Pawprint (oz9037)

About this Plan

Pawprint. Free flight sport model.

Quote: "Back in another lifetime, modeling-wise, there was a magazine named Air Trails. This was in the Golden Decade of aeromodeling, the years from 1945 to 1955. Air Trails featured two full-size pull-out plans each month, and in one issue (1/49 for those interested) there appeared a little sport F/F model called Pleasair (oz8999). Designed for CO2 power, the model was necessarily lightly built and perhaps a shade fragile for the sport purpose. Nevertheless, several friends and I built multiple Pleasairs and enjoyed them greatly.

Our Pawprint (the name is a wordplay derived from its first powerplant, a PAW diesel) doesn't resemble the Pleasair in the least, either in appearance or structure, but the intent is the same. This time, however, a few key changes have been made to enhance durability and reduce or eliminate hazards during trimming.

Construction is simple and rugged. A sport model must survive all manner of abuse, so wood sizes are generous. I recall a friend of mine in England remarking: I have noticed that a slightly heavier model will always fly better than a lighter, broken one.

Ease of trimming. I feel that a sport model's initial flights need to be kept to a very moderate pace. While this isn't true for contest pylon models, where full-power-and-a-short-run are the safest, the sport model's first flight ought to be scarcely more than an extended hand-glide. Until now, the typical .049 sport F/F model has ranged from 32 to 36 inch span. At this size, it is vastly over-powered for its purpose. To make matters worse, the cabin shapes that modelers like in a sport model are not as inherently stable and forgiving as the pylon layout. The result is that trimming becomes a sweaty process and dangerous to the model, with disaster never far away. Rapid rate of climb is not desirable in a model of this type. On the contrary, slow altitude gain gives more time to appreciate the plane in flight and allows longer engine runs.

The remedy is simple: make the model bigger. The Pawprint is 44 inch span. Suitable power can range from a .5cc (Dart or PAW 03) through a Mills .75, and on up to a .049; even a lcc if it's "elderly". But take care, not all engines are created equal. An ED Bee from 1947 has probably half, or less, of the power of a modern MP Jet of the same type and size. Some of today's very powerful glow .049s will require patient trimming since they don't readily throttle back. Often, a good answer to this is to put the prop on backwards at first. An even better answer might be to install a diesel.

Diesels have long been favored for sport F/F models (and F/F scale) due to their willingness to run at slow speeds and on large props. This helps enormously on those first flights. Then later, a PAW 80 or similar unit, chugging away on an 8-4 prop that a typical .049 glow won't look at, will give hours of fun..."

Pawprint, Flying Models, August 2011.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction