Thrush (oz12867)

About this Plan

Thrush. Radio control sport model.

Quote: "A neat, simple, low-wing design to get you into two-wheel landings and aileron flying. Thrush, by Steve Gardner.

THIS AIRPLANE IS the result of a suggestion made by Cliff Penic, a friend and flying buddy of mine. We were both flying small 3-channel models and we had just about stretched them to their limit, so Cliff asked for a model to start aileron training on. We had been impressed by a Senior Falcon (oz6137) in our area, but we couldn't afford a .60 or a .40, or even a .35 needed for a Falcon 56 (oz2424). Since we each had an Enya .19, we decided to go with that engine. We opted to make the design a tailwheel airplane because of our very rough field, and because we like tailwheel flying. The semi-T tail is Cliff's idea and has proven to be very sturdy. The hollow top block is my idea, from my CL stunt days (not to imply that I don't still fly stunt). The wing is also almost pure stunt in construction and is so light, strong, and logical that it is surprising it's not used in more R/C designs.

Cliff built the first Thrush from reduced size drawings - the 'plans' I gave him consisted of two 5' by 7' sheets of note paper. With just these to work with, and bearing in mind the fact that this was his first 4-channel model, his first low-winger, and his first scratch-built model, I think he did an amazing job. And while it shows that he can interpret plans very well, it also proves the model's simplicity.

After the first Thrush had been flown, we found some areas that needed improvement. The most obvious problem was the effectiveness of the rudder on takeoff. The model would immediately swing to the left and soon after it would leap off the ground, which is a good thing because we fly off a one-lane dirt road and it's necessary to clear the roadside weeds. We added some rudder area and fixed the problem on the first try.

Light weight is the model's secret to good performance on a .19, and so far all of our Thrushes have come out at 3 pounds or less. A heavy model with a big engine is not the way to go if you like relaxed flying. Please resist the urge to beef it up unless you are going to use a bigger engine, say, a .29 or a .35.

With an updated version of the model to build, I decided to go all out and do it right since I knew it would fly. This is called saving the silk and dope finish for a proven flyer. I have never had a problem with silk and dope getting heavy, and while an iron-on finish is nice-looking, a good dope finish has something extra, so it is worth the work.

The model has a female molded fiberglass and RAF epoxy resin cowl. Molding cowls is a good way to get replacement cowls, but it is a lot of trouble to make the plug and mold, so I suggest a foam plug and two layers of 6 oz glass cloth and epoxy for the cowl. Melt the foam out with MEK or acetone, and prime the cowl with a primer that will accept dope finishes (otherwise it will peel badly).

To start the airframe itself, I suggest you build the tail first. Pick light, firm wood with no pithiness, and make all the splices before you cut the outlines. Be sure the slot for the stab is parallel to the bottom of the fin between the keys. Don't omit the keys - they are very important. The elevator shows a wire joining the two halves, but a 1/4 in dowel would be just as good. It would merely require a bigger hole in the rudder.

After the tail comes the fuselage. Fuselages are very easy to build straight, but they are also very easy to build crooked. Be very careful about the wood you pick for the sides and be accurate about the centerlines on all the formers. Make up two sides, being very careful to build two right-hand sides so you will have an excuse to build two Thrushes, or maybe one of the two fuselages will come out straight! If one is all you want, and you are sure it will come out straight, then by all means build one right-hand side and one left-hand..."

Thrush, MAN, May 1982.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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