The Rave Hydrofoil

Redefining Fun, Speed & Comfort

by Thom Burns

"A Boat That Flies"

thom1.jpg (7069 bytes)I ordered the boat before it was in production after having sailed the prototypes a couple of times in Florida. I took possession just before Labor Day, which in this part of the world means I had about a month to sail it before being driven off the lake by ol’ man winter. I’ve been holding off writing this review for awhile because I wanted to confidently say what this boat really does. That confidence came together when I attended the first national RAVE hydrofoil clinic held at Jensen Beach, Florida in April.

The entire design team from Hydrosail, the one-design class president and the Wilderness Systems factory point man were there. Ten of us from the clinic, ranging from new buyers to dealers, really learned this boat with most of its bells and whistles.


thomdia2.jpg (8684 bytes)Before diving into the particular characteristics of the Rave let’s review a couple of principles of boatspeed as I understand them.

Most sailboats, including my racing keelboat, bore holes in the water. They are restricted to a top speed by the bow wave they are pushing and towing through the water. This top speed, called hull speed, is usually defined by a formula. This formula is about 1.2 times the square root of the waterline. If a boat has a twenty-five foot waterline the top speed would be 1.2 X 5 = 6 knots. In order to go faster the boat must temporarily increase its waterline or break out of its bow wave by planing over it.

Many keelboats with flatter bottoms, and boats such as scows and planing trimarans, are capable of escapingthomdia1.jpg (8335 bytes) the bow wave and planing. Once on a plane a new speed restriction takes over. This is friction of the boat over the wetted surface; water. The less the wetted surface, or, the more of the boat which is out of the water, the faster the boat will go. This is why sportboats, planing multihulls and even Whitbread 60’s are so fast compared to boats restricted to the bow wave/waterline formula.

The ultimate reduction in wetted surface area is to take the boat completely out of the water. The Rave hydrofoil ultimately reduces wetted surface area to about 22 to 23 square feet. This allows the sailplan to power up the boat to fly to some new theoretical limits imposed by cavitation over the hydrofoil wings (bubbles over the wings). The generally accepted maximum before meeting the cavitation barrier is about 42 knots. The recommended top speed of the Rave is 30 knots.

The complexity of the hydrofoil boat arises from the fact that it sails under all the speed barriers at different times and is able to overcome all but cavitation at different times. See the related article about the 42 NM Miami to Key Largo race which included 10 Raves in their first offshore one design class.


The first thing that impressed me is how extraordinarily well the boat performs as a sailboat when not on foils. It points 40 to 45 degrees to the apparent wind, it tacks on a dime with a self-tacking jib and jibes with ease. You can feel everything that this big powerful rig gives you.

Sailing Flat

Hydrofoil boats need to sail flat to give the wings the proper angle of incidence in the water. Get used to not heeling. This translates into considerable stresses since the sailplan is at its optimum when straight up and down. These stresses are absorbed by the aluminum grid and large cross beam before they are transferred into power and speed.


You have to shake your preconceptions here because you have so much control over your vertical foils which lift you to windward as well as your horizontal foils which hoist the boat clear of the water.

In light winds (4 - 8 knots) you are in a displacement mode. The windward foil is lowered all the way while maintaining your leeward foil at half latch and your rudder foil at half latch. This configuration gives you a lot of lift to windward with minimum drag. It is also one of the few times you’ll heel at all.

In a little more breeze, 9 to 14 knots, you can skim to windward. This is done by taking advantage of the horizontal foils’ lifting power to minimize wetted surface, thus increasing speed to windward. All foils are fully extended.

In yet more breeze, 15 plus knots, you can foil to windward. All foils are fully extended, boat speed is between 14 and 18 knots at approximately 58 to 60 degrees to the apparent wind.

Since the windspeed fluctuates, you may not always be on foils upwind. One efficient method of going upwind is, when you land in the lulls, to trim in and point up to 45 degrees apparent wind. In the puffs fall off a bit and foil to windward at high speed.

Beam Reaching

This is the fastest point of sail and the one which requires the least amount of wind in order to come out of the water on foil. It is not uncommon to bring a Rave up on foil in 8 to 9 knots of wind. As your skill increases you can do flying jibes. This is when the G-forces remind you that its very nice to be captured in a seat.

Broad Reaching

The further downwind you go the slower the boat goes relative to the windspeed and the less stress you put on the boat. In very high winds, if you come off foil without pointing the boat into the wind, you are most vulnerable to nosing the boat over. This is not a violent pitch pole such as in some high speed beach cats, but rather a slow elevator ride to 90 degrees.

Company History

Wilderness Systems began in Andy Zimmerman’s garage in 1985. Andy and his partner, John Sheppard, decided to build a few kayaks for their friends. They had both recently left the furniture industry. Building whitewater kayaks seemed to be more fun.

Despite the fact that the market appeared to be already saturated, it turned out to be more than just fun, it became a great success. They found a niche in building touring kayaks, an item which other companies were not very interested in at the time.

The glitch in the production process was that their hand-made boats were too expensive to produce. So, in 1991 they began the rotational molding process, and applied it to their most popular touring kayak, the Sealution. The result was a high-level performance kayak at almost half the price of the composite version!

The real explosion in sales came when the company, using its own in-house research and development team, created a new line of kayaks for the masses which were stable, inexpensive and easy to paddle. In 1993 the Rascal was born and became an instant hit.

Through the years the company offered several versions of sailing kayaks. When Andy and John teamed up with Jim Brown, creator of the SeaRunner 31 and 37, the WindRider trimaran was created as a new product and WindRider Sailing Trimarans became a new division within the company.

In 1996 the first roto-molded, wave-piercing trimaran left the factory, followed by hundreds more. According to Andy, Wilderness Systems is building over 30,000 small boats a year.


The Rave, like WindRider, is roto molded polyethylene plastic. The raw material is a powder which is poured into a mold then rotated and baked. After the baking process, it takes 20 - 30 minutes for cooling to take place. Then assembly begins. Pieces such as cut-outs and shavings are reground and reused. It is almost a "no waste" process.

The difference between rotational molding manufacturers is primarily how they use the process to build boats. Since polyethylene is a really tough, but relatively soft, pliable material, it gains its structural strength by creating curves, ridges, angles, pegs between layers, etc. The downside of this is that when there is enough plastic in place to deal with the rig loads and hull stresses of sail boats, the boat tends to get "heavy" and the continual flexing may degrade the stress points anyway.

Andy and Wilderness Systems have taken a far superior approach by using the roto molded polyethylene to keep the water out of the boat or to "float the boat." The structural integrity, and tremendous stress loads of the RAVE hydrofoil are taken by an aircraft aluminum tubing structure which is both simple and strong. Even the foils are aluminum and they are supported by a large five inch aluminum crossbeam.

The Foil System

thomfoil.jpg (6008 bytes)The crossbeam and tubing grid support three inverted "T" shaped hydrofoils. The left and right foils have an automatic control arm which adjusts the aileron flap on the back of the wing. This mechanical system controls lift and drag to keep the boat flying evenly through the water at the right depth. Bungee adjusting cords are manually controlled from the cockpit to assist and tune the automatic system. All the foils have three positions: all the way up, all the way down and half-latch. If the boat is moving the foils can be flown to the proper position either up or down.

The stock rudder foil is a neutral, following wing. As the front foils rise, the angle of incidence increases giving the rudder foil lift to raise the boat completely out of the water. When the boat is foil borne the rudder foil returns to near neutral.

The adjustable pitch rudder which I prefer has an aileron on the back of the foil just like the side foils do. You control the lift and drag by moving a control arm on the side of the cockpit. This can assist when becoming foilborne and in tuning the boat when on foil.

The Rig

The large-roach, full-batten mainsail is boomless. After jibing a couple of times at 20 plus knots, it’ll make sense. The jibe is over in a couple of seconds and you are off on the other tack without ever leaving your foil "feet." This is another time when warp speed is added to your sailing vocabulary.

The jib is small and self-tacking. It obviously works very well because the boat tacks on a dime. It’s so much better than comparable sized beach catamarans when tacking that it sets a new standard more akin to quick monohulls.

The roller-furling reacher adds 97 sq. ft. to the already impressive 193 sq. ft. sailplan. The reacher extends the wind range. It is easy to handle and powers up the boat in lighter air. It also allows lower downwind angles when flying on foil. This sail is usually referred to as the screecher by multihull enthusiasts.

The Rave has a rotating aluminum foil-shaped spar with upper and lower shrouds but no backstay. It’s a relatively simple, cost-effective rig which performs well.

The Designers

Dr. Sam Bradfield is a jewel of a person. His passion is sailing fast. He spent eight years at the University of Minnesota in aeronautical engineering before moving back to private industry and eventually to Florida. His expertise in fluid dynamics and advanced wind powered watercraft eventually led to hydrofoils. He designed NF2, Neither Fish Nor Fowl. Nf2 captured and held the Class C world speed sailing record between 1978 and 1982.

Sam and his associates at HydroSail, Inc., Mike McGarry and Tom Haman, set their sights on developing practical applications which could bring hydrofoil sailing and racing to regular folks. They developed foils for wind surfers and retrofits for catamarans. According to Mike, one of the problems with retrofits is that the original boats were not designed to handle the additional loads required to sail flat with hydrofoils. "It’s much easier to design the boat right from scratch."

Sam beamed when I told him that the factory just placed the 150th Rave order since last August. "It has been a really great team effort between the factory and the design team. It wouldn’t have happened without great sacrifice and cooperation between both teams."

How Tough Is Tough?

thom4.jpg (8226 bytes)A friend of mine got his Rave and immediately launched it in North Dakota. He went out and sailed in 30 knot winds without a reef (recommended at 20 knots). He promptly ran aground at a speed of 30 knots. The extent of the damage was a cracked weld where the crossbeam bolts together.

Another Rave owner ran aground in shallow water in Florida going about 28 knots. He broke his foil on the coral. Replacement cost was under $400. Imagine any other boat, power or sail, running aground at these speeds. The owners would be fortunate if the boats weren’t total losses.

I pitched my Rave forward in a 30 plus knot gust by flying the leeward foil out of water at very high speed. This caused the boat to turn dead downwind with all of its sails up and no way to release the main past the shrouds. It was a slow elevator ride up and neither I nor the boat suffered any damage. I'm an advocate of reefing and paying attention to both foils now!


The WindRider Rave is a fun boat to sail in displacement mode. It’s a fine sailboat with good speed and pointing ability. Its large square-toppedthom3.jpg (8407 bytes) main, rotating mast, self-tacking jib, asymmetrical roller furling screecher package and, of course, the foil system allow for plenty of growth for the experienced sailor while novices can successfully "fly" it. Changing gears in a machine like this is almost redefining the term.

Somehow, a scream or hoot escapes from even the most experienced sailors when the craft first comes up on foil. The boat is completely out of the water and you are moving along smoothly at 1.5 to 2.0 times windspeed. Pause for a moment and remember what you’re doing on a conventional or sport boat when its topped out (white knuckles - heeled and hiked to the max). On the Rave you’re comfortably sitting in your seat "flying" your machine.

I get a special charge when powerboats and jet skis try to vector an intercept course to figure out or clock the Rave. A big smile creeps onto my face as I pass every high tech machine in sight often at two or three times their boat speed knowing my checkbook took a minor hit and I didn’t have to coordinate a half dozen crew members.

Possibly the strongest suit this boat has is the ability of a wide range of folks from novice to very experienced to have fun, fly a modest speeds and doing it all from the comfort of your own seat. If you’re looking for a well-designed, innovative, fun, comfortable machine with a growing one design class which is really comfortable for you and your passenger, the Rave may be it.

Thom Burns publishes Northern Breezes. He also reps WindRider Trimarans in eight midwestern states.

For more info: Call 800-311-7245 or 763-542-9707.

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