Bottom Paint

[FlimFlamII]

I'm sanding off the old antifouling coat and what's left of the I'll old barrier coat. I believe the brown is the old barrier coat. you can see signs of plenty of blisters but they seem don't seem clear up rather quickly. you can also see spot where the gel coat is gone and the go glass exposed. the cream and tan colors are prviouky applied epoxy fairing compound.
at this point I'm thinking to sand through the old barrier coat, apply some fairing compound where needed, apply barrier coat and bottom paint and call it good for a few seasons.
the boat is in a fresh water lake in northern ID.
thoughts/suggestions?
thanks!

 

[dLj]

Photos would really help. That being said, from your description I'd likely be looking at doing either a good epoxy barrier coating or replace gel coat. Without photos on way I can comment on filler.

dj

 

[FlimFlamII]

Yes, pics do help... My understanding is that Once I get the bottom "cleaned" I really don't need to worry about the exposed glass as long as I use an epoxy barrier paint. Do I need to sand off all the pervious barrier coat?

 

[dLj]

You just need to get to a smooth, stable base. You don't have to remove the entire previous barrier coat. An epoxy barrier coat is not the same as epoxy paint, at least to my knowledge. I don't know what an "epoxy barrier paint" is. Last time I did an epoxy barrier coat, I used West System epoxy with the 422 Barrier Coat Additive. I understand there is also an interlux product that is highly regarded, I haven't used it so can't speak to it.

I can't tell what the dark discolored areas are in your photos. If it were me, I'd want to know what that was.

dj

 

[shemandr]

Assuming that you plan to sail this boat in the upcoming season, I wouldn't sand the whole bottom thru the existing barrier coat or Gel coat. Portions of that bottom look fine. I would take all the anti-fouling paint off. Sand to smoothness areas in which the barrier coat is intact. Remove barrier coat where it isn't sound. I wouldn't remove any gel coat unless necessary - like in the case of blisters. Fair, apply barrier coats, smooth, apply bottom paint and go sailing.
I agree that you don't need to worry about exposed gel coat that is properly covered with barrier coats.

 

[lehighsail]

Is this really Jackson Pollock asking?

 

[FlimFlamII]

do I need to remove the previous areas where they used an epoxy fairing compound or just make sure they are "clean"?

 

[FlimFlamII]

The brown is old barrier paint and the cream colored areas are epoxy fairing compound.

 

[jssailem]

Do I need to sand off all the pervious barrier coat?

apply barrier coat and bottom paint and call it good for a few seasons.

It sounds like the intent is to do minimal necessary work to the bottom to allow a season or two of sailing before your "refinish" the boat bottom.

Unclear if this is just to sail around the lake or that you want to optimize speed for something like racing. The references to "Smooth", "Fairing" and "Sanding" are what generates confusion.

You will need to sand the bottom areas you want to paint with an epoxy barrier coat. This is not about smoothing the surface it is about removing ablative paint that will not let the epoxy to bind to the bottom. It is about making the surface rough enough to allow the epoxy to mechanically grab the bottom. That is why we use 80 grit paper in our sanding and not 400 grit.

You do not need to remove barrier coat if it is a hard coat (not an ablative) and it is properly adhered to the boat hull. (Doing paint over flaking paint - both new and old will flake off.)

Once prepped and wiped down with solvent, you can paint with barrier coat and then paint with bottom paint. This will give you, your couple of seasons usage of the boat.

 

[FlimFlamII]

Assuming that you plan to sail this boat in the upcoming season, I wouldn't sand the whole bottom thru the existing barrier coat or Gel coat. Portions of that bottom look fine. I would take all the anti-fouling paint off. Sand to smoothness areas in which the barrier coat is intact. Remove barrier coat where it isn't sound. I wouldn't remove any gel coat unless necessary - like in the case of blisters. Fair, apply barrier coats, smooth, apply bottom paint and go sailing.
I agree that you don't need to worry about exposed gel coat that is properly covered with barrier coats.

remnants of blisters appear in old barrier coat. the ones I've sanded dissapear either when I sand through the barrier coat. I wondering that if I need to sand them all down to the gel coat even if they have no loose edges? I hope this makes sense.View attachment 192142View attachment 192143

 

[jssailem]

One of the best documents I read when dealing with blistering on my boat was this work by David Pascoe.

Boat Hull Blisters - Avoiding The Blister Blues: Marine Survey Articles by David Pascoe, Marine Surveyor

Good Detection and Communication Techniques Critical to Avoiding Complaints

www.yachtsurvey.com

Boats in the water for long periods of time, especially boats made of fiberglass form the early 80's, have the possibility maybe even the probability to develop blisters. It is a result of the changes in EPA requirements for fiberglass resins and the skills of the boat builders of the era.

Many ways to "really" deal with them have been considered and promoted. All are expensive and or time consuming.

You really need to consider what you want to do with your boat.

 

[Davidasailor26]

An epoxy barrier coat should be waterproof and not subject to the same type of blistering as polyester gelcoat. Is there any moisture in them?

Its possible that the barrier coat was laid up while the gelcoat was still moist, allowing blisters to regrow underneath. If that’s the case then you’re probably right to sand off at least those parts of the barrier and reapply. Otherwise I wouldn’t bother removing any barrier coat that is still well adhered.

 

[sailme88]

Never heard of brown barrier coats. It looks like tannic acid stains. Barrier coats are usually applied with a minimum 4 coats, and alternate between white and gray so you can judge the coverage. System 2000 is just one of the systems. You should get all paint off, fair out all blisters and then two part barrier coat.. When the last coat is still tacky, apply your first bottom paint of a different color than what you intend the finished hull color to be..

 

[FlimFlamII]

An epoxy barrier coat should be waterproof and not subject to the same type of blistering as polyester gelcoat. Is there any moisture in them?

Its possible that the barrier coat was laid up while the gelcoat was still moist, allowing blisters to regrow underneath. If that’s the case then you’re probably right to sand off at least those parts of the barrier and reapply. Otherwise I wouldn’t bother removing any barrier coat that is still well adhered.

The boat was hauled out las fall. There was mositure in the blisters at the time. It doesn't appear that there is much of a barrier coat if there was ever one at all. It's pretty evident that that the last two times antifouling was applied it may have needed a new barrier coat but it never happened. The small blisters clean up easily. For many I've barely had to sand away the gel coat before hitting clean glass.

 

[FlimFlamII]

Bit the bullet and sanded down to the gel coat/glass. Turns out that somewhere along the line bottom paint was applied directly to the gel coat lots of faring compound over that. Only two small blisters penetrated into the glass.

Next question, it will now sit outside until the weather warms up enough to apply the barrier coat and bottom paint. Is there any risk to absorbing water during intermittent Spring rains?

 

[jssailem]

Your boat is not a water magnet sitting under a cover. When it begins to warm up and the humidity declines your boat will be ready to epoxy and seal the bottom.

You can and should check the moisture of the hull bottom before you begin the painting.

 

[FlimFlamII]

Your boat is not a water magnet sitting under a cover. When it begins to warm up and the humidity declines your boat will be ready to epoxy and seal the bottom.

You can and should check the moisture of the hull bottom before you begin the painting.

Forgot to mention that it will not be under cover. Yard needs the covered space.

 

[jssailem]

Time for a waterproof tarp. A big one. Think of it as a portable cover.

Used them winters here in the PacificNW.

 

[Davidasailor26]

I wouldn’t worry about the moisture from rains. Rain would keep the gelcoat from drying out if it was already saturated, but water just running down the hull shouldn’t cause the kind of constant pressure that sitting in the water does. Some boats without barrier coats even routinely sit in the water for years without blistering, so intermittent rain should be ok. Like jssailem said you can pick up a moisture meter for piece of mind if you want to track the levels.

 

[FlimFlamII]

Finally finished sanding down to the gel coat/glass and started to put on the first barrier coat. As I was painting pin holes began to appear in the gel coat. They were not noticeable before painting or after I blew the bottom with an air compressor and wiped it down with acetone. Are they cause for concern or will the barrier coat, three applications, take care of it?