Hi Otto,
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Originally Posted by Otto
0Here's a thought, if u
sing L-shaped plastic: Why not cut it with pinking shears, such that its edge is a zigzag? This might turbulate the cross wind as well or better than a uniform wall height, with less drag.
Thoughts?
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An interesting thought. Pinking shears I've seen are have pretty small zigzags. Also, unless made of something compliant like rubber they could be hazardous if you brush against it or worse yet hit a pedestrian. The victim's lawyers would have a field day! I've said before that a simple fence behaves as a degenerate form of a stall strip (on aircraft they are usually triangular in section). Maybe a line of vortex generators set in a straight line rather than the usual angle would be more effective. Again, they should be made of something like rubber to avoid injuries. However, a fence or similar would almost always produce turbulance (and drag) on the lee side as a perfect head on apparent wind is a very transient condition at best. I would think a small amount of lateral lifting force is acceptable for very low apparent cross wind angles. A proper triangular stall strip would be nearly "aerodynamically transparent" until the apparent cross wind angle exceeds the half included angle of the stall strip.
I hope I'm not using too scientific/engineering terminology for most readers, that's my training and nature.
Quote:
Also, in the movie World's Fastest Indian (now available on Netflix, well worth watching) Burt Munro's motorcycle fairing has a longitudinal ridge similar to what we're discussing here:
https://encrypted-tbn0.gstatic.com/i...FI6pL7Irtd0kEX
I'd assumed it was a simple external joint for the two fairing halves, but now I wonder if (assuming the movie prop is a true replica) Munro had sorted out this crosswind device 50 years ago. Anybody know?
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I looked at the picture you linked to and studied it. The longitudinal ridge is obviously more than a body section join line as it is rectangular in form (as far I can see from the AMA's museum (I think) replica) and continues on the top of the tail.
The fiberglass can clearly be seen to roll over the edge of the rectangular section The rectangular section could simply be a practical implementation to provide a structural stiffener when the halves are separated. Otherwise they would be a bit floppy and difficult to handle. A preliminary Google search for it's aerodynamics has yielded nothing so far.
Maybe Bert (original spelling per Wikipedia) Munro stumbled onto a stall strip a half centry ago. He seemed to be the "tinkerer type" of guy and not much of a scientific documentary type person. He apparently died with his reasons.
As George Santayana said: "Those who cannot remember the past are condemned to repeat it". In my defense, I never knew it, so I didn't forget!
-- Teri