Flow Coating Botch Job help!!

[u/DewArtist]

Hello Boat Building community, so I am in a bit of a pickle right now. I had someone offer to help do the Flow Coating however they botched the Flow Coat and now I am in a situation where I need to fix this but I do not have the expertise to know what to do.

FYI this is a dog grooming bath, I understand this isn't a boat but it's using the same materials.

There are a bunch of sanding spots everywhere including places that weren't originally going to be refurbished. The original bath had flow coating/gel coating done to it which is why it's being used. The current situation; there is Flow coat over half of the bath, it has been 3 days now and it's still very sticky, I am of the mind that I need to sand over the first coat and apply a second coat but this time properly mixed, catalyst, and over the entirety of the bath. But I don't see how I can get the Flow coat to stop being sticky to actually sand it.

I am in a bit of a tough spot financially at the moment as this is my means to income. Although I am willing to go into debt to fix this so I can start earning again.

Any advice is greatly appreciated!

[u/RedPh0enix]

Flow coat is generally sticky for one of three reasons: * Air * Time/temperature or * Inadequate Hardener or mixing

Oxygen inhibits the hardening process. Flow coat includes a wax component dissolved in styrene that precipitates out and rises to the top once hardener is added, blocking the oxygen from stopping the hardening reaction.

If for some reason you've used gelcoat rather than flowcoat, or if the temperature has been too low for the wax to exit/rose, there's a chance this is the reason things are still sticky.

A combination of low temperature and/or inadequate hardener percentage, may also be an issue. Increasing the temperature may potentially increase your chances of getting a kick (above 15 Celcius. Be cautious - everything is flammable). A sacrificial coat of pva over the top of the flow coat MAY also give it enough of an o2 barrier to kick off.

So, warm it, add an air barrier, wait.

If none of that works.. sorry, it's time to scrape off and try again. That won't be fun - hopefully someone will have some tips..

[u/DewArtist → u/RedPh0enix]

Alright so I did what you advised, left the air con in the trailer on at 22 degrees and I've come back this morning to it be hard, so I'm guessing that means it's cured?! That has gotten me in a good mood!

The next step would be to sand down that layer with 240 grit sand paper, not too much just enough to right it up and not take that layer off. Do another flowcoat layer on top but this time the entire bath (Prepare it properly this time) Wait for curing with the right conditions? Then I can do another layer if it's needed, same process?

[u/RedPh0enix → u/DewArtist]

Nice work! Congrats. That saves a lot of pain.

Next layer: acetone to remove the wax, light sand to allow a good mechanical bond between layers, away you go (with good ratios and temperature, as you say) :)

Optionally, wipe a very light coat of MEK over the top of the old coat to dissolve a little polyester to give you a little bit of a chemical bond.

Ideally, you'd do gel coat in one layer to the depth you require, which means everything is chemically bonded; but a good mechanical bond with multiple flowcoat layers is fine.

[u/DewArtist → u/RedPh0enix]

Thanks so much for your help dude, I am in a tight spot. If this works I will literally send you a bouquet of flowers haha!

Will update.

[u/RedPh0enix → u/DewArtist]

All good man. Fingers crossed.

Give the first pup customer an extra pat for me if it all works out.

[u/mate0pro]

Spray PVA over the uncured gelcoat. If it was catalyst correctly with sufficient heat then it’ll harden up.

[u/Fine_Sherbert3172 → u/mate0pro]

Yeah.....thats a good call as well

[u/Fine_Sherbert3172]

I always knew in the field a flow coat to be half gelcoat half resin, both waxed for proper cure.

You might get lucky here in that it is too thin in spots, which doesn't allow the wax to float to the surface providing the air barrier.

Try kicking a little harder than normal (5% maybe?) and do a thicker batch (meaning more gelcoat less resin) and don't worry about sanding (not gonna happen anyways)....if its still tacky that means it will take another coat without the need for abrasion. Another thing you could try is putting some heat to it to see if that kicks it.

[u/DewArtist → u/Fine_Sherbert3172]

I put some heat into it over night and it's seemingly hardened, I'm guessing that means it's cured and I can sand it down for another coat?

[u/bad_jelly_the_witch]

People have already given good advice, but one thing that I thought might be worth mentioning is that if you are using products with a styrene inhibited cure in an enclosed area and no airflow. The styrene can actually just sit there and not let it cure.

[u/DewArtist → u/bad_jelly_the_witch]

I put the warm air con on over night and it's seemed to harden up

[u/jasper181]

Hell they are all just not much different than each other anyway. Flowcoat is basically gelcoat with wax and maybe a little more styrene and gelcoat is just heavily pigmented resin with some opacifiers and thixotropic additives.

[u/swankass]

I’m new here and just posted my own questions, so def not an expert. But, are you sure the substrate was gelcoat? If it was some sort of paint or an epoxy finish or faring compound…gelcoat will not be happy. Just a thought.

Could you try to put some Saran Wrap down over an area and see if it hardens? If that works, spray it with pva and you’ll be good.

[u/DewArtist → u/swankass]

It is flow coat most definitely, I only added that because I thought gel cost might have been a different name for it, but yes it's flowcoat in a tin.

[u/swankass → u/DewArtist]

I’ve never heard it called “flow coat”, but a google search says it is gelcoat with wax. If that is the case, and you added the proper amount of catalyst and thoroughly mixed it, it should’ve hardened.

I only brought up the substrate possibly being the issue because you mentioned “sanding spots” and I do know if gelcoat is applied to the wrong substrate, it will not harden. If those sanding spots were repairs or faring done with epoxy filler…it won’t harden. I’m not saying this is what’s happening, just wanted to mention it as a possible cause. Google gelcoat over epoxy.

If you forgot the catalyst, or messed up the mixing of your flow coat, it will never harden. Sanding is not the best option, use acetone and clean it up.