One Quick Glass-On Fin Question...Please Assist :)

Aloha all…

I just had one question relating to glassing on a fin. I read the archives and understand the basics, but I just have one basic question.

When glassing in the fin, do the glass patches have to totally overlap the whole fin? (I’m glassing in two marine ply fins on a fish) Do you just make some glass patches that will run up onto the sides of the fin, or should the patch be bigger than the whole fin to bond with the oversized piece on the other side? I don’t want to add too much more glass/weight, and was hoping to just put 2 pieces of glass on either side that just run up onto the sides of the fin, and not totally cover the whole thing. Is it just personal preference? Can someone clarify this for me?

Also…should I put a reinforcement glass patch under the fin, or does it really make a difference. There is 6oz on the bottom of this board. (I know its another question…but I couldn’t help myself)

Mahalo…

Josh

I personally prefer to layup the full fin. It’s stronger and easier to sand.

If you’re worried about weight, layup the two pieces of cloth, or three four ounce is better, on plastic or something. Squeegee all the excess off, peel it up and put it in place and smooth out.

With wood fins you might want to do a sealer coat of resin beforehand.

Try what you’re comfortable with. I found it easier, stronger and better all round.

Oh yeah…by the way…fin is already glassed with 2 layers of 6oz on both sides. So getting glass coverage on the fin shouldn’t be an issue. Thanks again.

Josh

Cut your cloth on a bias, so that the weave is at a 45 angle to the fin base. Cover the whole surface of the fin both sides with the cloth. The bias layup is almost twice as strong as a " normal" layup with cloth strands running both parallel and at a 90 to the fin base. I’ve been doing that since 1960. Went to all cloth glass on, no rope, and never had a fin break or even crack. That was one of my little “secrets” that I didn’t share with anyone back then. I don’t think I’d bother with a patch under the fin, unlessyou just want to do extra work. or it makes you feel better.

keeping it clean is a big part of doing fins… use a 2" brush to wet out the cloth, use as little resin as possible and squeege the cloth when your done… i would start with one fin at a time, way less stress…

cut you cloth large then the fins and then razor off the excess after it is partially cured…

i usually then hotcoat the bottom of the board including around the fins, let cure then fins down, hotcoat the fins…

they don’t HAVE to go all the way up the fin (especially if you’ve already glassed the fin) but the amount of weight you’ll save is negligible, and the fin will look nicer and sand easier with the glass being all the way up, rather than partway.

For what it’s worth, I did some fish fins the way you are thinking once, and wouldn’t do it again.

Another nugget of information. My question is this. The fin patch that you see on many longboards, this is done before the fin is glassed on? I thought that it was after the fin was on. What is Its purpose? Is it just more for looks nowa days or does it still have function?

No fin rope? Is two peices of 6oz on each side still enough for a 9.5 with a long base?

LB fin patches: if it’s an oval-shaped piece, they’re called “footballs” and it’s actually the glass from the sides of the fin laying (neatly cut/trimmed) on the bottom.

OTOH, if it’s a large section of the tail, that’s a separate piece of cloth. It’s unnecessary, adds weight and is only (IMNSHO) for looks.

duckdive,

Yikes! NO, two 6oz pieces only are not enough for any fin. To use glass only, start with 2 layers full coverage on the fin, and extending out onto the board (football shape) for approx. 4". Then 2 layers halfway up the fin, and extending onto the board approx. 1/2" less than first layers. Then another 2 layers 1/3rd the way up the fin, same setback on the bottom extension as before. Then 4 layers 2" up the fin, and 2" onto the board. Hotcoat and sand. You’ll only be sanding into the cloth weave at the ends of the layers. (no loss of strength) The MOST important part is that the cloth be cut so that the weave is on a bias in relation to the base of the fin. The above glass schedule is equal to the schedule I used of 7 layers of 8.5oz cloth. Be sure to tack your fin in place first with lam resin. You don’t want to be fighting a floppy fin, while trying to manage all that pre cut cloth.

Bill,

Thanks. Here is where i am at already. I used 6 groups of fin rope on each side. Then i put on one peice of 10 oz and one piece of 6 oz covering the whole fin and all the way to the rail on the deck. So based off you previous post you would say about 4 -6 more peices of 6 on each side. I was trying to avoid putting the glass only part way up the fin. I will be hand sanding the board and the uneven fi cloth will add on quite a bit more work. Thanks for any more help