Air expansion / delamination / whats the reason???

[willi]

I am a beginning builder of SUP boards in Florida --Yes, it is hot, and the sun unmerciful.
I have had two boards delam under the deck pad. Big bubbles - the epoxy & glass just pulled right off the EPS --wow --I thought what is goin on --yes, it was my fault I left them in the sun for a bit--(board color left natural)-BUT
 as I contacted two folks in the EPS foam industry to talk about going to 2 lb instead of 1.5 --figuring there would be less air in the foam to explode.
But, was told the air is encapsulated into the foam and there should be no expansion of the air in the foam. Two seperate experts -- two seperate conversations. Hmmm?
COULD it be the deck mat? I had a darker blue-ish / white / etc on the boards -- at my shop I put the deck mat out in the sun and man did it get hot -- but the deck mat also expanded
(I measured it before and after the sun teatment ) The mat is EVA foam 1/4 inch thick adhered with contact cement. No grooves in it.
The second board that blew up --I had sealed the EPS with two coats of epoxy (makes for a nice working surface) so there was good adhesion on the second one.
OK mates, lets hear about it because I am stumped --As I just wrote in the Certification blog -knowledge is power. I am listening.

[finsider]

Im not certified  but a denser foam will have less air voids within the foam (between the foam beads). The air is affected a lot quicker than the foam itself, so less air voids should mean less chance of delam. Are you venting your boards? I've heard of some people putting a vent both front and rear for big boards, and dark colored deck pad will definitely make it hotter. Hope that helps some.

[juandoe]

I would still say air.  Each of the foam beads is a closed cell but the gap between the beads still contains air.  There is the possibility of outgassing of volatile organics as well. 

[bean]

Yes check boardlady.com EPS will out-gas at 130 degrees.

[PhantomSup]

Yes. EPS will without a doubt outgas, blow air, fart, whatever you want to call it. when it gets hot it will blow. I have repaired dings in all kinds of EPS boards and they will all gas. EPS and epoxy is good stuff but heat is an enemy BIGTIME. I would suggest venting your boards.  Also you are correct on the pads they get hot as hell in the sun as well. 

[willi]

OK Phantom SUP-- I am try to be a good listner --
How about -- going to 2lb EPS and changing to a C bead size (smaller beads)
I am told it will shape better----- I am not sure what this will do to the weight of the board --Yes 2 will be heavier and more ding resistant ---AAARRRGGGGG more beads and less air -- and a light colored deck pad ..
and how about grooves in the EVA (not solid like I used)  to /  help dissipate heat ---
the grooves provide more surface area to cool and in some cases a slight shadow onthe valley of the groove --(my girl thought that one up)
Thanks for the thread -
-anyone doing SUP / VacBagging want to trade ideas ---

[adios pantalones]

Not only is the deck pad darker and a heat collector, it too, is foam, and an insulator as well.

Vents should help, but just like a prone board, mine always are laid face down, even if only for a few minutes.

[Allan Cheateaux]

Those are all good things to give a try. When you seal it, make sure you take it back down to foam. All you want to to do is fill the voids on the outside of the blank, and expose the beads on the outside surface to have something for the resin to adhere to. To much spackle and it wont bond.

Watch your laminating temps, as I've had better luck with with a much warmer laminating room. Also try to post cure as much as possible.

But a vent is always a good option to save a lot of deck work later.

[Absolutetrip]

Reading Willi's other posts on this issue, this is what I gathered so far.
Willi has a roll of what he calls 6.5oz tight weave hard to get the air bubbles out of, not like a E glass. Humm?
I would guess the good deal on the cloth you got is a roll of Rutans airplane stuff real tight weave almost looks like a denim weave. very tight with strands running 45 degrees and 90 and 180. Good stuff for vacuum molding parts and it is not designed for hand laminating. If this is the case there is your problem right there you are not getting a proper bond when laminating this stuff on the board due to the fact it is so hard to get the resin through it and achieve a proper bond. And yes everyone I have seen use it on a surfboard every board I have seen with that cloth has blown the glass right off the board.

Here is a leg up I have gelled thousands of gallons of polyester and epoxy resins. Here is what I recommend. Call Greenroom epoxy buy their resin and some of their slow hardener follow the directions mixing the fast and slow to get a gel time you can deal with. Also buy their cloth with their special silane finish in it. It makes doing epoxies easy er or ish. Also spackle your board sand the spackle with a 100 grit sand screen. for the simple reason you save resin and work and come out with a better product. Also if you do not lam the board within 24 hours of coating it with resin your bond becomes suspect unless scored with 36 grit for proper bonding. Specially if you are using a epoxy that blushes badly. Then you can throw the toulene/xylene whatever can ie additive F in the garbage. 
 

[PhantomSup]

I don't think going to 2# foam would really change much. It is more a matter of sealing the blank and laminating it correctly and I still prefer a vent in the finished board to eliminate any problems. I have worked with polyester resin and polyurethane foam for over 30 years with little to no problems. I'm still old school on boards but the new materials do have good potentials.