Design your own BCD model
If you are considering a scratch-built model, then it is reasonable to assume that you are either not a novice and/or are sufficiently fired-up by the idea of Carrier to want to wade straight in. OK - scramble!
As stated earlier on, the emphasis in BCD is on models that are capable of flying very slowly. Not only does this ensure high flight scores, it also maximises the chances of a successful arrested landing. Slow speed capability is therefore the most fundamental requirement of all. This is followed by the requirements of good stalling characteristics, stable free-flight' tendencies when line tension disappears upwind and the model gets left to its own devices (!), reliable and responsive engine throttling and - inevitably - a sensible degree of robustness to cope with the occasional and unavoidable hairy arrival on deck.
The wing of any BCD model is the most important component of all, since it determines the vital slow flying capabilities. The lower the wing loading, the slower the model will generally fly (although the higher the wing loading, the less affected a model will be in windy conditions). However, for a given wing loading, a larger model will always cope with the weight and drag of a set of control lines better than will a small model. Current evidence seems to indicate that models should be built to, or near to, the maximum wing area allowed by the rules of 450 sq.in. Models should also have the minimum wing loading possible, so the usual care should be taken to ensure that general airframe weight is kept as low as possible, commensurate with adequate strength for Carrier activities.
Aerofoil section is probably more important than most Carrier pilots realise, but because there is very little data on suitable sections for use at the Reynolds' Numbers involved (ie: for the aerodynamic conditions prevalent during flight with Carrier model wing sizes and typical slow run airspeeds), most of the sections tried are still guesswork. Some successful aerofoils have been based on the flat bottomed Clark Y or YH types, the Eppler range, some home-brewed Jedelsky sections and even some (very) thick symmetrical sections. This subject still seems to be wide open to interpretation.
It may also be worthwhile to accept the extra weight penalty of a detachable wing for the facility this affords for experimentation with wings of different area, section, plan form, tip shape, surface finish, etc. The possibilities are endless!Slow speed in BCD needs to be kept right on the ragged edge of the stall if the flight is to be ultra competitive. A wing's stalling characteristics can determine how easy it is to recognise the onset of a stall and thereafter to recover from it. This, again, is obviously a major function of the aerofoil section, but of course the technical ignorance noted above still applies! Nevertheless, for any given aerofoil section, it is still possible to produce a better-behaved wing if the tips are provided with some washout, ie: the wing section at the tips is given a few degrees less incidence than the main part of the wing. This avoids tip stalling, where one tip invariably stalls before the other and produces a roll. If this roll is out of the flight circle, that's fine. But if not..... All this said, very few Carrier pilots ever seem to use washout!
Slow flight can also be materially improved by experimenting with variations in leadout position, outboard tip weight and tail weight, as described in the slow run part of the set up section. Large elevators also make it easier to keep the model's nose up when flying close to the stall, and such elevator power can be assisted by the use of aerodynamic balance tabs, ie: the elevators are given portions that project in front of the hinge line. The scale-like requirement of Rule 11 does not extend down to this level of detail, so there is plenty of latitude here.Whilst flying slowly in wind, line tension reaches a minimum during the upwind sector of the flight circle. Although unacceptably low tension is easily countered by simply increasing model speed, this inevitably produces a lower slow run time and a less competitive flight. Some models with large fin/rudder areas will 'weathercock' in such situations, ie: the tail is blown into the circle with the result that the model points out of the circle. This may produce sufficient line tension to maintain control, though if such flight is intended, the control system must have minimal internal friction so that it can operate properly under such conditions. However, most models do not fly like this, probably because pilots are simply too uncomfortable operating at such low line tension.
The matter of a reliable and responsive engine is fundamental to the success of slow flight. Adequate power must be instantly available in order to drag the model out of a stall or to get it off the deck after a missed landing. This is a function of a properly adjusted R/C carburettor and whilst, strictly speaking, it isn't part of model design, no model can be competitive without proper attention to this aspect.
BCD rules
Convert an old model for BCD
Set up and fly BCD
Existing BCD designs
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