how to fill the gap?


i just found this site a few days ago because i decided to start repairing some boards we have around. i was looking for an alternative to microballons and found the solution with the inside of menstruation pads - amazing.

i am new to surfing (about one year) and even more new to fixing them but manually able. last year i broke this cheap softboard (decathlon) and already tried to fix it once but that time i used polyester to glue the wood and pu-foam (the one in cans) to fill the gaps - didn’t last long. now we have epoxy around and i would like to give it another try cause it is nice for people to make their first approches to waves.

i am asking for help (ideas, approaches, keywords) also because english is not my mothertongue and i have a problem to find the right words to search for.

so here is the problem:

  • the board is almost in two halfs. underneath is a plastic layer that still keeps it together.

  • i cutted out the foam next to the wood to glue + screw supportwood left and right of the two stringers (tried with polyester - it came off)

  • there is quite a bit of the original polystyrol missing that has to be replaced/filled


and here are the questions:

  • could i mix epoxy and polystyrolballs (smashing one-use-cooling boxes i.e.) as a filler?

  • is 2 times 20cm woodsupport on each side enough?

  • can i glue polystyrol with epoxy?  the internet has different answers on that.


i have epoxy-resin from a surfshop aswell as glass of 4 and 6oz.

would be amazing to get some help, here are some pictures.



  Those boards are very inexpensive here in the U.S…  My first preference would be to simply replace it with another one.    If you’re getting into doing repairs then you could save this one for use as a donor.  You can salvage the finboxes and fins and the leash plug and use the foam for filling holes in other boards with EPS cores.  

If you’re not able to do that then here’s how I would fix it:

Everything looks wet in the picture.  If the board broke in out in the water then the foam in that blank will have sucked a lot of water in, like a sponge.   So the first step would be to dry everything out.  You can flip the board with the bottom facing up and cover it with a dark tarp and stick it out in the sun.  The dark tarp will attract a lot of heat and will help evaporate the water in the blank.    If it gets so hot in your area that delamination is a concern you can stick the board in a shed that warms up during the day and let it sweat it out more gradually.  This might take a couple weeks.   There’s no point in doing anything else with this board until everything dries out.   

Your next step would be to stabilize the stringers by fitting them together and screwing or gluing a piece of thin ply on either side of each stringer.  Once the stringers are dry then gluing with epoxy will work.    

Personally, I don’t use resin+filler for large repairs because  - in my opinion - that just creates a hard spot that doesn’t flex with the rest of the board and therefore leads to re-breaking the board there.   Plus it adds weight.  

Instead, I would cut more of the foam out of your repair area and scavenge some dry foam from another broken/discarded donor.  Or use offcuts from a shaper who is shaping EPS blanks.  Cut foam plugs out of that foam to graft into your blank and then glue those in.  You want to cut these panels so they meet on the sides but are oversized relative to the rest of the deck. 

After the glue sets up you can sand the grafted plug down so its even with the rest of the foam and proceed to seal all exposed areas with a light layer of epoxy+filler slurry. You’re only using enough to seal everything and to provide a good surface for bonding with the rest of the repair.   Let that set up and sand it, then glass over with a layer of fiberglass to make it water tight.  

Then after your repair areas are watertight you can scavenge some more of the deck material from your donor board and glue that over your repair area.  You might also consider cutting a deckpad out of that same decking material or other EVA traction pad material in order to cover the exposed seams of your repair area.   

wow. thank you very much for the detailed reply.

yep, these boards are cheap but i have time and are keen on working with new materials. the board was standing outside and is quite wet. i opened everything up to let it dry properly, will take a few weeks i guess.

2 questions appear while reading your explanations:

  • do you really put a layer of fiberglass + epoxy between the foam and the deck? as i see it on the board, originally there is none. and is this only to make it waterproof?

  • i don’t have a donor board but eps should be easy to find. could i use camping matress to replace the deckpad, wikipedia says its pe or eva?

thanks again for the helpful input.


Anytime I’m working with EPS I will go to lengths to keep water out of it.  I don’t care if it’s a hassle or if I’m doing extra work.  I only want to work on that fix once.  So I seal my EPS repairs.   

As for your deck, I think finding a material and an adhesive that will bond with your existing shell will be the thing.   Even better if you can get some deck traction out of it so your riders don’t have to screw around with wax.     I have no experience working with the EVA they use for soft top boards so I don’t know exactly what will and won’t stick to it.  I’m sure there are others here who do know, though.   

I have not tried this myself but feel free to give it a try.  First, make sure everything is at least fairly dry.  Second, squirt some Gorilla Glue or other moisture activated foaming polyurethane glue (Roo Glue?) in the crack and spray a bit of water on it.  It will foam up and eventually cure pretty hard.  Scrape/cut/shape/sand it flush and scuff an area around the repair to prep the skin for next step.  Trim some durable fabric like Cordura to fit over repair and glue it down with 3M 5200.  I honestly don’t know the tensile strength of cordura but it should be comparable to, if not superior to the stuff they coat those boards with.  The 3M 5200 generally hold like mad to most anything…  should be good enough for most beginners.

PS - 3M 5200 takes a long time to dry… several days anyway unless you add accelerator.

Set it against a wall with the broken ends on the floor.  Let it drain for a few days or until there is no water puddling or draining.  On a table or saw horses attempt to align the two pieces to the original rocker.  Once you know you can do that without any problems, pull it apart and apply a mix of Epoxy and Cabosil or Qcell to glue the two pieces back together aligning the rocker.  Use Saran Wrap or plastic packing wrap to hold it in place if necessary.  Once it has set you will need to rout each side of the stringers so that a piece of 1/4" wooden insert on each side 6–12" long can be installed.  I use five gal. paint sticks. Fill all voids with a thickened mixture of Qcell/Epoxy.   Laminate a piece of 6oz or 6 and then 4.  Use EPOXY resin only.  Do a filler/hotcoat and sand.  Spray can a taped off panel around top and bottom .  Simplest fix.