surfboard is too soft. WHAT DO I DO?

Alright so hear me out Swaylock… SO I’m current in the process of building an insulation sheet surfboard. I just added the gloss coat and was ready to sand and finish her up until I noticed something… The board seemed way SOFTER than a typical board. I put pressure on the board in various places and noticed that I could put a pressure dent in it relatively easily. Now it’s not like the thing is a sponge but it definitely should not be this soft. Upon research and investigation, I realized something that I should’ve taken into account when I was fiberglassing the board, the foam I used is less dense than your typical eps surfboard blank foam. I am beyond frustrated with myself… So now I guess I have to sand back down to the fiberglass and add another coat which will add some time to the building process. So I ask you guys are there any shortcuts/recommendations that you would give me? What kind of sander should I use (Currently using a palm sander and an orbital sander)? How much more fiber glass should I add to the board (I already have two 6oz on the top and one 6oz on the bottom)? Is there any way that I can sand down a little bit but not until the glass and then add some fiberglass, or should I spend the time and sand until the glass?

I have already invested hours upon hours into this project, and I want to make sure the board will turn out sound so IF YOU COULD OFFER ME ANY ADVICE AND HELP ME OUT that would be greatly appreciated. Thank you.

Fiberglass alone isn’t going vto do it. You would do better adding a wood or corecell skin to the deck

I would just surf it and start planning your next board with needed improvements.  It’s all part of the fun. Mike

add a few 6oz patches to the pressure areas and forget about cosmetics. and ride it.


I’m with Yorky on this one. 6oz patches and surf it. 

Insulation foam.


Not too sure if you’re better off riding the board and a not worrying about it falling a part, or spending the time and money to make it stronger.

I’ve used insulation foam from the local hardware stores. I think the EPS foam from Lowes is much lighter than 1lb, maybe 1/2 lb and Home Depot is getting probably 3/4 lb or a best 1 lb EPS. This calculation is based on buying 1 lb, 1.5 lb and 2 lb foam EPS surfboard blanks from the local EPS manufacturer. They supply Home Depot with the EPS block foam. This is not the same stuff that Marko or some of the other surfboard blank manufacturers make. Marko blanks are good.

With anything less than 1 lb, you’ll need a hard external skin, and probably vacuum bag lamination. We use 1/8 inch thick balsa wood for sandwich skins and we use 2 layers of 4oz glass, a layer under the wood and one over the wood. That seems to work, but the soft foam will end up with delaminated skins after hard use in a couple of years. It does make a really light and fairly strong board, but not something that will last a really long time.

I’ve done 3 layers of 6 oz on 2 lb EPS and still have a lot of pressure dents. Currently using 3 layers of 6oz or 2 layers of 6 and one layer of 8 oz for the deck on 1 lb EPS. 3 layers of 6 oz and I have lots of denting on the deck. I will either use one layer of 8 oz on the bottom or 2 layers of 6 oz.

The biggest problem you may have is if you have a stringer. The area next to the stringer will crease then delaminate and probably tear along the stringer. This is because the foam is giving way but the wood is not. If you don’t have a stringer, you could be in for worse. The board may buckle from flexing. I usually have 5 layers of glass on the rails for the stringerless boards, to help make them stiffer.  

Insulation foam from the hardware store can end up being more of a hassle than it’s worth, but if you do compsands with wood skins, it can be a cheap source of foam. When I started buying the insulation foam in bulk, I could make a blank for about $5.00 US, but the manufacturers caught on and raised the prices quite a bit. 

Just came across this and wanted to see if anyone has had success with 1lb eps without a wood skin. I’m in the planning stages of my next build off of some salvaged dock foam. Not that I can’t vac bag a veneer on it, it’s just that investing time and money into vacuum bagging supplies sort of defeats the purpose of a recycled surfboard where the goal is to do it for cheap. I was thinking of using a stringer and 3x4oz deck and 2x4oz bottom but sharkcountry’s comment about delams next to the stringer has me worried. I’m not really concerned about pressure dents and actually like it once my boards get broken in a bit with some heel marks. 

So what should I do? Anyone have any success stories with using just glass over a 1lb core? I realize there are ways to glass skins to a board without a vac bag. Where do you guys source your veneers anyway? Internet or local supplier and what type of added cost is this usually? And what about the rails? How hard is it to get the skin to wrap around a curve such as that? I know most compsands are stringerless but has anyone done one with a stringer? The thing that worries me the most in all of boardbuilding is delams so I want to make sure I take all precautions to ensure I don’t get any. 

Thanks guys, this forum has been an amazing resource for me.


This board is 1lb or less recycled EPS cooler foam. I think I have 3 layers of glass on the deck, and it may be a combination of 8 oz and 4 oz. One of those layers is an inlay. 2 layers of glass on the bottom done in 2 single layer lams.

I think the glue lines being perpendicular to the stringer (thin plywood) helped it from bad pressure dents, but there are pressure dents. I’ve ridden this board hard and have surfed places where I’d do maybe 2 or 3 feet air drops.

The one area I notice that gets the worse dents on most of my EPS boards is where I sit. We can have long lulls and sit for up to a half hour.

with light foam you can go without stringer and had more glass on the deck and rails+deck patch. delam appears  from localise buckling. dents help to initate buckling as overall stiffness. stringer increase overall overall stiffness that increase overall buckling strengh but for local buckling it’s skin stiffness that’s play. so you need some stiffness to your skin, and less stiff is foam more stiff need to be skin. a stiff skin by itself increase overall stiffness so need less stringer. this is how compsand works: stiff shell on light foam. by weight a compsand can be by far breaking and denting strengh superior but for that it need really stiff skin end it feel really stiff, hard, like old surftech, more they soften skins better they surf but less strong.

So on 1lb stringer less foam, 2x6bottom 3x6 top, all layers around rails plus a deck patch with fiber at 45° between layers on deck. Seal foam with resin slurry first.

Yes, guys have done just glass over 1 lb EPS, but if I recall correctly they generally found it took triple 6-oz on the deck / double 6-oz bottom to not feel squishy.  By the time you’ve done that, the weight ends up the same or more than PU/PE and you’ve spent a bunch of time, money, and effort overbuilding a crappy core (no offense intended).

Triple 4 oz deck / double 4 oz bottom is what I use on stringerless 2-lb EPS and it feels good.  This is just my 2 cents.  Best wishes.

Yes I am sure all the glue lines helped quite a bit.

I lb EPS just isn’t suitable for Surfboards.  Precisely the reason people like Marko sell 1.5 , 1.9 and 2 lb.

“…building an insulation sheet surfboard…”

There’s your problem

Not an issue of having access to decent blanks, I was just hoping to do a recycling job like Skatement has been doing recently. I glued up some dock foam from a dock that was destroyed in hurricane Florence and was about to be hauled to the landfill. I was able to secure a vac pump so I’ll be attempting a compsand this December. I’ll do a build thread on it. Thanks for all the advice, you guys rock!

This is a link to the last board I made recycling EPS foam. Pretty sure it is 1lb. I added a 1/32" thick layer of Balsa over the area I thought would need the extra support becuase this one has a 1/2" thick stringer. Without a stringer, I’d be less concerned. I used 1/32" only because I had it. I normally use 1/16" or 1/8" thick sheets. 1/8" and you are building something solid. 1/16" willlet you bend around the curves easier, and 1/32" will bend around the rails with no problems. I don’t think you need to do that, just cover the area where you’ll be standing and sitting. Don’t leave a straight line across the board. I’ve staggered the wood for less waste, but now I make angle cuts (for looks only).

You can get thin balsa sheets at various retailers that specialize in wood for RC models. This company seems to have good prices.

If you just do a deck layer, you can use weight, like sand bags and then tape down the edges. I also use the shrink wrap you can get at the hardware store. UncleD did this.



This board was made from 4’ x 4’ x 13" blocks of EPS. I think it is about 1lb, and was originally pieces of floating docks. I made 3 boards with one block and I still have 2 blocks waiting to be used. All the boards I made are stringerless and just glassed. All the layers of glass are lapped around the rail for strength. I think I used a combination of 8 oz and 4 oz glass, or 6 oz and 4 oz. Deck would be no more than 1 - 6 oz and 2 - 4oz. I added balsa wood to re-enforce the fin box. I also have an angle in the middle where the front and back pieces of foam meet. The deck shows denting but the board is very light.

I rode this board during hurricane Hector in pretty intense surf, probably double overhead at the biggest, but very thick. I took a couple of poundings in barrels I didn’t make. I was worried it might snap, but it didn’t.

Just want to add that these 1lb EPS boards are made to try different ideas. They are not meant to be long lived, and if the ideas I’m working on turn out to be good, I can make another one with the proper materials. This board was made to see how the rocker worked. It has been a great board for better waves. Overhead or bigger and it shines, fast waves, it shines. 7-2 x 22" x almost 3".