Got a question for the EPS guys. Previous posts have listed the following density numbers for Clark foam:
Ultra 2.35
Super 2.55
blue 2.75
green 3.0
EPS density has been listed at 1.0, 1.5, 2.0, 2.5, and 3.0.
Assuming a conventional hand layup of the glass (no composite vacuum bagging) and using RR epoxy with a 6x6, 6 glass schedule -
Would you expect more or less denting of the deck to occur?
I would never have considered using an Ultra light 2.35 clark blank for a longboard but the middle-of-the road suggestions for an EPS blank is 2.0 or 2.5 density.
I have made a number of boards using clark super blue glassed 6x6, 6 with RR epoxy and they have dented more then a comparable 6x6, 6 poly.
Am I missing something about EPS or should I go with nothing less than 3.0 EPS when doing a hand layup?
the increased denting you noticed is a factor of the increased flexibility of epoxy resin. over clark foam, the glass/resin flexes and compresses the foam, resulting in a dent. with EPS, however, the foam will spring back, and will not leave a dent the way clark foam will. when i glass epoxy over clark (or some other polyurethane foam), i use a denser foam to minimize denting (usually “classic” weight).
Since question answered i guess I can do a small hijack…this means better “memory” in the foam so my question is about using EPS in a flexspoon type board. Generally, with pu foam , the blank is removed after glassing the bottom and replaced with high density pu pour foam (8-12#) because ordinary blank will disintegrate fairly rapidly under frequent large flexing motion. Is ti likely then that EPS will hold up significantly better/longer than the pu blank under those conditions so maybe can skip the removal/replacement labor and money and still get a board that will last a reaonably long time?
I’ve procurred a number of foam samples over the past year and done some testing. My results indicate the lighter densities of EPS (i.e. .75 - 1.5 lb/cu ft) are very springy… you can squish the foam and it rebounds. The heavier densities dent and stay dented.
Because of this and other issues, you will find that I’m pretty careful about specifying what type of foam and what density when discussing things like venting, water absorption, bouyancy, vacuuming, “EPS” vs “urethane”, etc.
Even EPS of the same density from different sources can vary as bead size and how the beads are bonded affect the foam structure. I’ve seen shitty EPS with pockets of beads that aren’t bonded at all.
In a flex spoon, I’d say do your own testing with various densities of EPS as each density seems to have it’s own character.
We’ve seen some dent like a golf ball and others that didn’t dent at all.
Same 6/6-6 and 2# eps foam.
The variable may be cure time. The golfballs were surfed days after laminating.
The cure time for poly might be a wivestale but for epoxy, I’m really starting to wonder if a good 7 days + is a good idea for epoxy up here in the colder climates.
Then again, maybe I should wear my respirator more often.
In colder climates it does take longer. Talking with the guys in NJ they go about two weeks in winter before riding the boards. You can post cure in a simple oven overnight at about 100 and this will help a lot. In FL we almost always are working in 90+ so we never saw the slow cure thing accept occasionally in winter.