Originally Posted by
jaymen
A bit late on my response, but we have found the thrust angle you set the engine at does determine the elevator trim. At the "stunt" setting, you do not need as much up elevator when compared to the beginner thrust position. PT-19s seem to fly at a pretty high angle of attack due to the decalage/incidence relationship between the wing and stab, so it's normal to see what your picture shows. Most Cox plastic planes were similar in that they were best at doing gentle climbs and dives, nothing really sudden or radical, and you needed to initiate a climb well in advance to avoid a "ground swell". The all balsa slab wing trainers by Guillows, Goldberg, and Sterling were far better flyers and responded much better, in fact it was not until I had built and flown a 1/2A balsa plane that I was able to sucessfully fly a plastic Cox plane. With a teacher however, most kids can gain control of a PT-19 with a few minutes of flight training on a calm day.
All of the PT-19s with a seperate plastic fuel tanks have a a further aft CG because the early metal tank Baby Bee was heavier. Have not really noticed much difference in the way they fly due to that, because the biggest difference is with the lighter lines, and the wing tip weight adding more control feel at the handle.
I think I had the engine set at the "stunt" setting (no down thrust) when I flew it; as best I remember, the airplane as seen in the picture was in straight and level flight at the time the picture was taken yet it shows what I still consider a lot of "up" deflection.
I agree that most of the Cox plastic airplanes were at their best doing gentle climbs, dives, and flying straight and level. However, a few I remember as carrying terrific momentum and line tension through to touch-down with a realistic roll-out (on an asphalt surface) after the engine quit unlike the sheet balsa profiles I had. If you needed to, whipping was an option to set it down where you wanted. The Stuka, Miss America, Corsair, Super Sport, and Rivets come to mind. The PT-19 for some reason didn't seem to glide well though. The 1/2A balsa airplanes I had, a Sterling profile Spitfire, a Scientific Piper something or other and a couple Ringmaster bipes were much quicker responding under power but energy dissipated quickly when the engine quit making the pilot work quickly to maintain line tension and flare for a less than satisfying landing. Bipes having lots of drag is probably a big factor here. Granted, the Ringmaster bipe was the only airplane I was ever able to successfully loop back in those days.
In trying to analyze it myself, wondering if its all a function of wing loading, landing gear location and drag effects that influence the differences in landing qualities.