Speed Dream 35 Prototype

Discussion in 'Sailboats' started by Doug Lord, Jan 10, 2011.

  1. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Speed Dream

    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: http://www.boatdesign.net/forums/sailboats/quant-28-foil-assist-keelboat-dss-38421.html
    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.
  2. Stumble
    Joined: Oct 2008
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    Location: New Orleans

    Stumble Senior Member

    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.

  3. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    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...
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