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The International Hydrofoil Society (IHS) Hydrofoil Message: Chats, Info Sharing, Networking
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Archived Messages
Count,MessageID,category,ShortTitle,Message,Date,UserName,MsgPswd,Phone,Email,ParentMsgId
“1”,”912645″,”3″,”Re; Re; Re; A faster pontoon boat||912645″,”FYI: Several people around the USA are working on adding foils to pontoon boats… hobbyists, not manufacturers. Their correspondence with IHS is archived and accessible. Go to the main IHS page at www.foils.org and use the PicoSearch Engine to look for the word “pontoon.” That will lead you to several citations.”,”2005-10-12″,”Barney C Black”,”poopdeck”,” “,” “,”911944”
“2”,”911944″,”3″,”Re; Re; A faster pontoon boat||911944″,”There’s a company in Canada www.u-fabboats.com that I have shared what I learnedand are planning to offer a foil kit on there pontoon boats. It will be a hydro-foil assisted with a fixed foil in the tunnel. Which will reduce wetted surface I guess thats what it’s all about? I been playing around with a fixed foil and have had much luck with it I was focusing on slow speed. 12 mph and she’s on a plane and thats at gross weight I am planing a motorsailing cat around this concept.”,”2005-10-12″,”Mike”,”nopswd”,” “,”info@buildboats.info”,”888662″
“3”,”888662″,”3″,”Re; A faster pontoon boat||888662″,”I have thought about this as well. Trick is, don’t get too high out of the water. It is tempting to want to run the hull 3 feet out of the water to skim through wakes, but a sudden drop will be more than the hull was designed for. Lifting the hull 10 inches will give you speed and fuel economy, with less structural risk. Raising and lowering an outboard is a great way to accomplish powering the boat. I would be concerned about what will happen when the foils hit something (and they will). A front foil centered between the hulls could pivot back up between the hulls. The rear foil or foils could be fixed to the structure behind the hulls, and pivot up when trailering or running shallow. The trick (as I have learned from my dynafoils) is to have the rear strut mounted so that the foil is in front of the pivot point. That is, the rear strut(s) would go from the pivot point at an angle, the bottom of the strut forward of the top of the strut. Helps keep weeds off too. Why is this important? If the rear strut is vertical and operates on a pivot, after striking debris the strut would begin to pivot backwards. As it does the foils angle of attack changes. At some point in the travel the foil will be perpendicular to the drag load placed on it and it will not rotate up out of the water. Kiss your transom goodbye, keep pliers handy to pull your teeth out of the dashboard. If the foil is forward of the pivot things change. The foil will become perpendicular to the direction of travel while still well below the axis point. By the time the strut rotates far enough to line the center of drag up with the centerline of the structure, the foil is now operating backwards with positive lift. This forces the strut to continue rotating up and out of the water, saving you a lot of pain.
If you would like to take a look at the dynafoil system, or just talk, feel free to drop me a line. I just moved up from Miami to Stuart. By the way, a lot of talk goes into how to control roll in hydrofoils. While this is a concern with ships, I am convinced it is far less complicated with smaller boats. If you have ever ridden a bicycle I’m sure you have learned that you already have the ability to overcome roll issues with steering. After a while you don’t even realize you are doing it.”,”2005-09-05″,”Scott Smith”,”nopswd”,” “,”boatswithwings@adelphia.net”,”3″
“4”,”853019″,”3″,”Re; Re; A faster pontoon boat||853019″,”Good luck with your project. Hope this helps.
Bob’s Machine Shop make the motor lifting plates you need. You can find them at.
Several catamaran builders and designers make the keel mounted foils systems you are talking about. See for instance the Hysucat Hydrofoil System.
http://admin.sun.ac.za/kie/unistel/technologies/foiltech.htm”,”2005-06-29″,”william white”,”nopswd”,” “,”whitewn@speakeasy.net”,”0″
“5”,”852923″,”3″,”Re; A faster pontoon boat||852923″,”I’ve been fighting that problem for some time. The easiest technique would be to jack the outboard motor up/down with spring-loaded and hydraulic jackplate. The rear foil which fits between the tubes, would move with the motor. A similar arrangement for the bow. If you allow the tubes to just skim the water that will keep the boat more stable. Make sure that going aground won’t be catastrophic. I’d love to find someone “local” to work with on my pontoon project. barry_steele@yahoo.com”,”2005-06-29″,”Barry Steele”,”nopswd”,” “,” “,”0”
“6”,”852922″,”3″,”Re; A faster pontoon boat||852922″,”I’ve been fighting that problem for some time. The easiest technique would be to jack the outboard motor up/down with spring-loaded and hydraulic jackplate. The rear foil which fits between the tubes, would move with the motor. A similar arrangement for the bow. If you allow the tubes to just skim the water that will keep the boat more stable. Make sure that going aground won’t be catastrophic. I’d love to find someone “local” to work with on my pontoon project. barry_steele@yahoo.com”,”2005-06-29″,”Barry Steele”,”nopswd”,” “,” “,”0”
“7”,”852376″,”3″,”A faster pontoon boat||852376″,”Living in Florida I spend a lot of my time on the water and most of it in the shallows. Pontoon boats offer the best way to take the party with me, slowly. A pontoon with retractable foils would be the best of both worlds. Any body out there tried this? I have given this a great deal of thought and have many ideas how to achieve this but expert advice is always welcome. Any advice where to look for info besides this excellent website would be greatly appreciated. Opinions on this would be welcomed aswell. “,”2005-06-28″,”Brian Scott”,”nopswd”,” “,”brian.scott.ctr@hurlburt.af.mil”,”0″
“8”,”792474″,”3″,”TUCUMCARI||792474″,”Hello,
For the past 26 years I have served as a project supervisor creating museum exhibits in honor of U.S. vets and those of our allies. Some of the venues I have done work for include the USS Intrepid Sea Air Space Museum and the Museum of Polish Military Heritage in America, both in New York City. Load my name Mike Dobrzelecki into a Google Search Engine and you’ll see examples of some of my work on two continents over the years.
I saw your name & email on the IHS website and hope you can provide some help on a research project concerning the Tucumcari PGH-2.
I built the old Aurora kit when it first came out in the late 1960’s early 1970’s (?) and not too long ago picked up a derelict unpainted damaged built-up, as well as a pristine complete kit still in the original box. I even still have some parts from my original build model.
My intent is to build one ‘flying’ and one in the water with its struts and foils folded up and possibly write a good article on the Tucumcari.
I have everything available on the internet for this fascinating hydrofoil, as well as, the old Sea Clasics issue with the Tucumcari on the cover. Recently, I obtained a copy of the History Channel Mail Call episode with the world’s most famous D.I. narrating exquisite video of the this fast-fighting boat in action – great footage, BTW. I have even manage to track down some of its crew for personal interviews. Most frustratingly, the crew I talked to so far all stated that their photos went missing during moves over the years.
I am looking for more photos including details of the interior, the exterior fit on the cockpit/bridge and upper surface of the hull and an answer to what’s in the large opening aft of the .50 cals and masts/antennae. I would also like to track down some more crew and any other books or naval history magazine articles on the the Tucumcari. Any leads would be appreciated.
Mike Dobrzelecki
3040 Clayton Street
Easton PA 18045
“,”2005-03-07”,”Mike Dobrzelecki “,”members”,” “,”Michael_Dobrzelecki@fwc.com”,”0″
“9”,”737553″,”3″,”Foil or Log?||737553″,”I don’t know what calculator you’re using, but if it’s telling you you can get good results from a section with a 50% thickness ratio and 25% “profile curvature” (camber?), I think you need to get a new calculator. These numbers sound like your foil section is a half-circle. Might there be just a little bit of flow separation coming off such a shape? “,”2004-11-13″,”Tom Speer”,”nopswd”,” “,”me@tspeer.com”,”0″
“10”,”737001″,”3″,”Hydrofoil Design Validation||737001″,”I downloaded a hydrofoil simulation calculator and wanted to verify the results I am getting.
Can someone tell me if the following numbers are accurate? I am trying to get the highest amount of lift I can for a constant water velocity over hydrofoil of 20m/sec or 38.9Knots. I am also trying to keep the foil span as short as possible.
Here are the input numbers:
Foil Area Square Meters: 1 Sq M (1M span X 1M chord)
Speed M/sec: 20 M/sec
density of water kg/m^3: 1000
thickness of foil divided by chord: 0.5
Aspect ratio (Foil span/chord): 1 “This is a square foil I know”
Angle of attack: 14.32 degrees
Profile Curvature: 0.25
The calculation is claiming that the hydrofoil would produce 53690 pounds of lift with these numbers. I need to make sure this is true and also that the wing is not in a stalled state on these numbers.
Greatly appreciated. Sidenote: Would anything change if I put a rectangular ducting around the hyrdrofoil? I know in airfoils and fans, the ducting produces more volume of airflow.
BE”,”2004-11-12″,”Foiled Again”,”nopswd”,” “,”mirequest@yahoo.com”,”0″
“11”,”732177″,”3″,”Re: planing hull seakeeping||732177″,”I don’t have a copy of these articles, but I would suggest contacting the Davidson Laboratory via their web page at:
http://www.stevens.edu/engineering/cms/
“,”2004-11-03″,”Barney C Black”,”poopdeck”,” “,”barney@alum.mit.edu”,”0″
“12”,”722280″,”3″,”planing hull seakeeping||722280″,”I am looking for copies of Gerard Fridsma’s two publications:
Fridsma, G., “A Systematic Study of the Rough-Water Performance of Planing Boats,”Davidson Laboratory, Stevens Institute of Technology Report 1275, Nov. 1969.
Fridsma, G., “A Systematic Study of the Rough-Water Performance of Planing Boats – Irregular Waves Part II,”Davidson Laboratory, Stevens Institute of Technology Report 1495, March. 1971.
Can anybody supply me with copies of these?”,”2004-10-12″,”Gunther Migeotte “,”nopswd”,” “,”gunther@cae.co.za”,”0″
“13”,”699947″,”3″,”Re: Engine Torque||699947″,”I have several small hydrofoils, probably similar to what you are trying to do. They are called Dynafoils (a search of the archive will turn up pics for you)and are about 8′ long, similar to a one-person sit-down waverunner. They were available in two HP’s, a 26hp model, and a 36hp model. Neither used a torque convertor. They used 2 cylinder, 2 stroke snowmobile engines, direct coupled to a 90 degree gearbox, to a downshaft with an evinrude outboard lower unit. The 26hp unit used a 9-1/4″ dia. by 7″ pitch prop, the 36hp unit uses a 9×9 prop. My 36hp Dynafoil leaps out of the water pretty well, and does about 35 mph. If you like, I can send you pictures, videos, or you can stop by in Miami and go for a test ride 🙂
If you are considering a 4-stroke, also consider a rev-limiter.”,”2004-08-26″,”Scott Smith”,”nopswd”,” “,”ssmith@syntheon.com”,”0″
“14”,”694448″,”3″,”Re; Re; Re; Engine Torque||694448″,”Barry,
Thank you for the information. What make is the prop…
“,”2004-08-13″,”Philip”,”nopswd”,” “,”kernowii@sympatico.ca”,”0″
“15”,”693009″,”3″,”Re; Re; Engine Torque||693009″,”For my application I have purchased a variable pitch prop for my mercruiser outdrive. The 3 blades to the prop are spring loaded with a lower pitch (around 16) for getting out of the hole and up on the foils. When the engine picks up speed, centrifugal force rotates the blades for up to about 25 pitch. This keeps the engine running within a fairly tight speed range. They are available for outdrives, outboards and inboards.”,”2004-08-11″,”Barry Steele”,”nopswd”,” “,”barry_steele@yahoo.com”,”0″
“16”,”692414″,”3″,”Re; Engine Torque||692414″,”Philip,
I would have expected that torque converters would rarely be required for small craft such as you describe. These devices result in a loss of power between the engine and the propeller and so a more efficient solution would be to select an outboard and propeller combination with an optimum gear ratio and propeller pitch to diameter ratio.
Hydrofoils have a resistance versus speed curve that means they require a relatively high thrust at takeoff speed and after that the resistance curve is more flat. Some larger hydrofoils (such as the Supramar PT 150) therefore had torque convertors of some form fitted to cope with this characteristic such that the engine would not be overloaded during takeoff but would run near optimally at cruise speed. For a smaller hydrofoil, there would typically be a surplus of power across the full speed range, but you may be adopting an outboard with relatively low power output so the takeoff condition may become critical for your boat.
Note that when using gearing in an outboard, the following relationship applies:
Power = (Torque) x (Rotational Speed)
Metric units for this equation are Watts, Nm and rad/s respectively.
Put another way, if you use a reduction ratio of 2:1 then the propeller shaft RPM will be half the engine RPM but the torque available at the propeller will be double that at the engine output shaft (neglecting any losses in the gearing due to friction). You can play with gearbox ratios until you obtain the required torque and RPM combination you need at the propeller. “,”2004-08-10″,”Martin Grimm”,”nopswd”,” “,”seaflite@alphalink.com.au”,”0″
“17”,”687245″,”3″,”Engine Torque||687245″,”I’m currently reviewing a design for a small one-person hydrofoil powered by a 15hp-25hp long shaft outboard. The question of engine torque has arisen and the need for an engine mounted torque converter however; in reading a lot of the design material on these pages (excellent guidance by the way) I have yet to come across this issue being discussed. Is torque a major design consideration on small (<9 feet) hydrofoils?","2004-07-30","Philip","nopswd"," ","kernowii@sympatico.ca","0" Propulsors Arneson Drive For Sale [2 Feb 02] This asd 6 drive is for sale. I think it would be a good drive for a hydrofoil. The drive is like new. Price $1,900. Credit cards OK. -- Fred Rodolf (FREDRODOLF@aol.com) [Date/Time=03-23-2002 - 12:33 AM] Name:webmaster@foils.org [Msgid=237120] Safety Safety Rules [2 Sep 97] I read in the Summer '97 issue of the IHS Newsletter about the American Bureau of Shipping (ABS) rules for high speed craft and will order a set. Do you know if there is a set of Coast Guard rules for safety? --Stan Siegel ( stansiegel@aol.com). Response... [2 Sep 97] The U. S. Coast Guard publishes a multi-volume "Marine Safety Manual" which can be downloaded from their website in Adobe Acrobat format. The Table of Contents does not mention high speed craft specifically, but there may be info buried in the individual chapters. The USCG (and IHS) participated actively in reviewing the International Maritime Organization's (IMO's) safety standards for high speed craft, published as Chapter X of the International Convention for the Safety of Life at Sea (SOLAS), available from from various booksellers. See the IMO home page for more info. -- Barney C. Black ( webmaster@foils.org). [Date/Time=03-23-2002 - 12:35 AM] Name:webmaster@foils.org [Msgid=237121] Archive; Bigger Wakes For Wakeboards Click Below to Open. https://foils.org/bigwake.htm [Date/Time=03-24-2002 - 2:07 AM] Name:Webmaster@foils.org [Msgid=237510] Archive; Design Texts, Software, Sources Click Below to Open https://foils.org/texts.htm [Date/Time=03-24-2002 - 3:30 PM] Name:webmaster@foils.org [Msgid=237692] Archive; Ultra-Hi Speed Hydrofoils Click below to Open https://foils.org/knots.htm [Date/Time=03-24-2002 - 4:09 PM] Name:webmaster@foils.org [Msgid=237699] Archive; Info on Books, Films, Articles Click Below to Open this Archive. https://foils.org/media.htm [Date/Time=03-25-2002 - 2:52 PM] Name:Webmaster@foils.org [Msgid=238065] Archive; Engines Sources, Maint, Repair Click Below to Open this Archive. https://foils.org/engine.htm [Date/Time=03-25-2002 - 3:10 PM] Name:Webmaster@foils.org [Msgid=238073] Archive; Commercial Operating Costs Click Below to Open this Archive. https://foils.org/opcost.htm [Date/Time=03-25-2002 - 3:45 PM] Name:Webmaster@foils.org [Msgid=238096] Archive; Drag Reduction Click below to Open Arcive: https://foils.org/drag_reduction.htm [Date/Time=04-20-2002 - 6:22 PM] Name:webmaster@foils.org webmaster@foils.org, [Msgid=249644] Archive; Seakeeping / Motion Sickness Click below to Open Archive: https://foils.org/seakeeping.htm [Date/Time=04-20-2002 - 6:33 PM] Name:webmaster@foils.org webmaster@foils.org, [Msgid=249650] science fiction ViewThread I have written a science-fiction novel on an imaginary watery planet and have included hyrofoil vessels. I'd like to know if my fictional use and description of hyrofoils seems possible and accurate. Floatplanes with hydrofoil struts: These planes are about the size and speed of a Piper Cub although lighter due to use of carbon fiber components. It can also fly as a glider. The hydrofoil struts fold while the craft is in air flight. The wing fold when the craft opperates as a boat. A propulsion device, which runs off of a hydrogen fuel cell delivers periodic burst of power. The cadence of the burst can be adjusted to coordinate with air and water conditions. This planet has no fossel fuels and so energy efficency is of utmost importance, thus the importance of a engine that can be turned off when not needed. Sail hydrofoils: I imagine them as small and lightweight for carrying two people with no cargo. They have auxilary power provided by the same propulson device that is on the aircraft. The propulsor is used get onto step quickly. I'd like to know about how tacking works with hyrofoils. How close to the wind do you need to be to stay on step? A friend of my thought it would only work on a reach. My story includes a scene with a battle between a guy in the aircraft and a bunch of guys in the sail hyrofoils. The guys in the sail hyrodfoils mounted howitzers onto their crafts (they were not designed for this usage) If they shoot in the wrong direction, while healed over, the boat capsizes. The guy in the aircraft has a laser cutter which doesn't do much unless he strikes sensitive parts of the hydrogen tanks.(His craft can't carry the batteries or other power source for a big laser) Does this sound reasonable? [Date/Time=08-30-2002 - 4:20 PM] Name:Lizzie Newell lizzie-n@gci.net, [Msgid=303576] science fiction All sounds well, with a few small points. Sailboats rely on momentum to carry them through a tack. The same momentum keeps the boat foilborne. Some hydrofoil sailboats like the Windrider have trouble staying up while tacking, but that is because of the control system, not the foils. The Hobie Tri-foiler tacks while foilborne with no trouble. Also, recoil from a gun would not cause the boat to capsize. Foils can pull down on one side of the boat as well as push up on the other, which also means that a well designed hydrofoil sailboat doesn't heel. Plus the recoil is so short lived it would be absorbed by the mass of the hull and the foils wouldn't even need to react. However, such a recoil would likely damage the structure of the boat. Fire a large caliber rifle, it doesn't have time to push you off your feet, but it will hurt like hell if it's not tight to your shoulder. A more troublesome device for a hydrofoils would be something that induce prolonged thrust, like a mini-gun (electric gatlin gun). A high power rifle will not knock you over, but a 9mm machine gun (much lower power) will certainly push you off your feet if you are not braced for it. Fired forward it would produce a reaction thrust that would slow a boat down. Backwards it would add to the thrust of the boat (not a problem for a foil). Sideways would be like being on a reach in a strong wind. The foils would have to adjust, and the extra angle of attack would induce drag. But if the direction of fire is slightly to the rear, the pressure on the hull would increase it's speed, just as the pressure on the sail in a reach adds to the hull speed. You might want to look up something called a "gyro jet". It was a pistol cartridge invented a while back that used a sort of spin-stabilized rocket propulsion. Artillery is too heavy for a hydrofoil sailboat. Simply put, twice the weight, four times the drag. The Gyro jet was almost recoiless, required a much lighter gun, and I believe is the technique used by many hand-held flareguns today. As far as how close to the wind you can sail a hydrofoil boat, wind direction is only a problem as it relates to hull speed. If a sailboat can achieve 20 knots 15 degrees into the wind, so can a foilborne sailboat. The most likely problem would be going downwind. A sailboat is always slower than the wind going downwind. A 10mph wind would not be likely to keep any hydrofoil sailboat up on it's foils, not matter how efficient it is. Hope this was of some use, Scott [Date/Time=09-03-2002 - 9:09 AM] Name:Scott Smith ssmith@syntheon.com, [Msgid=304776] science fiction/fact Some additional sailing hydrofoil information: there is a whole new type of sailing hydrofoil(though Monitor was actually the first) being developed around the world: the monofoiler. These boats are stabilized(generally ,but not always) by the crew; they are basically monohulls not multihulls such as the Rave and Trifoiler.You can see an overveiw of some of these boats at:http://www.monofoiler.com These boats can sail on as few as two foils and are a new wave in sailng hydrofoils. Sailing hydrofoils most certainly can sail downwind at speeds substantially higher than wind speed: they do it by tacking downwind(actually and technically-gybing) .A well designed foiler can point as well as "normal" sailboat and at any rate it's VMG(speed made good to windward) will be better. At least one new monofoiler, the Dancer, has been designed to jump: the flying system is controlled by the skipper and ,at will, he can twist the hiking stick, pull the trigger and jump clear of the water(!)--just for the fun of it! [Date/Time=09-24-2002 - 9:37 AM] Name:Doug Lord lorsail@webtv.net, [Msgid=313865] Hydrofoils are more than speed Why is speed always the focus when reading about hydrofoils? Consider the following: 1. Today in Sweden (Scandinavia, EU) the price/US gallon of diesel is about USD3.90 to USD4.00 due to tax 2. 95 % of all running time of pleasure boats takes place in smooth weather with moderate wave sizes (in fact the waves that cause irritation, not problems, are those generated by other boats, not the weather/wind. This is due to the large protected water areas by the archipelagoes surrounding Scandinavia and also due to rather low statistic average wind (force 2-3, Baltic coast areas) 3. The trend for pleasure boats is not always towards larger size but more towards comfort and luxury, etc., which makes the boats heavier. A 25-ft powerboat costs almost double the price in 2002 compared to the price of the same length craft a few years ago (including correction for inflation) 4. The average cruising speed is 22-26 knots even if top speed is 32 -40 knots. In fact, the average speed very seldom surpasses 22 – 26 knots. Rather often you see powerboats in the size 25 to 40 ft operated at 12 – 17 knots albeit they are built for higher cruising speeds. When I ask people why they are running their boat this way, frequent answers are: for comfort and/or economy/mileage reasons. The comfort factor is important (i.e. not to have to reduce speed frequently when meeting waves from other boats/ferries etc. which in fact now is the case. It is not due to poor performance of the boat – it is for better comfort, sometimes noise factor, compared to cars. Having these aspects in mind, the relatively simpler design task of hydrofoils for smaller boats compared to ferries may be could open up opportunities if comfort, noise, and mileage are focused on instead of just the high speed performance. [Date/Time=10-15-2002 - 7:16 PM] Name:Tomas Järnmark Tomas.Jarnmark@electrum.se, [Msgid=324184] Read a Good Book Lately? Are there today any sort of updated standard “bible” books (for designers, producers, students, etc.) that summarize what is acknowledged know-how (R&D, field experiences, truths & myths, designs, developments, costs, performances, bench marking comparisons etc)? If so where can I order these? [Date/Time=10-15-2002 - 7:17 PM] Name:Tomas Järnmark Tomas.Jarnmark@electrum.se, [Msgid=324185] Do Foils Equal Comfort? ViewThread Is a hydrofoil-based boat in the size of 27 ft more comfortable (cut through larger waves with better comfort, movements, splashes, etc.) at 25 knots than a surface-planing boat of the same size and speed? [Date/Time=10-15-2002 - 7:20 PM] Name:Tomas Järnmark Tomas.Jarnmark@electrum.se, [Msgid=324187] Do Foils Equal Comfort? Yes, [Date/Time=10-27-2002 - 7:30 PM] Name:Harry Larsen hlarsen0@gte.net, [Msgid=329671] Yes, Foils Equal Comfort! Harry should know. Visit his most interesting website at http://home1.gte.net/hlarsen0/ [Date/Time=10-29-2002 - 7:13 PM] Name:Barney C Black webmaster@foils.org, [Msgid=330715] Fibreglass Ship Manufacturing I am writing on behalf of one of my friends who lives in Iran. He is an inventor and would like to inquire for some information on manufacturing a fibreglass ship with 500 tonnes capacity in the merchant sector. It would be a greatly appreciated if you would alert me to any information resources on modeling, manufacturing (ship and or fibreglass). and the possibility of using fibreglass in this case? [Date/Time=12-20-2002 - 3:37 AM] Name:Mehrdad Tavana m30tavana@yahoo.com, [Msgid=353812] NACA 0015 Pressure Distribution ViewThread I'm looking for the theoretical pressure distribution (considering an invicid flow) for different angles of attack, for the NACA 0015. [Date/Time=03-25-2003 - 7:43 PM] Name:R. Sosa rsosa@fi.uba.ar, [Msgid=403003] Re; NACA 0015 Pressure Distribution I have access to a program called WingAnalysis Plus which is able to calculate the pressure coefficients for a range of foil types. You can purchase a copy of that program via the internet though I don’t have the website address at hand. I have calculated the distribution of pressure coefficients for the NACA 0015 foil at a range of angles of attack from 0 to 10 degrees at 2 degree increments. The results are attached as an Excel spreadsheet. Remember that these results are obtained from a theoretical method and so don’t represent measured test data. I can’t promise the results are accurate. I believe it should also be possible to derive the Cp distribution around a NACA 0015 foil at various incidence angles by reference to the text book “Theory of Wing Sections” but I have not yet done so myself. If you have found better (experimental) data, perhaps you can post a message letting people know where that data can be found. [Date/Time=05-28-2003 - 11:54 AM] Name:Martin Grimm seaflite@alphalink.com.au, [Msgid=442981] Attached File "NACA0015CpvsAoA~xls.zip" - size 54784 Click Here To Download X-Craft Press Release ViewThread Titan Wins Contract To Build Navy's X-Craft San Diego - Feb 26, 2003 - The Titan Corporation of San Diego said Tuesday that it has been awarded a $59.9 million contract by the U.S. Navy's Office of Naval Research (ONR) to develop and build the Navy's "X-Craft". The X-Craft will be a high-speed aluminum catamaran consisting of an advanced hull geometry, designed to give the craft speeds of 50 knots or more. Initially it will be used by ONR for purposes of hydrodynamic experimentation to include the addition of advanced lifting bodies and polymer drag reduction techniques. The X-Craft's deck will have two helicopter landing spots capable of handling a variety of aircraft up to the size of the H-60 helicopter series. With a design displacement of approximately 1,100 long tons, the 80m. long by 22 m. wide X-Craft will be self-deployable and of flexible design for spiral technology insertion. A Combined Gas Turbine or Diesel (CODOG) propulsion plant will propel the X-Craft to speeds of 50 knots or more. The CODOG propulsion plant is expected to consist of two GE LM-2500 gas turbine engines totaling 50,000 hp and two MTU 16V595 16-cyl 4380 kW diesels driving KaMeWa 125SII waterjets through Renk gearboxes. The vessel's Mission Module Bay will be capable of fully supporting multiple mission packages simultaneously. Titan also announced that it is awarding to Nichols Bros. Boat Builders, Inc., a subcontract to provide hull, mechanical, and electrical ship systems for the U.S. Navy's new X-Craft. This award to Nichols Bros. completes an RFI and RFP effort initiated by Titan less than six months ago. Nichols Bros. Boat Builders, headquartered in Freeland, (Whidbey Island) WA, specializes in the building of high-speed catamarans and other vessels. Work on the X-Craft was expected to begin in May 2003 and deliver in August 2004. A later phase of the program will add a lifting mid-body and a polymer injection system. [Date/Time=07-26-2003 - 8:18 AM] Name:Greg Bender glbender@erols.com, [Msgid=476489] Re; X-Craft Press Release See the Hydrofoils:Military category of this BBS for a thread of recent discussion on the X-Craft. [Date/Time=07-27-2003 - 8:58 AM] Name:Barney C. Black webmaster@foils.org, [Msgid=476922] Hydrofoils vs Tunnel Hulls? ViewThread Given that the two are of similar weight and power, which is generally faster and has less drag, a hydrofoil, or a tunnel hull (like raceboats)? I know that the two work very differently, and am very intersted in finding the answer to this question. [Date/Time=12-31-2003 - 6:15 PM] Name:Timothy Shaw slickmod@hotmail.com, [Msgid=565242] Re; Hydrofoils vs Tunnel Hulls? Hi Timothy, Although I am a hydrofoil enthusiast, my gut feeling is that for relatively calm water powerboat racing applications, the tunnel hull (such as unlimited hydroplanes) would come out as having less drag and hence translating to more speed than a hydrofoil design for the same installed power. Tunnel hulls seem to just skim over the water on the ends of their three(?) planing surfaces when at speed, so it is hardly a case of them having excessive wetted surface area which is what leads to frictional resistance. On the other hand, a hydrofoil design, even with only the very small hydrofoils that would be needed to support a relatively light boat at such high speeds, would still incur the additional drag of the supporting struts. The high speed would also mean that supercavitating foils are likely to be required and these don't tend to have particularly high lift to drag ratio's. Some means of surface sensing would probably also be required to control the foil angle of incidence so that the craft remains stable. This would probably mean using a planing surface sensor with associated drag as well. I would be delighted to hear that the opposite is that case, but then why are there no hydrofoils competing in "unlimited" powerboat races? Surely it is not just as simple as that nobody has thought about trying this idea or that hydrofoils are not permitted by the rules of an "unlimited" race!? By the way, hydroplanes do seem to make use of hydrofoils of sorts (probably also supercavitating foil sections?), in way of high aspect ratio skegs mounted on one side of the hull as a means of aiding in getting a "grip" when going around the circuit. They don't help lift the boat, if anything they stop it from toppling over in a sharp turn. At least that is my understanding. Perhaps you can enlighten us more about those devices? [Date/Time=01-01-2004 - 10:40 AM] Name:Martin Grimm seaflite@alphalink.com.au, [Msgid=565409] Re; Re; Hydrofoils vs Tunnel Hulls? Martinn, I am aware of at least one person who was involved with hydroplane racing that looked at putting supercavitating foils on the sponsons. I believe he petitioned APBA (American Power Boat Association) but do not know the outcome. This individual died last year, he was in his late 90s. He was also involved in the Boeing High Speed Test Craft in its early trials. Sumi Arima [Date/Time=01-02-2004 - 1:05 PM] Name:IS. Arima arimas1@juno.com, [Msgid=565775] Re; Re; Hydrofoils vs Tunnel Hulls? It doesn't seem likely that anyone using a hydrofoil will successfully compete against tunnel hulls, unless they come up with something radically different. It doesn't really matter whether you are discussing the small, sheltered water tunnels (commonly called a pickle fork), or the big, open water cats. Both of these boats are now capable of very high speeds. Since at these speeds they are no longer pushing a bow wave, the induced drag is very low. The drag from any foil system at 100mph+ becomes very high, regardless of how well designed or made the struts and foils are. Ask one of the open water boat designers how much drag force the skegs have to handle, you might be surprised at the answer. But a large part of the problem is control systems. Even with a good, fast system for controlling the foils, at those speeds the slightest glitch would be a disaster. The occaisional rogue wave has destroyed many a racers dream for victory. I remember when a 40 foot cat nosed into a rogue wave and was driven straight to the bottom, killing both crew members while doing almost no damage to the boat. Imagine what could happen if you managed to get a negative angle of attack on a foil for even a fraction of a second at 100mph. It would be catastrophic. And the smaller sheltered water boats can easily pull more than a G in a fast corner, the slightest tracking error induced by a foil or strut would be equally destructive. But being a foil enthusiast as I am, I would love for someone to prove me wrong. 🙂 [Date/Time=01-23-2004 - 8:19 AM] Name:Scott Smith ssmith@syntheon.com, [Msgid=576707] Re; Re; Hydrofoils vs Tunnel Hulls? Timothy and Scott From my perspective at speeds of 100knots and up the US Navy in the Seventy's built Two 100 Ton, 85 ft Surface Effect Craft to explore the potential. One was powered by Partially Submerged Supercaavitating Propellers (most racing surface drives are direct descendants of these) and the other powered by two stage axial waterjets. Both these craft were essentiall very fine hulled catamarans at high speed. Just a couple of feet of the aft length of their hulls were in the water at speed, and then only a couple of inches deep. This along with aft fins/rudders provided directional stability. The lift fans and Skirts kept the hulls out of the water at lower speeds, say 0 to 60kts), but at very high speed thay almost operated like a pure tunnel hull with a very wide tunnel. Both these vessels used the air cushion to control the heave and pitch of ride at very high speeds. They had response frequencies of up to 100hz and needed it. But they worked very successfully. To prevent the catastrophic pitch-ins you desribed, the Navy did a lot of research in shaping the above water shape of the Cat hulls and the Bow cross structure ramps between the hulls. One of them even had above water anti pitch foils attached at the bow that were a last resort to prevent pitch-ins. During there 10 year lifetimes they operated in all sea conditions offshore (greater 10+ significant wave height). The only reason they ever slowed down was for visibility or the crew got tired of the beating when in severe seas. Most Hydrofoilers consider that the Navy's PHM hydrofoils had the highest performance, but they only went about half the speed of these SES. The great benefit of the hydrofoil especially the fully sbmerged type on the PHMs was the ability of the active ride control system on those foils to level out the ride in waves less than 10 ft significant height. They could also operate in even higher seas but would start to countour the swells in these very high seas. I worked on the ride control systems for all these craft and it was indeed state of the art then and easily now to control the actuators at the very high frequencies needed to keep them safe. As for resistance. Both Hydrofoils and Tunnel Hulled Cats can be very efficient or very Inefficient according to the skils of the designer. On average. most tunnel hulled cats at high speed (100kts) are close to fifty percent more efficient than hydrofoils. There are a lot of people in IHS who would disagree with me there. The reason why is that the propulsion efficiency has to be accounted for too. In the PHM the waterjets were mounted very high 12 feet above the water and had lots of losses especially in the zee shaped water inlets. The two Navy SES 100 ton vessels had about a twenty percent speed difference for about the same power due also mostly to the difference between the Waterjet (lower efficiency) and the Partially Submerged Supercavitating Propellers (high efficiency and no struts or exposed prop shafts). Design is all about choices, and a good Naval Architect can make any of these hull forms into a reasonably well performing vessel. Enjoyed your comments Bill White [Date/Time=01-26-2004 - 8:31 AM] Name:Bill White whitewn@speakeasy.net, [Msgid=578306] Transport Efficiency of Hydrofoils etc Hi Bill, Good to see we are not all only passionate about hydrofoils and can see merit in other forms of high speed marine craft. Naval Engineers Journal, February 1985, page 211 indicates that the maximum speed of SES 100A was 80 knots (approx) and SES 100B was 90+ knots. Displacements were 289,650 lb (129.3 tons) and 206,000 lb (92.0 tons) respectively while total installed power (lift and propulsion) was 15,000 HP and 15,360 HP respectively. In comparison PHM displacement was 249.7 tons (NEJ, Feb 85, page 173) and power was 17,000 HP (page 161). Speed was 50 knots plus. Comparing calm water transport efficiency (displacement x speed / power) we have approximately: SES 100A = 0.690 ton.knots/HP SES 100B = 0.539 ton.knots/HP PHM = 0.734 ton.knots/HP So it could be said that SES 100B was roughly 30% more efficient than the PHM even given its higher maximum speed. The question I have is how do hydrofoils, SES, monohulls, catamarans etc compare when it comes to sustained speed for a given power in a seaway? Also in the February 1985 issue of the Naval Engineers Journal on page 57 Michael Eames presents charts of sustained speed in a seaway for 200 ton and 1000 ton vessels of various types. These charts indicate that the achieved speed of a low length to beam ratio ACV or SES falls rapidly with increasing wave height (from 80 knots in calm water to 40 knots in 2 metre significant wave height), while the notional 200 ton hydrofoil has a far more gradual speed degradation with increasing seastate (remains close to 50 knots in up to 4 metres significant wave height). It would be good to get some more specific data on the relative performance of various craft types as sea state increases. [Date/Time=01-31-2004 - 9:51 AM] Name:Martin Grimm seaflite@alphalink.com.au, [Msgid=581470] Transport Efficiency of Hydrofoils etc Hi Martin, I agree fully with your comparison of hydrofoils and SES. An interesting document was published called "Hull Form and Propulsor Technology for High Speed Sealift revised: 13 February 1997". Contact Chris Mckesson for a copy. The whole document is 45MB. Perhaps we can put it in the IHS website? The document compared the transport efficiency of different kinds of craft and their conclusions wer very similar: for state ofthe art vessels of each type, SES and air cushion vehicles offer the best transport efficiency. Hydrofoils were superior to planing, semi-planing and semi-displacement craft for volume Froude numbers (Fnd) of about 3.0. I have compared the hydrofoil-assisted catamaran data I have and it turns out they offer improved transport efficiency compared to regular hydrofoils -about 30% better - and offer improvement in transport efficiency from Fnd=2.20. No data was given in the report for varying sea states and I agree it would be very interesting to know how these compared for differing sea states. [Date/Time=02-02-2004 - 3:56 AM] Name:Gunther Migeotte gunther@cae.co.za, [Msgid=582312] Transport Efficiency of Hydrofoils etc Martin and Gunther Thanks for the feed back. The Speeds quoted in the Naval Engineers Journal for all these vessels (100A, B and PHM were all under quoted by about five knots here and almost everywhere else during their active duty times. Since the diferrential was just about constant accross the board your efficiency comparisons should stay the same. The speed impact of sea state on the vessels was never reported in the public domain with any accuracy. The PHM hydrofoils had by far the smoothest ride. They could maintain foilborne operations through sea state five. (10ft sig wave ht) And with care during operations they could often stay foilborne up well into sea state 6. But if you came off of foils in high sea states 10 ft sig wave and above it was difficult to get them foilborne again. Their hull borne sea keping was excellant as well but at speeds of 10kts or less. The SES and ACVs were also very good in rough seastates. When cushionborne, they would slow down due to the added wave resistance while still at full power through SEA State 5 the same as the PHMs. In Sea State 6 and up they would usually reduce speed for personnel safety. The ride was never as smooth as the PHMs but they still went faster through most of the operating envelope of sea state (0-6). We have very little operational information in even higher sea states, but the SES 200 which was closer to the PHMs in size, did operate at 20+ kts in a Hurricane in the Gulf of Mexico while performing a rescue mission with the Coast Guard when none of the Monohull 100 plus foot Cutters would go out. I can attest to the SES 200's excellent seakeeping having been aboard for a nonstop voyage from Norfolk to Halifax in early winter. The effect of the ride control system on that vessel was very impressive. Most of the published seakeeping papers on these craft were severly compromised by politics and arbitrary motion limits on the feasible operating envelope. Even the SWATH papers often were conservative. Thanks again Bill White [Date/Time=02-03-2004 - 8:06 PM] Name:Bill White whitewn@speakeasy.net, [Msgid=583540] Transport Efficiency of Hydrofoils etc Gunther and Bill, Thanks for your comments and additional insights on this subject. I am looking at transport efficiency data at the moment as a personal interest which was also prompted by a recent paper which briefly compared hydrofoil supported catamarans against other types of high speed craft. The document on high speed sealift sounds like one that would be worthwhile reading, though my interest is in passenger-only craft at the moment. These are more suited to application of hydrofoils than multi-thousand tonne sealift ships. [Date/Time=02-10-2004 - 10:22 AM] Name:Martin Grimm seaflite@alphalink.com.au, [Msgid=594015] hull choices 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=02-11-2004 - 9:02 AM] Name:glen oldfield compositedesign@hotmail.com, [Msgid=594722] Transport Efficiency of Hydrofoils etc THe sea lift paper is quite good as it covers wide range of ships from passenger vessels right up to the USS "United States" and covers all the different concepts in high speed craft including, semi-displacement craft, planing craft, hydrofoils, air cushion craft, hydroplanes, sea sleds etc. It also gives state of the art examples of each. I would bery much like to see your paper on transport efficiency comparisons of different types of craft. Can you post it on the IHS website? [Date/Time=02-12-2004 - 11:44 AM] Name:Gunther Migeotte gunther@cae.co.za, [Msgid=595556] Transport Efficiency of Hydrofoils etc Gunther, I am still collating and cross checking the vessel performance data where possible. When I have completed it as far as I can go, I will see how it can be made available via the website. [Date/Time=02-14-2004 - 9:04 AM] Name:Martin Grimm seaflite@alphalink.com.au, [Msgid=596590] Effect of Marine Groth on Hydrofoil Craft ViewThread I have recently had some discussions with fellow hydrofoil enthusiasts about the subject of marine growth on the foils of hydrofoil craft and how best to protect against this. It has been an aspect of hydrofoil operation that has always been a bit of a mystery to me. On several occasions I have read or heard that it is necessary to regularly clean the foils (and presumably also the hull) if hydrofoil craft are to maintain good take-off and foilborne performance. Without such regular cleaning, I recall reading that the Rodriquez hydrofoils on Sydney Harbour could even experience difficulty taking off with a full passenger load. More recently I have been told that a European operator of hydrofoils prefers to clean the foils every four weeks, either by lifting the craft out of the water or by sending a diver down to do this work underwater. Of course, either option adds to the running expenses and could become costly. A review of hydrofoil operations in the November 1969 issue of Hovering Craft and Hydrofoil magazine also indicated that a Scandinavian operator also docked each hydrofoil every four weeks for two days of cleaning and overhaul. I would be interested to hear whether any rule-of-thumb or more precise means of assessing the impact of marine growth on the performance of a hydrofoil is available? For displacement vessels, a rule-of-thumb allowance for the effect of marine growth is to add 0.1% to the total frictional resistance for each day in service after the vessel has received a fresh anti-foul paint coat. After 6 months, that equates to about 18% additional frictional resistance at a given speed, or more realistically, a speed reduction for a given engine power output. None the less, due to the form of the resistance curve for monohulls and catamarans, this additional drag will probably slow the vessel down in a fairly linear fashion with each day out of dock. In the case of hydrofoils, I can imagine the power margin available to become foilborne when fully loaded could be relatively small and so the craft may struggle to become foilborne with only moderate fouling. To further complicate matters, marine growth may cause a reduction in lift of the foils at a given speed in addition to the increase in frictional resistance. The analogy to this situation is the build up of ice on aircraft wings, which can have a drastic impact on both lift and drag. I am also interested to hear views on the best means of minimising marine growth on the foils so that the period between cleaning of the foil surfaces can be maximised. For example, would highly polished stainless steel foils (as used on many Russian hydrofoils, Jetfoils and some Supramar hydrofoils) offer better resistance to marine growth than the more typical high tensile steel which requires some form of surface coating to prevent corrosion? If a surface coating is to be used, has any information been published on that subject with specific application to use on the foils of hydrofoil craft? [Date/Time=02-28-2004 - 8:43 AM] Name:Martin Grimm seaflite@alphalink.com.au, [Msgid=604934] rtiEffect of Marine Groth on Hydrofoil Craf Dear Martin, the most useful reference on hydrofoil fouling that I have found is in Marine Technology: Experimental Investigation of {Eneromorpha Clathrata} biofouling on Lifting Surfaces of Marine Vehicles, Marine Technology 38(1) pp31-50, January 2001. I think that paper will answer most of your questions. If you are a SNAME member you should be able to download it off their website. [Date/Time=03-01-2004 - 10:20 AM] Name:Gunther Migeotte gunther@cae.co.za, [Msgid=605863] View Messages Search Messages Return to Home Page Frequently Asked Questions This board has been viewed 21676 times since Apr-20-2002 . (Total Views Since Board Creation on Mar-21-2002 is 22410.) Questions about this board, email: bbs@foils.org System Support, Email: support@bulletinboards.com To Learn About Bulletin Boards: Click Here Bulletin Board Management Site: Click Here (321) 984-9080 © 1997 - 2004 P.A. Corp. V7.1
