Speed Dream 35 Prototype

[Doug Lord]

Originally Posted by daiquiri

Just one consideration (sorry if superfluous): I believe that a lifting foil working so close to the water surface would experience a significant loss of lift due to aeration. Was this taken into account?
Cheers

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Slavi, Vlad is using a foil licensed by Hugh Welbourn which is a "DSS" foil. According to Welbourn and others the foil works well even if just using the bottom side in "planing" mode. See this thread for some info and a really cool video: Quant 28-foil assist keelboat / DSS
I have always been concerned that the biggest problem with DSS might be just as you suggest but so far, in the real world, they say that is not a problem. I'm not 100% convinced especially for use in the ocean but so far the results appear to be very good.

[Stumble]

As I understand it, by the time the foils aerate the boat doesn't really need the lift from them, of course as the boat heels over and the foils bury they start generating more lift. As I see it this acts as a self regulating system, that prevents the foils from ever forcing the boat beyond some heel angle.

My bigger concern for off shore work is what happens when sailing upwind and a wave trough passes under the boat. This could cause it to suddenly aerate, causing the boat to rock violently to leeward.

[daiquiri]

Originally Posted by Stumble

My bigger concern for off shore work is what happens when sailing upwind and a wave trough passes under the boat. This could cause it to suddenly aerate, causing the boat to rock violently to leeward.

Good point. Also because, if that happens, the foil would re-enter the water with a vertical velocity component (relative to the foil) due to hull roll speed, so the angle of attack could go beyond the stall...