Greetings all!
I would like to express encouragement to Dave Carlson for his work on FoilCats. Granted that there are some commercial products out there (rave, trifoiler etc) and that they may require a sustained windrange to perform ...but i still like the versatility concept of a foil retrofit. (attach 'em when the wind allows and either retract or leave 'em off when it doesn't) Please keep up the work ....and all i can say on his note "...perhaps it will soon live again as a source for Foilcat Kits!" is YES,please!!!

May everyone get good wind!

I think Foiling is a blast. Do I like the idea of combination sailing well off foils but foiling with the same (light) boat in good air? You bet.

I have foiled on and lifted 550 pound foil boats (Rave), and feel they are overbuilt- with 250 feet of sheets and adjustment lines (My friend Hollis Caffee has one and he sails a new Taipan 4.9 instead). The Ketterman trifoiler is light but takes 3 men and a boy to arrange and move around (My other friend Jennifer has one and she sails a Taipan 4.9 instead). They have never raced them against each other despite living 150 miles apart: That was a really big thread here 3 years ago.

So- GO combi-hydrofoil boats! Maybe we don't have enough crazee Frenchmen living in the USA who like to go fast on sailboats.

Dave:

Any chance of fitting foils to my Tiki when under power? Are they stable enough (for motoring)?

The problem with most foilers is the use of mechanisms to adjust the foils' angle of atack. They need excessive tuning and lines.

The Catri uses the boat's atitude instead and this simplifies the setup. It is a patented solution, though.

Luiz

Where can you learn about this stuff? ie books, sites etc.?

I think the best place to start searching is the International Hydrofoil Society. They have lists of books, sites, publications, etc.

www.foils.org

The Catri sites are also very interesting:

US Catri: www.aegeanmarine.com
Germany: www.catrimarine.de
Brazil: www.multicascos.com
Latvia: www.catrigroup.com

Luiz

Some clarification: The Rave weighs 400 lbs. The weight of the pilot in a race is a required 165 lbs. Any lighter skipper is obligated to carry weight near the pilot's seat to make up the difference.

There is no experience on the water like foiling but the weight of the foils will slow you down while hullborne.

Regarding Hollis, he bought his Taipan so that he could race more often. The Rave crowd doesn't particularly like being restricted to a windward-leeward course so it was very difficult to have a good turnout for racing. When you have a boat that foils, who cares whose the fastest beating or running?

Liked this version -
Spitfire
http://marine.bdg.com.au/spitfire12.html

The main problem with foilers is --?

getting the proper angle and adjustment ,

lifting --crashing off the foils -

very slow speeds until lift occurs .

How similar and effective are just the angled through hull boards comparitively ? --would an asymetrical through hull angled -canted board be potentially as effective .?

thanks
Carl

Tiki looks a bit weighty for this treatment: Weight is the foiler's enemy! But Williwaw was a 31 feet long trimaran, a homebuilt plywood foiler that made it to the South Pacific and back. I reckon its aluminum foils were substantial enough.

I agree with Carl that the 12 meter Spitfire is lively and lovely- and costs US$200,000. Hence my interest in retrofitting beach cats to fly.
W. Richard and other large French tris of the 1970s were heavy and when fitted with angled daggerboards, lots of stress was generated. So- jamming, leaks and breakage of the wooden foils resulted. This boat is in Ft. Pierce and the foils were sawed off years ago. Perhaps Catri shows the way.

The Rave trifoiler uses 3 inverted T-foils, each with an adjustable flap for attitude control, and lots of trailing arms, bungees and lines. Lately they changed to a joystick for each flap, suggesting a need for 4 hands.

In contrast I want to use surface piercing foils that are tapered, flying higher on a narrower foil to reduce drag and avoid flaps. The angled foil is fixed, and the righting force of the lee foil forces the rig to stay nearly horizontal. Not much heeling, as heeling force is converted into speed even in puffs.

Crashing? Yes loss of lift means crashing, but with surface piercing foils, the cat crashes horizontally, from 20 down to 12, then she lifts and you are off again accelerating to 20 in a few seconds. I have never pitchpoled in 4 years of development, even when running off downwind feeling like a speedboat: the long bows out in front keep this from happening. Even in good-sized whitecaps when it is blowing 25+, and everybody has gone home (except for the Hobie 16s)!

Thanks Dave

Great work on the foilers .

4 extra hands or an on board comp/ system to control foil pitch and flap control and amount of lift does seem a bit expensive

Agree with the fixed concept , are asymetric canted foils -boards the answer ,-or are the sym. sections best .

What is the lattest development on foil section -

found this ,but it seems dated already .
http://www.foils.org/design.htm

The foiler tris seem to be making progress
http://www.cat-alist.com/headlines/hydroptere.htm

fantastic machines.,

JOYSTICKS: THERE'S ONLY ONE ON THE RAVE
Jeez, Dave! You gotta stop looking at Hollis' and Doran's boats and applying what they've modified to a stock factory Rave. Hollis Caffee did install a joystick for each flap on the amas but that was his own mod; not the factory's. The Rave still is manufactured with one joystick that controls only the RUDDER flap and that is there to give an assist to an earlier liftoff.

CRASHING: IT HAPPENS ONCE
Regarding crashing, on the Rave it's kind of like a bicycle. If you keep falling over on a bicycle you may tend to blame the design. Training wheels are not necessary once you learn the technique. The fact is that you simply have to learn how to stay up without crashing. When first learning to fly you can literally fly the boat out of the water and most of us have. No big deal. Just add more bungee tension next time (see next topic below). Once you fall down you learn not to do that again. Kinda like a bike.

LEVELING: IT'S AUTOMATIC. NO JOYSTICKS NECESSARY
The Rave has an automatic leveling system for the flaps port and starboard. The leveling system works with a bungee connected to a wand that rides on the surface of the water. The wand is connected to the ama's flaps. There is a bungee to starboard wand and one to port. The wands, port and starboard, ride the water's surface and adjust the flaps automatically. The bungees are there to keep the wands from flying up from the surface. The two bungees are led to the control deck in front of the pilot through a camcleat for each bungee. So, bottom line, the Rave has an automatic leveling system and once you learn how much tension to apply, your hands are free. No joysticks necessary. No crashing impending.

THE ONLY JOYSTICK YOU NEED:
The joystick, only one, is connected to the rudder flap. You adjust bow attitude with this stick.

SO WHO HAS ALL THOSE JOYSTICKS?
Hollis Caffee and Doran Oster, both in the Gainesville, FLA area, did away with the automatic leveling (the wands) and added a stick to each flap, hence, the boat needs an octopus to fly the thing. Hollis and Doran Oster made the mod in order to have manual control while racing in their quest for improvement. For long hauls they readily admit that this system would be very tiring. I liken it to fuel injection on a car and would not think of ditching it in favor of having someone manually spit gasoline into each hole in rapid succession would be an improvement.

JUST LIKE AN AIRPLANE:
I think the pilots reading this will see that flying a Rave is just like flying an airplane: one control for the port and starboard wing flaps and a joystick for controlling the rudder.

STEERING THE CRAFT:
You steer the Rave with foot pedals connected to cables to the rudder.

DURABILITY:
Unlike the production foiler that begins with an "H" the Rave is bullet proof and can fly on many points of sail. It's too bad that the Hobie Tri-foiler was based on early technology and has proven limited and fragile. It gave a bad name to foilers in general. It's also too bad that the Rave was marketed (if you can call it that) by a kayak company and it's message never reached the intended multihull market.

Regarding your last statement, I've had the doors blown off my twice by foiling raves out here (might have been the same guy two different times) and I'd die to try one out, but as far as practicality, it really doesn't sit well, considering beaching that thing with the foils looks dangerous, and the draft when hullborne looks treacherous for the waters around here.

Tom Speer has posted a lot on the International Hydrofoil Society website, and is a real aeronautical engineer working for a large aircraft company in Seattle. A cut from the site (that Carl says looks dated) is copied below.
Eppler 817 and Speer's foil shape H105 are PROBABLY best for hydrofoil sailing: These are low rise, low bucket shapes that should not ventilate readily at our speeds. Caveats: Supercavitating foils and/or air injection are for high-powered motor-driven vessels only. Sharp entry symmetrical foils like the NACA0012 series ventilate readily. I know this for a fact!

Source of Foil Profiles (Tom Speer answer)
[3 May 01] I am part of a group of students engineers that studies l'Hydroptère. I look for the view of the profile EPPLER817 that we used to realize the foil of our maquette. In particular, I do not find the curves Cz and Cx incident to this fine profile. I am therefore very appreciative if you could help me in this area) -- Elie Daguet ([email protected])

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

Eppler E817(E817)
Eppler E818(E818)
Eppler E836(E836)
Eppler E837(E837)
Eppler E838(E838)
Eppler E874(E874)
Eppler E904(E904)
Eppler E908(E908)
Speer H105(H105)
The most complete database of section coordinates is at the UIUC Airfoil Data Site. With the coordinates from there and XFOIL (http://raphael.mit.edu/xfoil/), one can generate the data for precisely the conditions desired. -- Tom Speer ([email protected]); website: www.tspeer.com; fax: +1 206 878 5269

The Rave's draft is about 6" with the foils retracted. There is a "half-latch" position that has about a 2' draft and the fully extended position is a little shy of 6'. The foils have to be to be fully extended for flight.

Beaching the Rave is like any other beach multihull. Without leaving your seat you can retract the foils on the amas up to half latch and head toward the beach. As you approach retract the amas foils fully and leave the rudder at half latch. Then, you can hop out into 2' of water or simply fully retract the rudder and come up onto the beach.

Alternatively, because the boat will sit up at half or full latch you can hop out of the boat, pull it up into shallow water and then extend the foils down to half latch. That supports the hulls above water in it's "drydock" position.

Recovery onto the trailer is simple from a beach launch. I pull the boat up onto the beach a bit and then raise the boat up onto fully extended foils. Then, I back my trailer underneath the "suspended" boat, get out of the car and let the boat down on the trailer and drive onto the hard to disassemble. You can do the same at a launch but the bottom can be slippery sometimes. The hardest part of recovery happens when you are at a beach where you cannot get the trailer backed fully under the boat. Then, you may have to lift the bows up onto the trailer. It's 400 lbs and sometimes needs an extra hand simply because the boat is 17' wide and a bit unwieldy when shoving from just one spot on the boat.

I regularly hit at least 25+ (mph) and very often 30+ when there's a breeze. One has to have an airhorn to alert the jetski's when you want to pass them.

man I gotta get a ride on one of those sometime!

Jake,
Maybe the wind will be up enough the day before this year's R.T.I. to have some fun.

Carl,

Your concerns are probably the right ones. I certainly don't know enough to give complete and definitive answers, but here are some things to think about. I learned them slowly from the Catri designer.

1) Getting the proper angle and adjustment is a big problem. The Catri solution was using the boat's atitude as angle of attack adjustment. The rear foils work much like airplanes rear wings to keep the boat atitude where the designer wants it to be. The side effect is that pitchpoling is very unlikely. This - and other - solutions are patented.

2) Lifting and crashing is another problem. The boat needs additional energy for lifting (thus extra foil surface and drag) and has to get read of the potential energy orderly when landing, otherwise it crashes. He got read of this problem designing the foils for 90% lift only. The Catri never lifts entirely out of the water and the remaining wetted surface is a planing surface, with minimal drag. The top speed is slightly lower, but the foils can be shorter, the drag smaller and crashing is not a concern at all.

3) Very slow speeds before lift occurs: This is due to foil's drag and the additional energy to lift the boat, especially when automatic angle of attack regulation mechanisms are present. In the Catri this problem is reduced mostly using rear foils that stay out of the water in low speed and by the absence of regulation mechanisms taking energy from the boat. The designer also raised the rudder foil - it is near the surface, where it is supposed to steal energy from the rear wave. Also, thru hull canted foils can be retracted in low speeds, reducing the drag but still providing enough horizontal lift because they are asymetrical.

4) I believe that angled thru hull foils are less effective then inverted T or L shaped foils in a test tank. The advantage of canted thru hull foils is that (as demonstrated by Bruce - hence the name Bruce foils) they maintain the stability as speed increases. Also, it is impossible to reduce the working area of an inverted T or L shaped foil, but it is easy to partially retract an inclined daggerboard.
For this reason (reducing drag), inverted T or L shaped foils tend to be more symetrical and use active angle of attack regulations to increase lift, while a canted daggerboard can be more agressively asymetric.

By the way, the Spitfire's foils are canted but not thru hull as in the Catri. This means that ventilation is more likely to happen. It seems to be one of Hydroptere's problems - it is shown usin many "fences" in some photos and less in others. They seem to ignore Bill Roberts solution of canting the foils forward.

Cheers,
Luiz

My lifting foils and strut foils are canted forward to reduce the effect of ventilation. Bill Roberts has often raked boards forwards on big cats, it seems. NOTE: If foils are raked back, introduced air is quickly propagated down the foil onto the lifting area...which is not what you want.
Hollis Caffee told me today at the Gulf Coast A-class Championships said he may run his Rave in the Miami-Key Largo race again this year..last time there was lots of weed in Biscayne Bay from an east wind....which foilers do not want either!
PS: Woody Cope snaked away another big win. Way to Do, ButWheat!

Where can you go for a test drive on a Foil cat?