Pee Wit. 1/4A power model.
Quote: "1/4A offers new scope for the experimenter. Here's one viewpoint. Pee Wit by P Gasson.
UNTIL QUITE RECENTLY it had not been possible for English power enthusiasts to enjoy the use of a contest class miniature 1/4A motor. The recent introduction of the Cox Pee Wee 0.3 cc glow motor which is now in abundance in the model shops, has provided the long awaited answer and is fast becoming a favourite.
There is always a thrill to be had in contemplating the miniature and there are many modellers who have for years dreamed of an 18 in fast climbing power job and have had to content themselves with models of at least 24 in span and an engine capacity of more than 1/2 cc. Here is an account of the type of model evolved to meet these requirements and to deal in particular with the layout and type of construction which is considered essential for a model of this size.
To achieve a rapid climb it is always necessary to keep a careful check on the weight. Particular attention must always be paid to this requirement and the outside limit for a model of this type is 2-1/2 oz although by careful attention to wood selection it is not difficult to keep this down to 1-3/4 oz. With a 1 oz motor weight this allows only 3/4 oz for the airframe. The fact that over 50 per cent of the total weight is concentrated in the motor unit imposes a considerable limitation upon the choice of layout.
The most obvious effect is to bring the CG well forward which means that the wings must be situated almost over the engine. R Annenberg solved this problem by using swept forward wings, thus bringing the wing centre of pressure forward whilst keeping the root section behind the engine (see Fig. 1). In smaller models such as described here, a swept forward wing produces structural difficulties if tip flutter during the fast climb is to be avoided. For this reason a straight leading edge is recommended and the CG problem solved by making the moment arm longer than usual (about 4-5 mean chords), which also allows the pylon to be lower than that originally employed by Annenberg (see Fig. 2).
With this style of model it has been standard practice to mount the wing (but not the tail) outside the slip-stream, by which means it is claimed that the layout is less critical to tail trimming adjustments (see Fig. 3). Dihedral need not be excessive, 3 in per foot of semi-span being sufficient for most layouts. If too much dihedral is employed then Dutch rolling will occur and consequently the glide will. not be good. If, on the other hand, too little is allowed then the model will not be able to make full use of the high power because of its wish to side slip..."
Pee Wit, Aeromodeller, February 1961.
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