With the demise of ClarkFoam there has been a lot of talk of import blanks from China/Australia/Brazil. However, they all seem to be made out of different materials. Can anyone provide clarity on the materials, their uses, etc.
For example, Spyder foam is supposed to be designed for surfboards. It is a polystyrene that has a regular cell structure that runs vertically to help give it compression strength from someone standing on it and doing a bottom turn. It weighs 2.3lb (NOT 3.2 as reported elsewhere). It is expensive now, but would probably drop in price if there was a sudden demand. XPS weighs 2.0 (in the Blue variety). It does not have the aligned cell structure, and is therefore more suceptible to compression damage, but is less expensive. EPS is (I thought) the weakest of the bunch and has a cell structure that is open enough to allow water to absorb. Polyurethane is toxic, cheap and is supposed to have the weak structure of EPS. It is also going to be increasingly difficult to find because of the environmental risks. (PS I don’t think having to get your board from half way across the world because a totalitarian Chineese government is willing to poison its people in order to earn a few yuan is a reasonable solution for me.)
OK, so that’s what I know about foam, but what I want to know is how this applies to surfboards. I hear from some people that XPS requires epoxy rather than polyester glassing. Is that true? Is that why people use only PU from Clark Foam? If I am an amateur that only makes a couple of boards should I avoid XPS because I would have to learn a new way to glass? Likewise, why don’t people use Spyder foam, it was supposedly designed for sufboards. It doesn’t seem logical that PU would resist compression better, or resist absorbtion of water. Does it too require special glassing or shaping techniques? What about EPS? Do you have to shape it or glass it differently than PU?
In short, if your goal was to change as little as possible the way you do things after years of using ClarkFoam PU, are these other foams possible alternatives; and if not, why not?
Almost all of your questions can be answered in the archives.
If you want to change the way you do things as little as possible, don’t change anything. There will be PU foam blanks soon to replace Clark, and you probably won’t even know the difference.
The “PS” in EPS and XPS stands for polystyrene, which dissolves when put in contact with the styrene in polyester resins, so you have to use epoxy, or coat the foam with a barrier substance first that won’t allow the polyester resin to come in contact with the EPS or XPS foam.
Spyder foam is a type of XPS foam. There are two different types of Spyder foam, also known at Dow as “Surfboard foam”. The white is between 2.1lb and 2.4lb, and the blue is between 2.9lb and 3.3lb. And the Dow blue insulation XPS is between 1.7lb and 2lb.
XPS insulation foam is cheap, and Spyder foam is expensive. There are some issues with XPS use that have been discussed in the archives. Spyder foam doesn’t seem to have the same issues due to the chemistry being slightly different.
Glassing with epoxy is no different than glassing with polyester resin. But if you don’t want to try epoxy, you can’t use EPS, XPS, or Spyder. But if you do, the XPS and Spyder foams are really nice to shape.
I know a lot of information is in the archives, but it is amazing how hard it is to get a full answer. Most of the discussions assume too much or make blanket statements like “Spyder foam is crap”. No where in the archives did I find the simple answer that you gave: PS melts in polyester. Makes great sense. Also, I hadn’t found anything in the archives that pulls all the different materials together. Maybe a discussion of the different foam types could be pinned. That didn’t used to be an issue since we all used Clarkfoam, but now it seems like it would be.
Spyder foam still seems intreguing. I had thought that it had been dropped in the 80’s because of cost, not performance. It still resists compression better than 60lb blue XPS and has better lateral load strength. It has to be light since it is the material of choice for gliders and model airplanes. Anyone have actual knowledge of its use and why it didn’t take off?
Since many of the people stepping up to the void left behind by Clark are using XPS/EPS foam, I’ll look into what is involved in using epoxy instead of polyester.
I think the main reason not too many have tried the Spyder foam is the cost. A 4’x8’x5" block is $90. From what I have been told, mostly windsurfboards are being made from it.
On the other hand, there’s a lot of us experimenting with the regular XPS foam. Some are having delam problems and some are not. I personally haven’t had any problems yet.
I have tried Spyder foam. I used a little bit of it in the nose & tail blocks of a gray d-cell sandwiched board.
It was not easy to shape. Normally, high-density foam is a good candidate for surforms, but the surform seemed to rub the cells of the foam back & forth & rough it up. Kind of like tearout, without the tearing out bit. The hand plane was even worse. I think the connected cell structure you’re talking about (I didn’t know anything about that) made it worse for shaping. I ended up doing this bit with a belt sander. You can see I dug too far on the front one of the 2 bands on the left & had to fill that area with cabosil before glassing.
It also did not cut clean You can see the chunking along the back seam with the d-cell) and it sucked as much epoxy as the d-cell too. I will not be using it again.
EPS has the best strength to weight ratio of all foams, is easy to work with and is widely available everywhere.
XPS has a history of failure, i.e. delamination and heat realated issues.
Urethane foam from overseas will be expensive and inconsistant in quality and supply. Clark was a brilliant man who dedicated his life to urethanes and it took till 1995 before he really got it down. Consider what you will be buying from overseas. Some will be good, some will be junk. It will be a crap shoot.
If your a homebuilder then these issues may not apply to you. But if your basing a production on any of these choose carefully. Your future will depend on it.
If your a homebuilder then these issues may not apply to you. But if your basing a production on any of these choose carefully. Your future will depend on it.
Greg your 100% right on this one. Even if the rumors (rampant as they are) of the last six months or so of Clark foam coming from some factory in the orient and that coming back sometime soon. I would not want to depend on something like that any longer. The way of the path has been unveiled, some will take it others will try other things, some will pray for things as they were, but never will be again. In the words of John Millius in his movie, “Red Dawn.” Things are different now." Why not simply try and improve on and support whats now readily available.
Thanks!!! There is no substitute for actual experience.
I have a good, local (to So Cal) and inexpensive source of EPS and XPS. I may be able to convince them to make a mold or two for surfboards, if they think there is a market. The dominance of PU seems to be so overwhelming that I doubt they will make EPS boards, though. Walker Foam will bring 1000 blanks a week from China. If only the EPS market was even half that.
I don’t want to use Chineese PU. I would rather not have some farmers thrown off their land or fishing villages poisoned just so some party leader can have a factory. I will try some 2.0 EPS and hope that the rest of the market goes that way. It would be great to have a good EPS supplier out there, but as long as people are fixated on PU I guess that won’t happen soon.
One other thought, does anyone have actual information on what the big boys are going to do? Is there any indication that Rusty or Al Merrick will adopt EPS, or will they be just ordering blanks from China?
