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Old 17-04-2024, 07:39   #31
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Re: Fiberglass spider cracks

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Originally Posted by s/v Jedi View Post
I have seen these cracks before incl. aboard our own boat. They are primarily caused by gelcoat that is completely deteriorated from UV exposure.

Secondary problem is that the gelcoat was applied much too thick, think 5x the manufacturer stated maximum thickness, especially in corners where it quickly accumulates during spraying the gelcoat into a mold.

The thick layer of gelcoat is much more brittle than a more flexible fiberglass laminate underneath, meaning that these cracks will probably -not- continue in the underlying laminate.

I have tried wet sanding this gelcoat first with 320 grit then all the way up to 2000 grit followed by polishing. You get what almost feels and looks like good gelcoat. Almost. Within a year or so you see it deteriorate quickly again.

I find the best approach is to sand it away as far as possible without touching the laminate. Use a sander with dust extraction and 60 grit paper.

After that it is time to throw some money at the problem. Start with a coat of Awlgrip Hullguard to seal the laminate. Then fair where needed (AwlFair or TotalFair), sand and add two thin layers of Awlgrip 545 primer, the first layer gray and the second layer white (assuming a white finish). These products can all be rolled and brushed but add thinner until you get a smooth layer, donít accept roller stipple in the primer as you would need to sand most away again.

After this you have a base that you can use any finish on but I would call it crazy to use anything but a two component polyurethane, like Awlgrip topcoat. Two layers. With a light color like white, when thinned enough, there is no need for tipping after rolling it on and the result will be like a spray job.

Remember to sand away the gelcoat. It is completely deteriorated and no good under a new paint system either.

Also, the hull will be stiffer after this, flexing less. The Hullguard rolled onto that 60 grit sanded substrate is an epoxy based product as is the 545 primer.

Hi, Jedi,
Yes.
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Old 17-04-2024, 07:42   #32
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Re: Fiberglass spider cracks

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FYI - Capt. Tolleys gets +1 from me. Worked well for very fine "seepage-cracks". I wouldn't be without it on a 52 year old boat. https://captaintolley.com/
Hi, M,
If the cracks weren't opened/grinded to the glass underneath, they'll come back sooner than later. You haven't really dealt with the issue . .. . just put a band aid on a larger problem.
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Old 17-04-2024, 14:10   #33
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Re: Fiberglass spider cracks

Hi Rognvald, thanks for the info. FYI - I intended only to make a comment about the usefulness of the product, in general. Although I'm not very superstitious I hesitate to say I've not the opportunity to get experience repairing leaky cracks in fiberglass. Not having that know-how I didn't mean to appear to endorse using only the product to correct the OP's issue, but see how my reply 'sounded'. Your advice is much appreciated.
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Old 18-04-2024, 05:46   #34
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Re: Fiberglass spider cracks

I know that my suggested fix is labor intensive but when you diy this is a permanent fix, giving much satisfaction when completed.

Believe me, I have tried quicker fixes, like grinding the cracks out, then filling with white MarineTex and sanding/polishing that. Besides the color difference, the gelcoat will keep deteriorating, creating a void around the MarineTex fix and at some point the MarineTex is standing proud of the gelcoat as that erodes further.

Quick fixes like that are okay if the gelcoat is not as old, say 10 years or less. Beyond that, itís simply not worth it.
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Old 18-04-2024, 05:52   #35
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Re: Fiberglass spider cracks

Another interesting exchange of differing opinions albeit facts in all. I'm glad to hear that other CDs have had the same problem, confirms mine is not a defect boat. Assuming they were all built with similar construction procedures supports the too thick gelcoat theory but I also believe that there is another underlying problem. The reason that supports that is, the cracks have at least doubled in number in the last year.
I am well aware that the only way to fix it is the long process of removing the entire gelcoat and applying a new coat but I purchased the boat to sail, not for a months long project, so I still intend to put the bandaid on it for now. Keep the water out and put some makeup on until I get to the age I can't sail, too soon now, then I'll start the project.
This has been such a productive discussion, I'm tempted to start another. Maybe about weather, definitely not politics. Thanks.
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Old 18-04-2024, 06:02   #36
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Re: Fiberglass spider cracks

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Originally Posted by Byrnerc View Post
Another interesting exchange of differing opinions albeit facts in all. I'm glad to hear that other CDs have had the same problem, confirms mine is not a defect boat. Assuming they were all built with similar construction procedures supports the too thick gelcoat theory but I also believe that there is another underlying problem. The reason that supports that is, the cracks have at least doubled in number in the last year.
I am well aware that the only way to fix it is the long process of removing the entire gelcoat and applying a new coat but I purchased the boat to sail, not for a months long project, so I still intend to put the bandaid on it for now. Keep the water out and put some makeup on until I get to the age I can't sail, too soon now, then I'll start the project.
This has been such a productive discussion, I'm tempted to start another. Maybe about weather, definitely not politics. Thanks.
You can actually do both simultaneously. Just bring a sander and materials wherever you go and work step by step. The use of two part products mean that it is cured after a couple of hours and the boat can be used as normal again.
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Old 18-04-2024, 06:18   #37
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Re: Fiberglass spider cracks

Quote:
Originally Posted by Byrnerc View Post
Another interesting exchange of differing opinions albeit facts in all. I'm glad to hear that other CDs have had the same problem, confirms mine is not a defect boat. Assuming they were all built with similar construction procedures supports the too thick gelcoat theory but I also believe that there is another underlying problem. The reason that supports that is, the cracks have at least doubled in number in the last year.
I am well aware that the only way to fix it is the long process of removing the entire gelcoat and applying a new coat but I purchased the boat to sail, not for a months long project, so I still intend to put the bandaid on it for now. Keep the water out and put some makeup on until I get to the age I can't sail, too soon now, then I'll start the project.
This has been such a productive discussion, I'm tempted to start another. Maybe about weather, definitely not politics. Thanks.
Hi, B,
Jedi gave some good advice about "spot repairs" which is exactly how I handle my fiberglass projects. Tying up your boat for a major repair doesn't make sense. And, if you get some gelcoat and a color additive(usually yellow and brown) for white gelcoat to match aging, it can be easily "spot" repaired with a Prevail sprayer for most smaller applications. Remember: unlike your car or house, a boat IS an ongoing repair. And, every big boat I've owned over the last 35 years was, irrespective of condition, a theoretical work in progress. Good luck! Remember, even straight for the factory . . . perfect boats do not exist.
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