How to Glue EPS Foam Sheets Together, 3M Super 77 vs 3M 78 Spray Adhesive | Surfboard Building

This is my new method for gluing sheets of EPS or XPS foam together. Applicable to other applications if you need to glue these types of foams together (Styrofoam, etc...).
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#surfing #surfboard #eps

[@e13design]

You can place some small dowels in between the sheets while aligning. Then remove to land the sheets.

[@bob1505]

Did you hear me? I was yelling to Andrew, anybody that has done countertops knows to use dowels! It really does make it easy to align sheets with just one person.

[@66crayfish]

If you're worried about the glue seams on the blank, use your template to mark the outline of the board on both sheets & either mask up to/ spray but use a piece of cardboard as a shield, or don't spray glue on your cutting or shaping lines. The glue doesn't have to go all the way to the edge. Same with your profile if you are having a lot of rocker - only spray the glue up to your shaping line.

[@GMan38cal]

So, you actually let the spray dry before putting the pieces together? When I read the can, that's what I thought it meant, but wasn't sure. I'll be gluing the insulation to plywood, and probably spray both the insulation and plywood, what 3M calls 'two surface bonding'.

[@hegemony57]

Love this information. Thanks.

[@aristotle_4532]

This clamping method is not recommended for flexible materials. Uniform pressure can be applied using drywall boards with the eps lying on a large flat table.

[@jamesdixon2219]

Great video. Thanks. How light have you gone with this construction style EPS? I’m curious to know how far you can go before durability becomes an issue.

[@AndrewWorkshop]

Thanks! I probably wouldn't want to go less than 1.25-1.5 lbs/ cubic foot. I think you could get away with 1 lbs/cubic foot if you glassed it heavy but then the trade off is the cost of resin and weight of the fiberglass does add up. Having said that if you don't mind some pressure dings like a PU board I think you could get away with it but I haven't personally done that as I prefer to make my boards to last.

[@jamesdixon2219]

@@AndrewWorkshop thanks

[@chriscoralAloha]

Thank you.

[@AndrewWorkshop]

You're welcome!

[@MikeBaxterABC]

How can you compare 3M glue for use on Foam, without included 3M 74 Foam Glue???/

[@ifell3]

Have you done a seperation test with bending a vibration or are these all good to go?

[@ttonAb2]

Curious as well

[@jamesroscoe7555]

Properly applied, my understanding is the 78 adhesive is stronger than the foam. Once it is glassed, the skin will strengthen it substantially of course. I've been making blanks differently than Andrew (I glue XPS rocker slices). The one blank I glued up with 78 has worked well, much faster to glue up the blank than with pu glue (no clamping) and vastly easier to shape over the seams. It also maintains the flex of the raw foam. With pu glue, the glue line is stiffer than the foam. Depending on the geometry of the glue line that may be a good or bad thing (my glue lines are effectively stringers and I've made "stringerless" XPS boards this way).

[@AndrewWorkshop]

Thanks James!

[@AndrewWorkshop]

I have on a small pieces, I wasn't able to pull the sheets apart manually.

[@jamesroscoe7555]

@@AndrewWorkshop I had one joint at the nose of the 7-11 separate slightly while I was levelling the deck. But the foam was barely a half inch thick (or less) there and I probably didn't get a perfect spray of 78 in that spot. It was easy to fix (wicked in a little clear pu). For my process, spraying slices around 2.5" wide, there is a lot of overspray and the process is tricky to align and messy albeit faster than clamping up pu. For gluing whole sheets, I think it is the way to go. I would still use pu to glue in a wood stringer.

[@reidfreeman879]

Does that layer of writing on the insulation peel off? Or is just taken off as it’s shaped?

[@AndrewWorkshop]

I should have mentioned, that is a vapor barrier that is on some sheets. I peel it off if I need to glue sheets together or when I hot wire I don't need to remove it since it gets removed with the big chunk of foam. A hairdryer helps loosen the plastic and it peels off easily.