Ive been shaping polystyrene for a while now and i want to move on to shaping eps foam. Ive worked with epoxy resins with some glassers and am finding epoxies to be much more practical and easy than polyester resins, but ive never shaped eps or xtr before. I dont have enough $$ for an xtr blank so im just going to start with eps. I have heard stories about chunks of foam falling off since eps is that open cell, beady type of foam. Anyone got any tips to help a first timer so I dont destroy the blank and break the bank?
I am assuming you mean that you have experience with polyurethane foam.
EPS is polystyrene.
It will all depend on the density of EPS that you buy.
Many on here will disagree but i feel there is no real benefit in using higher density EPS over the same density PU. the PU will last just as long is easier to shape, finishes flawlessly and for me personally it surfs way better and you can order just about any rocker you can think of in a close tolerance blank.
Low densities under skins on the other hand are a whole different animal.
I finish all EPS blanks to #100 only then seal then glass.( with normal hand layup.)
Some beads may break away if you try to remove too much material too quickly. take your time and you wont have any problems.Good quality EPS can make the difference as well.
Nothing wrong with putting epoxy over PU either. Very strong possibly safer for you and your neighbours and pretty easy to use.
I use the same tools and procedure for both foams. I use sand paper instead of dry-wall screening to blend the rails. Go slower, more frequent passes so you dont tear out little chunks. Spakle, laminate, nice light board. Mike
Firstly polystyrene is not polyurethane in more ways than one. I “rough” sand EPS with 220 grit when I’m finishing off the shape. I find 80 grit just rips EPS no matter how delicate you are with it. That’s my only tip.
Start by buying the best foam you can afford. I like Marko.
Go slow, and move through your grits sooner than you would with PU. By that I mean don’t go as far with each grit. Leave more left for the next grit. If you do that, you’ll end up with a smooth surface that requires very little filler, if any.
For “performance” boards, including HP LBs, I go for the lightest but strongest board possible with traditional construction (not a compsand), so I seal with a minimal amount of resin/microballoons. Many use spackle, and the debate still rages. Glassed with 6 oz all around, you get a stronger and lighter board than PU with 4 oz all around.
Do as much as you can with the planer, EPS planes very well. I don’t use screen except for final ‘‘polish’’ with foam pad. Sandpaper works much better for me. Once you get used to it, good quality EPS is a pleasure to shape. I much prefer working with it compared to PU.
I forgot to post about this, but I bought some of those “micro-blades” for my “surforms…” Best thing ever, a little slower than standard blades, but doesn’t tear beads and leaves a finish so fine you could probably glass it and be fine.
The one tip I have, that wasn’t mentioned is; clean your tools frequently.
My recollection of urethane foam was it made dust and fell right off, but styrene seems to build up and then you cant get unevenness which may lead to “tearing”/pulling beads.
success! it went really well. I mustered up the courage to use the power plane but just took it slow and kept the cuts shallow. then hit it with 220 grit. i didnt have the problems i assumed i would have with it.
With a double 6 oz deck + patch and double 6 oz bottom you should be OK if you allow for a fat overlap of all layers. Just try and stagger where the laps end so you don't have a big step.
I'm not sure about price... I'd have to do too many conversions to figure that out.
I don’t know what that is that you’re looking at, but a foam core that’s typically 2lb deinsity EPS will have 10% deformation at about 35psi, which is somewhere between 200 and 250kpa. The higher the density, the higher the psi needed to cause deformation. Most EPS surfboard foams are 2lb, with super light cores and composite sandwich skins using 1lb.
I find that you can make a board much faster with PU/PE. PU shapes so easily and the dust falls to the ground. I usually collect as much as I can while I’m working and bag that for use as a resin thickener. EPS beads are so light that they will fly all over the place, and they’ll stick to everything. I think you have to work a little harder to get a finish as clean as what you can get with PU blanks, but I don’t buy quality EPS blanks. Maybe it’s different with the good stuff. We’ve tried Marko blanks when they first came out and they were good. What I use now is a fraction of the cost, so that’s why I use it.
I’m not sure how others are doing, but the EPS blanks I’ve glassed without some sort of skin are not as durable as a PU board glassed with the same amount of glass. I think epoxy resin is more flexible when dry, so it seems softer than Poly resin. The combination of epoxy resin and composite skins, makes a flexible but strong shell. I also think it is easier and faster to sand PU resin. Epoxy will clog the media quickly.