Once again let me point out that this data was for a Re = 20,000 and our typical stab is at ~ Re = 200,000. But none the less, I found it interesting anyway, in that the reversed airfoil had a linear lift response through zero alpha. The conventional direction for the airfoil at this Re was interesting in its “deadness” around zero alpha +/- 1.5 degrees, but once again, not at our Reynolds number. Hoerner (Fluid Dynamic Lift) has data for a reversed 0012 at a Re=2,500,000, once again not at our Re. It shows the same very linear effect through zero as does the Re = 20,000. I make a leap to assume that for our speeds the effect is the same. So the force from the stab around zero alpha is responsive and predictable.
The “dead effect” around zero is very pronounced for the Re 20,000 case. Data for a 0012 at high Re generally doesn’t show it. At our Re, it’s probably there, dependent on the leading edge shape.
At any rate, my gut feel, like David’s, was that the sharp leading edge would be disaster with any incidence at all. But, as we see, it isn’t too shabby at all, very one-to-one for angles of +/- 8-9 degrees.
Which brings up another question. What incidence does the stab see during a square corner? As Howard’s diagram above depicts, as the pitch rate starts, the driving angle-of-attack on stab is decreased, due to the tail length and the rotation rate. So, what is the range of alpha of the stab? It may be that it never gets above +/- 5 degrees or maybe 10 degrees. Is there any way to capture that in flight?
A guy walks into the wind tunnel area and asks, “which one of those guys is Richard Whitcomb?” The response was, “the one holding the metal file”. Whitcomb apparently was always willing to do a little filing to the model to seek a better result.
Topic: Walker's Stab Leading Edge (Read 13112 times)
