Posted: Dec 18, 2008 - 11:00 AM
I've had this same problem on a couple of my boats and I would recommend that you take this opp to learn a little fiberglass repair. It's not hard to do and the several sources of material and information will generally provide you with the technical information you need. As stated above, this is more of a cosmetic repair than a structural integrity risk and with some attention to detail, can be accomplished easily in several hours (total).
Materials can be procured from any decent marine supply store (as well as auto parts storse and home improvement, e.g., Home Depot, Lowe's etc.) The marine stores are more likely to have a better color match to your hull; however, the better auto parts stores also carry a good variety of pigments to color the resin.
Obviously, follow the directions provided for the system you choose--I've used the West System and many others and find them all to be similarly handled. Most consist of a two-part (resin & hardener) mix and some type of patching material, either woven fiberglass cloth, fiberglass mat (sheets of random fibers), all in various weights.
Your basic procedure would consist of cleaning and removing the loose pieces of broken fiberglass/resin and the surrounding surfaces. Acetone (main ingredient of nail polish remover) is v. useful here. Can be bought in quantity in home improvement stores & paint stores. USE in WELL VENTILATED AREA ONLY! Use two pairs of latex gloves (one over the other) for the work--this will aid cleanup!
Next, prepare the repair site. If what you describe is the down-curved portion of the rear of the deck, you can prepare a 'dam' by using painter's tape (blue masking tape from home improvement/paint store) to create an undersurface. Remember, the resin will be liquid and will drip & run until it begins to set. Once you have created a form/dam, make a small pile of fiberglass threads by un-weaving the cloth, shredding the random mat, etc. You will actually use two to three times as much as you think you will need. For a 50-cent piece hole in the curved edge of an H16 hull above the rudder gudgeon, I would probably shred glass until I have a full handful. Also, for the curved edge, it would be useful to have an additional piece of cloth two times the size of the total repair to place on top of the glassed in filled area.
Prepare and apply the resin in accordance with the directions included with the resin system you choose. Mix the resin (after hardener has been mixed) with the shredded fiberglass and pack into the repair area. Cover and smooth with the 'top cloth' and let set up.
You can use almost any model handheld power sander on the finish work, once the resin has set up. I have made 'hot batches' of resin and successfully sanded these to finish quality in as little as four hours after initial repair; however, tinkering with the 'mix' does require experience. For a first time, stick with the directions included with the system you use.
Sand, using gradually finer grades of oxide paper, until you've worked the surface to near original quality--this is where a good eye and touch help the most. The easiest part of fiberglass repair is the fact that you can easily re-work the repaired area, if you don't like the results. When you are satisfied with the surface finish of the repaired area (note the color will not likely match), then you are ready for the color-matched gel coat.
On this part, you don't need fiberglass, just the resin mixture. Mix in the color pigment to match your hull color, apply in accordance with instructions. Let set, sand (v. fine), polish. Re-drill the hole for the rudder pin (you could apply a small amount of resin to the inside of the hole to seal it); however, if your original repair was extensive, i.e., completly replaced the area, not merely the surface, additional sealant is probably overkill. Replace rudder systems and sail away.
In all, an easy fix on a weekend with decent weather and you will have learned something about the construction of the boat you sail.
Caveat: Nothing I've suggested above should contradict any included instructions and nothing should counter applied common sense and safe practices. Fiberglass repair sounds difficult; however, I started building my own surfboards before Hobie Alter built his first catamaran (he does have me beat on the surfboard thing though) and nothing is inherently hard. Careful adherence to system instructions, care with surface preparation and thorough finish work should provide you with a quality patch virtually indistinguishable from the original.