Washboard (oz3148)

About this Plan

Washboard. Delta free flight sportster model for .5cc motors. Model Aircraft, July 1958.

Quote: "A free flight delta sportster design for 0.5 cc motors. Washboard, by Colin Read.

THIS model was designed early in 1955 after a series of delta wing models had been built to develop a design capable of stable flights even in rough weather con-ditions. To make Washboard stable, sharply upswept wing tips are used, together with a staggered dihedral break to provide the necessary wash-out; the airfoil section is a normal flat bottom one, but using an inverted trailing edge to give a reflex section.

Construction is commenced by laying flat on the building board the 1/4 in sheet leading edge, 3/16 in main-spar and trailing edge (note the reverse section) then cementing the ribs in place firmly (double cementing is advised throughout). When dry, remove from the building board and add the upper 1/8 in sq spar, then separate the wing tips where shown and cut to fit the main wing, raising the tips tips 5 in. When both tips are firmly in place cement the dihedral bracing gussets in position as detailed on the drawing.

Formers 1 and 1A are now added, the whole of the leading edge and front formers then being sanded to shape (before covering with 1/16 in sheet), to provide smooth contours as shown. Lastly, the centre section is covered, top and bottom, and the 1/2 in sq wing tips added, after which the whole framework is sanded to a smooth finish.

The elevons, upper and lower fins, cut from 1/16 in and 3/32 in medium sheet respectively, are covered with tissue (doped on) and cemented in place after the model is covered and doped. The elevons are fixed in place with pieces of aluminium, and spring loaded with a small rubber band onto the stops which are cemented underneath the wing and elevons.

The engine used on the original was a Frog 50, radial mounted, but any power unit of 0.5 cc will provide sufficient power, but an increase in downthrust will be necessary if a more powerful engine is used.

It may be of interest that the original Washboard, recovered and redecorated, gained second place in the Unorthodox Section Concours d'elegance at the 1957 All-Britain Rally; the qualifying flight was 53 seconds."

Supplementary file notes

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