Plan file details
Sopwith Pup - Free flight scale gas model, for diesel motors up to 1cc. WWI biplane fighter. Pendulum controlled rudder shown, and sprung undercarriage. Scale is 1/8.
Quote: "Neither gone nor forgotten this great aircraft survives the ravages of time - a Pup still flies today. And now, in many places the atmosphere of the 'old days' will again be recaptured by the flying of this superb power model whose flight faithfully follows that of the original machine.
Following in the tradition of Bagley and his popular Bishop's Nieuport I7C, the model 'Pup' described in the pages of this article is equipped with the same built-in stability device, the automatic 'pendulum' rudder which makes light of one of the most difficult features of true scale model design.
Powered with a Frog 100 diesel, but will fly with any engine of similar capacity, it was tested with a .9cc Clan engine which proved to be lacking in sufficient power. Simplicity and strength were the keynotes in the design, the undercarriage being sprung in the true scale fashion ie with rubber band shock absorbers. The wings and engine mounting can knock off in the event of a crash.
Fuselage. The fuselage is built as a conical slab-sided box structure of 1/8 inch square hard balsa. Commence by building the two sides flat on the plan, afterwards joining them together with the various top formers, cross spacers, etc. Then bend the centre section struts to the shape shown on the plan from 18 swg wire and bind in place. Next, add the side formers, stringers and sheet. The cowling is carved out of hard balsa in two halves the top half being plugged into the lower half which is cemented to the 1/8 inch ply front former, which is in turn held to the fuselage by means of strong rubber bands. The engine is bolted to this former, 5 degree sidethrust being obtained by packing with washers.
Wings. First pin down TE and LE to the plan. The mainspars will have to be packed up with pieces of sheet to allow for the undereamber, when this has been done add the ribs, then build up the tips with 1/16 x 3/16 inch hard balsa, when dry steam 1/16 inch square bamboo to shape and cement on. Next, make the 20 swg wire strut lugs to shape shown on plan, then bind and cement firmly in place at an angle allowing for the stagger and dihedral of the wings..."