Aerodynamics. It's not a bad word.

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Steve D
Posts: 50
Joined: Sun Mar 05, 2017 9:50 pm
Location: Grand Republic of Texas

Aerodynamics. It's not a bad word.

Post by Steve D » Sat Dec 02, 2017 10:50 am

I accidentally posted this in photos.

After some discussions with my friend, the former aerodynamics professor for a boating school in Maryland, I was shocked when he said the Pietenpol is not very aerodynamically clean! He does like the design, but it was not built with aerodynamics in mind. He is a pilot with a Bonanza and says it could easily have gone 10-15 Knots faster with simple cleanups. Here are my takeaways for improving the aerodynamics:
He liked the wing shape for the mission. These are the aerodynamic improvements he felt would make the most difference. Cover the front cockpit when not used. Wheel pants. Fair in the landing gear or cover like a champ or streamline the landing gear legs. Then streamline the struts and cabanes. The only shape worse than a round bar is a flat plate. The teardrop shape is best at our airspeeds. Fair in the strut and cabane attach points at the wing and fuselage. The tail intersection can be faired. Other improvements would be flat streamlined flying wires, and fairing in fuel caps and so on. The windscreen size, shape and slope could be studied. Then fairing in bolt heads and so on.
He did feel that you would quickly hit a point where modifications wouldn’t bring much improved performance. (That whole parasite drag thing on the wing and fuselage.)
I was surprised at his statements regarding raising the wing 2 inches, cutouts or flops. He felt that raising the wing 2 inches would have little effect on aerodynamics except for the added drag of 8 inches of cabane. I was very surprised that he felt that a well done cutout would be better than a flop and neither was much worse than the straight wing. The center section location of the cutout or flop is in a place with so much interference (gas caps, cabanes, windshields, wires, and sometimes a radiator) that it is not as critical as it would be out on a wing. The flop gaps, locks and hinges could create about as much drag as a cutout unless very well faired in.
Videos of shapes in wind tunnel
https://www.youtube.com/watch?v=TqTSyFz6DJc
Streamline effects on light plane
https://www.youtube.com/watch?v=h7tXbXbPhd4

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