Would that catamaran ever sail?

Discussion in 'Boat Design' started by john5346, Apr 23, 2013.

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  1. john5346
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    john5346 Junior Member

    I made that design, a rectangle with a triangular bow and a flat bottom.

    Do you think that would sail? I dont understand anything about design of boats but using some plywood, I could make that so easy and quickly.

    Length, lets say 17 feet, width of each hull about 23 inches.


    If you say it would sail, then I will build only that type of boat. It will be all I will ever need in term of boats. Thank you. If I need something bigger, then I will build a 27 feet version.

    Would it sail?
     

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  2. messabout
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    messabout Senior Member

    Yes your boat will sail but even a bathtub can be made to sail. As drawn it will sail but not very well.

    Twenty three inch hulls will be wider than is ideal for a 17 foot cat. You also will need to raise the ends of the bottom a little bit. The transom end or back end of the bottom needs to rise up slightly above the waterline. As you have it drawn, it might make a reasonably adequate power boat but not a sailboat.

    I would urge you to get some professionally done plans for your build. There are many available and some for very little money.
     
  3. Richard Woods
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    Richard Woods Woods Designs

    Making the hulls for a beach cat is the quick and easy bit. It is the rig and deck gear that costs the money.

    You need to think about steering, how to attach the crossbeams, how to distribute the downforce from the mast into the hulls. How to prevent leeway, how to make the deck a comfortable platform to sit on, unless you plan to trapeze.

    Most beach cat hulls will be 18in wide or less

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  4. john5346
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    john5346 Junior Member


    Yes but how much efficiency will the hull lose by not being professionally designed? Lets say it is only 60%-80%, does that even matter? Now if it is something like only 10% of efficiency against a professional hull then it makes sense. Any way to test it by math or software simulation?

    How about a good guess, how bad would it be if it was in that form?
     
  5. john5346
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    john5346 Junior Member


    How about a junk rig or lug sail? Looks slower but it still sails fine, no?
     
  6. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Try the free program "Michlet".
    www.cyberiad.net/michlet.htm

    If the program is too tough for you, I can help out for a small fee.
     
  7. alan white
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    alan white Senior Member

    Many novices have come to this forum with designs that they came up with that have squarish hulls (no curves) because, I think, they assume that square shapes are infinitely easier to build than curved ones.
    There's nothing outlandishly difficult about building a curved hull. But those "corners" are awfully inefficient when pushed though the water.
    What is so difficult about making the hull curved (sides and bottom, fore and aft)?
    Anyone can do it. It should be fun!
     
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  8. john5346
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    john5346 Junior Member

    That is a nice software, anyone able to calculate the results?

    I dont know why it happens alan, I only think that a hull shape should cut the water and it feels like a triangular bow with a squarish hull would do the job just fine. People make sailing rafts and old cultures used log canoes and they sailed. Only example of free form sailing.

    Now why do people that are experts think that a squarish hull with a triangular bow moves inneficient through water? I dont want to defend my "design", it is only really a way to understand how professionals reach that conclusion without testing it, how is it so obvious? Since professionals never built squarish hulls with triangular bows, at least I never seen any boat like that.

    Link to any studies, testing or personal experience watching or building a squarish hull and its efficiency compared to a curved hull?
     
  9. Petros
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    Petros Senior Member

    people who study, design and test hull shapes, or do other fluid mechanics analysis, know without doing any analysis that a hull like that will have a lot of drag. It is not really much more work to build a hard chined but curved hull, and it will perform better.

    here is a link to some free plans for an all wood catamaran. It is an old design and performace will not be up to current standards, but it will be much better than what you have and is a proven design. You should be able to build it with all locally available materials.

    http://svensons.com/boat/?p=SailBoats/Hobby_Kat

    [​IMG]

    [​IMG]
     
  10. DennisRB
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    DennisRB Senior Member

    Here is what happens when someone with no experience tries to outsmart the professionals with a triangle shaped boat. Huge claims were made and the actual reality of the performance was not even close to the claims.

    I give the guy 100% for trying and actually finishing the boat. Thats more than what most people achieve, but I bet he wishes he built an existing design.

    http://www.cruisersforum.com/forums/f48/beaus-boat-9093.html

    [​IMG]
     
  11. Leo Lazauskas
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    Leo Lazauskas Senior Member

    I wrote it, so I certainly can. :)
     
  12. john5346
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    john5346 Junior Member

    Thanks for the link, those are cool boats.

    Yes but you dont need to be a professional to realize that his boat is FAT. Even if it was curved, it would still drag a lot. Too much width, not enough length. Now if that was half the width and twice the length, it would move through the water much better, right?
     
  13. john5346
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    john5346 Junior Member

    Then do it, for free. If you want and post the results. :)
     
  14. Petros
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    Petros Senior Member

    Junk rigs are great and perform well at all points of sail except when trying to point high into the wind (a conventional bermuda rig with a jib will point better). the junk is easy to control, they will not flog, the forces are lower so the whole rig is usually lighter, adjustments, trim and reefing are also much easier. I have built several small boats that use them and have enjoyed sailing with a simple junk.

    I do not have as much experience with lug sails, but the few times I have used them I did not find them that easy to work. The forces can also be quite large as well. but they are simple, a balanced lug is better but it requires more parts.
     

  15. Leo Lazauskas
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    Leo Lazauskas Senior Member

    No thanks.
     
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