Crackerjack (oz9269)

About this Plan

Crackerjack. Radio control aerobatic sport model for .40 power and 4 channels.

Quote: "Crackerjack started out as just another aeroplane, as I had not built anything for weeks. In fact, however, it turned out to be virtually a smaller version of my Something Special (oz9245). If you spend as much time as I do leaning over a drawing board, it is only natural to doodle aeroplanes - especially if one is bored or has a problem. In doing this, I find that occasionally a shape will appear that I really like, and one of these was Crackerjack.

If you like your models to be fast, fun and easy on the eye, then this is for you. The following notes are more a sequence of events than complete building instructions, as reckon you will have built a few models if you are going to build this one.

CONSTRUCTION: Wings 'n things: The wing is built in one piece, inverted, on the building board. The top surface being flat, dihedral is formed by the wing taper.

Fit the top spar (1/2 x 1/8 in spruce, spliced up from two pieces) to the board, packed up on the line shown with scrap 3/8 strip. Add the ribs, checking their alignment by their centre lines, noting that the section varies, giving built-in washout. Fit the bottom spar, leading edge, false leading edge at the centre section, gussets and riblets.

Making up the four wing skins from 3 in plus 4 in wide 1/16 sheet, shaping then to the line shown. Sand them well before fitting, glue in place and leave to dry well, before removing the wing from the building board.

After removing from the board, add the following: 1/4 in hardwood dowel, servo box sides, 1/2 in sheet fillers at bolt positions, 3/8 in sheet reinforcement at cable exit points, as well as outer cable. Fit the 1/16 ply brace at the centre section after cutting away the centre of centre-rib W1 to clear the servo. Now fit the upper skins. Shape the leading edge, fit the tip blocks and sand them to final shape. Cut out the ailerons, trim back the aileron leading edges, fit lin. blocks for the horn. Face the wing trailing edges and aileron leading edges with 3/32 sheet.

My ailerons are film-hinged; if you prefer to use mylar or similar standard hinges, soft blocks should be fitted to ailerons and wing at the hinge positions. The aileron horns have to be made from paxolin or Formica, as commercial horns of this shape seem to be unobtainable, so far as I have been able to ascertain. The shape is, of course, re-quired to provide the requisite movement with top hinging.

Fuselage and tail bits: One left and one right hand side of the fuselage are made up from 3/16 medium grade sheet, with 1/16 ply doublers attached using contact-adhesive, forming the curve in the sides (plan view) at the same time by rolling the doublers on..."

Crackerjack, Radio Modeller, January 1979.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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