Trimaran speed under power

Discussion in 'Multihulls' started by Jetboy, Jul 17, 2012.

  1. Jetboy
    Joined: Feb 2012
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    Location: USA

    Jetboy Senior Member

    Another thread in the motorsailer section got me thinking:

    The dream family sailboat for many would be able to both sail really well and motor at a good speed. I can understand the argument that you wouldn't want to give up sailing performance for motor performance, but I think a lot of sailers would make some performance concessions. The fact that the Mac26 sells so well is obviously a testament to that fact.

    A folding trimaran could possibly fit the bill very nicely. So... would it be possible to reinforce something like an F22 or a comparable size trimaran to handle say a 40 or 50hp outboard and run at 15-25 mph under power and still keep the ability to sail well?

    I think the hull design would require a re-working in order to probably look a bit more like a weta in terms of more buoyancy aft to help with the structural weight and the motor weight, as well as help get the boat up on a plane easier (if planing is necessary). I'm not sure what type of HP would really be necessary for 15 or 20. Possibly a 20hp would provide that? I'm not really sure how a typical trailerable tri would handle increasing hp.

    I know weight is a bit handicap for all sailboats and particular multihulls, but it seems as though trimarans might be well suited to be a great multi-use boat that can motor fast and sail well. I wouldn't expect it to tow a skier, just be able to motor quick enough to do what the Mac26 targets and still sail faster than a comparable length 4ksb.

    Thoughts?
     
  2. Greger
    Joined: Jan 2013
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    Location: Grayling Mi.

    Greger New Member

    I have been looking for same boat, no luck. Speed under motor power is different from sail power, wonder if amas can take the abuse?
     
  3. Turnpoint
    Joined: Jun 2011
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    Location: Port Townsend

    Turnpoint Junior Member

    F-24

    I like that idea too.

    but for some food for thought.... I once had a corsair F-24 that had a 15hp Honda 4-stroke mounted on it when I bought it. It wound do about 9.3 knots at full throttle. We swapped that for a 8hp 4-stroke and it would do 8.5 knots at full throttle. With the bigger motor it would squat and make a bigger wake. The F-24 had a sharp break in the rocker profile 2/3 from the bow that would return back to waterline at the transom. My understanding is that while sailing at speed this helped keep the bows up and counteract the sailing pressure. You could see this while sailing... Bellow 8.5 knots the wake noise would increase and it would take more and more sailing Pressure to increase the speed... Until the transom would break lose, the wake would quiet down and all of a sudden boat speed would start to climb quickly above 10 knots. Maybe one of those outboard mounted hydrofoils would have lifted the stern enough to get it to break lose.? Anyway, from my experience the f-boat main hull isn't set up for fast sailing. Something with a more submerged transom at rest would be better... But then low wind speed sailing performance would be lost. It would all be a compromise.
     
  4. Greger
    Joined: Jan 2013
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    Location: Grayling Mi.

    Greger New Member

    Ummm, could it be that simple? Just add hydrofoils to a bigger outboard and make most any trimaran a fast trawler?:idea:
     

  5. Turnpoint
    Joined: Jun 2011
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    Location: Port Townsend

    Turnpoint Junior Member

    I really don't think an outboard mounted hydrofoil would have helped the f-24 too much... But I wish I would have tried it when I had that engine on the boat.
     
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