MICRO AIRSHOW DOGFIGHTERS

Model Airplane News, Jun 2004 by Keennon, Matthew

One summer a while back, my friend Bill Watson and I were looking for a joint project, and we thought it would be cool to have a pair of semi-aerobatic WW I biplanes with working machinegun lights and sounds so we'd be able to put on entertaining dogfights at the upcoming AMA show.

We wanted our biplanes to be more like toy airplanes than precision scale models, and lights and sounds would make them fun. For simplicity, we made the two models essentially identical. Bill built the airframes by scaling up Walt Mooney's classic peanut-scale S.E.5 plans to around a 15-inch wingspan. But the German plane presented a problem: no German plane looks like an S.E.5. We decided to go with a Pfalz and to "massage" the wing and tail outlines so it would bear some resemblance to the Pfalz. I think it kind of turned out to be a "False Pfalz" in the end, but it's a beautiful model anyway.

We built the models out of balsa and covered them with RA Microlite iron-on covering. The Microlite is like MonoKote but lighter than doped Japanese tissue. The covering makes the bright, blood-red Pfalz look good, and the S.E.5 looks handsome in its scale brown and tan scheme.

To pull off good machine-gun sounds, I spent days tinkering with speakers, foam coffee cups, springs and old tin robot toys. I finally determined that the best system would have a spring-loaded hammer that smacks down on a stiff drum membrane that's enclosed in a box. I geared a tiny 4mm pager motor to drive a cam to lift and release the spring hammer rapidly. The drum membrane had to be thin and stiff to make a nice sharp "pop," so I used fish paper (a stiff, heavy paper used in electronics). Tiny, superbright LEDs hooked up to the flight computer flash alternately at a rate that roughly matches the drum sounds.

Crowds really love our dogfighters; a big cheer goes up each time we fire the machine guns during a demo. The planes can take off, do loops, wingovers and incredibly tight turns. Flying them together is a blast because they are so well-matched in performance.

At the end, we figured we had each spent around 100 hours on the models. Bill mainly did the framing and covering, and I handled the RC equipment, machine-gun drums and other miscellaneous details such as custom-machined props and wheels. Building these models was a labor of love that brought back my memories of building planes in an aeromodeling class at school (Bill and I both learned from the same teacher-but around 10 years apart!). Although the planes are really satisfying to fly, I don't think I'll do this type of project again anytime soon; it's too much work!