Crossbar hydrofoil

Discussion in 'Multihulls' started by SPC, Nov 26, 2020.

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  1. SPC
    Joined: Jul 2020
    Posts: 11
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    Location: Raleigh NC

    SPC Junior Member

    I have seen that there are aluminum extrusions available which directly work as a hydrofoil for some uses. I am wondering what would happen if I installed one, fixed, between the hulls and under the waterline on a cruising catamaran, about 1/4 of the way back from the front so it would be at the peak of the max bow wave. Rather than trying to make a foiling catamaran that lifts the hulls completely out of the water, it would never be lower than the hulls it would be attached between. In my mind this would lift up the bow just a little bit when in motion, which if I understand would be beneficial even for a normal displacement hull.

    Has this been tried or discussed?
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    I would think that would be more likely to be detrimental, giving the boat added lift forward of the COG. Can you direct me to the extrusions you speak of ?
     
    Last edited: Nov 26, 2020
  3. Heimfried
    Joined: Apr 2015
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    Location: Berlin, Germany

    Heimfried Senior Member

    Search for "HYSUCAT", "K G Hoppe" or "Gunther Migeotte" and you will find a lot of information about a very similar solution.
    Also www.proboat.com , click "back issues", find Issue #157 of "Professional Boatbuilder" (Oct./Nov. 2015) p. 68 ff
     
  4. SPC
    Joined: Jul 2020
    Posts: 11
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    Location: Raleigh NC

    SPC Junior Member


  5. Heimfried
    Joined: Apr 2015
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    Location: Berlin, Germany

    Heimfried Senior Member

    If the installation of fixed foils between the demihulls will be rewarding, depends among other things on the speed you will drive your boat mostly. The foils are causing additional drag at every speed. Only above a certain speed, the foils will lift the boat at such a level, that the overall drag is lower than the drag without foils.

    Perhaps you should calculate lift and drag to expect before you start the build. Read e.g. the book Hydrofoils - Design Build Fly by Ray Vellinga.
     
    kapnD likes this.
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