No gelcoat under waterline

[Chotu]

I have the complete petite system on mine. Epoxy primer (for adhesion only, since entire boat is epoxy) and bottom paint.

Has held up nicely but lots of ablative paint gone due to passage of time. Primer still fine

[JSSailem]

Nautix? A French based company focused on marine paints for yachting market. Been around since 1980’s

They sound like a reasonable European based source for the project you have. I have not used their product. Ask in your area about the product performance. Sounds like this is a product used by the marina yard. What warranty do they give? It will tell you a little about their belief in the product quality.

How long before you plan to look again at your bottom. 3-5-8 years. I suspect most of the bottom will be good if good preparation is done. Adequate layering is applied. If in the water constantly even then there will likely be a few small blisters. It is the nature of plastic boats in water. In wood boats it is rot and worms.

[Laxlife]

You need a barrier coat to seal the West System epoxy. If Nautix is a barrier coat formulation then that qualifies for your situation. If it is just an epoxy primer that is not the issue which a barrier coat addresses. Also are you certain the bottom peel was rebuilt with West System epoxy? A vinylester resin seems more appropriate for this kind of bottom job. I wonder if you can sample the bottom and determine whether it’s epoxy on Vinylester. Either way whatever I was used needs to be sealed with a robust barrier coat. interlux’s 2000 is a top barrier coat solution but they typically recommend 5-7 coats not 3-4. It’s expensive stuff for sure but you need to seal the bottom job or osmosis could reoccur.

[CaptainRivet]

I done the whole underwatership restoration myself on my Lavezzi supervised by a very well known fibreglass expert. I used binelester resin as easier to work with rhen epoxy and the binelester i used (organized by expert) is stronger then west system.
On epoxy you can use binelester oder epoxy resin but why do you need that if the whole underwatership was sealed with epoxy. So if you need to do some additional sealing i suggest to use binelester resin as yo have a bigger window for curing and its more tolerant to mistakes then epoxy.
To fair i highly recommend to use jotun megafiller multi, best for the buck and easiest to work with.
On top if that 2 laywer of international majestic thick primer. Thats your 2nd barrier coat after epoxy/binelster.
On top of that right away use 2-3 layer of International light primer. All painted after each other so you don't have to sand.
The light primer is your isolater and working surface you apply antifouling on, if you take antifouling off next time you will first reach the ocker colour of light primer so thats where you have to sand back to. No problem if you sand through to grey thick primer but now you have to stop. Light primer is known for excellent base and every antifouling sticks to it.
Yes there are other brands and they have good products to but what i mentioned is a whole combination of products thats optimized for this job and ease of use/working with. I know i done it myself. The fibreglass expert fixed 80000Euro damage inside and the insurance surveyor was very impressed with his work, never saw that quality in the last 20years...
So if you don't get the brands mention i highly recommend ordering them and ship it as this is a very poven and most cost effective material combination for maximum protection for the smallest buck possible and best to work with too.
I had to work with a different filler as we sourced too less...well after 2 days i decided to make better 2 weeks break and wait for the megafiller to arrive. Lessons learned. I need triple time to sand this patch and surface sucked too.
A very helpful tools for sanding is the electric flexible sanding board and the 1.20m fairing board you can get from www.flexisander.com
With this i was able to get a perfect surface very quickly, my expert right away bought one as he didn't know this product but saw me and the speed i got 2 40ft hulls faired.

[b.needalman]

It may be worth the time and expense to apply InterProtect. It takes at least four coats to provide osmosis protection. Comes in two colors, white and gray, to help avoid "holidays". Or was that the "treatment" you mentioned?

As others said, gelcoat is not needed in areas covered by bottom paint.

[CaptainRivet]

Originally Posted by b.needalman

It may be worth the time and expense to apply InterProtect. It takes at least four coats to provide osmosis protection. Comes in two colors, white and gray, to help avoid "holidays". Or was that the "treatment" you mentioned?

As others said, gelcoat is not needed in areas covered by bottom paint.

International thick primer majestic is better, cheaper, easier to apply and 2 coats are more then enough on top of epoxy as barrier coat and additonal protection in case of defects in the epoxy layers.
You don't have to use light primer as i suggested but for longlasting and easy maintenance afterwards i highly recommend it.

[Flemming Torp]

On my X-342, I have been using International VC Tar2 as my epoxy primer and International VC17 antifouling over the last 15 years. Sailing in Nordic waters.
It is easy to work with. Gives a nice, smooth surface. Easy to maintain, and does not add layers over the years.

[alanrosens]

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?

If there are no blisters or voids just antifouling bottom and relaunch.sent

[Motco80]

Thank you all for your information share.
Appreciate it a lot.
Im will probably go for 5 coats of “international “ interprotect.
Due to immediate existence in the marina.
Because of the keel is already covered with hemple epoxy primer(due to storage on dry dock in the winter)
I wonder if i can apply different epoxy primer on the existent hemple covering the keel.
About the vinylester that was recommended here, they got polynt brand.
How many liters needed for a 10.65 meter long
And 3.65 meters beam length boat?
And is it essential?
Thanks in advence.

[neilpride]

If you are going to apply Interprotect on top of Hempel epoxy primer you will have to sand it to give it a good grip.

[Disailor]

The water may have dried out but salt crystals will remain & will draw water. Best to flush with water (hose pressure is fine). Blister spots can be further dried with rubbing alcohol or acetone.
My boat had a serious blister problem. I used 2000e & Ten years now blister free.

[OneBoatman]

Being that the osmosis treatment was done with West System I would address any localized areas that need attention with West System or Mas epoxy. If the bottom paint has been removed such as by soda blasting, fill and fair trouble areas first with epoxy and then apply another coat or two of a quality two part epoxy all over. You want to use one with either a medium or a slow cure catalyst and only mix what you can apply within the pot life. Stay within all application limits if you are applying multiple coats unless you plan on doing much sanding between coats. An older relatively narrow beamed 35 ft monohull from the 80's will take roughly 1 1/4 gallons to cover one time if it is very smooth. Once your hull is covered in epoxy and it is suitably smooth there are plenty of modified epoxy bottom paints that will adhere directly to epoxy just fine. Otherwise follow the bottom paint mfgr's recommendation if they suggest you must use a primer compatible with their paint chemistry.

[Motco80]

Where i am now i dont have the west system.
You think if i use another beand on top of it it will be bad?

[CaptainRivet]

Can you explain why you want to do what and what you wanna achieve?
Its actually nowhere e plained.
Osmosis treatment badly done?
Or surface just bad?

On the keel has already hempel on it, whats the problem with it, why want you apply more above it.

I have it done all myself from a sandblasted firbeglass surface till copper coat and supervised by an excellent specialist.
Read my post above, don't just buy whats avaliable, you can order and get the right products shipped.

Sorry it was Hempel Majestic Thick primer (thats what the pros using) , 2 layers is enough and better as 5 layers expensive interprotect. Good product but very expensive. And applying 5 layers cost time. 20l majestic is good for 2 coats on 65sqm of hull surface (underwatership 40ft cat Lavezzi). The majestic does also a barrier coat to all whats underneath, the while surface need to be sanded and properly cleaned before, use 98% Alcohol for final cleaning and no Oil based cleaner like Aceton. Paint in the late afternoon evening first coat and in the morning next 2 day 2nd coat so no sanding needed.

[OneBoatman]

Ans. concerning compatabilty with other brands of epoxy resin systems, if you have an internet connection which it seems you do, just access the mfgr's MSDS (material safety data sheet). Read the major constituents and you will be able to tell if it is a poly amine type epoxy. The wt percents stated for the main chemicals will also likely be in the same ballpark. The companies that produce these products tend to clone each others chemistries. Mas makes a good one but I'm sure there are others. Good luck.