ive done about a dozen or so EPS/Epoxy shapes, but have yet to run into what i saw last night. a customer brought backa 9’3 i had done for him last summer and along the stringer about 12" above the finbox, the glass had sucked down on both sides of the stringer, looking like it had sueezed down the EPS and creating mini-channels on either side of the stringer, about 3 inches in width.
anyone have any ideas why or how to prevent this? how about how to fix this one?
thanks
jz
Heard of that, but haven’t seen in real life - looking forward to learning more.
Hey JZ,
sounds very interesting, may just be foam failure, not from anything you have done. it happens.
Pics and blank/epoxy specs would help too
shannon
I would go with a foam failure also.
Cycles of hot and cold. Shrinks the foam because the air gaps between the beads are now smaller.
I second this opinion… especially if it is a lower density foam. Rapid temperature changes and or pressure changes (did he fly the board?) could do that.
is it ‘exhaling’ through the porous stringer wood and focusing the failure there?
I’ve seen this a few times on poly boards…generally I would consider it foam failure as well…but that was on poly.
I’ve never seen an epoxy suck down/collapse like that…but I would still look at foam first.
Like others here have suggested…foam density etc.
As far as repair goes…I would score and peel back…fill in with a microbaloon heavy mix and let set…
then replace the existing glass, patch and blend.
Just my 1.874 cents
If the blank was glued up with a water based glue then in some cases the laden water that does not dry - even through the finished product can increase those effects of cold/heat extreemes.
Only use EPS that is glued with non water based adhesives.
It sounds to me like that is the case since when you glue the things up you can expect the glue soak as far as 2 to 3 inches in the foam if it is not a tight fuse, or the glue is more runny.
No, the stringer and the glue line aren’t really permeable, nor do they expand/contract with the foam. It’s basically shrinkage of the blank in thickness where the original air gaps have changed in size, maybe more pronounced due to large bead sizes. Although similar in appearance, this isn’t the same condition that was often seen on some of the softer Clark poly blanks. Sometimes those were over-shaped exposing very soft density foam which compressed when ridden but the glass still remained bonded. On very low density EPS, similar compression can occur, but extreme heating cooling cycles are more often the cause.
That board got hot. The foam probablt melted in a spot from exposure to extreme heat. Over 180F melts EPS and the only place I’ve seen this is inside a car. I’ve seen probably a dozen or so of these in my 28 years of building EPS epoxy. Will happen more often with lower density foams than with 2#. 2# almost never does this. ALMOST never.