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Thread: Building frames for ply on frame construction

  1. #1
    Join Date
    Dec 2002
    Location
    San Diego
    Posts
    122

    Default Building frames for ply on frame construction

    Building out the frames for Spira design. She is flat bottomed. Bottom frame is acrewed and glued to side frame, they meet face to face, not end to end.

    If I plane those faces flat, I cant see any reason to use thickened epoxy, just straight epoxy. Anyone disagree?

    On my next build of this type, I was thinking end to end with plywood gussets, also glued and screwed, would be better, but I cant say why or say for aure that is true. Anyone have a thought on the matter?

  2. #2
    Join Date
    Mar 2015
    Location
    Auckland, New Zealand
    Posts
    50

    Default Re: Building frames for ply on frame construction

    need to watch for absorption of the epoxy into the wood , not enough epoxy and you will end up with a starved joint , thickened epoxy tends to stay put .

  3. #3
    Join Date
    Nov 2011
    Posts
    5,322

    Default Re: Building frames for ply on frame construction

    I think it will boil down to the relative strength of the ply itself plus the amount of glued surface area, but I don't see it as necessary

  4. #4
    Join Date
    Jun 2000
    Location
    Pleasant Valley NS Canada
    Posts
    15,316

    Default Re: Building frames for ply on frame construction

    Use thickened epoxy; it is much more forgiving of minor irregularities in surface prep.

    Using gussets (sometimes called 'cheeks') to marry frames to floors is an old and proven technique. Size, number of fasteners and configuration is important, though, so do your due diligence and do some research on the subject.
    Hope for the best, but plan for the worst.

  5. #5
    Join Date
    Apr 2014
    Location
    Anchorage, Alaska
    Posts
    263

    Default Re: Building frames for ply on frame construction

    Quote Originally Posted by Gib Etheridge View Post
    I think it will boil down to the relative strength of the ply itself plus the amount of glued surface area
    I agree. My under-sophisticated destructive examinations convinced me that the plywood ply-to-ply strength is the weak link. The glue surface area needs to be large. That is accomplished with fillets of thickened poxy and fiberglass.

    Note that my fillet never failed. The plywood (BS1088) always failed by delamination.









    Read more at http://boatbw.blogspot.com/2016/02/d...ze-matter.html


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  6. #6
    Join Date
    Jan 2010
    Location
    Northern Europe
    Posts
    9,211

    Default Re: Building frames for ply on frame construction

    Correctly sized gussets should not come under enough strain to fracture. Im not sure up to what size what size of craft lapped frames were.are used, but obviously the frame size itself limits glue and bolting area.

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