if there are major soft spots in the foam or glass, you will have to sand away all of the shoddy stuff until you get to a point where the glass and foam are strong and well bonded. this is difficult for people (emotionally) because it involves making the ding bigger before finally getting to the point where you can do a good, solid repair. don't worry: you can fix it. but first, you have to get rid of all the bad stuff... brown foam, cracked glass, any place on the surfboard that you can "squish" by pressing into the glass... all this crap needs to be gone.
this is a repair of another repair gone wrong. the initial repair didn't get all the old foam and delaminated fiberglass out of the way, and eventually the nose of this board went bad.
at this stage, where everything is sanded away, you can start to build a tape wall around the part that you want to rebuild. once you have a tape wall up, you can fill in the old repair with a mixture of resin and microspheres, also knows as "Q-cell" which will take the place of foam and give you a solid mass that you can then re-shape.
this is a birds-eye view of the tape wall, or tape dam. you want to build it up high enough to hold in all the goo that you are going to put on the damaged places. remember, you want it at least as high and as wide as the rest of the rail shape. bigger is better. you will re-shape this after it hardens.
after the resin "kicks" you can pull off the tape dam and then wait for it to harden a bit more. once it is hard, you can sand it down to the original shape of the board.
the next step will be glassing.... or for people who really like their original aesthetics intact, you can either paint the repair now with acrylic paints, or else tint the glass. but before you glass, you want to sand down the area around your repair so your glass will sit flush with the rest of the board once its all done. then, tape off the area, remembering to leave about 1 inch or so around the repair so that the new glass you are about to lay down can overlap onto the board and make a nice strong repair. rails should get at least 2 layers of glass. decks should have 2 layers as well, and bottoms can probably get away with 1 layer, if the repair isn't too big.
...... coming next at the nye beach center for discovery ...... glassing and sanding....
.....the final stages! you can do it!