Fill screw holes in transom?

Discussion in 'Boatbuilding' started by stimulous check, Jul 13, 2009.

  1. stimulous check
    Joined: Jul 2009
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    stimulous check Junior Member

    I want to remove a pair of trimtabs from my transom - I added them believing they would make my boat plane faster, but in practice found I never used them. Would like to remove and sell them to pay for other parts I would use. The issue is the screw holes. Each tab has sixteen #12 or #14 screw holes and two hydraulic hose fitting holes that are 1/2" diameter. That's a total of 32 screw holes and 4 half-inch diameter holes. What is the best way to fill these?

    In the large holes I have been told to use a 1/2" wood dowel a couple inches long coated with epoxy and drive that into each hole, leaving some amount of hole to fill with epoxy on each side. Is this correct? Do I need to use cloth or glass fiber to prevent cracking over time of the plug?

    Another person said I should enlarge the hole in the wood somehow and fill with epoxy putty so the plug is held in the hole by the skins, the plug being larger than the original hole. This sounds a lot harder then the dowel approach.

    What about the screw holes -- do those need a tiny dowel pounded into each, or can I fill them with epoxy putty only? Or would air voids be a problem if I only packed epoxy putty into each screw hole?
     
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Wet out each hole with neat epoxy, then smash thickened epoxy into them. You can use a wood dowel in the larger holes, but you don't want a tight fit, so there's room for the epoxy to live. Use silica and milled fibers as your thickening agents.
     
  3. Stumble
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    Stumble Senior Member

    I am with Par on this (alwats seem to be), the only thing I would suggest is not using wooden dowels to plug the holes. I would just use thickened epoxy for the whole thing. I can't see any real benefit from useing the dowel, and in this quantity there is no price difference.
     
  4. PAR
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    PAR Yacht Designer/Builder

    The dowels could save on a small amount of goo, but that's it.
     
  5. stimulous check
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    stimulous check Junior Member

    Thanks PAR. Thanks Stumble. And thanks PAR again!

    I will forgo the dowels as I bet I'd use more epoxy trying to coat them properly than simply filling the holes!

    Someone said I should drill out the screw holes because the caulk used is unknown and might contaminate the holes for the epoxy sticking. On the other hand, the holes being threaded from the screws would seem to give them a lot of grab right now and I hate to make them bigger. Any thoughts?

    Another waker-by thought it was blasphemy removing the tabs and filling the holes. The tabs are not used at all on this boat, are worth about $400-450 used, and the boat is worth probably $9,000 total. The epoxy filled holes should be more water-tight over time than the cauked screws at present. But I suppose if I sell her someone will always feel the filled holes are an imperfection. What do you think? Bad thing to do to an old boat, or ok to remove an unused part and fill the holes?
     
  6. PAR
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    PAR Yacht Designer/Builder

    Drill out the screw holes, as this will clean them of any contaminates. The epoxy will soak into the core and bond just fine without threads.

    You can apply a dot or two of paint over the repairs (you have to have something over the exposed epoxy), which should match fairly well if you an novice painter or quite well if you have some experience mixing paint. The transom probably needs to be painted anyway, right, so that will hide any and all flaws for a quick resale. Would you buy a boat that has solid repairs or questionable fasteners showing?
     
  7. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    Par,

    I know epoxy has to be painted to keep the UV from breaking it down, but can you instead of paint just use a coloring agent to do the same thing?
     
  8. apex1

    apex1 Guest

    No! You must paint / varnish it. Colouring agents still leave the surface exposed to UV.
     
  9. PAR
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    PAR Yacht Designer/Builder

    There are a few things you can add to epoxy to dramatically improve UV protection, but the novice can't do this, so you're left with top coating the cured goo.
     
  10. apex1

    apex1 Guest

    Well, should have added: " for the use intended"
    But I doubt the amateur will get 2-Hydroxyphenylbenzotriazole at his local drug shop.
     
  11. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    This is the USA Richard, we can get that stuff on the street corner, in any major city . . .
     

  12. apex1

    apex1 Guest

    Thanks Paul. Good to know, in case i´m there and have a urgent demand!
    Richard
     
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