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teamgrumman(at)yahoo.com
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 Posted: Sat Nov 26, 2011 11:31 am Post subject: What a drag . . . |
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BH wrote, "When my cheetah is strait and level at 140 knots, the canopy rails are more than 1 degree ( 1.27 is my first measurement ) nose down. That means that rear section is 8.27 degrees nose down."
Now ya got me thinking again.
When 626 (the Project X plane) gets out of annual, I'm going to make some more detailed measurements on the wing incident. If zero lift occurs somewhere between 2 and 5 degrees down AOA, it MIGHT be possible to determine the lift on the fuselage.
Also, if max L/D occurs at somewhere between 2 and 5 degrees up AOA, now all we need is a device on the plane that finds relative AOA.
As a system, the vertical and horizontal lift and drag need to be considered. The lift and drag of the system seems dependent on loading, flap position, trim drag, cooling drag, aircraft weight, and Reynolds number (i.e., aircraft speed).
BH, can you make a mathematical curve fit to the rib you have? It might be possible to extrapolate data from existing NACA airfoil data. IF we know the top is a 64-415, then that shape we know.
BTW. The P-51 uses an airfoil similar to a 66-415. Same basic shape as a 64-415 but with the max thickness at 60% cord instead of 40% cord.
Gary
Sent from my iPad
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bob.hodo(at)yahoo.com
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| Posted: Sat Nov 26, 2011 5:26 pm Post subject: What a drag . . . |
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Gary >>> Now ya got me thinking again.
BH>>> I can't imagine you stop thinking very often...
Gary>>> BH, can you make a mathematical curve fit to the rib you have?
BH>>> I might have had that skill set 35 years ago, not sure, but I certainly don't have it now.
Gary, when I stare at that foil from the side, with my chair rail on the wall behind it like the oncoming airstream, I can see it not being too bad with the flat aft half parallel to the stream, and the front section more than 4 degrees up from that, and the big drooping front edge in its slickest profile. But that must happen down around 100 to 105 knots.
At 140 knots on the cheetah the flat aft half is more than 3 degrees nose down, and the front flat half is only about 1 degree nose up. To my eye it looks like the wing cannot possibly be lifting any longer, but apparently that big camber on top is still cranking pretty good. By this time however, we have a pretty blunt leading edge that kills a lot of bugs (and I think two hummingbirds on the way to Pennsylvania!)
I can trace you a copy of the rib on paper and send it to you to hang on your wall next to your TV if you like. ( Along with some pieces to stick on the front to change the shape as I would like!)
Bob Hodo
GADsden, AL
[quote][b]
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teamgrumman(at)yahoo.com
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| Posted: Sun Nov 27, 2011 9:02 am Post subject: What a drag . . . |
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Bob,
I would like a trace of the wing rib. I will reverse engineer as much as I can and see if I can find a profile that is close.
We may never know what its exact behavior is, but we can get close. At least we can get an idea where max L/D is.
Gary
Sent from my iPad
On Nov 26, 2011, at 5:23 PM, Bob Hodo <bob.hodo(at)yahoo.com (bob.hodo(at)yahoo.com)> wrote:
[quote]Gary >>> Now ya got me thinking again.
BH>>> I can't imagine you stop thinking very often...
Gary>>> BH, can you make a mathematical curve fit to the rib you have?
BH>>> I might have had that skill set 35 years ago, not sure, but I certainly don't have it now.
Gary, when I stare at that foil from the side, with my chair rail on the wall behind it like the oncoming airstream, I can see it not being too bad with the flat aft half parallel to the stream, and the front section more than 4 degrees up from that, and the big drooping front edge in its slickest profile. But that must happen down around 100 to 105 knots.
At 140 knots on the cheetah the flat aft half is more than 3 degrees nose down, and the front flat half is only about 1 degree nose up. To my eye it looks like the wing cannot possibly be lifting any longer, but apparently that big camber on top is still cranking pretty good. By this time however, we have a pretty blunt leading edge that kills a lot of bugs (and I think two hummingbirds on the way to Pennsylvania!)
I can trace you a copy of the rib on paper and send it to you to hang on your wall next to your TV if you like. ( Along with some pieces to stick on the front to change the shape as I would like!)
Bob Hodo
GADsden, AL
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