Barrier coat

[Scott Dunsworth]

Probably a question for Graham, but is a barrier coat under the bottom paint a waste of time and money for a epoxy boat that will stay in the water? I can under stand its usefulness on a fiber glass boat, but is it a good investment on a epoxy boat?

 

Scott

[Oyster]

Well having used the Interprotect 2000E since the 80s on big boats and clamming skiffs, well worth every penny twice over.

[Hirilonde]

Check the instructions for the bottom paint, or even write to their product support.  But no barrier coat is going to be more waterproof than epoxy.  The only reason I can think of to use it is a matter of adhesion, and I don't know that it would help any.

[Oyster]

Check the instructions for the bottom paint, or even write to their product support.  But no barrier coat is going to be more waterproof than epoxy.  The only reason I can think of to use it is a matter of adhesion, and I don't know that it would help any.

Well you need to read up on the Interprotect a bit. There is a reason why it came about from the start and that was to seal polyester resin hulls. But not only does it deal with moisture, its a great alternative product for filling glass while also protecting glass. If you use finish cloth even over any biaxall glass, you can use it as an initial fairing, as long as the bulk of the hull is fair from the start. You can roll it right on the green stage resin if you are not using some of the resins that blushes a lot and skip a step of sanding too .

Oh the thoughts on epoxy being waterproof, well its more along the lines of being water resistant but not waterproof. Epoxy does not have the on going post cure like polyester resins, which is the reason why polyester boats gain weight while the gelcoats spider crack too, and needs to be waxed to minimize a lot of the issues over time with the effect of dampness creating the issues with production type hulls built with polyester resins.

 

http://www.wholesalemarine.com/p/ILX-2000Q/Interlux+Interprotect+2000E+Epoxy+Marine+Barrier+Coat+Kit%2C+Grey.html#readmore

[Hirilonde]

I have read extensively on Interprotect and I think it was developed to make money.  I think it is a total waste of money on polyurethane boats with the possible exception that you are using it as a high build primer.  You will never completely seal an existing old fiberglass boat because you can't get everywhere inside.  So a boat kept in the water 6 months or more during the year will always contain some moisture and I don't think it makes much difference that it does.  My 1967 Renegade has been bare glass/resin in the bilge since it was built, there is always a little water in the false keel and I have no issues at all with bottom paint sticking or any other moisture related problems.

 

For new construction you are going to sand your last fairing coat, what ever it is.  The only question left as I see it is if you need a primer for the bottom paint or not.  If you do, then Interprotect is a good choice as you can hot coat it with bottom paint and skip another sanding.  But many bottom paints can go right over epoxy, so why spend more money?  If you need more material over the wood, then you stopped coating with epoxy (neat or with filler) too soon.

[Oyster]

I have read extensively on Interprotect and I think it was developed to make money.  I think it is a total waste of money on polyurethane boats with the possible exception that you are using it as a high build primer.  You will never completely seal an existing old fiberglass boat because you can't get everywhere inside.  So a boat kept in the water 6 months or more during the year will always contain some moisture and I don't think it makes much difference that it does.  My 1967 Renegade has been bare glass/resin in the bilge since it was built, there is always a little water in the false keel and I have no issues at all with bottom paint sticking or any other moisture related problems.

 

For new construction you are going to sand your last fairing coat, what ever it is.  The only question left as I see it is if you need a primer for the bottom paint or not.  If you do, then Interprotect is a good choice as you can hot coat it with bottom paint and skip another sanding.  But many bottom paints can go right over epoxy, so why spend more money?  If you need more material over the wood, then you stopped coating with epoxy (neat or with filler) too soon.

Well say what you wish. But when the pinhole and blisters all came to light, many of the big time production boat manufacturers were paying for the underwater redos and this is the direction that they went, and this came with huge liabilities costing them big time. If the product was a bunch of marketing manure, then why did the boat manufacturers go that route while also guarantee the redos.

 

But I started with the system back in the mid 80s and stand by my obeservation. I can also personally speak from experience and can personally show you an 18 year old hull that rarely if ever gets bottom paint on it, which got the system on it too. Not one issue, But have it as you wish, but there are literally hundreds of new boats and their builders using the system which also comes with big liabilites. Pure epoxy under water is not water proof and at best water resistant for a short period of time by comparison. The microplates thats in the Interprotect is just one step above and has stood the test of time.

 

Oh no paint type primers are waterproof. The reason that these are called primer is both that they build the surface up and also allow a surface to grab and receive a topcoat when being prepped. But have you ever witnessed topcoat painted hulls placed in the water for any time and not blister? Bet not..

[Tom Lathrop]

Perhaps a look at what Interprotect is might clarify this issue a bit.  Basically Interprotect is epoxy with a metallic flake additive.  What the metallic micro flakes do is to make the path for moisture through the coating much-much longer so it take far longer for moisture to get through a given thickness of coating.  Since the metal flakes are essentially impervious to moisture penetration, it stands to reason that this makes it better than plain epoxy as a barrier coat.  I mostly use plain epoxy because few of my boats live in the water full time.  I have used a flake added barrier coat and found it not only a superior moisture barrier but a mechanically superior abrasion coating.  In that sense, I don't consider it to be only a primer but a final coat unless UV protection is needed.

 

Whether Interprotect is worth the cost is probably an issue for the individual and their intended use of their boat to decide.  In critical situations, I would use it.

[Oyster]

Approx two hundred bucks to mentally think that I will not be crawling back under the boat with a potential of flacky bottom paint is enough for me to paint it now looking down on the hull and while its in the building stage. As i age and forget a lot of things, for some reason those mental pictures remain the same today as I type this. The amount of additional costs is nothing to the overall cost of the project not figuring the labor involved.

And I must add I am a dumpster diving boat building materials guy and shop at big box stores seeking out appropiate marine type building materials, making me one of the cheapest boat bums I know of. But this is not an area that I personally scrimp in at all.

[Scott Dunsworth]

Thanks for the opinions, I tend to build a little on the over kill side of things. So I'll use the barrier coat if for nothing else than a cheap insurance policy. $200 is not cheap, but over the life of the boat it's only 40 cents a month  . Unless she ends up on the rocks somewhere she will out live me by five times.

 

I should have her ready for a skim coat of mico ballons after this weekend.

 

To turn the corner a bit and shift to bottom paints, my brother used micron extra on his Coronado 25. It seemed to work good in fresh water and salt both. He bought two gallons and had enough for three coats. He sold the boat after four years and it still didn't really need redone. The slime from the fresh water would wipe of with a sponge pretty easy. Anyone else used this paint?

I know everyone has their favorites for various reasons. Like I am super hard headed about top side paints, like any boat that I am planning on keeping will never have any one part paint anywhere on the boat, inside or out. I'm also in love with the Epifanes two part to the point I will not use anything else. Interlux two part seems to be as good but to me doesn't flow out as well when used with a brush. Proper paint prep is just to much work to settle for one parts, That's my hardheaded statement for the week. Some folks swear by the two part varnish, I'm going to try it for the first time on our 28. 90% of it will be sprayed.

 

Scott

[Hirilonde]

I use Micron Extrra and am very satisfied.  Unlike the old bottom paints it lasts as long as there is paint.  So if it hasn't worn off (it is an ablative) then it is still good.  And with a little care not to let it build up excesively you will never have hard sand your bottom to remove old paint.  If you can justify the expense coating the bottom with a trace color before your choice color, it will provide a tell tale for when the paint is wearing thin.  I have been able to skip a year and still have good protection that year.  It will wear faster at the water line and leading edge of the keel and rudder.  I coat those places then coat the entire bottom each year.  This seems to be a good annual program.  You may want to start with the wear areas then 2 coats the first year whether you use a trace color or not as part of the plan.  If you go with Interprotect I think you will find that the hot bottom paint coat needs to be done within 8 hours of the last coat of Interprotect, though coats of Interprotect can be hot coated as much as 2 weeks apart (this is 7 year old information, read the instructions for yourself).

[PAR]

Tint the first coat of bottom paint, by mixing in some very contrasting topside paint, just enough to significantly change the color. This will provide a wear guide/trace coat. I routinely add white to black, giving me a gray (takes very little white) or black to other colors to darken them dramatically, so it's obvious when you need more ablative paint. Ideally, tinting with another color of bottom paint is perfected, but topcoat will work if you don't use much.