First board EPS delam :/

Okey so i fillcoated my first board bottom then deck and left it in the garage for two days. 

Just got my new bosch router and was gonna prepare for the fin box when saw two big bubbles and some smaller ones. 

1.7 EPS spackled 2 times and glassed 1x 6oz bottom and 2x 6oz deck.

Only thing that i can think of is that when i pulled the tape off the board I also removed some foam so i did a extra thin spackle along the the cutlap, let dry for 6!! hours and then sanded and did the top lam.

I also messed up the weight ratio when mixxing my epoxy for the bottom lam, the scale turned of in the middle of the process so i couldnt get it 100% 2 to 1 ratio.

Ive searched the board and it seems like the only way to solve this is to cut and remove the glas and patch in some new?



Maybe too much spackle/not enough lamination bonding to actual foam core?


“1.7 EPS spackled 2 times”



It might just be my eyes, but the stringer looks high and that actually looks more like a bubble with dry edges than an actual delam of fully cured fiberglass.  

Where are you geographically?  How hot did it get in the garage?  By any chance, was the delammed part of the board near a surface that got extra warm?  Fresh still-curing epoxy is more likely to have issues if heated in an uncontrolled environment. 

I had the exact same experience as you 20 years ago with my first epoxy shape.  Hadn’t even sanded the fill coat.  Without my realizing it, a buddy set it near a space heater after checking it out.  Humongous bubble on the deck.    Serenity now, serenity now, . . .

gdaddy: The stringer might be a tiny bit high but I tried to get it leveled with the foam, I think the angle of the picture makes it look that way more than it is.

newschoolblue: I live in Sweden. So today it’s been around 25-28C outside (77-82F?) Wierd thing is that it had completely dried yesterday when I checked it. And today 24H later they are there :frowning: The garage could get as hot as maybe 30-32C today.  Been the hottest day in two weeks today.

The bubbles are really filled with air/gas and the epoxy is stickie when i push on them.


What about using a syringe to fill them with new epoxy under pressure? Or better to cut the affected areas of entirely and add new patches of glass?


Thanks a lot for the help guys , all went so good until today. Had so much fun… :frowning:


I’d be a bit concerned that the epoxy is ‘stickie.’  It should have fully cured by now.  I’d also be concerned that by ‘testing’ it, you may have contaminated the surface with your fingers.

Anyway, I’d mix up some more epoxy and pay careful attention to the ratio.  Mix thoroughly and try to squeegee it through the lifted glass.  There are often pin air bubbles and dry spots that will allow it if you squeegee from various directions.  

If it doesn’t penetrate, try making a couple of small slits with a clean razor blade and work the epoxy in through the slits.  If you can, have one of those nifty curved tip syringes on hand to inject the epoxy in to the slits.  In any case, once the ‘bubble’ is filled, lay a sheet of plastic over the repair and weight it down with something flat.  

Hopefully the additional epoxy will set up hard and you can proceed as normal.  I would consider scuffing the surface of the glass with coarse clean sandpaper before applying the fill coat just to make sure you have a decent mechanical bond if the first batch has cured too much for a chemical bond.

I gotta say, that’s a weird looking ‘bubble.’

Got to warm.  You are also using way too much spackle…

epoxy sticky = bad mix. Probably you poured the mix out and started spreading it then scraped the container and dumped the last bit in the middle, therefore you have the problem of bubbles in the middle. If so, next time scrape the walls of the container into the center as you mix the epoxy, stir thoroughly, then when you get the last bit from the ocntainer, it will be mixed properly. “2:1” epoxies have some tolerance for mix ration, but usually they are truly 2:1 by volume not weight. Also if you mix by volume, no problems with tare or scale turning off etc. So try that next time.

I would  go ahead and get some brand new razor blades and use them to cut away the glass where it is not laminated onto foam. One layer of glass, not too hard. Or use other tools, if you like. Do remove the glass and scrape off all the sticky uncured epoxy, wipe the area down with a cloth soaked in 90% isopropanol or ethanol or xylene and let dry. Sand a 30-40mm margin around the area you cut out and reglass, taking care to mix epoxy thoroughly (mix for a minute, let sit for a minute, mix again, hold  up to light and see that it is mixed, scrape along the sides of the cup and fold the mix into the center, look at it carefully before applying.). Make sure the ratio is right too. And always glass epoxy over eps foam (or other porous  material) while temperatures are falling (normally better shape in morning, glass at night). Glassing while temperatures climb makes any bubbles expand, and makes air come out of eps blanks.

First epoxy board, do these steps, learn the process, don’t worry about the cosmetics too much.

johnmellor: The board is totally dry on the surface but the bubbles were filled with stickie epoxy . I always use disposable gloves when touching the board to not contaminate it.

McDing: What could be the cause of the board getting too hot? by just laying around after the fillcoat in a too hot garage? or the epoxy getting too hot? Just trying to learn from my mistake.


I decided to remove the bubbles instead of injecting more epoxy. I used a new razor blade and cut out the areas that were loose and the foam was coated with stickie epoxy :confused: The fields are now in need of some kind of spackle again since i also pulled some beads out with the fibreglass. 

My plan is to let it “dry” over night and see how it looks tomorrow. Hopefully the sticky surface is dry enough that I can sand it down a bit.


I am afraid that new bubbles will pop up once i cover these areas with a new layer of glass/coat

Thanks again for the help.

Will try to use less spackle next time. I tried to only fill the small holes with spackle and then sand the rest off, i scraped fairly hard but used approximately 600-700 grams of spackle that i mixed with distilled water. Spackled / sanded/ spackled /sanded …The board is 9"6 1/2.  

bwd Missed your post while writing my own. I just got a delivery today with mixing cups that I will use next time! I mixed a  big bucket with around 1200grams of epoxy. Poured half of that into smaller ones that I also added some different white/yellow pigments too. I then poured them along the board one by one , let it soak for a while then squeegeed it off. Poured the half litre of clear epoxy and lapped the board. 

were afraid of air bubbles and might ended up with a too unmixed epoxy ://

Although I am kinda disappointed right now I was sure to be knee deep in trouble way earlier than this , I am glad i got this far hehe :slight_smile:

You’re on the right track now. I usually only mix 200-300g epoxy at a time… With kg amounts you are lucky you did anything beyond making a smoking mess!
The uncured goo may harden but it isn’t like polyester that just needs to be catalyzed, to work; it has to be mixed with hardener at approximately the right ratio. Usually best to scrape it off when not right…

I’m a beginner on this laminating lark, but the thing that surprised me me how much my mentor moved the epoxy over the board to work it into the cloth and substrate - beyond when it looks as through the cloth is wetted out. Then he cuts the resin to bring it to the laps (holds the squeegee vertical and drags) and says, “Listen to the pop pop pop of air bubbles bursting.” I’m getting better under his tutelage but still can’t hear the popping.

When foam bead pop off easily at shaping, it’s a poor fusion eps, it’s possible for all kind of density but more with lighter one, it’s not an acceptable foam for surfboards because it’ll have delam problems and/or it’ll easily buckling. Make sandwich skin on this kind of foam.

Good inputs from everyone.  The 2 primary issues I see are the mixing ratio and possibly heavy spackle that really wasn’t dry.  The measuring cups will fix the mixing issue, but the spackle must go on extremely light as McDing says. Just enough to fill the voids - not a coating or fix for shaping errors.  Some of the water in the spackle will evaporate into the eps, which can condense and cause problems later when laminated, so the blank must be dried thoroughly and 6 hours isn’t enough even in So. Calif.   Dry it for a full 24+ hours, hot box if it’s too cold. If you really think that temperature is an issue, leave a breather hole when laminating.  Drill a hole 1/2 thickness of the blank to fit a section of drinking straw (tightly) at the leash plug or finbox, then laminate over/around the straw.  This is the usual venting procedure if doing high temp curing. 

RR is 2:1 by VOLUME but 100:45 by WEIGHT !!!

I know epoxy cures when it is a bit off, but the quality of the cured epoxy is very sensitive to the ratio.

Always make sure to write down the weight of the empty cup before mixing! I’ve had the scale crap out multiple times, knowing the weight of the empty cup has saved me several times.

I mix with 1 gram resolution and never make batches < 75g

Been reading a lot to prepare for every single step. But i guess this is the fun part of creating and building stuff. There is so much to learn and I am very thankful for everyones input and ideas.


*Less spackle

*Epoxy ratios 2:1 not by weight

Seems to be the two main errors.

Will maybe try the drilled venting hole method next time.

I hope the EPS quality is ok because I have material for 3 more longboards and would be sad to throw them away. Was a struggle to find someone here in Sweden that wanted to sell me any at all. 

The foam beads that followed with the cutlap tape was because I pulled the tape off with a bad angle. :confused:


The foam is no longer sticky where I removed the bubbles yesterday. Will measure the temperature in the garage today and see how hot it gets.

About the spackle. What do you use as spackle?

I advice on using thickened epoxy (thickened with mircospheres).

This leads to a much better bond than throwing in another product with different properties.

The major advantage is that you can glass over it when it is not fully cured yet, which leads to an even stronger bond.

BTW: The weight ratio should be mentioned on the bottle label, so another tip is to always read the label! As some epoxies have different ratios.

I used “One strike filler” mixed with distilled water.

ok, I could try to use epoxy + mircospheres on the areas where I removed the bubbles to even out the foam and then laminate a new layer of fibreglass. 

Measured the temperature in the garage today at 80.6 degrees, it’s not usually this hot around here but still curious if that is too hot? 

The epoxy i use only say 2:1 Ratio on the label.

No it’s not hot. I have guys that let my EPS boards in close car in sun every day here in south France with no problems. I must say with no more problems because i have before and i take care know. Poor fusion foam have lot of space between beads, so they are more sensible to temperature because gas between bead is free off move. For same reason they take more water when dinged.

Doesn’t it say if it is by volume or weight?

If not, that’s some serious crap epoxy.