Read the archives and best of swaylocks but still have a couple questoins about glassing on fins and the sanding process
How much cloth extends onto the board? When the football shape is described, does than mean half the football goes on board the other half covering the fin?
After fin is glassed on you have 2 extra layers of cloth around fin that is higher than rest of lammed board. WHat is the proper way to sand or blend this cloth? Do you just grind it down on the edges similar to the rail lap? Or do you sand everything to obtain a smooth surface through fin area?
I first tape 'em upright and tack them on with a little UV lam (witha little cut cloth fiber in there to make a “mush”)
remove the tape once the tack has set.
Lay the rope dry (I take apart some scrap cloth)
Cut two pieces 6 ounce that run all the way up the fin, and onto the board about 3 inches. I don’t cut “footballs” this to me is the wrong shape. Most of the time when a fin cracks or rips out, it’s the front corner of the fin that starts the action. So my cloth is wide there. I take the cloth all the way up, because it’s a humbug to sand 'em smooth if the glass only goes partway. The speed of UV cure, though, means I can do a baste coat before a hot coat, with hardly any downtime, so I may go that way. The added weight I don’t consider to be significant.
I wet the rope using a brush, then immediately lay the cloth (one piece at a time) and wet that with the brush too. Yeah, my job will be resin-rich, but I’m into strength. I hate having to re-set a fin that’s been broken off.
After the fin glass is dry, I hot coat the entire bottom. Sand to blend and make a fair, smooth finish.
NOTE… my last finish coat didn’t want to smooth over where the glass was exposed by my sanding. There ended up being a lot of little “pinholes” there, probably something to do with static electricity and surface tension. I know the foam is sealed, so I’m not concerned, but I had it all smooth and for it not to finish off nicely was a bit of a disappointment. The rest of the bottom finish coat was quite smooth. What this shoudl mean for anyone else, is to watch out for those pinholes in areas where the glass is exposed by the hot coat sanding.
The only thing I could add to that is one easy addition.
When you lay out your cloth, lay it on plastic, then pour some of your resin, and continue with wetting the rovings. The resin will soak in, a quick squeegee to pull out obvious excess, then peel it up and lay it on your fin. The wet layup will stick where you want it, and joins to itself around the extremities well, making for a neat trim once gelled.
I’m sure Honolulu would concur that his method sees very few weak point fin jobs. And Honolulu, if you get into doing it this way, you could find another layer of cloth on your fin layups with no extra weight.
Glue the fins down with either a mix of lam resin & cabocil, or use a hot glue gun if you are in a hurry. Then prep your glass and fin rope. Cut the glass about one inch bigger around the fins (two pieces per side), and two at the base. It does not have to be pretty, but it is easier if it is rounded off. Next, tie a knot at the top of your fiberglass rope you are going to use for your fins. Now mix your resin. Wet out your fin rope and lay it in the fin base. Cut the rope at the back of the fin with some sharp scissors so you have wet rope on both sides of the fin. Now you can wet out your cloth cutouts. You need two per each side of the fin. Lay it in there. Lay down the other side. Press it all together and try to remove the bubbles at the base. When the glass firms up and is kinda past the gummy stage, cut the shape with a razor blade. If you wait until it hardens too far, you have to grind it off, which is not fun. Hot coat and sand as usual. If you suck at sanding, shoot some hotcoat over the fin area, then do your hotcoat after that sets up.
Now you know how the clear look is at the front and trailing edge of a glassed on fin like you see at a regular surf shop.