Mini Build Questions

Discussion in 'Fiberglass and Composite Boat Building' started by HydroRocket, Jan 6, 2014.

  1. HydroRocket
    Joined: Jul 2012
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    Location: Minnesota

    HydroRocket Junior Member

    I have been planning on building a mini (12 foot or so) speed boat this winter. I was going to sheet it with 1/4" lauan and glass over the inside and outside. I found a couple threads that said this is wasting money because then you're basically making a fiberglass boat with wood core. Is there something else that would work as a better core?
    I'm trying to build the boat as cheap as possible because it's just going to be a prototype and when I get it right I plan on making a fiberglass mold for it.

    Should I go about this at a different angle? Different cores? Is this process okay for making a new mold?

    Thanks in advance.
     
  2. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Wood is a very cheap core.

    Sandwich construction (glass skin, core, glass skin) is a very efficient way to build a hull (weight wise). Wood will not be the lightest possible construction. You could always look for a polyurethane foam, but it will be more expensive.
    Don't let anybody talk you into styrofoam core. It is not strong or stiff (the actual major requirement) and damages easily.

    You could strip plank the boat in cedar - makes a good core, probably more expensive than ply, slightly lighter, able to make nice smooth curves, but will take more time for virtually everyone.

    A plywood core will be quicker in build time, if you already know what you are doing.

    There have been lots of small speed boats - what is different about yours?
    Nothing wrong with doing it just because you want to of course.

    Have fun. My $0.02
     
  3. HydroRocket
    Joined: Jul 2012
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    Location: Minnesota

    HydroRocket Junior Member

    Thanks for the info.

    Its just something I have been wanting to do and I have a different vision of where I would take minis ;-)
     
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    In this size wood or a wooden core build are really your only choices, unless you want to jack the costs with exotic fabrics. A "Lord method" strip plank build will be the lightest, though the "goo factor" will be higher than say a cold molded build, which would also be light.

    By the time your skins are thick enough, over a foam or honeycomb core, to offer penetration and slamming load resistance, you'll be heavier then a Lord build, though you'll be stiffer (inherent nature of a Lord build).

    Plywood will be quick to build and inexpensive. A stripped build can also be inexpensive, if you use cedar strips ripped off larger boards (2x12's for example). I spec'd a 26' sloop recently for strip plank and the strip costs were minimal (a few hundred), though fabric and goo costs where as you'd expect for this square footage.

    How fast do you think you'll run, as this will govern skin and core thickness, in a foam or honeycomb scantlings schedule?
     

  5. HydroRocket
    Joined: Jul 2012
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    Location: Minnesota

    HydroRocket Junior Member

    I would say speeds around 30 mph.
    What should I look into using for a layup on this?
    I'm still learning quite a few of the glassing terms and whatnot. I'm not looking for it to be absolutely as light as can be so a little overkill on the layup will be fine for the prototype boat.
     
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