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Old 03-07-2011, 11:43   #1
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How to Repair Fiberglass Sinks

We have built in fiberglass sinks with a gel coat finish (I think) in our galley and they are cracked and chipped all over (sides and bottoms of both sinks). We've debating trying to repair them or just get rid of them. We've never tackled a job like this (our last boat was steel) and have no idea what it would take to fix. Is this a job for a professional or could a novice do it? How expensive? Thanks!

Catherine
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Old 03-07-2011, 12:32   #2
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Re: How to Repair Fiberglass Sinks

First, is it the fiberglass or just the gelcoat that is cracked? If both are cracked I'd consider buying a stainless steel sink and replace it.

If that is not considered an option, fiberglass repair for something like this is not too terribly difficult. There are many books, videos and web sites including those of West System and Jamestown Distributors that have instructions/videos on the process.

Since you are only talking about a small area, I wouldn't even bother trying to match gelcoat colors and would use the stock white. Home Depot sells a small airless sprayer that you can use for the application (Preval Airless Sprayer) that costs a bit less than $5. Once the repaired area is sanded smooth to match the rest of the sink, take a couple of ounces of gelcoat add about 14 drops of catalyst (comes with the gelcoat) and give several coats. You'd like to build up about 2mm or so. Some gelcoat will cure on its own and others require a light spraying with a liquid wax to block of the air so that they will cure. Ask your supplier which one he's selling you.
Don't worry about runs and such, you'll sand them out later.

They say 4 hrs to cure but I usually leave it overnight. Wet sand with 320 grit until smooth, then with say 500 grit and finally with polishing compound. Voila, you're done. Say one day for the fiberglass repair, next sand and gelcoat, third day sand and polish.

Gelcoat is running around $17/qt, the sprayer(s) might run you $10-15, for the fiberglass repair (if it is needed) the cost varies a bit depending on what you need. There will be expendable supplies as well, some acetone, rags, perhaps masking tape, and, of course some sand paper.

I'd still recommend trying to replace them with stainless. The problem with gelcoat is that although it is tough it is also a bit brittle. It will not take kindly to dropping pots and pans on it. I suspect that's why you are seeing the cracks now. The only problem is that new sinks are rather pricey so you might look for them at a marine salvage yard. If you are really lucky the size might be available at a home supply store.

Search Results for paint sprayer at The Home Depot

Good luck,
Rich
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Old 03-07-2011, 13:25   #3
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Re: How to Repair Fiberglass Sinks

Rich,
Thanks so much for that detailed reply. I think it might be worth a try. I only think the gelcoat is cracked. The sink area is white, so no problem with color, I guess it may make my surround look a little dinghy but oh well. We did look into stainless sinks (that would be first choice), but the size is so odd (very long and narrow) that we couldn't find anything to fit. We've been getting quotes for corian installation, which isn't as bad as we thought it would be (cost wise), and it's still an option if this doesn't work.

Catherine
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Old 03-07-2011, 15:12   #4
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Re: How to Repair Fiberglass Sinks

See if you can remove the sink first, then you'll be able to see the backside and tell if the cracks go all the way through. If they do just laminate an extra couple of layers of glass to the whole backside of the sink or sinks for a quick repair for multiple cracks. Then repair the cosmetics on the inside of the sink. That way you can also do the whole messy job off the boat. Should be able to bang it out quick.
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Old 03-07-2011, 15:22   #5
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I just modified the entire cabinet complete with basin on our lagoon 440 as I needed the extra 1" height to fit our washing/drying machine. We bought a standard basin and fixed it to the underside of our counter top. Worked beautifully and many sizes to choose from. I believe the material is corean or something like that?
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Old 03-07-2011, 15:30   #6
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Re: How to Repair Fiberglass Sinks

Quote:
Originally Posted by cabo_sailor View Post
First, is it the fiberglass or just the gelcoat that is cracked? If both are cracked I'd consider buying a stainless steel sink and replace it.

If that is not considered an option, fiberglass repair for something like this is not too terribly difficult. There are many books, videos and web sites including those of West System and Jamestown Distributors that have instructions/videos on the process.

Since you are only talking about a small area, I wouldn't even bother trying to match gelcoat colors and would use the stock white. Home Depot sells a small airless sprayer that you can use for the application (Preval Airless Sprayer) that costs a bit less than $5. Once the repaired area is sanded smooth to match the rest of the sink, take a couple of ounces of gelcoat add about 14 drops of catalyst (comes with the gelcoat) and give several coats. You'd like to build up about 2mm or so. Some gelcoat will cure on its own and others require a light spraying with a liquid wax to block of the air so that they will cure. Ask your supplier which one he's selling you.
Don't worry about runs and such, you'll sand them out later.

They say 4 hrs to cure but I usually leave it overnight. Wet sand with 320 grit until smooth, then with say 500 grit and finally with polishing compound. Voila, you're done. Say one day for the fiberglass repair, next sand and gelcoat, third day sand and polish.

Gelcoat is running around $17/qt, the sprayer(s) might run you $10-15, for the fiberglass repair (if it is needed) the cost varies a bit depending on what you need. There will be expendable supplies as well, some acetone, rags, perhaps masking tape, and, of course some sand paper.

I'd still recommend trying to replace them with stainless. The problem with gelcoat is that although it is tough it is also a bit brittle. It will not take kindly to dropping pots and pans on it. I suspect that's why you are seeing the cracks now. The only problem is that new sinks are rather pricey so you might look for them at a marine salvage yard. If you are really lucky the size might be available at a home supply store.

Search Results for paint sprayer at The Home Depot

Good luck,
Rich
Finish thickness for gelcoat should be 16 mils. 2mm would be 78 mils, much too thick. Ratio of catalyzation should be 1-2% depending on ambient temperature, using the usual hot methyl ethyl ketone peroxide. Thats 22 cc per qt. for 2%, it's usually easy to figure from there. A proper squeeze beaker helps a lot. I can be wet sanding in an hour on a warm dry day, less with careful heat gun use. And all gelcoat needs wax or some other surface seal to surface cure, it's just that some gelcoat is sold with the wax already added. Personally I prefer to use unwaxed gel for repairs, and only add the wax for surface seal in the last coat. 4 nicely sprayed coats should give you about 20 mils, which will sand out to something like the desired 16. And a 20$ touch up gun will do a much nicer job than a preval, which will crap out on you repeatedly. Finish with at least 800 wet, or you will be able to see the scratches after polishing. Usually I start with 800 wet, but I shoot nice. I finish with 1500. Thin with MEK or styrene monomer to acheive a nice spray finish. Don't thin gelcoat more than 5-10% or you'll begin to experience wierd problems. And don't use a heatgun unless you know what you're doing, you'll discolor it by making it kick too hot. Finally, a good guide coat can be very helpful for newbies in acheiving a nice wet-sanded finish quickly.
Oh and sometimes on something like a sink you cant fit in a normal buffer to do the polishing. They sell a nice little polishing wheel you can chuck in to a pneumatic die grinder. I use these for polishing inside wierd shapes a lot. They are also great for polishing bronze and stainless very quickly. Use a regulator to turn the air pressure way down so they run slow and you wont burn anything. These 1" buffer pads fit into a standard Rolok shaft.
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Old 04-07-2011, 09:45   #7
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Re: How to Repair Fiberglass Sinks

Thanks Minaret, I stand corrected. I agree with the use of the other sprayer as a rule. I use a $24 glazer airbrush for most of my work. I suggested the Preval for a one time use and normally justuse the Preval to simply spray the wax on the final coat. I also prefer to use the waxless gelcoat and apply a few layers giving each a few minutes between coats and then hit it with wax.

I don't mind waiting the 4 hours or even better next day for sanding. After cleanup that gives me a chance to relax in the cockpit with a glass of "ol' thought provoker" and contemplate my next task.

Normally, I finish the wet sanding with 600 grit and then use polishing compound. Seems to work for me. As to the catalyst I use 7 drops per oz of gelcoat and again its worked well for me. For thinner I just use acetone. I know I should use the other stuff but its just one more can of "stuff" to have around. I usually thin to the consistency of cream or perhaps a tiny bit thinner prior to spraying. If color matching I thin to almost water consistency to make sure that every last particle of the coloring agent gets dissolved. Once the color match is satisfactory, I just let the acetone evaporate out.

Thanks for the suggestion on the small buffer pads, I'll look into those.

One final thought, Bennet Marine sells a few DVD's on cosmetic gelcoat repair. Volumes one and two are useful and I used them as my initial instruction. Volume three is kind of redundant.

I guess there's more than one way to skin a cat.

Regards,

Rich
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Old 04-07-2011, 10:11   #8
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Re: How to Repair Fiberglass Sinks

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Originally Posted by cabo_sailor View Post

I don't mind waiting the 4 hours or even better next day for sanding. After cleanup that gives me a chance to relax in the cockpit with a glass of "ol' thought provoker" and contemplate my next task.

Normally, I finish the wet sanding with 600 grit and then use polishing compound. Seems to work for me. As to the catalyst I use 7 drops per oz of gelcoat and again its worked well for me.

I guess there's more than one way to skin a cat.

Regards,

Rich
Wish I got to kick back with the old thought provoker! The reason I'm in a hurry is because I'm a proffesional, and when people are paying you more than a hundred bucks an hour they dont want to see you stand there watching paint dry. Many people finish with 600 and find it adequate, in fact I did so myself for many years. Then I REALLY developed "the eye" and now I can see 600 scratches in a finish from 10' away. It's a curse as most owners dont notice such things. However some do, and we work on a lot of crewed megayachts which have very proffesional and picky captains. Those guys demand a perfect finish. I find that 800 wet sands almost as quick as 600, with a little elbow grease, so it doesnt really take much longer to start with 800. Then you dont have to worry about sanding out the coarse scratches from 600. I'd only go down if to a coarser grit if I had a problem on the shoot like contamination, dust, bugs etc. Certainly Id never use 320, it'd take forever to get out the scratches from that. In the last ten years I'd say the greatest innovation on the gelcoat finishing front has been wet sanding disks for your DA. On projects of any size I always start with guide coat and an 800 grit DA pad. Then you only have to wet sand the corners by hand. Not only does it make it go really fast, but the random orbit helps the grit profile from standing out.
If you dont have or want a proper squeeze beaker for catalyst, a syringe works very well for accurate measurements. Measuring by "drops" is inherently innacurate, though the whole process is pretty forgiving and most of the time you can get away with a lot.
There are indeed many ways to skin most cats. Hope I can help people skin 'em quicker and easier though!
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Old 04-07-2011, 10:29   #9
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Re: How to Repair Fiberglass Sinks

Yeah I suspected you were a pro when you started getting into all the air compressor related equipment. I don't really have any air equipment except for the air brush compressor. For grinding out cracks and such I use an electric die grinder with a conical tungsten carbide bit. The original poster might find a Dremel tool with a small grinding bit will work well enough for the relatively small sink. A number of years ago I used one on a fiberglass countertop and you still can't tell it was repaired. I wish I could have a good set of air tools but the wife will kill me if I start bringing anymore tools home. What I have works well enough and I do the work for relaxation and to avoid having to pay someone like you. Just can't afford it.

As to the drops, yep they are not real precise but your right the gelcoat is pretty forgiving.

I'll go ahead and order some 800 grit. I keep all my sandpaper in an expandable plastic wallet and it currently ranges from 50 grit to 600, there's another slot I can stick a box of 800 into. The videos I mentioned are where I learned the basic process but as I gain experience I find myself modifying those techniques and speeding things up a bit. In any event, its always good to get some input from the pros, thanks again.

Rich
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Old 22-01-2012, 15:38   #10
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Re: How to Repair Fiberglass Sinks

OK, believe it or not, we're just getting around to doing this and things aren't going well. We are trying to use a gelcoat to repair our cracked fiberglass sinks.We are on round two of trying to use the gelcoat and we're about ready to give up, but thought we'd pose a question here to see if anyone has any other ideas.
We bought 1 qt. of gel coat with wax(Hi-Bond) and we are mixing it in 1/4 qt. batches. The first time, we used acetone to thin the mixture so it would spray using the preval sprayer - it sprayed on nicely, but the gelcoat never hardened (after several hours it was still like wet paint). Second time: tried less acetone to thin (it was too thick to use the sprayer), and we used a brush and roller to try and apply it. Still didn't harden after several hours; some was tacky in areas and other areas were wet.

If we try this again, we may just forget the thinning with acetone and try to apply with a roller. Any thoughts here? The previous comments implied that the ratio of gelcoat to catalyst was forgiving (and we don't think we're too far off) - but maybe that's the problem? How long should it take to set up? Not sure what to do, but this is the last time we're trying.
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Old 22-01-2012, 17:16   #11
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Re: How to Repair Fiberglass Sinks

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OK, believe it or not, we're just getting around to doing this and things aren't going well. We are trying to use a gelcoat to repair our cracked fiberglass sinks.We are on round two of trying to use the gelcoat and we're about ready to give up, but thought we'd pose a question here to see if anyone has any other ideas.
We bought 1 qt. of gel coat with wax(Hi-Bond) and we are mixing it in 1/4 qt. batches. The first time, we used acetone to thin the mixture so it would spray using the preval sprayer - it sprayed on nicely, but the gelcoat never hardened (after several hours it was still like wet paint). Second time: tried less acetone to thin (it was too thick to use the sprayer), and we used a brush and roller to try and apply it. Still didn't harden after several hours; some was tacky in areas and other areas were wet.

If we try this again, we may just forget the thinning with acetone and try to apply with a roller. Any thoughts here? The previous comments implied that the ratio of gelcoat to catalyst was forgiving (and we don't think we're too far off) - but maybe that's the problem? How long should it take to set up? Not sure what to do, but this is the last time we're trying.
Where did you buy the gelcoat? Gelcoat has a shelf life of one year, and the first sign it has surpassed that life is a refusal to cure properly. Almost any gelcoat repair kit you might buy at West Marine or any place similar will be past it's usable life. They sell slow and aren't dated. Buy from a reputable fiberglass supply specialist. Thin with MEK instead of acetone. And don't buy pre-waxed, it's also a source of problems. I buy the wax in styrene monomer separately (it's usually called Surface Seal), and only add it to the last coat. Or you can skip the wax and apply a coat of PVA instead after it's well tacked off. Try using a heat gun on the preval before and during use. You'll get much higher pressures, when the canister gets ice cold halfway through the shoot you lose most of the pressure. Keep it warm and it will last much longer and shoot better. Be careful not to overdo it. And make sure it's warm where you shoot too, gelcoat doesn't like to cure much below room temps. A space heater can help.
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Old 22-01-2012, 18:03   #12
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Re: How to Repair Fiberglass Sinks

Thanks Minaret, I was hoping you'd respond . We did buy the gelcoat from West Marine. Sounds like we need to start over with a new product. Do you have any recommendation for getting off the old, now "tacky", gelcoat? We've been using acetone, but if there's a better way we'd love to hear it.
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Old 22-01-2012, 20:25   #13
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Re: How to Repair Fiberglass Sinks

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Thanks Minaret, I was hoping you'd respond . We did buy the gelcoat from West Marine. Sounds like we need to start over with a new product. Do you have any recommendation for getting off the old, now "tacky", gelcoat? We've been using acetone, but if there's a better way we'd love to hear it.

Yea, sorry to hear about that, it's a bad mess when that happens. As a pro I see it fairly often. Clients try to do a job themselves, use ancient gel off of a dusty shelf somewhere, have a problem, and then bring it to us. It's always annoyed me that manufacterers never seem to label a clear expiration date, I' ve had endless problems. Both brokers and owners often give me gel that came with the boat from the factory. Not only is it usually a poor match, but it rarely cures properly and I took to refusing to use any such gel years ago, even though some clients really whine about having to pay for a color match when they have "perfectly good" gel on hand. Find a good source in your area with high turnover and stick with them. Here I use Fiberlay.
Fiberlay They are awesome.

Getting off the half cured goop is a PITA. Try a stiff plastic scraper, lots of acetone and rags, and sanding when all else fails. Really sucks on a curved surface like a sink. Good luck! Oh, how much catalyst did you put into how much gel, out of curiosity?
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Old 22-01-2012, 22:28   #14
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Re: How to Repair Fiberglass Sinks

The quart of gelcoat came with 1/4 oz of catalyst. We used 8 oz of gel with 1/4 of the catalyst (1/16 oz) + a few drops more. Temps here were in the 70's when we started.
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Old 23-01-2012, 00:20   #15
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Re: How to Repair Fiberglass Sinks

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The quart of gelcoat came with 1/4 oz of catalyst. We used 8 oz of gel with 1/4 of the catalyst (1/16 oz) + a few drops more. Temps here were in the 70's when we started.
If I'm doing my conversion right, 1/16 oz. is 1.77 cc, give or take, which isn't really enough. You need 22 cc for a quart, which means 11 for a pint and about 6 for your half pint. If you only did 2 cc that may have been the problem. Do a test patch with it. But remember, just because you can get it to kick in a cup doesnt mean you won't have problems getting a cure when sprayed. Shoot a little test patch on something and see if it cures nice when mixed much hotter.
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