Sawdust (oz1724)

About this Plan

Sawdust. Single channel RC model, for 1.5cc engines. A Chriss Foss design, from Christmas 1968 Aeromodeller.

Quote: "SOME will consider it functional, others may think it ugly (curse them!) but the fact remains that it works. To design a single channel power model for the sole purpose of flying, functionability (that's a good word) has to take precedence over aesthetics, so nuts to a cowled engine, fancy cabin, wheel spats, concealed wing fixings and the like. Sawdust is the combination of three essential components, wing, tail and fuselage, in that order.

As there is nothing worse than having a fuselage only just large enough to squeeze the radio in, Sawdust has been made adequately large to accommodate all the necessary gubbins, which are, at the same time, con-fined within the extremities of the wing mount for both structural and practical reasons.

The equipment used in the original is RCS Guidance System Mk.3, with an AM 15 motor up at the heavy end to provide the necessary pull - both truly British inventions which have made so many trouble-free flying hours possible.

As I have a certain dislike for flying sessions being terminated by structural failure, Sawdust is so constructed as to virtually eliminate this possibility. In retrospection of over a year of consistent flying, totalling some 20 airborne hours, the only damage that comes to mind is a bent tailplane and broken engine mount. The latter was the result of fitting a deadly pointed spinner, which subsequently buried itself in the ground on landing (?) whipping the motor out at the same time. Lesson learnt is not to use a spinner with a paxolin mount.

I initially attempted to fly Sawdust using a Conquest 'bang-bang' escapement, but soon discovered that this rather unpredictable form of control resulted in more digging than flying. Thus, after a series of vicious encounters with terra firma which resulted in little more than clogging the motor with a load of Sussex crud, I reverted to a more predictable and sensible form of control, namely, the Elmic Compact selective escapement. This made life a lot easier - no more dithering around wondering which is the next signal (inevitably it turns out to be the wrong one!) for all one has to remember is that one press is right and two is left, and that's not asking too much. Nevertheless, I didn't chuck the Conquest escapement away, but instead converted it to operate the throttle using the 'quick blip' method. After having found this extra control invaluable, I am surprised that so few cone-button' flyers make use of it. For only an ounce of extra weight, folks, you can land the model when you wish, without waiting for the tank to run dry, make low passes (oh, yes!) and even try Limbo.

Assemble the wing LE, TE and ribs of both panels, then raise each tip 1-1/4 in and cement in ply dihedral braces followed by the twos 1/8 in sheet centre ribs. Add top spar and fill in the LE and TE at the centre section. Lift the wing off the building board and add bottom spar, 4 in. gussets, vertical webbing, centre sheeting top and bottom, and 1/4 sheet tips. Inset 16 s.w.g. wire into the T.E. and secure with nylon wrapping. Finally, cover the wing with either silk or lightweight nylon.

Cement the 1/8 in sheet nose doublers to both fuselage sides. Assemble ply formers 1 and 5 and engine bearers (already drilled) on to one of the sides, and when positioned correctly, glue the other side into place - Evostik Resin W or similar is recommended for this operation. When completely set,cement - adjustments may be necessary here to suit the type of clunk tank used, and should be arranged so that the tank is a push fit into the bay when completed..."

Update 12/04/2016: Article pages, text & pics added, thank to RFJ.

Supplementary file notes

Article pages, text & pics.

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