Transom Replacement--First Time Rebuilder

Discussion in 'Fiberglass and Composite Boat Building' started by Chris Warren, May 2, 2018.

  1. Chris Warren
    Joined: May 2018
    Posts: 3
    Likes: 0, Points: 1
    Location: Murfreesboro, TN

    Chris Warren New Member

    Hi all, and thanks in advance for advice.
    Last year I put together a great kit for a 12' wood-duck hybrid kayak. I learned a lot about working with Fiberglass then, but this past year a friend gave me their old bass boat. I didn't know what I was getting into.

    I thought there would just be minor repairs, but the transom wood was rotten. I will probably be pulling up the floor and replacing that (maybe stringers too) but right now, I am working on the transom.

    I decided to do this from the outside, which probably wasn't the best way to go, but can't recross that bridge. Anyway, I cut the plywood and got it to fit tightly, but not perfectly in the back between the inside of the transom and the lip I left around the edge.

    I've looked through the posts, and haven't found anyone else asking these questions. Please forgive if I missed it.

    There are some gaps between the plywood and the edges. It is very tight in between the fiberglass of the boat, but there is some space on the bottom. Do I need to fill that space? I have already glassed the wood to the boat and the outside has one sheet. There is a little bit of space on the sides to pour something, if necessary. I don't know if it is structurally or waterproofing wise necessary.

    And then, I am going to lay up fiberglass wrapping around the edges (four sheets, one wraps 2 inches, the next four, etc up to eight) but the glass is much springier than the type I used on the kayak. How do you glass well around 90 degree edges?

    The pictures below are 1) the transom cleaned out, 2) the transom with plywood replaced. The outside plywood there is to hold the fiberglass on with wax paper while it laminated.

    Thanks again,
     
  2. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I recommend throwing the boat away at this point.

    Very sorry, but I tell it like I see it.

    Too many mistakes made early.
     
  3. Chris Warren
    Joined: May 2018
    Posts: 3
    Likes: 0, Points: 1
    Location: Murfreesboro, TN

    Chris Warren New Member

    Thanks, fallguy, but help me out. What were the mistakes? I removed the old wood, made a new wood transom, and glassed it in where the old wood was. The fit is good, but not perfect. I was just wondering if the small space between the bottom of the wood and the fiberglass of the boat needed a filler. Was that the mistake? Not putting a filler in ahead of time? Or is it the need to glass around the edges?
     
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    Making the core fit well takes time and isn't easy, but now the deed is done. It would be nice if the gaps were filled, which can be thickened epoxy, with lots of milled fibers. Let it "flow" into the spaces as best as practical, then hope for the best.

    If you still have the old exterior skin, you can save some time and materials, by bonding this back on. If not, you'll need to bulk up the outer surfaces so it's about the same thickness as the old one, then the fun of fairing and smoothing it, before paint.

    Have you any images of the now installed core, without the flake board covering things up?
     
    Last edited: May 2, 2018
  5. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    if you have edge voids, how did you bond the plywood to the inside lamiante? Supposed to bed in thickened glue and clamp it to the inside skin. How did you clamp it?
     
  6. Chris Warren
    Joined: May 2018
    Posts: 3
    Likes: 0, Points: 1
    Location: Murfreesboro, TN

    Chris Warren New Member

    I might have misled you. I was trying to be clear, but might have given a false impression.

    I cut out the wood for the transom and it fit very well. It wasn't perfect, and I was wondering about those small gaps like you will see in the picture that happen. The transom wood was laminated to the inside transom fiberglass by coating both the wood and the inside fiberglass and then wetting down a sheet of fiberglass weave. The weave was wrapped around the wood so that it laminated to both the inside fiberglass and the lip that was left of the outside fiberglass. I ran screws through the inside fiberglass into the transom wood to make sure there was good pressure for the lamination.

    The wood was to thick to fit in the transom to begin with. I used two pieces of 3/4 outdoor rated plywood, but had to grind it considerably to make a good fit. When it did go in, the wood where it wasn't ground out was the same level as the outer transom lip, so I put a sheet over the entire outside of the transom. I will now put four layers... One weave, then mat, then weave, then mat and wrap around the sides. I am sending a picture of the outside of the transom with one layer of mat, the inside of the transom so you can see that it is laminated there, and the side where there is a small gap between the transom wood and the side. That small gap is what I was asking about, not something that would keep the inside fiberglass from laminating to the wood.
    Thanks again for the help.

    By the way, the wood is considerably higher than it needs to be. The top of the transom will be where the darker fiberglass starts on the picture of the inside. The part that isn't laminated at the top of that picture is going to be cut away.

    The gap you see used to be just foam anyway. I was wondering about if the wood wasn't completely flush all around the bottom.
     

    Attached Files:

  7. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    The biggest mistake was cutting it from the outside, then, cutting it right at the edge.

    You need to leave about 4" of the actual transom around the edge so you have something to bond to, wrapping the glass around onto the hull can create all kinds of issues when the boat is running at speed. And with a rotten transom there's about 110% chance the stringers are rotten too, doing everying at one time from the inside is much easier.
     
  8. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I replace transom cores from the outside about 50% of the time. It's usually a budget thing and I find the outside skin removal method, a lot easier then puzzling together the cut up inner liner. At this point he needs to grind back the topside, sufficiently enough so he can apply enough fabric to transition from new to old work, without a bulge. If it was me, I'd stop at this point and concentrate on this, before any additional fabrics go it.

    What resin system are you using?, What fabrics? Amount of overlap from the old work to the new do these fabrics enjoy? Was the plywood properly sealed before inserted and bonded to the liner? Your transom core may be strong enough, though the bond to the hull shell is critical. This is usually done on both sides of the plywood, but since it's in already, you'd better get a really good bond on the outside. This will likely mean you'll need to grind back the hull shell, more then 12:1 and extra fabrics employed to help compensate for the lack of it internally.
     
  9. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Where to begin...

    First, a general comment. Ask first!

    Second. Gut the boat. See what you have to fix.

    3. Report the rating plate max hp.

    4. See if you can peel off the outer layer of glass. It was a mistake. What is it? If it is thin csm; just leave it if it won't peel off.

    5. Report back the glue (poly)? And the csm weights.

    Some rambling general comments for you.

    Transom plywood is typically bolted onto the laminate on reverse by using bolts and clamping boards to get enough pressure to squeeze out a peanut butter mix of thickened glue. Glues are thickened with cabosil about 2:1 cab to glue. The fact you used screws means you probably created voids in the repair. Those holes need repair as they allow ingress. The fact you are asking about voids means you didn't do it the way i would expect. If the plywood didn't lay down right as it sounds; this is probably due to clamping fail.

    Don't add more than two layers of 3/4" ply. Typical transom thickness is 2". Some motors will require cutting tabs off if you go bigger. The 2" thickness is achieved by glasswork.

    The top of the plywood cannot be exposed at the end. Wrapping it with the glasswork is important to keep the edges from opening.

    In order to get a different glass to wrap; you need to form a radius on the hull edge that will require resahping later. I use a 1/4 sheet electric sander to form a 1/4" 45 degree flat; then I round it out with 36 grit floor paper from HD. In your case; you need to grind off the gelcoat about ?8" (see what PAR says) on the hull sides and bottom and then form the radius for the glass. After glassing; on a planing hull you need to fair back to a sharp edge.

    Poly on plywood is not great. Poly is not waterproof.

    Transom repairs done by amateurs wrong can result in death. An aquaintance of mine had friends die when the transom fell off. Iirc; four people perished.

    I don't trust your approach so I still recommend junking it.
     

  10. ondarvr
    Joined: Dec 2005
    Posts: 1,895
    Likes: 114, Points: 63, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    Yes it can be done from the outside, but like I said, it's very likely everything is rotten and it needs to be gutted. Once the interior is stripped away the transom is easy to do from the inside.

    Now he has all the hassles of both methods with significantly more time and money required.
     
    Last edited: May 5, 2018
    fallguy likes this.
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