I have 7’2" epoxy eps board that is about 1 1/2 years old. It has one layer of 6 oz. on the bottom and two layers of 6 oz. on the deck with a six oz. deck patch. It has about 300 sessions on its sessionometer. There are some foot dents on the deck but no delams or stress fractures. When it was new, I could press my thumb into the bottom and make a small dent, it seemed like it was a little soft but now when I try to do the same thing I can’t, it seems to have hardened. My question is " Is the board getting stronger over time or am I getting weaker?"
Did you leave it in the car on a hot day?
Both Epoxy and Polyester keep curing over time. A gentle heat prior to use is good for any new board.
Alternating heat and cool-down is better than merely a short intense heat blast.
The pic below is a finished board in the hot-box made from foil and a hair dryer. Its good in my climate down south.
Josh
I leave my board in the bed of my pickup truck which has a black fiberglass tonneau cover. So, maybe the heat has helped cure and strengthen the board?
Yep, a slow bake…
Too much heat is never good but.
There is of course a point where it becomes optimally hard, then starts deteriorating. This takes years and years…
All the best,
Josh
I was once told that epoxy takes months to fully cure. After about 6 months, it’s about as hard as it’s going to get. But polyester reaches “full cure” after several days.
This could be bad information, but that’s what I’ve always thought.
With epoxy lot of it depends on the manufacturers recommendation, and generally a good quality epoxy manufacturer will have a recommended post curing schedule of slowly increasing temperatures spread over a 24 to 36 hour period. It’s then pretty much as hard as it’s going to get. We used to do up to 80C.
Without baking it seems it continually cures, but only to the point of the highest temperature reached. If it gets any hotter it starts further curing again so softens a bit.
I’m with Josh on the PE resin. Cold and hot alternating, speeds things up a lot.
This is one of epoxy’s real strengths. Upon initial cure it’s much tougher than polyester and in time it gets much tougher still. It’s adhesive qualities and it’s basic molecular structure allow the stuff to bond with the matrix and accept loading and unloading for extended periods without the breakdown seen in polyester resins. This advantage at resisting fatique creates boards with much better performance lives.
What Wildy is talking about is post cure and this shortens that cure cycle from months down to a few hours. Generally a fairly agressive post cure like the one Greg suggested to 80C (which is about 180F) will get you results in a very short time. With surfboards and the foam we use this can only be done to about 150F so the post cure must be longer. Generally post curing a board to 120F (50C) for 12 hours is going to give you enough of an advantage that it’s worth doing.
is there a methodology that you would recommend for the heat/cool cycle that was alluded to?
or would you prefer just going whole hog in a hotbox for 12 hours instead?