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

The International Hydrofoil Society (IHS) Hydrofoil Correspondence Archives


Updated last August 20, 2006

Hydrofoils: Sailboats

Hydrofoils: Sailboats      Top


Archived Messages


“1”,”946256″,”9″,”Re; Foilboard Video||946256″,”OK, all you technical types out there – take a look at this video and then try to explain how it’s balanced about each axis!

Furthermore, if the foiler had been more balanced, he could have focused on speed and the non-foiler might not have overtaken him at the end of the video.

I’m guessing the Miller foil sailboard ( // ) has better pitching stability.”,”2005-12-12″,”Mac Stevens”,”nopswd”,” “,””,”945786″

“2”,”946245″,”9″,”Re; Foilboard Video||946245″,”OK, all you technical types out there – take a look at this video and then try to explain how it’s balanced about each axis! Ok, I’ll try:

I challenge your premise that it is balanced about each axis. The board appeared quite unbalanced.

I think it is balanced the same way a unicycle or an ordinary sailboard is balanced, i.e., the operator’s control of weight and other forces.

The rear hydrofoil probably adds some pitching stability.”,”2005-12-12″,”Mac Stevens”,”nopswd”,” “,””,”945786″

“3”,”946241″,”9″,”Re; Foilboard Video||946241″,”OK, all you technical types out there – take a look at this video and then try to explain how it’s balanced about each axis! Ok, I’ll try:

I challenge your premise that it is balanced about each axis. The board appeared quite unbalanced.

I think it is balanced the same way a unicycle or an ordinary sailboard is balanced, i.e., the operator’s control of weight and other forces.

The rear hydrofoil probably adds some pitching stability.”,”2005-12-12″,”Mac Stevens”,”nopswd”,” “,””,”945786″

“4”,”945786″,”9″,”Foilboard Video||945786″,”OK, all you technical types out there – take a look at this video and then try to explain how it’s balanced about each axis!”,”2005-12-10″,”Tom Speer”,”nopswd”,” “,” “,”9”

“5”,”873505″,”9″,”Re; Hydrofoil Voyager David Keiper Book||873505″,”I have just listed a copy of David A. Keiper’s book Hydrofoil Voyager on eBay. The item number to search for is 4567171188. This is a 10-day listing. This item is out of print and scarce. The book is (mostly) about design, construction, and sailing in the Pacific in the first hydrofoil sailing yacht WILLIWAW. See the listing for more details. There is a review of this book at: // There is info about Dave Keiper at: // There is a short video clip of WILLIWAW in action at (this is an 11 meg file, so don’t dare go there if you have a slow internet connection!) Questions about this book may be submitted via the listing on the eBay website.
“,”2005-08-08″,”Barney C Black”,”poopdeck”,” “,””,”9″

“6”,”862912″,”9″,”Hydrofoil Voyager David Keiper Book||862912″,”I have just listed a copy of David A. Keiper’s book Hydrofoil Voyager on eBay. The item number to search for is 4563256226. This is a 10-day listing. This item is out of print and scarce. The book is (mostly) about design, construction, and sailing in the Pacific in the first hydrofoil sailing yacht WILLIWAW. See the listing for more details. There is a short video clip of WILLIWAW in action at (this is an 11 meg file, so don’t dare go there if you have a slow internet connection!)”,”2005-07-18″,”Barney C Black”,”poopdeck”,” “,” “,”0”

“7”,”851283″,”9″,”Re; Re; Surface piercing hydrofo||851283″,”Jake,

The foiler moths that I have seen don’t have fences fitted and seem to be able to get away without them. In the first instance, in your position, I wouldn’t bother to fit fences and just test the board to see how it goes. After experimenting, if you have the feeling that air is being drawn down on the low pressure face, then you can always retrofit a fence or two later. Any fence will normally add drag, and that is the last thing you need if you are trying to speed sail. “,”2005-06-26″,”Martin Grimm”,”nopswd”,” “,””,”0″

“8”,”830684″,”9″,”Rave Hydrofoil for Sale||830684″,”WindRider RAVE Hydrofoil Trimaran Sailboat, 1999, Main and Jib, yellow hulls, custom galvanized trailer. Dealer display boat. $4000

Bob Rundus Sailboats
36 East Green Street
Champaign, IL 61820
Phone 217-359-3000
“,”2005-05-18″,”Robert Rundus”,”nopswd”,” “,””,”0″

“9”,”821336″,”9″,”Re; Re; Surface piercing hydrofo||821336″,”Thanks Tom,
I have just re-read my posting and I have been somewhat confusing. I am not looking at bi-directional foils. I am wishing to build a pair of asymetric windsurfer fins suitable for surface piercing usage, as the fin will be fitted behind or to the side of the board, not sticking out of the bottom of it, and may be canted to provide some lift. As I have fitted the device to a speed board and intend to take it to Weymouth speed week this year, low drag and no ventillation at high speeds are important factors. I have also conceived a system that enables the two separate fins, one port , one starboard profiled to be swapped while sailing. I just need to get the test rig working on one tack so that the optimum fin position, cant, rake, attack angle etc. can be discovered.
Could I just use one of the profiles you recommend for foiler moth lift foils and fit a couple of fences?
Rich Miller, by using a long symetrical root foil with fence, ended up with his asymetric foils submerged all the time, so the demands on his foils were slightly different to mine. “,”2005-04-30″,”Jake Frith”,”nopswd”,” “,””,”0″

“10”,”821326″,”9″,”Re; Re; Surface piercing hydrofoil||821326″,”I don’t think ogival sections are a great idea. The sharp leading edge leads to separation unless the angle of attack is in a narrow range of ideal angles of attack. When separation occurs, you have all the ideal conditions for ventilation. So everything can be fine, and then suddenly change dramatically with just a small difference in loading.

It’s possible to design bi-directional sections that have rounded edges instead of sharp ones. With attached flow at the leading edge, you can maintain a good run of laminar flow, while still controlling the location and extent of the laminar separation bubble. And separation begins at the trailing edge, where it can progress smoothly and predictably as you load the foil.

For an example of such bi-directional sections, see These are predicted to have comparable performance to conventional NACA sections, but no experimental data are available to confirm this yet.”,”2005-04-30″,”Tom Speer”,”nopswd”,” “,””,”0″

“11”,”819881″,”9″,”Corection to address||819881″,”Hi Jake,

Here’s a quick correction to the web site given previously. It is: and the tread you are looking for is “foiler design”. You will probably be required to register, but you should find the site to be useful.

If you reply and need a response, use this temporary address: “,”2005-04-28″,”Ray Vellinga”,”nopswd”,” “,””,”0″

“12”,”819877″,”9″,”Re; Surface piercing hydrofoil||819877″,”Jake,

If you are not already reading, you should try it. There you will find a running dialog about designing hydrofoil sailing moths.

If you design a sailing board that reverses direction, look at the Ogival sections. They are symetrical fore and aft, ie, they have sharp leading edges coming and going. They are a segment of a circle on top with a flat underside.

Hope this helps.

Ray Vellinga”,”2005-04-28″,”Ray Vellinga”,”nopswd”,” “,””,”0″

“13”,”819373″,”9″,”Re; Surface piercing hydrofoil||819373″,”You raise quite a few thought provoking questions in your posting. Hopefully one of the design-oriented people in IHS will answer you. Meanwhile you might want to take a look at Rich Miller’s successful design, if you have not already seen it. Check these two pages:

Click to access miller.pdf

I doubt that Rich follows the IHS BBS, so if you want to talk to him, you could certainly give him a call or send him an email. The last contact info I have for him is: Rich Miller (; 640 Colusa Avenue; Berkeley CA 94707 USA; phone: 510-525-8006. I am not sure if all that is still good.”,”2005-04-27″,”Barney C Black”,”nopswd”,” “,” “,”0”

“14”,”819015″,”9″,”Surface piercing hydrofoil||819015″,”I would be enormously grateful for any advice IHS membes can give on the following:
I am nearing completion of a sailboard based test rig which I intend to use to attempt to achieve a semi hydrofoiling single tack sailboard. In short, the system uses a conventional board, truncated aft of the back strap with finbox removed and filled in flat. There is a mechanism that allows the fin to be adjusted in pitch, cant, angle of attack, depth, and -within the constraints of the position of the board and the sailor’s back foot- position. (In other words infinitely adjustable)
I propose to carry out the following test schedule:

1) Fix a conventional symetrical fin centrally as far forward as the back of the board will allow, ie., so it is in the same position as it would have been slid right to the back of the finbox, except it will no longer have the endplate effect of the board. The task here will be just to get the thing sailing. First barage of questions… Will a conventional fin just spin out due to the loss of the endplate effect allowing air to be sucked down? If I wish to fit fences to the fin, how big should they be, should they entirely surround the chord or just be around the leading edge? Should the fences be angled up or down, if so by how much? When I travel at high speed in choppy water on a standard board and the tail of the board frequently leaves the water I don’t immeadiately spin out, so would I even need to modify the fin at all?

Part ii)Fit asymetric foil/s (single tack use obviously) so that the fin will attempt to provide lift, rather than just lateral resistance, and start playing with angles of attack and canting the fin (tip to windward) to provide a more accurate counter to the forces from the sailor’s feet and the mastfoot. I have been looking at the horizontal lift foils that Moths are using, but am not sure if they will work in the context of surface pircing and at the higher speeds. (anything over 50 knots will do:) Once again, will it need fences?
Essentially my problem is that I have spent far too much time actually windsurfing etc. to learn how to design my own bespoke range of foils for this craft. I am capable however of drawing a series of chords from foil coordinates and building a simple foil.
Does anybody have a good idea what foil already designed (and at what scale of chord) might work for these purposes (both the symetrical and asymetrical), and where I might find the coordinates. For ease of fabrication I would like to try a straight untapered foil, perhaps just with a bit of finishing at the business ends that could also be end for ended for the different tacks on the asymetric foil.
Any other comments on whether this has been done before etc. most welcome.
Final inventor’s rant… I believe that the recent regaining of the outright speed sailing record has largely been due to Finian Maynard’s adoption of a single sided rig. After all Yellow Pages’ foils only allowed it to sail on one tack. Why, when water is some 800 times denser than air and fairly primitively rigged ice yachts have bettered 100mph, is the windsurfing world wasting time developing rigs while still sailing on fins that are hugely compromised by having to work on both tacks?
Secondly, Think why a windsurfer has a fin mounted in the middle sticking out of the bottom of the board at the back. I think it might be lazy thinking – the evolution from surfboards which do not have to cater for the same loads, and ease of manufacture. There are two seperate forces delivered by a windsurfer: planing lift of the board and lateral lift of the fin. by sticking the fin out of the board, surely you are introducung all sorts of strange immeasureable vortices at its base. The stuff I am doing at the moment is attempting to divorce as much as possible the two different goals of board and fin. It may of course not work…
Any ideas, help gratefully received here or on”,”2005-04-26″,”Jake Frith”,”nopswd”,” “,””,”0″

“15”,”817494″,”9″,”New Book on Hydrofoil Sailboat MONITOR||817494″,”The auction is now closed. However, the book can still be purchased direct from the author. The closed eBay listing can be viewed for 90 days to get details about the book and some copies of the illustrations. Just used the advanced search function on the ebay site to search for the item number among the completed auctions.”,”2005-04-23″,”Barney C Black”,”poopdeck”,” “,” “,”0”

“16”,”814200″,”9″,”New Book on Hydrofoil Sailboat MONITOR||814200″,”There is a new book for sale on eBay about the hydrofoil sailboat MONITOR developed in the mid-1950s by Baker Manufacturing Co with US Navy backing. Go to and search for item # 4542861342. The listing expires in five days.

The 61 page soft cover book includes 19 drawings and sketches of various elements of the MONITOR design covering the foils, hull, sail and control arrangements. Also contained in the book are 25 photos of MONITOR and other Baker hydrofoil craft. The back cover features a screen shot from a simulation by Hanno Smits. This book is undoubtedly the most definitive single source of information describing the MONITOR design.

MONITOR Principal Characteristics:

Sail area: 230 square feet
Length of hull: 26 feet
Overall width: 21 feet
Weight 1014 lbs plus operator(s)
Wind velocity required to fly: approx 13 knots
Automatic trim regulation with varying thrust
Steering by rotation of rear foil
Foil incidence angles adjustable in flight
Rolling moment partially compensated by differential adjustment of foil angles

This book will be of interest to designers and engineers who want to know the details of MONITOR’s design and construction. It is also of interest to hydrofoil historians and model makers. People intrigued by David Keiper’s hydrofoil yacht WILLIWAW and hydrofoil sailboat STORMY PETREL may also be interested in this book about an earlier sailing hydrofoil craft.

“,”2005-04-16″,”Barney C Black”,”poopdeck”,” “,” “,”0”

“17”,”789894″,”9″,”Telestar foil conversion||789894″,”Michael

Go to our primary web site at


Then go to our Pico search at the bottom of the page and enter

Sailing Foils or ladder foils

You will find tons of information addressing your conversion.

It has been a long time since I saw a working Telestar. Good Luck

Bill White
Web master”,”2005-03-02″,”William White”,”nopswd”,” “,””,”0″

“18”,”782452″,”9″,”Telstar 28||782452″,”Intersted in building a ledder hydrofoil on my Telstar 28 (simmiler to dak hydrofoil).
looking for information/blueprints/etc that can help me with this.
“,”2005-02-16″,”Micael”,”nopswd”,” “,””,”0″

“19”,”764795″,”9″,”Re: Bruce’s Foil||764795″,”The best information is by Edmond Bruce himself – “Design for Fast Sailing,” The Amateur Yacht Research Society, 1976. I think there’s also some information on Bruce foils in the AYRS book, “Sailing Hydrofoils.”

(Some background: the Bruce foil is like a daggerboard or centerboard placed on an outrigger instead of on the centerline of the boat. The foil is canted to provide a stabilizing vertical force as well as a horizontal force to counter the side force from the rig. This greatly reduces the heeling of the boat, using the hydrodynamic moment from the foil for lateral stability instead of the hydrostatic moments from hull form stability or keel ballast.)

Bruce typically canted the foils at 45 degrees from the vertical (tip inward). The outrigger beams were sized such that the center of laeral resistance of the foils was located the same distance from the centerline as the height of the center of effort of the sail rig. Both low aspect ratio foils and moderate aspect ratio foils were used. His small scale tank tests showed an aspect ratio of 1 gave him the best performance, although he only tested aspect ratios of 3 or less and at low Reynolds numbers. I believe in later publications he used a planform with a circular arc (ogival) leading edge and straight trailing edge.

In his moderate aspect ratio sailing experiments, he mounted the foil on a small outrigger float with a pivot so that it could be raked aft like a centerboard when the foil was to windward. One needs to have the center of lateral resistance aft with the foil to windward and forward with the foil to leeward to get the same directional balance as a centerboard, because the force from the sail is inclined forward.

As for sizing the foil, I’d be inclined to use 40% more area than you’d use for a conventional foil. I’d also go with a high aspect foil rather than the low aspect ratio that proved best in his tow tank tests. Naturally, a symmetrical section is required because the foil has to operate on both tacks.”,”2005-01-15″,”Tom Speer”,”nopswd”,” “,””,”0″

“20”,”762800″,”9″,”Bruce’s Foil||762800″,”Can anyone supply design criteria for an Edmond Bruce foil?”,”2005-01-12″,”B.Rowe”,”nopswd”,” “,””,”0″

“21”,”738445″,”9″,””Monitor Hydrofoil Sailboat“||738445”,”The book “Monitor Hydrofoil Sailboat Design in Review” is now available. The cost is $25.00 plus $5.00 S&H in the US. S&H for Europe is $10.00 USD and for Australia is $12.00 USD. Please include mailing address.
Orders are to be made thru: Neil C. Lien
424 Meadow Lane
Evansville, WI 53536
“e”mail address:
phone 608-882-5551″,”2004-11-15″,”Neil C. Lien”,”nopswd”,” “,””,”0″

“22”,”732074″,”9″,”Trimaran stability||732074″,”I have a Sea Pearl trimaran and am looking for ways to reduce weight. The boat is 21′ with a beam of 14′. The center hull is 5’6″. Would it be feasible to replace the amas with foils to provide lift? They would either skim the surface or be out of the water in light air, but would gradually submerge as the wind picked up, eventually balancing the design force from the sails. The center hull will provide adequate form stability at rest. Thank you.”,”2004-11-02″,”Bruce Rowe”,”nopswd”,” “,””,”0″

“23”,”722690″,”9″,”Re: hydro foils for kiteboard||722690″,”Hi Rich,

I am French so excuse me if my English is poor.

Congratulations for your kitesurf performance. I am not sure that the solution to go faster is an hydrofoils system.
The limit speed could be caused by the very strong drift force due to the kite.
If you want to experiment hydrofoils, you have to study very seriously these systems ( I think there is not a good “ready to use” system which can be fitted on a kitesurf )

You can use composite material (fibreglass, carbon fibre, epoxies resin) to make hydrofoils (not only metal). You can buy, for example, long sailboard fins (about 50 cm) to begin tests (symmetrical profiles, but it can be used)

Good luck and contact me if you want more information.

Gerard Delerm
“,”2004-10-13″,”Gerard Delerm”,”nopswd”,” “,””,”0″

“24”,”721718″,”9″,”hydro foils for kiteboard||721718″,”I have recently competed in Weymouth speed week on a kitesurf kite and standard board and have posted a speed of 30.97 knots.
I wish to increase the speed and the only thing I believe is stopping me is the boards resistance. I wish to try out hydrfoils on my board that will lift the board approx 5-10 cm off the surface of the water. I have thoght about using hydrfoils off model boats.
The hydrofoils will have to be made of metal I think. Has anyone got any suggestions of where I could get such things from or made?
The board I am using is 130cm long and 37cm wide.
I look forward to your suggestions
Richard Gowers
Uk”,”2004-10-11″,”Rich Gowers”,”nopswd”,” “,””,”0″

“25”,”715101″,”9″,”T Foils||715101″,”Please send me a sample 2004 newsletter and information about joining your org. I am a small sailboat builder in the USA and I want to learn about T-foils for daggerboards and rudders. To date I know almost nothing, could you recommend a book or books that could teach me about foils. I build a moth boat and the Europe Dinghy (which is a moth boat but has a more advanced sail) Anything you can do to help me get started will be greatly appreciated.
Thank You,
Charles Graves
Graves Little Boatyard
1675 Riahardson Road
Merritt Island, Florida
USA 32952”,”2004-09-27″,”Chas @ Graves Little Boatyard”,”nopswd”,” “,””,”0″

“26”,”699955″,”9″,”catlift foils||699955″,”I don’t know about the catlift foils. I do have some of the Dak foil sections, if you need to see a section profile. Sorry, no plans or complete kits, although they do turn up rarely the internet.”,”2004-08-26″,”Scott Smith”,”nopswd”,” “,””,”0″

“27”,”692423″,”9″,”Re; Catlift information?||692423″,”Gordon,
I can’t say I have heard about the “Catlift” foils but certainly many years ago David A. Keiper (DAK Hydrofoils) developed a “Dak-foil” conversion kit for Hobie 16 catamarans. A photo of a Hobie fitted with such foils appears in the 1978 issue of Jane’s Surface Skimmers. You can find other information related to David’s work on our website. Unfortunately, he passed away a number of years ago.”,”2004-08-10″,”Martin Grimm”,”nopswd”,” “,””,”0″

“28”,”692419″,”9″,”,Re; Catlift information?||692419″,”Gordon”,”2004-08-10″,”Martin Grimm”,”nopswd”,” “,””,”0″

“29”,”685487″,”9″,”Catlift information?||685487″,”Hi,

Does anyone have any information on a device called a Catlift. It can supposedly be attached to a Hobie Cat or Top Cat and lift if up using a small hydrofoil.

Any information you may be able to provide would be appreciated.

Thank you,

Gordon Swift”,”2004-07-27″,”Gordon Swift”,”nopswd”,” “,””,”0″


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PRIOR TO 2002:

International Hydrofoil Society Correspondence Archives…

Hydrofoil Sailboards, Windsurfers, Surfboards
Descriptions, Advice, Sources of Information, and Requests For HelpGo to Posted Messages Bulletin Board (BBS)
See also: The Miller Hydrofoil and <new!> Rich Miller’s 28-page Illustrated Technical Paper on his Hydrofoil Sailboard <new!>

(Last Update 8 Jun 03)



Hydrofoil Surfboard Source

[27 Apr 02] Please forward all inquiries for hydrofoil surfing to — Daniel Elias (

Hydrofoil Windsurfer “Parabolic Design”

[16 Dec 01] I am designing a hydrofoil windsurfer. Your site has been most informative and inspirational. I’ve been in contact with Rich Miller and Gerard Delerm, two of your foiling windsurfing enthusiasts. They’ve been excellent sources of info. My project is finally moving forward. I’ve been trying to design a prototype of a “parabolic wing hydrofoil”. I saw one once in an Industrial Design Magazine six years ago, I liked the idea but have been unsuccessful in locating the necessary technical information to actually create one from scratch. As you’ll see, “Parabolic Hydrofoil” does not a good key-word search make. By Parabolic, I mean as if we took a straight wing form, held it at both ends and bent or bowed it downward into the water. I may be calling the curved wing by the wrong name etc. If you know what I mean and have any leads please contact me. — Eric Dixon, Designer/Builder/Inventor (

Responses…[16 Dec 01] At one time about 25 years ago, I sat through a presentation by a fellow in Seattle who built a tow model of a four-legged hydrofoil using parabolic disks as foils. Since he towed the model with his pleasure craft, I cannot attest to his success since almost anything that is towed can create enough lift to skim on top of the water. I don’t have any more details or who may be of help in tracing down this individual. — Sumiyasu Arima (

[16 Dec 01] I am not familiar with the term parabolic when applied to a hydrofoil. From your description as to what you mean by “parabloc”, it looks like “negative” dihedral. Or am I misinterpreting your statement? I wouldn’t advise using negative dihedral. Although it was used on the tips of the aft foil of PHM (but the center section, which was much larger, had positive dihedral). If anything, you want positive dihedral as a stabilizing effect. Not many airplanes flying around with negative dihedral. Note that there is a hydrofoil document by Gibbs and Cox (although very old) on the AMV CD ROM that has a discussion of effects of dihedral and will tell what you want to know. — John Meyer (

[16 Dec 01] My only comment is that the reason PHM had negative dihedral (anhedral?) on the outboard sections of the aft foil is that the ship had a very high turning rate (degrees/second) when foilborne at design speed and, as a result, in fully coordinated turns, the roll angle of the ship was very large (on the order of 20 degrees as I recall. The negative dihedral was needed to keep the outboard tips of the foil submerged in turns. It also contributed to increased roll control authority at oblique headings in waves. Bill O’Neill could expound on this further, I’m sure. If Eric isn’t looking for such high performance, then positive dihedral is the way to go. — Bebar Mark R NSSC (

[16 Dec 01] I’m not certain that we’re discussing the same concept. If you could go to the Hydrofoil Society’s web site and look in the photo gallery under “what’s next?”, find Luigi Colani’s site. There is a concept model from 1973. It looks like a fish with a push prop. and it has an “external observation/control cabin. This model has two foils each with curving profiles. Another image from the photo gallery shows the ship “Katran-1” from the Volga shipyard, this working vessel has curved foils as well. This is the concept I wish to employ. Where do I find technical info on these types of foils? — Eric Dixon, Designer/Builder/Inventor (

[16 Dec 01] I checked the material you referred to, so now I understand the foil configuration you have been talking about. Such a foil has been referred to as a “Hoop Foil” and was first used by Prof. Oscar Tietjens in 1931. I described this briefly in a draft of a book (Ships That Fly) I put together some years ago. I am attaching the brief discussion here as an Adobe Acrobat file. As to analysis of such a foil, my guess is that you could approximate it as a V-foil with an appropriate dihedral angle and end plates, and go from there. Tom Speer may have looked at this, so I am cc’ing him on this in case he can help. — John Meyer (

[16 Dec 01] I’ve not looked at hoop foils. I agree that they would be somewhat similar to V-foils. My guess is the flatter center section would have less wetted area than the V-foil but possibly more induced drag due to its closer proximity to the surface. Perhaps this is what he had in mind: — Tom Speer, F-24 Ama Deus, website:; email: (

[3 Feb 02] I partly fabricated such parabolic / hoop foils for my own windsurfer once but never finished that project, and earlier last year my windsurfer broke in half so now there is even less reason to finish those hoop foils off. I may reply at some time with more details and photos of my attempt. — Martin Grimm (

Surfboard Hydrofoils

[29 Sep 01] Hello, can you please assist me with information about Laird Hamilton and hydrofoils on surfboards? — Graham East (

Response…[11 Nov 01] A little late but the following url has a photo of Laird Hamilton on a hydrofoil surfboard. That sums up my knowledge — Bill White (

[27 Apr 02] See this website: — Barney C. Black (Please reply via the BBS)

Planing Sailboard

[10 Aug 01] I am from the University of Natal and need assistance on the theory of planing. I am doing a dissertation on the hydrodynamics of planing sailboards. If you have any information on this it would be greatly appreciated. Would a copy of the 1994 Shanghai Conference proceedings be of any use? — Gordon Cook (

Responses…[10 Aug 01] Try the following two websites:

Tom Speer ( website:

[13 Aug 01] Planing theory has been covered in depth by many papers authored by Dan Savitsky at Stevens Institute. “High Speed Small Craft” by Peter Du Cane (Temple Press, London – 1964) is a good reference. The Heller-Jasper paper on this subject is a classic (SNAME, late 50s I believe). Joe Koelbel has also published some good basic small planing craft design guidance – in papers and magazine articles. — Ken Spaulding (

Speed Record

[4 Jan 01] According to the 2000 Guinness Book of World Records, prior to the Yellow Pages ENDEAVOUR gaining the sailing speed record, it was held by a windsurfer. Thierry Bielak of France rode his windsurfer to a speed of 45.34 knots (84.02 km/h or 51.21 mph) at Camargue, France. — Martin Grimm (

Response…[3 Feb 01] A few years ago I saw a photo in a windsurfing shop purporting to show the setting of a windsurfing record of 54+ mph. I can’t recall where the shop was. There is a sailor named Mike Delahanty who runs Gorge Sails (in Washington state, near Hood River) who was the speed champion about that time. Perhaps he could tell you the current situation. — Rich Miller (

Sailboard Success in France

[3 Oct 00] I am French, and I built a homemade sailboard with hydrofoils. I named it “Le Foilboard.” To show my work I made a little home page about it. There is a French version and an English one. — Gérard Delerm ( website:

Hydrofoil Surfboards

[17 Aug 99] Do you know if anyone has worked on hydrofoil surfboards? For waves? I’m looking for info, as I surf, and spend way too much time on crazy ideas, so I don’t want to duplicate someone else’s work. — Doug (

Response…[17 Jan 99] Go to the IHS Links page and look for links to the Miller Hydrofoil Windsurfer and the Air Chair hydrofoil water ski. Those two examples are the closest to what you are talking about.

Small Foil Design Info Wanted

[24 Jul 99] Has anyone that you know of designed or produced a hydrofoil windsurfer? I had the idea to design one, but need to know more about the characteristics of foils, i.e. how much surface area required for x amount of weight and speed over the foil, etc. Any help you could give would be appreciated. — Dr. David Miller (

Hydrofoil Sailboard Design Problem

[14 May 99] I’m a student in my first year in the Ecole Nationale Supérieure des Mines de Paris, And I’m just beginning to work on a project : I’d like to try to make a windsurf board with hydrofoils. I know this is not very original, and I have seen the links to ” Miller hydrofoil,” but I don’t know how to contact him. Moreover, I don’t know which solution I am going to chose (number and type of foils). I’d like to have some advice on this issue. I already have some contact with Hugues de Turckeim, a French shaper who is working on the TECHNIQUES AVANCÉES, the catamaran of Ensta, also a French engineering school. — Yannig-François le Roux (; PARIS

Another Hydrofoil Sailboard Design Problem

[17 May 99] I’m working in the design of a windsurf board with the hydrofoil concept. Do you have some information regarding this idea? — Juan Carlos Santilli. (

Response…[19 May 99] There is magazine article that describes the Miller hydrofoil wind surfer in detail… this description will give you plenty of ideas for your project. Please note that Miller’s design is patented and may not be copied for profit! — Barney C. Black (Please reply via the BBS)



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

The International Hydrofoil Society (IHS) Hydrofoil Correspondance Archives

Updated last August 20, 2006

Hydrofoils: Sailboats

Hydrofoils: Sailboats      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 (

      • )
      • Response…
      • [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 (

        • )
        • Response…
        • [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
        • Responses…
        • [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 (

        • )
        • Response…
        • [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 (

        • )
        • Response…
        • [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]
      Archive; G Baker Hydrofoil MONITOR
      Click below to Open.

      [Date/Time=03-24-2002 – 2:01 AM] [Msgid=237508]
        Archive; Add Hydrofoils to Sailboats
        Click below to Open.
        [Date/Time=03-24-2002 – 12:16 PM]

          Archive; Sailboards, Windsurfers, Surfboard
          Click below to Open

          [Date/Time=03-24-2002 – 3:26 PM]

            Archive; Hydrofoil Racers – Sail/Power
            Click Below to Open this Archive.


            [Date/Time=03-25-2002 – 4:09 PM]

              Flying Keelboat


                    • 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

                      • Doug
                      • 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

                        • Doug,
                        • 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


                            • 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

                                • John
                                • 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
                                  • PS:
                                  • 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


                                      • 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

                                        • There have been several articles on kite sails in the Amateur Yacht Research Society publications. You can get back issues, but you will have to pay for them! It might be possible to find back issues in a library somewhere. There is an index of the articles mentioning kites on the web at:


                                        • .

                                    [Date/Time=07-12-2002 – 7:59 PM]

                                      Name:Barney C Black, [Msgid=281897]
                                      Kite Sail Possibilities

                                          • The leading proponent of kite sails is Dave Culp (email:


                                          • ), who’s also the AYRS webmaster.

                                      [Date/Time=07-12-2002 – 8:01 PM]

                                        Name:Tom Speer, [Msgid=281901]
                                        Kite Sail Possibilities

                                            • Scott
                                            • 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


                                                • 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

                                                  • Thank you for your web site, it’s really a “mine of information”! I have a little hydrofoil boat and a web site: PK Hydroptère de loisirs (Small Hydrofoil Sailboat Built For Only $800.00! ). The address of this site is


                                                  • Fred

                                              [Date/Time=09-14-2002 – 7:57 PM]

                                                Name:Frédéric Monsonnec, [Msgid=309784]
                                                Windrider Rave Top Speeds

                                                    • Mark
                                                    • 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

                                                              • Martin,
                                                              • 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

                                                                • Scott,
                                                                • 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

                                                                  • Jake,
                                                                  • 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

                                                                    • Just thought I should set the record straight about the first ever monofoiler…(well I call it a bi-foiler) Here are some details


                                                                    • We should also not forget the amazing development by Rich Miller of the first true and only “monofoiler”, a high performance sailboard with just one foil in the a unicycle!

                                                                [Date/Time=11-11-2002 – 1:43 AM]

                                                                  Name:Ian Ward, [Msgid=336265]
                                                                  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]
                                                                    Rich Miller`s Hydrofoil Sailboard

                                                                        • On the IHS website there is a reprint of an article about Rich Miller’s hydrofoil sailboard. Go to


                                                                    [Date/Time=11-22-2002 – 4:05 AM]

                                                                      Name:Barney C. Black, [Msgid=341779]
                                                                      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


                                                                              • I’m interested in the e-book on the


                                                                          [Date/Time=12-03-2002 – 5:57 PM]

                                                                            Name:Byron E. Wallin, [Msgid=346366]
                                                                            Hydrofoil Voyager E-Book

                                                                                • The late Dave Keiper’s book

                                                                            Hydrofoil Voyager

                                                                                • , which tells the story of designing and building the hydrofoil


                                                                                • 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


                                                                                • . 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


                                                                                • (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


                                                                                    • 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]
                                                                                      books a nd articles

                                                                                          • Where can I get Bernards Smith’s books and articles? thank you Vincent Browne.

                                                                                      [Date/Time=01-06-2003 – 2:53 PM]

                                                                                        Name:vincent browne, [Msgid=359379]
                                                                                        Re; Re; A Light, Cheap Foiler Dinghy

                                                                                            • Jim,
                                                                                            • 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


                                                                                                  • 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

                                                                                                        • Tony,
                                                                                                        • 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]


                                                                                                            • 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]

                                                                                                                    • Hello,

                                                                                                                    • 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]
                                                                                                                  Hydrofoil Moth Sailing Videos and Stills

                                                                                                                      • You guys might be interested in having a look at the links below. The first link is a collection of six videos showing the hydrofoiled Moth. The second link shows several still photos of the Moth both in and out of the water. Each photo has a good descriptive caption.


                                                                                                                      • Any comments or thoughts are appreciated.

                                                                                                                  [Date/Time=02-24-2003 – 4:39 AM]

                                                                                                                    Name:Rohan Veal, [Msgid=383699]
                                                                                                                    IHS members in So Cal


                                                                                                                          • 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?
                                                                                                                            • Cheers,
                                                                                                                            • Henry

                                                                                                                        [Date/Time=03-19-2003 – 5:21 PM]

                                                                                                                          Name:Henry, [Msgid=399556]
                                                                                                                          hydrofoils? on a sailing cat


                                                                                                                                • 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


                                                                                                                                    • 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

                                                                                                                                        • Paul
                                                                                                                                        • Be Sure to check out our IHS Archives: Posted Messages and Frequently Asked Questions (FAQs) at


                                                                                                                                        • They contain lots of information from earlier converstations on this subject.
                                                                                                                                        • Bill White

                                                                                                                                    [Date/Time=05-28-2003 – 6:39 PM]

                                                                                                                                      Name:Bill White, [Msgid=443265]
                                                                                                                                      Want a ride on Hydrofoil


                                                                                                                                            • 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


                                                                                                                                                  • 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]

                                                                                                                                                    • Thank you very much to Rich Miller for that technical report.
                                                                                                                                                    • Gérard

                                                                                                                                                [Date/Time=06-18-2003 – 6:11 PM]

                                                                                                                                                  Name:Gérard Delerm, [Msgid=455251]
                                                                                                                                                  First Unifoiler Scow Moth


                                                                                                                                                        • 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]
                                                                                                                                                      Re; First Unifoiler Scow Moth

                                                                                                                                                          • Hi Ian,
                                                                                                                                                          • Thank you for your message and congratulations for your work. Can you show somes pictures about your project please ?
                                                                                                                                                          • regards,
                                                                                                                                                          • Gérard

                                                                                                                                                      [Date/Time=11-20-2003 – 1:00 PM]

                                                                                                                                                        Name:Gerard Delerm, [Msgid=547448]
                                                                                                                                                        Historic First Nationals on Foils!


                                                                                                                                                              • 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]
                                                                                                                                                              and a picture !

                                                                                                                                                                  • Rohan Veal sailing “White knuckle express” at the Australian championships in Queensland.

                                                                                                                                                              [Date/Time=01-04-2004 – 12:43 AM]

                                                                                                                                                                Name:John Ilett, [Msgid=566418]
                                                                                                                                                                 Image Attached:  “Rohan-QLD.jpg”   Click Here To View
                                                                                                                                                                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=02-04-2004 – 10:38 AM]

                                                                                                                                                                    Name:glen oldfield, [Msgid=583861]
                                                                                                                                                                    Re; hull choices

                                                                                                                                                                        • Glen,
                                                                                                                                                                        • 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]
                                                                                                                                                                      Re; Re; hull choices

                                                                                                                                                                          • If you are interested in the Moth class of boat fitted with hydrofoils go to this discussion group:

                                                                                                                                                                      [Date/Time=02-18-2004 – 1:41 AM]

                                                                                                                                                                        Name:Ray Vellinga, [Msgid=598753]
                                                                                                                                                                        Speed race in Douarnenez (France)


                                                                                                                                                                              • Hello,
                                                                                                                                                                              • 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]
                                                                                                                                                                            Speed race in Douarnenez (France)

                                                                                                                                                                                • Anne, you have made a good start by posting your message on the IHS bulletin board. If you want to contact some people directly, I could suggest Dr. Sam Bradfield (


                                                                                                                                                                                • ) about his vessel SCAT and Rich Miller (


                                                                                                                                                                                • ) about his hydrofoil sail board (see


                                                                                                                                                                                • ) and some of the people involved in designing or racing hydrofoil moths (see


                                                                                                                                                                                • ). News of your event should be provided to the IHS Newsletter editor John Meyer (


                                                                                                                                                                                • ). Hope this helps.

                                                                                                                                                                            [Date/Time=05-31-2004 – 8:01 AM]

                                                                                                                                                                              Name:Barney C Black, [Msgid=656322]

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