Old boats into new cat?

Discussion in 'Boat Design' started by newbeeee, Aug 12, 2022.

  1. newbeeee
    Joined: May 2022
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    newbeeee Junior Member

    Just curious, Anyone tried to use 2 sail boats and make them as catamaran ??

    I know it looks stupid option, but so many abandoned boats being salvaged by port authorities and selling them for peanuts, sounds to me an option to build big with small boats. If a working design can be made, it could change the way recycling old boats works!
  2. waikikin
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    waikikin Senior Member

  3. BMcF
    Joined: Mar 2007
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    BMcF Senior Member

    All the structural challenges aside, connecting a pair of typical sailboat hulls side by side would result in a very slow end product, particularly if the spars and sails were from one of the "donors".
    Ilan Voyager likes this.
  4. Ilan Voyager
    Joined: May 2004
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    Ilan Voyager Senior Member

    It's an excellent way to wreck your nerves, throw a lot of money and waste your time. The results are guaranteed disastrous.
    Multihull is not simply tying together several hulls, specially old ones found cheaply at the junkyard. The design of these boats is very specific and has needed years of experimentation and refining. Multis are generally fast displacement hulls, pretty slim and might to use all the juice of the formula ie decoupling hull shape from stability thus optimizing the speed by lowering drastically the drag.
    Monohull sail boats are designed to work heeling somewhere from 8-10 degrees to 20-25 like the skerry cruisers, thin and very heavily ballasted. So the water lines are not specially good upright, specially the old heavy displacement cruising boats.
    And a monohull without ballast is not more in its waterlines.
    The first multis made in Occident in the heavy traditional occidental way of boatbuilding were truly bad and a tendency to fall in pieces.
    The first occidental to understand the concept of multi as thought by the "primitive" non occidental was Nat Herreshoff with the catamaran John Gilpin 1877, cf drawing, and Amaryllis later.
    These designs were totally alien for the yachting world until the designs of Rudy Chow -with Woody Brown and Iwamoto- after WW2 (Manu Kai 1947).
    Last edited: Aug 12, 2022
  5. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    If you are looking for a liveaboard boat, it is a good plan.
  6. rnlock
    Joined: Aug 2016
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    rnlock Senior Member

    I imagine you could make a catamaran that sailed reasonably well, and reasonably fast, from two skinny rowing boats or two kayaks. Until they broke, because they wouldn't be strong enough. There are some fairly simple, crude multihull designs from plywood that might be less work than converting something else. I imagine they'd sail fairly well as long as you didn't compare them to sophisticated multihulls.
  7. comfisherman
    Joined: Apr 2009
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    comfisherman Senior Member

    About 15 years ago some of the fleet was going through a pretty solid consolidation, small boats were essentially valueless whereas boats just over a threshold of capacity were still viable and very expensive. Two identical boats were sitting in the yard one had rolled over and was stripped the other was in pristine condition from years of care. They were seven apart out of the mold in a line of a hundred or so, and it got us thinking..... a match twin repower would make a wild shallow whopper of a catamaran. Hulls were 40x just shy of 12'.

    We pitched the idea to a young naval architect who had crewed his way through college and still augmented his income with fishing. After a but of haggling he traded us for doing some figuring in exchange for us taking him on a hunting trip. Few weeks later he had some figures on how wide the gap would be to get rid of the negative hull interactions, and the forces we'd need to keep the whole mess together.... never mind the concessions or complexities that would be needed to decrease tunnel slap.....

    Suffice to say the idea was shelved.
    Ilan Voyager and BMcF like this.

  8. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    It's about as realistic as turning two old motorcycles into a car.
    Ilan Voyager and BlueBell like this.
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