Repairing deck gellcoat stress cracks

[Exile]

Originally Posted by Boatyarddog

Use alkyd enamel paint, it's great for filling in those cracks checks, and impurrefections.
It's softer, but gets harder as time passes.
Epoxy is very brittle. And will crack again.
Interlux has lots of nice colors too.


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I thought paint was a no-no over gelcoat w/o extensive cleaning, de-waxing, and priming?

[Terra Nova]

Sounds like you are using an inferior product or mixing it wrong.

[BigBeakie]

Sometimes generic statements about materials are not appropriate. The epoxy is flexible vs epoxy is brittle is a case in point.

Epoxy resin can be either brittle or flexible depending on the formulation. It should be no surprise that a materials characteristics depends on the chemistry.

Eg. West System 205 is fairly brittle and shatters when you whack it and System 3 resin is tougher and will not shatter nearly as easily. I tested an epoxy made here in Australia where we couldn't break it no matter how hard we smashed it.

So, it depends.

[Boatyarddog]

Originally Posted by Exile

I thought paint was a no-no over gelcoat w/o extensive cleaning, de-waxing, and priming?

As with any paint sanding and primers are required, dewaxing, is needed on new layup, as well amine blush removal.
Certainly not extensive, but scuffing up the old gelcoat is nessessary, as well, removal, of dust and wipe down with solvent.
Usually required with all good paint jobs.
Just did the interior of my boat, after sanding the shine off of the gelcoat interior applied, Interlux primer and rolled on acrylic enamel, that's a latex, looks beautiful, and is very tough, doesn't scratch off.


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[Exile]

Originally Posted by BigBeakie

I've used Magicezy on both stress cracks and deep gouges. The liquid Magicezy for thin stress cracks works well. It flows down into the thin cracks and bonds to the gel coat. You can run a fine sewing needle along the crack to open it up, ie V it before applying. With a slight buff after setting for 24 hrs, the cracks have disappeared.


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I was going to try this or a similar product on some stress cracks and an experienced pro who's done other deck work on my boat strongly advised against. He said it simply didn't work, but I can't recall further particulars as it was awhile ago. I hope yours has held up.

[Boatyarddog]

Originally Posted by BigBeakie

Sometimes generic statements about materials are not appropriate. The epoxy is flexible vs epoxy is brittle is a case in point.



Epoxy resin can be either brittle or flexible depending on the formulation. It should be no surprise that a materials characteristics depends on the chemistry.



Eg. West System 205 is fairly brittle and shatters when you whack it and System 3 resin is tougher and will not shatter nearly as easily. I tested an epoxy made here in Australia where we couldn't break it no matter how hard we smashed it.



So, it depends.

West systems 205 is a hardener, I believe, resin is 105, 206 is the slow hardener.


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[BigBeakie]

Yep, correct. The resin is 105. Sorry for the typo.

[Exile]

Originally Posted by Boatyarddog

As with any paint sanding and primers are required, dewaxing, is needed on new layup, as well amine blush removal.
Certainly not extensive, but scuffing up the old gelcoat is nessessary, as well, removal, of dust and wipe down with solvent.
Usually required with all good paint jobs.
Just did the interior of my boat, after sanding the shine off of the gelcoat interior applied, Interlux primer and rolled on acrylic enamel, that's a latex, looks beautiful, and is very tough, doesn't scratch off.


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Yes, but I thought you were referring to using an enamel paint to fill in stress cracks on a gelcoated deck. Did I misread this?

[minaret]

Originally Posted by Exile

I was going to try this or a similar product on some stress cracks and an experienced pro who's done other deck work on my boat strongly advised against. He said it simply didn't work, but I can't recall further particulars as it was awhile ago. I hope yours has held up.

I would agree with your experienced pro. Crack cure is snake oil.

[cabo_sailor]

I too have been plagued by cracking both cosmetic and structural. Some are mere voids where the glass didn't get wetted out with resin. Some are impact cracks from dropping something on the deck. The nastiest are structural where the crack extends into the underlying glass.

It's been a long learning curve. Using a one size fits all has resulted in success for some cracks but the reappearance of some of the structural particularly where the bulwarks join the deck.

Those will need a somewhat more aggressive approach involving glass fiber and laminating resin. Not difficult but time consuming.

But in all cases I would place strong confidence in Minaret' suggestions. After all he does this for a living.

As an aside, I can say the later repairs have held up better than the first. Maybe I am learning something 😜


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[Boatyarddog]

Originally Posted by Exile

Yes, but I thought you were referring to using an enamel paint to fill in stress cracks on a gelcoated deck. Did I misread this?

Referring to repainting the deck.
Sounds like the gelcoat has been removed then coated with epoxy and colloidal silica, pigmented I would imagine.
In hot sun without a covering of some kind epoxy doesn't do well, uv damage.
That's is why I suggested they prime & paint with Alkyd enamel. As a protective cover.
Larger cracks should have been filled and faired with epoxy thickened with 410 microlite fairing filler powder.
Then the deck would be prepped, primed and repainted.
I'm no refinishing guru, but I've had no problems with this procedure on any projects I've done this
I think these cracks may be shrinkage and damage by UV, and due to differing rates of contraction of the substrates.
Should keep that boat covered in hot sun.

If they are stress cracks, they'll probably reappear eventually unless something is done to change the stress loads, or those areas are reinforced.


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[Exile]

Originally Posted by cabo_sailor

I too have been plagued by cracking both cosmetic and structural. Some are mere voids where the glass didn't get wetted out with resin. Some are impact cracks from dropping something on the deck. The nastiest are structural where the crack extends into the underlying glass.

It's been a long learning curve. Using a one size fits all has resulted in success for some cracks but the reappearance of some of the structural particularly where the bulwarks join the deck.

Those will need a somewhat more aggressive approach involving glass fiber and laminating resin. Not difficult but time consuming.

But in all cases I would place strong confidence in Minaret' suggestions. After all he does this for a living.

As an aside, I can say the later repairs have held up better than the first. Maybe I am learning something 😜


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Funny how you get better at these sorts of jobs. Easy in my case since I started at the nursery school level. I also have some thinning & crazing gelcoat that is typical of the deck of an older boat. After reading many of Minaret's advice & suggestions in several threads, I have thus far had some success keeping the gelcoat up and not resorting to painting.

There is, however, one troubling area of lengthy stress cracks emanating from one of four U-bolt deck fittings which secure the shrouds. As Minaret has already mentioned, I'm pretty sure the only lasting remedy is to grind out the entire section and build back up. The problem is that the entire area is part of a section of molded gelcoat nonskid, so then I'm looking at one of those Flex-Fold products to attempt to re-do the factory nonskid (probably a nightmare), or have one section painted with nonskid but the rest of the deck molded gelcoat (not good). Not sure what to do and the cracks are tiny in diameter, but I'm getting nervous about eventual water penetration into the cored deck. Any thoughts?

[Exile]

Originally Posted by Boatyarddog

Referring to repainting the deck.
Sounds like the gelcoat has been removed then coated with epoxy and colloidal silica, pigmented I would imagine.
In hot sun without a covering of some kind epoxy doesn't do well, uv damage.
That's is why I suggested they prime & paint with Alkyd enamel. As a protective cover.
Larger cracks should have been filled and faired with epoxy thickened with 410 microlite fairing filler powder.
Then the deck would be prepped, primed and repainted.
I'm no refinishing guru, but I've had no problems with this procedure on any projects I've done this
I think these cracks may be shrinkage and damage by UV, and due to differing rates of contraction of the substrates.
Should keep that boat covered in hot sun.

If they are stress cracks, they'll probably reappear eventually unless something is done to change the stress loads, or those areas are reinforced.


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OK, I understand what you're talking about now. I generally use West Systems epoxy to repair minor cracks & dings on my deck, and can confirm that any of these areas not covered over with fresh gelcoat will eventually turn dark from UV. Not sure if the discoloration also means it has been weakened but it wouldn't surprise me.

[cabo_sailor]

I don't know if this helps but many years ago I crewed on a club racer that got t-boned. We lost part of the toe rail and had a nice hole in boat at the hull deck joint.

The yard ground down the nonskid pattern on the damaged and then ground down the same shape on the undamaged side. They left both relatively small areas smooth and re-gel coated both. You couldn't tell there had been any damage since both sides matched

Still had to replace the entire toe rail.

Rich


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[Exile]

Originally Posted by minaret

I would agree with your experienced pro. Crack cure is snake oil.

Thanks for this info, Minaret. Turns out you & the experienced pro I'm referring to agree on a lot! He loves my boat and generally has only one way to make repairs -- the right way. I always come around in the end, but not before I've wasted his time with poorly conceived "shortcuts." I probably annoy him with all my banter, but maybe that's why surcharges on invoices were invented!