Which cat is this?

Discussion in 'Multihulls' started by sigurd, May 28, 2016.

  1. sigurd
    Joined: Jun 2004
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    Location: norway

    sigurd Pompuous Pangolin

    I don't think anyone uses it - anyone know it?

    Attached Files:

  2. catsketcher
    Joined: Mar 2006
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    Location: Australia

    catsketcher Senior Member

    Pretty hard to tell with that shot but looks like a Shuttleworth Spectrum 42
  3. Steve W
    Joined: Jul 2004
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    Location: Duluth, Minnesota

    Steve W Senior Member

    Wow, that's quite a place to haul out.
  4. Manfred.pech
    Joined: Apr 2010
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    Location: EU

    Manfred.pech Senior Member

  5. catsketcher
    Joined: Mar 2006
    Posts: 1,306
    Likes: 148, Points: 63, Legacy Rep: 790
    Location: Australia

    catsketcher Senior Member

    Look at that antifoul

    Just a heads up for anyone interested in using a similar hull flare to the Spectrum - be careful.

    Look at the antifoul on the pic Manfred included. It goes ALL the way up to the flared chine. Something smells off here. That chine should be about 250 mm above the waterline. Look at the nacelle as well. You shouldn't really have to antifoul a nacelle and this one has heaps.

    I saw a Shuttleworth in the same condition in the Burnett River at Bundaberg. Over years it had gotten heavier and heavier and the low down flare went from maybe 200mm above the waterline to right on it. The boat now had 7:1 wide hulls and would be a real dog. Normal hull flare can handle wide variations in load without drastic changes in waterline shape. The Spectrum shape ( also used by Arber and Kerr in Oz to design a few nice cats) has a narrow waterline that flares within 300mm to a wide shape. If you do not design the boat with enough flotation it will sink so that the flare gets close to the water - or even in the water. This drastically changes the hull shape. Go back to the first pic at top and see where the antifoul is. This is how the boat is designed to float. They are great boats but do not do well when overbuilt or used to carry too much load.

    So if anyone is thinking of using this hull shape be extremely careful! You cannot just add 1m onto the transom like many designers do when they get the weight study wrong. Also if you would like to buy one - check out that the boat has all the flotation required for all of your gear to get her down the DWL. Don't even think of buying one already low without cruising stores. Remember the leeward hull still has to immerse more deeply when sailing.

    I actually like this hull shape BUT it has some limitations. The folding cats I built have this shape so I do have the experience with it. My larger version has a transom extension but I also am going to foam up the aft sections in a couple of months because I put the calculated CB further forward than the real CG and the boats came out heavier than I thought. (Boats always come out heavier - its just a question of how much)


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