Bottom Paint, primers, Barrier Coats

[wufibugs]

It is time to paint the bottom of the 1986 Hunter 31 I recently bought. I am assuming that the bottom is an ablative, and that this is a good paint for Southern California waters. I looked through the archives, which provided many different opinions, many tips, but left me somewhat confused.

1. I plan on using Micron 66 because it got a very good review in Practical Sailor's tests, which seems pretty objective.

2. I have not yet hauled the boat out, so I am not sure what was there. In the last 6 months the diver's notation about the bottom paint went from fair to poor. I am unsure if I should sand, apply a barrier coat, a primer, and then ablative paint, if that is overkill, etc. I want to get a very good substrate so that I can get several seasons of just repainting before I have to think about the substrate again.

3. I am planning on rolling and tipping two coats of paint.

 

[Ted]

And the question is...........

 

[wufibugs]

Sorry, I did not make that very clear: "I am unsure if I should sand, apply a barrier coat, a primer, and then ablative paint, if that is overkill, etc."

If the bottom is already ablative, I could sand and paint, I suppose. The question is whether I should prep with a barrier coat AND a primer, just one, or neither.

 

[Mark Ferrick]

It Depends

What you do depends on what you find when you haul the boat. Be there if at all possible. That way you can easily check for blisters. If no or very few are found, I would sand and paint. On my boat, I just started a similiar process, but I have blisters, so I will repair, barrier coat and then paint.

 

[wufibugs]

So the barrier coat is there primarily to deter blistering? How exactly does it accomlish that? I also read some posts debating whether the bottom paint should be "hot" painted, that is applied before the primer or barrier coats are dry.

 

[Mark Ferrick]

My understanding

is that the barrier coat is a much better sealant keeping water molecules out of the gelcoat. Now that being said, if there are lots of blisters , that indicates lots of moisture in the gelcoat. If you barrier coat with moisture in the gelcoat/fiberglass, then more blisters will develop as the moisture cannot get out. The trick is drying out / making sure the fiberglass is dry before you barrier coat.
I am still full of contradictions myself, not fully understanding it all.
SO, my plan is to
1- sand off all bottom paint
2- open blisters
3- let open wonds (blisters) dry
4- repair / fill blisters
5- seal hull with eppoxy / barrier coat
6- paint.
I think........... That is where my research has lead me...

As far as hot painting goes, I think I will do it.

 

[Maine Sail]

So the barrier coat is there primarily to deter blistering? How exactly does it accomlish that? I also read some posts debating whether the bottom paint should be "hot" painted, that is applied before the primer or barrier coats are dry.

Epoxy is highly water impermeable when compared to polyester resin. Most all barrier coats are epoxy based. Vinylester is excellent also.

There is no debate that I am aware of about hot coating. It is the way to do it for both build up coats of barrier and the initial coat of bottom paint because you get a primary bond rather than a secondary bond.

With Interlux Inter Protect 2000E you are supposed to hot coat the first coat of bottom paint when the barrier is "thumbprint" dry meaning that if you press your thumb to it you can still leave an imprint but no barrier sticks to your thumb. This can be a very short window of time and in warm weather can require a chaser. One guy rolling on the last barrier coat and one rolling on the paint behind them at the thumbprint window. Most all barrier coat makers do not suggest the use of water based antifouling paints for hot coating..

For the amount of time you will be hauled out of the water a barrier coat job is basically going to be a waste of money. The hull needs to be DRY before applying a barrier coat or you simply seal the moisture into the substrate. For boats that are in water year round this can take a long while out of the water to achieve dry. If you don't have a blister problem I would just haul, pressure wash, sand if necessary and re-paint.

In the NE to achieve dry out many yards will strip in October, measure moisture content then let dry all winter.

High moisture readings are recorded by tracing the outline of the meter then writing the date and moisture reading in the box. It is re-checked monthly and new readings written in the box.

As you can see drying happens quite slowly. Those readings should be roughly 4 or less before applying the barrier coat:

There are a LOT of unscrupulous yards that will take your money and do an improper barrier coat job.

P.S. No need to "tip" an ablative as they are self polishing. Use a light nap roller like a 1/4" or even foam if you want really smooth..

Micron 66 is great paint but brackish or fresh water will ruin it. Be sure you never venture up a river or estuary with low salinity or it can be an expensive venture. I was going to user it after my recent bottom job but where I launch is in brackish water and Interlux strongly advised against its use.

 

[Warren Milberg]

I am not a big fan of barrier coating, particularly an older boat (I, too, own an '86 model). If your boat does not have blisters when you haul it, my guess is that it will not develop them. If the bottom appears to be in good shape but only needs bottom painting, the trick will be determining what is already on the bottom and what is compatible with. As a very general rule of thumb, if you brush your fingers along the bottom and paint comes off on your hand, you have ablative on there now. If you rub the paint and can only burnish it, you probably have a hard modified epoxy paint. You can put ablatives over either type of paint, but you cannot put modified epoxy paint over a soft ablative without first sanding it off. Take a look at the Interlux site for a compatibility chart. So....if the paint on your boat is in good condition, that is properly adhered, all you need do is rough it up, clean off the resideu, and put on the Micron 66. If it is peeling and chipping, prep it by a good sanding. If you have no blisters (hopefully), forget about a barrier coat (which would require removing all vestiges of paint on the boat first).

 

[tommays]

The fact that your in CA makes a lot of this info of marginal value due to the much different rules on what is allowed to be used

for example Perfection cant be sold in CA

 

[Stu Jackson]

Bottom paint & locale

1. I plan on using Micron 66 because it got a very good review in Practical Sailor's tests, which seems pretty objective.

I'm not so sure about PS's objectivity in your particular case. While I haven't read the PS recommendation article (I gave up on them years ago), the MOST important issue with bottom paints is how they work in YOUR particular sailing area, not just saltwater.

Since your boat sits more than it sails, I would venture that folks in MDR harbor have preferences based on years of experience. You oughta ask around and check with your local yards before you decide for sure on Micron 66.

My local yard, right in our marina, recommends Product XYZ because it works very well. I'm going on 4 years with a coat and a half. I think that's pretty darned good for bottom paint in saltwater.

 

[dvideohd]

so what is a good MDR...

recommendation?

--jr

 

[wufibugs]

That is wonderful information. I will take a very good look at the bottom to see if there is blistering. If not, a barrier coat would be counterproductive. No one mentioned primer, which I assume means that it too is unnecessary. However, just for knowledge sake, when would one want to use a primer first?
I should note that I moved the boat to Chula Vista [San Diego]. As suggested, I asked around the docks and thus far have not found 2 people using the same bottom paint, though ablatives were in the majority.

 

[Warren Milberg]

I would use a primer, like Interlux Primocon, only when I didn't know that TYPE of bottom paint was on my boat and didn't want to totally remove it before applying a new bottom paint and was not sure it would be compatible with what's already on the boat.

 

[Futsal Fred]

OK Then How About This?

I have a 2000 Hunter 260 which spent it's first ten years in salt water.

There was maybe ten coats of ablative paint slopped on the hull and big chunks were chipped off, etc. An ugly mess.

So I'm stripping it all off, a miserable job but I'm a glutton for punishment.

I'm down to what is (I guess) the primer coat, which doesn't respond to either of the strippers I'm using (Soy Strip and Aqua Strip) so I'm going to have to sand that off but it's fairly thin and won't take a lot of effort or remove much good gelcoat.

My question:

Since the boat is now exclusively sailing in fresh water, I know I don't need an ablative paint on it again, but can I simply skip painting altogether, wax iit up good and call it a day?

Or should I coat/paint it with something, either a barrier coat or a coat of paint?

Any thoughts?