filling holes

Discussion in 'Boatbuilding' started by TOALL, Jun 20, 2016.

  1. TOALL
    Joined: Jun 2016
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    TOALL Junior Member

    once the strip plank hull has been completed you are left with hundreds of holes where the temporary fixings have been removed. Is it simply a case of squeezing in some thickened epoxy.
    Surely air will prevent it from fully filling the hole. Will this theatrically be a route for water penetration/migration
    if perfection is needed should each hope be enlarged so it can be applied by syringe to ensure its fully filled. This seems madness considering the amount of fixing holes during the build of a 50ft hull
     
  2. PAR
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    PAR Yacht Designer/Builder

    If memory serves me, you'll be applying about 36 ounces of fabric over the exterior of these strips, right? Wet out the holes with straight epoxy, then use the "mash and go" technique to fill the holes. You can fine tune any dents and divots in the fairing process, before the sheathing goes down. Once you've filled the holes and put 36 ounces of goo and fabric over it, you'll be pretty secure from potential leak points.

    Not all strip planking techniques require hundreds of temporary fasteners. Look up the fishing line (monofilament) trick, to holds strips in place, until to goo cures.
     
  3. gonzo
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    gonzo Senior Member

    Consider that wood is a bunch of empty tubes glued together. Small pinholes are not structurally significant. You can "mash in" some putty. The main problem with the holes is that if you don't putty over them, when the resin starts curing and heating up, they will create air bubbles under the laminate.
     
  4. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    Seconded, even tape(s) can be used to hold a few strips at a time, reverse clamping from the frames, and a lot of Spanish windlass techniques. TBH if you use staples (especially with tacking strips) the holes are pretty insignificant and will fill with neat epoxy.
     
  5. PAR
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    PAR Yacht Designer/Builder

    Plastic staples can be left in place and sanded right over.
     
  6. rwatson
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    rwatson Senior Member

    Your concerns are real. However, the cure for getting epoxy into the small holes is to slightly warm the epoxy as you roll it, and enough goo will then displace the air in the holes. try ribbed metal rollers first.
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Filling holes is a two stage process. The first is to wet out the hole with straight epoxy. This can be done with a putty knife or one of a number of tools. Mash it in the hole using the blade to force it in. Capillary action will cause it to seek out the very corners within it. The idea is to wet the inside of the hole, priming it for the filling. Wait a few minutes for the goo to soak in as you mix a thickened batch and go over the hole again, mashing it in hard with the knife, plastic applicator, etc. Smear this off dead flush with the surface or just a little shy of flush. This is the first stage. When the goo has kicked off, mix up a fairing compound and apply a slightly proud puddle over the hole. This is the second stage and what you will sand flush with the surrounding surfaces.

    I dislike warming epoxy and applying it to a cooler surface. This just warms up the open cells in the wood and the air in them, which form bubbles that will rise to the surface and make pin holes. I do it the other way, by warming the wood. This causes the gases in the cells to expand a bit. Then I remove the heat and apply the goo. The cooler epoxy causes the air in the cells to contract, which causes the epoxy to get sucked into the cells and no bubbles. I also try to insure there's a shallow dimple at the top of the hole, so the fairing compound has a divot to get a hold of, when it's applied. Some will tell you all this can be done in one shot, but I've never been able to do it reliably, so I just assume there's going to be slight divots over each and top them off later, with something easy to sand.

    Lastly, decide on what the hole needs to do. If it's part of a structural element, use a structural filler to initially fill the hole. This will retain the integrity of the area around it, if compression/tension loads try to distort the hole. If the hole is just a cosmetic consideration, then fill it with a fairing compound. For example around chain plates or other hardware attachments, I'll use a structural mix to fill the hole, but if it's a few temporary holes where a butt block or scarf was held until it cured, then fairing compound.
     
  8. rwatson
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    rwatson Senior Member

    "I dislike warming epoxy and applying it to a cooler surface. This just warms up the open cells in the wood and the air in them, which form bubbles that will rise to the surface and make pin holes. I do it the other way, by warming the wood."

    Really ? If the holes open up, where do you think the warm epoxy will run to ? Its not like the epoxy stays warmer than the hull for very long.

    Never seen that problem, except for traditional "outgassing", which is caused by .... the hull getting warmer.
     
  9. PAR
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    PAR Yacht Designer/Builder

    I don't have outgassing issues, because of the technique I use on initial raw wood coatings, but I have seen pin holes, when filling screw holes, if warmer epoxy is applied to a cooler (raw) substrate. For epoxy to draw into the cells, the air inside needs to be warmer than the epoxy and (most importantly) cooling down during application. This causes the contracting air in the cells, to suck in the goo. If done in reverse, the goo raises even if slightly, the cellular air temperature and this prevents the cells, from sucking in as much as they can, while this air is expanding.

    This said, you can use the "hot on hot" method, which I do regularly. This is to raise the temperature of the raw substrate and also the goo. The substrate is moved or has the heat removed and is permitted to start cooling, before the warm goo goes on. Now, this also works quite well. I usually try to have a 10 degree temperature difference between the goo and the substrate (cooler goo), so the contraction thing can still occur.

    To solve outgassing, all a raw wood surface needs is no pools of goo. If the surface is scraped clean, while applying the neat epoxy, no pools can form, therefore no bubbles can rise up through them.
     

  10. ElGringo
    Joined: Mar 2014
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    ElGringo Senior Member

    I have never used plastic staples. I can find a lot of places that sell them but little information about using them. How thick will they staple? What materials will they staple. Did the work great?, good?, or just OK?
     
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