TECH TALK: How to repair small dings in both glass and carbon surfboards and foil boards?

Welcome to this Appletree Surfboards tutorial video (https://appletreesurfboards.com/carbo...)

We believe that everyone should be able to repair small dings, 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 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!

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.

What do I need for my repair
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.

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. 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.

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. 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. Now put some tape on the edge and stick it to one side of the hole. Same for the carbon board.

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.

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.

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.

So here we are again the next day. The epoxy is cured, and it’s time to finish the repair. Remove the tape. 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. 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.