Supermarine Sparrow II (oz9616)

About this Plan

Supermarine Sparrow II. Scoolyard scale parasol model.

Quote: "Warm weather is on its way, and it's not too early to start building for those calm summer mornings and evenings. An easy to build schoolyard scale R/C model is hard to beat for real pleasure and minimum investment. In the October 1982 issue of FM I laid out the basis for designing and building successful schoolyard scale models and described three versions of an ideal scale subject - the Supermarine Sparrow II. We present here the 48 inch span, .049 powered version which uses two or three channels for rudder, elevator, and optional motor control.

The full size Sparrow II was a classic British parasol, designed in 1924 by Supermarine Aircraft's young designer RJ Mitchell; the same Mitchell who was destined to eventually design one of the most famous aircraft of all time - the Spitfire. The Sparrow was originally built as a biplane for competition in the 1924 Lympne trials for light two-seat aircraft. Chronic engine troubles, however, kept it out of the trials. It was modified to a parasol monoplane in 1926 and the reliable 36hp Bristol Cherub III, two cyclinder engine was substituted for the earlier Blackburn Thrush powerplant. The Sparrow II weighed in at 963 pounds at take-off and had a top speed of only 65mph and a minimum, stalling speed of 30mph.

My model was sized to carry a light weight two or three channel radio and .049 engine at a wing loading of no more than 8 ounces per square foot. Since the wing area is 375 square inches, our all-up target weight was 20 ounces. I lucked out and the prototype came in under the target weight, including one ounce nose ballast in the form of a dummy Cox .049 cylinder.

The weight of the model breaks down as follows: I used a Royal Van-guard, four channel receiver, three World Engines micro S-22 servos, and a 225 mAh battery pack. This comes to about 5-1/2oz for the radio. A 2-1/2oz Cox Dragonfly .049 R/C engine is used for power. The complete airframe, including ballast, weighs a little over 11 ounces, for a total ready-to-fly weight of 19 ounces. If you follow the construction shown on the plans, you can easily make the 20 ounce target, and at that weight, the Sparrow II is an outstanding and realistic flyer.

Since the Sparrow is a simple and fairly conventional design, it is suitable for a relative newcomer to modeling. Use light to medium weight balsa throughout, and resist the temptation to beef up or add structure. The only hard woods used are spruce longerons, ply dihedral braces, and several plywood fuselage formers. I find it easier in this type model to build aluminum tubes into the fuselage where the cabane and landing gear will be attached. This way the wire parts can be bent and fitted and then removed until the fuselage is covered and painted. After final assembly, they are locked in place with a drop of cyanoacrylate glue..."

Supermarine Sparrow, Flying Models, May 1984.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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