Multihull upwind/reaching performance

Discussion in 'Multihulls' started by misteringer, Oct 21, 2014.

  1. misteringer
    Joined: Aug 2014
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    misteringer Junior Member

    I am just curious about how well multihulls (specifically cruising cats) perform upwind and reaching in big waves (not normal big waves, but huge ocean swells generated by storms (up around 20 feet or 6m). The reason I am asking is because whenever I see a video of a cat in big waves, they are running downwind with a drogue out.
    Is this the only option or were they just lucky and just happened to be heading in the same direction as the wind and the waves? I'm just curious because I have heard so many people say that multihulls are superior to monohulls, but if they can't go upwind in big waves then I would have to disagree. All answers are appreciated and thanks in advance for helping me understand.
    Also, if anyone knows, what size wave would be required to flip a large catamaran like a lagoon 380 or something? (lagoon 380 has a 6m beam)
  2. Gary Baigent
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    Gary Baigent Senior Member

    Depends how heavy they are, if you're talking about cruising cats, whether they have decent dagger foils, whether their windage is excessive and so on. A number of the heavy production sailing "caravans" have a bad reputation; have to start their motors to go to windward.
    If you're talking about more performance oriented designs and not water bus types, then they beat and reach perfectly fine because their windage is low, platforms are wide, therefore powerful, and their foils are superior than low aspect ratio keel types as seen on some cruisers.
    Check out the many videos of race multihull performance in such conditions.
  3. Richard Woods
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    Richard Woods Woods Designs

    The OSTAR was always won by multihulls from 1972 (except in 1976 when Taberly won, but a Val 31 came in shortly after). That is a windward ocean race, open to both multihulls and monohulls. The multihulls finish first in the Fastnet race, and no doubt will do so in the Route de Rhum next month

    Not many boats actually do well going to windward in 20ft waves, however many hulls they have. And usually the crews fare even worse.

    A boat is stable in wave that are less than the boats beam. So your Lagoon should be safe in 20ft beam seas. But much depends on whether you mean a breaking 20ft wave or a 20ft ocean swell (which a sailing boat won't really notice, but a big ship will)

    Check out the first 50secs of this video. How high is the wave? 8ft maybe??

    and this one, start watching at 4mins in. Also not a 20ft high wave

    and this is a classic

    Most people try to avoid sailing to windward in major storms, so there is actually very little hard data to prove the case one way or the other. Pete Goss did it in the Vende when rescuing Rafael Dinelli, but few others have

    Richard Woods of Woods Designs
  4. keysdisease
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    keysdisease Senior Member

    The rig and sailplan of any vessel are what go to weather, the boat is just along for the ride.

    However much leeway a vessel makes is a function of whatever leeway prevention device is employed, daggerboard, leeboard, keel, foil, etc.

    Stability in order to "carry" the sail plan is different in a monohull vs multihull, beam vs ballast

    Windage plays a part in leeway and speed, the less windage, the less leeway and the more speed.

    I think. ;)

  5. Richard Woods
    Joined: Jun 2006
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    Richard Woods Woods Designs

    This from SA

    "92 yachts are still racing in the Rolex Middle Sea Race. The expected frontal system arrived around Midnight last night at the northwest corner of the course. Reports of storm force winds and big seas have been received by the Race Committee and 25 yachts had officially retired from the race by 15:00 CET on Wednesday 22 October. The Race Committee has received no reports of any injuries to crew from the fleet."

    Check out the conditions and the monohulls that retired. I bet it wasn't 20ft waves, and probably not 60 knots wind. Looks like it wasn't to windward either (but I haven't looked at the results myself)

    Richard Woods
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