Firecracker (oz11245)

 

Firecracker - plan thumbnail image

About this Plan

Firecracker (Keith Rider R-4). Radio control pylon racer model.

Quote: "Upon deciding to build a formula FAI class racer different from the enlarged Formula I configurations normally used, it seemed logical to investigate the era of the thirties, since some of the most interesting racing airplanes ever designed were produced at that time. After considering the good and bad features of various racing designs of this vintage, the Keith Rider R-4 design was my choice.

Popularly known as the Firecracker, this airplane was selected because of its low wing, short, wide-tread landing gear, large root chord, long fuselage and inverted inline engine. The low wing gives easy access to the radio gear, The low, wide-tread landing gear results in easy takeoff and landing. The large root chord allows a thin percentage wing for low drag, and the long fuselage results in a 'groovy' airplane even though the tail surfaces are scale area. The inverted engine installation allows a clean, low drag front end.

The selection of this configuration turned out to be a good one as it placed in all the 1970 FAI races in our area including second at the Spokane Internats - in spite of its being the pilot's first year of racing. It handles and maneuvers so well that it has placed in several scale contests even though it is not, strictly speaking a scale model.

Construction Light weight and straight, true flying surfaces are two important features to stress in the construction of this model. The original was very flyable even though it weighed 6 lbs. A 5 lb version has just been completed and it is definitely faster. Extra weight will not cause any handling problems, but it will slow the plane down in the turns.

To insure good stall and handling characteristics with this type of wing, it is important to build it straight and true with tip wash-out as shown on the plans. When cutting the wing cores, use a foam block with at least one flat side. The core should be cut with the proper washout relative to the flat surfaces. The resulting block can then be used as a jig when sheeting the wing. In making the cutting templates, the tip should be made about 1/16 oversize to compensate for the foam melting that occurs with such a highly tapered wing.

The aileron linkage, tip ribs and landing gear blocks should be installed before sheeting the wing. The wing is covered with 1/16 balsa sheets which should be glued ahead of time. The wing can be sheeted in the foam jig as shown on the plans using a water-base contact cement such as Core Grip or Sig Core Bond. When finished, the sheeting at the tip can be pulled together and glued, and the leading and trailing edges added. Use straight pieces to prevent warps. Any gaps around the edge of the tips can be filled with Sig Epoxolite.

The ailerons should be cut out at this point and edged with balsa as shown on the plans, and the leading and trailing edges sanded to shape. Add the 1/8 plywood aileron doubler (shown on the plans) for the control arm. Blind nuts will later make the installation easier.

The easiest way to join the wing halves is cutting the dihedral angle carefully on a power saw then gluing the two halves together with Titebond or white glue..."

Firecracker, American Aircraft Modeler, January 1971.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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Firecracker - completed model photo

Datafile:

003.jpg
003.jpg

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Scaling

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