Ben
A well shaped film/cloth soft sail can have a higher L/D than a wing. However the soft sail usually has added drag from the supporting systems of mast and stays. A clean wing design avoids this extra drag. Also the soft sail has a narrower operating range for angle of attack meaning it has to be trimmed to keep driving as the apparent angle to wind changes. A wing with rounded leading edge has an optimum angle of attack for best L/D but also works well either side of the optimum.
Kitewings are efficient soft sails:
They are relatively high aspect ratio, clean aerodynamically, light and can be easily canted to give a lifting component thereby reducing the vehicle or hull drag supporting the pilot. The canting and high efficiency are the same features that Paul Larson's rigid wing achieves. I believe the kitewing could be adapted to a small proa but I do not see an easy way to reduce wing area without carrying different wings. There may be a more elegant way of achieving the same result with a soft sail that can be reefed.
Rick
On 26/01/2013, at 12:22 PM, bjarthur123 wrote:
's been awhile since i looked into this, but IIRC a thick foil confers no benefit at the reynolds numbers typical of sailing. so you're better off with the simplicity of a single-surface sail. can anyone confirm? rick??
Rick Willoughby
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