Japp

FIRST PARAGRAPHS OF BUILD ARTICLE:

"A 20-1/2 inch wingspan single-channel radio control model, for .010 - .020 engines. Japp, by Tom Prukner.Although small, 'Japp' has a big performance, don't dare to discard her as a novelty model. Far from it, she is fast and highly aerobatic and because of her small size, always attracts a crowd whenever flown. The prototype, although flown with a Webra Picco single channel pulse proportional outfit, is suitable for other lightweight single channel outfits with small escapements or as a free flight model with the Cox .010 engine.

Nearly all the components can be cut from only two sheets (!) of 1/16 x 3 x 36 in balsa. 1 mm thickness was used in the original but this is not generally obtainable in this country (the prototype was made by a Yugoslavian modeller in Norway). Take great care to position all the components exactly as the illustration on the drawing or all the parts will not fit on. Study the plans carefully and decide which version and engine you are going to use. The Cox TD .010 provided ample power in the original and the integral Cox tank gave a two-minute flight time, quite long enough. if you intend to do aerobatics it's advisable to install the optional stunt tank behind the engine mounting former, with the fuel feed line bypassing the integral tank. For free flight add an external graduated tank to reduce the engine run, as this size of model soon goes OOS.

The prototype construction took some five hours and with the exclusive use of PVA white glue, drying time was longer than anything else. Commence construction with the wing. Note the angled ribs, and boxed leading and trailing edges as used in A/2 glider construction. Cut all the leading edge riblets, the main ribs and root/tip ribs. Pin the lower leading edge sheeting down flat over the plan then glue the front riblets and tip ribs in place. Note that the centre section is flat, this is built separately to the two wing panels. Now glue the 1/16 sheet spar in place, followed by the top sheeting. Add the leading edge strip and a D section structure that forms the front half of the wing panels will result. Leaving the leading edge structure pinned in place, pin the lower trailing edge sheet to the plan, glue the 1/16 x 1/32 strip in place then add the trailing edge top sheeting, having bevelled the rear edge prior to commencing construction.

With both the trailing edge and leading edge in position, glue the angled ribs in place and when dry remove both panels from the plan. Construct the centre section over the plan, sheet the lower surface then add the two piece ribs, followed by the trailing edge structure, dihedral brace, leading edge and top sheet. Block the wing panel tips up 1-3/4 in with the centre section edge level against a square table edge and sand the sheeting to the dihedral angle. Now glue the wing panels to the centre section with 1-3/4 in packing under each tip rib. Cut the tailplane from 1/16 sheet, add cross grain tips and sand smooth.

Cut the fuselage sides, top and bottom and doublers from A1/16 sheets and engine mounting former from 1/16 plywood, Bind the undercarriage in place, cementing well. Glue the fuselage side and bottom doublers in place, then the reinforcing strips to take the place of formers. Glue the two fuselage sides to the engine mounting formers, add cross bracing strips, then when dry cement the bottom in place. Now cement the fuselage top on, followed by the tailplane and fin. Add the nose sheeting around the engine bay and install radio equipment. Note the servo mounting tray, shaped this way for the Webra Picco unit only. Remove the R/C gear and cover the entire model with one coat of 50 per cent thinned clear dope then lightweight tissue all surfaces, including the fuselage. This tissue covering on the fuselage imparts great strength and prevents the sheet splitting with minor knocks. Decorate with bright colours of your choice as an aid to visibility."