I need some gel coat assistance

[buckbuck]

I don't know what I'm doing. Somebody help me.
I bought the kit @Bill D recommended to do the same repair on the bottom of my boat. How much do you add of the MEK? What is the brown bottle for? Do you guys use a postage scale to measure the amounts?
I'm scared and feel all alone.

 

[Bill D]

Jim, full disclaimer... this was my first attempt and I don't guarantee results. Lol

I used my wife's little food scale to measure out 8 oz into a mixing cup. I think I then added 1 ml of the catalyst to the gel coat and mixed with a little wooden stir stick. (I also think I added a little more before applying.) Warning, make sure you mix it up good and don't have any stuck to the sides or it won't cure. Also, if it is cooler you need additional catalyst. I didn't realize this, and the stuff I left overnight wasn't fully set the next morning. I also really wasn't thrilled with the mix I had, so more catalyst may be helpful. It was much thinner than the paste I used on the black parts of the boat.

I think a key part to the application is to clean the area well and remove any wax or other surface contaminants, then sand the area down with a good rough sandpaper. The roughest I had was 320 grit and I would have liked a rougher finish for better adhesion and cover for the new gel. If I did it again, I would also do several applications over the same area, several hours apart. I didn't want to mix, waste, remix, waste and so on, so I did one application in a thicker coat. Probably not recommended... Good thing it's the bottom of the boat.

BTW, I love the homemade supports. Genius.

 

[buckbuck]

@Bill D , did you use the brown bottle? It seems to be for curing.
Was that one ml or one tsp? Seems like they want 20% on the catalyst.
I am still kinda scared.

 

[Bill D]

I think I went by the mixing instructions on the bottom of this page.

https://www.jamestowndistributors.com/userportal/document.do?docId=257

If my brain serves me correctly, one cc and one ml are the same amount. I had an eye dropper that read in ml laying around, so I used it. They recommended 8+ cc per quart for 1% at 77*. Since I went with 8oz, I divided the 8/4 to start, then added a little at a time as stirring until I thought it thickened up.

I forgot to mention the brown bottle. Should be something like 1oz per quart so for my 8 oz cup it was 1/4 of the bottle or like 7 ml. I added this after I got the catalyst stirred in and before applying.

 

[swatski]

@buckbuck Love the supports!

Have you guys considered using those disposable sprayer kits from Preval? The great thing is, those are like $5 a kit at Menards if I remember correctly, you can mix small amounts of gel coat to experiment and/or to do multiple layers, as soon as the thing starts to clog - chuck it and set up another one. Spray painting gelcoat is generally not recommended, but there is no perfect way to do it anyway. You will ALWAYS get "orange peel" not matter what you do, and the last step is wet sanding and buffing with some cutting compound, always.

The MEK is tricky, too much is worse than too little.


These are the kits I'm referring to:

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[tdonoughue]

2x on the Preval sprayer. But you will need to thin to use that.

Heading to dinner with family now, but will write more later. I would definitely hold up until we can get you more instructions. I have the same kit here somewhere (haven't used it yet), but I have done the paste stuff a bunch. Got some tips for you, just need more time to write them up.

Don't panic; remain calm.

 

[GTBRMC]

@Glassman

Any thoughts?

 

[buckbuck]

Well the good thing about this job is it does not have to look good. It will be on the bottom where the bunks make contact as you are retrieving the boat. I just want to protect the fiberglass.
I have abandon this project until you guys get me through a couple therapy sessions. Gel coat is so scary.

 

[Bill D]

Those sprayers are an interesting idea. I wanted to keep it as simple as possible since it was my first attempt.

Started with the paste. Easy peasey. I can do this, it's just some grinding, sanding, applying, and a lot more sanding. Couple passes with the buffer and you can't even tell it was there.

 

[tdonoughue]

Ok, I think my kit is at my boat. So verify this against the directions to see if it does not make sense:

The two things you mix together are the catalyst (clear bottle) and the gelcoat (can). That is the stuff you need to get in the right proportion. And that is something I have not figured out how to do exactly yet. But I am thinking it is going to involve measuring volumes, not weighing. Probably an eyedropper and a shot glass-sized thing will be involved, I think. I believe the directions called for 2% by volume, so I will be getting an eyedropper full of the catalyst and putting it in with 50 eyedroppers of gelcoat. Good stirring will be critical.

You will need to thin your mixture in order to use a sprayer. The problem here is that usually you use acetone to do that, but the instructions say expressly NOT to use acetone. So, this is where we may need @Glassman to advise. I have looked on the web some, but all I found was expensive things in quantities I didn't want to buy...

So, to do this, first, get a block and wet block sand with 600 grit or so to get rid of those burs and junk on your repair area. You want to make it as smooth as possible before you begin. Don't worry if you expose more epoxy a little bit. Once basically smooth (and it will not be shiny--don't worry), you are going to want to wipe the whole thing down with acetone. That will clean the surface. Let that dry before proceeding.

Then, you are going to spray. I did it thinning the paste stuff to an impossible degree and it did work ok. It will be better with the stuff you bought, as it is runnier to begin with. Next time I will be using my real sprayer (since I have one), but the Preval will work fine. Get an extra sprayer and can for it, and remove the screen off the bottom of the intake tube before you start. Test on a piece of cardboard so you learn how far to be from your work when you spray. When I did it, it was 8-12 inches or so. You don't want so thick a coat that it runs, nor so thin that it does not cover.

I *think* that the brown bottle is the mold release. You don't stir that in; you spray it on afterward to cover the gelcoat so that it can cure (but remember--I can't find my kit, and I can't read all the bottle in your pic, so verify this part). It keeps the oxygen from the repair area. It is much better than trying to cover with Saran Wrap or plastic. It will cover everything very nicely. Don't worry about hurrying to get it on. Take your time and clean up your leftover gelcoat with acetone (not water). Dry with paper towels and be picky to get everything off. Spray some acetone out of the sprayer. Clean the intake tube. Let it all dry thoroughly. Then put in the mold release and spray that over the gelcoat (it should be pink, I think). The mold release will dry and leave a film coat on the top of your gelcoat. Let that sit overnight.

(oh, if that brown bottle is not the release, then you will want to get some PVA mold release before you start--use it as I set out above; and, of course figure out what the brown bottle is then for before you begin...)

That mold release wipes off with water afterward. Use a damp sponge and some elbow grease. Elbow grease decreases with water, so use water liberally. Once that is all off, things get easy. Now you are down to sanding. Start with that 600 grit, then to 800, etc. After that, I went to polishing compound (I used Griot's #3) with a buffer and it shined up nicely. I finished with Griot's #2. Be forewarned: until that last step, it will look dull and you will think you are really screwing things up with the sanding, but you are not. When you break out the polish, that puppy will shine. And you will be disappointed it is on the bottom of the boat.

 

[swatski]

I think the brown bottle is probably a thinning additive, styrene monomer with some extra MEK, patch aid or whatever they call it. I have thinned with acetone and it works fine, but you can only add a little bit, definitely not more than about 10-20% of the total volume. That said, if you have the additive, I would use that.
I would use (sacrifice) one Preval to get a handle on things, try it on a piece of cardboard to make sure you can spray and everything cures. You will get some orange peel - so that is not an issue.
From what I remember, the Prevals get very cold as you spray, and that messes those up as they start spitting chunky stuff and it is a mess/over. That is why you need several of those kits, I think cleaning and reusing is not really practical.
And not to be a smart alec, but I think those Spectrum kits will cure fine without covering the job with either plastic or pva or what not.

And 2% vol/vol is roughly 14 drops per oz. (MEK hardner to gel coat). So that is easy, you don't have to worry about the size of the drops - there is some buffer in those ratios.

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[Glassman]

@Glassman

Any thoughts?

Yes, but they always get me in trouble.


On the sprayer? Sure, they are pretty good - especially if it's a small job and you either don't have a compressor and spray gun or air brush or simply don't want the hassle of clean-up. Sometimes the smallest jobs are a pain in the neck due to prep and clean-up.

For thinning or reducing we always use acetone. For the aerosol sprayer you need to get it pretty watery and I recommend using a surfacing agent as well to aid in the drying process...otherwise it may remain tacky for a long time. We use a surfacing agent made by Valspar - #5788C90007

 

[buckbuck]

It is my intention to just brush this on. I would not mind ending up with a build up of gel coat in these areas due to that is where the boat hits the first bunks. @tdonoughue it appears that brown bottle is some kind of curing agent. Do you think I can just brush it on after the gel coat has set?

 

[Bill D]

I may be fuzzy on this, but doesn't it say on the brown bottle to add it to the gel coat? I had in my mind that it promoted curing by drawing things out of the mixture.

 

[buckbuck]

yes it does. Seems to me there is a lot more art than science in gel coat. I guess that is why I am struggling.

 

[Bill D]

Bah, art is suggestive and doesn't have to be right to be good. I'll jack my boat up one evening this week to see if what I did is still there. I realize now that I'm horrible at taking pictures as I do these things...

 

[swatski]

that brown bottle is some kind of curing agent

Ah, so it is a thinner with some wax to aid curing. I would definitely mix it in and avoid messing with the fresh surface.
And yes, it is an art, no doubt. LOL
Over and out.
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[tdonoughue]

Fully agree. A thinner with curing aid. Mix it in as it says.

Then I would still get the PVA mold release. That stuff was magic. Even if you brush on (in which case, by the way, you won't need to thin it extra), use a Preval sprayer to spray on the mold release afterward. You will be happy you did. Far easier than covering it or waiting forever for it to cure.

Yes, there is some art there. And the science is not as exact as you think. You will be fine, despite how it seems. That is what I experienced on my first repair. Really nervous over it, in the middle was sure I had screwed it up, and was amazed when I got to the last step that it turned out perfectly and I could not even see where the blemish had been.

Oh, and listen to everything @Glassman says. Thank you, sir.

Reminder: we do require pics as you go and after you finish.

 

[FLJetBoater]

So I got ambitious and attempted to repair some small dings in my gelcoat that have been bothering me since I bought the boat. Got all the supplies, boat prepped and ready to go. I didn't realize until AFTER, but I WAY WAY WAY over-catalyzed the gelcoat. I read the instructions as 1 OUNCE per pint, not 1 TEASPOON per pint. Probably since the bottle of MEKP was in oz, and the wax ratio was in oz, the wax bottle was in oz, so I just didn't pick up it was tsp. So I figure I over catalyzed by about 6x as 1 oz = 6 tsp. The gelcoat was completely set in the can in less than 5 minutes and the can was extremely hot - I couldn't even hold it.

I did put it on before it set, but now I'm not sure how well it's going to cure?

 

[tdonoughue]

Oops.

Well, you are where you are, right? Cover it and let it sit until tomorrow. Then evaluate. It will either be fully hardened and look and feel like normal gelcoat or... not. If so, sand and polish it up and call it a win. If not, sand it up a bit to even it out, Dremel out the bad stuff and try again.

That's the nice part about gelcoat. Even when you screw it up, there is grace and redemption.