No gelcoat under waterline

[Motco80]

Hello
I have an 1981 sailboat(Jeanneau)
That had an osmosis treatment 8 years ago.(not on my ownership)
During the treatment, all the gelcoat was sanded off all the way until the fiberglass, and after the hull was dry enough, they applied west system epoxy with out gel coating.
Now im on the dry dock after sanding old antifouling and I noticed there is no gel coat.
Can i just make 2 layers of epoxy primer and filler and then antifouling, or i must sand it all to the fiberglass and make gelcoat?

[rslifkin]

Epoxy primer and bottom paint is perfectly fine. There's no need for gelcoat below the waterline where it will be painted over anyway. The only reason it's there to start with is because it's easier to just gelcoat the whole thing during production.

[Motco80]

Thank you so much for fast reply ��
How many primer coats and which brand do you recommend?

[Motco80]

And also, is it possible to make 2 layers of fiberglass on top of old epoxy?

[neilpride]

Once they have removed the gelcoat and applied epoxy, there is no way back, you can't apply gelcoat on a bottom with cured epoxy , you can apply epoxy primer and antifouling, anyway ,I suspect they had done a good job with West, if you want a brand that works very well, Interprotect 2000E, with 2 or 3 coats you would have enough, if you follow the instructions to the letter, including the curing window to apply the antifouling when the last coat of primer is almost cured, so you can avoid sanding.

[Motco80]

Thank you too for your reply!
The marine shop edvises me to use nautix for the epoxy primer, filler, and antifouling.
Do you know this brand? They are good?

[more]

Originally Posted by Motco80

Hello
I have an 1981 sailboat(Jeanneau)
That had an osmosis treatment 8 years ago.(not on my ownership)
During the treatment, all the gelcoat was sanded off all the way until the fiberglass, and after the hull was dry enough, they applied west system epoxy with out gel coating.
Now im on the dry dock after sanding old antifouling and I noticed there is no gel coat.
Can i just make 2 layers of epoxy primer and filler and then antifouling, or i must sand it all to the fiberglass and make gelcoat?

gel coat is worst ever human made layer. need polishing evry year,need wax for filing micro crack,not 100% waterproff. but is cheap,very very cheap under 0,1% what be cost of proper painting and becouse cost ship builder use them.

but if you buying new boat light sand boat and paint deck,hull. underwater you must paint of course.

[capt jgw]

Originally Posted by Motco80

And also, is it possible to make 2 layers of fiberglass on top of old epoxy?

Sure, using epoxy resin. Polyester resin does not reliably stick to epoxy. Gelcoat, being modified polyester, doesn't either. Once epoxy, always epoxy. Epoxy's better anyway, just more expensive.

[Motco80]

what about nautix?
anyone has expirence with them?

[Jenta]

Not wanting to start a debate about it, but since it has been said that you can't ever put gelcoat over epoxy I wanted to offer that it is not always the case according to other sources and my own experience.

True, you do need to prepare the surface properly and one of the major steps is removing the amine blush which is very easy to do with just water and a scotchbrite pad. This step would not apply to "old" epoxy as you are dealing with but only when laying up fresh epoxy resin. You're only going to be getting a mechanical bond on old epoxy but the same would be true if you were putting a new epoxy layer over an old epoxy layer.

Boatworks Today on YouTube has done some great videos on it including testing but there are several videos out there.
https://www.youtube.com/results?sear...oat+over+epoxy

This would apply to more than just gelcoat of course as any polyester or vinylester resin product would be the same.

I would totally concur though that there is absolutely no benefit to putting gelcoat where there is none under the waterline. Gelcoat is porous to water which is why it needs to be painted/sealed under the waterline so you could be causing more work for yourself. Epoxy itself is not porous so in reality you don't even really need a barrier coat between epoxy and bottom paint - though I still do and would.

I think an epoxy based barrier coat will still give you better results going on first prior to your antifouling as has already been suggested.

[capt jgw]

About polyester over epoxy: yes it can be made to stick, but not as reliably as epoxy. Poly is a great media for laminating fiberglass but it's not a particularly good glue. Epoxy was invented as a glue long before anyone thought of laminating fiberglass with it. It does both extremely well. Laminating glass on cured epoxy may or may not last forever, epoxy probably will.

[Motco80]

Thank you all for your replies.
Appreciate it.
So I guess i will go for epoxying the buttom with filler where needed and then epoxy primer and then antifouling.
Please advise me for the best materials for this job from your experience.

Here i got advised for nautix…
Any thoughts?

[Jenta]

I have no experience with or knowledge of Nautix.
Are you in Europe or something? Looks like they are a French company.

I've not done an entire bottom with barrier coat - but several large areas where I've removed through hulls or done other repairs and have used TotalBoat TotalProtect and had good success with it and easy to mix/apply. The last antifoul I've used was Pettit Odyssey HD Ablative and I did a total of 3 coats and that has done very well. Your barrier coat and antifoul shouldn't need to be the same brand. There are compatibility charts for antifouling over other antifouling - so that needs to be paid attention to if you're not removing all the old antifouling paint.

We've only been on the boat 4 years though so there will be plenty with more information than I have. But I get the feeling that for the most part it is kind of like anchors. Essentially, picking a modern anchor design is important, which exact anchor not so much. If you are always only in a certain area, you should see what people in that area are using and maybe lean towards that. If you move all over the place then that is much less important.

[Motco80]

Yes im in cyprus.
They use here mainly international or nautix.
Thank you for your reply!

[Chotu]

It is very early and I just woke up. But I’m not understanding one thing. Why? Why are you doing any of this?


If you already have epoxy over the polyester boat, why are you trying to add more?

Are you just talking about putting an epoxy primer (paint) on there so that the bottom paint sticks well?

You mentioned filler. Why would you need that?