Trying my hand at gel coat

[BOWTECH.JUSTICE]

I'm fixing gouges and scrapes on the boat bottom. Due to the repairs and the dullness of most of the bottom, I've decided to try my luck at re gel coating the entire bottom. I am using the evercoat premium gel (unwaxed). My question is- I've already sprayed a couple coats on and the unwaxed gel doesn't need to be sanded between coats, so how long can I go from putting a coat on until I do another? I understand the factor of dirt and particles floating around but do I need to worry about adhesion to the previous coat if I don't get on it within a couple days?

 

[Georgesalmon]

Yup, you should allow less than 16 hours between coats. Zactely the same as you would for polyester resin because all gelcoat is, is polyester resin with pigments and some other stuff in it like thixotropic agects and UV inhibiters.

 

[Rickmerrill]

If you can make a long day of it you should be able to get several coats on. Spray, wait till starts to tack, spray again. Anyway, just a thought.

Trooper82 went a few rounds with gelcoat http://forums.iboats.com/forum/boat...nd-hull-repair/537653-78-ebko-lebaron-therapy

and so did Decker83 http://forums.iboats.com/forum/boat...k-boat-transom-deck-stringer-replacement-help

Please keep us updated on your progress!

 

[BOWTECH.JUSTICE]

So what happens and what's a guy to do if it sets a couple days between coats?

 

[Woodonglass]

What's the temps been? How long HAS it been?

If it's still a bit tacky, and it prolly will be, then Scuff it a bit with 40-60 grit (Paper will clog like crazy so you'll need a lot) then wipe down well with acetone and shoot it. Your bond won't be as good and you may have issues later own but it's all that you can do! As previously stated, with any Polyester based product, it's ALWAYS best to do "Wet on Wet" applications to get the best bond between layers.

 

[Rickmerrill]

You might consider hitting it with PVA, let it harden then scuff.

 

[Woodonglass]

Uhmmm I wouldn't advise this ^^^^, You'll have a better chance of getting a chemical bond if it's not fully cured. The PVA will cure the resin after a period of time and then there's NO CHANCE of the two layers getting a chemical bond.

 

[Rickmerrill]

Ok, I was just trying to save him from the gummy sanding and I would think a good mechanical bond should work. I figure the first layer was a mechanical bond but I guess if there is some chemical bond to be had might as well go for it.

 

[BOWTECH.JUSTICE]

Well, one good thing is that what I've done so far is just big enough for experimental purposes and not the whole bottom. Experimental as in ratios and how much I can do at a time. It's now been 3 days and the temps in my shop today are in the 50's. I thought I had read somewhere that since it doesn't cure without the PVA, I didn't need to be in a rush. I'm still learning (obviously). I am to the point now that I'm ready to do the whole thing but sounds like I need to do more prepping on what I've already sprayed. I will say that what I have done so far looks good but it's not completely covered so I guess I need to take a couple steps back. Thanks guys, I will try to keep updates coming.

 

[BOWTECH.JUSTICE]

And one thing, I had thought about doing the curing thing and then sanding, so what is the difference between doing that and sanding the original surface and spraying onto it? Thanks

 

[Rickmerrill]

Yeah that was what I'm thinking, weakest link and all that. When repairing, the first layer is going to going to be applied to old,cured glass so we are going to have to rely on a good mechanical bond somewhere down the line. But, when gelcoating I wouldn't cheat the gods of fate if I could avoid it so I'd go wet-on-wet rather than letting each coat cure, sanding and then applying the next coat. It may work out fine but if it didn't the consequences might be nasty.

Can you keep the temp above 60 while you're spraying and for a couple of hours after? I wouldn't do anything with polyester below that.

 

[BOWTECH.JUSTICE]

Yea, I can keep the temp up when needed. That's just the temp now as I haven't been out here for a couple days. This is very new to me but I'm the type that's always up to trying something new and this boat is a good experiment boat. 1992 celebrity. It's in good shape but it does need some touching up like this job. I'm just doing the bottom for now, that way if it goes bad only the fish (and I) will know. I did just try some sanding, sure enough it started gumming up. So I have some work to do.

 

[Woodonglass]

It's REALLY important that you keep the temps above 60 for 3-4 hours while applying the Gelcoat. Once it tacks up you can let it drop down but not until it tacks. As stated before Gelcoat is primarily intended for use in Mold applications so when us DIY'ers do it on Glass boats we start in a bad situation already. What you have done has complicated it double. I fear you may have issues down the road but time will tell.

 

[Rickmerrill]

Hopefully it will all work out for the better. Besides, once you've started the sanding phase this will just seem like a distant memory. Please take some pictures and keep us up to date, we all learn together.

 

[undone]

PVA only helps during the initial curing phase, once the gel coat has cured to a point where the surface is the only tacky part it has already been air inhibited and it won't help much if any. But it will make a mess.

If the surface is still a bit soft, if you can dig a fingernail into it, or it feels gummy, you can spray over it. Don't wipe it down with acetone, you don't want to remove that tacky layer.

With low temps the chance of it curing thoroughly is slim, so that helps in this instance.

 

[Rickmerrill]

On second thought, and it's totally your call, you might consider spraying PVA on it, let it harden, sand it all off and starting over. Guess it just depends on how much you have to remove, if you have enough material left to do that and how much of a perfectionist (scaredy cat) you are. I remember trooper82 had some sand through issues so try to get enough material on to avoid that but I have no idea how thick it should be. Remember, you are treading where few dare go so be careful and patient but the results can be amazing!

 

[BOWTECH.JUSTICE]

Ya, I seem to be good at doing things the complicated way.
So, it really doesn't look bad the way it is so I'm thinking I may put the PVA on and let it cure. The areas I wanted to repair are covered so that's good. As it stands right now, I let it cure and finish sanding and buffing, what's the worst thing that can happen? It will just peel off, correct?

 

[BOWTECH.JUSTICE]

One thing about me is I'm not too afraid to try things. Doesn't always work out for the best but when it does, it's pretty satisfying. I'm gonna sand it down and re do it as I'm doing the whole bottom. I've already learned what not to do so hopefully things will go better as I move on.

 

[Woodonglass]

Uhmm it's to late to put the PVA on to make it cure. PVA is to be sprayed on just as the Gelcoat begins to tack up. Since its been several days it will actually do no good to spray it on now. Gelcoat is Air Inhibited cured. The PVA forms a Plastic Like barrier which blocks the air and allows the GC to cure. Since air has been allowed to penetrate the Gelcoat molecules for this long period of time it's not gunna happen as intended.

 

[Rickmerrill]

Thanks undone and wood I learned something today! I was figuring if you could block the air it would cure (head slap).