Questions about epoxy & FG on house boat roof

Discussion in 'Fiberglass and Composite Boat Building' started by mudflap, Jun 17, 2020.

  1. PROPGUNONE
    Joined: Jun 2018
    Posts: 24
    Likes: 10, Points: 3
    Location: Sharpsburg, GA

    PROPGUNONE Junior Member

    Especially if there’s an underside to glass.

    I rarely measure a specific amount of epoxy. With the 2:1 RAKA I use cheap, clear plastic cups. Think dollar store, about 8oz sizes. I pour an arbitrary amount of water in one cup and mark the level of it on the outside of the cup with a sharpie. Then I pour that water into a second cup. Refill the first cup to the line you drew, dump the additional water into the second cup, and mark your new line. The first cup you used is your hardener, the second is your resin. 2:1 ratio every time. I just keep making batches until I get to where I need. The exception is large laminations, where I’ll use measured cups, working with about 12oz at a time. I just go until I’m done.

    Roller will start to degrade before anything else does due to the epoxy getting tacky and the friction increasing... one of the reasons I prefer a squeegee. The cups shouldn’t have goo in them long enough to really set up. If you’re measuring with graduated containers, just make one always for hardener, one always resin and then combine in a third, disposable cup.

    Sanding depends on how bad your underlayer is. Wet on wet is always best. If I were doing two or more layers I would probably pre-cut every layer of glass and work one section at a time, laminating all three layers before moving on and trying to do it fast enough to maintain wetness for the next layer to stick to. Peel ply is useful for this, though Ive never used it. There’s about 100 variables involved, but basically if the glass doesn’t lay flat you need to do some grinding/sanding. If the epoxy is hard and the glass is flat you need to do some washing. If you use peel ply you accomplish both these things.

    150grit is my go-to for just about all boat work. The exception would be mold making.

    With a roller you might need to use a laminating roller, but Ive only ever used one to roll out CSM. With fabrics I just squeegee them down until I get good wet-out. You can feel the cloth with a squeegee.


    If I were new to it I’d do it this way:

    Buy yourself a bunch of 36” wide or so 10oz glass. Cut it into 1-yard sections, with some slightly larger. Lay them down on the roof with about a 2” overlap. I number each piece with a sharpie, then I roll it up and set it aside. Now you have your pattern.

    Wet out your roof with an as-thin-as-possible layer of epoxy. Let cure. Plywood shouldn’t have any areas that soak up more resin than others, but if you do, keep working until you get an even, thin coating.

    Sand any high spots down, rinse or wipe with solvent.

    Lay down your first section of glass. I make epoxy and just dump it right on top. Then I work my squeegee over it, not worrying about perfection yet, until its wet. Drop the next layer on top of it, squeegee well to get the resin from below worked into it, then add any extra epoxy you need. You should be able to wet out a one-yard area with two 10z pieces of glass in relatively quick time. If you have extra resin, just lay your next section of glass down and pour it on, repeating the process, overlapping glass sheets by a few inches.

    You’ll quickly develop a feel for how much goo you need and what pace you’ll work at.
     
    bajansailor likes this.
  2. mudflap
    Joined: Jun 2020
    Posts: 10
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    Location: texas

    mudflap Junior Member

    > it might be easier to fibreglass the sheets at ground level, fit them on the roof, and then just glass the joints?

    You are sure right. Will try to do that as much as possible next time. As it is, plywood has already been glued (PL adhesive) to frame. Doh!

    Here's a 'nuther dumb question:

    After mixing in cup, can I pour epoxy in disposable paper bowl to increase surface area when applying with brush? It does not appear that bowls have was coating.
     
  3. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Paper bowls will usually be fine.

    But don't get to upset if Mr Murphy hands you the odd one that isn't.
     
  4. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Using a brush is painfully slow, on a flat surface I pour the resin on the surface and use a squeegee to move it around and remove the air.

    No need for a second container with a different shape.
     
  5. mudflap
    Joined: Jun 2020
    Posts: 10
    Likes: 0, Points: 1
    Location: texas

    mudflap Junior Member

    Thanks for all the help. Work is in progress!

    So I bought Raka 127 resin and 350 "non-blush" hardener.

    Question: Is "non-blush" truly free of blush? I'm not sure I'd recognize blush if it hit me in the head, so I'm hoping I can ignore this potential problem since I upgraded on the hardener?

    Goal is to re-coat before epoxy hardens whenever possible.

    If allowed to cure, plan is to do a light sanding, followed by a thorough vacuuming.
     
  6. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    "blush" looks a lot like a hard water deposit on a shower tile. It is easily removed with water and a scrub pad. Many do an insurance scrub before sanding.
     
  7. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I just did a similar job.

    some advice

    Use 50" wide cloth, full overlap in the middle at 48".

    put the cloth on a tube and roll it back towards you so long as the roof supports you

    wet about 18" at a time and keep working back to yourself; do one side at a time

    I used db1700. You can use lighter, but for any db you must wet the substrate or wetout is tough.

    Light woven glass you can topside wetout, but still roll off a tube. Light wovens can get drysucked by plywood; so you might want to precoat..

    Most manufacturers give you advice on no sand recoats. Gonna be hard to do anything bit weave fill on recoats. Assuming you are using woven cuz you want to sand biax before any weave fill to knock off the stitching a bit.
     
  8. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    And don't do this in direct sunlight.
     
    fallguy likes this.

  9. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    yes! You'll exo fast in hot sun..

    good point
     
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