I have done a test piece with some scrap EPS foam. I glassed a small patch on the foam with two pieces of 6oz glass, one coat of lamenating resin and one coat of sanding resin. I can compress the foam under the glass easily with my
finger and I am concerned about the strength of my finished board. Am I missing something about the process or are surfboards supposed to compress like that. Any comments would be helpful.
Supposed to be like that.
All epoxy styro boards are held together with the help of it’s other proponents, so one such structure, by itself, is weaker than the sum of it’s integrated parts.
Without support from 360 degrees, your patch is basically just a patch floating in space, unable to support itself.
Add the rest of the structure, and that includes more than one layer of 6oz and some hotcoat (inadaquate amount of glass for EPS blanks), then the whole mono structure gets it’s strength.
Thanks LeeDD that makes sense. You have lifted my spirits. I am
looking forward to glassing the whole board and I am reading everything
I can so I don’t have to many suprises.
What weight is the EPS, it makes a difference? I saw the innards of a broken Board Worst and it was most likely only 1/2 pound density. You can only get back from a glass job, the strength of the material under it, all the glass in the world won’t make up for marshmallow foam
How well does the EPS you’ve got hold up against compression without glass? The EPS I’m using now I can only compress about 1/4" with my tumb. Depends on the sice of the patch and epoxy too, I’ve had epoxy go off quite soft for some reason where I could compress it a little but the board has held up nicely. I’ve also done test patches that was soft to begin with, but cured to regular stiffness in a few days.
If the EPS is real soft I suggest you use atleast 3 layers of cloth on the deck(or atleast 2 plus patch).
regards,
Håvard
The EPS I use is about 1.5#density. I hot wire the blanks out of a giant block, use 2x6 oz top and bottom. The foam seems soft compared to polyurethane foam. But haven’t broken any yet with hard use. All of them have deck dents but I’m just making them for myself and friends and about the same I’ve gotten on polyurethane/polyester boards. Maybe a 3rd layer of glass on the deck would eliminate this, but I’d rather have them that much lighter. The only ding I’ve gotten is in a paddleboard I dropped on the rocks. I’ll never use polyurethane blanks or polyester resin again. I really like the floatiness of the foam and the durability of the epoxy. I went through a lot of trial and error before someone told me about Swaylocks. Greg Loehr and more recently Bert Burger have put out so much really great info on dealing with the materials. Go for it and have fun.
Jon
Cutting the outline through 2# EPS is tough. The consistant density is much harder to saw than Clark’s “crust then dust” foam. 2# EPS does compress a little but also decompresses to original shape. A shaped blank is much more flexible than Clark blanks. Picking them up is like picking up a bird: sooooo light.
I’ve used 1# EPS on 2 boards now. The first one got 3x6 oz S cloth on the deck. It definitely has a strange feel under my back foot - a little ‘give’ like a softtop or something. But everything seems to spring back. The only visible changes are dents from knee paddling.
The second one is waiting for hotcoat. I laminated a couple days ago and glassed on a homemade fin last night. I used 2x10 oz Volan plus a deck patch. Its stiffer already, and is still only about as heavy as a similarly sized poly/poly board.
So far, I’ve been using Tap Plastics epoxy with the ‘medium’ hardener. It is supposed to be the clearest and most flexible when cured. It is definitely both. On the first board, I did a lam coat and an epoxy filler/hot coat. On the second one, I’m doing both epoxy coats and then also a poly gloss coat because the buffing out is more predictable to me. Epoxy is really, really hard to sand. It should also stiffen up a little more with that. Keep in mind that most epoxies aren’t completely cured for 2 weeks. Also, if you don’t have a perfect mix, it might never set up hard. I’ve also found that if you’re glassing in weather that’s too hot, or you heat up your garage too much to try to accelerate the cure (like I do with poly), or if you put the board in the sun, it might for some reason take much longer to set up hard. All the glassing & ding repairs I’ve done with epoxy seem to like 65-70 degrees, not more.
I think I have enough glass to do three pieces on the deck. I think that is what it is going to take although there is something unappealing about having a board that will compress even if it does spring back. I don’t want the board to feel disposable.
yo marke. all the epoxy/ eps work we used to do involved vacuum bagging on a kauri (new zealand native timber species) 1mm veneer. we did this to help resist the spongy gig you mentioned ( they were damn-near bullet proof, and still insanly light). 4oz to seal the eps blank, then wood veneer (vacuumed on), then 6 oz plus generous filler coats. at that time in nz there was no good "clear " epoxy available, so the yellow tinge we got was diguised over the warm timber colour. im sure you could get away without the veneer - just more cloth… the boards looked stunning- my only criticism would be the “corky” feeling of the extra bouyancy in the expanded poly blank!! you have to really tune down your volumes to achieve a comparable feeling to the of a standard polyesther board. ( and i already ride small boards)
good luck bro, but im still in the p.esther camp myself
ps. you might want to check out www.supersession.co.nz, a label at my old factory, legends in epoxy!
Your probably using 1# density. Laminate that with two layers of 6 oz on the bottom and three layers of 6 on the deck. This comes out quite light and has good strength. If it’s 1.5 use a two layer bottom one 6 and one 4 and three layer deck of one 6 and two 4’s. For 2# use two 4s on the bottom and two 6s or three 4s on the deck. EPS will dent on the deck until your using about 24 oz. This is a bit heavy but not as bad as you might think. Even though EPS dents it won’t delaminate and initial denting will appear somewhat bad but will only go so far and then stop. The use of veneers, spheretex, coremat, balsacore, divinycell and other core materials on the deck will eliminate denting but this does make the board quite a bit harder to make.
If I buy more glass should I stack up deck patches and only go around the rails with one sheet on the top and then do a patch on the bottom rather than wraping two pieces around the rails each time.