Excerpt from an article in Multihulls Magazine, March/April 1988…

By Martti J. Palmquist

The idea was not exactly born in a vacuum void of experiences, or events, or insights that, eventually, led to this invention. Growing up in Finland, I was fortunate that my father had a cabinet making shop where I could (and did) build my own toys, including model sailboats, ships, as well as free-flight rubber band and rocket powered model airplanes. At age 9, with the help of my father, I build a 2 man kayak with sail sewn out of (God forbid) my mother’s new linen bed sheets. A couple of years later, the mast and sail ended up on an ice boat of my own design. Only 15 minutes after launching it the boat was destroyed in a bad accident. Limping off the ice, with just the mast and the sail under my arm, I felt very good about the knowledge that I had sailed at more than twice the wind speed.

My mother, a school teacher and librarian, used to bring books she knew would interest me. I read about ramjets, rockets, jet engines, aerodynamics, boat and aircraft design. I still remember a time when I sat in between the spokes of a dining room chair turned upside-down to simulate the cockpit of a biplane, and acting out the instructions in a how-to book on acrobatic flight maneuvers.

Skiing and skating occupied much of my free time during the long winters. And, in pursuit of speed, the lessons of air resistance and crictional characteristics of different snow and ice conditions were not lost on me. Attepting to ski across a steaming pile of horse manure at 40 miles per hour can result in a powerful and lasting insight into the mechanics of pitchpoling.

Soon after immigrating to the USA, I had an opportunity to go waterskiing for the first time. Having graduated from trick skis (banana peels) in a couple of hours, I discovered during spin practice that the hydrodynamic resistance of the skis was reduced, drastically, whenever the skis were transverse to the motion (that’s why they are called banana peels). I pondered the reason for the disappearance of the drag, but didn’t really understand it until later when I was building a sailplane, and reviewing the basic aerodynamics. There it was, in black and white. Increasing the aspect ratio (span/cord) of a lifting surface increases the lift/drag ratio. A simple calculation showed that turning the skis sideways could produce a 60-fold reduction in drag. Some years later I flew a number of passengers to Silver Springs, Florida, which is famous for its glass-bottom boat rides. To kill time, I boarded one of the boats. The captain had taken an extra long cigarette break and was behind schedule. In order to catch up, he gunned the motor between points of interest. The glass bottom would turn opaque with tiny bubbles rolling against the glass. I looked closer and inside some of the larger bubbles I could see a smaller bubble furiously spinning around the circumference of the larger bubble. Knowing that the same molecular property that is responsible for the surface tension is what transmits the hydrodynamic drag in the first place, and seeing the bubbles’ tension, brought realization that the bubbles were interfering…forming a roller-bearing barrier to transmittal of drag, thus solving the other half of the “banana peel” effect.

On my layovers at Fort Laurderdale, I tried out Hobie Cats and got irreversibly hooked on speed sailing. I soon purchased a 16’ G-Cat and proceeded to push it to the outside of the envelope. The pitch-polings that resulted were spectacular! I particularly remember one February day at Lake Lanier…the winds were blowing at 20-25 knots and building'; the air was brisk and the spray was numbing. I knew there was no way to make this boat sail faster - unless - I could rig a “banana peel” to lift the lee pontoon - it would have to be suspended to skim over the tops of the waves, and it would have to have its center of lift forward of the center of gravity to keep the bow from dipping. The wind was gusting to 35 knots and I was beginning to doubt the wisdom of being out alone. In order to return to the beach, I eased the traveller, turned slightly off beam, hiked fully aft and flat over the water on the wire, and played the mainsheet and the rudders, to keep the lee bow just inches above the surface of the mounting waves. The windward hull was alternately free and barely slicing. “If I had a hydroplaning wing with some buoyancy-producing lift, in opposition to the total effort of the sail, I wouldn’t even need the other hull.” I had misjudged the motion of the waves and saw the forward trampoline disappear in a thunderous spray. I got a hard jolt in the trapeze jacket and felt myself going ballistic. In midair I tried, mentally, to prepare for the cold dunking with an underlying feeling that this really wasn’t necessary. I could have prevented the bow from dipping with an airplane -type elevator control.

That incident became the point of culmination I began making sketches of possible configurations and, in less than a year, formulated the design principles, completed a patent search, and filed the application.

A US Patent #4,635,577 was issued to me on January 13, 1987 for Hydroplaning Wing Sailing Craft or Wingmaran (a trademark of Aero Marine Technology), as I now call it.

To simplify the explanation of the operating principle of the wingmaran, I have prepared a sketch of the forces acting upon it, as viewed from below the surface. The total effort of the sail acts approximately parallel to the line from the center of gravity of the boat to the center of the hydroplaning lift and buoyancy of the wing, so that the wing always squarely opposes both the heeling moment and the forward pitching movement of the sail. To accomplish this, the wing must have forward sweep and an inverted gull wing shape. The wing also needs to be flexible, so that some of the energy absorbed when planing up a wave, can be reduced on the backside. At the same time, it must have torsional rigidity to prevent tuck. Experiments have shown that a wedge-shaped wing foil produces the most lift and buoyancy, and the least resistance when slicing through crested waves.

When this boat is pushed towards its limits, it rocks up on its wing tip. The center of lift moves outward and forward, due to the inverted gull wing shape and the forward sweep of the wing, while the hull is just barely skimming the tops of the waves. The hull drag is reduced, because there is less wetted surface, the wing drag decrease being inversely proportional to the square of the velocity. In this condition, the boat is free to accelerate without appreciable increase in drag. Theoretically, it should be possible to fly the hull if the inverted “V” rudders are used, to simultaneously steer and control the pitch and the angle of attack of the wing. I say ‘theoretically” because I have not been able to achieve this condition, and, therefore, do not yet know the ultimate speed value.

In one of my experiments I used an 18’ G-Cat hull and found that it cavitated at around 20 knots, loosing its lateral resistance. I am now using a non-cavitating hull, a centerboard with a supercavitating foil.

I have drawn comparative graphs of the drag characteristics of a catamaran and a trimaran, and the same for a Wingmaran. it is not a quantitative study, for I don’t have access to computer modeling equipment. However, it should be fairly accurate regarding trend. The dashed portion of the Wingmaran wing drag curve shows how moving the crew weight or, ‘an active ballast system’, on a larger boat, can reduce the wing drag as the boat speed is nursing past the hump speed of the wing.

In the evolution of wind-driven vehicles, where does the Wingmaran’s ultimate performance lie? The lift/drag ratio of a high-performance sailplane, converted to nautical terms, equates to 50 times wind speed. Of course, its equivalent of lateral resistance is the frictionless force of gravity. An iceboat, or a land yacht, can easily attain five times the wind speed. The ultimate catamaran performance seems to fall around twice the wind speed. I predict that the Wingmaran, when fully developed, will reach between 2.5 and 3 times the wind speed. To achieve such performance, lightness and strength of construction will play a major role, supported by development in super-cavitating foils for rudders and centerboard.

The upwind and downwind performance of the wingmaran is roughly on par with cats and tris and in light and shifty winds, it is at a disadvantage. However, in strong winds, anywhere within 40º either side of beam, the Wingmaran will show its mettle.

Martti’s home-built glider which won 1St place at the Oshkosh Air show (circa 1968)

Wingmaran Prototype #5, 1988