EPS glue up - Latex Paint FAIL

I had saw some indication that latex paint would work to bond EPS. After 48 hours it was only dried on the edges (and holding strongly). However the inside was still completely wet paint.

Any better suggestions? I can try Epoxy, Gorilla glue or Titebond

All that you named could work. If it’s Titebon, it should be waterproof (Titebon III). In my case, I’ve used 2 things: contact adhesive specially made for EPS, and PU foam in liquid formula (A+B). Search the archives. Good luck.)

I decided to try neither of those things. I’m attempting to use gorilla glue spray adhesive even though it’s not actually compatible with styrofoam. It seemed to only melt the foam slightly. We’ll see what happens.

See something like this before you buy something

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For polystyrene foams (EPS & XPS) the spray adhesive you want is 3M 78.

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I haven’t found a spray adhesive for EPS or XPS that works well. Foaming Polyurethane glue like Gorilla Glue or Elmer’s are the best for a solid bond.
I’ve tried at least 5 spray glues, and 3 said they were for foam. They didn’t melt the foam like some will, but they didn’t have a solid bond. I could pull it apart after it was cured. Some spray glues will melt the foam as soon as it touches it.
I tried various types of white glue like Roo Glue, the Titebond, even the kids Elmer’s glue. I have not tried contact cement.
I would try to stay away from epoxy because the seam will be very hard compared the the foam. Foaming poly glue is harder than the foam, so you have to plan out the glue joints and try to keep from having to sand through them. It tends to tear the foam or create bumps and dips.

You are right. It seems that under pressure the PU foam increases in density and becomes hard to sand. I made my first board joining eps sheets glued horizontaly wity this and it was a pain. Now I am trying with contact adhesive with the vertical method that sharkcountry showed in one of the last threads of the old forum. The only problem aré the rails. I am newby so I dont know if I can do some decent perimetral rails…

3M 78 Polystyrene foam spray adhesive has to cure for 2-3 days to get a strong bond.
But it is more difficult to sand when it is cured.

Overall, not thrilled with having to do glue-ups for my boards. I am shaping wakesurf boards and I think that the thicknesses and rocker shapes are putting my deck too close to the glue up line. To the point that I sanded through the glue up line while foiling my deck and ended up with a really awkward deck situation due to that.

I’m going to have to play with it a bit to see if I can figure it out, but I may just suck it up and start ordering blanks from Greenlight.

Unfortunately I’m nowhere near the coast or a surf town where I can easily grab blanks.

Or do like Sharkcountry. Bend your rocker into the horizontal sheets you bond together. That’s where he has problems with spray adhesives not holding.
I don’t do that because I don’t need much, if any, rocker in bodyboards and knee-board/bodyboard hybrids — especially with no tail rocker required for my tail channel.
But several years ago I noticed that the foam could not be pulled apart if I let the 3M 78 cure for 48-72 hours. So, I suspect that if you want to bend rocker into a 2-sheet blank, you need to keep in in the rocker table/rocker jig for 2-3 days so the 3M 78 can cure.

Might be worth a try … I just question if the value and time saved is worth it. Some other things I’ve been considering:

I cannot find any EPS sheets in anything higher than 1pcf. And even the 1pcf stuff I bought weighed out to only .88pcf …

2pcf blanks from Greenlight would be a lot easier to shape since the denser foam will sand better and have less tear out.

So am I just killing myself using inferior products for the sake of saving $100? I’m not selling boards yet, but if/when I get to the point where I actually will build some commissioned boards for friends, then I think it might be best to just get some blanks shipped.

I dont know where you live, but where I live, a third world country, there are eps industries that makes fish and medical boxes, eps locks and so on, that make on demand blocks with the Kg/m3 that you nerd, too. Search on internet, call them.

I started making compsands with full blanks, but my brother figured out a way to use the EPS sheets at Home Depot and Lowes and a rocker bed to get the rockers we wanted. The foam was softer than standard EPS blanks, but a fraction of the cost. Our first 10 or so boards had balsa wood veneer wrapped around the foam and that gave it a lot more strength. Sometime after that I found 3 denser 4’ x 8’ x 6" thick slabs of EPS on craigslist and decided that it would be more economical to cut rocker slices than to carve out a single board. I made a bunch with 4 sections and no wood covering, just glass.
That taught me how to use glued up pieces of foam and make blanks.

I do not recommend this method of making the blank because it is time consuming and can often lead to other problems. Shaping is a big one. Glue lines will drive you crazy if you are sanding through them. Some softer glues don’t sand so you will need to use a razor and carefully cut them. Hard glues often lead to unevenness, or tear out the beads. That’s when you learn how to spackle boards.
I still glue up foam, both EPS and XPS, because I have a lot, and we keep getting it with medications.
I only make boards this way for myself, it’s a great conversation piece when I’m out. I don’t hide the glue lines, so people can tell that the board was made from many pieces of foam glued together.

I officially just threw in the towel with DIY blanks. Not worth the hassle. I’ll either drive to the beach or order from Greenlight.

My .88pcf or 1pcf whatever board just got completely destroyed. Left it in the sun to finish curing some epoxy and it off-gassed something fierce and delaminated. Crushing blow on surfboard #2.

Leaving low density foam in the sun causes the air between the EPS beads to expand.
Think empty plastic milk bottle taken from 68 F room temp, then top cap sealed. Place it in the hot sun outside. Bottle blows up like a balloon.
If you use low density EPS you need to add a vent.

So I intended to add a vent shortly after this step. I knew this could happen but damn we’re talking A LOT of air in a pretty short amount of time. And these boards are meant to be wakesurf boards that might sit in the sun on the boat quite a bit so I can’t really risk that.

Funny but not funny. Been there done that many times. It’s important to understand the differences of each foam and how to manage them. There is a very good reason why PU blanks are the best for surfboards, but making my blanks from left over foam only costs me my time, glue, and some tape.
I had one EPS compsand board that I put in the sun to post cure and in 15 minutes it was a balloon. I actually surfed it like that a few times. The cool water would pull the board back down, but I knew that it wouldn’t be good to leave it like that so I cut into it to fix it and found that the heat made the foam separate and the wood/glass was solidly attached to the foam.
Several of my XPS boards developed large delams during an extremely hot year sitting in my outside covered board rack. I made the mistake of using old aluminum siding when I build the rack/shed. My XPS boards will delam if left in direct sunlight, but if I leave them in the water, they are OK.
As far as vents, I only have vents in my hollow boards. None of my EPS or XPS boards have a vent, but vents are good, just remember to use them correctly. I once showed a guy the hollow board I made and I thought I had the vents opened, but when I showed him the vents and opened it more they let out a small sound and I knew that the weren’t opened enough when I stored the board. Gotta make sure you open and close them properly.

Doing that you are avoiding that a bunch of eps it goes to the oceans, fishes, and so on… even humans. Eps never desapears in nature, and is one of the less recycled polimer in the world, 1 % if I’m not wrong.

I just glued up enough pieces of XPS to make a 6-6 x 21 blank. I used Gorilla glue. This board has 12" long x 1.5" wide pieces running nose to tail. I stagger the pieces to make sure there are no weak spots. Pieces were 10" or 12" square by 1.5" thick.
I think it’s safe to say that we have poisoned Earth with plastic debris. Mostly from plastic bottles and containers, but I’m sure EPS and XPS are contributing too.

That’s fir sure. Eps it goes dividing until microparticles that ends on the oceans. This year here in Chile there were hard rains, the rivers overflowed, and what was one of the more abundant things that the wather carried? Eps. One of the reasons why I am trying to do the same like you, sharkcountry. And with the rest of eps I found an “eco-wood” recipe that can work to make dime find. Maybe. Let’s see…