THE SECONDWANKELPowered

Aircraft. . .

ABOUT THE AUTHORStan Tonkin's (EAA 20801) first venture in aviation was three model air-

planes he had on display at the "Century of Progress" World's Fair in1933. Started in aviation in 1936, A & E Licensed in 1940. Two years inGeorgia, Civilian Flight Schools, three years in Air Force, Flight Engineeron B-17's and B-24's. Past 30 years in General Aviation. FAA ratings heldare A & P, Commercial SMEL, Instrument and Instructor.

By Stan Tonkin (EAA 20801)9S 114 Aero Dr.

Naperville, III. 60540(Pnotos by the Author)

S,SOMETIME BACK, i read inSPORT AVIATION where someonesaid, "Sooner or later someone is go-ing to come up with a Wankel pow-ered light plane."

Well, we came up with a flyingWankel plane in June of 1970. Webeing the owner and designer, Mr.Stan Corcoran of New Lennox, 111.Stan is an old timer in the designand manufacturing of gliders and ul-tra light aircraft. The other part of"we" was yours truly, the builder.

This aircraft was an all metal, poprivet, biplane with a 30 ft. span. Ithad flaps on both wings and no land-ing gear just one wheel and brakein the keel, as any good glider orsailplane designer would have.

Long before the aircraft was fin-ished, weeks of research and develop-ment work went into the powerplaneinstallationand reduction drive. First,a mock-up of the fuselage sectionadjacent to the engine mount wasbuilt. This was an exact duplicate,as to material, rivet spacing, engineattach points, etc. Then, this mock-upwas affixed to a platform on wheelsand could be moved outdoors for en-gine test runs. The mock-up was totest engine mount rubbers, vibration,engine attach points, mount fatigue,rivet shear or loosening also, towork out as many bugs as possiblebefore we moved out to the airport,as we did our building in a shop intown.

Our first try was with the enginemounted low on the top deck of thefuselage with the pusher propellermounted two feet above the engine.This arrangement didn't work out, asit proved difficult to dampen the whipin the drive belts. Next, we raisedthe engine up close to the prop andused short belts. With this mock-upwe tried many arrangements of en-gine mounts, drive belts, exhauststacks, muffler arrangements and nu-merous propellers. Speaking of pro-30 MARCH 1974

The all metal biplane used as a test bed for the Wankel engine installation.The little machine was designed by Stan Corcoran of New Lennox, Illinoisand built by Stan Tonkin.

pellers, Mr. Corcoran once manu-factured props for drones duringWorld War II. Our test props weremade with fiber-glass epoxy.

The powerplant for this airplanewas a Sachs Wankel of 20 hp., thesame model as used in snowmobiles.It was mounted as a pusher. The 40inch prop was driven by 4 matched"V" belts going between a crankshaftpulley and a bearing box mounting aprop pulley on top of the engine. With-in 20 minutes the reduction pulleysand gear could be removed and asmaller prop attached to the crank-shaft for a direct drive version. Ofthe two, the reduction drive gave bet-ter performance and the noise levelwas cut down considerably. This en-gine had a muffler also. The pullcable for starting was mounted onthe cockpit floor.

FAA gave N-11RC a license onJune 22, 1970.

Although the airplane flew well,it was under-powered. The most se-vere problem was blisters on the handfrom pulling the rope starter as thesmall wood prop was not much of aflywheel. Later the Sachs was re-placed with a Kawasaki 436cc engine.

R. S. Corcoran and the rotary enginedbiplane blast off the second Wan-kel powered aircraft to fly, accordingto the author. Can anyone dispute hisclaim?

This engine had more power and anelectric starter. Many successfulflights were made with this power-plant.

By the way, the first Wankel pow-ered aircraft was the "Q-Star" builtby Lockheed Aircraft.

Side view of the Sachs Wankel in-stallation. The belt reduction system,carb and muffler are visible from thisangle.

Another angle of the Sachs.

This shot provides the perspective to make one realize how small the SachsWankel really is even including the belt drive reduction unit. The allmetal airframe of N-11RC is interesting, also.

Rear view of the air cooled SachsWankel. This engine has been usedsuccessfully for a number of yearsin snowmobiles without the fan-fare new auto rotaries are now re-ceiving.

SPORT AVIATION 31