Join Date: Mar 2007
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We have actually been employing this fan method for quite some time with good results, all these laws of physics notwithstanding. As an earlier post pointed out, one key is to run enough of them in series. Ours are mounted outboard on cantilevered outriggers, which can be folded in for docking manoeuvres. They can also pivot fore and aft as much as 30 degrees for apparent wind adjustments, as we sometime like to vary our point of sail for variety's sake (beam reaching everywhere can get somewhat tedious).
Another important design aspect, often overlooked by previous unsuccessful pioneers in this burgeoning field, is to ensure that the orientation of the fan blades and their direction of rotation is SUPPLEMENTAL to, rather than opposing, the coriolis effect. Obviously this requires that the apparatus be re-oriented when moving between hemispheres, but this impediment only affects a small number of sailors anyway.
Others will be curious as to the performance advantage: It's no exageration to say that they are ample. In comparing observed speeds to the polars for our boat, we sometimes register velocities as much as 1/10 of a knot greater than predicted. Someone else pointed out the energy consumption issues, but we long ago resolved that obstacle by powering each fan with its very own Solar Stick. All in all we are pleased with these modifications and find they are well worth the tremendous effort, substantial cost, and modest inconvenience. To the skeptics, we say: "Just give fans a try!"