Convert an old model for BCD
What's the best type of model to use?
Well, almost any old model will do, but if you have a choice, the best configurations are as follows:
- Wing area of about 300 square inches minimum. This gives the model at least a reasonable slow flying ability. Areas of over 450 sq.in., however, are not permitted (Rule 1).
- Wing thickness of about 10% chord or greater. This gives the model reasonable low speed lift characteristics. The aerofoil section is not important at this stage, although a lifting section may perform better than a symmetrical one if you have the luxury of a choice.
- Your model must have an undercarriage. Fuselage-mounted undercarriage is usually stronger and therefore more preferable than wing-mounted, since carrier landings can be very heavy indeed!
- Your model should have a fuselage. This means that the tailplane will be separate from the wing and will therefore provide smooth control during flight. A fuselage also means that the model can be made to look like a Carrier aircraft so that you also get the 'scale' bonus points. Profile fuselages are undoubtedly the best type to use: small alterations in profile are simple and quick; arrester hook attachment is also very straightforward.
- Engine size should be between about .25 and .40 cu in. This will provide a sensible amount of power at high speed, low speed stall recoveries and overshoots.
A very wide range of aircraft will fit the specification shown above. If you have a choice, pick a model that you don't mind putting the occasional dent in, as the deck landing itself can sometimes be a bit dramatic!
If you're converting a model which conforms to the requirements above, you'll only need to add a throttled engine, the 3-line throttle control system and an arrester hook. It is even possible to use something like an old combat wing, although you'll have a much more suitable model if you throw away the engine pod and elevator and construct a separate fuselage and tail for it. Do this simply by copying the fuselage and tailplane of the BCD design that has a wing chord dimension closest to your own wing.
Once you've chosen an old model, remove the existing 2-line control system and fit your new 3-line system after chosing one from the selection shown and described in Section 4. Whilst some of the systems are very sophisticated, remember that this model is merely a trial. If you want to minimise the work involved, use the simplest arrangement possible - the 'bellcrank-on-bellcrank' system. See the section on 3-line control systems. Mount this externally. This may not look so tidy as an internal location, but it makes installation, maintenance and repair tremendously easier.
The arrester hook should be no longer than 1/3 of your fuselage length (Rule 3). The shape, position and method of mounting should be copied from whichever model in most closely resembles yours in construction. Profile fuselaged models are obviously easier for hook installation than are full fuselages, and this may well influence your choice of existing models. Whilst most of the model designs shown on this site use hook latches to keep the hook up until needed, the amount of work to install a latch in a full fuselage can be considerable. Since the rules do not require latches, the hook can actually be left to dangle free for simplicity. It will simply drag along the deck during take off and remain down throughout the entire flight.
The disadvantages of this are that a deployed hook during the fast run looks untidy and - slightly more importantly - that a dangling hook during the slow run reduces the vertical airspace available beneath the model for stall recovery. Anyway, your choice - but remember, as before, that the model is merely a trial!If the model has an outboard side-mounted motor, you can improve slow speed line tension by angling the motor outwards using wedges under the engine's mounting lugs. Carrier motors must also be fitted with an effective silencer (Rule 3). Some manufacturers' standard silencers are enormous and, in side-mounted engines, can project down below the nose so far that they are liable to be ripped off even in the gentlest of landings. Not only can this completely destroy the silencer, it can also easily damage the crankcase at the silencer attachment point as well. You will be much better off if you fit a dustbin silencer. Not only is this type much more compact and far less likely to be damaged, it is also much lighter than a normal silencer.
To improve your model's slow speed performance and line tension, it's also useful to glue the rudder to an outboard angle of about 20 degrees. If it's possible to fix some kind of external hardpoint to both the outboard tip and the tail, to which lead weights can be screwed, then such weights can be varied to 'tune' the low speed performance of the model. See the slow run in Set up and Fly section for an explanation of this. In any event, make sure that the outboard wing's tip weight is about 2oz to start with. If your wing has flaps, these must be permanently disconnected from the elevator pushrod and thereafter either glued up, made adjustable (this is legal, as long as they cannot move during flight) or locked out of action altogether.Finally, you can gain an extra 10 points (see Rule 11) simply by repainting the model in a suitable naval colour scheme. Don't make it complicated, though. All white, all light grey or all navy blue is quite acceptable, providing that the vast expanse of new paint is relieved by some appropriate national insignias.
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BCD Rules
Set up and fly BCD
Existing BCD designs
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