shaping eps take - 2

Questions about eps - if I use 2.5# , which has been called similiar to superlight , does that mean that the density and also the weight are similiar, and in turn the buoyancy similiar. If so that would seem to indicate that if I make a 6’2" with the same stringer, shape and with the same (4x4,4) glassing(but with epoxy resin) the board should float similiar and flex similiar to a board recently made from a 6’3"r with pu resin ?? If I make the transition I don’t want all the new learning to result in a reject board.I see this as a big deal cause none of us want to go backwards. Ideally at this point I think we (I) could benefit from an indepth guide to using eps and epoxy. - especially with regards to the performance of the board. I believe it would be an easier transition if we could start by being able to get close to the performance of pu for starters. We can always innovate from there.

It should be pretty close. But, I’m no shortboard expert.

I would suggest you get 2-3 blanks. They’re cheap, 3 should cost you less than $100. Get a 1.5 gallon kit of RR - also $100 or so. Use a wet-out table or fold up your cloth to wet it out, and even if you’re just getting started with epoxy, 1.5 gallons should net you 3 shortboards. Your lams will be nice & tight because of the longer work time and you can hotcoat thin by warming the resin. Then just sand & surf em. You probably already have some glass & fins, but if not $200 more should get you enough 4 oz & glassons. So for $400 max, you can do 3 shapes.

To start, I would certainly suggest you keep the same rockers you’ve been using. Keep the same templates.

Make one just like your normal board. Make another one, but maybe 1/4" thinner. Make the third both thinner & with the reverse-outined Bert style bit at the tail. Surf all 3 & let your friends do the same.

I mean, we’re talking about feedback in less than a week. And you’ll immediately be more of an expert than anyone else you know.

hey Benny - I appreciate your reply’s - down to earth - thanks. btw what is 'reverse-outlined Bert style bit at the tail ?

hey Benny - I appreciate your reply's - down to earth - thanks. btw what is 'reverse-outlined Bert style bit at the tail ?

Any word on where we can get EPS and epoxy supplies?

Epoxy resin is somewhat lighter than PE, so for the same glassing schedule and shaped blank (other things being equal), the resulting board will be a tad lighter. I haven’t seen a convincing calculation that establishes the mass density of Clark Foam. I suspect it varies more that we were intended to know, and this is why it was never published. Consistent density is apparently part of the “art” of pouring the liquid foam at the Clark factory, and one of the reasons other foam makers have come and gone.

Neither do we know how well the density of EPS is controlled from billet to billet.

This suggests an EPS/epoxy board made identically to a PU/PE board could weigh a little less for the epoxy, a little more or less for the foam.

Honolulu - that makes sense, now how about flex ?

Well, you answered some of your own questions. I think you need to search the site first and you will answer the rest and more that you don’t know about. In any case, density is mass/volume, so if you build the same volume and the masses are equal, your blank weighs the same (disregarding different stringer materials). That doesn’t tell you much about flex though. It’s hard to let go of something when you are so familiar with it, as is any good relationship. Personally, I think my eps boards work as good as pu/pe, but it’s been so long since I’ve riden one of those (besides some classic longboards), that I can’t really compare anymore. I bet you can always find someone to ride a reject board, somewhere.

Clark foam densities did vary some but in lab testing this is what we got over and over.

Ultra 2.35

Super 2.55

blue 2.75

green 3.0

EPS is available in many densities but mostly in 1.0, 1.5, 2.0, 2.5, and 3.0. These weights are pretty accurate as that industry has building standards. Strength to weight on EPS is much better than urethane.

2.5 and 3.0 don’t need sealing like the lighter weights.

2.0 and up have little or no water absorbsion problems through dings. 2.0 and up don’t need vents.

An EPS board of similar weight density will have very similar flex and exactly the same buoyancy as a urethane,

The epoxy laminate will be somewhat lighter than the same glass schedule with polyester.

Thanks, this is the info I needed. I’d suggest this info be put in the epoxy/eps primer - Thanks.


What should a blank be finish sanded to if I don’t seal I’m using 2lb and I got a rush order?



What should a blank be finish sanded to if I don’t seal I’m using 2lb and I got a rush order?

I think Greg said he finishes with 80, I took mine to 100.