Cap 230 (oz15336)

About this Plan

Cap 230. Radio control scale model. Wingspan 45 in, for 25 to 40 engines.

Quote: "Your Free Pull-Out Plan. CAP 230. Easy to build, highly aerobatic, 45 in span model for 25 to 40 engines and four function radio. Designed by David Boddington.

IT IS EASY TO SEE why the CAP 21 has been such a popular choice as an R/C scale model. The full size is highly aerobatic but it retains ideal model proportions with a reasonably long nose and tail movement and very generous tail surface areas. Wings feature a straight planform taper, 'sawn-off' wing tips and an aileron/flap arrangement which allows the use of conventional inboard ailerons or strip ailerons without too much departure from scale.

The fuselage is basically a box structure with the corners rounded off and a curved section rear decking; the engine cowling (housing a Lycombing 200) is wide enough to hide away the cylinder of engines to most model scales.

Kit manufacturers throughout the world have appreciated the potential of the CAP 21 for modelling purposes and not surprisingly the market has been flooded with models of this neat gallic aerobat. If I see another example of the Eric Muller / Louis Pena 001 aircraft, with its tinted and reference marked (aerobatic manoeuvres) canopy and crossed national flags on the rudder, I think I will go mad. No, it is not difficult to account for the success of this design in R/C model terms, it is relatively easy to build and certainly has a good flight performance. Perhaps it is a little surprising that it has been chosen for larger models with GRP fuselages where the construction methods permit more voluptuous fuselage shapes without additional difficulties.

Less well known than the 'Vingt-et-un' is another CAP derivative, produced by Avions Mudry, and titled the CAP 230. Retaining the general proportions of the 21 it has sufficient changes from its parent to make it an attractive alternative and the variations of colour schemes also add variety. The most obvious change is the 'Zlin' style rudder, with its pointed lower rear end, but there are a number of more subtle differences.

Starting at the front end, the engine cowling shape is quite different when viewed from the front, air intakes being positive shaped openings rather than the oval shaped hole around the spinner of the 21 prototype. Transition to the spinner on the top of the cowl is also more defined.

Wings are essentially similar but the undercarriage mounting is further inboard. this gives the modeller the option of fixing the legs to the fuselage, with a small wing cut-out, or to the wing itself. Wing to fuselage fairings, only at the rear, are more angular and extend further back. A one piece, side hinged, cockpit canopy is fitted (also used on some of the other CAP designs). The prototype 230 was flown without wheel spats. but these were fitted to production versions. 'Spade' aileron balances and twin exhaust pipe which exit at the lower rear edge of the cowl are other external differences between the 230 and earlier versions of the 21. So if you are looking for more of the same. with minor differences, have a go at the CAP 230.

Construction: Although I am a confirmed 'Balsa-basher' I have to admit that the wings of the model do cry out for veneered-foam construction.

Having heard that the full size aerofoil (near straight surfaces from about 25% chord rearwards) did not translate too well in model form I decided not to tempt fate by following this scale line - the same applies to Ken Bink's Extra 300 and the Su26 models. With the straight taper wing planform and 'scale' strip ailerons - half of the length are flaps on the real 230 - there are no problems in making veneered foam wing panels, the 'sawn-off" tips also make life easy. Quoted dihedral is two degrees so put your root and tip templates central on the foam block and cut the root to an angle of 88 degrees.

I eventually selected a standard NACA symmetrical aerofoil for the root, transforming to an NACA 23015 section at the tip to minimise the risk of tip stalling. You could also add a couple of degrees of washout to give enhanced upright flight stability, but remember that the inverted flying may suffer as a result.

If you prefer to build a traditional construction wing you will have to form two sets of wing ribs by the sandwich method. I would suggest that you only taper the spars and leading edge on the top sides so that they can be pinned direct to the building board. Slot the ribs into position. remembering to set the root rib at the correct dihedral angle (template shown). Sheet the top of the wing and leave to set thoroughly before removing from the board. Trim down the lower edges of the spars and add the bottom sheeting. Glue the centre section trailing edge to the rear spar. fitting in the aileron torque rod and tube at the same time, and spot cement the aileron strip. Sand the wing panels to the correct profiles.

Both the built-up and veneered foam wing panels can be joined by using a three inch strip of glass cloth and resin. When the wings are joined cut away the front centre section and add the new front reinforcement and dowels..."

Direct submission to Outerzone.

Update 6/6/2024: Replaced article file with complete version, thanks to RFJ.

Update 13/6/2024: Added article part 2 (Prototype Parade pages), thanks to Graham.

Supplementary file notes

Article.
Article (part 2).

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