Amazing "Hydroski-Foil" Air

Boat...it's fast, fast, fast!

• When the countdown reaches zero for face diving or air seepage along ski. Result: exceptional versatility and this hydroski-foil air , one push un- which results in loss of . performance. leashes a 3/4 hp booster engine which Remember, a hydrofoil (similar to an Operating a hydroski-foil air boat suc- jumps the boat up on damp-air with ) produces tremendous lift cessfully can be done most easily by the vapor-trail speeds! The design proved "A- as it speeds along submerged in water. following means: First, adjust forward O.K." over half-foot waves, on land using This is accomplished by a partial separa- ski-foils anywhere, between 14° to 16° wheel attachment, across ice using runner tion of water over the top of the curved angle of attack on water and the stern attachments—with tether line, free- hydrofoil. With water pressure under- ski-foil between 3° and 6°. Second, pivot running, and radio control as well. Most neath the "wing" and a partial vacuum the stern ski-foil straight ahead as you people who have witnessed "damp-air above, tremendous lift is achieved. would a rudder. Clip your tether line flights" of the ski-foil air boat were quite All require some means of leads on the stern and forward strut and inquisitive. adjustment for regulating their running start engine. Hold boat slightly in the Several years ago an article I read about depth in rough and in smooth water. On water and give it a 2 or 3-mph push. the U.S. Navy's hydrofoil spurred large Navy or pleasure boats hydrofoil Under its own power the hydrofoil sec- me into constructing a conventional "foil depth is controlled by patented electronic tions will raise the clear of the water model. Performance tests of my surface- or mechanical devices, but model hydro- at 6-mph; as speed increases to 15-mph, piercing hydrofoil air boat revealed two foil boats are extremely tricky to control the hydrofoil sections break clear of the problems: airborne stability and control. by any means because of their small size water also. The high angle of attack and Hydrofoils which support a model hull and water conditions. After making sev- speed now permit the hydroski sections an inch or two above water require per- eral wood and aluminum hydrofoils, I to support your craft for high-speed skip- fect angular adjustment to prevent sur- combined the hydrofoil and the water planing at approximately 1 3/4 " above water.

Hydro foil/ski (left) is made from 1/16" soft aluminum. Angle adjust- ment and fin attachment is set for free running.

14 American Modeler — October 1962

The engine stand can be 1/4" plywood or 1/16" aluminum reinforced Fifteen hulls (left) with stainless steel at stress points to were tested with more conform with the engine assembly. All than 15 hydrofoil/ski three hydroski-foils are 1/16" soft combinations . . . a aluminum 3-5/8" long by 5-1/8" wide. lengthily process, indeed. Skis are 1" wide and must be stiffened Inventor-author Harold E. lengthwise by riveting or other means to prevent metal fatigue. All hydrofoils Follett (below) holds U.S. measure approximately 13/16" wide. Patent No. 2972974 on Angle of attack for the bow ski-foils may his craft which performs be permanently assembled between 14° like hydrofoil-water ski- to 16°. The stern ski-foil must be ! pivotable for steering and also vertically adjustable for angles from zero to 6°. Other construction details are indicated by the photographs. For clearance above the hull, I suggest mounting an .049 engine high enough to swing a 6-3 prop and an 8-8 prop for a McCoy 29 engine. This development started several years ago during my junior year at Millersville State College, Pennsylvania, while ma- The foregoing description applies for joring in Industrial Arts education. Hours relatively calm water conditions. By .drop- of research were required to pioneer and ping the inclined stern ski-foil to a perfect the hydroskifoil concept. I built horizontal position, the boat will scoot and operated 7 different models using 15 over waves 6" to 1 foot high in open ski and foil combinations powered by 5 water, depending on engine size. The different engines. Two models plus U.S. stern ski-foil submerges itself about 1/2" patent copies of this invention have been under the surface, which stabilizes the studied by officials in the National In- boat, causing it to follow the wave con- ventors Council, Office of Naval Re- tours in rough water at 15 to 20-mph. search, and the Bureau of Ships. Attachments for expanding the versa- If the reader is interested in obtaining tility of the hydroski-foil boat include fins for free running in any predeter- model-size plastic or aluminum hydroski- mined direction, wheels for parking lots, foils, wheels and ice runners, send me a and ice runners for frozen lakes and card expressing your thoughts. This will ponds. These attachments can be added help decide the advisability of having the in a matter of minutes for year 'round hydroski-foil boats mass produced by a operation. It is also possible to adjust toy and hobby manufacturer. Send your steering and speed by radio control. cards to: Harold E. Follett, c/o American Advantages of a hydroski-foil air boat Modeler, 420 Lexington Ave., New York include excellent stability, control, versa- 17, N.Y. tility and a broad engine selection from a .049 to a McCoy 29 engine on the same craft! As to the vapor trail speed mentioned earlier, you can expect over 25- mph from an .049 Thimble-Drome engine with a copy of my 1-1/4 pound boat (which could be made much lighter for Optional McCoy 29 racing competition). With a McCoy 29 power (right) on same engine tests indicate unusually high speeds—between 55 and 88-mph. Another 18" long boat seen advantage of a ski-foil air boat is by- running with .049 on passing floating debris by adjusting the opposite page! Only ski-foils to the inclined position as out- changes needed when lined for smooth water use . . . the ski- shifting from 1/20 to foils climb up and ride over seaweed, 3/4-hp: lighter leaves and small twigs. pontoons for added Materials and specifications for con- struction include a solid balsa wood hull, buoyancy at rest and 18" long, 2-7/8" beam, 1-5/16" high. small steps screwed The cross strut of Honduras mahogany, onto bow ski-foils 16-1/4" x 1-1/2" x 1/4", is mounted at an to prevent "diving" in 8° negative angle to prevent model from rough water. taking off at high speed.