# What is the best way to repair cracks in the gel coat



## saurav16 (Mar 22, 2007)

What is the best way/recommended way to repair cracks on the deck and also crazing in the gel coat?


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## Gary M (May 9, 2006)

I do not think you can do much about crazing expect paint the deck. Cracks however, a little job I need to tackle soon, need to be ground out a bit a and then filled with a matching gel coat. It is important to keep water out of the underlying structure so cracks should be attended to. 

There is a company in Florida that does custon matching gel coat. they have the colour codes for many common manaufacturers. They are Mini-craft of Florida.

Gary


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## TSOJOURNER (Dec 16, 1999)

saurav16 said:


> What is the best way/recommended way to repair cracks on the deck and also crazing in the gel coat?


The cracks and crazing are caused by the flexing of the fiberglass underneath. Gelcoat repair is time consuming and expensive. If the flexing is not stopped, the cracks will return (unless they were from exterior force damage) There are some glass professionals on this forum:
http://www.boatdesign.net/forums/


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## saurav16 (Mar 22, 2007)

For cracks on the deck you fill it with gel coat as well?


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## sailingdog (Mar 19, 2006)

Saurav-

If the cracks are just crazing, then you will probably need to paint over it. However, if the cracks are stress cracks, then you need to fix whatever caused the cracks in the first place. Gelcoat is generally less flexible than the underlying laminate, and if an area of fiberglass is bending due to stress, the gelcoat will generally crack before the underlying laminate is actually damaged. However, without proper reinforcement, which may be as simple as adding a couple of layers of glass, the laminate will eventually fatigue and fail. 

Deeper cracks in the gelcoat need to be ground out, filled with thickened epoxy and then either painted or gelcoated.


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## saurav16 (Mar 22, 2007)

The cracks for the most part are just under the stanchions, which is common right?


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## sailingdog (Mar 19, 2006)

That probably means the deck has some problems and that water has gotten in the core, if the deck is cored there. Do the stanchions have solid backing plates under where they are mounted? If not, I would take the stanchions off and check the deck beneath. If the deck is sound—without core or without core problems—sand the gelcoat, and re-gelcoat the top before remounting the stanchions. When you re-mount the stanchions, and add a decent size backing plate of stainless steel, aluminum, fiberglass or epoxy-coated marine plywood. If you use anything but the stainless, add fender washers. If the deck is cored—pot the holes after drilling them out oversized and then re-drill the fastener holes through the thickened epoxy you use to pot the holes. I also like to counter sink the fastener holes a tiny bit to allow the sealant to form an o-ring type seal.


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## TSOJOURNER (Dec 16, 1999)

So which product should someone with cracks use to fill back in the gelcoat or epoxy? I'm keen on epoxy myself and re-painting over, since my deck is Camel and I wanted white anyhow... Which epoxy is considered good for this purpose?

I had several cracks just from weathering and neglect, so perhaps there is a third cause? or is that considered crazing?


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## TSOJOURNER (Dec 16, 1999)

A question from the cheap skate...

What is the difference between gel coat and supplies from the specialty store and a fiberglass shower refinishing kit from the home improvement store?


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## sailingdog (Mar 19, 2006)

I'd use either MAS or West Systems epoxy with a chopped fiberglass filler to fill the cracks. IIRC, you can gelcoat over epoxy, provided you scrub the amine blush off the surface. West Systems has aan article on doing it. 


Lancer28 said:


> So which product should someone with cracks use to fill back in the gelcoat or epoxy? I'm keen on epoxy myself and re-painting over, since my deck is Camel and I wanted white anyhow... Which epoxy is considered good for this purpose?
> 
> I had several cracks just from weathering and neglect, so perhaps there is a third cause? or is that considered crazing?


The gelcoat you get from the bathtub repair kit isn't probably as UV resistant as the stuff you get from the specialty shop, since the UV exposure a bathtub gets is minimal.



arbarnhart said:


> A question from the cheap skate...
> What is the difference between gel coat and supplies from the specialty store and a fiberglass shower refinishing kit from the home improvement store?


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## saurav16 (Mar 22, 2007)

SD, 

NO backing plates, I was going to add stainless steel backing plates under the stanchions to keep this from happening again.


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## sailingdog (Mar 19, 2006)

I figured as much from your description of the stress cracks. 



saurav16 said:


> SD,
> 
> NO backing plates, I was going to add stainless steel backing plates under the stanchions to keep this from happening again.


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## TSOJOURNER (Dec 16, 1999)

sailingdog said:


> The gelcoat you get from the bathtub repair kit isn't probably as UV resistant as the stuff you get from the specialty shop, since the UV exposure a bathtub gets is minimal.


Turns out it is; the opaque pigment (even when white) is a light blocking solid. What else is (or might be; more guesses are still welcome) different? The cost difference is not incredibly significant, but there is some. The convenience difference is pretty incredible though.


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## sailingdog (Mar 19, 2006)

Arbarnhart-

I used to work in the paint industry... the white pigment is generally titanium dioxide, and yes, it blocks light, but the resin itself may not be as UV resistant in the Bathtub kit, and may not be properly formulated for exposure to the other things that boats are subject to, like UV, extreme heat, extreme cold, etc. Most bathrooms are relatively temperature stable, and not generally exposed to UV, etc.



arbarnhart said:


> Turns out it is; the opaque pigment (even when white) is a light blocking solid. What else is (or might be; more guesses are still welcome) different? The cost difference is not incredibly significant, but there is some. The convenience difference is pretty incredible though.


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## sailaway21 (Sep 4, 2006)

Gel coat does not bond well to epoxy. If you are going to cover with gel coat you should use polyester resin instead of epoxy.


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## sailingdog (Mar 19, 2006)

Sailaway-

That's what I thought originally too... but you might want to read the testing they did over at West Systems with epoxy and gelcoat. LINK.


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## sailaway21 (Sep 4, 2006)

Thanks Dog,
I would be more than a little interested in hearing more on this subject. Most of us end up with mechanical bonds on a lot of our epoxy repair jobs and, if gel coat will adhere as well, it has the potential to change accepted wisdom.


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## TSOJOURNER (Dec 16, 1999)

> The cracks for the most part are just under the stanchions, which is common right?


Yes - it is common, and the backing plates are something you should definitely put on. A suggestion here for you though...

It is going to take a long time and involve a lot of frustration trying to repair the cracks and then match the repair material to the colour of the weathered deck. If your crazing has not spread too far, the easiest and probably best looking solution is to get some thin deck plates cut out of stainless to insert between the stanchion and the deck.

Make patterns from the stanchions, and add one or two inches to the perimeter as needed. Seal the deck with epoxy, put your plates on and your backing plates underneath.

In addition to saving you many hours and much coarse language, it will add a bit of strength to an area that suffers a lot of stress.

Before you do this though, you need to make sure that you don't have any core issues...

Good Luck !


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## saurav16 (Mar 22, 2007)

Thanks as always you guys are a big help. To fill large cracks I should probably use 206 hardner as mentioned in my last post since you want the epoxy to be thick right?


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## sailingdog (Mar 19, 2006)

Depends on the temperature, but generally, if you're thickening the epoxy, using the slow hardener is a good idea, since you need to spend extra time mixing...


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## TSOJOURNER (Dec 16, 1999)

*Deck Gel Coat Cracks Question*

A moisture meter shows moisture in my deckd where there are cracks in the gel coat. Can I just drill some holes and fill with Creeping Crack Filler or Git Rot? Seems to me that it will stop the rot and strenthen the deck. The stuff is premixed and ready to go. - Capt. Ron


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## TSOJOURNER (Dec 16, 1999)

Can I just fill the deck cracks with Creeping Crack Filler or Git Rot? Should strengthen the deck and eliminate the rot from moisture intrusion. What do you experts out there think? A moisture meter shows moisture in the deck at the location where the cracks recently appeared.


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## TSOJOURNER (Dec 16, 1999)

I have an area where I have to do the same repair. 

The book I am using (Practical Sailor volume on maintenance and repair) recommends drilling in a pattern (I will have to check spacing later) and then letting it air dry (possibly with heat) for some time before filling it with thickened epoxy. You drill through the top skin and core but not the bottom. Then you have to refinish the deck. I am considering coming up from the bottom and epoxying in plugs in my holes and then adding some glass on the underside (cabin roof) after drying. I can seal with epoxy on top and then paint. But that is not what the book says to do and I could end up regretting it.


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## sailingdog (Mar 19, 2006)

You really need to repair whatever is causing the deck's gelcoat to crack and re-inforce it before doing anything else. Creeping Crack Filler and Git Rot will not do that. They'll probably not help much with preventing future water intrusion either.


rarelyontime said:


> Can I just fill the deck cracks with Creeping Crack Filler or Git Rot? Should strengthen the deck and eliminate the rot from moisture intrusion. What do you experts out there think? A moisture meter shows moisture in the deck at the location where the cracks recently appeared.


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## TSOJOURNER (Dec 16, 1999)

In my case, the cracks appear to be from an impact and once sealed I don't think moisture will come in there again. There are a couple of places where I have cracks but I am not sure I have moisture; I am assuming that sealing the top will be adequate there, but I will drill a hole just to get a sample from the bottom and plug it. If the sample is moist, I will drill more, dry and then plug. Soft spots would require a different approach.


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## helmsmatt (Jul 29, 2002)

I did have crazing (not stress cracks) throughout my deck gelcoat.
I was able to re-gelcoat, but it wasn't easy.
First, I sanded the surface,
Then I brushed on a relatively thick layer of gelcoat.
Then I block sanded the gelcoat to get it flat. This would sand most of the new gelcoat off, but filled the crazing.
Then I sprayed several coats of gelcoat.
A light sanding with 400 and 600 grit flattened the orange peel.
Compound, wax, done.
I didn't want to paint, as a similar amount of labor for paint or gelcoat results in a shorter life for painted surfaces vs. gelcoat. Gelcoat is easier to repair also.
For more detail, email me.


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## sanctuarysam (Sep 16, 2006)

*has anybody heard of/tried this?*

i have a couple of spots on my deck and came across this site..not sure if it's any good or not..
anybody seen this stuff?
http://www.epoxyproducts.com/capt.html

thanks,
sam


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## Idiens (Jan 9, 2007)

sanctuarysam said:


> i have a couple of spots on my deck and came across this site..not sure if it's any good or not..
> anybody seen this stuff?
> http://www.epoxyproducts.com/capt.html
> 
> ...


I have used it, frankly it didn't work too well.


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## cardiacpaul (Jun 20, 2006)

ummmm
catalinadirect has a kit for the stanchions
http://www.catalinadirect.com/index.cfm?fuseaction=product.display&Product_ID=30

might just as well do the chainplates too
http://www.catalinadirect.com/index.cfm?fuseaction=product.display&Product_ID=12


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## chucklesR (Sep 17, 2007)

I had a couple of scratches in the gel on my boat, and since I had a chunk of 'miracle cloth' (metal polishing primarily, but said it was good on fiberglass so what the heck) in my hand I rubbed at them.
Long story short, they went away, the chemicals in the cloth compounded the surface, filled the scratch, and polished the area to where I can neither see nor feel where the problem was.
Mind you, this wasn't crazing or cracking, just a scratch.


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