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Post by chuck59 on Feb 1, 2012 7:49:58 GMT -5
P.S. so I gather from all this that as soon as I really feel confident and am consistent in my S-II, a Pitts would make for an easy transition? That's true. A Pitts is actually a bit easier because you have all that horsepower to get you out of trouble if things start to get out of hand.. ;D
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Post by oahupilot on Feb 1, 2012 18:03:10 GMT -5
I use TOW (Theory of wing sections) for airfoil lift and drag numbers in here, those wing sections in that book are NASA wind tunnel tested, real and proof. NASA did not do the wind tunnel tests, the name of the organization is part of the airfoil number. NACA. Also in an early post you said you preferred "aerodynamic science to empirical observation", I hate to break it to you but all aerodynamic data is based on empirical data, as no working solution currently exist to model all aspects of fluid flow. Most of the equations we have for fluid flow are designed to fit the data that was collected during wind tunnel tests. When naca tested their airfoils it was based under certain ideal conditions and in a controlled environment, this does not guarantee the same result in the real world. You also have not even mentioned angle of incidence which affects lift produce for a given speed. A NACA 0009 produces 0 Coefficient of Lift (CL) with no angle of incidence but at 10 degrees angle of incidence you get a CL of 1.082. I don't think most designer are untruthful about their numbers, I think its probably an idealized best case scenario.
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Post by oahupilot on Feb 1, 2012 18:31:33 GMT -5
Hi Ed, as I only have a few hours of Sonerai-II under my belt, and no other powered taildragger (but many hundreds of flights in gliders some decades ago) I love gliders, so much fun, to bad they cost a fortune to operate and own. The last glider I flew was acrobatic and such a joy to fly. I was impressed by how fast you can pick up speed in a glider and the sound of the wind rushing by the thingypit. I would love to own an acrobatic motor glider one day. PS Seriously who wrote an easter egg into the forum that changes C*ckpit to thingypit, lol.
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Post by Schmleff on Feb 1, 2012 18:35:35 GMT -5
Yes, i remind that previous example just show very simply way to have some kind of clue of wing lift/ stall speeds. There is lot of more things to considered when actually design or calculate a wing. These examples is actually "best case scenario" type, and usually lift of wing is smaller....if there is twist or "not so perfect" surface of low aspect ratio or.... Looks like with those numbers (stall/ lift) that Sonerai frame don´t generate lift....and most of airplanes fuselage don´t generate noticeable amount of lift, unless it is design like it....like flying wing. Hans is absolutely right, you should use data with correct reynolds number for airfoil when calculate wing. You find what Re is and calculator for it here, NASA site: www.grc.nasa.gov/WWW/BGH/reynolds.htmlTalk to the KR guys that decided to high speed taxi their planes without wings about how much lift the fuse makes... ;D
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Post by Schmleff on Feb 1, 2012 18:45:01 GMT -5
It seems like we are straining at a gnat here. My ASI goes to 0 before my plane stalls. Years ago I flew mine under LSA rules (with the little motor). The manufactures word is good enough for the FAA, why do we want to fight that? If it was that important to the FAA you would expect there would be a special LSA stall speed task force... Neither I nor the FAA really has a way to determine what my planes stalls at under ideal conditions at sea level.
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Post by n3480h on Feb 1, 2012 20:26:53 GMT -5
Gotta agree with Jeff. The FAA has much bigger fish to fry than to expend manpower and dollars toward enforcing such insignificance. Just keeping FAA functions financially viable is a challenge these days. And really, who is going to stall any aircraft at sea level? I guess one could fly into Death Valley on a standard day. If I wanted LSA, I'd just build it light, build it safe, and fly. Enjoy this great little aircraft and leave the worrying behind. Life really IS too short. Tom
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