GOP Home Build

Discussion in 'Boat Design' started by schultzfactor, Oct 25, 2013.

  1. SamSam
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    SamSam Senior Member

    I'm thinking you are going to have issues of displacement, which means the size of the hulls weren't designed to float as much weight as you've already added with wood, fiberglass, etc., much less any big motors.

    You should put it in the water right now, before you add any more weight, and see how it floats.

    Here's a chart that rwatson made on motor weights in kilos.

    [​IMG]

    So, put it in the water and have two guys stand on the back transoms to simulate two 40 hp outboards, while you stand where the center counsel is going to be. Plus put two full gas tanks aboard, two batteries, an anchor and equivalent weights for the center counsel and all supplies like a cooler of food, drinks, ice, fish gear, etc. Lay a few pieces of plywood on where the decks will be. If you plan to take any passengers, add some seating weight and have those passengers get on now. The two guys on the transom don't count as passengers, as they are 'outboard motors' for the moment. It would be best to rig a couple lines to the bows so the 'outboard' guys can lean way back over the water and heavily jump up and down on the transoms, better simulating real outboards.

    As long as it's glassed and the wood is sealed, clean fresh water won't hurt anything, it will dry off. But it will give you a pretty good idea of how it floats and how much weight you can add, if any, and where you can add it.
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    No brackets ! Those skinny hulls will not tolerate that kind of set-up. But as Sam sam says, you need to see whether you can accomodate even transom-hung engines weights. But you would be wise to forget extending the mounting point further aft, some perfectly good power cats turn into dogs that way.
     
  3. schultzfactor
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    schultzfactor Senior Member

    Great thanks. It's in my plan to put it in the water pretty soon. The hulls are actually quite a bit wider than the original ones, but it is something I am worried about. I suppose that is the risk she I just whacked her together. At the top of the tunnel they are 500mm wide and at the bottom they are 220mm wide. I'll make a drawing of the hull profile from the bottom and upload it. At the midship the hulls are nearly 500mm wide at the keel.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    Sounds extremely slender. The ability to bear weight aft will be very limited.
     
  5. schultzfactor
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    schultzfactor Senior Member

    Might be, if I have to change the stern so be it. I have been thinking based on previous comments to create more rocker aft. I'll see how it floats and go from there.
     
  6. schultzfactor
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    schultzfactor Senior Member

    the stern

    here are some pictures with dimensions. thoughts are appreciated thanks. I have a few alternatives if this is really not going to work.

    1. Rebuild the stern and pontoons aft.
    pos: improve hydrodynamics and displacement?
    neg: none really.

    2. add foam sponsons inside each pontoon and fibreglass onto the strucure.
    pos:easy retro fit.
    neg; i know you're going to say unknown hydrodynamics and perhaps a bit ripshy, but then this whole thing is an unknown adventure.

    3. cut out a wedge as drawn.
    pos: easier than rebuild.
    neg: perhaps still not enough displacement.
     

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  7. schultzfactor
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    schultzfactor Senior Member

    hull turned upside down

    might give a clearer understanding of the hull shape.
     

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  8. Yobarnacle
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    Yobarnacle Senior Member

    you might want to install a motor well in the bridge between the hulls, forward of the transom, so the motors weight is forward of the stern and not hung on aft of transom.
    fuel and batteries could be placed even further forward for balance. Maybe under a seat.
     
  9. schultzfactor
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    schultzfactor Senior Member

    Yep that could work well. Ameracat do almost like a tri hull pod for a single outboard pod. I could easily do something similar that would add to the displacement significantly.
     
  10. schultzfactor
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    schultzfactor Senior Member

    centre pod

    Like thismaybe. Ignore the hydrofoils they are just for fun.
     

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  11. schultzfactor
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    schultzfactor Senior Member

    Ameracat hull

    Here is the Ameracat one with a central pod?
     

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  12. Mr Efficiency
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    Mr Efficiency Senior Member

    What is the length of it ?
     
  13. schultzfactor
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    schultzfactor Senior Member

    the centre hull, not sure. I would think itmight be as long as 2m?
     
  14. schultzfactor
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    schultzfactor Senior Member

    and it looks as if this hull goes from symmetric hulls fore to asymmetric aft?
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    No, the length of your boat ?
     
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