![]() ![]() The acceleration of the air downward in the wing wash is a large part of the lift off a wing. You've redirected the air coming up to the foil and squirted it downwards. There's now a very healty curve up to the airfoil and a strong downsweep off the trailing edge. But look at the way the streamlines have changed. ![]() Note the volume between the pressure curve grows. Somewhere about a 1/4 psi at 6 degrees if you average it out. ![]() Note that the streamlines have a little bit of deflection downwards at the trailing edge and there's a pressure difference in the chart on the right. Use the slider on the right side of the airfoil to zoom back for a wider view. Start with the symetrical one and add 6 degrees of angle (of attack) using the slider. Looking forward to hearing from Ollie and Ben and the others here.ĭrop on by this site for a very interesting app that lets you play with an airfoil in real time. I'm going to take a stab at this now and hope that I'm not TOO wrong. You're really bending my mind and I'm learning that I have some bad misconceptions. I've written this part about 4 times now. ".how a flat bottom airfoil works (high pressure under the wing and low pressure over the wing)." But in the meantime here's the polars to go with the above.īut you also put in an interesting point. There's another item but since it has another pic to go with it I'll break this into two. So you CAN fly and even thermal soar with a symetrical airfoil but it's going to have some limitations. See that recurve back? That means that in very fast flight it's actually making MORE drag than when it's cruising quickly but not speeding. The relatively high camber 7037 gets up to about Cl 0.9 before the drag gets very high. The very low camber 7003 FAI glider type has a slightly better range up to 0.8 and a low end that is really fast in a vertical dive when the Cl is 0 but would be draggy if you actually flew upside down (that part is missing here but it's in my Soartech 8 book). And, of course, being symetrical it does the same thing when upside down. In the pic below you can see the 8020 fully symetrical has a range of lift up to about Cl= 0.4 to 0.5 before it gets kind of draggy. If you look at polars for symetric and cambered types you'll notice that the airfoil has a range of lift and that as the camber curve rises the lift range is shifted towards the positive values and the max lift coefficient before the high drag knee that we know as a stall moves up as well. It just happens to have a very, very low camber value. ![]()
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