Undercoat for Antifoul

[seadog30]

Hi All

I have just spent the last 2 unpleasant weeks cleaning off 6 or 8 coats of antifoul from my 30 foot bilge keel GRP ketch.

Some of the antifoul was loose, some worn through, and some just powdery on the surface. I have after rubbing down with 40 and 80 grade and scraping the loose off got down to a solid smooth surface. In some areas the prepared surface is down to the GRP gell coat and in others still showing anti foul.

The question is - can anyone recomend a barier primer coat to seal the old surface and prepare it for new coats of modern antifoul.

Thanks - Seadog

 

[Tranona]

Choose your anti fouling and use the recommended primer and undercoat. For example Primocon is recommended under International anti fouling and other brands of paint will have similar recommendations. My choice would be a Jotun antifoul with their primer.

 

[upcountry2]

Choose your anti fouling and use the recommended primer and undercoat. For example Primocon is recommended under International anti fouling and other brands of paint will have similar recommendations. My choice would be a Jotun antifoul with their primer.

+1 Jotun vinyguard, used it for years, just as good as Primocon in my opinion and half the price....

 

[captainJP]

i always use primocon as a barrier coat then i apply 2 coats of international micron which is copolymer antifouling, it will give you an even coverage, the way it performs will give you minimum paint build up as well, i have found that it works in the most harsh fouling area as well, which will keep the performance of your boat and you will get less drag, ive just brought mine from yachtmailchandlery.com they were very quick at dispatch and were really competive on price too, i also purchased my anodes at the same time which gave me next day foc shipping .

 

[sailorman]

Hi All

I have just spent the last 2 unpleasant weeks cleaning off 6 or 8 coats of antifoul from my 30 foot bilge keel GRP ketch.

Some of the antifoul was loose, some worn through, and some just powdery on the surface. I have after rubbing down with 40 and 80 grade and scraping the loose off got down to a solid smooth surface. In some areas the prepared surface is down to the GRP gell coat and in others still showing anti foul.

The question is - can anyone recomend a barier primer coat to seal the old surface and prepare it for new coats of modern antifoul.

Thanks - Seadog

blakes underwater primer or international promocon

 

[[3889]]

+2 for Vinyguard. Easy to work with and very resilient.

 

[CAPTAIN FANTASTIC]

Couple of coats of Jotun Penguard hb, followed by Hard antifouling, then apply eroding antifouling

 

[seadog30]

Thanks All

I will give the Jotun a try, I have used the international and Blakes before. The Jotun seems a better price.

 

[Jim@sea]

Whats wrong with buying a 2.5 litre tin (plus hardener) of a epoxy primer from a car paint suppliers, brush/roller it on and you have a really good base for putting antifouling on. ps really easy to apply and dries quickly.

 

[coopec]

I am just about to the point of painting my yacht below the waterline. To get to the recommended thickness of coating (10-12mil) you would need five coats of epoxy primer if you use car paint!

This subject is covered on the following link (just scroll down to "Barrier Coat 101")

http://www.epoxyproducts.com/barrier4u.html

 

[Jim@sea]

I am just about to the point of painting my yacht below the waterline. To get to the recommended thickness of coating (10-12mil) you would need five coats of epoxy primer if you use car paint!

Perhaps if it was car paint sprayed on, but this is ordinary epoxy paint which is used for boats, trucks and cars. I was told to buy it by the painter at the boatyard where my boat is. When its mixed its quite thick and when putting it on with a brush because it dries very quickly you can overlap. I doubt if Gelshield is any thicker because if it was you would not be able to roll it. I notice that I paid £19 for 1.5 litres of epoxy primer and £11 for a litre of epoxy hardner (plus Vat) which did my 24ft hull below the water line twice.
PS I am a great believer in buying things from a non boat supplier. Forinstance a friend has a Crane Hire business, the Marlow Ropes rep left a price list (for slings) but there was Multiplait warp used for anchors at 40% less than what chandlers charged.
PPS. My boat has now had 8 coats of epoxy below the waterline. Only because I enjoy painting and it reminds me of when I had a bodyshop and hand painted perhaps over 100 vans.

 

[gcostell]

Whats wrong with buying a 2.5 litre tin (plus hardener) of a epoxy primer from a car paint suppliers, brush/roller it on and you have a really good base for putting antifouling on. ps really easy to apply and dries quickly.

Hi, could you recommend any brand?

 

[Quandary]

Jotun Epoxymastic 87 is what many rustbeating companies repack in small quantities for resale, it is available in a wintergrade (which goes off very fast) and with extra aluminium which is nearly too high in solids. Penguard HB is easier to apply and is available with a winter additive. (To 10 C) When I took my hull down to the bare gelcoat I used two coats of the HB followed by one of Vinylester 88. I am convinced that Vinylester 88 is an even better primer than Primocon. I use it on everything, GRP wood metal.

 

[coopec]

" PS I am a great believer in buying things from a non boat supplier" Couldn't agree more!!!

Sounds as though you are using the same type of epoxy as what I want to use- quite thick. Ive read some people put their epoxy on with a putty knife and then spread it................?

 

[charles_reed]

Primocon - 5 coats recommended.
My memory is of metallic Primocon a horrible tar-mix with which one was supposed to prime steel and cast iron - always bled through.

I used 7 of Gelshield (it's more waterproof and dries faster) one coat of hard antifoul and then 2 coats of eroding antifoul. It has the dual advantage of osmosis proofing as well as priming.
Since then I've only put on a single coat of eroding antifouling to avoid a build-up which one then has to scrape off,
Using a contrasting colour of hard antifouling allows one to pick out areas of high erosion and put a 2nd coat of eroding antifoul on.

PS Recommended to me by a boatyard who mainly worked on superyachts - probably had far less expertise than those of us sitting @ home soaking up all of International Paints (aka Azko Nobel) technical literature.