View Messages Search Messages Return to Home Page Frequently Asked Questions

The International Hydrofoil Society (IHS) Hydrofoil Message: Chats, Info Sharing, Networking

The International Hydrofoil Society (IHS) Hydrofoil Correspondance Archives

General: IHS Administration Design of Foils: Foil-Struts-Controls-Performance Design of Vessels: Hull-Machinery-Costs-Performance/Ops History of Hydrofoils: People-Vessels-Operations Hydrofoils: Commercial Hydrofoils: Military
Hydrofoils: Models Hydrofoils: Pleasure Hydrofoils: Sailboats R/D: Student Projects/Thesis etc. Sources, Buy/Sell: Brokers-Builders-Designers-Operators Miscellaneous:Hybrids-Other High Performance Vessels-etc.

Updated last August 20, 2006

Hydrofoils: Sailboats

Hydrofoils: Sailboats      Scroll To Top Top

    Latvian CATRI Sailing Hydrofoil
      Latvian CATRI Sailing Hydrofoil (Aldis Eglajs)
      [17 Feb 99] I received some further information from Aldis Eglais in Latvia (Lettland), the designer of the Catri 26R MicroFoiler. At the moment I'm still in the planning phase of my project but I intend to build the boat this summer here in Switzerland. Aldis is offering the plans for a very good price (US$ 1,300), and I'm very close to ordering them. I'm waiting now for his study plans. I will keep you informed. His E-Mail: -- Phil Schlund (

      [17 Feb 99] There is a short article about the Catri 26 Trimaran on page 48 of Multihulls Magazine Mar/April 1998 edition. The address given is Aldis Eglajs; Maskavas 291/5-26; Riga LV-1063, Latvia; Tel/fax : +371 7258427. -editor
      2nd Response...
      [17 Feb 99] In Winter 1997-98 I did a project for a Dutch company called PJPC Multihulls. They wanted to build the Catri 26 for the European market to sell for about US$50,000. There were complete plans for making the (eastern European) ship suitable ( more comfortable) for the rest of Europe, which was part of my study (I was asked to design a mechanical device to lift the two swords). Unfortunately the Dutch company stopped their activities due to health problems of the owner, so I am at the moment looking for other tri-builders who could use my design. If you want to know more, contact me. -- Maarten de Jong (
      3rd Response...
      [21 Feb 99] We are working out two types of Catri Foilers -- trailerable cabin boat range (22' 26' 30') and offshore cruising & racing range (35' 39' 45'). After very successful prototype tests in the Netherlands there are two shipyards in Latvia started with 22' and 26' and one in San Francisco starting with 26'. The first boats will be delivered this Summer. The 30' will be started in March for delivery beginning 2000. There are some homebuilders in Australia and elsewhere. You can find our presentation and description of Catri 22, 26R, 30 as well as the draft price list in the attachment. -- Aldis Eglajs, Catri Marine (
      [Date/Time=03-21-2002 - 10:52 PM] [Msgid=236662]

    Sailing Hydrofoils
      Wants World Speed Record in Sailing

      [13 Jan 02] This looks exactly like the site I need. I want to have a crack at the wind-powered water speed record, and I reckon the only way we're going to get the thing fast enough is up on a foil. The only problem is I have absolutely no idea. If anyone has info. it really would be appreciated (formulas/heights anything to help me build the hull) -- Ian Montgomery (

      [13 Jan 02] The world sailing speed record was once held by a hydrofoil - Greg Ketterman's LONGSHOT. This boat has since been adapted for production as the Hobie TRIFOILER . A used TRIFOILER would be a good way to get experience in high speed sailing. In my opinion, the world speed record has risen out of the reach of subcavitating hydrofoils. The current record holder used planing hulls, which you can think of as fully ventilated supercavitating foils operating at the surface, which is where a supercavitating foil is most efficient. Cavitation proved to be a barrier to Ketterman's pushing his hydrofoil to today's speeds, and I doubt if there's much you can do with section shaping to raise the cavitation speed much higher. Designing a supercavitating hydrofoil system that had a lift/drag ratio adequate for a sailing craft is just feasible, but requires very sophisticated hydrodynamics design. Hydronautics' experience with their supercavitating helicopter-towed sled demonstrated drag reductions on the order of 40% -60% just by doing a more sophisticated type of analysis of the spanwise hydrodynamics of their design. You'd have to do the same for a sailing hydrofoil. Something like the Windjet LANDYACHT adapted for the water might be a starting point for the hull and rig design. -- Tom Speer (; website:

      Monohull Dinghy...
      [5 Mar 01] Is there any website on a leeward-foil assisted faaast monohull dinghie, say an IC, Contender or 505 with a Bruce on a 3m lever ? -- Claus-C. Plaass - Pickert 10 - 24143 Kiel - Germany - email  (, ph +49-431-36 800

      [5 Mar 01] Not only foil assisted, full flying: -- Tom Speer (; website:; fax: +1 206 878 5269
      [6 Mar 01] I have designed a 16' 100lb 2-person monohull foiler using two(only) fully submerged foils; should be sailing in 2-3 months. Take a look at the Hanno Smits website (listed under websites of IHS members) for info on his work with SP foils and a FLYING DUTCHMAN. Personally, the Aussie work on their Moths is most inspirational and should lead to light weight production monohull foilers that while not as fast (top end) as some multihull foilers will provide the thrill of flying to a much wider audience. -- Doug Lord (

      Hydrofoils Excluded From TheRace2000...
      [9 May 00] TheRace headquarters has admitted that they limited the entry of our hydrofoiler for the No Limits Race around the world. Their discrimination against foils has seriously impeded the development of effective offshore sailing hydrofoils. Our potential sponsor withdrew when our entry was denied. If they reverse the decision now, there is still a chance to pull it off. The prototype is complete. Our nine foot wide horizontal spans are designed to retract when we hit the inevitable obstacles. Please email with a copy to and ask them why they are discriminating against hydrofoils and why they still call this a "no limits" event. You can make a difference. Thank you for your support. Peter Murray Tel.#(1)561-286-2643

      VOLANTIS 60' Sailing Trimaran...
      [12 Feb 00] I just attended a meeting of the Northwest Multihulls in Seattle where Duff Sigurdson of Canada presented the latest news on the 60 foot trimaran planned to be built in Hawaii. Sam Bradfield has designed the foils thus she will have inverted T-foils and small amas. Nigel Irens is the designer. They plan a solid wing with reefable/furlable center section, and a hard vertical tab on the lower leech of the rig for depowering. It looks like a more delicate Rave Trifoiler, with a single CF gull-wing crossbar. I was impressed, even considering that Queen Elizabeth II is supposed to christen it. It is not immediately clear that "Volantis" is meant for The Race. Burt Rutan will build the foils in his "Composites" shop in the Mohave Desert, and the majordomo is Adm. Stuart F. Plott, formerly head of seaborne infiltration efforts during the late unpleasantness in Vietnam. Duff also talked about aquatic satellites- small versions of the hardsail trifoiler that would be permanently at sea, monitoring the shipping lanes and seaport accesses, video-monitoring incoming ships for oil dumping/bilge pumping. Solid wings again? Please contact Duff Sigurdson for more accurate news- he is the new publicist: formerly associated with the Ronin project for The Race. -- Dave Carlson ( website:

      Moth Class Sailboat Races With Foils...
      [25 Feb 00] In a world first, Western Australian International Moth Class dinghy sailor Brett Burville has cracked it with a Foiler Moth, winning outright two heats of the World International Moth Class Championships held in Perth last week and finishing a creditable 10th place overall. The International Moth class is one of the few truly development International sailing classes and also allows foil development. At times Brett was travelling at up to 1-1/2 times the speed of the top existing designs and easily won the races in which he stayed upright. This is no mean feat, keeping in mind that an existing Moth can outpace a 505 and is already the fastest 11' monohull in the world. Brett's boat is a standard Moth, with a larger-than-usual T-foil on the rudder and forward V-foils mounted at the end of the wings. It appears he showed bursts of incredible speed in the stronger winds, punctuated by many capsizes. Clearly there is scope for further development, perhaps with some form of sensor control. He was foilborne above about 8-10kts of wind and sailed both downwind and also upwind on the foils. In the light wind races he removed the foils from the simple mountings in a couple of minutes. This is a major achievement, as most foilers to date are only reaching speed machines, like sailboards. This is the first time ever for a foilborne craft to compete successfully around the buoys in all conditions in a truly international standard sailing competition. It is hoped that Brett will produce some further details and it is expected a lot of further development will now proceed, as it is possible to take any existing Moth and truly revolutionise its speed in winds over 10 knots! Who will be first to take it further?? -- Ian Ward (

      [25 Feb 00] See also the article and photos in the Jan 25, 2000 Sailing News from Boating Oz. Also, information and photos from various sources was reprinted in the Spring 2000 edition of the IHS newsletter.

      Racing Boat Design Source...
      [2 Apr 99] Does anyone know where you can get designs for jet boats (sport/racing versions - not fishing/commercial)? Please email me. -- Mathew Davies (

      [3 Apr 99] The following groups run both propeller boats and JET (impeller) boats in various classes. The prop boats are quicker but both achieve speeds in excess of 200 mph regularly. Contacts (Hope the phone numbers are current.):

      Liquid Quarter Mile magazine (909) 989-1169
      IHBA International Hot Boat Assoc. (714) 634-4422
      ADBA American Drag Boat Assoc. (216) 543-9647
      NJBA National Jet Boat Assoc. (714) 993-2664
      SDBA Southern Drag Boat Assoc. (817) 662-0774

      -- Ken Cook (
      [Date/Time=03-23-2002 - 12:58 AM] [Msgid=237130]

    Flying Keelboat      ViewThread
      Has any one any knowledge of a monohull KEELBOAT using hydrofoils in a full flying manner?My company at is about to introduce a canting keel model 42" in length that I believe may be the first fully flying hydrofoil keelboat called the aeroSKIFF. Any comments with substantiated information would be very helpful.I amm working on a version of this design for full size sailboat applications particularly in the Open 60 Class..
      [Date/Time=04-20-2002 - 4:44 PM]    Name:Doug Lord, [Msgid=249625]

    Flying Keelboat

      I have seen many multihulled sailing Hydrofoils and a few Centerboard/daggerboard/leeboard Monohulled sailing Hydrofoils. I have also seen Cantable Daggerboards and keels. I have never seen the combination you describe.

      Are the Foils fully submerged and attached to the keel or are the foils separate from the keel?

      At 42 inches, you might want to also post this message in the Sailing model section.
      [Date/Time=04-20-2002 - 4:59 PM]    Name:Bill White, [Msgid=249626]

    Flying Keelboat

      When you say Keelboat, I understand that to mean a sailboat with a centre keel? I am not aware of any such boat adapted to run foilborne. Looking though a publication by AYRS on sailing hydrofoils indicates that most experiments with sailing hydrofoils have tended to use hydrofoils mounted on outriggers or catamarans. In the case of monohulls, the foils are usually mounted off wide crossbeams and there is no keel below the hull in those case. The nearest I can come up with compared to what you outlined are a number of International Moth class sailboats that have been designed with hydrofoils fitted rather than the usual centreboard. Photos of these craft can be seen on the International Moth Class Association of Western Australia website at:

      I am curious about your own concept so I hope we will hear more about it from you down the track?

      [Date/Time=04-25-2002 - 7:47 AM]    Name:Martin Grimm, [Msgid=251569]

    Adding foils to 27-ft catamaram      ViewThread
      I am interested in adding hydrofoils to a 27-foot stiletto catamaran. Can you send me any information on how to start designing the foils and how they could be installed?
      [Date/Time=05-04-2002 - 8:24 AM]    Name:John Thomason, [Msgid=255277]

    Adding foils to 27-ft catamaram
      There are resources for you on the IHS website, but no quick and easy answer. Some thoughts that occur to me include:

      Take a look at our books page There are some titles on this subject, all out of print I believe. However they can be obtained with a bit of effort from a library, used bookstore or the eBay on line auction site.

      The Amateur Yacht Research Society has published a number of technical papers on the subject of hydrofoils, and these are all still available. There is a link to AYRS from our links page at

      The IHS has for sale the set of David Keiper files on adding foils to cats, however this design work was aimed at much smaller Beach Cats. Info on these files is at After David Keiper died, his work was continued and perfected by Dave Carlson. His email and website addresses can be found on our site by using the search engine on the main page. He is a good source of practical as well as theoretical information.

      You might want to consider getting a boat that is already foil equipped and was designed for it. The Catri is such a vessel. Information is on our site at and at When the designer Aldis Eglais first corresponded with us, he was offering to sell just the plans or the plans plus kit as an alternative to buying and shipping a fully manufactured vessel... don't know if this is still an option.

      Anyway, just some thoughts that may be of use to you.
      [Date/Time=05-04-2002 - 8:27 AM]    Name:Barney C. Black, [Msgid=255279]

    Adding foils to 27-ft catamaram

      Over the years I have seen many mods made to Stiletto Cats. The Stilletto has always seemed to draw out the adventurers in the sailing world due to their High performance and rasonable price. They have very light foam sandwich hulls which might be very difficult to attach foils to, if you can not entirely use the crossbeams.

      I have not seen any Hydrofoil conversions but many other Stilletto projects can be found in back issues of Multihull Magazine, Quincy Mass.

      They have a web site and their owner publisher is very user friendly.

      Best of Luck
      Bill White
      [Date/Time=05-04-2002 - 9:23 PM]    Name:Bill White asst Webmaster, [Msgid=255479]

    PK - A Small Hydrofoil Sailboat
      Dear IHS members,

      Bill White of IHS asked if I would share my experiences in developing and sailing a small sailing hydrofoil. I am happy to do so. Below is a brief account of my 10 year adventure with PK.

      Thanks to my web site (and the International Hydrofoil Society site), I look forward to and receive a lot of e-mails on PK Hydroptère de loisirs (Small Hydrofoil Sailboat. The address of this site changed last month.

      The new address is:
      (Editors note: This is an extensive personal site of sailing hydrofoils)

      PK History:

      I started the design of PK in 1992 and the construction in 1993.

      This boat is exclusively made with some "Recycled materials"! For example the rail of the "rotary bench", is an old bicycle wheel! As a result, I designed and built PK for approximately $800 £.

      PK flew the first time in 1997 without the system for the modification of the incidence and with a classical cat boat sail. When I sail I don't want to have some spectators chuckle (if PK don't fly!) and that's the reason why, I just have bad photos of PK in flight!

      The latest version, (it's the same hull and floats since the start, but I changed all the other parts), has been ready since last summer (July 2001). Unfortunately I have had a problem with my backbone since the same date! As a result, I don't know if I am going to sail soon and I don't have photos of this version on the sea!

      The particular points of this latest version of PK are:
      Rotary bench
      Rigid rig and sailboard sail
      T foils with " incidence control system"
      Rotary floats (to protect the foils)

      Main dimensions:
      Length Overall 5 m
      Length Hull 3.85 m
      Beam 4.8 m
      Sail area 7.5 m2
      Weight 70 Kg
      Built For Only $800.00£!

      Please note that I cannot send the plans of PK, because I am not a naval architect and I think PK is not perfect, it's just a prototype! However, I would be happy to discuss her design and construction over the IHS Bulletin Board.

      Thank you very much

      Best regards
      Frédéric Monsonnec

      I have enclosed different photos of PK at diverse ages below:

      Before the first test of the fifth version in 1997: PK5 Stern-97

      and PK5 Bow view-97:

      Central hull during the first flight in 1997:

      First test of the "incidence control system" in 2000:

      PK6 in my garden last year! :

      [Date/Time=07-04-2002 - 4:22 PM]    Name:Raiola Giancarlo, [Msgid=278825]
      Attached File  "" - size 40357   Click Here To Download

    Kite Sail Possibilities      ViewThread
      Last week I read an article about hydrofoils on yahoo's boomerangtalk... Besides building rangs I like driving my kitebuggy. Unfortunately the beaches here are small, but.... with a lake nearby, such an article and an interest in foils....... ;-). Modern powerkites are very efficient sails with some great advantages over
      normal sails. I wonder if one could power some sort of lightweight 1-seater hydrofoilbuggy. It's obvious though (after finding the IHS-site ;-), that I still have quite some reading to do... Thanks to everyone at the IHS for making that possible ! -- Bart Derks,
      the Netherlands
      [Date/Time=07-12-2002 - 7:57 PM]    Name:Bart Derks, [Msgid=281893]

    Kite Sail Possibilities

    Kite Sail Possibilities

      There is a lot of Kite Board sailing on the Outer Banks at Cape Hatteras where I vacationed a few weeks ago. The boards are short versions of windsurfers boards or more like snow boards.

      If I had the time and was a bit younger I think one could add a set of Hydrofoils to these kite boards and about double the speed. The foils would be similar to the ones that have been adapted for water skiing. There are several on our IHS web site at

      A good example is the sky ski

      Best of luck
      Bill White
      [Date/Time=07-13-2002 - 12:00 AM]    Name:Bill White, [Msgid=281938]

    Windrider Rave Top Speeds      ViewThread
      Very nice website, lots of interesting and useful information! I'm interested in sailing hydrofoils, since I saw a Windrider Rave sailing near Toronto, Canada a few weeks ago. It is a commercially
      available hydrofoil trimaran. I see a lot of articles on your website about sailing hydrofoils, but nothing about the Windrider Rave. Their website is, and The Dutch over here claim a max speed of 41.5 knots, and I read that a French sailor has even gotten to 43 knots with the Rave.

      Another sailing hydrofoil I noticed, is the hydroptere,, and is mentioned on your site.
      [Date/Time=09-14-2002 - 11:27 AM]    Name:Mark-Jan Bastian, [Msgid=309662]

    Built hydrofoil sailboat for only $800

    Windrider Rave Top Speeds

      Thanks for the inputs. We do mention the Windrider Rave model on our Links page at Their web address keeps changing, so we appreciate the input so we can keep it current. The Rave is an exciting boat to see in action, though I have never seen it at the speeds you mention.

      Bill White
      IHS BBS manager
      [Date/Time=09-23-2002 - 7:04 PM]    Name:Bill White, [Msgid=313647]

    Windrider Rave Top Speeds
      Check out: for a whole series of monofoiler sailing hydrofoils. Some sail on just two foils,one on the daggerboard and one on the rudder. Generally, monofoilers won't be as fast as boats like the Rave that develop their own righting moment--but they have tremendous "fun" potential...
      [Date/Time=09-24-2002 - 9:15 AM]    Name:Doug Lord, [Msgid=313860]

    Windrider Rave Top Speeds
      Check out the Hobie Tri-foiler. The Windrider and Tri-foiler are both fast designs, and both similar. But the Hobie has a better control system. The Hobie uses a surface follower system that is very effective. The Windrider uses a system that has it's control input beside the strut instead of in front of it. It requires you to adjust bungee's to keep the foils trimmed. What is the sense in that? It seems to me that the foil control system should do just that, control the foils. There are plenty of other things to keep the pilot busy in a 35+ mph sailboat, without having to keep the foils trimmed. I have heard that there are some people that can successfully tack a Windrider without coming off the foils, but nobody has ever been able to do it in front of me. But I have seen a first-timer tack a Tri-foiler with little difficulty. Either way, both of these boats bring a whole new dimension to sailing.

      Scott Smith
      [Date/Time=09-24-2002 - 10:37 AM]    Name:Scott Smith, [Msgid=313899]

    Windrider Rave Top Speeds
      Hi Scott,

      The Hobie Tri-foiler certainly has a neat and simple foil control system, but the 'wand' approach used on the 'Rave' also seems to work well. From what I have read about sailing the Rave, it should not be necessary to manually control the foils to keep the boat flying in a stable manner. There is however a capability to control the foils manually if that is what the crew want to do.

      Christopher Hook, who first developed a workable fully submerged hydrofoil craft, employed manual surface skimming attitude sensors that projected far forward of the bow foils. Apart from looking somewhat ungainly, these would undoubtedly have been subject to a fair bit of damage in service, even if just bumping into a wharf occasionally. I have often wondered whether it is really necessary for such mechanical surface sensors to actually project far forward of the foils. The Rave seems to demonstrate well enough that this isn't necessary as it runs well in waves while foilborne. For small waves that are typically short, it is not necessary for the hydrofoil craft to react to them by rising up, rather it can just continue through them straight and level. Having a foil sensor far forward is therefore no advantage in that case. For long waves relative to the boat it does not matter much whether they are detected directly in line with the foils or one or two metres in front of the foils as the wave elevation will not be very different between those locations. It would therefore only be for waves that are around the length of the boat that the position of the surface sensors would have a noticeable effect on the motion of the craft.

      A question someone may be able to answer: For large electronically controlled fully submerged hydrofoils like the Boeing Jetfoil and PHM that could happily cruise in large waves at 40+ knots, how far ahead of the boat did the bow mounted surface sensor actually look to detect oncoming waves? How did the signal from that sensor get coupled with the signals from all the accelerometers mounted around the boat that were also used to achieve a smooth ride?

      By the way, there is some nice footage in the video by Arcadia Entertainment "Hydrofoils - Flying on water" that shows a Rave doing a 180+ degree turn (downwind) in the blink of an eye, and remaining foilborne for a good portion of that evolution. Given that can be done, tacking the Rave while remaining foilborne would seem straightforward.
      [Date/Time=09-26-2002 - 7:41 AM]    Name:Martin Grimm, [Msgid=315018]

    Windrider Rave Top Speeds
      There is much truth to what you say, but don't get sailboat dynamics confused with powerboat dynamics, and scale means a lot as well. A Boeing Jetfoil is a big, long boat. The length of the boat, coupled with it's weight, means that it pitches forward and back comparitively slowly compared to a smaller boat. So the inputs to the control system require a slower rate than for a small boat. It's the difference between balancing a broom on your finger and balancing a pencil. For most foil powerboats, the best ride is achieved when there is little control input from waves (fast rate input), and most input is from the height above surface sensor (slow rate input). Basically, fly it straight, compensate slowly for altitude and large, slow swells, and the smaller waves will pretty much take care of themselves. Grumman demonstrated this with a variant on their foilboat that used submerged foils. The control system was actually mounted directly to the trailing edge flap of the front foil. The system worked well. Also, powered foilboats don't have to continuously deal with large side to side forces, except while turning. It gets different for sailboats like the Windrider and Tri-foiler, however. The foils aren't just compensating for altitude, they also have to control heeling forces (left & right) and pitching forces (front & back). In variable winds, the forces acting on the sail(s) can be very high, then a split second later drop to nothing as the wind dies, or worse, changes directions. On a powerboat, the thrust line doesn't change, so the distribution of weight among the foils is predictable. Not so with a small sailboat. As I recall, the sensor on the Windrider is spring-loaded towards the down position with a bungee strectched across to the cockpit. While on a reach, you adjust the tension on the bungee until the foil rides at the proper height. If you change direction, or if the wind changes, you have to re-trim the sensor tension to keep the boat stable. This may be why they show a downwind tack in the video. There is only a momentary loss of power, and the pilot doesn't have a large burden to keep the boat up. Tacking upwind is trickier, as the powerloss can be longer and have more effect on the foilboat's trim. But the real proof is in the pudding. I have seen an amateur tack a Tri-foiler in moderate wind, with no apparent trouble. I have yet to see anyone tack a Windrider in any wind, with any pilot. If someone out there has a video of that, I would love to see it. The Windrider seems to have a growing popularity lately. It is a little cheaper, but is there another reason for this? Maybe it can do some things I am not aware of. If anyone out there has had any real experience with both the Tri-foiler and the Windrider, I would love to hear it. Maybe I'll even apologize and shut up :)

      Scott Smith
      [Date/Time=09-26-2002 - 8:38 AM]    Name:Scott Smith, [Msgid=315058]

    Windrider Rave Top Speeds
      As for the height sensors they where mounted looking directly down at the water. The ACS control system was set up to maintain a constant 1 "g" force on the deck via accelerometers and gyro's. The Hull mounted accelerometers where located on the PHM at the to rear struts and the forward one was mounted just aft of the forward strut. The accelerometers dampen out the effects of the height sensors seeing chop by clamping the signal to the hydraulic systems.
      [Date/Time=09-28-2002 - 11:30 AM]    Name:"Jake" Jakobson, [Msgid=316107]

    Windrider Rave Top Speeds

      Thanks for your reply. I follow what you are saying about the dynamics of sailboats and the effect of the scale on the motions of a craft.

      Just reinforcing your point about scale, for a case where all proportions of a boat and the waves it is travelling in are scaled down and if the speed of the boat is also "Froude Number" scaled, the time period in which successive waves are encountered is reduced by a factor of the square root of the ratio of model to full size length. For example, a 1:20 scale model of a hydrofoil boat will encounter the corresponding "1:20 scale" waves in only 22% of the time of its full size counterpart, or around 4.5 times faster.

      Although there is an agent for the sale of the Windrider Rave in Australia, I have not seen any first hand. I have not seen any Trifoilers either so I can't comment about their relative characteristics!
      [Date/Time=09-28-2002 - 9:12 PM]    Name:Martin Grimm, [Msgid=316268]

    Windrider Rave Top Speeds

      Thanks for that straightforward response to my question. It beats trying to find that out by tracking down and then reading through long and complex technical papers!
      [Date/Time=09-28-2002 - 9:16 PM]    Name:Martin Grimm, [Msgid=316270]

    First sailing Bi-foiler

    First sailing Bi-foiler
      Dr. Ward ,it looks like you have done a tremendous job! Check out for other monofoiler's such as Brett Burvills Moth sailing on just two foils(one on the daggerboard and one on the rudder).And recently ,John Ilett's monofoiler sailing the same way but with an addition of a wand based altitude control system. Also included on the site are pictures of David Lugg's International 14 sailing on just two foils with manual control.
      If you would like I'll be more than happy to add your boat to the others on
      When did you first sail your boat on two foils?
      Congratulations on a great job! Doug Lord
      [Date/Time=11-11-2002 - 8:19 AM]    Name:Doug Lord, [Msgid=336328]

    Catri Hydrofoil in Guaraní and Tupi
      With regard to the glossary of hydrofoil-related terms at, There was no word for "Hydrofoil" in South America's main native languages, the Guarani and Tupi, BUT both languages use the same word for "Water" ("Y" or "I") as well as the same word for "Wing" ("Pepó").

      Also, adding words is a valid resource in both languages, exactly as in Latin or Greek. For example: "pepó" is derived from "pe" + "pó" = "flat" + "hand".

      As a consequence, the word "Hydrofoil" can be translated directly into "Y'pepó" and the meaning is clear in the course of normal conversation. The roots were double checked in three different Guarani dictionaries and two Tupi dictionaries and the correctness of the composed word was verified with many Guarani speakers, among them two teachers of the language.

      I searched for this word while trying to find ideas to name my future hydrofoil assisted folding trimaran model "Catri 27R" designed by Mr. Aldis Eglajs, from Latvia. By the way, I found and read his text in your website before my first contact with him and now the boat will be the first of a serial production in Brazil. I shall name it "Y'pepó" if my wife and daughter allow me...

      [Date/Time=11-24-2002 - 9:15 AM]    Name:Luiz Schechter, [Msgid=342713]

    Hydrofoil Voyager E-Book
      The late Dave Keiper's book Hydrofoil Voyager, which tells the story of designing and building the hydrofoil WILLIWAW and sailing her solo across the Pacific Ocean, is a terrific book... a mixture of adventure story and "how-to" book. You can read the full review of this by the IHS newsletter at

      Unfortunately, Dave Keiper died and the book has gone out of print, along with the companion videotape of WILLIWAW. IHS first attempted to interest some publishers in the idea of reprinting this book commercially, but was unsuccessful. Then, IHS had the idea to create an E-Book version with clips from the video to be offered at cost on CD-ROM. We even went so far as to scan the book into Adobe Acrobat with bookmarks, internal hot links, and full optical character conversion. In fact, the remnants of Dave's website as preserved by his brother Frank state (incorrectly) that the eBook is available (see Unfortunately however, we were not able in the end to get unanimous consent to offer the book in this fashion without remuneration to the heirs.

      Meanwhile, this excellent book remains unavailable to the public; I have not seen even one copy go up for auction on eBay over the years since Dave died. Attention is shifting inexorably away from Dave's legacy in the hydrofoil sailboat field to focus on currently active efforts such as the racing Moth Class experiments with foils and the Catri sailboats designed by Aldis Eglajs. At one point, IHS member Tom Speer was planning a follow-on to WILLIWAW (see but I do not know the current status of this idea; the site was last updated in 2001.

      The key to getting permission to reprint the book is to interest a commercial publisher or other company to do so in a way that would benefit the heirs financially. IHS was not able to do this, but we certainly did not exhaust all possibilities. Perhaps someone else would be willing to tackle this.
      [Date/Time=12-03-2002 - 6:25 PM]    Name:Barney C Black, [Msgid=346383]

    A Light, Cheap Foiler Dinghy      ViewThread
      Bi-foiler and small dinghy foiler development is happening quite fast at present by a few keen amateurs, I am sure there is a long way to go and we need a breakthrough... in the same way that Sailboards developed (It seems amazing to me that the Sailboard has proven to be such a breakthrough in efficiency compared with all other sailing craft, and yet it was never "designed" as such, it developed simply by empirical testing and in most cases the ideas of amateurs... where were the Mechanical engineers, Physicists, Mathematicians, Hydrodynamicists and Naval architects when this breakthrough in design was developed?).

      We seem to have an amazing resource of such talent within the IHS ranks, and I am sure we could together pro-actively design a better Moth based on hydrofoils and come up with a really good, simple, light and cheap foiler dinghy for everyone to enjoy!

      It would be good if IHS would sponsor a special development discussion section on the website, where perhaps some other members or interested parties may be able to contribute answers and ideas to many of the questions that I have. For example:

      Why can't I sail foilbourne upwind in under 15kts of wind, how to fix this?
      Is semi foiling upwind faster than displacement sailing?
      Would a foiled bow rudder work?
      How to maintain control at high speed?
      Why can't I sail foilbourne upwind in under 15kts of wind, how to fix this?
      [Date/Time=01-04-2003 - 3:07 PM]    Name:Ian Ward, [Msgid=358650]

    Re; A Light, Cheap Foiler Dinghy
      As a controls guy, I believe that we underestimated the human's ability to stabilize a sailboard. Forty years ago in 'The 40 knot sailboat', Bernard Smith ( predicted that the ultimate sailboat would have only a single foil in the water, but he didn't imagine that guys could actually balance on their rudder/foil! The same thing goes for the hydrofoil 'air chair', for the first few tries it seems impossible. People are slow, but within the constraints of our 'neuromuscular lags', we are amazing adaptive controllers.
      [Date/Time=01-05-2003 - 2:59 PM]    Name:jim hynes, [Msgid=358944]

    Builder of Catri 27 Hydrofoil Sailboat
      We have a boatyard in Brazil that manufactures a sailing trimaran with hydrofoils that flies, the Catri 27. Please visit Currently the site is only in Portuguese but in a couple of months it will be also in English. If you want more info please contact me!

      [Date/Time=01-06-2003 - 8:10 AM]    Name:Dr. Raul Díaz Langou, [Msgid=359235]

    Re; Re; A Light, Cheap Foiler Dinghy

      You have made a nice observation. I tend to find it hard to understand how hydrofoils with such apparent little transverse stability as the current series of fully submerged sailboats with only centreline foils can be operated, yet Ian and others have shown it can be done! That doesn't only apply to these sailboats and the air chair water skis that you also mentioned, but also solar powered one-man hydrofoils, pedal powered hydrofoils and now even hydrofoil surfboards!

      For those with a really technical bent, the mathematical modelling of the human operator using skilful body weight shift to maintain stability of a solar powered hydrofoil has been examined in the following reference:

      Terao, Yutaka; "Lateral and Roll-Yaw Coupled Motion Control of Hydrofoil Craft", Proceedings of the 7th International Conference on Stability of Ships and Ocean Vehicles (STAB 2000), 7-11 February 2000, Launceston, Tasmania, Australia. AMECRC Ltd, Editor: Martin Renilson. pp 542 - 550.

      For me, I just prefer to see these spectacular craft running foilborne. The Arcadia Entertainment "Hydrofoils - Flying on Water" video shows some good footage of such solar and human powered craft and air chair water skis in action.

      [Date/Time=01-07-2003 - 12:41 AM]    Name:Martin Grimm, [Msgid=359572]

    Where to get old books, mags
      A large listing of popular books and magazines dealing with hydrofoils is featured on the IHS website at Unfortunately, IHS is not a source for most of these documents. To obtain copies, Try local libraries, used book stores and antique shops. Local libraries may have access to the book or magazine you want through inter-library loan even if the particular branch does not have it. Most bookstores, including the chain bookstores like Borders have access to a service that locates out of print books. Also try the on-line auction services at Ebay,, and Yahoo... particularly Ebay. Sooner or later, just about everything shows up for sale on Ebay or its companion site allows you to "preorder" a used copy of any book in its massive listing (though Bernard Smith's book is not listed).
      [Date/Time=01-09-2003 - 1:23 PM]    Name:Barney C Black, [Msgid=360565]

    Cat Needs Better Motion Into Chop      ViewThread
      I own a 38 foot racer cruiser sailing catamaran in Puerto Rico. I have changed the motor arrangement to get better speed while motoring, and can now motor at 14 knots in flat water.

      I am interested in adding fins to the sterns of the catamaran, to help
      reduce pitching while sailing and motoring into chop. My question is, can you recomend a person or company that could help me evaluate the possibility of adding fins to my cat to help give it a better motion while moving through chop/ waves?

      As you can imagine this is a recreational sailboat, and I would only add fins to my cat if it is something that I can do economically (they would be fixed fins).

      [Date/Time=01-24-2003 - 1:59 PM]    Name:Tony Amador, [Msgid=366530]

    Re; Cat Needs Better Motion Into Chop
      My experience on sailing cats is limited to having sailed a Prout 45 from Bermuda to Annapolis. My experience was that the boat pitched uncomfortably while beating and the worst (most extreme) motion was forward; aft there was considerably less motion and it was far more comfortable aft. If your boat behaves in the same manner, I think adding fins aft would gain you very little. At least one of the power cats at the Annapolis power boat show had bulbous bows to reduce pitching.
      [Date/Time=01-25-2003 - 6:26 PM]    Name:Michael W. Preis, [Msgid=367041]

    Re; Cat Needs Better Motion Into Chop
      Paul Bieker (photo below) has designed these kinds of foils for International 14's. He's a Naval Architect in Seattle. His email:

      [Date/Time=01-26-2003 - 8:21 AM]    Name:Tom Speer, [Msgid=367269]

    Re; Cat Needs Better Motion Into Chop

      I tend to agree with Michael. If you want to reduce pitching motions, it would probably be better to add an anti-pitching fin or fins as close as possible to the bow of your boat.

      The Royal Australian Navy fitted an anti-pitching fin to the bow of its mine hunter catamarans and this seems to have been beneficial in reducing pitching motions. The fin spanned the entire gap between one hull and the other. These craft had a speed of about 8 knots but would have had a displacement significantly greater than your own boat.

      Unless the fins are particularly well designed, you should anticipate some speed loss due to the additional drag that they will create. Also, there is a possibility that in some sea conditions, such as in following seas, the pitching motions may become worse if the fins are purely passive.
      [Date/Time=01-26-2003 - 8:52 AM]    Name:Martin Grimm, [Msgid=367276]

    Volantis      ViewThread
      Does any one know of the sailing hydrofoil Volantis? I've heard it is being built in Hawaii by the designer of the Rave Windrider.
      [Date/Time=01-28-2003 - 7:51 PM]    Name:Byron Wallin, [Msgid=368609]

    Re; Volantis
      You can find citations of magazine articles as well as archived correspondence on the subject of Volantis by using the search engine at the bottom of our main page at Just enter the word Volantis and click search.
      [Date/Time=01-29-2003 - 9:57 PM]    Name:Barney C. Black, [Msgid=369337]

    Re; Volantis
      Dr. Sam Bradfield has been a consultant on the project. However, it's not under construction yet. I believe they are still trying to raise money for it and refine the mission requirements. Unlike most sailing hydrofoils, this one is eventually intended to be unmanned.
      [Date/Time=02-04-2003 - 1:46 AM]    Name:Tom Speer, [Msgid=371849]

    Re;Cat Needs Better Motion Into Chop
      The problem with fins at the bow is that one of the requirements of a sailing catamaran is that it resist pitchpoling (capsize forward or diagonally). A fin at the bow can go to a negative angle of attack, pulling the bow down and contributing to dangerous situation. So a fixed fin at the bow is probably not a good idea. This leads to adding a control system, and before you know it you've got a full-blown hydrofoil stabilizer development project. Not that there isn't merit in that. But a fin at the stern will contribute to stability as well as damping, although the damping is less than if it were at the bow.

      As far as I know the HYSUCAT approach hasn't been applied to sailing catamarans yet. Maybe a foil stretching between the sterns?
      [Date/Time=02-08-2003 - 2:46 PM]    Name:Tom Speer, [Msgid=374632]


      My name is Gérard Delerm (I am french)
      I already show my home page about "Le Foilboard" on the IHS site.
      It is a sailboard with hydrofoils project.

      There are now somes updates in the english version (link NEWS on the contents page).

      [Date/Time=02-10-2003 - 9:00 AM]    Name:Gérard Delerm, [Msgid=375459]

    IHS members in So Cal      ViewThread
      Is there anyone here from southern California working on hydrofoil sailboat designs? I would be interested in learning about your projects.
      [Date/Time=03-15-2003 - 2:31 AM]    Name:Steve Salani, [Msgid=396535]

    SLO Foils
      hey hey - I´m in San Luis Obispo. I don`t have anything to look at, but would love to hear what else is going on. Where are you/have you heard from anyone?
      [Date/Time=03-19-2003 - 5:21 PM]    Name:Henry, [Msgid=399556]

    hydrofoils? on a sailing cat      ViewThread
      I have a 7 meter sailing catamaran that I use in the Indian Ocean off the coast of Kenya. Its an older (20 years?) Italian boat designed more for use on lakes than open ocean. Its bows are sharp and narrow making them very sensitive to weight up front. In larger waves they will tend to dig in, making water wash over the bows, of course making them dig in further. I would like to make the bows more bouyant. One way I have been considering is the addition of a couple of "hydrofoils" just below the waterline on each side of each hull. I envision small wings 2 or 3 inches wide and perhaps a foot or 18 inches long fibreglassed onto the side of the hulls with an angle that causes the water to push up on the bows as they move through the water.

      I figure that at 8 to 10 knots I would like to get around 3-400 pounds of lift TOTAL from all four hydrofoils. This would allow a couple of people to ride forward on the cat without hurting performance and would keep the bows up when maneuvering in wind and waves.

      I have no idea if this is a practical solution to this problem. If it is I have no idea of the actual size of the hydrofoils. So I am soliciting ideas from those who know much more than myself about this sort of thing to try and lead me to a reasonable decision as to whether or not I should try this.
      [Date/Time=05-26-2003 - 8:24 AM]    Name:Paul Cowles, [Msgid=441573]

    Re; hydrofoils? on a sailing cat      ViewThread
      I'm adding to my question slightly. I see by looking over the site I am actually talking about adding 'fins' rather than hydrofoils. The idea is the same though to 'lighten' the bows when I am underway. Cheers.
      [Date/Time=05-26-2003 - 8:56 AM]    Name:Paul Cowles, [Msgid=441586]

    Re; hydrofoils? on a sailing cat
      In the late 60's this was tried on many cats. The main problem is that if you are hit by a gust and bury the bow below the angle of attack of the fixed foils on the bow, then you can have some very embarrasing cartwheels. Angle the foils too high to prevent this and all you do is slow the boat rather than give lift.

      I think the best answer is to use pivoting foils, with a sensor. This way you can always get optimum lift. If you are adventureous the HYSUCAT idea may also be a winner. see

      An alternative is to put T foils on the rudders to reduce pitching and diving. This works quite well, involves no moving parts and is simple to add.

      [Date/Time=05-26-2003 - 11:23 PM]    Name:Ian Ward, [Msgid=441941]

    re; Foils on Sailing cat

    Want a ride on Hydrofoil      ViewThread
      I have been studying HYDROFOIL designs, and think I have "nailed" it. Now need to ride on someone's craft. I live in South Florida but am willing to go anywhere in NA for an extended ride. Any one have an operating Hydrofoil Boat who can accomodate my request?
      [Date/Time=06-03-2003 - 7:32 AM]    Name:Gerry Levine, [Msgid=446222]

    Re; Want a ride on Hydrofoil
      I live in Miami. If you are looking for a ride on a hydrofoil sailboat, there is a place here that rents windriders. Drop me a line and I'll look it up for you.
      [Date/Time=06-05-2003 - 6:41 AM]    Name:Scott Smith, [Msgid=447375]

    New Hydrofoil Sailboard Design Info      ViewThread
      For those interested in the design and operation of hydrofoil sailboards, Rich Miller has created a 28-page photo-illustrated technical paper on the design, construction, and sailing of his hydrofoil sailboard. Look for the link to this document near the top of the page at
      [Date/Time=06-15-2003 - 6:36 AM]    Name:Barney C Black, [Msgid=452969]


    First Unifoiler Scow Moth      ViewThread
      I would like to share some ideas and experience....

      I have recently modified an old non-winged scow Moth hull, placed a single foil on the centreboard and a retractable surface running foil at the bow. No rudder T foil at all. Total cost of materials to make the foils is about $200, even less if you simply modify your existing centreboard!.

      I took it out last Sunday and got it up and going in about 10-12 kts of wind. There are many things to improve yet, but in principle it all works fine, no capsizes and some good bursts of speed on reaches!. It is really amazing to realize it is possible to sail with only ONE foil in the water!.

      The principle is not new, Rich Miller has a sailboard already doing fantastic speeds up to perhaps 35 kts with a similar arrangement. This is just the first application to dinghies. There is a long way to go yet, but 35kt Moth is a real possibility

      This means it is possible to use existing, old boats and adapt them to foils. I see no need for a new range of specialist hulls just for foiling. In fact some of the older and more stable hulls may perform even better as they are still good in light winds. It is also relatively cheap to make the necessary modifications. The boat is launched in the same way as a normal dinghy. In conclusion, it is indeed possible to have a low cost, high speed, easy to handle foiler suitable for begginers and speed demons alike.

      In my opinon, most of the fears about foiling in sailing circles comes from not being able to imagine what is possible, not actually having a go and even worse, doing nothing to actively develop a solution! Some of those who looked at the original Brett Burville trifoil Moth contraption were horrified at its ungainly, impractical but fast foils and immediately wanted to ban these from the Moth class.

      It is only with imagination and some real drive from the Isletts, Rich Miller etc that we have made real progress, and I am sure there is a lot more to come in terms of simplification, speed, handling and low cost! There is only one way to find out, I encourage all of you to give it a go and develop your own solutions!

      I believe the International Moth class should be proud to be the only International sailing class currently prepared to allow foil development.
      Without such an open forum, Moths would have remained Scows and foiler development would have ceased at Trifoilers.

      In the long run I am sure Moths and all future sailing classes will benefit.
      [Date/Time=11-10-2003 - 9:39 PM]    Name:Ian Ward, [Msgid=541387]

    Historic First Nationals on Foils!      ViewThread
      Just want to let those know that don't that Rohan Veal of the Moth Class has an unsurmontable lead in the Australian Moth Nationals. He is sailing a Moth on hydrofoils! This is the first time in history that a hydrofoil equipped boat has won a Nationals using foils; it is one of the first times that a hydrofol equipped boat has won any major race series. It is clearly a dramatic step forward for hydrofoils and sailing in general!
      He has won five races against 30 plus boats by leads of three to nine minutes. In the race he won by nine minutes second place was also a hydrofoil!
      Rohans boat sails on just two foils: one on the daggerboard and one on the rudder. Altitude control is by use of a "wand" system. Stability is provided
      entirely by the crew. The boat and foils were built by John Ilett of Perth Western Australia and he deserves congratulations as well.
      Way to go Rohan!
      [Date/Time=01-03-2004 - 8:35 AM]    Name:Doug Lord, [Msgid=566079]

    Want to know more?
      Thanks again Doug, series is just finished. Of the ten heats, Rohan had 8 wins ,3rd and 4th. The 3rd and 4th are dropped races for the points tally so it was a cleen sweep. His top speed by on board GPS was just over 20 knots. For those that wish to see more here are some links. and
      [Date/Time=01-03-2004 - 9:43 PM]    Name:John Ilett, [Msgid=566365]

    hull choices      ViewThread
      ive sailed moths for a while and am considering a new hull for foiling, i only have one question:

      does a planing hull beat a displacement hull to 10 kts boat speed in lighter wind conditions.

      what im trying to acheive is lift off in a wind range between 5 - 10 kts and after that i would like a low aerodynamic drag hull. im thinking of something similar to a formula sailboard for its planing but am concerned about the wetted surface area as opposed to a displacement hull similar to a rowing skull. although i only have 11 feet of LOA (width currently runs around 1ft)

      ps: consider the weight of each hull to be the same.
      [Date/Time=02-04-2004 - 10:38 AM]    Name:glen oldfield, [Msgid=583861]

    Re; hull choices

      If you were considering a larger boat, say one carrying several people, then the answer would definitely be that a slender displacement hull would have less resistance at 10 knots. If on the other hand you are looking at something as small and light weight as a Moth, then it is harder to clearly identify the best option as there will be a transition of least resistance from the displacement hull to the planing hull at a speed around what you are interested in.

      In the Moth size range, the best performing boats these days seem to be the very slender displacement types. In higher wind speeds it could be expected that a planing hullform should give lower resistance. Of course by that stage, if foils are fitted, the hull should be clear of the water under those conditions anyway!

      [Date/Time=02-14-2004 - 9:19 AM]    Name:Martin Grimm, [Msgid=596593]

    Speed race in Douarnenez (France)      ViewThread
      we're organizing a speed race over in Douarnenez (France). Different categories are invited to run : windsurfers, kitesurfers, multiholls 60 feet and hydrofoils[/b. I'll give you more information next time but for now, could you please give me some contacts of people eventually interested by that kind of races ?
      Waiting for your answer,
      Thank you,
      Anne Raffray
      Société des Régates de Douarnenez
      57 quai de l'yser
      29100 DOUARNENEZ (phone) (fax)
      [Date/Time=05-26-2004 - 11:32 AM]    Name:Anne Raffray, [Msgid=654338]

View Messages Search Messages Return to Home Page Frequently Asked Questions
This board has been viewed 21682 times since Apr-20-2002 .
(Total Views Since Board Creation on Mar-21-2002 is 22416.)

Questions about this board, email:
System Support, Email:

To Learn About Bulletin Boards:  Click Here
Bulletin Board Management Site: Click Here

(321) 984-9080
© 1997 - 2004 P.A. Corp. V7.1