I’m looking for some opinions on what could have happened on a board I sold to someone who came back months later and said they had an issue with delamination. I asked him if he ever left it in a hot car and he said he never did and kept it in a board bag.
The construction is #1.5 lbs EPS sheet foam glued together with 3M 77 (spray contact cement for EPS foam), board is vented and has a color cloth inlay. Glassed strong with double 6oz on the deck and single 6oz bottom with a fin patch. Vented with an auto vent.
I have made many boards and a few SUPs using 3M 77 for gluing sheets of EPS together, never had an issue like what this guy came back with. Basically I thought at first there was a delamination on the bottom, there was a huge air bubble from the fins to almost half way up the board.
Once I cut it open I realized the sheets of foam had separated, you can see in the pics the extent of what happened, I should have grabbed a pic of the bubble but I forgot.
I have been racking my brain on what could have happened and my mind keeps coming back that he did leave it in a hot car, because the amount of air that expanded to push the sheets of foam apart had to be pretty high, so high that the auto vent couldn’t handle it in a short period of time.
I think if the foam sheets didn’t give away first, I think the glass would have been delaminated, air has to go somewhere. I gave the guys money back and I’m going to try and salvage it using some spray foam and clamp it back together.
Any one have thoughts on what could have happened? It’s a shame as this was a nice board, I surfed it for 2 years before selling it and never had an issue with it.
3M 77 melts EPS. 3M 78 does not.
I suspect the melted EPS seam between sheets prevented air from equalizing fast enough (if at all) from one sheet of foam to the other, that is, only one layer of foam was venting.
Which side of the board is the vent on?
With 2 layers/sheets of foam, you may need a vent for the top layer and a vent for the the bottom layer (2 vents).
No doubt in my mind the board was left in the hot sun.
Board bags can get pretty hot.
Just my $0.02.
Opps correction it was 3M 78 I used, my bad, always get them mixed up LOL.
Thanks for the thoughts, the vent is on the deck by the tail. I did think about the two sheets not having a path for the air to travel between them, so I always use a thin metal wire and “docked” the board at various places so the air could travel freely.
The spray glue is not good for EPS, even epoxy can be a problem. I have made a lot of boards gluing up 2 layers of EPS foam to get a thick enough blank. Several have delaminated between the sheets. I found that you need to rough up the surface quite a bit and you need good full coverage of glue on the whole surface. Boards that I had used a layer of epoxy resin, but didn’t sand the foam surface good separated. Boards that didn’t have complete coverage of glue, separated.
I try to avoid gluing up 2 full sheets to get the thickness because shaping through a scarf is a real problem. I prefer making rocker slices and I use foaming PU glue like Gorilla Glue and clamps. I run a bead of glue where I think I won’t have to shape to avoid problems. Clamping with PU glue make a solid bond. I also add a perimeter band to avoid shaping through the glue along the rail.
I think it might help to have a breather in the board if you want to make boards with 2 layers of EPS, but you still need to make sure the glue surface is clean and rough enough for the glue to bite. When the board delaminates between the foam, it is hard to fix. I have a board that really like sitting around waiting for a fix, but I don’t know how I can do it. I drilled holes into it once and used a syringe to push epoxy in. I thought it was fixed, but it delaminated again. In hindsight, I’m pretty sure that I didn’t rough it up enough and use enough glue when I first made it.
I also had the same delaminating issues when using 3M Super 78 to glue up multiple sheets of EPS. Mine was on a downwind carbon foilboard and the delamination occured on a hot day with the board in the sun. The board was vented. I’ve tried to fix the board by drilling multiples holes in the deck, syringes the epoxy in and vacuum bagging it. The repair failed anyway. So much money down the drain. YIHAA
I will make sure to never having to glue EPS sheets again. BUT, if I would do it, I would try that guy technique :
1 - Trace a rough outline on the sheet
2 - put a few drop of PU glue to tack the sheets together
3 - shape the board
4 - seperate the sheets by running a fishing braided line between them
5 - glueing full sheet with PU glue
6 - Vaccum the thing.
FrançoisSF, from first vid i look quickly, seems you speak about XPS (styrofoam=extruded foam) not EPS (beaded foam). Xps is known for delamination problems even if some use it with more success than disaster it’s sensible to delam. Good keying and pu glue is a way to reduce them but…
Eps, if there is a bit of glue, don’t delam, but beaded can separate somewhere under the glueded skin.
Sorry, bad spelling on my side. My problem was seperation of the sheets and not delamination. The laminate was still attached to the foam. The video is indeed XPS but my board was EPS.
What kind of glue are you using to glue up your EPS ?
Dans un autre ordre d’idée, je voulais prendre le temps de te remercier pour toutes les informations partagées sur le forum. Je suis Swaylocks depuis plusieurs années et tes conseils sont toujours pertinents.
Beasho has had some neat ‘stuff’ (online board building content) over the years, nice to see his name mentioned. I was more aware of it when I was making SUP’s and posting on another forum that he also frequented.
Ok François, i will ask in english for everyone even if it’s not my best, les français et les langues étrangères…LOL.
So for gluing Eps foam to Eps foam i use PU foaming glue, i spread it and scrap it thin with a stiff squegge on one foam part and water spray the other then put them under pressure. Pu glue with water foaming and go deep in eps so impossible to separate without destroy eps. Fluid is the glue easier it is to spread. Not funny to shape glue lines so use it at minimal.
Here it’s my windsurf blank made with light eps sheets glueded
That is a great explanation, particularly in your second language! Is it possible to stop the glue short of any areas that will be sanded? I guess keep the glue more to the centre of the blank and not quite spread out to near the surface?
Yes, but because of foaming at least reduce glue quantity where you have to shape it. Need to find a pu glue that foam stiff, nowadays thanks to normes most stay elastic and tough, not easy to shape.
