Nit picking: only stunt people say "moment" when they're talking about a length. In physics and mechanical engineering, it's "moment arm"; a "moment" is either a short period of time or a torque, but is not itself the arm along which a pair of forces is turned into a moment.
Observation: This is kind of what I was saying in my deleted post about copying a design: know what to copy and how, and you can at least have a good starting point for a new model. The high point of the wing isn't really the right place: the wing's mean aerodynamic chord is. But chordwise, the high point of the wing is pretty darned close to the MAC so it's not at all a bad approximation to use the wing highpoint instead.
I honestly think that if you knew the important aspects to pick off of a design, and you knew how changes (such as changing the aspect ratio, or moving the tail back) would affect the airplane's performance, you could go a long way to building credible, if not world-beating, airplanes.
Tim, I quite agree and simply missed "arm" - I've always used the "correct" term in my notes. But I think you miss a couple of points.
I'm not much interested in copying the "numbers" from, say for example, an Impact, to build a .25-powered profile. The approach has worked really well over the years -
for me. Your own mileage may vary ...
Second, for all but the very highest levels of competition - and I'll stick my neck out here - my money is with the guy that practices and practices and practices over the guy who simply shows up with a "world-beating airplane".
Back in my high school days again - when building was really my least favorite part of the hobby - I won a combat match on an
extremely windy day with a Ringmaster powered by a Fox .35 Stunt engine and with only the inboard wing. Good friend Jack, in either admiration and/or shock, exclaimed, "Leonhardi, I swear you could fly a brick!"
It was a slight exaggeration, of course, but I seriously doubt there are many here who are out flying as much as some of us were back then.
I have designed over the years, going back to the '60s, several well-liked designs that flew well enough to be used as club builds. That's probably more satisfying to me than designing a Nats winner would be.
I have strong personal preferences, and suggest that anyone interested in starting to design their own airplanes ought to develop their own. And to encourage them, let’s keep it relatively simple!
I like relatively low aspect ratios, for example - they tend to be stronger, less prone to warp, and are more stable in strong winds.
I like airplanes slightly more nose-heavy than many others; they tend to groove better and are easier to fly by “feel” when not looking at them.
Those are starters … anyone else?
PS: Tim, when reading Netzeband’s summary, pay special attention to this -
“It slowly became obvious to me, that WINNING a stunt event was firmly in the hands of the pilot, the judges, the flying site, the weather du jour, not to mention the pilot’s lucky socks. The capability of the AIRPLANE to perform a perceived, acceptable flight path appears way down the list in order of importance.”Dennis
Topic: Design Parameters III (Read 6633 times)
