Jumbux (oz14163)

About this Plan

Jumbux. Free flight sport model.

Quote: "Full Size Plan for this Parasol Sportster. By E Glyn Hughes.

Jumbux was really designed as a 'scale model' of a free-lance full-size light aircraft, and as such makes a really sweet-natured sport model which is a joy to fly. The original flies with a rather tired old ED Bee up front but any diesel or glow engine from .75 to 1.5 cc may be used. She has proved very stable and prang-resistant in all conditions, so you can confidently get building with the assurance that this is not only the ideal consistent sport-model for those halcyon summer afternoons, but a real all-weather flier! Jumbux is flown on a deserted Lincolnshire beach and it is always windy.

Construction: Fuselage: The first step is to bend the wire pylons and undercarriage struts. Cut out formers B and D from 1/8 ply. Drill 1/16 diameter holes where indicated on the plan and tie the wire struts in position using thread, which should then be well covered with balsa cement.

Build the two sides flat on the board using 1/8 sq balsa and allow them to dry pinned in position to minimise distortion. Use formers B and D as the placing formers and build the rest of the fuselage off the plan. The stringers on the top are all 1/8 sq. Cement the engine formers in position and then do the panelling in 1/8 balsa sheet.

The cockpit coaming should now be cemented in position and covered with two layers of Modelspan. The cockpit opening is cut out when this has been done. The engine cowling is built up from a 1/4 in sheet and carved and sanded while in position. Sandpaper the completed fuselage smooth and add the dowels.

Wings and Tail: Cut out all wing ribs and build the three panels flat on the board. Cut the main spar to the shape shown on the plan. Select three pieces of good quality trailing edge strip and pin them down; also the leading edge and mainspar. Cement all ribs, gussets and wingtips in place. Add the two top spars. Cement together the three panels, incorporating the 2-1/2 in dihedral under each tip. Cover the centre-section with is 1/4 in balsa sheet and carefully sandpaper this part and all joints.

The tailplane is built in a similar manner, flat on the plan. The fin is made from 1/4 in sheet and sanded to the section shown.

Finishing: The original was covered in lightweight Modelspan. Fuselage and fin were red, wings and tail yellow with the name made by cutting out the letters in red tissue and doping them in position on the wings. Three coats of clear dope were applied, and about six coats given to the engine cowling.

Flying: Test glide over long grass adding weight to the tail compartment or nose as required. The original does nice wide left-handed circuits. Use low engine power to start with. A useful trick is to put the propeller on backwards to reduce thrust. (No, it doesn't become a pusher!)"

Supplementary file notes

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