Uhmmm- put it this way, what a surf shop would charge for labor is a big piece of what you'd pay for the tools to do it, and there really ain't that many. Here's your tools and materials list
Scissors - not real good ones, the plastic-and-stainless ones are good enough
Throwaway 1" chip brushes, the ones with natural bristles
Sanding resin- maybe 8 ounces/half a pint.
6 oz. fiberglass cloth
Fin rope
Paper cups
Stir sticks, the wood ones
Random orbital sander with discs ( this is optional, look locally for a used one from Porter Cable or Milwaukee or Bosch. You don't want the palm grip, hold-in-one-hand type)
80 grit sandpaper
Wet sandpaper, several grits.
Utility knife or X-Acto knife with new blades.
Vinyl gloves, the cheap ones from the hardware store
Masking tape
Okay, here's what you do -
Carefully sand the loose and cracked cloth away. Take your time. A random orbital sander will make it easier, but you can do it by hand, it takes longer but if you're not familiar with power tools, this prolly isn't the place to learn from scratch.
And no, I don't consider a Dremel to be a power tool, it's only a hobby thing for doing eensy weensy little things, not ding repairs. Neither are the sandpaper disc setups that Uncle Fred used to put in a drill. Uncontrollable, with those things you wind up doing more damage than you fix. But I digress.....
Once you have the cracked and obviously loose stuff deal with, that's when you go with the rope . Like SammyA said, you can make your own, from 10 oz cloth or woven roving scraps.
Now, here's a trick. Use maybe one crystal or so of instant coffee stirred into your sanding resin, most of a cup of it. It's a brown tint and not much more, not unlike instant coffee . Don't catalyse the whole thing, just use a little in another cup, catalyse that lightly and stir well, and with your vinyl gloves on put the fibers in place alongside the fin base, brushing a little resin into 'em until they are translucent, clear.
I say catalyse lightly 'cos that gives you more time to work with it. If the stuff goes off too soon, you have a nightmare to sand away and it's really no fun at all. I say put the tint to a cup full of uncatalysed resin ( cover it between steps) so you don't wind up with four different tints for every step.
Kinda gently mold the fin rope-resin glob with your gloved fingertip so it's concave. That will save you a lot of sanding later. When the resin goes to a gummy, gelatinous stage, that's the time to get any stray drops and blobs up, they should peel off nicely.
Okay, sand the hardened glob ...when it's hardened. Use the 80 grit, make it a smooth transition between the vertical fin and the horizontal bottom. That's its function, you see, to make what's ttechnically called a 'fillet' between 'em that looks good. No lumps, no lines, just smooth.
Now, wasn't that fun? Good, now for the next step. Take your scissors and cut some 6 oz cloth that are more or less the same size as the fin plus an inch or two to lap down onto the bottom. Same scissors, cut the bristles shorter on one of your brushes, to maybe 1" long. Catalyse some more resin, brush a little onto the surface you're gonna glass, set cloth on there, brush more onto it, set your next layer, more resin until the cloth is clear but the weave still shows. Leave it at that, let the resin dry some, until it's nostly hardened,
Now take your x-acto knife, the Really Sharp one and cut the cloth away that sticks past the outline of the fin. Okay, wait until it's as hardened as it's gonna get, sand the edges of your cloth so there's a nice smooth transition.
Right, mask around where you sanded the transitions on the bottom and with your last throwaway brush, brush some catalysed resin onto your new cloth and the spots right adjacent to it. You're looking to fill the weave of the cloth and blend your transitions, no more. I'd go a little stronger with the catalyst, so it will harden before it sags away.
When that has hardened, break out the wet sandpaper and sand it nice and smooth, maybe go to 400 grit. It won't be perfectly polished, but then again, this isn't a museum restoration or a new board, it's your first ding repair and you're gonna use the board, right?
Okay, have at it. And I need to have my coffee and get the old brain going.
hope that's of use
doc...