size, aspect ratio, need for winglets, shape, (inverted T vs. inverted Y vs. horizontal V), NASA foil specification . My plan calls for a single foil fully submerged with all control being accomplished with above water airfoils (pitch, roll, direction). Everything above water is conceptually set, but I have limited understanding / knowledge about foils. I understand that there are arrangements combining a lower speed and higher speed foil on the same vertical column, with some type of grooving on the higher speed foil to prevent cavitation at limited angles of attack. With respect to the website http://www.supramar.ch/ there is an article on grooving to avoid cavitation. I anticipate a limited wave surface (off shore wind) so elevation could be limited, and the initial lifting foil would be unlikely to be exposed to resubmersion at speed. Supramar is willing to guide/specify the grooving at no charge, but I need a foil design for their review or at least that seems to be the situation. I have not actually asked for a design proposal. Maybe I should. Actually it is hard to know if my request would even be taken seriously. They did communicate initially but subsequent emails have been unanswered. Any instruction, constructive criticism, or guidance would be appreciated. Of note the current land speed record for a kite/sail powered tricycle vehicle is just a touch over 72 mph in 40-50 mph winds. — Duncan Coolidge (jcoolidg@tds.net)

Response…[11 May 03] We frequently get requests like this. The answer is not simple, but there is a lot of help within the organization and on the website. I advise first checking out the site, and at the same time order a copy of the Advanced Marine Vehicle (AMV) CD-ROM #1 announced on the site. This CD has a lot of foil design info. — John Meyer (jmeyer@erols.com)

What NACA Series is Best?

[15 Mar 02] I am studying in Naval Architecture Department, Ocean Engineering Faculty, Sepuluh Nopember Institut Of Technology, Surabaya Indonesia. Before I complete my studies, I must do experiments as requirement from my college. I want to experiment with about lift and drag for a foil of a Hydrofoil Craft. This experiment is using Computational Fluid Dynamic (CFD) with ANSYS 5.6. But I am confusing about what NACA Foil Series is suitable for Hydrofoil Craft, and what the principal reason for choice this NACA Series. — Hot Pungka Purba (pungka@yahoo.com)

Response…[15 Mar 02]You haven’t said what the requirements are for your section. Since you mention NACA foils, I assume that you are interested in the subcavitating speed range. You need to have some idea of the range of lift coefficients are required of your foil – this is driven by the load the foil has to carry and the variation in angle of attack the foil will experience as it goes through waves. Something like Cl = 0 to 0.6 with a design Cl = 0.3 would be typical. The intended speed range for the vessel is critical – what are the takeoff, cruise, and dash speeds? And you need to know how the craft will be controlled – will the foils be surface piercing or fully submerged, and will they change incidence or have flaps?

I believe there are four key problems in subcavitating hydrofoil section design. First, you want to avoid separation because this invites ventilation as well as causing drag. Second you want to avoid cavitation. Of course, you also want low drag, and fortunately the things you do to get a high cavitation speed and avoid separation are also good ways to minimize the drag. Finally, the section may be operating close to a free surface, and this modifies the velocity distribution about the foil.

Since cavitation begins when the lowest pressure anywhere on the foil drops below the local vapor pressure of water, you want to minimize the maximum velocity. That means no sharp pressure peaks allowed! At the same time, you want the average velocity over the top surface to be as high as possible so as to produce the most lift. This drives the design to shapes which have long, flat pressure distributions – shaped like building with a flat roof.

The NACA sections which have this type of rooftop velocity distribution are the 6-series laminar flow sections and the earlier 1-series (i.e., 16-012, etc). The 1-series sections have a shallow favorable pressure gradient back to 60% chord, but they have a highly convex pressure recovery that is not necessarily a good characteristic if one wants to avoid separation at the trailing edge. So a comparable 6-series section (say, 66-XXX) would probably be a better bet than the corresponding 16-XXX section.

There are other more modern hydrofoil sections, such as the Eppler designs. Try to get his book, “Airfoil Design and Data”. It is out of print, but your engineering library should be able to find it. He talks about the philosophy of hydrofoil design and has several sections specifically designed to be hydrofoils.

You can also design your own hydrofoils using XFOIL, which you can download for free. XFOIL is more modern code than the Eppler code, but you can still design sections like Eppler’s using XFOIL. This would be a good start to analyzing with ANSYS because ANSYS doesn’t have the inverse design capability of XFOIL but it does have a more powerful analysis capability. So you would be able to compare the experimental results, the inviscid + integral boundary layer results, and the Navier-Stokes CFD results, at least for subcavitating flows.

Simulating the two-phase flow that results from cavitation would be a difficult challenge! But it has been done, and this makes a Navier-Stokes method worthwhile. Unfortunately, much of the research has been done using NACA 4-digit sections (like 0012, 0015), and I suspect this is either out of ignorance as to what makes a good hydrofoil, or perhaps because these are bad hydrofoils and cavitate more easily!

Say you are concerned with a fully submerged hydrofoil with flaps to control the height of the vessel. As the boat flies through waves, the orbital velocity of the waves will change the angle of attack on the foil and thus the lift. The control system will try to compensate for this by moving the flap. If the boat is flying along perfectly level, a good approximation of a perfect control system would be one that maintained a constant lift coefficient on the foil as the angle of attack changed. Thus you need to consider three cases: zero angle of attack with the flap at neutral, positive angle of attack with the flap deflected up, and negative angle of attack with the flap deflected down. The larger the flap deflection, the greater the angle of attack change that can be tolerated while still maintaining the same lift coefficient, and the higher the sea-state in which the ship can operate. For each of these three cases, the peak velocity will occur on a different part of the foil. You would want to design the foil so that the value of the peak velocity is the same in each case. This will give you the highest speed without cavitating. But larger flap deflections and a greater angle of attack range means higher maximum velocities and thus a lower operating speed without cavitating, so there’s a tradeoff between the ability to operate in rough seas and the vessel’s maximum speed. It’s an interesting design problem! But one that comes back to knowing the original requirements in order to design (or select) the appropriate section.

Take a look at …

— Tom Speer (me@tspeer.com) website: www.tspeer.com

Just after I pushed the “Send” button for the preceding email, I found a good link about using Fluent to calculate cavitating flows, but I didn’t save the link. I can probably find it again if anyone is interested. I’ve also thought some about why the 16-XXX sections are so popular for hydrofoils over the 6-series, and I think it must be because they have a much thicker and stronger trailing edge. So perhaps I was too hasty in recommending the 6-series because they may not be practical for the very high loadings of hydrofoils. Flexing of the trailing edge can lead to singing, too. By the way, there are some interesting papers at U. Mich. on their large-scale hydrofoil (8′ chord!) test. — Tom Speer (me@tspeer.com) website: www.tspeer.com

Foil Design Guidance Needed

[4 Feb 02] I am restoring and optimizing a 1969 Irwin 24. Its keel has an “L” design fin and ballast torpedo. The foil consists of a one inch thick steel plate encased in fiberglass and faired to a section that is similar to NACA 00-series sections through station 6; then tapers to a blunt trailing edge. I have some experience with symmetrical foil optimization; however always with sections in the 8% to 12% thickness range (and no data on less than 6% thickness). I have never implemented a foil less than 7% (even when strength and ballast were not considerations) and I am contemplating taking one of two options:

  1. Maintaining the thin section, leaving the foil in tact (excepting minimal fairing) through section 6, tapering the trailing edge to 1/16th inch and squaring off (this may require increasing the span ~3 inches); making the foil a very close approximation of a NACA 00-series section with 4% thickness.
  2. Building up the existing foil section to a NACA 0006 or NACA 0008 section (this may require increasing the span ~1 inch and add approximately 100 pounds to the displacement).

Option 1 is far less work, but would change the plan form design slightly. I am not particularly worried about moving the center of lift slightly back because I have removed a 6 inch deep skeg that was a retrofit between the keel and rudder. In any event I am keen on cleaning up the trailing edge. Option 2 would be a good deal of work that would require some benefit to justify undertaking. The plan form data on the keel is as follows: Span = 24 inches, Chord = 45 inches, Max thickness = 2 inches, Sweep Angle = 45 degrees. The torpedo height is 12 inches, the torpedo is V shaped where it meets the foil (120 degrees at the foil interface and the at the bottom) and has a total length of 58 inches. Total displacement is 3000 pounds. Thanks for any guidance you can afford me. — Tom Graham (TGraham@entergy.com)

Response…[6 Feb 02] Paul Bogataj had an article in Sailing World a while back concerning keel sections and leading edge shapes. I’d download XFOIL and use it to look at different sections. You can put in your section as it is, NACA sections for comparison, and use it to make modifications to either. — Tom Speer, F-24 AMA DEUS (me@tspeer.com) website: www.tspeer.com

Rudder Cavitation Design

[3 Feb 02] The rudder cavitation article in the Winter 01-02 Newsletter got my interest. The hydrofoil strut has a similar sea state problem. We tailored the strut section pressure distribution along the strut to reduce its cavitation sensitivity. If you are interested I would be glad to talk with you about the work we did. My comment is based on the ongoing research effort we had at Boeing Marine Services (BMS) relating to hydrofoils. The research combined our hydrofoil experience with the aero capability imported from our airplane organization. The work was reported in Boeing documents and IRAD reports-David Taylor was always on the distribution list. We presented a paper at the 19th Tow Tank Conference giving a brief report on the Jetfoil forward foil. — Bob Dixon (dixon.bob@comcast.net)

Responses…[3 Feb 02] I’d like to hear more about it. I wonder if many strut “cavitation” problems are really ventilation problems, and if what one would do with the pressure distribution would be somewhat different in the two cases. To prevent cavitation, did you try to cap the peak velocity by using a roof-top pressure distribution, carried as far aft as possible? This would also be consistent with natural laminar flow control. — Tom Speer (me@tspeer.com)

[3 Feb 02] Thanks for the info. All of the Boeing reports are in the Advanced Ship Data Bank at NSWCCD (David Taylor). Do you have a copy of the paper from the 19th Towing Tank Conference? That may not be in the Data Bank. If you could send it, I would copy it and send it right back. It may be good to include in the next AMV CD we may be putting out at IHS. — John Meyer (jmeyer@erols.com)

Turning Circle Explanation

[25 Nov 01] I need a brief explanation about measuring the turning cycle of a ship (HSLC). — Yuksel UNAL (yunal@ssm.gov.tr)

Responses…[25 Nov 01] The answer to the question can be found in Vol. III of SNAME’s Principles of Naval Architecture, pp.316 and Fig.157. — Bill Buckley (wbuckley@erols.com)

[25 Nov 01] You have asked about the measurement of the ‘turning cycle of a ship’ and I presume this is a reference to the Turning Circle performance. A ship’s turning performance is defined by parameters such as the advance, transfer, tactical diameter and steady turning diameter and speed. These are defined in naval architecture text books. For any particular ship, they are a function of the initial speed and the angle of the rudders (or waterjet) that is applied. The distances are often defined relative to the length of the ship itself, so for instance a ship may have a tactical diameter of 5 ship lengths after applying full rudder angle while at maximum speed. In the past, such parameters were measured by taking position fixes to nearby stationary objects or by the use of radio ranging equipment. It is more common practice these days to measure such maneuvering parameters on trials by using Differential GPS equipment reconnected to a data logger. More information on the conduct of maneuvering trials is available in such documents as the “Guide for Sea Trials” that can be purchased from the Society of Naval Architects and Marine Engineers (SNAME) who’s website is at www.sname.org. Details of that publication extracted from their website are as follows: Guide for Sea Trials: Covers sea trials of self-propelled surface ships displacing 300 tons or more, powered by fossil fuel and driven by steam turbine, gas turbine, diesel engine or electric motors. It does not cover dock trials or tests or demonstrations which can be conducted dockside, which are covered in T&R Bulletin 3-39, Guide for Shop and Installation Tests. [3-47] 1989, 95 pp. List Price: $38.00; Member Price: $19.00. Available by photo reproduction only. — Martin Grimm (seaflite@alphalink.com.au)

[26 Nov 01] Are you talking about “tactical diameter”, “advance and transfer” as explained in any seamanship textbook like Crenshaw’s? — CAPT Peter Squicciarini (Dsquicciarini@acu4.spear.navy.mil)

Taig’s ALF

[11 Nov 01] Here are pictures of a friend’s foil sailboat called ALF by Alistair Taig. Mr. Taig has a unique solution to automated attitude control using dynamic pressure rather than a surface skimmer. Click Here to view an article (in Adobe Acrobat format) that he wrote about that. — Ron Drynan (info@humanpoweredboats.com) website: www.HumanPoweredBoats.com

Response…[11 Nov 01] I liked his analysis of the steady state gain in his feedback control system. I wish more amateur designers did analyses of this kind. A fully submerged foil that operates at constant lift coefficient is basically one that maintains its angle of attack, much like a fixed foil would if the craft were flying with a constant pitch attitude. However, the effect of his spring would be to modify this relationship. A spring which applied a nose-up moment on the foil would result in a larger lift coefficient at low speed and a lower lift coefficient at high speed, which is in the direction necessary to trim the craft. With the right spring constant it would act like a feedforward term in his control system to trim the foil and reduce the dependence on his pitot tube feedback. This is a spring which acts in the opposite direction that he suggests. Personally, I would be more concerned about sizing the spring for after takeoff and less concerned about speeds below takeoff. The pilot can manually override the system to get low drag hullborne, and then release it for takeoff. I think he’s going to be in for an interesting time when he gets it flying! Tuning the lag in the pitot-tube feedback will be tricky – it has to be enough to put the break frequency below the wave frequencies he’s trying to reject, but the bandwidth still has to be high enough to stabilize the heave of the boat. And if the lag is too much, the phase lag will destabilize his system. However, the idea that the roll-off in vehicle response will attenuate the wave disturbance is valid. His pitot-tube will act rather like a bang-bang system as it dips in and out of the water, and this may lead to a limit cycle oscillation. However there may be enough dithering from wave action to smooth this out. — Tom Speer (me@tspeer.com); website: www.tspeer.com; fax: +1 206 878 5269

Yawl Leeboard Foil Design Recommendation Needed

[9 Nov 01] I have a 28 ft Shearwater yawl build by Edey & Duff in 1987. It is designed to have a pair of pivoting leeboards suspended outboard on each side instead of a centerboard or fixed keel. The standard leeboards measure about five ft long and 32 inches across the lower end. they are flat in section with a rounded leading edge and a tapering trailing edge. One of my leeboards fractured rolling in big seas on lake Michigan, and instead of purchasing a replacement from E&D I want to make a new pair exhibiting improved performance. Both the designer and builder favor simple, low-tech, short and flat leeboards for sailboats, claiming that foil sections are not worth the bother. However, another owner of a boat like mine, a friend in Barnegat, NJ, did construct a pair of custom leeboards for his boat and their performance is remarkable. His boat is considerably faster than mine, and makes much less leeway when sailing to windward. Proof enough for me! Of course he is also a very good sailor. Rather than copy his work line for line, I am trying to search out as much about underwater foils as I can, and am finding this a daunting task. I know, for instance that a few of today’s high performance scow sailboats and catamarans are using foil bilge boards for lift to windward by virtue of the fact that only the leeward board in in the water while the windward has lifted above the water due to heel. Two specific questions I have are:

First, what NACA foil section would be appropriate?

Secondly, what angle-of-attack would be most effective for that section? The top speed of a Shearwater in a fresh breeze over smooth water is about seven ot eight knots on a reach and five knots to windward, which is slower than high-performance scows and catamarans.

I have found advice recommending the NACA-0012 foil as being very good for symmetrical foils with zero- angle-of-attack. I have also found information indicating that when a foil that thick has its pitch increased, that trailing portion of the windward side might exhibit flow separation. I know that my friend has thinner foils than a NACA-0012, measuring 1 1/2 inches thick with an 18 inch chord and that they are asymmetric, with a chord ratio of 60%/40%. I do not know what positive angle-of-attack he has used (only the leeward board is used on these boats, while the windward one is drawn up out of the water), only that there is a small amount of “toe-in”. I would very much appreciate any guidance you might provide. — Nichilas “Moby Nick” Scheuer; Rockford, IL; (mobynick@juno.com)

Response…[4 Dec 02] I am currently building a Bolger/Storey Chebacco 25 origionally designed with a centreboard , however “fools rush in … etc. ” and I’ve gone with a change to leeboards. How is your project going? and would you have any info that I might find useful ? Your response anticipated and appreciated. — Simon Jones (sjones@sa.Apana.org.au)

Hull Drag Characteristics at Take-Off

[22 Oct 01] I am presently dealing with the design of a hydrofoil boat with fully submerged hydrofoils. The foil section design as well as the strut design are already well established but the hull design is still under development. Since the craft will be powered by a water jet system very similar to the Jetfoil propulsion system, the hull resistance near take-off speed seems to be critical for the overall power requirements according to my calculations (hump speed power). I have not found any reliable literature information regarding the hull resistance characteristics from standing to take-off speed. Of special interest is the hull resistance decrease when lifting the hull off the water near take-off speed. An article from Charles G. Pieroth/Grumman Aerospace Corporation dealing with ‘hydrofoil hullform selection’ published in Hovering Craft & Hydrofoil in 1977 does just give general recommendations. Also on the IHS-homepage I could not find further useful information. Can anyone provide me with more detailed information? — Sebastian Muschelknautz (Sebastian.Muschelknautz@Linde-VA.de)

Responses…[22 Oct 01] I don’t know if the following will be of assistance, but you may like to look at these papers:

Sakic, Prof Dr Vinko (Maritime Institute, Split); ‘Approximate determination of the propulsive power of small hydrofoil craft’, High-Speed Surface Craft, March 1982. (This discusses resistance in hullborne mode and transfer into foilborne mode but only over about two pages).

Latorre, Dr Robert; ‘Hydrofoil Craft Performance Calculation’, Naval Engineers Journal, March 1990. (again, this addresses performance on take off).

Finally, the Maritime Research Institute Netherlands (MARIN) once offered for sale a program for the hydrodynamic design and analysis of hydrofoil craft in calm water called ‘HYDRES’. This included “the calculation of the resistance for hullborne, take-off and foilborne speeds”. It was apparently based on the use of Series 65 hard chine planing hullforms. Further details may be available via the MARIN website but I have not checked that. — Martin Grimm (seaflite@alphalink.com.au)

Source of Foil Profiles

[3 May 01] Je fais partie d’un groupe d’élèves ingénieurs qui étudie l’hydroptère. Je recherche des données sur le profil EPPLER817 que nous avons utilisé pour réaliser le foil de notre maquette. Je ne parviens notamment pas à trouver les courbes de Cz et Cx en fonction de l’incidence pour ce fameux profil. Je vous serais donc très reconnaissant si vous pouviez m’aider dans ce domaine. (I am part of a group of students engineers that studies l’hydroptère. I look for the view of the profile EPPLER817 that we used to realize the foil of our maquette. In particular, I do not find the curves Cz and Cx incident to this fine profile. I am therefore very appreciative if you could help me in this area) — Elie Daguet (Elie.Daguet@etu.enseeiht.fr)

Response…[3 May 01] The data may be found at www.nasg.com/afdb/index-e.phtml. There you’ll find data for the following hydrofoil sections:

  • Eppler E817(E817)
  • Eppler E818(E818)
  • Eppler E836(E836)
  • Eppler E837(E837)
  • Eppler E838(E838)
  • Eppler E874(E874)
  • Eppler E904(E904)
  • Eppler E908(E908)
  • Speer H105(H105)

The most complete database of section coordinates is at the UIUC Airfoil Data Site. With the coordinates from there and XFOIL (http://raphael.mit.edu/xfoil/), one can generate the data for precisely the conditions desired. — Tom Speer (me@tspeer.com); website: www.tspeer.com; fax: +1 206 878 5269

Paravane Questions

[3 Sep 01] I read Phil Morris’ comments about a paravane. I have had the same idea myself, as mentioned at Jon Howe’s forum at the speedsailing pages. It appears his foil is a supercavitating one. Also an interesting (and pretty) approach is the “jellyfish foiler”, although what will happen when the luff-ward foil slips? I suspect the pivot point will now be the lee-ward foil, and the whole craft may bury or make a judo. I would like to know from Phil Morris if he has had any progress in his research on making a “water-hook”. Also I have read somewhere that it has been tried (as I understood it) in combination with a wakeboard and a kitesurfing kite (by whom, I don’t know, I think it was one of the foil-chair or -ski manufacturers), but they couldn’t control it in high speeds. No details on the setup were given. — Sigurd Grung (mermade@frisurf.no)

“Glide Ratios”

[3 Apr 01] I’m assessing high-speed sailboat designs, using the expression for maximum wind-factor asymptote, 1/( (1/Ga) + (1/Gh) ). This requires reasonable values for aerodynamic and hydrodynamic glide ratios, Ga & Gh. I have no trouble finding glide ratios for airfoils, subcavitating foils, and planing steps, but where do I find data relating aspect ratio and angle of attack to glide ratio for supercavitating foils? I need reasonable, but not exact values, within 20% or so. Some suggest using one-third the glide ratio of a subcavitating foil, but… is the planing step glide ratio a better approximation? — Phil Morris (phil.morris@alum.mit.edu)

Responses…[4 Apr 01] The reference to ‘glide ratio’ is unusual but it actually corresponds to the overall lift-to-drag ratio of the airfoil / hydrofoil (or aircraft / boat) in question. For instance, a high performance glider has a glide ratio of 1:40, i.e. in still air, it will drop 1 metre in altitude for every 40 metres in horizontal travel. To achieve such a good glide ratio, the drag of the whole glider has to be no greater than 1/40 of its lift (which is equal to its weight). A lot of work was done on supercavitating hydrofoil sections for US Navy hydrofoil projects in the 60s and 70s timeframe. You would find some of it published in the Society of Naval Architects and Marine Engineers (SNAME) journals such as Journal of Ship Research. One main researcher in the field was Marshall P. Tulin. You are right that the glide ratio (lift to drag ratio) of supercavitating foils is not generally as good as fully wetted foils so your use of 1/3 of the glide ratio is at least tending in the right direction. The glide ratio will vary considerably as a function of the angle of attack of the foil. The greatest glide ratio is achieved for relatively small angles of attack on typical airfoils such as on gliders. — Martin Grimm (seaflite@alphalink.com.au)

[3 Apr 01] I believe by glide ratio you means the lift/drag ratio. A sailplane’s glide ratio is the same as its L/D. The equation you listed is the correct performance relationship for a sailing vehicle, but you have to ensure that the lift and drag you plug in is the lift to the side (in the horizontal plane and perpendicular to the oncoming flow direction) and the total drag. The vertical L/D is irrelevant except that it dictates the drag that will be added into the total. With hydrofoils it’s easy to get confused, because the L/D one has to use in the performance equation is really the lift of the strut divided by the total drag. Since you didn’t ask about the strut, I will not get into a long discussion on the topic. I also don’t have the parametric design information for which you’re asking! Here’s what I have been able to put together on the feasibility of high speed supercavitating sailing hydrofoils.

  • The best supercavitating foil performance I’ve found (and admittedly I don’t have much to draw from) was a T-foil and strut designed for operation at 60 kt and tank tested at the Lockheed Underwater Missile Facility. Aspect ratio was 5, taper ratio was 0.5, and the foil was swept back so that the trailing edge was straight. The section was 7% – 7.5% thick. That foil’s design takeoff speed was 35 kt, where it had an L/D of 13 at a lift coefficient of 0.5 based on the wetted section. At high speed, the chord was effectively less due to the aft 20% or so on the lower surface not being wetted (the structural annex portion). It required a lift coefficient of at least 0.2 to avoid wetting of the upper surface at high speed. It achieved an L/D of 9 at a speed of 65 kt and a depth of one chord. An 18% thick parabolic strut tested for side force at 70 kt had a maximum side force coefficient of 0.1 at one chord depth and a leeway angle of 4 degrees. Strut chord is typically 50% bigger than lifting foil chord due to the taper in the latter. So adopting this same design to support a sailing hydrofoil, at high speed, the maximum sideforce is 15% of the lift. L/D for sideforce is probably around 5 at best. The total drag divided by the sideforce gives a ratio of 1.06, for a “drag angle” [arctan(D/L)] of 46 degrees. Even if the aerodynamic L/D were 10 (which is probably twice current practice), this results in an apparent wind angle of 52 degrees and a top boatspeed/windspeed ratio of 1.3, so the required wind speed would be 46 kt to achieve the 60 kt the design speed of the foils. At a depth of 3 chords and assuming the lateral L/D also went up to 9, the achievable sideforce is 90% of the weight, the transverse drag angle of the foils is 13 degrees and the apparent wind angle is 19 degrees, for a boatspeed/windspeed ratio of 3 and a true wind speed of 23 kt. This is about the same performance as a competitive land yacht in these winds, operating on a smooth flat surface. So these numbers have to be considered as highly optimistic at best and the feasibility of the supercavitating hydrofoil is a long shot.
  • Here’s another example of supercavitating hydrofoil design that shows how sophisticated one’s design capabilities have to be. One can make a guess at possible performance, as I’ve done above, but to actually achieve those numbers requires the ability to accurately compute the details of the drag components. Hydronautics designed a helicopter-towed minesweeping sled that had 4 ladder foils at the corners. Each ladder had three foils – one subcavitating, one base-ventilated, and one supercavitating. The central strut was a modified parabola (parallel surfaces at the trailing edge) canted 25 deg from the vertical. The top rung and a diagonal strut were a 16(35)04 section (4% thick subcavitating NACA design), the base ventilated rung looked to be a cambered parabola with nearly a delta planform, and the bottom rung was a tapered, swept-back planform with a sizeable annex (rectangular structural addition) behind the wetted supercavitating portion. At light weight (27,000 lb), takeoff was around 22 kt and the drag was nearly constant out to 80 kt with a bit of a rise from there to 100 kt. At heavy weight (40,000 lb), takeoff was around 25 kt and the helicopter had enough thrust to pull it to 70 kt. L/D was 7.5. “The most significant problems which had to be overcome related to achievement of full ventilation of the strut, base ventilated, and supercavitating foil. Positive air channels were finally provided at the strut base in the vicinity of the upper and and middle foil-strut intersections. These changes which were necessary to insure the ventilation assumed in the basic design, improved the lift-drag ratio achieved by incomplete ventilation (for full submergence) by approximately 30 percent. The highly swept supercavitating wing was originally designed without twisting the wing to account for the induced effects of sweep. When the wing was twisted to account for sweep-induced effects, the optimum lift-drag ratio was increased by approximately 40 percent!” [quoted from: Johnson, Virgil E., and Scherer, J. Otto, “Some New Results of Research on High Speed Hydrofoils,” Hydrofoil Symposium Held at the 1965 SNAME Spring Meeting, Seattle Washington.]

The same paper has a chart showing a supercavitating foil stalling at 80% of cruise speed when maintaining lift through incidence control, flying down to 57% of cruise speed when fixed but extended with a 60% chord trailing edge flap, and operating down to 50% of cruise speed with both the flap and incidence control. Drag at that condition was about 5X that at cruise. This might give some guidance as to what’s reasonable in the way of takeoff speed with supercavitating foils and variable geometry. — Tom Speer (tspeer@tspeer.com) website: www.tspeer.com fax: +1 206 878 5269

Follow Up…

[21 Apr 01] My specific interest is not so much for vehicle support, but wind propulsion. So, the foils are indeed turned up spanwise vertical to generate principally lateral lift (like sails and centerboards). One of the proposals I’m trying to assess is a supercavitating paravane. It’s basically a centerboard detached from the boat, and flown like a kite underwater (but sideways, like a skier outside the wake). In the abstract, it has some striking similarities to Tom’s minesweeping sled. So, the datums he provides for supercavitating L/D between 5 and 9 are quite helpful. Moreover, those insights let me know that yes, it is *theoretically* possible for high-speed sailcraft to attain both high speed and high wind factor (4 to 8) with supercavitating centerboards. The lateral lift application doesn’t have an actual take-off problem to deal with. But, my engineering skepticism still remains, centered around cavitation transition and ventilation issues. While I slowly admit that some of these high-speed sailing schemes are possible, their success seems to require some pretty spectacular engineering. — Phil Morris (phil.morris@alum.mit.edu)

Seakeeping / Motion Sickness Graphs

[30 Mar 01] The seakeeping performance of fast ferries is often illustrated by way of graphs of RMS vertical acceleration levels (typically expressed in g’s) versus motion frequency for particular sea conditions. To illustrate this I am including such a plot as obtained from a Rodriquez brochure for the RHS 160F series of surface piercing hydrofoils. As can be seen from the graph, the acceleration levels of the hydrofoil (presumably at its CG location) are indicated for a range of relative headings to the waves for a frequency range from 0.1 Hz to 8 Hz. On top of this are indicated the limits for 10% motion sickness (ie the MSI level, although exposure period is not indicated on the graph) and also ISO limits for human exposure to vibration at higher frequencies. I would like to ask how these graphs are generated as it is not clear to me exactly what they are illustrating.

Real ships operate in irregular waves where there is not a constant encounter frequency or wave height with every successive wave which is encountered by the ship. Only in model tests can regular waves with a single height and period be generated to establish the performance of model boats or ships in under idealized regular conditions. The Rodriquez graph suggests the data is for Low Sea State 6 seas (Significant Wave Height of 4m or more but well less than 6m). As this is an irregular seaway, I am not clear of the meaning of the unbroken plots of RMS vertical acceleration over the large range of frequencies from 0.1 Hz to 4 Hz (corresponding to encounter periods from 10 seconds down to 0.25 seconds) that are given for the craft at various different relative headings to the wave direction. It seems to me that it may be some sort of de-composition of the irregular motion data from sea trials back into a response for a series of theoretical regular wave conditions? If that is the case, then what is the meaning of comparing these ship response curves with the various Motion Sickness Index (MSI) or ISO vibration limits?

What I would have expected is that each run from sea trials in a particular seaway would generate a single data point only on the graph of RMS acceleration versus modal encounter frequency. Runs into head seas in a given seaway would have a higher modal encounter frequency than beam seas which in turn would be higher than the encounter frequency for runs in following seas where the ship and waves are traveling in the same direction.

RHS 160F  - Graph of Rough Sea Behaviour

I have only used the Rodriquez graph as an example to illustrate my uncertainty. Various designers and builders of fast catamaran and monohull ferries have used a plot format almost identical to that of Rodriquez for their hydrofoils, hence there must be a logical explanation of the interpretation of such graphs. I would welcome a reply which helps to explain it. My understanding is that the original tests on volunteers in a test rig to establish trends in the occurrence of motion sickness were performed at various regular frequencies of vertical motions. I have never properly understood how the jump has been made from this data to the case of irregular vertical motion exposure although I am familiar with the formula that should be used to calculate MSI levels for irregular vertical motions such as in a real seaway. Can anyone give suggested references which will also help to clarify this for me? — Martin Grimm (seaflite@alphalink.com.au)

Responses…[1 Apr 01]Here’s my take, based on reading Vol. III of “Principles of Naval Architecture” – maybe some of the NAs out there can fill in or correct this:

  • The graphs you’re looking at are wave response spectra, not the response to the boat to a particular set of waves. These are really averages over all random seas. Note that the units are RMS g’s – the average of the acceleration squared – which is much like a standard deviation.
  • There are idealized wave height spectra which are based on oceanographic research. Typically these show the wave height-squared vs. frequency for different sea states or wind conditions (assuming the wind has been blowing for a long time over a wide area). There are even specialized wave height spectra for different parts of the world, such as the North Sea. These spectra are for regular waves, in which all the waves are marching in the same direction.
  • In addition to the wave height spectra, there are also wave direction spectra which account for the fact that the waves in a random seaway can be coming from a variety of directions, but there will still be a direction from which most of the waves are coming. So when you multiply the wave height spectrum by the wave direction spectrum, you end up with a composite spectrum for a random seaway as a function of both wave length (or frequency) and direction.
  • I would guess the plot you’ve shown is probably based on a wave height spectrum for an open ocean seaway with a significant wave height of 4 m (the average of the highest 1/3 of the waves) – the plot is labeled “Sea S. Low 6”, and a sea state 6 would have a range of 4 – 6 m with an average of 5 m. It could also be from a random seaway with the wave directions distributed in, say, a cosine-squared fashion about the dominant direction. This defines the operating environment.
  • For a given boat, one can calculate the dynamic response to a given wave of a given size from a given direction. If the boat is subjected to the same wave for a long time, the boat response will settle down to being a sine wave of the same frequency but possibly a different amplitude and shifted in phase (the peaks of the boat response won’t occur at the same time as the peaks in the wave). Above a certain frequency, the boat will be increasingly unresponsive to the wave because it is too massive to follow it. At very low frequencies, the boat will follow the wave almost perfectly and the boat response will be the same as the wave. In between, there may be a resonant frequency at which the boat’s response will actually amplify the wave. This response of the boat to waves of a given frequency is given in terms of response amplitude operators, or RAO’s, which are the ratio of the size of vertical response of the boat to the size of the wave. There’s a different RAO for every point on the boat – for example, the bow RAO is greater than the one at the center of gravity because the bow moves up and down as the boat pitches. The total response of the boat comes from summing the individual responses of the boat to the individual waves.
  • So when you multiply the wave spectrum times the RAO as a function of frequency, what you get is another spectrum which represents the statistics of the boat’s motion to a random seaway. This is what you’re looking at in the plot. One could also generate the same results by running a simulation of the boat in a seaway and repeating the simulation many times (hundreds or thousands) with random variations in the sea and averaging the results (a Monte Carlo analysis).

I have a question of my own regarding the graph: I have seen the same boundaries for acceleration used in other reports, and I believe they are described in an ISO standard. However I’ve not been able to find it. Can anyone provide me with the standard? — Tom Speer (tspeer@tspeer.com) website: www.tspeer.com fax: +1 206 878 5269

[3 Apr 01] I was able to put my hands on relevant documents fairly quickly. In the Rodriquez graph, the motion sickness limit curve on the left and vibration limit curves on the right come from ISO 2631-1978 (E) “Guide for the evaluation of human exposure to whole-body vibration,” Second edition 1978-01-15, and a later amendment and a later addendum. As close as I can determine quickly, the motion sickness curve is for 10% of the crew sick in a 4-Hour exposure. The curves were derived from human performance experiments in ship motion simulators to be compared with a 1/3-octave analysis of ship motion spectra – in this case, the vertical acceleration at some specified location on the ship. In the case of fast ferries, ride comfort is a primary concern. And this type of a plot shows the frequencies at which the human body is most susceptible to motion sickness and most sensitive to structure-borne vibration (from machinery and hull pounding in heavy seas, for instance). To derive a single-value criterion for design studies, we analyzed the ship motion spectra of frigates and destroyers in heavy seas. In cases where the peak in the motion spectra reached the sickness limit curve, we integrated the motion spectra and found limit values clustered around a root-mean square (RMS) average of 0.2 G vertical acceleration. The analysis of high-speed craft would likely yield a different single value. Now to the documents, the base ISO 2631-1978 (E) and Amendment 1 of 1982-04-01explain the “Fatigue decreased proficiency” end of the spectrum – 1.0 Hz and above. Addendum 2 “Evaluation of exposure to whole-body z-axis vertical vibration in the frequency range 0.1 to 0.63 Hz,” of 1982-05-01, explains the motion sickness range – though the limit curves are shown as linear “buckets.” The smooth curves, from which Rodriquez picked one, were shown in the human performance analysis reported by O’Hanlon, J.F. and McCauley, M.E., “Motion sickness incidence as a function of the frequency and acceleration of vertical sinusoidal motion,” Aerospace Medicine, April 1974. — John H. Pattison

Follow up…

[3 Apr 01] To Tom Speer: I believe I have a copy of the standard you are seeking details for, but can’t trace it at the moment. Here are a pair of references to that standard from another document I have. I don’t know if it has been updated since:

ISO 2631/1-1985(E), “Evaluation of Human Exposure to Whole-Body Vibration – Part 1: General Requirements”, 1985, International Organization for Standardisation.

ISO 2631/3-1985(E), “Evaluation of Human Exposure to Whole-Body Vibration – Part 3: Evaluation of Human Exposure to Whole-Body Z-Axis Vertical Vibration in the Frequency range 0.1 to 0.63 Hz”, 1985, International Organization for Standardisation.

It seems part 1 deals in part with the range of frequencies above 0.63 Hz but I can’t be sure. My feeling is that this is more associated with vibration due to propulsion machinery on larger merchant ships than with wave induced whole ship motions. The standard was drafted in around 1972 and first released, already as ISO 2631, in 1974 with the title “Guide for the Evaluation of Human Exposure to Whole-Body Vibration”. Although I have never come to terms with the various models of the effect of ship motions on humans, I found that the approach proposed by the late Peter R. Payne seemed to have an elegant unified approach across the whole frequency range. He also came from a background of planing craft and hydrofoil design so would have had high speed craft motions in mind. For details, see:

Payne, Peter R., On Quantizing Ride Comfort and Allowable Accelerations, paper 76-873, AIAA / SNAME Advanced Marine Vehicles Conference, Arlington, Virginia, 20-22 September 1976.

Back to my seakeeping / motion sickness question: If you indeed believe the Rodriquez data I used as an example is a motion response spectrum where the actual measured irregular time trace of acceleration has been de-composed into its frequency components, then that is also the way I viewed it except that I didn’t say so as clearly in my original question. Going on from this common interpretation we have made, I feel that doing this spreads the total ‘energy’ associated with the acceleration time trace across a large frequency range and thus makes the resulting plot appear as having a far lower magnitude of acceleration than if a single equivalent RMS acceleration based on the complete irregular acceleration time series had been plotted at a single frequency corresponding to, say, the average frequency of the acceleration peaks in that irregular signal. The current approach for assessing Motion Sickness Index for an irregular vertical motion on a ship is to treat the irregular oscillation as if it was the same as a sinusoidal motion having the same RMS acceleration and a frequency corresponding to the average period of the acceleration peaks of the irregular motion, or more commonly the average period of the displacement peaks is used. This is fairly well described in the following text book:

  • Lloyd, A.R.J.M., “Seakeeping – Ship Behaviour in Rough Weather”, Ellis Horwood Series in Marine Technology, Ellis Horwood Ltd, 1989.

That book appears to have an error in the equation for calculating MSI but that may have been corrected in the more recent and revised issue of this excellent reference book on the subject. — Martin Grimm (seaflite@alphalink.com.au)

Drag Reduction via Magnetic Fields?

[16 Mar 01] Concerning the practical application of using elecro-magnetics in drag reduction… How can I try this out on a home built catamaran? It seems to me that the amount of drag reduction could be extreme, and the speed increase would also be equally radical. I am in the most early stages of planning to build a multi-hull yacht and I want extreme speed with extreme luxury (don’t we all?). Electromagnetic hull drag reduction might allow enough of an increase in speed to make hydrofoils a real world option. In this case I see it as transitional. A help to obtain the required speed for a cruising cat to get to hydrofoil speeds. Even if 100% lift is not induced, increased lift is a form of anti-gravity and reduced wetted area, so speed is increased. Certainly, however if this will work with only permanent magnets to some degree then so much the better. I also have other drag reducing ideas for the hull as well but obviously electromagnetics should work with any shape. So how can I practically do this? Implant wires, magnets and whatnots into the gel coat? I’d really like to know. If you have anything for me I would appreciate it and who knows maybe I will be able to make use of it. — Steve Van Brown (lordvalraven@hotmail.com)

Responses…[23 Mar 01] What can you have read to lead you to think you could do this?! The concepts for electromagnetic turbulence control for drag reduction remain quite immature and still lacking any definitive demonstrations of success at meaningful Reynolds numbers. I wouldn’t encourage you to continue his thinking in this direction. Let me know if you have any questions about where things stand. — Stan Siegel (Stansiegel@aol.com)

[23 Mar 01] Electromagnetics for drag reduction falls into the same category as magneto-hydrodynamic propulsion; that is, fun but no payoff. A Japanese gambling magnate spent about $20M to produce a great looking ship that went—you ready?—5 knots. The U.S. Navy topped this by giving Textron $25M to reduce drag and make a propulsor for subs. Result: 00000000. If you want to reduce drag for about 100x the potential payoff, put the power into a two-phase (non -Newtonian) flow system like Prairie Masker. That system introduced air bubbles at the bow to ventilate the surface. It may not work well with hydrofoils but it would make an interesting experiment and a real contribution if you could pull it off. — Nat Kobitz (KobitzN@ctc.com)

[23 Mar 01] I am very much interested in this subject also. If you haven’t logged onto the German website (http://www.fz-rossendorf.de/FWS/FWSH/EBLC/separation-control/), you should because it has some interesting info. — John Meyer (jmeyer@erols.com)

Side Force Over-Predicted Due to Ventilation…

[2 Mar 01] Surface piercing struts at a slight angle to the flow (e.g. in a steady turn) experience a side force that is over-predicted by normal hydrofoil theory. This is due to the suction side being ventilated to atmospheric pressure. Ventilation could extend all the way to the foil. Do you know of any literature concerning this subject, and how one predicts the side forces accurately? — Günther Migeotte (gunther@cae.co.za)

Responses…[5 Mar 01]The Hydronautics handbook that I sent you has a chapter on ventilation. The gist of the chapter is that there are 4 necessary conditions for ventilation to occur: 1) the local pressure must be less than atmospheric, 2) there must be a path for air to be conducted to the low pressure area, 3) there must be separated flow, and 4) the cavity formed must be stable. The key condition is #3, separation. If you have fully attached flow, any air introduced will simply stream off in a row of bubbles and not ventilate the flow. So the key would seem to be to design so as to maintain a margin against separation, either due to boundary layer separation or cavitation, and then analyze the strut in the conventional way. This being the case, one would be advised to avoid sharp-edged sections that will promote leading edge separation bubbles. It’s interesting to note that successful hydrofoil sailboats, such as the RAVE, have struts that are constantly loaded sideways and use conventional section shapes. — Tom Speer (tspeer@tspeer.com); website: www.tspeer.com; fax: +1 206 878 5269

[5 Mar 01] If a hydrofoil does not have any wings that pierce the surface, only struts, it will be unstable in roll so it will usually be banked into any turn, so there will be no steady side forces on a strut. However the side forces depend on the control philosophy of the roll control system. It is possible to corner a hydrofoil unbanked, but the cornering will be limited by the roll control flap limit. Also the angle the boat takes up when it is loaded off-centre depends on the control system. The obvious philosophies are to keep the boat flat or to centralise the average flap position. If the boat is kept level, there will be no side force on the struts, but if the flap position is centralised the boat will lean to keep the center of gravity above the center of the wing. If the main foil is tilted, the lift it produces is not vertical, so the sideways force is: w * tan(theta), where w is the boat weight and theta is the angle of tilt. Side wind forces have to be taken on the strut. I haven’t got a clue how to calculate it. When the flow over the strut is calculated, the angle of attack will have to be adjusted until the lift (sideways) equals the sideways forces. The flow over a strut causes areas of increase and reduced pressure. I haven’t done the calculations, but I think that the angles of attack will be so small, less than 2°, that the changes in pressure increase or decrease will be minimal. It is the pressure decreases that encourage ventilation, and if it is a problem, the struts thickness will have to be reduced. In which case, the strut will have to be longer in chord to be strong enough, so the angle of attack will be smaller, also reducing the ventilation problems caused by turning. From my experience on a Trampofoil, the main wing would ventilate quite badly if it hit the surface. I even videoed this happening from underwater in a swimming pool. However, the struts would not ventilate under any conditions. This included when the Trampofoil was ridden with the main wing at about 10° to the horizontal, and when it was steered violently, there was no problem with the front strut (which was the rudder) ventilating. I don’t think that you need to worry about ventilation caused by side forces. Ventilation may be a problem, but side forces will not add to it significantly. The structural effects of side forces need to be considered. — Malin Dixon (gallery@foils.org) Holly Cottage, 9 Barton Road; Carlton, Nuneaton CV13 0DB England; phone: +44 1455 292763; Mobile +44 7798 645574; Work +44 24 7664 2024; Fax +44 24 7664 2073

[6 Mar 01] Put a fence around the strut about 1 foot below the flight waterline, and another about a foot below that. The first one should be about 6 inches high, the second about 4. This should handle the problem of increased side force due to ventilation. Incidentally, it also works for struts for fully submerged foils. — Nat Kobitz (KobitzN@ctc.com)

Cavitation Bucket Diagrams

[2 Mar 01] We are French students working on foils and the problem of cavitation. In the FAQ of your web site, we have read a message of Mr Martin Grimm who speaks about cavitation bucket diagrams. We would like to find an example of these diagrams to illustrate a tutorial project. Could you help us by sending us a diagram or any valuable information? — Mathilde Pascal (Mathilde.Pascal@etu.enseeiht.fr) and Ludovic Léglise (hya54@etu.enseeiht.fr)


[2 Mar 01] I’ve attached an excerpt from the paper I just gave to the Chesapeake Sailing Yacht Symposium. It shows such a diagram and discusses its relevance to the hydrofoil design. I’ve also included an enlarged version of the diagram. I’ve chosen a somewhat idiosyncratic way of plotting this diagram. The X axis is often angle of attack, but I’ve chosen to use lift coefficient because different sections have different zero-lift angles of attack and lift coefficient is what really counts to the designer. But the biggest difference is that I have plotted velocity ratio on the Y axis instead of pressure coefficient or cavitation number. I did this because pressure coefficient is proportional to velocity squared, so it emphasizes areas of high velocity which are not of real interest. By plotting vs. velocity ratio I have expanded the bottom of the chart which is where the section will be operating when cavitation is a concern. The other thing you will find on this chart that I’ve never seen on any other diagram is an overlay of freestream velocities and foil loading corresponding to incipient cavitation. I found this really helped me to understand the section curves in the context of the boat’s design. I haven’t actually plotted it out yet, but I suspect that had I used pressure coefficient for the Y axis, the lines of constant foil loading would have been straight lines. Finally, my apologies for using English units. I’ll leave conversion to metric as an exercise for you students! — Tom Speer (tspeer@tspeer.com) website: www.tspeer.com; fax: +1 206 878 5269

Tom Speer's version of a Cavitation Bucket Diagram

Click on Image For Larger Version

[6 Mar 01] Tom Speer has already given you a good reply following your request for examples of ‘cavitation bucket diagrams’. I will however provide you one more example which is presented in the more usual manner with section cavitation number on one axis and foil angle of attack on the other. The attached diagram has been adapted from one of the figures in a very well presented and comprehensive book on the subject of marine propellers, namely: Marine Propellers and Propulsion, by J.S. Carlton (Senior Principal Surveyor, Technical Investigation, Propulsion and Environmental Engineering Department, Lloyd’s Register) Butterworth-Heinemann Ltd, Linacre House, Jordan Hill, Oxford OX2 8DP First published 1994. ISBN 0 7506 1143 X.


There are no scales on the axes of the diagram as it is illustrative only. You can see from the shape of the curve where the ‘cavitation bucket’ term came from. Even though you may already be familiar with the terminology on the diagram, I will run though it for completeness:

A Cavitation Bucket Diagram The section cavitation number is defined as:

Sigma o = (po – pv)/(0.5 rho V2)


po = Free stream pressure in absolute terms, i.e. not relative to atmospheric pressure (SI units would be Pa).pv = Vapour pressure of the water in absolute terms (SI units of Pa).

rho = Water density (SI units would be kg/m3)

V = Free stream velocity, i.e. well upstream of the foil (SI units would be m/s)

(I have avoided using subscripts or the usual Greek symbols so that I can send you this message in plain text)

For a foil traveling say 1 metre below the water surface in salt water, po can be calculated as:

po = patm + rho.g.h


patm = Atmospheric pressure, say 101300 Pag = Acceleration due to gravity, say 9.81 m/s2

h = submergence of the foil (in metres if using SI units consistently)


po = 101300 + (1025 x 9.81 x 1.00) = 111355 Pa

In salt water you can take the vapour pressure to be say: pv = 17000 Pa to be on the conservative side. The vapour pressure of distilled fresh water can be as low as 1700 Pa.

You can see from the diagram that at high angles of attack, cavitation will occur on the top side of the hydrofoil (called the ‘back’ in propeller terminology). At low or negative angles of attack, the low pressure moves to the bottom of the hydrofoil (this being called the ‘face’ on propellers). If the water flow past the foil is fast enough and the foil is not deeply submerged, then cavitation can even occur when the foil is at the zero lift angle of attack. This form of cavitation is referred to as bubble cavitation because of its appearance. This cavitation occurs simply a result of the thickness of the foil which causes the water velocity to increase slightly as it passes the sides of the foil and in turn the local pressure of the water drops below the vapour pressure.

These days, there are techniques available to design foils which are fairly tolerant of variations in their angle of attack and so can avoid the onset of cavitation. Such foil sections have a fairly wide cavitation bucket (defined by the parameter “alpha d” on the figure), though the limit at which bubble cavitation occurs may then shift to higher cavitation numbers so the bucket is no longer as deep. — Martin Grimm (seaflite@alphalink.com.au)

Follow Up…

[10 Mar 01]We have built a model of a foil with a NACA 0015 profile. Where could we find the cavitation bucket diagram corresponding to this kind of foil? Mathilde Pascal (Mathilde.Pascal@etu.enseeiht.fr) and Ludovic Léglise (hya54@etu.enseeiht.fr)

Follow Up Response…

[11 Mar 01] Here is how you build a cavitation diagram:

Go to http://raphael.mit.edu/xfoil/ and download XFOIL. This is the most powerful airfoil section design tool available. Do not think of using anything else you can download from the Web -they are all inferior to this program.

Put in the coordinates for your foil.

Analyze the section for a number of angles of attack, covering the intended range of operation. Examine the pressure distributions for each angle of attack.

For each angle of attack, record the minimum pressure coefficient that occurs anywhere on the section. The cavitation number, sigma, is simply the negative of the minimum pressure coefficient, Cp. (sigmai = -Cpmin where sigmai is the cavitation number for incipient cavitation and Cpmin is the minimum pressure coefficient)

Plot the minimum pressure coefficient vs angle of attack or lift coefficient, according to which you prefer.

Repeat steps 2 through 5 for each section you wish to consider.

I recommend you plot sigmai vs CL for the following reasons. If you disregard the vapor pressure of water, which is small, the critical speed for incipient cavitation at the surface is approximately

Vcrit = 14/sqrt(sigmai) m/secsigmai = (14/Vcrit)2

Vcrit is the freestream velocity above which cavitation may occur. Note that this is a horizontal line when superimposed on a cavitation diagram. If you know the freestream velocity (boat speed) and you know the lift coefficient, then you know how much load each square meter of the foil is carrying:

L = CL * 1/2 * rho * V2 * S[L/S]crit = CL * 1/2 * rho * (Vcrit)2

[L/S]crit = CL * 1/2 * rho * 142/sigmai

sigmai = {1/2 * rho * 142 / [L/S]crit} * CL

Note that for any given foil loading (L/S), the quantity inside the braces {} is a constant so this is a diagonal line extending from the origin of a sigmai vs CL plot.

Finally, to put together the whole cavitation picture, do the following:

Lay out axes of sigmai vs CL

Plot horizontal lines corresponding to the critical cavitation boat speeds.

Plot diagonal lines corresponding to the foil loading for incipient cavitation. Note that this forms a grid which is independent of the choice of foil section.

Plot sigmai vs. CL for the hydrofoil section.

Now, not only do you have the cavitation diagram for the section, you can relate it to key design aspects of the boat as a whole. You can see immediately how heavily the foil can be loaded and how fast the boat can go before encountering cavitation. Since the grid is universal, it can be used to define the requirements for designing a hydrofoil section, which you can do with XFOIL as well.

There is an excellent paper on the cavitation of hydrofoils in the latest issue of the Society of Naval Architects and Marine Engineers’ Journal of Ship Research, written by researchers at the Institut de Recherche de l’Ecole Navale, 29240 Brest-Naval, France: J.-A Astolfi, J.-B. Leroux, P. Dorange, J.-Y Billard, F. Deniset, and S. de la Fuente, “An Experimental Investigation of Cavitation Inception and Development on a Two-Dimensional Hydrofoil,” Journal of Ship Research, Vol. 44, No. 4, Dec. 2000, pp. 259-269. It shows more cavitation diagrams and also the degree to which experimental cavitation occurs at Cpmin. The agreement is excellent at the bottom of the bucket and Cpmin is a conservative estimate for the sides of the bucket. They also discuss the interaction of cavitation and laminar flow, which will be important for your low Reynolds number experiments. — Tom Speer (tspeer@tspeer.com) website: www.tspeer.com; fax: +1 206 878 5269

Manual Control of Sailing Hydrofoils

[28 Feb 01] Has there been any recent input on manual foiler control (say, of the RAVE) or does anyone have any thoughts on the subject? — Doug Lord (lorsail@webtv.net)

Responses…[28 Feb 01] I have my doubts if manual ride level controls are useful at all, if you actually mean “real time” adjustment not preset positions:

As a dinghy sailor, you have enough to do with steering, sheeting, weight trim, sail adjustment etc., so almost no time for more to worry about.

Light, smallish craft do react very quickly on even the slightest foil adjustments, even larger units as high speed ferries use auto controls, either with mechanical or electronical input, self-driven with pushed or trailed surface level arms or combinations of servo power from electric-hydraulic-air or such.

I just wanted to express that for looong extended cruises full and only manual control could be exhaustive and boring. IF humans can act as quick or better than automatics, okay !

— Claus-C. Plaass – Pickert 10 – 24143 Kiel – Germany – email  (plaass@foni.net), ph +49-431-36 800

[4 Mar 01, updated 3 Nov 02] I designed several manual controlled foil stabilized outriggers. From the first one it was plain to see that manual controlled full foilers was the way to go to generate performance all around the course. Sailing is just too dynamic not to have manual controls. I invited Greg Ketterman to sail my boat proposing to change his tri-foil to manual control but he explained that for he was working on larger designs where this might not be possible. I think it is inevitable. Let me know if you are interested in more details as to how we controlled them. I have several designs and several published articles about these boats. Last article was in Multihulls March/April issue. A Yahoo search for John Slattebo will reveal two more. — John Slattebo (raptor16@sbcglobal.net) website: (http://hydrovisions.com/)

Reynolds Number Scaling Effects

[20 Feb 01] Do you know of any references or anybody who has investigated Reynolds number scaling effects of hydrofoils under the free surface. What I am primarily interested in the loss in lift of model foils due to their lower operating Reynolds numbers. So far the only info I have on the subject is Dr. Frans van Walree’s Ph.D. thesis. My own calculations show this loss of lift depends on the Reynolds number as well as the submergence of the hydrofoil and can be as high as 30%. — Günther Migeotte (gunther@cae.co.za); Dept. of Mechanical Engineering, University of Stellenbosch; Banghoek Rd; Stellenbosch,7600

Responses…[21 Feb 01] I’ve not been able to find any information on Reynolds number effects on hydrofoils, either. It’s not clear to me just what the mechanism would be for Reynolds number-dependent free surface effects on a fully submerged foil, except indirectly through modification of the pressure distribution and thereby the boundary layer. For surface piercing foils and struts, I could see how viscous effects would affect the spray drag etc. All the investigators I know have assumed that the foils would be operating at fairly hi Re and would be pretty much fully turbulent. For what it’s worth, I’ve designed some hydrofoil sections which should tolerate a much wider Reynolds number range, suitable for models operating down to 300,000 – 400,000. Possibly less with BL trip. Xfoil results are at http://www.nasg.com/afdb/show-airfoil-e.phtml?id=1187. I’d like to know more about what you’ve found and how you do your calculations. I don’t have any free-surface capability other than the infinite-Froude number linear approximation. Two big issues I wonder about are spray drag of struts and surface piercing hydrofoils producing lift, and prediction of ventilation. — Tom Speer (tspeer@tspeer.com) www.tspeer.com fax: +1 206 878 5269

[21 Feb 01] One good reference for these effects is the Ph.D. thesis of Dr. Frans van Walree at MARIN. If you check out the IHS website, somewhere you will find a link on how to obtain a copy of his thesis. He found that there is a viscous reduction in lift curve slope for all Reynolds numbers, but for Rn>1e6 the effect is small. If one is using thin wing theory, the extra lift caused by the thickness of the foil is cancelled by the viscous effect giving a lift curve slope close to 2pi. As the Reynolds number gets lower one is forced to introduce viscous corrections and account for the thickness of the foil. I have followed a similar line to van Walree in trying to calculate viscous effects. I have compared experimental results for hydrofoils with numerical results of the vortex lattice method of AUTOWING ( http://www.cl.spb.ru/taranov/Index.htm ). Autowing has been well validated for hydrofoils. Comparing the exp. and calc. lift curve slope, I found that for the 3D hydrofoils I examined, the viscous effect on lift disappears as the foil approaches the free surface. For h/c<0.25 it is practically negligible. After thinking about this, I think it makes good sense. Viscosity affects mainly the suction side of a foil, as it has adverse pressure gradients. Using Xfoil one can clearly see that the boundary layer reduces the suction pressure (compared with potential flow) and hardly affects the pressure side as it has favorable pressure gradients. I have not heard of anybody else mention this. Close to the free surface the suction side of the foil contributes very little lift, so the effect of the boundary layer is small. Xfoil predicts the viscous loss in lift quite well if Rn>5e5 with leading edge turbulence stimulation for deep submergences. For free transition, Xfoil under predicts the viscous loss in lift. If you come up with any other info please let me know. What is needed now is a version of Xfoil with a free surface model to investigate this further…. — Günther Migeotte (gunther@cae.co.za)

[21 Feb 01] I can suggest one fairly old reference on model testing of hydrofoils compiled for the International Towing Tank Conference (ITTC) which may be of help: DTNSRDC-81/26 (or 81/026 ??) ‘Status of Hydrodynamic Technology as Related to Model Tests of High-Speed Marine Vehicles’, July 1981. Unclassified, Approved for Public Release, Distribution Unlimited. David W. Taylor Naval Ship Research and Development Center. Author of Hydrofoil section: B. Müller-Graf (who is still an IHS member) Abstract reads: The High Speed Marine Vehicle Panel of the 16th International Towing Tank Conference prepared hydrodynamic technology status reports related to model tank tests of SWATH, semidisplacement round bilge hulls, planing hulls, semisubmerged hydrofoils, surface effect ships, and air cushion vehicles. Each status report, plus the results of an initial survey of worldwide towing tanks conducting model experiments of high speed vessels, are contained herein. Hydrodynamic problems related to model testing and the full-scale extrapolation of the data for these vehicle types are also presented. — Martin Grimm (seaflite@alphalink.com.au)

Section and Materials For Supercavitation Foils

[23 Nov 00] This concerns foils for a 22ft racing catamaran powerboat a friend of mine is currently constructing. The HYSUCAT concept consists of a main foil supported on the lowest point of the hull and spans horizontally across the tunnel between the two hulls just in front of the center of gravity. There are also two smaller aft foils close to the stern that does not span the whole distance across the tunnel. On this particular boat the chord length is 160 mm and the span approximately 950mm. As this boat is powered by two 150Hp outboards, the maximum speed would be around 70 Mph. The main purpose of the fwd foil is to reduce the slamming of the hulls and also to bring it onto a plane much quicker. The foil section currently used on a slower boat is an arc of circle foil manufactured from stainless steel. This foil section was probably used for ease of manufacturing. I have recently manufactured a couple of carbon/kevlar foils for my Trampofoil with great success and would thus like to manufacture another foil for the racing boat using a more optimum foil section and composite materials. The section I have picked was the E817 but I am wary that this foil section might cavitate at these high speeds. My knowledge on super cavitating foils is very limited but I have seen some sections with the sharp entry and flat rear end witch looks promising. What section would you propose to use in such an application and where can I get hold of some data and information regarding these high speed foils? What would the implications be in using a composite material and corrosion due to cavitation? — Ben Lochner, Cape Town, South Africa (benl@kingsley.co.za)

More on Retractable T-Foils

[20 Oct 00] In the current (Autumn 2000) newsletter, there’s an article about MDI’s retractable T-foil for Incat, with most of the historical information coming from Fast Ferry International, and some information from John Adams here at MDI. I would like to add a few statements on a more personal plane. The original 74m wave piercer ride control system was basically as stated in the newsletter (as an excerpt from Fast Ferry International) except- the first 4 square meter pivoting T-foils with flaps (1 per hull) were designed at that time as well. (not the center mounted retractable) I know because I did the 3D CAD integration of the concept, and came up with some interesting features of the 4 sq M foil actuation mechanisms myself. Most of these features are still in use today, some were a learning curve. The previous pioneering ROCS for a non-SES vessel was a smaller foil stabilized catamaran CONSOR 9, which had hull mounted fins. The T-Foil idea was originally pushed very hard by a ‘staunch’ engineer (who would NOT let go of it…) from the UK- Lionel Frampton of Marine and General Engineering, Ltd. UK. Without Lionel’s persistence, the foils may have taken a much different tack indeed, and I feel he should receive some acknowledgement for the prevalence of the T-foil today. I also worked on the Corsaire 11000, 12000, and 13000 designs, actually building 2 model scale T-foils and integrating them in the tank model at DTRC, in what I believe was the first tank testing of an active ride control system of this type. It was, in fact, the 1/14th scale model referenced in the article (paper given by Christian Gaudin of ALN and Raymond Dussert-Vidalet of SNCM at the 16th Fast Ferry International conference). I also designed the integration of the trim tabs and roll fins for these model tests. The model T-foils are still being used for various tests. It was pretty exciting to see them in the IHS newsletter! — Rick Loheed (rloheed@islandengineering.com)

Reynold’s Number Calculation

[7 Oct 00] I would really appreciate answers to two quick questions: 1)How can I calculate the Reynold’s Number of a hydrofoil? 2)Are there any good sources of hydrofoil coordinates or data on the internet? — David Shelton (DBshelton2@aol.com)

Responses…[7 Oct 00] The Reynolds Number (Rn) = vL/(nu). Where: v = velocity, L = length, nu = kinematic velocity. It is important that the units be consistent. For example, v in feet/sec, L in feet, nu in sq feet/sec. L is a characteristic length, typically the foil’s chord. Nu varies with temperature and fluid (in fresh water at 59F nu is 1.22603 X 10-5). The Reynolds Number for each foil and strut must be calculated separately. — King James H CRBE (KingJH@nswccd.navy.mil)

[7 Oct 00, updated 17 Feb 03] There is an airfoil database at http://www.nasg.com/afdb/index-e.phtml. There is a freeware NACA foil generator program available at http://ourworld.compuserve.com/homepages/Harold_Ginsberg/boatship.htm. Also, see the links page on the IHS site for additional sources of design info. — Barney C. Black (Please reply via the BBS)

[9 Oct 00] The Reynolds Number is the non-dimensional ratio of the inertial forces to the viscous forces pertinent to a body moving in a fluid. It is given by the following equation; R= velocity times a length parameter divided by the kinematic viscosity of the fluid. You can see that it doesn’t make any sense to ask– what is the Reynolds Number of a hydrofoil?– without specifying what Reynolds Number, e.g.., a foil, a strut, the hull, etc. If you mean a foil, the length parameter is generally the chord. If it’s the hull, the length parameter is generally the length of the hull. The larger the Reynolds Number, the less important are the viscous forces, conversely, the smaller the Reynolds Number, the more important are the viscous forces. A Reynolds Number approaching zero corresponds to flow in which inertial effects are negligible by comparison to viscous effects such as a steel ball dropping in a tube of honey. In the case of “hydrofoils,” the question is — for what length parameter and for what flow velocity? After all this explanation, the bottom line is that I don’t believe that the Reynolds Number is of particular concern for “hydrofoils.” What is important is the Froude Number, which is the ratio of inertial forces to gravity forces, the inception of cavitation on the foils, and foil or strut ventilation. — Bill Ellsworth

[9 Oct 00] Reynolds Number is defined as: Rn = V * L / NU Where: V = Velocity (of the hydrofoil) through the water in metres per second (m/s); L = A reference length in metres (m). In the case of hydrofoils the chord length is used as the reference length to calculate Reynolds Number. NU = Kinematic Viscosity of the water in metres squared per second (m2/s). Any other consistent set of units can be used, as Reynolds number is a dimensionless quantity. For fresh water at 15 degrees Celsius: NU = 1.13902*10-6 m2/s. For salt water with salinity of 3.5% at 15 degrees Celsius: NU = 1.18831*10-6 m2/s. For any reasonable range of water temperatures, the Kinematic Viscosity can be calculated approximately with the following equations (giving results in units of m2/s again): For fresh water: NU = (6.8309*10-4*TEMP2 – 5.227728*10-2*TEMP + 1.76836591)*10-6. For salt water with salinity of 3.5%: NU = (6.6375*10-4*TEMP2 – 5.145326*10-2*TEMP + 1.80950523)*10-6 Where: TEMP = Water temperature in degrees Celsius.

Which Foil Section is Best

[29 Aug 00] I wish to construct a few recreational dynamically supported pleasure craft. I have been conversing with Mr. Larsen (an IHS member) and Mr. Mateev (Cal Tech and IHS Member). They have been most helpful in helping me to assess the basic design constraints required. Based on their correspondence, I would first like to pursue the construction of a hydraulically retractable surface piercing (shallow draft) hydrofoil. The prototype craft is to be in the 20 foot (6 meter) range with a displacement of 2500 to 3000 lbs. (1150 kilograms to 1350 kilograms). I believe this to be the standard displacement for this size of craft. Target speed to be 50 knots. Power to come from an I/O arrangement with a standard V-8 gasoline motor generating approximately 300 hp (223.8 kW). Engine may be further modified to increase output. Leg to be a modified unit with a “Vari-Prop” pitch adjustable prop. Ride height is as of yet undetermined. I have not purchased the boat yet. I am hoping to construct a two piece interlocking foil arrangement that could hydraulically split for the purpose of retraction. Time line is (10) months to construction. Among these design criterion is foil selection. I was referred to you by Professor Kinnas (University of Texas at Austin, Department of Civil Engineering, Ocean Engineering Studies). I presently have little knowledge of the physics involved in foil selection. Any assistance would be gratefully accepted. — Wayne Gillespie (wayneg99@telus.net)

Response…[29 Aug 00] Regarding hydrofoil sections, I like the NACA 16-series hydrofoils because they provide good cavitation resistance, which you will need at 50 knots. As design speed increases, the hydrofoil thickness/chord ratio and lift coefficient must reduce to prevent cavitation. I used a NACA 16-510 hydrofoil section for surface piercing hydrofoils developed in the 1950’s, which had a max speed of 46 mph with the 65 hp outboard I was using at the time. You might want to read my article on hydrofoil boats in the pioneer section of the International Hydrofoil Society Web Pages. An excellent source for other hydrofoil cross sections is in the book “Airfoil Design and Data” by Richard Eppler, published by Springer-Verlag, 1990. — Tom Lang (tglang@adelphia.net)

Follow Up…

[8 Sep 00] Thank you very much for the input. I suppose that I will have to find a supplier / method of production for the foil(s). How are the actual; dimensions obtained? Are there on line resources available to this end? Distance between supports will have to be determined as well. I have visited the University of Texas at Austin pages and found an interactive applet design page that models relative lift and drag ratios of given foil dimensions. Most interesting. I however presently lack the understanding of the data to interpolate. Do you know the approximate cost of dies for aluminium extrusion? Are there any points of interest in the production end of foil extrusion that you have learned through your experience? I will endeavour to obtain the referenced book. You mentioned that a 1.5 deg twist in the foil of your kit allowed the craft to lean into the turn by allowing the inner foil (on the turn) to ventilate first. Can you elaborate on the process involved that cause this to happen? Conversely, it there is information within existing reference texts, I would be most grateful if you might simply direct me in the appropriate direction. — Wayne Gillespie (wayneg99@telus.net)


[8 Sep 00] You might want to consider making composite hydrofoils; however, extrusions are easier to work with. The foil cross sectional dimensions are available from the Eppler book, or in the case of NACA sections from the Dover book by Abbott et al, “Theory of Wing Sections”. The Marks Handbook on Mechanical Engineering is one of many references on beams and structural strength. You might re-contact IHS to see if he has a list of references on hydrofoil design, and if they know of any sources of extrusions. Also, you could contact Alcoa for their list of existing dies and the cost of new dies. I think that there are many hydrofoil enthusiasts who would like to buy extrusions. You might ask IHS about references concerning ventilation. Also, it would be helpful to join the IHS; the special student cost is very low. My experience showed that ventilation occurred when angle of attack increased around two-to-three degrees above the design angle at a 30 deg dihedral, more with a higher dihedral, and less with a lower dihedral. Much depends on the accuracy of the hydrofoil nose region. Ventilation occurs when the hydrofoil boundary layer separates near the nose on the upper side, and air fills the separated region, generally superventilating the entire foil section downward for several inches; the result is the sudden loss of all lift in the supervented region. Sharp nose sections ventilate sooner than airfoil noses. Fences can be used to stop ventilation at intervals, but add some drag. — Tom Lang (tglang@adelphia.net)

Sailing Hydrofoil Design Data

[19 Feb 00] FYI, Here’s a new link for your “Websites of IHS Members” section. I’ve put up some information on hydrofoil sections that might be of interest. — Tom Speer (tspeer@tspeer.com)


[5 Jan 00] I am about to start my hydrofoil setup for my solo sailing 18 Square, but I have some questions about certain aspects of design. The main question is what are fences on hydrofoils for? What do they do and how should the be arranged on a foil shape? I want to make foils like those from ICARUS and I know they used fences. Are they a way to keep water down? Visual marker for the skipper? Another question is what is the chord size for ICARUS ? It looks like 4″-5″ because it is larger than the crossbeam on a Tornado beach catamaran. What size do you think would suit a 360 pound catamaran sailing at or above 25 knots with 200-400 pounds of crew weight? This assumes I do use the ICARUS foil setup. I may use the ICARUS II setup and use a smaller chord, this is pretty much just a doubled up bottom lifter foil. This setup was used when they had the double rig. I noticed you didn’t have any photos of this great boat either, I have found two of them on this page: http://home.worldonline.nl/~hbsmits/hydrofoi.htm — Michael Coleman (MECcoleman@aol.com) — Mike’s NACRA PageMike’s 18 Square Page

Response…[5 Jan 00] Fences reduce spanwise flow. Since the pressure under the foil is greater than that on top, the water wants up any way it can. Going around the tip reduces the lift ;therefore, fences or tiplets or tiprings. If you are making an exact copy of ICARUS foils use the same fences. If not, the best is to do some simple tank tests (try the Naval Academy). If you want to risk a little loss in efficiency scale the ICARUS foils and fences. ALSO, do not change the aspect ratio of the foils without testing. Reducing it will change flight characteristics. Increasing it will change structural loads. SUPPLEMENT: Strut fences are good for reducing downflow on the strut, both water, which reduces lift and air, which ventilates the foil and screws everything up. GOOD LUCK!!! — Nat Kobitz (kobitzn@ctc.com)

2nd Response…

[5 Jan 00] I do not know of any hydrofoil ship with fences on the foil itself. Fences were put on the struts to interrupt ventilation. Ventilation is when the air flows from the water surface creating a cavity between the strut surface and the water. Due to the difference in density of air and water, ventilation could cause loss of lift and/or control. The fences are essentially flat plates attached to the strut perpendicular to the strut surface and in line with the water flow. Generally they were contoured in simular shape as the strut. A good example is the cavitation plate on an outboard motor or the I/O drive. Fences were not used on any of the Navy hydrofoils. As far as the remainder of your questions, I plead ignorance. — Sumi Arima (arimas1@juno.com)

3rd Response…

[4 Jun 00] The following is quoted from the 1967 book Hydrofoils by Christopher Hook and A. C. Kermode: “One serious problem with both these systems [ladder foils and V-foils] is air entry, for by the very nature of the design, some parts of the foil, or some of the foils, are always at or near the surface; they are in fact surface-piercing foils. This means that it is all too easy for air to get in and spoil the lift. The danger of air entry can be reduced to some extent by fitting fences, baffle plates, or screens on top of the foils; as their names imply, they act as barriers to the air, and may temporarily prevent it from getting further down the foil, but like most fences they can be jumped, and as one fence emerges, the air jumps to the next fence down.”

Experimenter Needs Advice on Foil Sections

[7 Feb 99] As a new IHS’er, I recently purchased Dave Keiper’s notes and 3″ foil & strut stock. After reading his notes, however, I feel I need to get started in this fascinating world of hydrofoils at a little more basic level, and tackle my 1982 Nacra 5.2 hydrofoil project a little later… after I successfully build a more basic hydrofoil project (I’m a marketing type, not an engineer)! I wish to construct a stable towed hydrofoil platform, utilizing 4 ea. 6″ surface piercing foils in a split-tandem configuration. I’m guessing that each foil would be angled out 55 deg. from the vertical strut. I would like to carry a loaded vessel weight of 800-900 lbs., at speeds up to est. 45 mph. What foil section would be best suited for this application, and who can I purchase 6″ foil and strut stock from? I recall reading that Alcoa offered foils, but don’t know what to ask for ! Do you have any suppliers you could recommend that make such foil stock? Any suggestions / recommendations for this towed contraption? — Brian Ballou

Response…[8 Feb 99] Recently I attended the Düsseldorf Boat show – known as the World’s largest. I remember having seen symmetrical foils of a very high surface quality, weldable and with two internal struts for stiffening. Chord length was about 6-8″, thickness was about 1 inch, wall thickness was some 1/6 inch. Comes in lengths of 6 m (20′) If this is of any interest to you, please let me know with details, such as required section, total length and max length for shipping. I already discussed the matter with the manufacturer, so sending you an offer shouldn’t take very long. My offer for the 3″ chord length NACA 16-008 and Clark-y remain valid. — Claus-Chris Plaass (plaass@foni.net) phone: +49-431-36 800

[11 Nov 01] Foil Stock, carbon fiber NACA 63-412, 120mm chord: http://imca-wa.freeyellow.com/Resources.html. — Tom Speer (me@tspeer.com) website: www.tspeer.com

The Right Section?

[updated 18 Aug 98] I need to find the proper foil section to use for a strut section . . . my experience is all with Aerodynamics, not Hydrodynamics, so am out of my comfort zone (Reynolds number wise). Issues: (1) Maintenance of fully attached flow throughout range of 10-60 MPH; (2) Essentially zero degrees angle of attack (strut); (3) Very small chord (in the range of 1/4 to 1/2 inch) — Scott Kelley (scottk@iccom.com)


[7 Oct 98] Sorry it has taken so long to get back to you, but I had to get hold of Abbott and Von Doenhoff’s book on “Theory of Wing Sections”. I recommend a very simple section; namely NACA 0012. A thicker section would normally lead to cavitation at a given high speed, so it is a tradeoff between cavitation and structural adequacy. As in most things it’s a compromise! — John Meyer, President IHS (president@foils.org)


[18 Aug 98] I believe the question of what section to use involves more issues than Scott Kelley is aware of. In any event I can recommend that he contact David Taylor Research Center (now Naval Surface Warfare Center – Carderock Division) to obtain a copy of the following report: Rothblum, R. S., D. A. Meyer and G. M. Wilburn, “Ventilation, Cavitation and Other Characteristics of High Speed Surface-Piercing Struts”, Report NSRDC 3023, July 1969. This is the most comprehensive test report on strut hydrodynamics which I encountered in my previous work on hydrofoil loads criteria. I must say the strut dimensions which he cites seem bit unusual. For a chord of 0.25 in. and a representative 10% thickness this would result in a maximum thickness of 0.025 in. — Bill Buckley (wbuckley@erols.com)


[18 Aug 98] The old Hydrofoil Design Data Log (DDL) had foil section shapes for all of the Navy’s hydrofoils. It should be in the Advanced Ship Data Bank at CDNSWC, and I don’t think that kind of data is classified. — Mark Bebar (Bebar_Mark@hq.navsea.navy.mil)


[18 Aug 98] The main considerations for using a small chord (~1/2 inch) strut at high speed (60 knots) are endurance and providing smooth flow around it. These tasks are opposite in some sense. The thicker the strut, the more durable it is, but it gives results in diminishing the speed at which cavitation begins. I think it is necessary first to calculate the thickness at which endurance will be guaranteed, then choose the profile for the smoothest flow.

Endurance. In your design, you should consider the strut as a rafter with one attached end or both attached ends or as a frame with certain shape. The maximum value of forces acting on the strut must be taken when calculating the bending moments. The calculation is made by standard methods of elasticity theory or some empirical expressions. The thickness of strut paneling is determined from condition of providing the endurance at the maximum bending moment. The maximum contracting stress cannot be more than Eulerian stress with endurance reserve 2.5. (The thickness of the strut cannot be less than the thickness of strut paneling.) If flow is non stationary (for example wave impacts take place), then it is necessary to check the dynamical endurance of the strut by means of experiment or complicated calculations.

Choice of the Profile. If the smoothest flow is needed, you can try a profile with circled bow edge and sharp stern edge something like NACA-0009 (it is sometimes used as a rudder), it must work until high speed without cavitation. You can estimate the speed at cavitation will start using expressions given on my web page. But usually in hydrofoil systems other strut profiles are applied. The bow edge is circled or sharp, the stern edge is obtuse (like a wedge). It enables to diminish the resistance at some speed range (so-called effect of resistance crisis), in spite of flow estrangement.

— Konstantin Matveev (matveev@cco.caltech.edu) website: International Hydrofoil Society Presents…

Hydrofoil History – Pioneering Vessels and Pioneering People
Articles, Awards, Correspondence(Last Updated February 28, 2016)

[Pages From History (Articles)] [IHS Award Citations] [Information & Photos Needed] [Correspondence] [ Death Notices, Obituaries, and In Memoriam]


  1. The Premier Source For Descriptions and Principal Characteristics of Specific Military and Commercial Hydrofoils is (are) the back issues of Jane’s Surface Skimmers, Hovercraft, and Hydrofoils — check your library or used book store!
  2. IHS needs additional articles on hydrofoil history for the newsletter and for this page. See below for subjects on which we need information and photos. To suggest additions to the list, contact the webmaster.

Go to Posted Messages Bulletin Board

Pages From the History of Hydrofoils

The International Hydrofoil Society (IHS) presents pages from the history of hydrofoils… selected articles and photos from the IHS newsletter and other sources, written by and about people who were there (and in many cases are still here). Enjoy!

IHS Award Citations

One of the more pleasurable functions of the International Hydrofoil Society is to recognize hydrofoil pioneers for substantial contributions to the field. The IHS Award Citation consists of an engraved plaque and a text summary of the recipient’s contributions. Following are some of the Award Citations given to date.

Information and Photos Needed

Following is a partial list of historical topics that could make good additions to this page. Contact the webmaster if you would like to provide info/photos or to write a new “Page From the History of Hydrofoils” on one of these subjects or any other historical subject of interest to hydrofoilers. Please feel free to suggest topics that should be added to this list.

  1. According to the Smithsonian Air and Space Museum website, PBM-5A Martin Mariner aircraft were used in ski/hydrofoil development tests for seaplanes conducted by Convair in the late 1950s. Also according to the website, the Convair XF2Y-1 (F-7) Sea Dart was used to experiment with a small rigidly-mounted hydrofoil ski. Actual flight was not possible with this configuration because the rigid mounting and placement of the ski “…would not permit the approx. 20 degree nose-up attitude required for takeoff. The first test was carried out on 21 Mar 57. Violent pounding caused every taxiing run to be aborted at speeds between 50 and 60 knots. Another rigid ski configuration was tested in the autumn of 1957. It too cause too much vibration, and further tests were abandoned.”
  2. “The bath tub [hydrofoil] models were made in 1938. That was just about a year after I had married. In 1941, we decided to make it a hydrofoil sail boat, and made our first successful run under sail on the Chesapeake Bay in 1941. Then we took it apart and put it back up in the garage afterwards and didn’t sail it again, and it was later turned over to Vannevar Bush. He got a very important idea, that he thought the hydrofoils were going to be so effective in all kinds of shipping. He formed a company and he said if I’d patent my original sail hydrofoil, those plans would be worth a great deal, and he’d give me a generous amount of stock in his company… He really was excited and he’d been wondering how he was going to get patent coverage on the hydrofoil. Here was something ideal, I could patent my sailboat. The problem he (Bush) had, he had a fellow named Shearer, I think his name was Shearer, and he did most of the calculations for Vannevar Bush. The NACA had put out books that summarized airfoils characteristics. They gave the profile drag of a great number of airfoils. These were low drag airfoils capable of laminar flow and they had very, very low drag. So Shearer was taking the values of drag, and then just saying that the lift to drag ratio was to take a reasonable lift coefficient and divide the drag into that. He was getting lift to drag ratios that were around 30 and 40 and 50, and he didn’t realize that there was another drag that was called induced drag, which was the drag due to lift. You just don’t put it in the handbook because it is dependent on the aspect ratio and the speed. Anyway, that was the thing that was wrong with the Hydrofoil Corporation. They calculated the drag wrong and they thought they could get drags that were very, very much lower than they could get. When they built some of their first models, they found that the drag was much higher than they’d thought.” — Dr. Robert Gilruth in a 14 May 86 interview conducted by Dr. David De Vorkin, Ms. Linda Exwell, and Mr. Martin Collins.
  3. The hydrofoil development work by Sam Saunders and the Saunders Roe company in support of the Canadian naval hydrofoil program led to the construction in 1956/57 of the 59 foot long hydrofoil vessel R-103 BRAS D’OR, which was equipped with ladder foils. The BRAS D’OR was subsequently re-named BADDECK in 1962 in anticipation of the construction of the proposed larger FHE-400 which was to be given the name BRAS D’OR.
  4. According to Ian Hamilton in his article “The Hydrofoil As a Weapon,” which appeared in Pacific Defence Reporter Aug 1981, “The first hydrofoil boat was the product of an accident in 1861, when Thomas Moy, an Englishman, decided to study the aerodynamics of wings by observing the underwater swirls they created. Having attached wings to his craft, he ventured out onto the Surrey Canal. To his surprise, the ship rose from the water — and unintentionally he had invented hydrofoils. But it was not until 1898 that the first efficient hydrofoil was designed by Enrico Forlanini of Milan…”
  5. More items needed… please suggest additional topics by contacting the webmaster.


[ALBATROSS] [Aquavit/Aquavion] [FHE-400 BRAS D’OR][R-100 MASSAWIPPI][R-103 BADDECK][HIGH POINT] [FLAGSTAFF] [FLYING CLOUD] [Hitler’s Hydrofoils] [MONITOR] [PHMs] [PLAINVIEW] [TUCUMCARI] [LITTLE SQUIRT] [Display Models] [R/C Models] [WHITE HAWK] [HS VICTORIA] [Hydrofoil Seaplanes]

Found a “Lost Member”

[19 Jan 02] It is interesting to see activity in IHS these days. I was once a member 20-25 years ago in the UK and knew/know Mark Thornton and Bob McGregor. — Neil Bose, Ph.D., P. Eng., Professor — Chair, Ocean and Naval Architectural Engineering, Faculty of Engineering and Applied Science, Memorial University, St. John’s, NF, A1B 3X5, Canada; Tel.: +709-737-4058; Fax: +709-737-2116 (nbose@engr.mun.ca); www.engr.mun.ca/Naval ; www.engr.mun.ca/~nbose


[19 Jan 02] It was good to hear from a “lost” IHS member. If you want to catch up on what has happened at IHS, an excellent history of the organization was prepared for our 25th Anniversary Conference by Bob Johnston… That will bring you up to 1995. It can be found on the web at: //archive.foils.org/ihs25his.pdf. As you were an early member in England, you may be able to fill in some of the gaps or add information to what is published in that paper. Much of IHS’s development subsequent to 1995 are reflected in the extensive IHS website. — Barney C. Black (Please reply via the BBS)


[23 Jan 02] An interesting historical footnote: the following text and photo appeared on eBay. “Ticket for Hydrofoil Service, a failed attempt to introduce “high speed” marine transportation between Falmouth and Martha’s Vineyard in 1966. The vessel was named FLYING CLOUD and operated on a trial basis, including a demonstration run to Nantucket. The combination of her unsuitability to Nantucket Sound, mechanical problems, and lack of public interest ended her short career in the Cape and Islands area. The ticket is pink, measures 4×3 inches… Front reads: ‘Hydrofoil Service. Good for one passage in either direction between Falmouth and Martha’s Vineyard. Sold subject to Tariff Regulations. Form Hy-1 Issued by W.H., M.V. & Nan. SSA. No. 2068 James H. Smith Chairman.’ Back lists disclaimers of Woods Hole, Martha?s Vineyard and Nantucket Steamship Authority.” — Barney C. Black (Please reply via the BBS)

Polish Hydrofoil Design Point of Contact

[13 Jan 02] I am very interested to obtain your AMV CD-ROM. In the 1960-70s our Department was involved in some projects connected with hydrofoil vessels with surface piercing foils. Some of them you can find in an old Jane’s yearbook, for example: Jane’s Surface Skimmers: Hovercraft & Hydrofoils 1970-71. — Michal Krezelewski D.Sc(Eng) (krezel@pg.gda.pl) Our mailing address: Faculty of Ocean Engineering and Ship Technology; Department of Ship Hydromechanics; Technical University of Gdansk;  G. Narutowicza 11/12 str.; 80-952 Gdansk, Poland

Responses…[13 Jan 02] As you recommended, I looked into Jane’s and found the 76-seat ZRYW-1, completed in May 1965, the first Polish-designed passenger hydrofoil to go into service. It averaged more than 39 knots on scheduled services between Szczecin and Swinoujscie, a distance of 67km. Also, a design for the W-2 REKIN, a ferry for the Baltic. Other hydrofoil designs were smaller, personal watercraft, including the WS-4 AMOR, a 4-seat hydrofoil designed by E. Brzolska, and the W-6 EROS, a 6-seater. I don’t know if you have any archived photographs and information available, but if you do, I would like to include a page on our website dedicated to the Polish hydrofoil history. It would be a good subject for the newsletter also. There is some technical information and some photos in Jane’s, but we do not have permission to use this copyrighted material. — Barney C. Black (Please reply via the BBS)

[1 Jun 03] Mr. Krezelewski from Technical University in Gdansk is THE man connected with development of Polish hydrofoils in 1960s and thus he should know from first hand experience a good deal of their history.. I suggest you should try to get a lengthy article from him! — Marek Twardowski (marektwardowski@hotmail.com)


[22 Dec 01] I have been researching today’s US Navy Patrol Craft. Specifically the PC-1 CYCLONE Class. I feel that it is time to resurrect the old PGH-2 TUCUMCARI designs. When comparing the CYCLONE spec to the TUCUMCARI spec, I find that as a Special Warfare vessel, TUCUMCARI far exceeds CYCLONE in most respects. It appears that if the TUCUMCARI drawings and engineering data were available, the timing is right for some US shipyard to make an Unsolicited Proposal to the USN to build a prototype using all the modern bells and whistles. The basic TUCUMCARI was 100% successful. The vessel either met or exceeded the mission requirements of the Navy. I have always asked the question, “Why did the USCG and the USN have to go to Vosper Thornycroft, a British company for a high speed vessel design”? Do we not have capable engineers in the United States? — Ken Plyler (Kfppfk@aol.com)

[17 Dec 01] Just a tidbit that might be useful to you: The PHM actually had dual height sensors, radar and sonic. Both signals were interpolated by ACS simultaneously. I have experienced foilborne ops with sonic sensor only, and the ride was noticeably rougher, but effective. — Rob DeSendi, USS AQUILA PHM-4 (RDesendi@nsmayport.spear.navy.mil)

[26 Dec 01] I believe the radar and sonic height sensors were independent of each other. There was a switch on the bridge to select “radar” or “sonic” not both. The ride on the radar sensors was better in most sea states, but the sonic sensors were much more reliable–Chuck Shannon, ET1 MLSG (ChuckE68@aol.com)


Lürssen Hydrofoil…

[11 Nov 01, updated 16 Dec 01] I wonder if IHS is aware that Lürssen once built a fully submerged hydrofoil of their own? Here is a photo of it from a book on the FR. Lürssen Werft which I found in our library. The book is titled: Fr. Lürssen Werft . Bremen – Vegesack – Builders of Fast Boats. “Reproduction or use of the whole or any part permitted if source is quoted.” Printer: H.M. Hauschild GmbH, 2800 Bremen. There was no publication date apparent on the book (which was undoubtedly a company handout). Only the slightest details about this hydrofoil were provided in the book. — Martin Grimm (seaflite@alphalink.com.au)

[16 Dec 01] I also now have found the pages with a little more detail of this hydrofoil. They have a chronology of the development of the company and for the year 1963 under ‘projects’ they indicate: “After the purchase of patents subsequent development and construction of a hydrofoil with fully submerged foils [photo 63, reproduced at right]. Development of this type of ship is followed closely in the whole world.” Incidentally, in 1954 they also indicated under ‘projects’: Hydrofoil in aluminium BREMER PIONEER, length 19m. I seem to recall the BREMER PIONEER was one of the early Supramar-designed surface piercing hydrofoils. They did not have a photo of that hydrofoil in the book. In the same year they indicate under ‘Employees’ column that Gunther Popp was (engaged as) naval architect, he became manager in 1962 and technical director in 1973. Other employees are also listed in the book… perhaps one of them could recall more of the history of hydrofoil work at the company if they could be tracked down? — Martin Grimm (seaflite@alphalink.com.au)

Historic Canadian Hydrofoils Today

[11 Sep 01] When I was in Canada in 1996 I had a telephone conversation with Thomas G. Lynch (author of The Flying 400 – Canada’s Hydrofoil Project) through the publishers of the book, Nimbus Publishing Limited. Apart from the Bell/Baldwin HD-4 Hydrodrome replica and the BRAS d’OR museum display, the BADDECK (R-103) and MASSAWIPPI (R-100) are apparently still also preserved in Canada. I will now quote from the 1983 book by Mr. Lynch and then annotate with information from my phone conversation with him on 19 June 1996 while in Halifax:


  • R-100 MASSAWIPPI: From the 1983 book: “MASSAWIPPI was retired in 1959 and laid about in storage until she was presented to the Maritime Museum of the Atlantic, Halifax, N.S. in October 1966. Since that date, she has languished in storage in a shed in Mt. Uniacke, N.S., where it is alleged she is too large to display within the new museum building. Damage was reported to her upper deck from dry rot in 1982. Efforts are being made to either have her displayed or transferred to the Bell Museum in Baddeck, Cape Breton, but with little success to date.” From the June 1996 phone discussion: Condition of the craft has been stabilised following the wood rot. (Note: I tried to locate this craft in 1996 but without success. I didn’t find the right person to ask at the Maritime Museum of the Atlantic so can’t be sure of its status or current location).
  • Saunders-Roe Ltd R-103 BADDECK (originally named BRAS d’OR but renamed BADDECK in 1962): From the 1983 book: “BADDECK; R-103 was retired in 1970 and has spent the intervening years sitting in her cradle near the Fleet Diving Unit, Atlantic, on CFB Shearwater waterfront. Her fate remains uncertain, but efforts are currently underway to have her turned over to the Bell Museum as a natural descendant of the Bell-Baldwin genius of so long ago. However if efforts are not pressed, she might see scrapping yet.” From the June 1996 phone discussion: Preserved in the Museum of Science, understood to be in Ottawa. The craft is apparently intact and well maintained, to the point of turning over the gas turbines.

Note that the book includes arrangement drawings of the R-103 and of R-100. — Grimm, Martin (seaflite@alphalink.com.au)

Responses…[11 Sep 01] Further historical description and photographs of the Bell/Baldwin Hydrodromes HD-1 through HD-4 can be found in the book Bell and Baldwin: Their Development of Aerodromes and Hydrodromes at Baddeck, Mova Scotia, by J. H. Parkin, University of Toronto Press 1964. This book also describes the continuation of the HD series, starting with HD-7 by “Casey” Baldwin after Bell’s death and after Casey’s failure to interest the Navy in towed hydrofoil targets. According to the book, several hypothetical designs were developed over the years, HD-7 through HD- 20, but only HD-12, a 30-foot runabout, and HD-13, an outboard motor hydrofoil boat, were actually built, both in 1928. — Barney C. Black (Please reply via the BBS)

[4 Jun 03] The Nova Scotia Museum used to store the R100 (Massawippi) hydrofoil in a shed at a Provincial Historic site called Uniack House. This is quite close to Halifax. This is memory more than fact. I will try to verify this year. I will over the next year or so be scanning some images I have inherited from Casey. I would be more than happy to share them to this site if anyone is interested. — Sean Baldwin, MCM2001, Inc. (sbaldwin@mcm2001.ca)

World War II German Fast Attack Hydrofoil Craft

[3 Sep 01] I am a 16-year-old undergraduate student in Parma – Italy who is performing assigned research on German fast-attack boats (in particular hydrofoils) of War World II. Although the historical part of your WebSite is a very comprehensive one, I was unable to find there some detailed technical information I need for my writing. Would you be so kind to address me to other more detailed WebSites dealing with the topic or key person (like the late Captain Johnston) who could help me further? Also, are there relevant books on the subject? — Flavio Scarpignato (scarpi@tin.it) or (carmelo.scarpignato@unipr.it) e-fax: +1-603-843-5621; website: http://www.unipr.it

Response…[3 Sep 01] Following are some quick ideas:

  • There is a 1982 book: Strike Craft by Antony Preston; Bison Books Ltd (17 Isherwood Place; Greenwich CT 06830 USA) ISBN 0-86124-068-5. This book contains many photos and much history of German E-Boats and S- Boats… no specific WWII hydrofoil history however. There are several used copies of this book available at http://www.amazon.com. There is a photo of this book on the IHS website at //archive.foils.org/popbook.htm.
  • A search for fast attack boats and torpedo boats on amazon.com yielded several interesting titles, but I do not have a copy of or know the specific contents of any of these: German Coastal Forces of World War Two by M.J. Whitley; Coastal Forces (Brassey’s Sea Power : Naval Vessels, Weapons Systems and Technology, Vol 10) by Barry Clarke, Jurgen Fielitz, Malcolm Touchin, Geoffrey Till (Editor); From Monitor to Missile Boat : Coast Defence Ships and Coastal Defence Since 1860 by George Paloczi-Horvath; Fast Attack Craft by Anthony J. Watts; Fast Attack Craft : the Evolution of Design and Tactics by Keiren Phelan; Fast Fighting Boats, 1870-1945 : Their Design, Construction, and Use by Harald Fock; Die Flottille : aussergewoehnlicher Seekrieg deutscher Mittelmeer-Torpedoboote by Wirich von Gartzen; E-boats and coastal craft : a selection of German wartime photographs from the Bundesarchiv, Koblenz by Paul Beaver; Z-vor! : internationale Entwicklung und Kriegseinsèatze von Zerstèorern und Torpedobooten, 1914 bis 1939 by Harald Fock; Fast Fighting Boats, 1870-1945 : Their Design, Construction, and Use by Harald Fock; Flottenchronik – Die an den beiden Weltkriegen beteiligten aktiven Kriegsschiffe und ihr Verbleib, by Harald Fock, erschienen 1995 im Koehler Verlag.”Mit diesem Buch wird erstmals der Versuch unternommen, das Schicksal der an den beiden Weltkriegen beteiligten aktiven Kriegsschiffe aller Nationen darzustellen.Das Werk umfaßt die Kriegs-und Nachkriegsschicksale für den Zeitraum 1914 bis 1980 in chronologischer Reihenfolge”.
  • There are three hydrofoil attack craft on Michael Emmerich’s Kriegsmarine site at the following locations:
  • There was a magazine article: von Schertel, Baron Hanns, Hitler’s Hydrofoils, The Best of Sea Classics, Summer 1975 and Sea Classics Jan 74, Challenger Publications, Inc. Canoga Park CA, USA, pp 4-9, reprinted from Aviation & Marine Magazine, France. Baron von Schertel first began experimenting with hydrofoil craft in 1927. This article gives details on German hydrofoil development during World War II. In 1939, the military first became interested in a 2.8 ton hydrofoil demonstration boat. Various hydrofoils followed that craft, including the VS 6, VS 8, VS 10, TS-1 Coastal Surveillance Hydrofoil, Single-Seat 3-ton torpedo boat, and the 4-ton Pioneer Corps workboat.Hopefully some of this will be of assistance to you. Unfortunately IHS is not a source of the documents cited above! — Barney C. Black (Please reply via the BBS)

    [9 Sep 01] You might add another book to the reference list: Marine-Kleinkampfmittel by Harald Fock, Nikol BVertragsvertretungen 1996, ISBN 3-930656-34-5. This is the book where I found the German hydrofoil projects described. – Michael Emmerich (emmerich@german-navy.de)


Piaggio P.7 Hydrofoil Seaplane

[6 Jul 01] I have located a hydrofoil related website which of historical interest: http://aeroweb.lucia.it/en/history/pegna2.htm. Here is the background to my locating this site: I took trip North where I called in on the Fighter World aircraft museum alongside the RAAF Williamtown air force base in New South Wales, Australia. On display at the museum were numerous entirely hand made scale models at approximately 1:72 scale or smaller by Norm Forrester. These included a series of Schneider Trophy seaplane models. One such model which particularly caught my eye was the Piaggio P.7 of 1929. It was a sleek monoplane with a hydrofoil undercarriage rather than the usual bulky pair of floats. Here is the blurb by Norm Forrester placed alongside his model: “Piaggio P.7 (1929) — An ingenious (but unsuccessful) Italian design for a Schneider Trophy racer, it was proposed to use hydrofoils instead of floats. The driveshaft of the 970 HP engine first drove a water propeller until the P.7 rose on to the hydrofoils, the drive then being transferred to the airscrew. Alas, it didn’t work!” Although I have read about various other similar attempts to use hydrofoils on seaplanes, I have never come across the Piaggio P.7 before. I was keen to find out more about the P.7 and its history which I have found on the cited webpage. Unfortunately my camera was not working so I couldn’t take a photo of Norm’s model, however I made a sketch from my video footage of it. The website also has three views and profile views of the P.7 on the link but they are not too crisp and much of the detail in those scans has been lost. — Martin Grimm (seaflite@alphalink.com.au)

Responses…[29 Sep 01] I would like to inform you that some additional pictures are available on the following website: www.aviogatti.it (click on the Schneider chapter). Pushed by curiosity, I recently visited this site which corresponds to an Italian bookshop, specialized in aeronautics, and the pictures are included in a story, written by the very known Naval Arch. Franco HARRAUER, in Italian. He describes a sort of tale, on which the test pilot Tommaso Dal Molin, flying the Piaggio PC-7, on 1931 wins the 13th Schneider Trophy. Unfortunately, the dream ends very soon and the sad reality was that this seaplane never had the possibility to fly and win. Mr. Dal Molin, tragically died flying another seaplane during the tests, and the Piaggio PC-7 “Pinocchio” , with a lot of unsolved mechanical problems, never had the chance to demonstrate the validity of the foils solution. — Lorenzo Bonasera (email address withheld)

[11 Nov 01] Although I was not able to read the Italian text in the further website you have identified, I was delighted to see the three view drawings of the PC-7 and the photo of it floating (just!) in the water. With those additional drawings, it is tempting to try to build a radio-controlled model of this lovely racing plane just to see how it may have performed! Thanks for finding and reporting on that additional website. — Martin Grimm (seaflite@alphalink.com.au)


[22 May 01] Last week, leaving Paine Field in Everett Washington, I spotted a familiar shape next to the fence. Going over, I checked and sure enough, it was LITTLE SQUIRT, up on blocks for storage. Its against the fence, on Boeing property, close to the main airport entrance drive, just beyond the Museum of Flight restoration facility. I asked a friend Bob Desroche, who works just down from where LITTLE SQUIRT is parked, to take some pictures. Here is how she looks today. — David Lednicer (dave@amiwest.com)


LITTLE SQUIRT Today - Port Side LITTLE SQUIRT Today - Stern LITTLE SQUIRT in action

Aquavit 10-Passenger Hydrofoil…

[1 May 01] Attached are drawings I had done of my Aquavit 10P, Front & Side elevations. I request that anyone with information on this craft, please scan it and send a copy to me. This includes technical info, sales material, photos of specific vessels, anything related to the Aquavit 10P. Thanks! — Vik Poremskis (viktor_por@yahoo.com.au)



[01 May 01] Noting your e-mail address suggests you are living in Australia, I am curious to know more about the Aquavion 10P that you have. Is this by any chance the one which has been laid up at Gonsalves Boatshed at Pittwater north of Sydney? I have attached a photo of that craft I took several years ago. If it is one of the several Aquavion hydrofoils imported into Australia, do you know any more about the history of them that you could share with the IHS? It seems to me that Aquavion must have manufactured at least three models of hydrofoils with increasing passenger capacity ranging from: 1.The Waterman, 2. The 10P which is also apparently referred to as the Aquavit, and 3. The 40P which was also referred to as the Aquastroll. — Martin Grimm (seaflite@alphalink.com.au)


[16 May 01, updated 29 Jun 02] I will be making available some of the Aquavion materials that Vik has provided to IHS. These files are in Adobe Acrobat format, and are rather large files in most cases. Following are links to the files that are currently available from this site or from www.exigent.info.– Barney C. Black (Please reply via the BBS)

Luerssen Hydrofoils

[4 Mar 01, updated 6 Apr 02] A shipyard manager from Luerssen Werft GmbH, Bremen told me something about the small hydrofoil Luerrsen built in the early seventies. This boat was a experimental prototype, fully developed by Luerssen. It worked well, but the idea fell out of favor at Luerssen so they donated the boat to the “Auto & Technikmuseum – Sinsheim. He said also that Luerssen built 6 experimental hydrofoils including the shown one after World War II. These were mostly built without a yard number (sounds like Luerssen tried to keep these experiments as secret.). He could not say where these boats are today, but if someone will search in small yacht habours, some sheds, warehouses, scrapyards and the depots of the German authorities and the navy, he could find astonishing things. (So I have found a small Russian type Ekranoplan in a small shipyard near Hamburg last year). I got the name and the phone number of one of the chief developers of the Luerrsen experimentals, a guy named Dr. Osterstehte. I will call him and ask him to get some closer information about the experiments. By the way: Do you know the concept of the “Wenddelsches Schnellschiff” (transl. Fastship), developed by Professor Wenddel, a former collaborator of Baron v. Schertel ? A experimental prototype exists in the collection of the German Navigation Museum in Bremerhaven, Germany. Click Here for photos of the Luerssen craft, the Wenddelsches Schnellschiff, and another 1950s era prototype craft (Adobe Acrobat format). Another idea was the hydrofoil project of the German engineer Dr. Ingo Schloer. He has worked out a concept, which looks like the crossing between a SWATH, a fixed wing hydrofoil, and a PHM. There is a picture of it in a German book about Fast Attack Craft. This project vanished into the drawer for uninteresting projects in the German Ministry of Defense. I will inform you, if can get more information about the Luerssen hydrofoils. –C. Schramm (Chr_Schramm@gmx.de)

 Response…[10 Apr 02] I was delighted to learn that the Lürssen Werft experimental hydrofoil is still in existence and in apparently quite good condition. Just as interesting is the BREMER PIONEER test model and the fully submerged hydrofoil design by Schiffbau-Ingenieur F.H. Wendel. I had recognized the shape of that craft and knew I had seen it before in a book. Some details of Ing. Wendel’s designs appear in: Fock, Harald, Fast Fighting Boats, 1870 to 1945, Their Design, Construction, and Use, first English edition, 1978 (originally in German 1973), Naval Institute Press, Maryland USA. See IHS website for more details. Part four of the book covers the war years and includes hydrofoil developments. It includes diagrams of Ing. Wendel’s concepts including a foilborne photo of the craft now preserved in Bremerhaven. I do not know what type of stabilisation system was used on that boat. The illustrations of his military designs suggest that all three foils had flaps fitted, and the 1952 test craft seems to be the same when looking at your photos. It is not clear what controlled those flaps as your photos and the one in the book do not clearly show any mechanical ‘water surface sensor’ as was typical of the Christopher Hook fully submerged hydrofoils of similar vintage. There is what may be a surface skimming sensor on the aft strut which looks like a smaller foil positioned above the main aft foil. The flaps on the bow foils also look like they may have some form of servo tab behind them. The alternative is that the hydrofoil had some early form of electronic or electro-mechanical stabilisation system. Is it still possible to look inside the hydrofoil and see what may have been fitted? Perhaps you could get permission to do that when you next visit the museum? Take a ladder with you! It would also be good to obtain more close up photos of the foil and flap units. Would the museum have more information about this hydrofoil and how it worked? The propeller positioned forward of the aft foil as originally fitted to Supramar PT-20 surface piercing hydrofoils are also reported to have resulted in problems. This seemed mainly to have been due to propeller damage from debris. It is better that a log hits a strong foil than a relatively soft and thin propeller blade that can easily be bent! Also, Supramar had to solve early problems with cavitation erosion on the PT-20 propellers. I don’t know if the swirl in the flow aft of the propellers would be too much of a problem for the flow over the foils (this is after all the standard layout on propeller driven aircraft) but I have not seen any other hydrofoil design with podded propellers that are positioned forward of the foil. — Martin Grimm (seaflite@alphalink.com.au)

HS VICTORIA / Seattle – Victoria BC

[13 Feb 01] My family owned and operated the HS VICTORIA, Northwest Hydrofoil Lines, Inc. from when she was built in 1965 to when she was scrapped sometime in the 1980s. I have a lot of information, articles, pictures and first hand accounts from my uncles and my father, who operated her from Seattle, WA. to Victoria, BC. I would like to share this information with other people who enjoy this web site. — Mike Niedermair (NiederM@nima.mil) or (Niedone@aol.com)

Response…[17 Feb 02] There is a 12 page information booklet about H. S. VICTORIA posted on the IHS website. The file is in Adobe Acrobat format, and is rather large at 1.8 meg file size. Please be patient while it downloads. For those with slow internet connections, it is probably better to download the file entirely onto your hard drive, then open it with the free Acrobat Reader. — Barney C. Black (Please reply via the BBS)

Victoria in Seattle

Grumman Concept Drawing [18 Jan 01] Looks to me to be a proposal/preproposal artist rendering of what eventually became the MARAD-funded H. S. DENISON. Don’t recognize the designation of “PK-89”; all Grumman hydrofoil designs had an “M” followed by a number. Purpose of program was to demonstrate open ocean hydrofoil capabilities; which it did at a recorded speed of 60 knots. DENISON was built at the main Grumman facilities in Bethpage in the center of Long Island, and trucked at night to Oyster Bay for final assembly and launching. Charlie Pieroth (SoundTM@ix.netcom.com)


[2 Dec 00] I am the current owner of a 36′ hydrofoil that operated out of Juneau, Alaska in the late 1970s. It is a welded aluminum, stepped hull passenger ferry that was crashed. I recovered it 15 years ago in Ballard, Washington (it was stripped down, with no motor, or foils). I don’t know the builder’s name, but I have the hull identification number. It was called the JUNEAU FLYER. I am thinking about restoring it as a hydrofoil. I am interested in any information regarding hydrofoil technology and information on the JUNEAU FLYER. I know that she had a gas turbine engine in her, and I think she had fixed foils. If you’ve seen the James Bond movie Thunderball, there is a hydrofoil that detaches from the front of a larger boat, and the hydrofoil looks very similar to the JUNEAU FLYER. — Carl Van Valkenburg (carlnat@buttes.net)

Responses…[2 Dec 00] The Thunderball vessel was named DISCO VOLANTE. There is a picture on the Rodriques Cantari Navali webpage on this subject: An ad placed subsequent to filming reads: “Safe, thrilling, spectacular, FLYING FISH was used in Thunderball, one of the most popular 007 James Bond [movie] sagas. FLYING FISH was the first commercial hydrofoil [for] sightseeing use in the Western Hemisphere. The advertisement: All-aluminium, 20 tons, 65 feet long, propeller-driven. She moves at 20 m.p.h. with her hull in the water. When up on her foils, she glides smoothly above the seas at 40 m.p.h. Comfortable, all-enclosed, wide window passenger compartments. Deep cushioned aircraft-type seats. Forced-air ventilation. Capacity: 60 passengers. Completely safe, Coast Guard approved. Unsinkable hull has eight watertight compartments for buoyancy. Diesel powered, no fire hazard. Smoking permitted at all times. Type: PT 20 ; Seats: 72; Yard building number: 052 ; Delivered in: 1957; Line: Manila-Corregidor; Country: Philippines” — Barney C. Black (Please reply via the BBS)

[18 Feb 01] FLYING FISH was outfitted at Miami Shipbuilding Corp. for her role as the DISCO VOLANTE. In the limited edition DVD of the movie Thunderball, there is a section on the Making of Thunderball that has a scanned photo (b+w) of the FLYING FISH in the MSC yards. I’m searching for further information–Plans, etc., on the FLYING FISH for a model I plan to build. — Doug Binish (email address withheld)

Who Invented the Hydrofoil?

[2 Dec 00] Who invented the hydrofoil? — Various… this is a FAQ

Response…[2 Dec 00] Following are two different opinions on this subject. We invite those with other facts or opinions to submit them! Another source of information on early hydrofoils is the book, Aeromarine Origins; The Beginnings of Marine Aircraft, Winged Hulls, Air-Cushion and Air-Lubricated Craft, Planing Boats and Hydrofoils by H.F. King, Putnam (London) and Sero Publishers, Inc (USA), 1966. Meanwhile, see the IHS photo gallery for more on early hydrofoils. — Barney C Black (Please reply via the BBS)

  • “The first hydrofoil boat was the product of an accident in 1861, when Thomas Moy, an Englishman, decided to study the aerodynamics of wings by observing the underwater swirls they created. Having attached wings to his craft, he ventured out onto the Surrey Canal. To his surprise the ship rose from the water — and unintentionally he had invented hydrofoils. But it was not until 1898 that the first efficient hydrofoil was designed by Enrico Forlanini of Milan in Italy. His craft, powered by aircraft-type propellers, reached a speed of 44 knots (81.5 km/hr or 50.6 mph).” Source: Hamilton, Ian, “The Hydrofoil as Weapon,” Pacific Defence Reporter, Aug 1981
  • “The first evidence of the use of hydrofoils on a boat or ship was in a British patent of 1869. It was granted to Emmanuel Denis Farcot, a Parisian, who claimed that ‘adapting to the sides and bottom of the vessel a series or inclined planes or wedge formed pieces, which as the vessel is driven forward will have the effect of lifting it in the water and reducing the draught.'” Source: Hayward, Leslie, “The History of Hydrofoils,” Hovering Craft and Hydrofoils, Vol 4. No. 8 (May 1965) through Vol. 6, No. 6 (Feb 1967).


[11 Nov 00] I have an uncle that served aboard the PGH-2 TUCUMCARI. He was aboard her when she hit the reef. I was wondering if you knew where she was today? I have been looking for a long time and just now found this site. — Caleb Hagarty (CCH1985@aol.com)

Response…[19 Nov 00] After the TUCUMCARI was put on the reef, it was transported to David Taylor Naval Ship Research and Development Center, Annapolis MD Division (across the water from the US Naval Academy). The ship was stripped of many of the major equipment, and the remaining hull was used to study fire fighting techniques for aluminum ships. Some of the lessons learned were the use of various plastic and fiberglass pipes, which ones held up, which ones melted, and which ones were toxic. This led to establishing specifications which are used in many of the current Navy ships. Also studied were the effectiveness of various fire extinguishing materials such as CO2, Halon, and foam. — Sumi Arima (arimas1@juno.com)

Hydrofoil Amphibian – Student Project

[11 Nov 00] I am an graduate student from India pursuing a project on creating a amphibian craft… a vehicle that can move both in land and water. After a wide area of thought we have considered using hydrofoils with wheels at the bottom to enable us to have not only a large wheel clearance but also lesser drag in the water. I would like to know if there is any information regarding such a project anywhere else in the world. — Janak (ragus@netkracker.com)

Response and follow-up…[11 Nov 00] In the 1950s and 1960s, the US Army, Navy, and Marines all experimented with hydrofoil landing craft. Some of these were amphibians, specifically: the DUKW (by AVCO Lycoming and Miami Shipbuilding Corp for the US Army) , LVHX-1 (by AVCO Lycoming for the US Marines), and LVHX-2 (by Food Machinery Corp — now United Defense — for the US Marines). Photos and more information about these vessels can be found elsewhere on our site, specifically in the History of Miami Shipbuilding Corp (MSC) and in the 1950s section of the Photo Gallery. — Barney C. Black (Please reply via the BBS)

[18 Nov 00] I would like to know what difficulties were experienced, for such crafts seem to have completely vanished. Then too, the 1960s is a very long time ago. The DUKW and the LVHX2 both seem to have either retractable hydrofoils or fixed ones, the wheels being extendable. I was wondering if we could place the wheels directly onto the hydrofoils. That would give the rider a perfect birds eye view . Although such a craft would not be very road friendly, they would definitely be very useful near the shore and on the beach. Another idea was to use non submerging fans, like the ones used on hovercrafts for propulsion. That would enable us to have free moving wheels. If the wheels were also submerged, there would be no necessity for separate rudders, the wheels may itself act as rudders. That will help simplify mechanics. For added stability at low speeds, we are also thinking about using a trimaran type hull. Please let me know what you feel about these ideas. Knowing what went wrong with the 1960s projects may help us. We hope to first start with making a scale model. — Janak (ragus@netkracker.com)

[19 Nov 00] The DUKW and LVHX craft were successful, although they were mechanically very complex and heavy for their payload capacities. Their amphibious capability is greatly exceeded by Air Cushion Vehicles (ACVs). Use of a trimaran hullform will add stability and reduce powering requirements. The design challenge is to obtain satisfactory cargo volume on a trimaran center hull that is more slender than a monohull of equal full load displacement. — Mark Bebar (bebar@foils.org)

Mexican Hydrofoils NICTE-HA and XEL-HA

[20 Sep 00] Does anyone have any idea what happened to the couple of Rodriquez hydrofoils that were sold (?) in Mexico in the early 80s, NICTE-HA and XEL-HA? Ever seen any pics of them there, operational or otherwise? Tim Timoleon, Editor, Classic Fast Ferries (classicfast-f@email.dk) website: http://go.to/classicfastferries.

Indonesia Hydrofoil LUMBA LUMBA Info Wanted

[16 Sep 00] When I was a kid growing up in the jungle oil camps of Sumatra Indonesia during the 1950s and early 1960s I vividly remember the excitement of traveling across the Strait of Malaca from Indonesia to Singapore on board a modern (for the time) passenger hydrofoil called the LUMBA LUMBA (which is the Indonesian word for the grey dolphin in the area). I am trying to obtain any information I can on this wonderful vessel. Perhaps it is even still in service somewhere. I was in a model shop in London maybe 10 years ago and saw a kit for the LUMBA LUMBA. I wish I had purchased it. Any information would be appreciated…and will help bring back fond memories. — Rob Briggs, Atlanta, GA, USA (briggsfamily@mediaone.net)

Response…[16 Aug 00] Thanks for your most interesting inquiry, but LUMBA LUMBA on the Indonesia/Singapore route is a new one on me. I will post this on our website and also forward it to several of the “old timers” in our membership in the hopes that someone will know something about that vessel. You should browse through the photo gallery section of our website to see if you recognize the model from any of our photos. Also, Jane’s used to publish an annual or biannual directory “Jane’s Surface Skimmers” dating back to 1968; with many photos and descriptions, organized by country of manufacture. A library or old book shop may have an early edition, or they occasionally go up for auction on www.Ebay.com. I looked in the 1969/70 edition and did not see this vessel by name, but you might recognize the type from photos. For example, the Supramar PT-20 type was popular in the oil industry dating back as far as 1957. You could also contact the Classic Fast Ferries website. The Fast Ferry International Database of 1995 lists a LUMBA LUMBA being operated by the Pulau Seribu Marine Resort in Indonesia, but this is a monohull built by Yamaha in 1989. As for models, there is a secondary market for old model kits, so it may be possible to find one. Occasionally they go up for sale on Ebay, though in 2+ years of monitoring this site for hydrofoil-related items I have never seen a kit specifically of LUMBA LUMBA. — Barney C. Black (Please reply via the BBS)

Miami Shipbuilding History

[18 Aug 00] I write, edit and publish and annual historical magazine for the Friends of the South African Air Force Museum. Last year one of the articles I wrote was on the SAAF crash boats/rescue boats. From that an interest arose on researching the full history of the Motor Boat Unit. To this end I have been engaged in a number of interviews with surviving members, and archival research. One of the people instrumental in us getting these boats was the designer a Mr. Dair N. Long, a naval architect at the University of Michigan. He designed what were known as Miami boats which were built by the Miami Shipbuilding Company (MSC). I wonder if it would be possible for you to tell me anything about this gentleman, more about the company and if there are any relevant documents available. — Guy Ellis (Guy@datasoft.co.za) website: http://www.dynagen.co.za/eugene/guy.html

Response…[9 Sep 00] My father worked at MSC around 1939-41 when the USA entered World War II. They were building and repairing ASRs then for the European arena. We attended a party when MSC went out of business as that company, the current owner, Mr. Brown was there. If you’re interested, My father has many stories about the times back then. You can contact him at the following address (or c/o my email address): Dick Besola, Sr., tel: 305-891-5942, fax: 305-891-2116, — 1570 NE 141 Street, N. Miami, FL 33161 — Dick Besola, Jr. (shark1dick@aol.com)

Sydney Harbor Hydrofoils

[8 Sep 00] A total of 7 hydrofoils operated on Sydney Harbour over 26 years, as listed below. The LONG REEF, CURL CURL, and SYDNEY were part of State Transit’s fleet of hydrofoils, which operated between Sydney and Manly from 1965 to 1991 before being replaced by Incat Jetcats. MANU WAI (now offered for sale after extensive renovations and repair of grounding damage) was shipped as deck cargo from Auckland NZ after our purchase.

    • MANLY Hitachi Zosen PT20 (1965)

    • FAIRLIGHT Rodriquez PT50 (1966)

    • DEE WHY Rodriquez PT50 (1970)

    • CURL CURL Rodriquez RHS140 (1973)

    • PALM BEACH [ex-PATANE] Rodriquez PT50 (1969/1976)

    • LONG REEF [ex-FRECCIA del MERGELLINA] Rodriquez PT50 (1968/ 1978)

    • MANLY Rodriquez RHS160F (1984)

  • SYDNEY Rodriquez RHS160F (1985)

LONG REEF, CURL CURL, MANLY, and SYDNEY survived until 1991 and were taken back to Italy by Rodriquez to be resold or leased in the Mediterranean by various operators. CURL CURL was renamed SPARGI and is now on the market for US$500 000. Both RHS160Fs are in service to the best of my knowledge, I am unsure of LONG REEF ‘s status. — Garry Fry (gfry@vtown.com.au)

Death Notices, Obituaries, and In Memoriam

[18 January 16] Kotaro Horiuchi: IHS Member, Bulletin Board Contributer and Creator of Extraordinary Hydrofoils, & RC Hydrofoil Models

To all IHS members. It is with sorrow that I acknowledge the loss of my friend and IHS member, Kotaro Horiuchi. Here are words to remember him by, written in Japanese Kanji symbols by his son, Satoshi Horiuchi and reviewed by his first cousin, Ayako Timmons, translated using Bablefish with my editing:

Kotaro Horiuchi is my father. Today, everyone is busy with father’s funeral. The family is all together and I received much love and support, thank you, thank you very much. Father, as we know was very robust as of December of 2014. But in his last year he suffered and lost weight. He was a tough person, but then he developed Interstitial pneumonia, still his general health was good. He was recovering, and so he returned home, and continued to recover his energy.

Then the pneumonia temporarily took a dangerous turn and he was re-hospitalized. But by New Year’s day he was regaining strength; so he was again released home, provided there was 24 hour care. At home Kotaro resumed training on his ERGO ( boat training machine). His condition was rapidly improving, but on January 18, 2016, after having lunch and taking a rapid ride in his wheelchair, he suffered a cardiac arrest, and died quickly. His face was calm, and there was little suffering.

Father had a good life, I believe, but it was difficult when his wife, Atsuko, died 5 years ago at age 80. Atsuko was active to the end and had mastered rowing the skull, and won gold medals in the all Japan World Masters.

To fill the emptiness after losing her, my father for the first time had two lives. His early life was working as a boat Designer at Yokohama yacht, and Yamaha motor boat and yacht design. He designed hydrofoil propeller boats, pleasure boats and fishing vessels, including a wide range of original ocean-going boats. Also, he designed helicopters. Remote control helicopters are hung beside his front door. In addition, he created small cars and scooters, so he literally worked on vehicles for land, sea and air. Some of his creations were built in his workshop in shichirigahama, but occasionally he moved to Kamakura in cooperation with Yamaha. One of his last projects was finishing his father’s 17-foot trimaran cruiser.

The other life was as a racer of rowing boats. He rowed for high school, the University of Tokyo, and the Yokohama yacht Club. His specialty was rowing scull and kayak, and he had done so since childhood under the influence of his father, Juro. The Japan Rowing Association selected him as crew. Then as the crew chief for Tohoku University he competed in the 1960 Summer Olympics and the 1964 Summer Olympics. After a gap of some 50 years he again coached at Tohoku University for the Intercollegiate National Championship. Then he coached the Japan national team in the World Championships. Finally, he was once selected to be the Olympic coach for the Japanese rowing team.

I was anxious when father, at the age of 87 with health anxieties, flew to Varese, Italy, There in the world masters tournament for rowers up to 90 years of age he earned 3 gold medals. I was very pleased.

Satoshi Horiuchi

More: Kotaro will be remembered for his extraordinary design work including many important hydrofoils including several that can be seen in these videos:


In addition, he leaves us his book, in English:
Locus of a Boat Designer Vol. 2 His passing leaves a deep void.

Ray Vellinga  

[1 August 15] Barney Black, Past IHS Board Member and IHS Web Site, IHS Newsletters and IHS Blog Publisher

It is with great sadness that I report that long-time IHS member Barney Black passed away on 29 July from complications related to ALS. Barney was honored by IHS in 2001 for his outstanding contributions over many years to the Society’s communications efforts, specifically for setting up the IHS Website, Electronic Blogs and Newsletter publications. He also served for a number of years on the Board of Directors.

Barney had an unusually varied and multi-disciplinary career in the marine industry. He earned the unusual degree of B.S. in Humanities and Engineering from MIT in 1971.

He provided equipment, maintenance, and training to Navy, municipal, and civilian divers and fire fighters; worked in the SSN-688 Class Advanced Design Project Office at the Newport News Shipbuilding and Dry Dock Company; served as a consulting engineer to the Naval Sea Systems Command in Arlington, VA, supporting various design and modernization projects in mine countermeasures; provided logistic support for the PHM Class hydrofoils; and was a Senior Principal Engineer at TRW.

More recently, Barney was a Senior Logistics Management Specialist on the US Coast Guard’s Deepwater Project. Barney Black will be greatly missed by all who were privileged to know him and our prayers are with his family.

Mark R. Bebar

President, IHS

A more detailed Memorial to Barney can be found here: In memorium IHS Past Board Member Barney Black.

[11 April 14] John R. Meyer Jr., Past IHS President

To all Members of IHS,

It is with regret and sadness that I pass along the news of John Meyer’s death. John had been battling cancer and was recently in the hospital for treatment. He elected to return home on 10 April and passed away on 11 April 2014.

The Memorial will take place on Saturday 17th of May 2014 at 3:30 pm in the Pilgrim Lutheran Church – German Lutheran Church Washington DC – is renting from them. 5500 Massachusetts Avenue, Bethesda, Maryland 20816

Please keep John’s wife, Gigi and his sons, Kurt and Craig, in your thoughts and prayers.

Mark R. Bebar

President, IHS

A more detailed Memorial to John can be found here: In memorium IHS Past President, John R. Meyer Jr.


[16 Oct 12] Sadly, Dr. Sam BRADFIELD, 94, of Melbourne, died Tuesday, October 16, 2012. The International Hydrofoil Society ( IHS) awarded Dr Bradfield an Honorary Life Member Award in recognition of his extensive contributions to the hydrofoil community over many years on 26 Feb 2010.

[7 Mar 03] With regrets I must inform the hydrofoil community that I received the message this morning from Ed Hermanns, that our colleague of many years, Ray Wright, passed away last week. To those who never met him, Ray was the Chief Hydrodynamicist at Grumman up until his retirement. As such he was always a key member of the hydrofoil development team at Grumman. Ray was a quiet man, dedicated to his faith in God and science. He was a true gentleman, and dedicated his professional career to the science of hydrofoil hydrodynamics. Few in this small field, knew as much about the subject as Ray, yet he was always willing to teach and discuss. He was deeply respected by his peers. I personally learned much from him about the field of hydrodynamics and life. It may come as a surprise to many to learn that while trained in aerodynamics, he had a very deep distrust of any airplane enclosing him that was not firmly planted on the ground. Those wishing to express condolences, may write his wife, Myra; contact me directly for the mailing address. — Charlie Pieroth (SoundTM@ix.netcom.com)

Response…[11 Mar 03] I have a complete set of the Hydrofoil Design Specs that Ray contributed to so much. They are on my book shelf, and every time I look at them (and I have drawn very heavily on them over the past), I think of Ray and all the labor that went into this effort. As you may know I made sure that they were all scanned and made part of the Advanced Marine Vehicle (AMV) CD-ROM #1. So his work will live on. — John Meyer (jmeyer@erols.com)

[22 Dec 02] It is with regret that IHS reports the death of CDR Erich H. Ashburn, USN [Ret]. CDR Ashburn was OINC of PEGASUS throughout the Operational Evaluation (OPEVAL) process.

[18 Jun 02] Joseph F. Sladsky, Jr., President of Kinetics, Inc., PO Box 1071, Mercer Island, WA, 98040 died 7 June 2002 from cancer. His business will be disestablished by the end of the year. — Michael R. Terry, 425-881-6823 [According to the obituary in June 26, 2002 Eastside Journal of King County Newspaper Publications, submitted by Sumi Arima, “Mr. Sladsky was born March 9, 1941 in Czechoslovakia. He officially immigrated to Canada when he was 11 after living in a refugee camp in Czechoslovakia for two years. He cam to the United states when he was in hfoils.org”>www.hydrofoils.org

Design Studies For Hydrofoils and Struts…

[25 Oct 97] As part of DARPA’s assessment of the potentials for high speed ships, we have two groups doing some top level design studies for hydrofoils and struts. Is there a stress limit you would recommend using to account for a readily available high strength steel that would account for future detailed fatigue analyses? I don’t know if there’s any useful data from the prior hydrofoil programs that would shed some light on this. — Stan Siegel (stansiegel@aol.com)

Response…[2 Nov 97] I’m glad to hear there is still some interest in hydrofoils if only in regard to concept studies. Regarding the question of a stress limit for future detailed fatigue analyses, I can not suggest “a value” because of the many serious issues involved in such a selection. The most practical suggestion I can offer is for the parties involved to obtain the static strength, fatigue and flaw growth properties of the 17-4 ph material employed in the design of the PHM-3 series foil system. The cyclic loads which would be needed could be ratioed up or down from the Boeing load criteria as a starting point. Obviously they would need to retrieve and review the stack of Boeing reports involved- no small task in itself. As far as selecting a readily available high strength steel is concerned, such a step is a potential minefield as I think you know. I’m not a fan of 17-4 ph, but it was used with fair success in the PHM-3 series ships after a complete redesign of PHM-1 foil system. HY-130 was used successfully in elements of the PCH-1 Mod 1 foil system, but it (and the required coatings) were never subjected to the extended service experience of the PHMs. It may be the better material but we have no proof. Perhaps I’m being a bit too realistic for concept studies which sometimes are not very realistic in the first place. In any case, if I can be of further help to you don’t hesitate to contact me. — Bill Buckley (wbuckley@erols.com)

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