It's time for me to eat humble pie. High aspect ratio in a pylon racer is not as important as I thought.

I designed a trial 1/2 A pylon racer on paper. I selected the S6063 wind tunnel test model airfoil which had the lowest coefficient of drag in the Selig series of tests at UIUC. It has a low drag bucket from Cl=-0.05 to Cl=0.4. It doesn't stall until Cl=0.8. The Cd minimum at R==300,000 is 0.006.

I assumed a 36 inch span, 4inch average chord, one pound flying weight and a speed of 100MPH. The airfoil reynolds number under these conditions is 312,000 which allows the use of the windtunnel test data. In straight, level flight, the Cl computes to 0.04. In a ten G turn, the coefficient of lift would be 0.4 which is just within the low drag bucket. The Cd=0.0075 in a 10G turn and the bank angle is 84 degrees. The radius of a 10 G turn is 67 feet. Does this sound like it is tight enough to win races?

Since the S6063 is ony 7% thick that would be 0.28 inches on a 4 inch chord. This raises the question of spar strength, stiffness and weight. Unicarbon pultrusions are available with a compression strength of 275,000 PSI. A standard size is 0.034 x 0.121. Two spar caps of this stock weigh 7 grams. With 0.2 inch high, end grain balsa as a shear web and kevlar thread wrap such a spar would weigh about 1/2 ounce and be able to carry a 50 G load in this application.

The total drag is hard to estimate because of the unknown parasitic drag. However, assuming a parasitic drag coefficient of 0.01 and adding the induced drag coefficient of 0.0057 in a 10 G turn plus the profile drag of 0.0075 for a total drag coefficient around 0.0232. From this I calculated an estimated drag of 9.5 ounces. This seems in the ball park for the thrust of a 1/2 A engine.

The conclusion is that the speed advantage of the aspect ratio 9 wing over an aspect ratio 3 wing would be roughly 10% in the turns. Also, with either wing the speed in the turns would be about ten percent slower than in the straights.