Finishing corecell end grain at gunwale line

Discussion in 'Fiberglass and Composite Boat Building' started by Ctowles, Mar 5, 2015.

  1. Ctowles
    Joined: Oct 2013
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    Location: Jackson hole, wy

    Ctowles Junior Member

    Im building a whitewater dory. The hull is 1/2" corecell sides. The whole hull is glass but I still have exposed corecell at the end grain of the side panels at the sheer line of the boat. What is the best way to finish this. I plan to bury this in the gunwale arrangement under rabbets in the inwhale and outwhale. Still I feel like this end grain should get glass. I could
    A. Build a jig to router out core and refill with thickened epoxy
    B. Wrap the edge with glass seam tape. I could do this by rounding over one edge and wrapping the joint at 90 degrees, or rounding over both sides and trying to wrap the full panel end grain like an upside down U
    C. Do nothing at all and cover it with the gunwales.

    I know corecell doesn't absorb water and doesn't move it thru the lam with capillary action, but still seems wise the completely encapsulate the foam hull. What's the best treatment for finishing the end grain of the panel at gunwale line?
     
  2. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    Many ways to make it but what I would do: Glue with epoxy a wood strip on top of the sheer line, round the top corners, laminate over the sides with biaxial..
     
  3. jorgepease
    Joined: Feb 2012
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    jorgepease Senior Member

    I think all your options are ok, you can even just fair over it to seal it. If you go the way of router, I used a rotary dremel type thing to do that no jig needed, just a fluted blade with no cutting point, makes for a nice solid edge when you fill it.
     
  4. redreuben
    Joined: Jan 2009
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    redreuben redreuben

    I choose A.
     
  5. snowbirder

    snowbirder Previous Member

    B. You're just trying to keep a delam under control here, as well as keep moisture out.
     
  6. Ctowles
    Joined: Oct 2013
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    Ctowles Junior Member

    Well, I think I'm gonna go option b.

    I did use a couple piece of wood as shims the other day but other than than and the gunwales, the whole boat is cored. Don't see a reason to add wood now. Also, biax at the sheer sounds like overkill, just cause the gunwale arrangement in this boat will be stout. Inwales and outwales with rabbets to cover the end grain, then spacer blocks, then handrails. I feel like reinforcing that joint with biax is just adding complexity in an area that's gonna be solid as it is. I have some 2" tape for this purpose. Debating between rounding over just one side or two. With one the glass only needs to bend a round 90 degree corner, not too hard. If I round over both I have to turn 180 degrees a lot more chances for peeling air bubbles etc on the tape line.i may round over the outside edge and bury that 90 degree corner joint in the gunwales on the inside side of the panel.

    Mixing filler is fine, but as I used plascore on the interior, I filled plenty of stuff with thickened epoxy and am sick of wasting glue and fillers etc. I'd rather add some more glass here which at least adds a bit more structure.
     
  7. redreuben
    Joined: Jan 2009
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    redreuben redreuben

    If you want structure that counts, router out 3mm and fill with uni.
     
  8. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    You could glue a plastic or aluminium extrusion over it, like a channel, of the right size.
     
  9. Ctowles
    Joined: Oct 2013
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    Location: Jackson hole, wy

    Ctowles Junior Member

    Well, let me rephrase that. Glass tape adds something where adding thickened epoxy basically adds nothing. I don't really need more strength here though. The gunwale arrange ment is 3.5-4" thick of mostly solid ash and fir. It's plenty strong and will be stout for everyday rowing. If were talking about adding strength in a catastrophic impact scenerio like slamming a canyon wall or pinning on a boulder, I just don't think that's something you can build for. A couple tows of uni ain't gonna save ya when you crack into a canyon wall at 15mph in a loaded boat. Build it strong enough to survive unscathed and it's a pig to row, build it too light and it crumples like a paper airplane. I try to build for surviving everyday wear and tear, as well as a few big hits. I don't build strong enough to slam the canyon wall.
     
  10. redreuben
    Joined: Jan 2009
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    redreuben redreuben

    No uni won't save it, but its stronger than bog and will be as waterproof as DB without the bulk of wrapping.
     

  11. redreuben
    Joined: Jan 2009
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    redreuben redreuben

    Actually, put in enough filler to cover the open cells then top with a uni cap, all contained within the skins - no bulk.
     
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