13' skiff design

Discussion in 'Boat Design' started by canadian cat, Oct 24, 2015.

  1. DCockey
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    DCockey Senior Member

    My understanding is high deadrise aft is only needed for a soft ride if the boat will be launching off of waves with the initial re-entry impact aft.

    I've been studying powerboat hull design for several years by attending conferences, reading papers and journal articles, and reading several recent books. As others have said here it can be complicated with multiple tradeoffs.
     
  2. canadian cat
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    canadian cat Junior Member

    Thank you for the very thoughtful reply I will consider all of your points carefully. At this point I have a 11' rib with aluminium hull and a 15hp two stroke. I am trying to improve on the ride quality of this boat as most everything else is great about it. The light durable hull, just light enough to get off a beach, good power, stable, but the tubes leak and are expensive.

    Do you have some links to examples of the designs you reference. Such as the warped bottom.

    Thanks

     
  3. canadian cat
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    canadian cat Junior Member

  4. PAR
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    PAR Yacht Designer/Builder

    That's full off decades old rubush, not based on any testing or even reasonable observation. Some of the basics are reasonably accurate, but then there's the suction BS, which is just not in keeping with what was well understood at the time of its publish date (1979), let alone now. In fact, to prove this "suction" crap, some enterprising designers drilled holes in some test boats, figuring they'd hear air being sucked into the holes at speed. Instead, they had geysers of water from each hole. So much for the suction theory. Isn't the internet wonderful . . .
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    Haha, you have to admire the ingenuity (?) of that test to debunk the suction theory. I'm afraid the OP has just about made this an impossible quest by stipulating 125 lbs limit, which makes it inevitable that speed and comfort combined, is totally improbable. The only way is to cut the speed requirement right back.
     
  6. messabout
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    messabout Senior Member

    In the dusty part of my bookshelves lies a copy of The Naval Architecture of Planing Hulls. By Lindsay Lord. Copyright 1946. In the book L. Lord insists that the afterplane of warped bottom hulls had "suction" loads. He was a plenty smart guy with all sorts of credentials but he was out to lunch with the suction postulate.

    The author wanted his boats to have Monohedron bottoms where the dead rise was constant after midships. He was wrong about the suction thing but deep vee type boats are sure enough monohedrons.... for an entirely different reason.
     
  7. PAR
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    PAR Yacht Designer/Builder

    Again, we've found the monohedron element to offer some advantages, but these are only applicable on higher speed craft. The disadvantages on modest speed and displacement speed boats just doesn't justify this design aspect, especially if a stable platform is desirable.

    Lindsay Lord's most notable books where before the 63' - 64' series tests that proved the value of monohedron hull forms. Some, such as Hunt and Blount had done some testing and postulated the suction theory was wrong, but no one believed them until these tested spanked the establishment thinking down.

    My effort in pointing this stuff out for the OP, is simply it's a lot more complex a set of variables, then he might realize and plenty of misinformation, is available to make things worse. Each variable has an approach that can be taken, but as always the conflicts need to be addressed to find the best "convolution of discontiguous compromise" possible.
     

  8. philSweet
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    philSweet Senior Member

    If you have what I think you have, it's going to be very, very hard to improve on that.
     
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