Tech talk: Small ding repairs, in both carbon and glass boards


Welcome to this Appletree Surfboards tutorial video, for carbon and glass board repairs.

Can I fix small dings in carbon and glass boards by myself?

We believe that everyone should be able to repair small dings in both carbon and glass boards, from flight damage, to impacts with the rocks or when you accidentally drop your board on the parking lot. Larger damages, like broken fin boxes or crushed tails or noses are also not too hard, but they will be too complicated for the experienced, so it’s best to ask the assistance of a professional. We might make another video on this in the future!

Our foam is 100% waterproof

In general Appletree boards are really strong, and they do not damage easily. Also remember that our foam is 100% waterproof, so even bigger damages do not need immediate fixing when they are not structural.

Do you want to know more about our 50k waterproof foam and how it’s different from foam in other boards out there? Check out our tech talk: Waterproof foam via the link below.


Is it difficult to repair my kite surf board or foil board?

The process we are showing here is quite easy. It is perfect for filling non structural cracks and small holes that do not require adding carbon or fiberglass. It works equally well for both carbon and glass board repairs. If in doubt about your damage always ask a professional.

What do I need for my carbon and glass board repairs

It only requires the following:

  • Epoxy resin, preferably for surfboards, so it is not yellow tinted, but any will do
  • Micro balloons for thickening
  • Black pigment, in case of carbon repair
  • Mixing cups
  • Painters tape
  • Plastic foil
  • Sand paper, 100, 180, 320, 400
  • Optionally some matte clear coat

How do I know if my board requires a repair?

This board has damage as if it hit the rocks, it has two damages next to each other. They look similar, but in the one on the left, the glass has actually cracked. You can feel the crack with your nail. The one on the left looks bad, but our boards are really strong, and this is only optically. As long as the spot is not soft it does not require a repair. But we can make it look a bit better, so we will do them both.

Make the hole bigger than it was

To start with the real damage. Take a strong and sharp knife and carefully start removing all of the loose bits of fiberglass. You will always need to make the hole bigger than it was. To make sure the repair has enough to hold on to, and to be sure that you got the entire damage filled. As you can see here, I remove quite a bit, and I also dig a bit of a hole in the foam, also to give the epoxy something to hold on to. Make sure that you remove a bit of foam wider than the opening in the glass, this will help the repair to stay in place and properly seal.

After you are sure you have removed all the loose bits, blow away all the dust and give the whole thing a good sand with rough paper. Also sand the inside and around the repair, but don’t go too far around the repair as this sandpaper leaves nasty scratches. The repair next to it does not require any knife work, just a rough sand with some 60 or 100 grit will do.

Tutorial video how to repair your carbon or glass kite surf board

Is fixing a carbon board more difficult than fixing a glass board?

Carbon and glass board repairs are about the same. In this case someone dropped something heavy on the carbon board. It might have been me with a hammer, but we will never know. Anyway there is a nasty hole that needs fixing. This is on the larger side of the spectrum, and it almost needs reinforcement, but our laminate is very strong, so even this can be fixed without using carbon.

Again, remove all the loose bits, in this case this whole patch. Dig out some foam, sand the edges and around the hole so it’s nice and rough.

Then for the fun part. Take some plastic film. I use LDPE plastic foil here, but you can use any film, as long as it’s not clingfilm, that is too weak. Packaging plastic from a random item usually works, I have even done this with packaging from cookies. It does help when it’s transparent, but even that is not necessary.

Cut a square of plastic, about 2-3 times the size of the hole, and it’s easiest if two sides are straight(ish). Now put some tape on the edge like so: and stick it to one side of the hole. Same for the carbon board.

How to mix epoxy

It’s now time to mix your two part epoxy. We always do this by weight as it is more accurate. Every epoxy system has a different ratio, so make sure to check your epoxy. Always make sure you have enough, you can mix a second batch, but that is double work. In this case I made about 20 grams which is more than I will need.

When the epoxy is mixed well, add the micro balloons. This stuff is ultralight filler, which will make your epoxy thicker, so it stays in the hole and also much easier to sand. So do use it if you can. It comes as standard in most repair kits you can get at your local surf shop.

Start with about the same volume as your epoxy. Mix slowly as the stuff flies everywhere and you also risk whisking in air which will create bubbles later which you then need to fill again. This should give you this yoghurt like thickness. I like it a bit thicker, so I add another spoon full. Now for the carbon version, I add some black pigment. This helps hiding the repair in a carbon board. But it doesn’t do much else.

Fill the cracks with epoxy

Back to the board. Smear in the epoxy. Make sure to get it into all the cracks and under the laminate first. Then fill the hole completely. Same for the black stuff in the carbon board. Fill it so there is slightly more epoxy than you eventually need. Epoxy will slowly sink into the hole and it also shrinks a bit when hardening. When the hole is filled like this: grab the edge of your plastic foil and pull it tightly over the repair and stick in place with the tape. The neater you do this now, the easier the sanding will be. If you make a mistake, or trap air, just remove and do it again. This is where the clear foil comes in handy, you can see what you are doing. Depending on the epoxy and the temperature, the curing time varies. Just take at least 24 hours, to be sure the epoxy is hard.

Repeat the process if there is still a small dent

It is now the next day. Time to remove the foil. Carefully sand away all the access epoxy mix. Slowly sand back to the original shape, constantly checking that you do not sand the board too much. Same for the carbon repair. As you can see, with the glass board there is still a small dent. So it will need another fill to make it really neat. Or you can leave it, up to you, we will give it another fill.

Unfortunately in the carbon board, there are two air bubbles, I did warn myself… so this also needs another fill. So, mix another small batch of epoxy, same as before. Add a small drop in the hole, and this time I will just cover it directly with tape like so. This works fine for small holes like this.

Now we wait another 24 hrs…..

Last step: Sand the board back to the original shape

So here we are again the next day. The epoxy is cured, and it’s time to finish the repair. Remove the tape. As you can see, everything is properly filled. Now just slowly sand the whole thing back to the original shape. When you get close to the final shape, go down in sand paper to avoid scratching 400 or 600 grit is usually where we stop. Keep feeling all the time this is the best way to feel if you have sanded everything, and if the shape is correct. I am happy with this result, so I will leave it like this. As this glass board is a bit older and it has already yellowed out a bit, the repair is more white than the surrounding board, but I’m fine with that. If you have a colored board, you can try to color match the repair, but that is quite hard.

In case of the carbon, the black is fine for me. We could have used some white, but we are going for a functional repair here. As a final option, you can spray the area with some matte clear coat. This will fill in the last scratches and make the repair less visible, but it’s totally optional.

So there you have it. Quick and easy simple tips, for both carbon and glass board repairs. These boards are ready to go again, and repairs like this should easily hold and they are plenty strong! Hope this helps you to take your first steps in repairing your own boards! It’s a very useful skill and it helps to keep your boards in tip top condition, ready for the next session.

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