Why have I not seen 3 lb. eps blanks?

I know it sounds like a step backwards but hear me out.

I’m not questioning the benefits of eps/epoxy construction. But what I’ve wondered for a couple years is this:

My understanding is that the Clark superblue blanks were in the ballpark of 3lb/cu. ft density. So why, in the last few years since the pro-epoxy movement really started getting momentum (which was actually pre-Clark shutdown), have I never seen 3 lb. density eps blanks?

Wouldn’t this have helped avoid so many of the issues encountered in getting the traditional establishment to try new tech? You know, all the complaints you hear - you gotta seal it, too corky, too stiff - wouldn’t they be greatly minimised by starting with a more apples to apples approach, ie: 3lb core and 4 or 6 oz. glassing? Theoretically, once folks got comfortable working with and riding the different materials, then they might more interested in exploring the new avenues possible thanks to the enhanced physical traits in a lighter cored sandwich.

Hope I don’t sound too glib or flippant, because I’m asking this in all sincerity. Is there something I’m missing?

Personally I dont see any benefit in using High density EPS over the same density PU.

It is very expensive and the weight savings are minimal .Compression strength is about the same and you lose the ‘memory’ of the lighter grades of EPS.

Of course these are just my findings with the limited experience I’ve had with the high density EPS.

Good point. If it’s too similar then I suppose you haven’t gained anything, apart from perhaps some recyclable scrap. But if the boards break just as easily then you’re still just adding to the landfill.

I have a lots of them. They make wonderful big wave guns/sup’s and tow boards. I think they are super strong and they shape like butter with a drum or bladed planer. The cnc’s come out perfect. Unlike the 1-2lb eps range, no need to spackle if you are into that, because they come out perfect. I bought up a guys supply of 2.5 and 3lb foam he got from the mainlaind because they can’t make it here in Hawaii. when I got the bill I have to admit I almost sheeet myself because it was about 3 times the price I expected.

I believe Marko foam has 2.5 and 3lb available that is way less expensive than what I paid for mine. It certainly has its place in board making, but most peeps want strong and light and cheap. All my guns are 3lb foam

Segway has 3lb EPS. Apparently 3lb is the highest density Ken can manufacture.

It is my understanding that EPS has better mechanical properties than PU. A 2lb EPS vs a 3lb PU glassed the same will perform very similar. Thus people have made boards with lower density EPS blanks and the same glass schedules they were using on PU → more float/corkiness. I havent done a 3lb EPS board but I would bet it would be stiff as hell, thus why it lends itself well to guns/towins etc…

just my bs theory… someone please correct me if i am way off the mark

Appreciate the responses.

OTAY - out of curiosity, how much difference in “feel” is there compared to a comparably-shaped and glassed PU board?

On the surface, it seems like it should feel pretty similar.

I love epoxy and only surf PU/PE boards when swapping boards during a session. I love stiff and floaty with guns. I still think the 3lb is lighter, crisper and quicker flex and more floatation than a similarly dimmed pu/pe equivalent. Also think the over kill on pe resin and cloth schedule on guns is not necessary with 3lb eps. Just do a 6 bottom and 6/4 top and epoxy resin and you are set. I have 1/4" wood stringers in the guns also.

If you just could have one big wave gun, it probably wouldn’t matter which you use. Big waves and good conditions you will use anything to get the job done.

I want to make it clear that I don’t mfg the EPS foam. I purchase block from a number of vendors, and the blocks are 4’ X 4’ and up tom 24 ft long. I use mostly 16 ft blocks. The foam is made in density’s from 1 lb (.9 lb) to 3 lb (2.8 lb) foam. EPS has a specification which allows for +/- 10%. In order to make the 3 lb foam, the process requires more plastic beads as well as a much longer cycle time for the steam. The amount of pressure placed on the hydrolic moulds gets to be a problem, so most EPS mfg’s will only make up to 2 lb (1.8 lb) foam because of the stress on the equipment. Peolple talk about higher density’s than 3 lb, but I have yet to see any. I’m not aware of anyone that makes higher than 3 lb…

As for the blanks…I can make ANY size blank from ANY of the foam density’s as long as it is no longer than 21 ft no thicker than 50 inches, and no wider than 50 inches. That should cover most surfboards, paddleboards and small boats!

Most of the 3 lb stuff I cut is for Guns…


I was in EPS molding for 13 yrs. (Foam Fab, Compton for you Ken!) and

when you get into the 3 lb. range you are entering a range of densitys where

the aspect of molding the material becomes the problem, not the cost. In

block form, it is really hard to get the fusion (bead to bead meld) in the center

of the block at that density in the large blocks. It is also difficult in smaller

shapes as well, and requires long cycle times to fuse and then cool the material

with a satisfactory part produced. In molded blanks a la Marko, it must be

understood that the middle of the blank is around 3" thick while the ends are

1/2" thick or less. this means that the inside of the center of the board will not

be fused at all if the ends are not collapsed from over-fusing, especially when

the densities increase. There is a time/cost per cycle that is figured into the

price of any custom molded product as well as rejects (I have never seen a “second”

Marko blank) that would put higher densities out of the comparable price range

in competition with pu/pe. Without pricing the cost of a blank in current dollars,

I would think that, based on my experience, that anything in the 3 lb. + range to

duplicate the old pu weights would be too expensive for the limited market.

Hope this helps, I could go on… LOL

Now that’s what I’m talkin about - a seriously informative answer from guys who know. Thanks Ken and surfteach. Personally, I wouldn’t mind if you did go on, as I find the background info on foam manufacturing really interesting. But I think the initial question has been pretty well answered.

Thank you all.

Like Airframe - from my experience with cutting and shaping some 3lb eps i have found it to be pretty expensive. The bead structure seems to change a bit when you get above 2.5, there are alot more hard spots then you would normally have (but that all depends on the manufacturer) and the beads are a good bit more solid - in that the foam does not need to be sealed when shaped. The 3lb slab resembles more of a molded eps, like you said, because of the pressure needed to make it, and the beads do not flake but rather dust off which is pretty cool.

Main problem = the stuff does not move, unless you are in tight with a guy who makes quite a few LBs and uses the 3lb it ends up not being worth the extra $ and time needed to make.

Best use I have found for the extra that I can inevitably never sell is to make some dual density blanks 1.5 or 2 and 3lb

i have been using 3lb. in making wakesurf board for the last year , easy to work with and i get my blanks cnc shaped by a friend for low cost , now all my shapes have flat bottoms but nose and tail rocker are cnc. all cores are 1" thick and i have been using 2x6oz. S cloth on top and bottom. all boards are vac bagged with dryfinish like COIL and now only hotcoating the bottom and rails to keep the board light

Hey that is pretty cool. I have experimented with 3lb and lighter doing skimboards and only a handful off wake surfboards - all with hand lamination and never had any real problem with too much flex or breaking, even at 2lb doing triple 4oz on both sides they come out really light.

Are you putting any stringers in those wakesurfs?

I was always hesitant about trying to get those things vac’d because I dont like putting stringers in them, and it is not a dyvincell core - heard too many horror stories of the things snapping in the bag even on a rocker table. I am just hotwiring and then handshaping them, it would be alot of effort wasted on my part to have the 1/2" foam get contorted during glassing. Just curious.

No stringers ,. i use 3 pound with 2x6oz. s glass on both sides then hotcoat and sand smooth , boards weigh from 4 to 5 lb. and no boards are longer then 5.6. seems everyone is using 2 pound on the wakesurfs. i use 3 lb. so i wont have to use a stringer with no problems. ALL my blacks are CNC hotwired and their is no need for a rocker table for me when i vac bag , for 3lb eps i use 10" of vac and no more. you can see some of my blanks on my site



Sweet, looks like you are pumping some pretty sweet boards. Ever try the Dyvinicell cores? Ive seen it up to 5lb+

See you at the expo later in the month!

some folks tried it for rails , like a parabolic stringer board , it costs too much for me and i like getting my blanks cnc cut were all i have to do is use a router for the rails and boxes then staight to lam coat

from what know…marco foam makes 3lb foam from what i know they will make anything you need… but it,s price…check out marco foam.com

my latest board was done with 4/6 oz on both sides and did not get any dents on the deck , the board is 3lb eps .4.8x20x1.125 and rides fast with the twin fin and c-5 box set up. weight with traction less fins is 4.5 lb.

Reviewing this thread of late last year, I agree…Surfteach gives an insightful discourse about how producing (or attempting to) 3 lb. EPS has its inherent challenges and IMO a point of diminishing return.

It may be well enough to say let the two different approaches to making surfboard blanks stand on their individual merits. The virign 2 lb. EPS that I have been using recently nets an extremely strong performance board using a 6/4 glassing schedule on both top and bottom. The material shapes well and the reduced hull weight allows you to focus the strength into the skin. Using a double layered top and bottom with ALL layers lapped onto the rails produces an extremely durable product for the consumer in a lightweight category.

I recently have spent time with White Hot Foam discussing different aspects of their specially produced “Surf Specific” EPS. This is EPS foam that undergoes a separate curing that they developed in their Arizona plant. White Hot is a subsidiary of a much larger company that supplies the housing industry, and the EPS that they produce for architectural features such as columns, baseboard, crown mouldings, and SIP’s, are an entirely different formulation of EPS similar to what some of us used throughout the 80’s on sailboards and some surfboards. A primary supplier of that particular EPS was secured, for the most part, from Western Insulfoam.

Regardless of who produces it, the difference with “virgin” EPS is that you are not geting recycled material. Some people might feel there is nothing too complex about developing and producing quality Expandable Polystyrene, but nothing could be further from the truth. There are also many misconceptions surrounding EPS as a material and it is noteworthy when informed individuals like SurfTeach, Greg Loehr, Mike Daniels, Otay, and others chime in with insights of their experiences with the material and its evolution of a period now spanning decades.

The age old complaint I hear from surfers that do not like the ride is the difference in bouyancy that is inherent to the material itself. I would guesstimate that the 1.0 or 1.5 lb. “styrofoam” (trade name originated by Dow in, or around, the 50’s) floated about 62 lbs. per cubic ft. back then. I don’t know what he calculation would be now or how or if it significantly differs with today’s improvements to ‘superfusing’ the material thru the use of IDRO/EDRO or other proprietary methods.

White Hot decided to stay with the large billet/bun production after researching results of smaller individual molds similar to what Marko is using. Each to their own on that matter. White Hot’s “SS” true 2 lb. foam has a noticeably crisper feel to the EPS beads due to a secondary curing process they developed for surf blanks. I also have two 2.5 lb. foam blanks from them that I am glassing with two different glassing configurations while weighing them at every juncture along the way to being finished. This is something I did with a Mowses Ice Nine blank last year. I originally began doing this back in the 1980’s while using the method to determine where and how much weight was added in production of high performance custom sailboards. It is a real eye opener to say the least.

The point I want to make here toward the possiblity of using higher density EPS (in this case, 2.5 lb.) is that the complaint from some surfboard manufacturers is that EPS requires sealing, use of epoxy, and the added cost of yardage in that EPS blanks are assumed to require double layers of fiberglass on the bottom as well as the top. With the use of higher density EPS, this may not be the case.The generally accepted approach toglassing EPS is subject to review with the development of newer epoxies exhibiting improved qualities from what we were familiar with in the 80’s…and as to the feel of the end product, good designers can use as yet disclosed methods to tweak the ride in a multitude of ways.( I’m staying mum on my own current R&D…).

No doubt people have their individual preferences and agendas for whatever reason. The point is, there are attributes from each core material that is currently in use, and IMHO, it is pointless for one to begin mimicking the other…

Ahhgh, dangit Bruce.

I finally, belatedly, hotwired my first 2 lb. blank just hours ago, and now you wanna tease me with secret glassing techniques? You’re killin me here.

FWIW, I’m making a 5’8" stringerless quad fish to zip around my Gulf Coast mush on. I’m all ears if you feel like making any suggestions via PM.

(I’m allowed to briefly hijack my own thread, right?)

Seriously though, thanks for your comments. I hope you’ll post results.