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Thread: Thickened epoxy for plywood laps?

  1. #36
    Join Date
    Dec 2012
    Location
    Providence, RI USA
    Posts
    1,230

    Default Re: Thickened epoxy for plywood laps?

    I spoke to the folks at Jamestown Dist. about their Thixo cartridges, and they said it wasn't necessary to pre-coat with unthickened, then they said that you could do it for say, a beveled ply edge.

    I've always coated both surfaces with unthickened and then used thickened in the joint. But what Eric says above rings true. I think I won't coat the face of the ply anymore. It does seem to contribute to running.

    I love the stuff in the cartridges. I'd use it all the time, but the price is a bit dear.
    "near it, a small whale-boat, painted red and blue, the delight of the king's old age."

  2. #37
    Join Date
    Mar 2005
    Location
    Saco, ME
    Posts
    2,131

    Default Re: Thickened epoxy for plywood laps?

    My first build was a Shellback. I used S3 Gelmagic in the laps. I think I used different epoxies to experiment and learn since it was my first boat. But I know a couple laps have the Gelmagic. S3 said that there was no need to coat the end grain with unthickened, contrary to my training! So I put the prethickened, Gelmagic right to it on both sides of the lap joint. I sailed the boat hard for years and the joints were picture perfect when I sold it later.
    Clinton B. Chase
    Portland, Maine

    http://tinyurl.com/myboats

  3. #38
    Join Date
    Dec 2005
    Location
    Shoreline, Washington
    Posts
    2,234

    Default Re: Thickened epoxy for plywood laps?

    Quote Originally Posted by Clinton B Chase View Post
    My first build was a Shellback. I used S3 Gelmagic in the laps. I think I used different epoxies to experiment and learn since it was my first boat. But I know a couple laps have the Gelmagic. S3 said that there was no need to coat the end grain with unthickened, contrary to my training! So I put the prethickened, Gelmagic right to it on both sides of the lap joint. I sailed the boat hard for years and the joints were picture perfect when I sold it later.
    Thanks (also Falcon),
    What I suspected. Does not directly address the question of doing the same thing with your own thickened epoxy goo. But tends to back up my idea that the latter is fine without precoating. Probably best to use a structural filler like silica, cell o fill or fibers, thickened just to the point of not sagging. No thicker. Which takes a little practice. Don't starve the joint, don't be ham handed or overly aggressive drawing the laps together.

    The line up of epoxy products continues to expand. I think the manufacturers ideas about their own products evolve. We all make assumptions, which may have some foundation, but are not always correct.

    PS - I also, near as I recall, did a little bit of everything planking up the 2nd 18 hull. It is difficult to resist the temptation of soaking exposed grain with unthickened product. Seems like reasonable insurance. Won't argue that there are situations when it is prudent and sensible. Pre-sealing adds considerably to the time and tedium of the process. How stupid if not necessary in this case.

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