Glass ons

I have no clue how to glass on fins. My last 4 boards the fins have looked like crap and there are cracks around the fins and they are about to fall off. Here is how i did it. Take a buch of fin rope soak it is resin then wrape it aroudn the base. It looked like crap and it doesn’t work. I just saw a picture so i think thsi is how you are supposed to do it. Take fin rope (have no idea how much) wrap it around the base of the fin. Then you take a sheet of cloth and put it over the whole fin and make it nice and smooth aroudn the base. Of course the rope and cloth are wet with resin.

Thanks for the help

Don’t wrap around fin, just lay it on each side of, then two layers of 6oz that goes all the way up the fin, and about 6" into each side of the bottom of the board.

Unwind the rope first. Normally, it’s 6 strands, 3 for each side of a twin or tri side fin.

I like using all 6 for single fins bigger than 8", so need two full pieces of rope, app. 7" long, one on each side of the fin.

The more you do, the neater the install, until one day, you only have to trim with a razor, and slightly sand with 120 for a nice smooth finish.

Yes, you have to sand the two layers on each side of the fin, then gloss it with the gloss coat, if you’re good at glossing, or independent of gloss coat, if you’re not.

And you do this all in one process or do you wait for the fin rope to dry and then put the glass over the fin.

I do it in one process, but I wait for cure on the two layers of 6oz on each side of the fin before razoring the leading edge and trailing edge rope, then wait for complete cure before hotcoating. Neatness counts major in this process, and the more you do, the neater it gets.

Of course, the fin gets tacked down beforehand, so it doesn’t shift around on you.

3 strands does not seem like enough. Are you talking about the rope where it comes in a yard and there are a bunch of little stands and you take 6 little strands out of it.


After you unwind the fiberglass rope, you’ll be left with 6 semi separate strands, 3 for each side of a twin or tri fin setup.

For single fins longer than say…7", you need all 6 strands on each side of the fin.

If you’re really neat, two layers of 6 oz covering the strands, up the entire fin, and lapping 6" onto the board bottom is minimum. More is better, and can compromise the tail bottom shape.

For glass ons, and to account for rail laps, I always sanded a bevel along the entire rail, tip to tail, then sanded out a little extra foam on each side of the tail bottom, to account for THREE layers of glass, resin, and rope from glass-ons.

get the “Essential Surfing” book… photos will help a lot. the way i learned (when doing thrusters) was to do one fin at a time, doing all three at once is crazy when you are new… set EVERYTHING (scissors, squeege, rope, precut cloth, brush etc.) out before you start in neat stacks. i even make sure my glass is pointing the right direction so when i pick it up (use a sticky gloved finger in the middle near the top, never touch the edge or it will fray) i don’t have to try to spin it or adjust it). i usually tape a bunch of news paper over the bottome of the board about 6" infront of the fins and lay everything out there. the newspaper keeps the drips from my gloves from getting on the board… the less resin you get on the less you have to squeege/sand off…

i use 7 stands form a 24oz sheet for rope for thruster sets, more for twins and singles. first soak the rope and then ring it through your hand a few times, then lay the presoaked rope, on one side of the fin starting about 1’ infront of the fin, cut with scissors about 1" behind the fin , lay on the other side of fin again about 1" infront to 1" behind, cut off the knot that you tied to keep the rope together. then put on your 6oz precut sheets.

make a templet and cut all your 6oz side sheets the same, i attached a photo of a fin with an orange line around it, the orange line is roughly the shape of my templet. when you lay the templet on your 6oz cloth make sure it is 45 degrees to the grid of the cloth, this way the cloth is stratchable when are putting it on (when i learned this i was shocked at how much it helped)

hotcoat the bottom and after cured flip the board and hotcoat the fins with fins pointing down…

there are so many tricks even if you read them all you still simply need to do it a bunch and get your own system.

try using uvcure resin, it is nice to have a lot of time to get everything all nice and clean.

fixing broken fins is a geat way to practice…i attached a photo of a rin repair, bofore sanding to give you an idea of what your shooting for…

i would bet there is tons on this in the archives.

good luck.

oh yah, another trick i use is to put 3 or 4 disposable gloves on each hand. that way when a glove get too messy you just pull it off…

The other posts seem to have it covered in words. If you want a visual explanation, try Glassing 101. I thought that was pretty comprehensive. If I remember correctly, I think they may lay a couple of cloth panels over the fins. I only used one and that was fine.

Howzit Spaz, Use UV resin,that way you have plenty of time . Setting fins with UV is really easy. Aloha, kokua

Thank you so much for all of these tips. Now i wont be scared to use glass ons anymore. Do you happen to have anymore pics of putting them on.

thanks again