sandcomp experts

did anyone experience soft spots (#1 Eps all loose) but no delam?

glas 3oz. inside/ 2x3 outside with 3mm H60. my weight is 75kg (150) quite less than berts 200 with 2oz glas.

i have 2 boards with it and cutted one b/c i was sure it would be a delam, but pulling the sandwich off i ripped the Eps off as well. the beads were sticking well to the glas but the EPS under it is all soft and crashed.

sorry i’ve got no camera so no fotos.

i’m now using H80 and balsa but a little worried.


Yep, thats what i’d expect to see.

The epoxy rarely delams at the point of bonding with the foam.

The weakest link in the chain is the EPS bond with itself, so the foam gets torn apart and forms a type of delam like that.

Even the bond with the wood can delam, thats not overly strong either, but unlikely.

The cure I use is to reinforce the areas that will be compressed often while under normal use - so under your feet, and possible where you hands go for duckdiving and pop-ups.

Do this by adding extra glass patches under the skin where needed.

This stops these areas compressing too much, which can result in failure of the foam.

EPS is very good in that it springs back readily, but there is only so much it can handle.

Hope that helps?


thanks Kit, what glas schedule would you rec. for those areas? 2x3 inside 3x3 outside? or swich to 4oz./2x4 glas on top and 3oz for bottom only?


i wonder how berts thread -board is holding up and where is he using foaming epoxy?

Sorry man, I’m not well versed in the foam skins, all of mine are Paulownia.

I go with 3 oz inside and out usually, with 3oz patches underneath. Sometimes more, but not often less, I find they feel good like this, and are sooo light anyway, it’s not worth chasing the last few grams and giving away that basic strength.

But Paulownia is heavier than the heaviest balsa (just).

Pauls (Silly) done heaps with foam skins, he’d be the man to advise on those


EDIT: forgot to say, thats for 2mm ish thick Paulownia skins

thanks again, maybe he’ll read it and give some tips.


i was just surprised about it.

i uzzi

could be bad bonding of the beads

i cat say unless i see pics

and even then im not sure

h80 is a lot more flexible longitudinally then balsa

it doesnt have the compressive strength of wood either

ive done that schedule you speak and my board turned out overly flexible and the deck skin was showing signs of compression damage after a short time.

i used more glass on the deck and rail and it has improved thing greatly

however its just a quick fix and not ideal

now i use balsa on the deck on all boards except my personals(test boards)

in the future

i plan to try 5mm airex at a slightly higher density if i use pvc skins on the deck

i think the 3 mm stuff is fine on the bottom

and then theres the springer???

hi paul, kit’s answer "…The weakest link in the chain is the EPS bond with itself, so the foam gets torn apart and forms a type of delam like that. " sounds about right. i made some tests and even my 3mm balsa is very flexy under the feet and will need add. glass.

i cutted both spots sparkeled the area with q-cell allready and have no camera at the moment.

it hurts b/c of the weight but i def. have to change the glas schedule or use higher dens foam, the tail area is to thin to stiffen it up with concaves, but the doubble concave on speedneedles boards make now more sense to me.

i’m still confused about it, like i said bert gave his weight with 200ibs, glass 2oz with patches.

springer LOL…yeah i planned to cut 15mm of the rails change to balsa and put 1 add. layer glass over the hole deck.

with the claims i made about sandwich stability i guess i’ll leave the house for the next month only @ late night. LOL


Bert uses balsa which helps, but I think he also orders the EPS to his specs. Building foam EPS quality is not surfboard foam EPS quality. Also the concave deck bert uses helps against denting as it spreads the load very differently. Cut a plastic bottle in half a see what force you need to dent it from the inside vs. the outside.

hi haavard, agree the concave helps. if i look at the damadge speedneedles doubble concave might even be better as you press with your feet outside the middle axis, but the worst part is under the rear foot where the deck is allmost parallel the front has some pressure dents. i might change this as well. as for the balsa it is def. stiffer, but if i press with my hand it might still flex to much.

as for the eps i’ll talk to them, if they can do something.

thanks for the info


hey Haarvard

i think building quality to be pretty good foam for building surfboards

The other option is to inlay higher density EPS as a deck patch.

Cut your own sheet of 2# EPS, half an inch thick should do.

Once you’ve shaped the blank, run over it with a router set to 1/2 inch depth.

Inlay the foam, glue it in with gorilla glue.

True up the shape if necessary.

Thats the lightweight option, but the extra glass patches are an easier fix.

Haarvard, thats a good analogy, I like that one, it makes sense!


h 60 is too light, its not spreading the load over a great enough core area …

revisit your skins …



thanks, bert i changed allready to 3mm H80 and 3mm Balsa but even this feels kind of flexy when pressed. it seems that balsa has the best mech. properties so i think to change as follow 3+3patch inside/ 2x3patch outside on top and from 3mm balsa on bottom to 2mm 2x3oz… i would use the remaining 3mm h80 for bottom only.

this would also make me 1 more layer to protect the edges.

what would be your rec.?

only shortboards up to 6"8


is the the vacuum thread board still alive?


i had to try the foto posting first. kind of big.

the modified board is the white one on the left. soft spots cutted out, filled with qcell, h80 bagged, patched. then i cutted the pvc rails and installed wood and this thing changed from easy forgiving to a super hot racer.

thanks to all for your help

not a bad quiver for my 6month shaping expirience jeje


Nice skin jobs!