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Thread: The Basics

  1. #1
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    Default The Basics

    I am no expert with multihulls - in fact the opposite, however the basic safety of a multihull design was the very first factor I considered in my move from big power boats to a sailing cat.

    On rule of thumb that stuck in mind was that if X is the force it takes to roll a mono hull, it will take 5X to roll a cat.

    I then bought every book I could on cats and searched, in particular, for accounts of cats in storms.

    All that research led me to the conclusion that cats are safe boats.

    It also led me to ask a whole series of more detailed questions about what design features increase/decrease the safety of cats.

    These questions are what this forum is about.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  2. #2
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    Default

    First and foremost - its the sailor that makes the safety. The boat - mono multi or bathtub, just gives the sailor some parameters to work in.

  3. #3
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    Default

    Quote Originally Posted by ForumAdmin View Post
    On rule of thumb that stuck in mind was that if X is the force it takes to roll a mono hull, it will take 5X to roll a cat.
    I dont believe that this is a viable rule of thumb. The width to length of a cat is a major factor in resistance to rolling. Weight, centre of gravity are also major factors, but so is the grip of the vessel on the water. A Catalac 9m is narrow, but its grip on the water is low, thus any pressure on the side translates primarily into a sideways movement. Early british design cats had quite low rigs and reduced sailplan. Some of the newer fast cats will lift a hull. A factor that I consider to be wrong for a cruising vessel, but these are more hybrid race/cruise. Nevertheless, these designs will naturally tip over much faster than an old british design cat.

    Most Cruising cats, tend more to the ethos of those british designs rather than the hull lifting fast cats, purely because these cruising designs, whilst slower, will also carry weight with much less impact than on the fast hull designs.

    What all of these boats do have in common, is not a problem of capsize, but a potential for a pitchpole. Thus they all need to have a system to slow the boat down. They also have to have a proper fitting to hold that system to the vessel.

  4. #4
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    Default

    I agree with all you have written there.

    I suppose the rule of thumb (which is not mine) is basically to give some idea of the difference if forces required to roll a typical cruising cat compared to a typical cruising monohull. It does take much more force to roll a cat than a monohull.

    I also agree that the greater danger is pitchpoling and the key to avoiding this is reducing speed.

    As I see it - a gust of wind on a mono translates into more roll and spilling wind. The same gust on a cat normally translates into increased speed. Hence the danger of increasing speed until pitch poling is a possibility.

    All of the above is pure theory on my part of course because I am a novice on the learning curve and no more.
    Safe Sailing
    Paul
    Blog: www.suliere.com

  5. #5

    Default

    I read somewhere that most lives are lost due to people falling overboard. This is an area where cats are much safer - they don't roll or heel like the mono's, operations at the mast are metres away from the sides of the boat, and usually at deck level, rather than standing on the coachroof.

    I remember going forward to reef on my old steel mono in around 30 knots, standing up there on the coachroof, with the lifelines at less than knee high only a metre and a half away, with the boat rolling it's arse off, and feeling very vulnerable.

    I stand at the mast of my cat, and look at the lifelines more than 3 metres away, 750 mm high, and KNOW it's a much safer place to be.

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