1) Clean the immediate and surrounding area with Acetone solvent.
2) Roughen the surface with 80 grit sandpaper only where it will be repaired
3) Mask off with plastic all around the repair area, don’t be stingy....a little more plastic and masking tape here can save a lot of clean up later.
4) Precut multiple layers of appropriate cloth (two 4 oz pieces for surfboards) one piece with about a ½” margin larger than the hole, second layer 1” larger than the hole.
5) Fill any deep indention with foam of same type, or skim with resin and glass bubble paste if indention is 3/16” or less deep.
6) With the ding filled with either foam sanded to shape, or Resin/Glass bubbles (while still wet), put a thin coat of resin on the repair area.
7) Wet out both pieces of 4 oz cloth patches on a separate flat surface covered in plastic.
8) Remove the cloth patches from wet-out table and position over the ding, using the smaller one first and covering that one with the larger.
9) Cover the complete area of the repair with plastic sheeting….can even be saran wrap.
10) Take a large auto body plastic squeegee and work all excess resin out of the cloth and onto the adjoining plastic masking….when everything looks optimum spider out from the edges of the top covering sheet of plastic with masking tape to stretch it out smooth without wrinkles.
11) When it has fully cured the plastic will pull right off and you will have a perfectly smooth surface that conforms to whatever compound curves exist.
12) The excess resin will have been pulled onto the adjoining plastic away from the repair area. I like to use the blue masking tape and take a Dual action sander starting with 120 grit paper to feather the exact edge of the repair…the masking blue masking tape is easy to see, and makes knowing just how far to take it down a no brainer.
13) After you have feathered it down on all sides pull up the perimeter masking which takes with it all excess resin.
14) At this time you can lightly sand it and put on a gloss coat…or gel coat if it’s a cat.
A catamaran repair is no different other than using more layers of 4 oz or 6 oz cloth, increasing the overlap of the repair slightly, and adding a coat of gelcoat. I did the bow of a friend’s Hobie 20 several years ago and by using the factory matched gelcoat you could not tell which hull had been damaged in a collision and which hull was untouched.
When everything is listed like this it sounds like a big production…but it really is “stupid simple” and gives a much stronger and cleaner repair. It also avoids damage to the surrounding laminate that often occurs as people try to sand down a high profile lump of resin and cloth.