Sopwith Pup (oz14522)

About this Plan

Sopwith Pup. Radio control scale model WWI biplane, for electric power with geared Speed 400 motor. Wingspan 31-1/3 in, wing area 360 sq in.

Direct submission to Outerzone.

Quote: "As I write this, it’s been over 24 years since I drew up and built this Sopwith Pup model. I’d rather tell you what I definitely remember about it and not try to stretch the facts. I will say it was a very pretty model in the air, stable and easy to fly (once I increased the dihedral), and an absolute sweetie on a grass runway.

I built the Pup to use a Speed 400 with an Olympic gearbox. Thanks to the gearbox’s distinctly oval pinion gear, the gearbox made a rhythmic rumbling sound, especially at low throttle, giving a very realistic sound when making low passes and approaches (Yes, I have heard real WWI type radial engines, as I lived less than a two-hour drive from Old Rhinebeck Aerodrome).

The model is classic stick construction, and it really looked good with Litespan covering. Originally, I planned to use Cmdr Dunning’s colors, from his historic (but, sadly, ill-fated) landing aboard HMS Furious. To save weight (remember, this was a Speed 400 and NiCAD model!), I didn’t do any painting, nor did I use fabric dye on the Litespan.

I used white Litespan for the white parts of the roundels and for the rudder. I cut the blue and red markings from craft-store tissue paper. Dope the tissue to the Litespan with dope thinned 50/50, spray it with rubbing alcohol to shrink it, then finish with a coat of un-thinned clear dope.

I maidened the Pup without ailerons, and, as I soon discovered, without enough dihedral for the rudder to turn the model effectively. I wound up having to do several loops before I was able to keep the model from flying into a tree... happily, full up and full rudder was enough to drift the model away from that tree! So, if you don’t add ailerons, DO keep the dihedral at least as per the plans.

I did mold the engine cowling from a pop bottle, using a balsa plug and a heat gun. In fact, I molded a cowling, then shrank a second cowling over that to ensure the cowling was strong enough to survive grass field landings.

Finally, if you can’t find realistic wheels AND you’re flying off grass, you can do what I did – laminate balsa over light ply discs, chuck the sandwich into a drill and sand in a shallow center cone and the dummy tires. I don’t recommend wheels made this way for pavement, but they work fine on grass and only need the occasional black paint touchup."

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