Why is the gossamer albatross prop angled downwards?

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HumanPoweredDesigner

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First I thought it was to get a lift component from the thrust with a small loss in forward thrust, since sine climes faster from zero than cosign drops from zero. But this might not help since lift varies with lift squared.
So, I now wonder if it is so the prop is going straight into the downwash of the wing, so the blades do not get different lift at each part of their path, and produce huge vibrations. But even that would only work at one air speed. (is cross wind a vibrational problem for propellers?)
Or maybe he just happens to have a possitive angle of attack there?

So why?

http://upload.wikimedia.org/wikipedia/en/f/f3/Gossamer_Albatross_II.jpg
 

shadow

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Sep 23, 2008
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I'll make a guess. Perhaps it's because the propeller is acting in the wing's downwash and giving the propeller a positive AOA lined it up better with the flowstream -> better efficiency.

Shrug,
Serge.
 

HumanPoweredDesigner

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I bet it would also be a good way for me to get less dirt and rocks in my propeller. More it points up, less the rocks come up. Maybe also less wind blowing past the pilot in front.
 

bmcj

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I bet it would also be a good way for me to get less dirt and rocks in my propeller. More it points up, less the rocks come up. Maybe also less wind blowing past the pilot in front.
Those are both terrible reasons for changing the angle of your thrust line. Stability should be your driving factor.
 
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