Building small race boat form a mold

Discussion in 'Boatbuilding' started by ber1023, Jun 29, 2016.

  1. ber1023
    Joined: May 2008
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    ber1023 Junior Member

    Good day,

    I have a mold of a 12ft ish race style boat that someone made originally in wood. I want to make a cored fiberglass version and plan to run at speeds of around 30mph and it will take heavy wave abuse. My primary question is how do i go about the strakes on the bottom? Do i bag 1 layer of fiber, then fill in the strakes with dense foam and then put another layer of glass down with divinycell (3/8") and then bag again (then matching the lay up on the inside). My lay up i was thinking would be

    6oz S glass,(fill strakes so its all flat), 6oz Sglass, 3/8" Divinycell, 6oz S glass, 6oz S glass

    the boat will have stringers and such, I am trying to make it as light as possible, being on the edge of breaking is fine. Will be used for race use only

    Thanks
     
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I've just designed a 11' 9" pocket racer, much like the old hydro classes once had, but it's intended to take on rougher water, so has more deadrise, slightly more beam, freeboard, etc. If you take one of the old style class racers out in a chop, you'll just get pounded to death, regardless of the number and size of strakes you install. In fact, strakes will likely make things worse.

    What class are you going to run in and does the sanctioning body have scantling regulations? Is the design well suited for "heavy wave abuse"?
     
  3. ber1023
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    ber1023 Junior Member

    no rules, its as suited for rough water as a little 12ft boat can really get while doing over 30mph with a stock 9.9
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    How did you come to this conclusion? Most of these little class racers are shallow deadrise, warped bottom designs, which aren't well suited all all.

    This (attached) is much better suited than the typical hydro class racers, having about 3 times the deadrise normally seen on this style of design.

    [​IMG]

    This 9' design is typical (J class above) and you can see it's a flat bottom with a fine entry. It'll jump up on plane, then pound unmercifully once over the mid 20's.

    Below is about the same size and class as mine, except it's a warped bottom with maybe 4 degrees of deadrise. It too will pound badly.

    [​IMG]
     

    Attached Files:

  5. gonzo
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    gonzo Senior Member

    Those boats will flip in heavy waves at 30MPH.
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    A light lay-up in the strake recesses, fill flush with lightweight filler, then start the lay-up proper, I'd say.
     
  7. ber1023
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    ber1023 Junior Member

    the boat is more similar to a winrace or seaflyer opposed to those glenL racers. Look up winrace boat on googlee
     
  8. ber1023
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    ber1023 Junior Member

    what do you consider a lightweight filler?
     

  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    There's a lot of ways to build strakes up. I prefer to bulk up with hard stuff (plywood usually), then use a filler to tune them up. If this is in a mold, you'd put the appropriate laminate down, then whatever bulking material you like. If it's an all goo laminate, microballoons and phenol or quartz spheres are light bulking fillers. I'd toos in a fair percentage of milled fibers to toughen them for impact.
     
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