Epoxy glue questions

Discussion in 'Wooden Boat Building and Restoration' started by mojodad, Feb 20, 2013.

  1. mojodad
    Joined: Feb 2013
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    mojodad Junior Member

    So you guys using thickened epoxy as glue, do you use any nails or screws also or just the epoxy? I'm thinking for a plywood boat like Michalak's jon jr.

  2. mojodad
    Joined: Feb 2013
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    mojodad Junior Member

    One more question. I've never worked with epoxy before. I'm looking at the Raka epoxy. Do you typically use fast cure hardener or a mixture of fast/slow? Michalak suggests fast in his book. I'm working outside it 50-60 degree weather. Thanks.
  3. michael pierzga
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    michael pierzga Senior Member

    Epoxy cure choice depends on the component assembly time and the working temp of your shop . I prefer slow cure for large laminates and Medium for everyday work .

    Im a slow motion type a guy. If youre hyperactive, work with sweat dripping off your nose, need your boat by friday or have a couple helpers, Fast will work

    Fast cure epoxy is prone to waste because it kicks off before its used. When laying a long fillet, fast epoxy will firm up and make it impossible to retouch .

    Viscosity of the resin is also important. I dont know RAKA. Locally I use West and Epiglass. West is Medium Viscosity and Epiglass is thin. Thin epoxy spreads like paint and wets out fabric fast. It also runs downhill and takes extra coats to fill the weave.

    Portable electric heaters overnight are helpful when using slower cure times. In the morning the work piece is cured.

    And no metal fasteners left in the finished product. Fasteners create a path for water to enter. Wood lasts longest if you prevent water ingress.

    Working outside is a problem. Use should build a tent over your boat to control the environment and prevent the epoxy surface from becoming contaminated. The heat shrink plastic boat cover films on top of bent PVC pipe makes a cheap and effective boat shed.
  4. DGreenwood
    Joined: Aug 2004
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    DGreenwood Senior Member

    This is all good advice. I would add:

    The build shed is important and worth your time.

    Download the Gougeon Bros book on epoxy and read it (free on internet)

    Do a few small projects first with cheap plywood to get the hang of it. Epoxy is easy when someone shows you or you take the time to learn to handle it and learn what its capabilities are.

    Oh and read the damn book!
  5. Milehog
    Joined: Aug 2006
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    Milehog Clever Quip

    Dunno about fast hardener for a first timer. Maybe after some experience has been gained.
    The most common epoxy mistakes are improper resin/hardener ratios and failure to thoroughly mix the components.
  6. pauloman
    Joined: Jun 2010
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    pauloman Epoxy Vendor

    that is in the range of a regular cure epoxy. Be sure to use a non blushing epoxy (google epoxy amine blush). Also better to use a real formulated marine epoxy and not epoxy from a bulk repackager. See www.epoxyproducts.com/mepoxies.html for comparing marine epoxy vendors.

    Keep in mind that even the best epoxies cost maybe $40 - $45 a gallon at most to manufacture. A reasonable mark up is acceptable (distributors demand about a 50% discount) still, some vendors laugh all the way to the bank with 300% or 400% mark ups.
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Paul has a good point and a good line of products as well. You can pay over a 100 bucks a gallon or you can shop around. I find Raka a bit thin for most uses.

    Download the free users guides from westsystem.com and systemthree.com. It'll cover most of your questions.
  8. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    And the point being??? None, the op asked about gluing so blush isn't an issue..
  9. dinoa
    Joined: Oct 2007
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    dinoa Senior Member

    Composites have to be designed for joining by mechanical fasteners.

    Bonding composites with epoxy with cotton flox added to the consistency of peanut butter works well. There are special formulations available just for bonding but flox added to a good structural epoxy gets the job done and is good at gap filling. Wet joint with neat epoxy before bonding. If you can, bond while piece is still at green stage.

  10. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    Composites only have to be designed for joining by mechanical fasteners if that is what you are going to do.

    If you don't intend to use fasteners this is wrong, and most of us cannot design the composite anyway.

    Your kayak wouldn't be designed for fasteners.
  11. robwilk37
    Joined: Nov 2010
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    robwilk37 Senior Member

    ive been using raptor composite nails and staples for assembly then glassing over. no need to remove them. the manufacturer recommends a special gun (pretty expensive) but i find my bostich guns work just fine.

  12. dinoa
    Joined: Oct 2007
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    dinoa Senior Member

    When you join composite components with fasteners you are point loading the composite. An isotropic lay up must be made heavier by locally reinforcing the fastener area or using a multitude of fasteners or making the whole panel stronger. Composite components are best joined by providing a join area such as an overlap or joggle with sufficient bond area to transfer loads. Fasteners transfer loads through the cross sectional area of the fastener to the composite structure which must absorb the load without exceeding bearing, breakout and shear constraints of the local area.

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