Barrier Coat with Fabric

[smurphny]

Just hauled out to dry for a couple of weeks, strip the bottom, and tackle the barrier coat job that's been on the to-do list. Does anyone have experience doing an epoxy barrier coat with a glass layer? My boat has extensive crazing, common in a lot of boats of her vintage. It's starting to show through the still well adhered Awlgrip. The folks at West think 4 oz. glass would be the right thing to use to permanently fix the condition, right over the old bottom gelcoat and Awlgrip sides. I'm wondering if one of the other fabrics available might be easier to use/wet out/form and easier to fair out afterward. Also, If anyone knows of a better way of stripping bottom paint than a DA with a vacuum, would like to hear it.

[FSMike]

I'm in over my head here but -

If the gelcoat is in good condition why barrier coat?
Conversely, if the gel coat is in bad condition I can't conceive of putting new glass on top of it, much less on top of Awlgrip, without removing them. By the time you finish prepping those surfaces there won't be much left of them anyway.
I'm primarily used to hearing of barrier coats being put on below the waterline. Are you planning on doing this only above the waterline?

Perhaps somebody with more knowledge than me has a wiser opinion?

[casual]

IN 1990 I purchased a 1978 C&C 36.Survey showed 11 blisters,I had the boat yard put barrier coating on expensive.1 yr latter at haul out 6 blisters reappered.I at that time requested yard space and had the gel coat peeled after letting the boat sit for 8 months until dry by a moister meeter I repaired the blisters with matt faired and put 1 coat of west system epoxy on.This dried for 2 weeks I sanded and washed the bottom and laid on 4 oz matt with 8 more applications of west now 21 yrs latter I have had no blisters.I have had a few areas maybe 2 to 4 inches round where the matt seperated from the 1st coat of epoxy buy no moister intursion was evident.
Lot of work but wirth it.

[hellosailor]

"The folks at West think 4 oz. glass "
West Marine, or West Systems, the epoxy and glass pros?

If you mean the epoxy folks, they're usually right about these things. If you have extensive gelcoat crackling all through the topsides as well as below the waterline, and it really is the gelcoat not some "paint" that a PO put on the boat, they just might have the right alternative. When you say Awlgrip topsides...if that's just Awlgrip popping, I'd rather sand it off than doa glass job and then STILL have to do at least as much sanding again afterwards to refinish it.

You might look into bead blasting it, instead of sanding it. With the right media you can strip off almost anything without damaging the underlying material.

Gonna be a massive job to lay up all that vertical or upside-down fabric and then get a smooth finish on it, I'd be terribly reluctant to do it that way without knwoing why West thought it was best. (If that was WS, not WM.)

[sabray]

If the gelcoat is in good condition it is not an example of good or bad laminate condition. Water can permeate gelcoat with out blistering. Osmosis what you do not want to do if you are glassing over is do this on a wet hull. That's a lot of work to do poorly.if the laminate is on good shape soda blasting and barrier coat may be a better go. I think cost wise vinyletser is b;etter but it's been along while. Vinyl ester easier to use there is even viylester fairings compound. Also what is your hull lay up. If it's cores light old polyester epox and cloth maybe a better choice. Laminate condition moisture content layup schedule maybe a density test. No should be telling you how to repair this without knowing more then what you have told us.

[capngeo]

Originally Posted by smurphny

Also, If anyone knows of a better way of stripping bottom paint than a DA with a vacuum, would like to hear it.

Gelstrip - Your first step for a complete osmosis cure

[FSMike]

Originally Posted by smurphny

---- If anyone knows of a better way of stripping bottom paint than a DA with a vacuum, would like to hear it.

A DA with a vacuum in somebody else's hands?

[minaret]

x2 on the gelstrip peeler. I've peeled many bottoms with this tool. It is by far the fastest way to get to bare laminate. We used to do barrier coat with WEST epoxy many years ago, but now we only do it in severe cases where we've had to double-peel. It's pretty rare. We do the whole laminate and chemical bond the fairing compound all in one day, it's a nightmare job. I've done several in vinylester with duracote fairing as well, it's a little easier than epoxy but still a PITA. Unless you need to remove some laminate, don't go that route. If your gelcoat is good, have someone grind off the bottom paint down to clean gel and then use interlux 2000/2001. Use at least four coats, six is ideal. If you do the sanding yourself use a 36 grit 7" softpad setup. Dont sand any finer than 36, the 2000 will fill the grit profile in about 2 coats and it provides excellent tooth. If your gelcoat needs to go too, have someone peel it off, grind fair, apply 2 coats of WEST and slick the whole bottom with 407 for fairing. Once its fair, apply 2000. Dont forget the moisture meter, you need dry laminate. If you have a moisture problem, find a yard that uses the hotvac. I've seen many boats take 6 months or longer to dry out using conventional methods. Good luck!

[minaret]

Originally Posted by FSMike

A DA with a vacuum in somebody else's hands?

Anybody who strips bottom paint with a DA is asking for a bad back. Use the 7" softpad in a quick bubble tent with 36 grit. I can do a whole 50' boat in one day by myself if the tent is already built. It'd take a week with a DA. Use 3M Imperial Purple 36. Imperial green is good too, but the purple just rocks...

[GordMay]

WEST Systems has numerous free tutorials
➥ WEST SYSTEM | Use Guides
Including “Barrier Coating”
➥ Barrier Coating

[David M]

I would consider multiple layers of an epoxy barrier coat over a paint free hull whose gelcoat is not falling off either. Interlux 2000 is great for this. I quite frequently see Interlux 2000 going over hulls that have just had blister removal jobs. You will want to use a moisture meter to make sure the moisture content is low enough.

Cloth will never lay flat when you have to overlap it and it will look funky having had to fair over the overlap. There is always the chance of cloth delaminating because it is being held on with a physical bond and not a chemical bond like the rest of the layers of fiberglass of your boat. You are also adding weight to the hull.

[smurphny]

As mentioned, I have contacted West and have read the application info. Their tech guy indicated that as long as the underlying surface is sound and well sanded w/ 80 grit (I'd go even rougher)that a glass layer of 4 oz cloth would eliminate any future problem.

I don't know if any of you are familiar with the "spider web" condition on some of the boats of this era but the gel coat is not peeling or loose, not stress related, it's just extensively webbed with a maze of hairline cracks which, of course have trapped contaminates in them. It's was caused by a dissimilarity in expansion coefficients between the gel and underlying glass when Grumman/Pearson/Pacemaker etc. were experimenting with resin formulas at the beginning of the mass-produced glass boat age. I have tried on other boats (and this one's topsides) to use multiple coats of epoxy primer, to squeegee in West System before priming and applying multiple coats of Awlgrip but it seems these cracks will eventually (5-10 years) come through anything.

I am very worried about seaming as David has mentioned which is why I had hoped someone has done this. I'm thinking maybe laying on 36"-60" widths vertically, gunwale to keel, letting each one set and then carefully cleaning up the edges before butting the next might yield a flat surface with a bit of fairing (which would have to be done over the entire surface anyway). Wish there was a way to try it first.

The other option is to sand off all the old gel coat and replace it with epoxy or new colored polyester which is a big job but do-able. Getting an acceptable surface after sanding is my worry because the gel coat will not be uniform in thickness but I guess a couple of layers of hi-build primer would smooth it out. It's hard to duplicate what came out of a waxed mold once you start breaking the surface (hard for me anyway). Leaving the original smooth surface and using it as the base for a thin, uniform layer seems more logical IF the cloth can be seamed adequately. I don't think delamination would be a problem as long as the surface is clean and roughed up enough. What's more, the waterline will not be lost in the process. The waterline on this boat would be a real PIA to try to locate. It's not just a parallel stripe.

Interesting that Casual has done this with mat. I have found that trying to wet out mat when it's overhead is virtually un-doable. Light cloth would seem to be the only way to go as it can be wet out very quickly and easily and provides an easily fairable surface. Not trying to build a new hull here, just trying to eliminate the crazing and get a solid surface to work with. This hull has solid 2" of glass at keel, laid up w/ multiple layers of roving and mat and has at least 1/2" build-up at the thinnest spot. It does not seem to have been sprayed with a glass fiber gun but laid up by hand. It is very dense with multiple laminate layers any place I've ever drilled.

[David M]

I just don't see an advantage to adding cloth when what you have is structurally sound and can be made to look good again for a long time. This is especially true when this can be done for a lot less expense and effort.

[minaret]

I would be tempted to remove the problem gel as well. However, if you intend to laminate your whole hull as described, you might consider using Pro-set resin from WEST. It has a higher viscosity and wets out glass much quicker than 105. It is WEST System's laminating resin. For one layer of cloth either is fine though. I would use 2 layers of cloth as the weight is negligible either way. That way you have a little something to sand on when fairing, and you can butt the edges with no laps and stagger the butts. Works out much better for fairing. And you wont worry about the crazing coming back...

http://www.prosetepoxy.com/PDF/1%20L...ling_Guide.pdf

http://www.fisheriessupply.com/produ...ge=2&did=13785

[minaret]

Originally Posted by smurphny

I am very worried about seaming as David has mentioned which is why I had hoped someone has done this. I'm thinking maybe laying on 36"-60" widths vertically, gunwale to keel, letting each one set and then carefully cleaning up the edges before butting the next might yield a flat surface with a bit of fairing (which would have to be done over the entire surface anyway). Wish there was a way to try it first.

.

I've done this a lot. Stick to 36" and do vertical strips as you mentioned. You need a big crew, we often have 2 mixers/helpers per laminators, with 2 laminators per side. Acquire a mixing machine.

Fisheries - Product Detail

It will pay for itself. If you do the whole job, 2 layers with staggered butts, all at once with proset using medium or slow hardener, then you can chemical bond your west with 407 for fairing the next morning. Unless it's really hot where you are. I believe the laminating resin has an ultra-slow hardener as well, but that may require a post-cure. You want to chemical bond the fairing if at all possible. If you cant get a crew thats big enough to do both sides at once, do one side at a time. You can use WEST with fast hardener for the fairing...