Full Size Printed Plan 1/2 A Proto Control Line Speed STILETTO Wingspan 14” Engine .049


Listing is for Full Size Printed Plans and Building Article


Unique appearance and superior streamlining ore achieved on this 1/2 A Proto racer with simple shaft extension. Idea would work on any size speed model.



Wingspan 14”          

Engine .049 

Richard La Conte

THE PROTOSPEED MODEL, by defini­tion. is supposed to resemble a full size airplane, but in order to achieve good aerodynamic design, these models now are looking more like-to quote the Con­test Director of the '69 Nats-"Hell Razors on Wheels." The Stiletto is in­tended as a step toward the original in­tent of the Proto rules and as an effi­cient aerodynamic design.

Several areas or design improvement were explored. When it is reworked the 049 engine because of its size, does not respond with large increases in power and some engines seem to be at their peak in stock condition. Since few gains are to be made in engine modifications the next logical place for improvement is in aerodynamic design beginning with the propeller.

Little information is available on model propeller performance. except that such propellers are very inefficient when compared with full size counterparts and that the airflow is extremely tur­bulent and forms a spiral around the fuselage. To obtain maximum use from the prop wash the maximum Cross sectional area of the fuselage is best placed as far aft of the propeller as possible. In present designs, the forward location of the engine puts the maximum cross sectional area just aft of the propeller and any attempt to reduce the area is limited by engine size. Also, the abrupt vertical rise of the cowling does an ef­fective job of disrupting the prop wash before it can stabilize its flow.

With the amid ship location of the Stiletto's engine, this design succeeds in obtaining the desirable aft location of the maximum cross-sectional area and at the same time creates a sleek and realistic looking model. Other benefits obtained from this engine location are being able to use larger intake ducts for the carburetor and cooling and of in­terest to stunt enthusiasts-a reduced rotational moment of inertia due to the larger mass of the engine being placed near the aerodynamic center of the wing. This results in an airplane that is high­ly responsive to the controls.

Now comes the question does the amid ship location of the engine increase the performance  A 1967 prototype used a Cox Space Hopper engine which had given consistent Proto speed runs of 64 to 68 mph under W.A.M. rules in Cali­fornia. A 12-in. minimum wingspan and no minimum area were specified. The prototype, built to AMA specifications, weighed a heavy 81/4 oz. Several drive systems were tried, and the Stiletto is the design which finally evolved.

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