First Board Trouble - Melted with Heat gun

New poster / completely new shaper here - I got to the point of laminating my board - all without a hitch until I had some dry spots on a freelap. I thought I would mix a small amount of epoxy and wet out the glass so as to have something to sand down instead of rubbing around fiberglass. This worked well in theory but had trouble curing, which I tried to alleviate by applying some heat from a heatgun to the uncured resin. This of course was a huge mistake and ended up melting the EPS foam underneath the glass. It feels squishy / soft in those small parts and I have no idea if there is anyway to try to salvage this board. I am really trying not to be wasteful - any advice to make this board in anyway rideable(I know it won’t be great and probably noticeable in water)? 

 

  • Help a kook

Oh dearie me.

Still, call it a learning opportunity. At least you didn’t set it on fire. There are those that have managed to do that. And next time, you’ll use more resin. Better to waste a little resin than…yeah. 

And, a picture or several would help a lot. 

In the meantime, and all could change once we see it, I’d suggest you treat it like a ding repair. Open it up, gently remove what I’ll bet is ‘former foam’ gone soft and shrunken, fill and sand to fair it to the shape it should be, glass over. 

Now, some people do dings and the irst thing they do is whip out a router and attack, attack, attack. Generally it’s a very bad idea, they make a simple, easy repair into a giant clusterfuc#. This might be that rare exception- if you have a plunge router and you’re good with it you might want to think about that. . Otherwise, no. 

What to use for filler? You could slather in resin plus foam dust or cabolsil/aerosil mixed in to thicken the resin to a useful filler paste- but it’s heavy, hard to sand and you wind up with something pretty obviously a repair.

You could very carefully cut a chunk out and glue in a precisely fitted piece of foam ( the router method) but that’s a lot of work and while it can be nearly invisible ( when done really well) most don’t do a very good job and it looks like the hack work it is. I’ve seen some, gah, they looked like somebody made one of those Jello with marshmallows desserts, foam floating in resin. Horrible. 

Last, and easiest, going on the supposition that your foam is white, use White Gorilla Glue, the stuff goes off and expands as a white urethane foam, fills irregular spaces nicely, sand to fair it in and glass over. It should be compatible with your EPS. Taping over your glue as it goes off with wide masking tape gives a little pressure before it blows off, makes for a denser, stiffer foam.  

Again, this is just a preliminary wild guess without seeing what you’re up against. In the meantime…

hope that’s of use

doc…

Doc is steering you right.

Just wanna add…

If you have trouble with your epoxy curing, it’s because you:

A) messed up your ratios

B) didn’t stir thoroughly enough

C) are glassing in freezing temperatures

100% it’s one of these three issues.

Thank you Doc for the insight! - I took your advice and cut out the glass in the area of effect. The foam underneath was indeed singed and the crevice was about 1/8" deep. I bought some gorilla white and will try your method of filling openings, sanding them down and reglassing the area. Would there be any reason I would just glass the entire bottom again? I know this will add weight but might unify some of the repair textures.

I think I definitely didn’t stir enough - the small amount of resin I mixed starting kicking in the cup quickly but didn’t cure when I wetted it out. 

 

Will upload photos when I have them filled. 

 

Right? Styrene foam, unlike urethane foam, can sort of melt/soften with heat or the right solvents, and that’s what bit you. 

chrisp is smack on with his suggestions on epoxy use, at least in my somewhat limited experience. Mixing the stuff by volume can be problematic - epoxies tend to be finicky when it comes to exact proportions. I’ve used the proportioning pumps and gotten it wrong. Doing it by weight is better and a cheap electronic kitchen scale (1-3 kg capacity, gram scale is all you need) should work for measuring by weight. Nearly all epoxies will have tables or proportions for measuring your mix by weight, they tend to be more precise. And that’s never a bad thing.

Getting it mixed really well, reasonably quickly, without getting a lot of air bubbles in it, that’s tricky too. Oddly, I found the ‘folding’ techniques high class cooks use on things like chocolate mousse to be useful They do it that way so they don’t ruin the foamy stuff they are working with, but I have found the same technique mixes epoxy resin without making it foamy. That’s me, your mileage may vary, etc.

Now, Gorilla glue, being as I’m old and somewhat senile I forgot to mention it’s what’s called a moisture catalysed urethane: it needs a very little water to make it go off. either swiping the girlfriend’s plant mister to give it the faintest touch of wate

r or a couple of dabs with a damp sponge or clean rag is all you need. 

(quick edit) - use a fairly thin layer of glue. It expands quite well. Use too much and you have The Thing That Ate Milwaukee to sand down. 

Reglassing the whole bottom- you mentioned weight, which is the biggest deal, and that’s not really that big a deal. Board will be slightly stiffer and stronger too, which isn’t a bad thing. Assuming the bottom isn’t especially lumpy I might lay some light cloth over the cutouts on the repair as you do the job, just to avoid potential weak spots, but that’s really all I’d add.  

Anyhow, I’ll let you get back to it -

hope that’s of use

doc…

I would have just drilled a hole in the glass and injected some expanding foam into the void.

I sure as hell wouldn’t put a second layer of glass on the bottom. You have already created an imperfection in the board. Just repair that spot and live with it.

Want to warm a particular spot to cure it faster? Use a hair dryer on low heat, never a heat gun.

I hear guys talking all the time about injecting resin into delams and dry spots;  They obviously have never tried to do it.   What chrisp said is matter of fact.  These kind of f—ups occurr when you haven’t thought the process out and get in too big a hurry.