Cartoon by Bill Dean See dimensioned construction plan at end of article



About the designer … Age 20 … Eng. Apprentice at RAE … Member Grange, N. Kent and Kentish Nomads … has been modelling 7 years … also keen on weightlifting, cycling, music … and Wakefields

DEVELOPED as the eighth of a series, known as "Puff-Adders", this model was designed at the beginning of the 1951 season.

The third in the series had placed third in the 1949 I.C.I. Challenge trophy with 3 mins. 48 secs. on a 28 secs. power run, and the 'viper was created with the object of placing even higher in the same event for 1951. It began life with immediate success in the form of a first place in Concours d'Elégance at the All-Herts. Rally, followed by a qualifying flight of 3:20 on a 11 secs. power run.

Next success came with top place in the newly introduced S.M.A.E. Jetex contest, on 2nd September, when after two mediocre flights, the 'viper made a 24:1 ratio flight to gain an easy first. Unfortunately, the model sustained damage during the S.M.A.E. contest, which affected trim so much that the 'viper's I.C.I. Challenge cup performance was far below par. The normal duration is between 90 and 120 secs. on a single 350 charge.

Four identical Fuselage sides are lap joined, then the motor platform is built up, complete with stop and supports and fitted to the diamond fuselage. The sketch shows how jig formers are used to construct the pylon. P.7 and P.5 are fitted first, then P.3, P.4 and P.6 in that order. The tail position can now be cut away, and platform parts fitted, also the birch skid at the nose.

Wing and Tailplane
construction is entirely conventional and needs no explanation. Cover the entire model with Lightweight Modelspan; the original was finished with black fuselage and white surfaces. Total weight should be in the region of five ounces, the C.G. should be at 75 per cent. of the chord from the L.E.

Trim the Vindskreenviper to turn in the same direction for both power and glide. Use extra turn to eliminate any tendency to "stall off the top" and don't forget to use the d/t. For the very best Ratio contest performance, use three 350 charges and allow the first two to burn away before releasing, as the third charge will have the greatest thrust. Happy 'viping…