Cracks in gelcoat

Stress cracks are a common occurance and are not an indication of structural failure. What they do mean is that the fiberglass flexed more than the gelcoat is able to bend without cracking. Fiberglass composites can and do flex more than gelcoat (brittle) without any adverse effect on the composites strength or longevity. Most boat manufactures try to reinforce areas that are prone to flexing to prevent the gelcoat cracks from occuring. However, they cannot cover all possibilities without making the boat needlessly heavy.

So, do not worry about the cracks this year as no harm will be done. If you want to fix them, you must grind away the gelcoat down to the fiberglass composite and "paint" in new gelcoat, then sand down flush with the surrounding gelcoat then polish. Sand starting with 120, 220, 320, 400, 600, polish. Some people go past 600, but I find it unecessary. Make sure your sanding area grows with each successive grit of paper.

A dremel tool is a good means of grinding out the crack. The groove or removed material does not need to be wide, just down to fiberglass (1/8" wide groove is plenty). If you just cover up the crack, it will reappear almost immediately.

The hardest part of making an invisible patch is matching the gelcoat color. Color kits are available, but hard to get a good match. The easiest way is to order the gelcoat through a CC dealer for your particular boat and color scheme. The problem is that 1 gallon is the minimum order and a gallon of custom gelcoat color will cost you about $180.00 from a CC dealer.

Kenny, Can you be more specific on what to use? I have the same problem and would like to take care of it with-in the next 2 weeks before I put the boat in the dock.

Kenny:

If you do not believe me, that is fine. It is an acceptable practice and NOT my advice, but the advice found in many books covering fiberglass repair. I am in the process of repairing a severly damage boat and have done extensive research and purchased several books and videos on the subject. I trust the authors who have been repairing fiberglass boats for many years. I am just passing along what I have read and practiced, not what I dreamed up.

I will clear up one thing. If the source of the stress is not corrected, then yes the cracks will reappear. If the stress was one unusual event, then no they will not reappear.

I am curious why you think replacing gelcoat with gelcoat is a bad idea. Remember, I said grind through the gelcoat to the fiberglass. I did NOT say grind into the fiberglass and replace fiberglass/resin with gelcoat. Help me learn something new if you know I am wrong, just do not say I am wrong...why?

grind em out.! put glass back in.
a chopper gun job cost $$$ but u have a beautiful boat paul !
crazing/gelcoat cracks as david said are somewhat different from stress cracks,however the repair process is the same.
paint the front door of your house every year for 20 years.what happens? the paint cracks!
why ? it's too thick ! spray gelcoat too thick in a mold and after a while we have cracks in the finish.gelcoat was never designed to be a filler but a hard durable finish.fiberglass makes a much better filler.

Kenny:

I would love to send you a photo of one of my repairs and you will see I am qualified to make the comments I make. I am having to patch holes punched through the composite, replace the bow that was crushed. Replace the port side bow at the upper deck to hull seam due to being crushed. My method is to cut out crushed areas, grind away all delaminated composite material, lay up new composite of equal thickness as original on a 12:1 taper to original undamage material, fair out with epoxy resin mixed with a thickening a sanding "powder", spray gelcoat, sand, polish. If you look close, you can see the gelcoat blend line, but you have to look close. I will try to post a before and after picture, if I can figure out how.

Good question? there the same to me.

that repair looks good david,and i'm sure your bow repair will turn out just as well.
for someone who took the time to gather books,video's and fiberglass repair information thats great!
however,i know from years of hands on experence making a living at it that gelcoat is not used as a filler in cracks regardless of what the auther of the book claims.

Here is what I started with...