catamaran hull shape that provides reserve buoyancy

Discussion in 'Multihulls' started by rapscallion, Jan 4, 2013.

  1. rapscallion
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    rapscallion Senior Member

    Does anyone remember seeing a catamaran hull shape designed to provide additional stability when excessively healed? I was picturing a hull with a flare that would act like a lee pod on a proa hull in order to slow the motion of a capsize. I wouldn't want the goal of the reserve buoyancy to be capsize prevention, but rather an additional zero point on the stability curve. Has anyone tried this in a design before?
     
  2. Stumble
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    Stumble Senior Member

    Rap,

    You would have to run the numbers but my gut feeling is that the amount of additional stability would be dwarfed by the stability provided by the width of the hulls. I just can't see you being able to provide enough additional flotation to really mean that much in the grand scheme of things.

    On a trimaran it's a different issue, which is why Corsair just redesigned its floats to provide more buoyancy.
     
  3. Richard Woods
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    Richard Woods Woods Designs

    yes a number of people have done that. Maybe one of the first was David Barker with his Sundancer in the late 1970's (my apologies if I got names wrong, it was a long time ago)

    I, and many others, have designs with a knuckle and flare which help increase static stability at high heel angles. I write a bit about it in the Articles pages of my website

    There are possible problems if you take the overhang too far. Coming alongside and using fenders, or maybe "flare slam" in a cross-sea for example

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  4. Gary Baigent
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    Gary Baigent Senior Member

    Richard, not Sundancer, which had narrow, angled out, somewhat like CSK catamaran hulls but symmetrical in cross section; you're thinking of Sundreamer with her accommodation pods ... but these did not run to the bows to provide extra buoyancy up high. By the time these pods would be adding safety, it would be way too late, the crew catapulted through the rigging.
     

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  5. warwick
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    warwick Senior Member

    Was there not some thing by Malcolm Tennant, for the mini transit race?
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    Plenty

    And that's why. If one wishes to enhance the range of stability and/or the righting moment, that is the easy quick option.

    BTW...you wont prevent capsize...it'll happen under the right conditions.
     
  7. Gary Baigent
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    Gary Baigent Senior Member

    Warwick, Malcolm Tennant drew a 6.5m catamaran idea for Mini Transat (Daniel Charles from France subsequently informed that no multis were allowed in the 6.5m race but liked the idea anyway) with a small wing mast in each hull and had a small blister somewhat Dick Newick proa style each outer hull side ... so that if it capsized sideways the blister and buoyant wing mast would halt the cat from going right over, would instead lie on its side.
     
  8. warwick
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    warwick Senior Member

    Thanks Gary, for filling me in on the Malcom Tennant Cat. I vaguely remember reading about it, possibly in the early eighties.
     
  9. rapscallion
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    rapscallion Senior Member

    Malcolm's cat sounds like an interesting design. No info about it on his website... bummer.

    This paper came to mind...

    http://www.sailboat-technology.com/...ion_For_High_Performance_Superyacht_Polli.pdf


    But it sounds like the hull shape wouldn't provide a benefit worth the additional complexity. I tipped my G32 over a half dozen times least season! It pops right back up thanks to Jan Gougeon's genius :) I tend to push for speed when I should be cautious..

    I am very impressed with the 1999 Alingi catamaran design brief, As well as the decision 35 design. I was trying to dream up a decision 35 design approach to an all out racer that included some reserve buoyancy that would buy a solo sailor an extra couple of seconds to blow the main before going over. But maybe training wheels on a racing cat aren't such a good idea.

    My thoughts were along the lines of a 35' to 40' version of the WSL70 design. The goal would be a catamaran, as fast as a Reynolds 33 (PHRF in the -70 to -80 range) that could be sailed from the center pod by one person. I really like the water ballast on my current cat, and the 1999 Alingi design uses water ballast as well. I also love Jan's new design strings.. but my center pod would be lower, smaller and more modest. The beams could slide past one another like the L7 trimaran, and the boat could be trailerable. And, because I tend to tip cats over I would go with a self righting system like The G32.
     
  10. teamvmg
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    teamvmg Senior Member

    [​IMG]


    AAARGH!
     
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  11. rapscallion
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    rapscallion Senior Member

    I wouldn't want to get into a tacking duel in that thing!
     

  12. El_Guero

    El_Guero Previous Member

    It makes for a great model.
     
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