Fiberglassing a hydro. Need some advice.

Discussion in 'Powerboats' started by Shreve, Jul 28, 2016.

  1. Shreve
    Joined: Aug 2015
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    Location: Columbia, MD

    Shreve New Member

    Greetings folks. I'm getting ready to fiberglass this Hal Kelly design, and I'm stumped on how to proceed. I've built surfboards in the past, but they're a different animal. Not sure about cloth direction, size. Many small pieces? Horizontal? Side to side? Bow to stern?

    Take a look at the photos and see what you think. Any advice appreciated. Thanks in advance! Shreve


  2. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Does Hal Kelly say anything about what to use or how?

    It looks like the junction of the sides and bottom isn't beveled and the edges of the bottom stand proud, the same with the sponsons and transom. That will be a nuisance to cover and I doubt it would be possible to 'wrap' the glass around edges like that unless it was extremely vacuum bagged.

    I would use as big of pieces as possible. If you have to lap crosswise, I would do it so the laps won't allow water to peel them apart, so that would be from the stern to the bow. It might not matter with epoxy, but it can't hurt anyway.

    Some people say put the cloth on the bare wood and then apply resin, but I have never had that work good. For me it always ended up with patches of resin starved glass, which is not repairable by putting more resin on after the resin has set or even started to set.

    If the boat is only in the water for short periods of time, like racing or a few hours in the day, I'm not sure I'd even glass it.
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Fir plywood tends to check badly. If it is not for structural purposes, 4oz. cloth with epoxy will be enough.
  4. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Yes, I didn't think about that.
  5. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    Yes, epoxy all the way. Find a system to use for lightweight build. Not a big boat look at West systems.
  6. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I disagree on the 4 ounce cloth on Douglas fir. I've seen it check under 8 ounce.

    Log onto and download their "Epoxy Book" and and download their user's guides and boat building book. These are all free and good references to check or to learn.

    It appears you need to ease several edges to get the fabric to "lay down" properly. These edges can be built up again after the sheathing. Fair the hull well, before the sheathing goes on. This will save you countless hours of cursing afterward. Lastly, does this boat "need" to be sheathed? I built quite a few of these as a kid and young man and we rarely sheathed them, just faired and painted to save weight.

    You can use West System or one of the other major brands if you like, or you could use one of the discount goo's at over half the price. Check out RAKA, and for alternative formulations that are just as good as the major players.

    As to fabric application, the bolts only come in two (generally) sizes, so you'll have some seams. Use common sense and layout the fabric to be most economical. Cloth doesn't have a specific orientation requirement in this application. If it was me, I'd run one piece right down the middle, overlapping the chines a few inches, if the boat's beam will permit. I'd do the bottom first, then work up the sides with healthy overlaps.
  7. Forestgnome
    Joined: Jul 2014
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    Location: Sacramento, CA

    Forestgnome New Member

    Normally the small racing hydros don't get glassed. The edges need to stay sharp to help it track in the turns. They usually just get epoxied.

  8. pjak
    Joined: Nov 2016
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    Location: NZ

    pjak New Member

    One question. Are you building a boat in your lounge? Haha that's classic
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