Bonzo (oz11293)

About this Plan

Bonzo. Control line stunt model, for Fox .35 engine.

Quote: "Scale-Like BONZO Stunter, by Paul Plecan.

If U-control stunt is heading in a new direction, it is definitely toward scale, particularly since Dave Hemstrought's PT-19 Stunter (oz6451) appeared in the Sept 1960 issue of American Modeler. (This Fairchild ukie stunt plane, incidentally, is being re-presented in the 1965 AM Annual so newer aerobatic recruits will know of it.) Subsequent designs have veered toward scale even when not patterned after any particular airplane, with cockpit details (plus a pilot) appearing in most nowadays. So our Bonzo is a natural, considering the high sustained interest shown in Goodyear Midget racers for nearly 20 years.

In profile, our Bonzo is entirely scale; only the horizontal surfaces are puffed up to Stunt proportions. After all, how far can one deviate from the 'norm' in Stunt? All the top contest winners (without exception) possess similar nose / tail moments, areas, airfoils and CG placement - only the profiles vary. It is the author's contention that Steve Wittman has a lot of our top stunt model designers beat at their own game! To obtain the desired overall fuselage length of 40 in, the side view was scaled at 2-1/4 in to 1 ft - it is practically a 'ringer' for the Nobler (oz6212), which needs no introduction to Stunt afficionados.

Our model tipped the scales at 40 ounces, ready to fly. Wing area is 520 square inches, a bit more than the Nobler's 503 (which is quoted as 550 on kit plans and in many technical discussions). Control linkage is orthodox; there's nothing tricky about this ship. Even the paint job is simple - all yellow, with blue spinner, LG struts, wheel pants (if used) and numbering. Engine is mounted in sidewinder fashion so that it is concealed in the scale cowl bump on the right side of the fuselage.

As one can see, the ducting system for engine cooling air has been thoroughly worked out. Left air inlet feeds into a 1/2" hole in fuselage side, directing a cooling blast of air at the crankcase (yes, it gets hot there). Since hot air expands, we provide a %" hole near the aft end of the engine compartment; this leads to an outlet on the bottom of cowl bump, where a hole is apt to least upset scale effect. Right cowl air inlet is in perfect position for feeding fresh cooling air to engine cyl-inder and intake port. A large outlet aft of cylinder dumps hot air down through bottom of cowl bump. A hole just aft of the cylinder head draws off hot air from this critical area and dumps it downstream from main outlet. Original was about 5/16 in diameter; it could be 1/2 in or more. On the Fox 35X we used, exhaust stack was in an ideal position; facing down, it disgorges the gunk stream away from the model. Neat, huh?

So try our Bonzo Stunter. Cut out all wing parts first; the 24 ribs are identical. TE capping strip is 1/16 x 3/4 in, be sure it is straight. If not, cut from 1/16 sheet balsa with aid of a metal T-square or yardstick. Splicing will not be necessary on spanwise members if 48 in balsa is used (available from Sig dealers). If splices are required with standard 36 in stock, make them as far away from center of wing as possible. Line up pieces accurately and overlap ends, making cut through both pieces with aid of metal straight-edge, employing a fresh X-Acto blade for a clean cut.

Pin TE to wing plan, cement all ribs in place, then add top TE capping piece. Rear 1/4 x 1/4 TE strip is cemented in place next. Use 1/2 in sq strip to block up front ends of ribs at this stage, so wing is supported at the front. Any strip will do, as long as each rib has its rear section flat on work-bench for a 'true' assembly. Cement and pin LE (1/4 sq) into notches in ribs. Ditto for 1/4 in sq top spar. Sheet covering goes on next. Do not use fast-drying cement at this stage..."

Bonzo, American Modeler, November/December 1964.

Direct submission to Outerzone.

Update 27/06/2019: Added article, thanks to RFJ.

Supplementary file notes

Article.

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