Fiberglassing overhead - How?

Discussion in 'Fiberglass and Composite Boat Building' started by jdory, Jun 11, 2018.

  1. jdory
    Joined: Aug 2015
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    jdory Junior Member

    I'm about to fiberglass a pvc tube onto the structure as pictured below for net attachment and wondering how to do it. The layup will be 3 layers of biaxial glass, starting with 12" wide and getting narrower. Using epoxy. I've now got the pipe coved in all the way.

    I've searched on the internet and see some people recommending 3m 77 adhesive spray to tack up the dry fabric, but I'm afraid I'll float it off when wetting out the fabric with either a brush and/or foam roller. Plus the subsequent 2 layers might want to fall off as I apply them. Just haven't had enough experience to know either way.

    I've also read about letting the initial coat of epoxy (on the structure) get tacky, then putting up the cloth. I did try that on the sides as an experiment, but it seemed to float off when wetting out the glass like I fear with 3M adhesive.

    I'm thinking I could vacuum bag it but getting it in place (only myself working here) while getting the bag going seems very difficult. I'm trying to picture using the ropes (I used to help hold pipe in place while I tacked it on with thickened epoxy) as perhaps temporary clamps - lifting up the whole wetted out assembly and bag on some doorskin plywood (12' wide structure) into place, then getting the bag stuck on and going. But maybe there's a more simple way?

    I've also thought I probably should cut the 12' pieces of fabric into 2 or more pieces to make it less troublesome. I could overlap the subsequent layers over cuts to help with overall strength.

    Hoping someone can show me how they did/would do it. Thanks for looking! Jim

    Oh, and it seems easiest if I just vacuum bag and infuse it, but I've no experience in that and getting infusing epoxy (low viscosity) here would take awhile. Mostly, not having the experience makes me hesitate to try that.

    IMG_20180606_183155.jpg
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Fibreglassing overhead I have found less of a drama than might have been anticipated, but that was always using polyester, and mainly mat, but sometimes unidirectional glass. Make sure whatever resin you are using, is suitable for laminating when working overhead, If you have doubts about the materials you already have at hand, do a test under an old table or similar, to see what problems ensue, or if you have yet to obtain the resin, interrogate the supplier as to the suitability of it, for your application, I have used epoxy resins that were relatively thin and runny, and don't think it would have worked overhead too well, but I expect a suitable thickening agent might have corrected that.
     
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  3. jdory
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    jdory Junior Member

    Thanks for the reply! I may be overthinking it. I could try a little thickened epoxy, let it get tacky. Working at about 60 degrees F. so not too runny.
     
  4. ondarvr
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    ondarvr Senior Member

    Thicken it to almost like a putty, then put one layer on, it should stay in place well, three layers shouldn't be a problem.
     
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  5. jdory
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    jdory Junior Member

    Thanks! So I have colloidal silica that should work for that - my only concern there is weakening the peel resistance. But it shouldn't, I think.
     
  6. jorgepease
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    jorgepease Senior Member

    That would be so easy to vac bag, no need to infuse. It would eliminate any chance of sag. If you have the pump why not.
     
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  7. ondarvr
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    ondarvr Senior Member

    It's not going to be an issue.
     
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  8. redreuben
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    redreuben redreuben

    While I’m more familiar with poly I would wet out the glass on a board, roll it up on a piece of tube and then unroll it on the job consolidating as you go. Don’t oversaturate more weight will help it slide/fall.
    Use peel ply if you have it.
     
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  9. jdory
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    jdory Junior Member

    Thanks for reply. I may vacuum bag, but the issue is holding it there until I get the bag set up.
     
  10. redreuben
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    redreuben redreuben

    The trick to getting it to hold up is resin quantity you need enough to wet the fibre and create enough “Sticxion” but not so much that it slides of in a river of resin.
     
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  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Conduct that experiment I spoke of, and proceed with the "real" work when you are satisfied it works on the test patch.
     
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  12. rwatson
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    rwatson Senior Member

    Gee- so many complicated solutions for an easy technique.

    For overhead work, just use Peel Ply. You dont want to thicken the epoxy or it may not wet out the fabric properly.

    It holds the right amount of resin firmly against the hull, and doesnt drip.
     
  13. jdory
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    jdory Junior Member

    Yep - got and always use peel ply. Getting the glass to hang there while applying the peel ply is my concern. I suppose I could wet out the 3 layers of glass on a table (board), apply the peel ply there, roll it up and then unroll onto the structure, working it while unrolling. Only two hands. I think if it does start to peel off on an end I could temporarily clamp it using my ropes or somesuch, if masking tape doesn't work. But working all that with epoxy on gloves, and a roll of 'yet-to-be-stuck-on glass' in one hand... Maybe I should call in some help on this one. (12' length of biax tapes)
     
  14. rwatson
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    rwatson Senior Member

    how heavy is that glass ? I certainly wouldn't try to do all three layers at once. Just apply each layer before the previous one hardens.

    If you wet it out with a roller, I would expect it to just stick there, just from air pressure if you don't overwet it. In fact, you can go a bit light on the final the Epoxy layer application as the peel ply will spread out and fill any dryish areas when you roll it..

    You may need to use tape on the edges, or worst case, some patches of peel ply at difficult curves. If you are doing the dry - wet technique, some thin plywood and large headed pins might work for a temporary holding technique on the dry sections.

    You don't want to try and put one big sheet of peel Ply on at once, Just cut it up to 1 x 1 metre squares, and apply them strategically.

    The little bit of "ridging you will get is not a problem.

    Edit. Oh, one more thing that might help. make up something to hold the Fibreglass on the rolls like a toilet roll holder, so you can reel it off the roll as you wet it out.
     
    Last edited: Jun 12, 2018

  15. ondarvr
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    ondarvr Senior Member

    Using the thickened epoxy as a bedding for the glass works well, wetting out the glass isn't a problem once the glass is held in place.
     
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