Proper material for Floor-hull space Aluminum CC

Discussion in 'Boatbuilding' started by fishmore2013, Dec 14, 2015.

  1. fishmore2013
    Joined: Dec 2015
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    Location: Connecticut

    fishmore2013 New Member

    I just installed a floor in a 1982 Sylvan Aluminu hull CC
    I used marine grade plywood for the deck, polyurethaned
    the deck and I have a 1-2' space from the edge of the floor to the Hull.
    Since the hull is aluminum I can't use fiberglass and the span is too wide for caulk.
    Anyone know of an adhesive that would work in this application?
    Thanks Jon
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    "The deck and I have a 1-2' space". Do you mean 1-2 inches or feet? So basically the fit is really poor and you want to fill the gap. A trim piece would be the easiest and nicest quality finish. You can use flexible PVC trim from companies like Taco.
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    I'll assume you have a 1" - 2" space around the plywood decking perimeter. This is a pretty big gap, but you have two approaches. The first is to leave the gap, which will let standing and boarding water drain below, where it can trickle back to the transom plug and of course, the other is to seal the sole (plywood) to the hull sides.

    If it was me, I'd leave the gap and let moisture drain below, so it can run aft and get out. Additionally, this will permit some ventilation for the plywood in the bilge, so it can wet/dry cycle naturally, preventing rot, as polyurethane isn't waterproofing anything, unless it's a 30 mil thick coating (or better).

    Gonzo's idea of a perimeter trim piece would work, bonding the sole to the hull if desired. You could also fillet and 'glass the sole to the hull shell, though you'll want to use a high elongation resin formulation, such as G-Flex, instead of regular goo, so the different expansion rates can be accommodated.

    A bonded sole will likely create a hard point along the contact area, so if you do this, make the 'glass "tabbing" generous, to help mitigate this trait.

    On your boat the ribs are providing the structure, so bonding the sole to the hull shell isn't necessary and I'd avoid it, but some like an easy to hose out deck, which suggests a bonded sole. It's your call, but since the plywood isn't encapsulated, the best choice is to have some ventilation below it, with an open perimeter.

  4. fishmore2013
    Joined: Dec 2015
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    Location: Connecticut

    fishmore2013 New Member


    Thanks for the replies
    Yes 1-2" not feet
    I had some trouble getting the front deck to fit right because the last to stringers
    Are 1"higher than the others leaving the gap
    The trim piece is a great idea
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