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Old 29th May 2013, 09:22 AM   #6
Jean-Marc
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Join Date: Aug 2006
Posts: 1,343
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Farlo is spot on.

The power of a foil (windmill, fin, sail) is directly proportional to air density. From 35C to 5C, that power increases by roughly 10% (cold air is denser, heavier).

That 10% power surge might appear small but if wind speed and foil's efficiency are kept constant, the power of an 8.6 m2 sail (assuming a luff lenght of 500 cm) used at 35C is roughly the same as that of a 7.7 m2 sail (assuming a luff lenght of 474 cm) used at 5C. So, it's no surprise that you feel overloaded by using your 8.6 m2 sail at 5C whereas you feel nicely overpowered at 35C.

You can play around with numbers to calculate the power of a foil (i.e., a windmill) here : http://www.engineeringtoolbox.com/wi...er-d_1214.html

Cheers !

JM

Last edited by Jean-Marc; 29th May 2013 at 09:29 AM.
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