Manoverable Trimaran Design

Discussion in 'Multihulls' started by rapscallion, Mar 10, 2007.

  1. rapscallion
    Joined: Oct 2006
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    Location: Wisconsin

    rapscallion Senior Member

    what design features would make a trimaran more maneuverable? I was thinking specifically about talking and jibing..
  2. Doug Halsey
    Joined: Feb 2007
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    Location: California, USA

    Doug Halsey Senior Member

    I worried about this while designing my 15' singlehanded hydrofoil trimaran (Broomstick). Since this boat is wider than it is long, I knew it would be hard to turn, especially to tack.

    I didn't do anything special in the hull design, other than provide enough rocker so the bow & stern wouldn't drag, but I did choose a sloop rig, rather than a cat rig, thinking that I could I could influence the turning with the relative tensions on the main & jibsheets. I soon found that handling mainsheet, main traveller, jibsheet, & wrestling with an 8' long tiller extension was too much for 1 pair of hands to do. Backwinding the jib made it easy to get out of irons, but having the jib made it much more likely to get into irons in the first place.

    Finally, I figured out that I could use the drag of the amas & foils, way out near the ends of the main crossbeam, to help the turning. Coming into a tack, I deliberately heel to windward & the boat spins very rapidly into the wind. I keep it heeled the same direction until it has turned sufficiently far off the wind on the new tack. If the boat should get into irons & start moving backwards, I heel it in the opposite direction as well as reversing the tiller.
    Jibing has never been a problem, maybe because heeling to leeward naturally tends to make the boat turn away from the wind.

    Using the ama & foil drag to help maneuver has been so effective that I'm intending the cat rig to be my usual mode of sailing.

    Photos of my boat & a short description can be found in the International Hydrofoil Society's Photo Gallery :
  3. Paul Scott
    Joined: Sep 2004
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    Location: Spokane, Wa

    Paul Scott Senior Member

    Doug- it looks like you moved to a wishbone boom (?). Are you going to stay with it? Why? This not criticism. I like wishbone booms, but sometimes I don't know why, exactly.

  4. Doug Lord

    Doug Lord Guest


    Doug, your boat looks great! Would you be willing to share your foil areas and your philosophy in choosing those foils? I note that the rudder kicked up with the foil apparently still attached - seems like there could be a lot of force. How does it work? Great job-great weight!

  5. Doug Halsey
    Joined: Feb 2007
    Posts: 440
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    Location: California, USA

    Doug Halsey Senior Member

    Sorry for the delay in answering Paul & Doug's questions; I was out of town for 10 days without a computer & just saw them today for the first time.

    About the wishbone boom : Actually, the wishbone rig was the original (on my smaller main) & the conventional boom is newer (on my larger main). I'm planning on converting the smaller main to a conventional boom soon, but I'll have to make a short extension to the base of the mast to get enough clearance for me to get under it when tacking & jibing. I would like to post a longer reply, but I would prefer to start a new thread comparing wishbone & conventional booms (in the Sailboat forum).

    About the foil configuration & dimensions : Thanks, Doug, for your favorable comments. I'd be glad to give you some numbers & my reasons for choosing this type of foil, but again I think a new thread on foil configurations (in the Multihulls forum) would be more appropriate.

    Unless someone has a better idea about where to post these replies, I'll be planning to write longer replies later this week.
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