Are you talking about O-C Foamular 150?
If so, O-C Foamular 150 foam is XPS and is 1.3 pcf with 15 psi min. comp. strength – tears and crushes easily.
There is a lot of information posted here at sways about using EPS and XPS foam. This is a topic that has been discussed many times…
http://www.foam-control.com/?pdf=/Foam-Control%20EPS%20-%20TechData.pdf
The stuff I use is the FC150.
Picture below was cut last week.
The only reason I use insulation foam is price. I have been able to get it for as little as $5 a board, and I’ve bought used blocks from floating piers that I bought for $5 each that I can get several boards from. Going cheap has it’s problems, so I don’t recommend it for your first attempt.
The first several EPS boards I made were either a stringered slab or a pressure molded Marko blank. At the time, Marko just started making the individually molded blanks, and we were able to get them at very good prices. They’ve gone a long way to making better surfboard foam, probably the best EPS surfboard foam right now. My brother and I were making wood skinned boards, and he created a process that allowed us to take EPS foam from our local Home Depot or Lowes and make our compsand boards. Before that we used Poly blanks, but the boards were heavy by comparison. My brother thought about trying the insulation foam, and it worked out. This was in 2005 before the Clark shutdown, so we lucked out by having experience using EPS and epoxy, and what we were doing wasn’t affected.
My opinion…
If you buy a superfused molded EPS blank from US Blanks or a Marko molded blank, you are buying something very similar to a Polyurethane blank but it will melt if you use polyurethane resin. These blanks are pressed into a mold individually and they end up looking very much like a molded polyurethane blank. That means there’s less work needed to shape a board, as long as you use a blank that is close to what you want to make. Because these are pressure molded individually, the beads are smashed together really tight, and it’s close to water proof foam. You can sand these to nice finish before glassing.
The surfboard slab EPS is precut from a huge block to a specific rocker and has a bit of thickness profile cut into the foam. They come with a stringer, but they are rectangular. Because the foam is made in huge blocks then cut into the slabs, the foam is not pressed together as tight. The finished blank often has tiny dents where beads were pulled up from sanding. With some of the slab cut blanks, you may need to do a fill coat or a spackle to keep the foam from absorbing too much resin.
I’ve used both types of EPS and I really like the individually molded blanks, but they will be as expensive as a poly blank, sometimes more expensive, and they don’t have as much choice. Marko Blanks are very good. The slab cut blanks are priced almost as high as the Poly blanks too. Having the rocker, profile and stringer done makes it very easy to shape a board quickly.
By comparison, industrial grade EPS usually cost a lot less depending on your source, and how large a piece of foam you buy. You’ll probably want to fill coat or spackle this foam too. The stuff I have available to me from the local hardware stores is 1lb foam or less than 1lb. It is way too soft to use without a lot of glass, or an outer shell (skin). I use this foam for composite sandwich boards that have a wood skin and fiberglass. If you can get foam between 1.5 lb or 2 lb density, you will have a reasonably stiff foam that will make a decent board using standard glassing schedules. Personally, I’d get a 2 lb if I could. Then you have to think about the rocker, do you cut it out of the block, or press it in? I usually don’t cut out a profiled slab the way most guys do because I don’t buy large blocks. I cut out rocker slices from narrower sheets (3" or wider) and glue them together to get the width I need. Depending on the thickness of the foam, I can get 2 to 4 times as many boards from the same piece. I also add a 1" perimeter band to get the outer rail clean. There’s a lot more work when you use EPS insulation foam.
The other insulation foam, XPS, which can be blue, pink or yellow, is a different animal. It is stiffer and waterproof, but because of the process they use making it, it has bonding issues with resin and it releases gas when it heats up. I’ve used XPS for at least a dozen boards, and I like the way it shapes.
For flex, I’d say EPS can have the most flex, then XPS, then Poly. But, Poly can be bought in so many densities now, and I only used older blanks. Also, poly blanks usually come with stringers, and stringer also determine flex. I have been able to get 2 stringerless Poly blanks about 10 years ago, and they were as floppy as any EPS if not worse. I shaped them into stringerless boards, and they worked out just fine, but I had experience shaping stringerless EPS, and controlling rocker with rocker sticks and weights. You can also adjust the distance between the glassing stands to get a certain kind of rocker using a floppy blank.
I tend to be a bad choice for flex help because I prefer stiffer boards.
All of the experiments I’ve done using the insulation foam I have available in my neighborhood stores left me with 2 conclusions… unless I’m making a skinned board the foam is too soft, and it’s way more work to make these boards. Once I get through all the chunks of foam I’ve collected over the years, I probably will just use precut surfboard slabs for EPS, or molded blanks. If I make wood skinned boards, I’ll continue to use the softer Home Depot EPS. I should also add that you will need to add something under the fins to give it more strength, or you will have problems. We either add a piece of heavier density foam, or wood.
To Mathie…
Immediately go back, and re-read post #6 above. It is the definitive statement on the ‘‘how to’’ of making an EPS surfboard. When you’re done, read it again.
I’m with Bill and Bernie, except, when it come to flex, I found the 2lb eps blanks I cut from a block to be much stiffer than the @ 1.5 lb xps I’m using these days. I get 2’x8’ sheets in 2" or 3" thickness - insulation - from the local lumber yard. xps has different qualities to be sure. I think it is the most challenging to shape, as it tears the most, but I try to be careful, fill in major problems, and don’t care what it looks like on that level. What I love is, if I get a ding through the glass, since xps is 99.98% hydrophobic, I don’t have to worry about water infiltration/migration. I also drill preemptive vent holes, and haven’t had any problems with bubbles/delamination.
There are so many ways to approach the building of the proverbial pool toy. One thing i like to keep in mind: the blank is just a form to wrap the glass around… “Wink!”
I found that with XPS, you have to move the planer slowly. If you have sharp blades, the tearing is usually from moving forward too fast. I get super smooth cuts when I move slowly, but it will tear when I move quicker. The same for EPS, if you see tearing, try to slow down.
The foaming glues work well with both EPS and XPS foam.
If I recall correctly TaylorO, you are using Owens Corning Foamular 250 XPS.
What glassing schedule are you using with the OCF 250?
Hi Bill, You got a better memory than me, but as I was thinking about it, I realize I’m working with what I have around town, and am not too concerned about those details, as it’s working well for me.
From my thread about the tail reconfiguration, re. my glass schedule: 4oz X 4 @ 90o, and 4oz X 1 @ 45x45o = a diamond tail patch on the bottom up to about 4" in front of fins, and on the top from the tail to about where the top of my chest lies while paddling. I fully wrap all the layers around the rails as much as possible. I’m also drilling “vent” holes, with the tiniest bit I can find, on about a 2" grid, along stress point/joints in the foam, and on the deck in possible high pressure areas under by feet and butt (the one place I blew a bubble once), and I haven’t had any challenges doing this (per a suggestion from a pro here on Sways years ago) to several boards.
What stokes me up about the lower density of the foam: The Sally 4 has more volume and glass than the Sally 3, but weighs noticeably less… And, so for, knock on epoxy, the heavy glass schedule has revealed only scratches after many encounters with the rock reef here.
Hi Bernie,
I’m just above caveman here… I don’t use the planer that much - If I get a gouge it’s from rushing/sloppy use of a surform or sanding block… Ha!
If I feel the need to fill, I mix a very thick putty of epoxy and glass beads. I feel like I had worse water intrusion issues with dings when I was using spakle, that is, if i had a ding that compromised the skin enough to let water in, the combo of eps bead and spakle got pretty crappy - like, in just the remainder of the session amount of time was enough to mess it up.
If it’s the first time shaping a board, go with the Home Depot stuff, it will help you learn and if you do a good job, you’ll have a surfable board. I’ve made a few with Home Depot foam and yes they can tear, the glueup lines will show through, and there is a definite possibility you could get a delam (happened to me) but seeing as it’s a low price it doesn’t really matter.
Our first catastrophic fail was trying to glue hardware store EPS sheets into a rockered assembly the flat way with Elmer’s white glue. It worked on the test piece but not at full size. The glue never dried in the middle of the blank and we ended up pitching the works, material and rocker table. Now I just use Goriila Glue (foaming PU glue) or epoxy for EPS.
Second time, to replace the above failure, we got this piece of roofing insulation EPS:
https://www.brockwhite.com/catalog/materials-and-accessories/insulation/eps-insulation/1-0721196
At 6" thick we could hot wire the rockers, and at 48"x96" it was not ridiculous to drag home. We got 3 boards from the above piece- 2 that were whole and the the third was made from scraps.
If you’re only choices are EPS or XPS from Lowes, Home Depot or another local hardware store, be sure to ask what the density of the EPS foam is.
In my opinion, 1 lb or less is too soft for a durable surfboard. EPS foam with a density of 1.5 lb or higher will be OK. Just squeeze the foam with your fingers, a light EPS can be smashed down easily. One surf session and you will have a board covered with pressure dents, even with 3 layers of 6 oz glass.
If you have a choice between 1 lb EPS or and XPS like blue Dow styrofoam or pink Owens Corning styrofoam, I strongly suggest going with XPS. When you shape the foam, just sand with 60 grit or 100 grit and then glass it.
I’m working on a Home Depot Compsand now, https://www.swaylocks.com/forums/home-depot-compsand-build, and I can’t believe how soft the foam is compared to the XPS and slab EPS I’ve been using for a while now. I just threw out pieces of old 2 lb EPS foam I bought about 15 years ago, and I was amazed at how much harder (and heavier) that foam was.
I agree on the mush from spackle in dings.
I now make a thick mix of white undercoat and beads to smooth the EPS blank after reading about it on Sways. Also makes a nice base for acrylic spray.
the only reason I looked at getting my foam from Home Depot/Lowes was because I hated walking in to FH and getting the “beat it kook” looks from the sales staff because I wasn’t in the industry with a wholesale license and was just a garage hack.
So I said F that and I’d figure out how to build boards without relying on nothing more that my local hardware stores. I could get my foam from Lowes and my resin and cloth from City Mill which sold FH materials.
It was truely a pure garage hack experiment from the sheet foam to the industrial plastic saran wrap I used in place of a vacuum setup. We learned allot going through those early stages from the pumps to buy to the bags to the types of glue and skins to use. But at this point we have it down to a science
I always felt it just like making sushi aside from the actual shaping.
But without a shaping room with lights we weren’t expecting to be making boards to sell.
In the end we actually put out some pretty interesting, good looking and even decent riding boards.
Hell my first shaping EPS was done using a belt sander and 36 grit belts along with a 2x4 with a cut 36 grit belt for the flats.
Super low tech inspired by Shwuz, Benny1 and MrJ in the crazy days before Bert.
When you’re bagging 1/8" to 3/16" planks of wood on the outside of the foam core with glass under and over, the 0.75-1lb cheapo insulation EPS works just fine.
Shaping a Marko blank and glassing it seems so much easier than build you blank first and bagging on a shell.
Doing a poly blank with UV resin is even simpler and faster.
So if you want to just shape and glass and put in boxes without worrying about reinforcements, I would just stick to the industry supplied stuff.
Hell even easier just send your program to a cutter and have them do most of the heavy work and just clean it up afterwards and glass it. I’ve done that too.
A total no brainer as long as you have a file and the right blank.
Saves allot of time and mess.
Up to you
my brother and I are just a couple of garage freaks having fun playing.
for us its not a business or something to make money from.
making our own stuff made us respect how hard it is to master it like the pros have
you have to put in the time to get really good at anything
I scored 3 blocks of 2 lb EPS from a construction company once. The were 6" x 48" x 8’ and I paid only $20 each. One block was slightly shorter than 8’. I chose to use a saw and cut rocker slices. Even with 4" thick slices I was able to get 5 boards from each block, so each blank was about $5. I was using balsa wood for stringers back then, but eventually started making stringerless boards. This taught me a lot about shaping and using cheap electric planers, various home made sanding blocks, surforms, cheese graters, and other non standard tools. Other than switching to a surfboard planer, I still use all those tools including a variety of graters.
I also went through a period of learning what glues work and don’t work. White glue, like elmers or the stuff kids use in school or even good wood glue doesn’t do well for EPS or XPS. Gorilla Glue or similar foaming glues are the best.
I just started a board using 1" and 1.5" EPS from Home Depot. It was left over from another project and will be covered in balsa or other wood for a stronger shell. I’m currently using Elmer’s Glue because it’s a lot cheaper than Gorilla Glue.
Amen.
This is a fantastically cut hot wire cut job here JRandy.
Thanks Chris!
One thing that caught me my last cutting session this weekend is the blank ends. The templates need to be a bit longer, like 2" (5cm) each end to account for the ‘hysteresis’ or delay in the curve of the wire by hand. I made templates with cute little 1" (2.5cm) ‘shelves’, which I replaced on the fly with 2-3" (5-8cm) scrap strips and hot melt glue ran at a tangent to the curve in process.
Hi JRandy
Can you confirm something about the foam.
So you buy plain insulation polystyrene EPS foam from a foam or building company in sheets of a certain thickness (my options are 100mm, 125mm, 150mm) in a certain grade (density) of foam (my options are what the foam company refers to as Medium in 18 kg/M3 or Hard in 24 kg/M3).
How does it go sanding and making the rails and contours on the bottom. Is it easy to work with. Do you use a EPS foam sealer before glassing. How is its bonding with the glassing/fibreglass. Are you using what I would define as: ‘high quality epoxy resin’ or ‘specific surfboard epoxy resin’ or ‘just any epoxy resin you can find’.
Are you then inputting your own wooden stringer: I have found a very nice marine grade plywood to source.
How heavy are you glassing.
Regards
@Chris4
I have bought EPS in densities 0.88PCF (14kg/m^3 ‘soft’ ) and 1.5PCF (24kg/m^3 ‘hard’ ).
The lighter one was an approx 150mm sheet, the heavier one was a large block 0.7 x 1.2 x 3+ meters (2x4x12 feet).
The heavier foam was easier to shape and sand and more resistant to dents in the shaping bay, which sometimes can be steamed out with a clothes iron and a damp rag.
I have never done a PU blank so I cannot compare to that. Some folks use an even heavier 2PCF foam and the ‘fused’ varieties should afford less bead tearout.
I used lightweight spackle before glassing. I don’t think (it’s been a few years) I liked the one that I added extra acrylic via floor polish to the spackle.
I have added stringers, have yet to try marine ply. I now have access to a nice bandsaw with a resaw blade so I may go old-school on the next one.
Here is my last ‘build’ thread (2015, has it been that long?) with glassing notes on the last page:
I would lean towards surf-specific epoxy to get the viscosity and brighteners and reasonable flip times. My last Ebay batch of epoxy had a three day flip time (hard enough to sand) where surf blends are measured in hours not days. Better materials do make a difference, including glass cloth and sandpaper.
Don’t consider my advice to be the end-all, there are way more experienced people here that have taught me most of what I know.
