infusion and cold mold foam strip planking

Discussion in 'Fiberglass and Composite Boat Building' started by groper, Nov 6, 2011.

  1. groper
    Joined: Jun 2011
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    Location: australia

    groper Senior Member

    Well i thought id start a new thread as i cannot find much information besides "fram`s" blog of the Farrier F39 tri build.

    What im looking at is a method of building the hull of a 10m power cat i have designed below, but obviously these principals could be applied to anything. [​IMG]

    I was initially thinking of making infused panels or buying DuFlex panels and having them CNC cut to the desired plan then taping them together, but after consideration i think vertical foam stripping then infusing the entire hull is probably a faster, and easier method. I might still use the CNC cut duflex panels for the bulkheads, then tape them in after the hull is infused to save a bit more time there.

    What im thinking of, is making the mold in a similar fashion to the farrier vertical foam strip system, except i do not plan on joining 2 halfs together. Instead, i was thinking of building a full mold including bridgedeck to infuse the entire inner (or outer) skin from keel to sheer in 1 shot, then turn the boat over and repeat for the other side.

    Some things Im not sure of;

    A female or male mold ie. inside first or outside first? I think either is doable, but as to which is best/easier i dont know...?

    How to seal the edges of an open mold for the vacuum bag? Do you hand laminate a thin strip around the edge before your layup and then seal the bag onto this or is there another way?

    Ill upload more images/drawings of the modelled setup as things become clearer... i can/will smooth out the chines using a vertical foam strip method as opposed to a flat panel construction.

    The hull upside down... [​IMG]

    I hope some of you can help by sharing your experiences.
     
  2. fcfc
    Joined: Feb 2005
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    Location: france,europe

    fcfc Senior Member

    Beware : my advice is subject to caution.

    You need a female mold.

    Why I think so:

    You put the foam, then inner skin. Then some internal stringers and bulkheads. With one skin only, I doubt you could turn the hull to do the other side. Half skinned, a sandwich is nothing.

    With a male mold, you could do only the outer skin. I do not think the hull would be rigid enough to be turned.
     
  3. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    It will be plenty strong, with the male mould sitting inside.

    You can roughly follow the Fram method, although I am not sure whether the vertical strips will be benificial to you. For what I see of your drawings, these are basicly chined hulls? If so, you can simply use large sheets of foam, and use these for closing the male mould frames. Then either make them 100% airtight (and test), then infuse, or apply a hand laminate first (airtight), then infuse. Or do not bother at all, and hand laminate. (good crew recommended).

    Another option is to apply the inner skin to the unbent foam panels first, closing the mould with these panels, then apply an outer skin. Compared to Duflex, it saves you a lot of force bending the panels in shape, and you have a continuous outer layer of fiber.
    After turning over, you will need to glass the seams on the inside, though.
     
  4. groper
    Joined: Jun 2011
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    Location: australia

    groper Senior Member

    thanks herman, i initially have drawn the hull with chines as i was planning on using duflex - however now i am thinking of infusing, i am in the process of re drawing the boat and smoothing out the chines so i have continuous curvature - which i think looks MUCH better so far, those chines were ugly...

    i was going to run the router down each join like Fram`s method, then apply bog to join each sheet together and seal them... do you bog the edges of the foam to make a place to seal the vacuum bag onto?

    The part that concerns me is the bottom of the hull nearest the bow... i have a very thin and fine entry hull shape that would be better suited to being built in 2 halves, split vertically down the middle then joined together later. However that kinda defeats the simplicity of infusing the entire skin in 1 shot. So i might have to strip plank the hull bottoms to get the shape i need - im not sure?
     
  5. Sand crab
    Joined: Feb 2011
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    Location: Montana

    Sand crab Junior Member

    Kss

    Are you aware of Derek Kelsalls Kss system? Basically you start your hulls as one very large sheet of flat fiberglass. You cut long tapered slits in each end and fold the 2 sides up. The slits come together and form the bow and stern and voila there's your hull shape, some clamping and bracing, and it's now ready for core. It's supposed to save alot of time on forming molds. Numerous vids on Youtube and check his website out. He has plans for power cats, also. BOB
     
  6. groper
    Joined: Jun 2011
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    Location: australia

    groper Senior Member

    Yes im aware of the KSS system, however i do not think it is adaptable to a hull of this shape, or is there something i am missing here?
     

  7. CatBuilder

    CatBuilder Previous Member

    It is adaptable. In fact, Derek will take any design and make KSS plans for it.

    There are a million and one ways to do this stuff. I'd advise to pick the way that nets you the most fair outer surface of the hull from the start. (except don't make an entire real mold up for a one off)
     
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