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Thread: Transom bonding

  1. #1
    Junior Member
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    Transom bonding

    Hi all just looking for some info on decent bonding products for bonding my new transom ply to itself and to the fibreglass on the boat prior to glassing it all back in.
    The transom will comprise of 2 layers of 18mm marine ply as it needs to have the same strength factor as the original transom an be able to support an outboard up to 150hp
    The boat is a Tremlett 21 sportsman.
    I also noted that the Tremlett transom has a curve in it that i'm told is part of the design. There are no signs of structural damage as I have full inspected for such problems.
    So really just looking for the right bonding to do a permanent job as well as be strong enough to hold the ply to the curvature of the transoms.

  2. #2
    Super Moderator Alex's Avatar
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    All the rigidity of the transom is in the wood, the fibreglass is nearly all protection.

    So normal procedure would be to pepper both plys with tiny holes, 2mm or so. Use G4 primer to prime wood surfaces 1 hour prior to bonding. Put a layer of 600g CSM (plus resin) inside the transom outer skin and press prime and holed wood onto, keep pressure until layer of glass set. Resin should ooze out the holes in ply creating a resin 'rivit'. Grind wood smooth. Repeat with second plywood (2 surfaces to prime here, with glass layer in middle) Grind again, fill any gaps (normally edges) with resin and colloidal silica mix the glass over with more 600g CSM, dont forget to prime the ply again!

    The final layers are the most important, the entire area should be MINIMUM 3 layers of 600g CSM (4-5mm) BUT extra is important at the top and any other areas that will take stress from that big outboard.

    Old fashion yes, but effective.
    Paulw73 likes this.

  3. #3
    Junior Member
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    Thanks Alex as always your knowledge shines through.
    I wasn't sure whether or not I would need any sort of special bonding agent to maybe help pack out the potential flex from the bow but yours just confirmed the old method is still affective even in the modern age of fibre glassing products and procedures.
    Time for my order to be placed to get my boat finished now.
    So by the morning you will no doubt be reading my order for completion then weather permitting I will be getting on with the transom by the weekend or early part of next week.
    Thanks again for the info your a star..

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