Picture of Fix a Very Broken Surf Board
Graft it back together and fiberglass it invulnerably strong. This project is good preparation for making a board from scratch.

This repair method uses epoxy resin and microballoon putty. Instead of epoxy you could use polyester resin or vinyl ester resin, with minor changes dictated by the resin instructions. Remember that unlike epoxy, those other resins dissolve styrofoam. This board is urethane foam so it doesn't matter.

Stuff you'll need:
Broken surfboard
Epoxy resin and the directions to not screw it up.
Fiberglass cloth. I have 8 oz and 4 oz.
Tyvek bunny suit to keep fiberglass dust off your skin.
safety glasses, dust mask, gloves for ditto.
Angle grinder, sanding disk, backing pad.
assorted other abrasive spinning devices, sanding blocks, sandpaper

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Step 1: Scrape off the Wax

Picture of Scrape off the Wax
If there's any wax on the deck, scrape it down to the deck with a serrated glue applicator.
You can also use a "comb" which is a similar wax texturing tool sold in surfing stores for this purpose.
Then use the straight edge of the glue applicator or any sharpened-credit-card type tool to scrape off as much wax as you can.

Non-surfers may wonder why people wax their boards, and why it looks like it was waxed with candle drippings, not like an ad for floor shine products. The purpose of sufboard wax is to provide a non-slip surface for the feet. So rougher is better.

The wax also gets sand stuck to it. If you surf bare-chested your abraded flesh will get embedded in the wax and your nipples will bleed. You'll realize why "a shirt worn while surfing" is called a "rash guard".

Step 2: Heat Gun and Rag to Remove More Wax

Picture of Heat Gun and Rag to Remove More Wax
Use a heat gun and clean rag to remove more wax. You'll see the wax sheet out in front of the heat gun when it melts. You can feel when most of the wax is gone, because the rag will slide much more easily over the board.
Then soak a new clean rag with isopropyl alcohol and rub down the board to remove any remaining traces of wax. Wax would prevent the new fiberglass from sticking properly

hi, there's a few things I'd do differently,

what I've noticed is that a broken stringer inside a glassed over break will eventually cause delamination and another break down the line.

the vibration from riding and flexing the board during bottom turns causes the broken joint to open up and forces the new glass skin to separate from the foam.

so before mating the two halves together I'd reinforce the break in the stringer by splinting the break with more hardwood. sawing the foam away from the stringer at least 5 inches up the break on both sides, and also wherever any other stress fractures may be hiding.

Grain running longwise, the splint need only be 1/16 thick hardwood sandwich glued with resin into the spaces made by the saw blade.

This also insures the two halves are lined up pretty close and tight.

Trim the excess flush to the deck and bottom and than fill the break with the microball mix, taping one side over the wet bond line and flipping over to fill in all the empty spaces of the break.

I hope that will help save a favorite board you just cant throw away...
I was just curious if you think you could have gained anything by adding a couple pencil rods through the core at the break? Like aluminum or something. I don't think it would add too much weight...but not sure about balance/tilt.
What do you think?
louis.m3 years ago
You write "up to about 100 degrees".

A hundred degrees what, Celsius , Fahrenheit, Réaumur, Rankine or Kelvin ?

Frankly, I guess you mean Celsius or Fahrenheit (which is still quite a difference), for something as global as a web page, it would be useful if you mention the unit.

bendog383 years ago
How exactly DID you break your board like that??? I've found it very hard to break ANYTHING like that.
juicymoose3 years ago
Very helpful saw a guy who snapped his board in two on the atlantic coast, would have saved him a few euros
boingx4 years ago
Interesting how different skills often come together. In sewing, binding tape (cloth used to edge material) is made by cutting the material at 45 degrees so that it will lie flat when attached on a curve.
Wade Tarzia4 years ago
How ell does epoxy stick to a formerly glassed area? I was told that in such cases the new or next layer of glass "is just along for the ride"  because the new epoxy cannot chemically bond with the long-ago-cured glass and epoxy.  But I guess that leaves the mechanical attachment of new epoxy on the scratched up old surface?  Is that what holds the repair together entirely?
Mechanical bond is mainly what holds it together. Foam and gless also IMHO has mechanical bond. Epoxy fills pores and that does the trick.
nonce4 years ago
Good insight but, this is how i see proper way of fixing boards
toad4 years ago
Very good instructions, although I would have glued small strips of wood to either side of the stringer for strenth. But then I would have made a horrible mess of the fiberglass and most likely glued myself to the board.
milesp4 years ago
 I'd also consider routing in a bit of ply along each side of  the stinger to add strength. Also, don't breath on micro balloons whilst mixing - nasty stuff in the lungs!

TimAnderson (author) 4 years ago
that holds the fiberglass cloth tight and smooth against the rails (edges) of the board. If you don't do that it can hang straight down.
articice4 years ago
what's the blue tape for?
katmckee5 years ago

Great Shirt!

TimAnderson (author)  katmckee5 years ago
Thanks! I should have worn the bunny suit. But I was thinking. "I've got a good crosswind, and I'll just sand it a little". Next thing I looked like I'd been in a snowstorm and felt like I'd rolled in cactus. I had a sore throat and was blowing my nose all night. After that I suited up before any sanding.
george675 years ago
Thank you including mistakes and misadventures.  I often have as many eureka moments with them as I do the good tip and advice you provide.  I'm sure documenting them is not as fun as showing total victory so I'd also like to applaud the fortitude you show by doing so.
I do composite repair everyday in an FAA repairstaion, and have since 1992. This is a well written instructable.

My one observation would be to use a fiberglass epoxy putty mix instead of the micro-balloons. Micro-balloons save you some weight, but they are better used for filling in irregular holes, like impacts. They do a good job of rolling into all the nooks and crannies. They don't impart much strength, and if you make the mix either too thin or too thick you loose effectiveness.

You can cut up fiberglass cloth, on the bias of the weave, to make the equivalent of milled glass fibers. They won't be as finely milled or as small as a purchased milled glass, but they add a lot of strength to the repair.

Also, when using any type of putty mix, be it milled glass fibers, micro-balloons, or aero-cil (cabo-cil) be aware that the putty will generate it's own heat and "kick off" quicker than the normal pot life of the resin by itself. On a large patch, it can cause the patch to bulge or de-laminate from the surface you are bonding to, or the individual plies from each other.

I have, on occasion, used a variation on your curing oven. For small fairings that it would not be cost effective to fire up the large commercial ovens we use, I have used a cardboard box large enough to hold the part and a cheap blow dryer. Place the part on a stand, I use mixing cups, place the box over the part, make a flap on a bottom corner of the box, large enough to accommodate the nozzle of a  cheap blow dryer. Make another similar sized flap at a top corner of the box for air to flow out of the box. Plug in your blow dryer, I usually use a low setting. Make sure your box is at least 3-4 inches bigger than your part. Using the flaps, you can open or close them to achieve a nice temp in the box to cure parts.

Most of the resins we use have a pot life of 40 minute and a cure time of 4 hours to 24 hours at room temperature. Using this impromptu oven, once the resin has passed the working time, even the 24 hour cure time can be cut to a few hours.
TimAnderson (author)  underwhelmed5 years ago
Thanks for the great tips! If I'd known/thought of it I definitely would have thrown some chopped glass into the putty mix, especially in the middle where the stringer was broken.
your dog5 years ago
what happened!?
I just had this cool idea, a surfboard closet shelf.