Looking for "Soft" Adhesive to use with Foam...

Discussion in 'Boat Design' started by BobBill, Mar 21, 2021.

  1. BobBill
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    BobBill Senior Member

    I understand some here have made foam amas and hulls using epoxy, and dealt with foam sanding and the hard epoxy to fair...I have been advised to use Gorilla Glue...waterproof, soft and so on...

    Any advice is welcome...plan to glue Blue or Pink sheets (BigBox) of 2" foam to form hull, using hot wire...and hot wire ideas welcome too.
     
  2. fallguy
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    fallguy Senior Member

    Just use the foam glues.

    PL300 foamboard adhesive. Sold in caulk tubes.

    gorilla glue is not really affordable

    When you cut the tubes, cut a 1/2" hole in the nozzle and use a trowel to trowel the glue a bit thinner.

    You are sheathing it all in glass, so you don't need perfection, but the glue provides some shear web if you ise enough. If you are using a ply web, then the glues are only holding it together until you do the glasswork, ftmp

    When I made small amas, I remember putting a bead like every four inches and knocking it down flat with a trowel. I did not go for full coverage of the foam. This also makes shaping easier as you are not necessarily always in glue. But foamboard glue was pretty pliable after curing iirc.
     
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  3. BlueBell
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    BlueBell "Whatever..."

    BobBill,

    I have found wooden skewers work really well,
    when placed at the correct angle,
    to really help keep foam pieces in place while the glue sets.
    Remove, or leave in, as your build allows.

    BB
     
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  4. BobBill
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    BobBill Senior Member

    First. Thanks for help...I plan to use light Okuma as the shear web, or the trimmed outer edge of the Hobiecat 16 hull.
    Its shap can also hold the pylons and serve as guide to wire trim shape...deck will be light Okuma...using H-16 asymmetric shape also...The foam will be pink or blue...2", in layers, then wire-faired and glassed...ala Dierking; though I believe he used epoxy. Then will paint to match.
     
  5. fallguy
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    fallguy Senior Member

    There is no reason to use epoxy to bond the foams together. You could epoxy the foams to the plywood, but a thickened epoxy is really far more difficult and expensive than needed for foam to foam bonds.

    On Page 62 of Gary's book, he mentions polyurethane glue. Foam glues work fine. Probably not for wood to foam.

    My amas are fairly small, all foam, no web. Glued up with foam glue.

    My pylons were set with wood flour thickened epoxy. Mine are made with pvc and have worked fine for the canoe. But my amas are only like ?4' long

    ps...Dierking says to test the bonds and I did..the foam glues pull the side with lower surface area with foam because of the low shear strength of the foam; this is a technical pass of the quality; epoxy would be no different...in order to epoxy bond the foams well; use a 1/16 trowel and a lot of epoxy; the failure mode of the joint is the same, but here does not matter because you are fully sheathing the ama and so it can't pull apart; it does take a few days for the glue to cure up; glue them on a Friday and take the weekend off..
     
    Last edited: Mar 24, 2021
  6. BobBill
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    BobBill Senior Member

    I dig, thanks for ideas.

    Main reason am looking for other than epoxy is the soft foam vs hard cure of epoxy. Gary did build a lovely hull of blue foam, but I would suggest the fairing process was a bit dusty.

    I moved to a hotwire kind of fairing and was just looking for means of dustless or close to dustless fairing before I glass the hull, is all. Someone suggested Gorilla, so I asked...

    Evwn bought a slew of 18650 cells and some AF transformers to heat wire...but might just use simple thermostat and 110 from wall, like with solder iron for glass.
     

  7. fallguy
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    fallguy Senior Member

    Dust is good. Sorry to tell you, but using 36 grit floor paper increases surface area and improves on the poor shear ratings of xps
     
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