Time to Grind

[Scott]

Thanks, Paul!

Your explanation helps a lot! My boat is 20 years old so I'll bet it has a barrier coat. I talked with my marina and they said they wouldn't sand blast and they thought that stripping may be the only way to go. They won't allow me to work on this project (they are my only option for winter storage) so I will need to hire them. We hadn't decided on the course of action yet so this helps me. I assume that you need weather that is at least above freezing, so the time frame may limited.I didn't necessarily want to take it down all the way to gel coat. If it strips to a barrier coat and I can sand that before applying new paint, I think that will work fine.I look at the bottom now and see a thick, rough surface with a lot of flaking paint and I want to smooth it down and get a clean surface. No blisters are evident and the survey says the same. I wonder if removing the paint will reveal anything different.Scott

 

[John Dawson]

Try to keep up, Scott

A barrier coat has to be a little thick, so you can often tell along the waterline whether there is a little ridge of extra layer. Interprotect will be grey, Bottompoxy etc and other epoxies with additives will be a honey colored resin color. Copperpoxy is copper color, and I think the VCTar stuff is black. You need to do a little archeological dig and carefully sand down thru the layers in a spot to expose all layers down to the gelcoat and try to determine whats there. The bottom paint may change color if someone has used a flag coat first (to signal the last layer of paint when sanding.)If you are going to fix blisters under 60 degrees, I think you will need special additives. Definitely don't do any barrier coat work under 60 degrees. You will need to sand any surface for barrier coating, plus you need to paint the first layer of bottom paint into the uncured last layer of barrier. If you don't, you will need to resand it or use the no-sand primer to help adhesion.

 

[Paul (Affinity C320)]

Very Good

Yes, I agree, exactly what I did. Very good job of explaining this. Take care John.

 

[Bilge-Rat]

Scott

60 degrees being the low temp. But no more than 80 degrees. You have to mix up large batches (1 gl.)to roll it on and the stuff may set up before you can get it all on. 70 to 75 degrees it ideal. The West epoxy barrier coat is pretty thick but it still wants to run so you don't want to hurry. There are special rolls for epoxy called candy strips. They look like a barber pole. Enjoy ~~~~~picture on next post.....

 

[patrick]

No, R Kolb

Home Depot is good. Find a cute assistant. Good. Then first you say "I'm Randy". Then you say "I'm looking for a cheap stripper." Don't forget to duck. Watch out for the boyfriend, too.By the way, the epoxy itself will not dissolve. The underlying gelcoat or paint probably will. If the epoxy is intact, you can strip away the bottom paint with ease. If it is scratched or worn, you might soften the base enough to loosen the epoxy in those areas.

 

[Bilge-Rat]

Picture1

On a friends boat, here's a picture after repairing blisters ~~~~~

 

[Bilge-Rat]

Picture 2

Here is the opposite side with the barrier coat already layed up. It took 4 gallons to cover this 28' vessel.~~~~~

 

[Scott]

Keeping Up!

Thanks All ...I've got the picture now!

 

[Bob]

De-blistering

I spent a number of days cutting blisters out of the hull of my boat with a sandblaster some years ago - lots of hard work, real messy, and slow. The next time I did any de-blistering I decided to try my Dremel tool with a round cutting bit. Wow, what a difference. The Dremel would do the job in about 1/5 the time and in a much cleaner fashion. You have to handle it carefully, of course, but just pretend you are a dentist cutting our cavities. Of major importance is to make sure the blister cavity is completely dried out before you fill the void, otherwise you will see another blister form in a year or so.

 

[NautiDuck]

Repeat Bisters

Great photos bilge-rat. For you folks who have repaired blisters and then barrier coated. Did it work well? Did any blistering return? One web site I looked at said to leave the blisters alone since repairs often make the matter worse and blisters aren't all that harmful anyway. What is your experience? Randy

 

[Alan]

Which Peel Away??

There are 2 Peel Away formulas. The one sold in HD and hardware stores will not attack gelcoat and barrier coat. The 'marine' Peel Away will. The marine version is almost twice the price of the general purpose stuff. I tried both of them. Finally used the marine version a few years ago and it did a great job. Much more aggressive that the other.

 

[John Nantz]

Drying the Hull Out

With all this discussion I didn't see anything about drying the boat out before filling the voids and applying the barrier coat. Standardly one dries the boat (hull) out before applying any coatings to remove entraped moisture and avoid a return of the pox. Did anybody do that or was it just not discussed? If not, I'd be curious why not.by the way, the post about the Home Depot paint counter was really good. Maybe there should be a challenge for the most humerous posts! It's a long time to spring! (at least at 48º North!)

 

[John Dawson]

Read post #2 carefully

Specifies drying out hull before filling voids and applying barriers. Moisture meters and patches will help determine readiness. If you are in a hurry, take your boat to a hotvac center and have it cooked. Computer controlled pads that apply heat (to cure unresolved resins that attract moisture) and vacuum (to help extract moisture) over a two week period. Boat will then be ready for immediate coating. See link. A new trend is toward having barriers done professionally by a company that specializes in doing work under ideal conditions. Premature barrier failure is so common in amateur jobs that there is a growing market in this task. Barriers are said to last 7 - 10 years or more on average, and are effective in minimizing water intrusion where proper thickness and bonding are achieved.To address a previous question, blisters are said to be the result of uncured resins pulling moisture thru the gelcoat; it forms molecules that cannot escape and builds a bubble under pressure. That blister is primarily under the gelcoat, but signifies uncured resins that will continue to attract moisture and delaminate the deeper layers of the hull. Thats why fixing the blisters doesn't stop more developing, and why John N. considers drying so important. Drying the hull halts the delamination, prevents moisture from being trapped beneath the barrier, and denies the entrance of more moisture. Hopefully the resins will then have more years to fully cure.

 

[patrick]

John, are you bilocating?

Is that a word? Is it allowed here?I agree with you about drying out the hull.If memory serves me, there are several kinds of moisture meters. One measures resistance and my surveyer used one which measures some other factor - capacitance? It seems to me that resistance would not be a good actual measurement since it would vary depending on whether your boat was in salt or fresh water. It would probably give a relative indication though if used properly.Anyone have any good info on moisture meters?

 

[Fred Ficarra]

Drying out the boat might be a good thing,

especially on the INSIDE. John, do you have standing water in the bilge where the blisters manifested themselves?Sail Magazine, in a sidebar, many years ago printed a news release about a midwest university study that found that 88% of all blisters are caused by water INSIDE the hull. Cure? Paint it and keep it dry. Of course there is no gel coat inside so it seems to make sense.

 

[John Dawson]

I don't know, Patrick...

is it bad? I was referring to the second post in the thread, not going for two-part answers there.

 

[John Dawson]

I don't know, Fred...

is it bad? Anyway it seems to me that most smaller blisters are under the gelcoat. Larger ones are in the laminate, but the process works from either side. The resins attract moisture from wherever, alter it so it can't escape, and a blister occurs that splinters the laminate. If blisters mainly occurred on the hull near the bottom of the bilge, I would find that more credible. (I do believe there is some truth to it, and agree with bilge paint.) But you often see blisters distributed on the hull and on skegs that are solid. My bilge water isn't usually deep enough to make blisters halfway to the waterline. The outside water is there 24/7 with pressure. So lets include painting the bilge with drying out and barrier coating. Awlgrip, anyone?

 

[John Nantz]

Drying Out and Testing

Thanks for your answer in "Read Post #2 Carefully", John. I re-read it and you're right - just overlooked it.For a proper blister job it really makes sense that the hull should be throughly dried out and verified with a moisture meter. It also makes sense that the bilge should be maintained dry too in order to keep moisture at bay and also fight interior mold and mildew.With regard to the use of moisture meeters, however, I understand that it takes training and a lot of use to really get to learn how to use them - according to a surveyor I talked to. Sure, one can go out and buy one for a few hundred bucks, and get some readings, probably like using a stud finder, but apparently knowing what you're the readings are telling you is something else. Of course, I suppose, one can allways err on the side of not geting any readings that indicate moisture if that's possible. I'd be interested in what anybody has to say on this.The faster hull drying methods are news to me so that's interesting. If I ever buy a used boat I think one of the first things I would do is get it dried out and barrier-coat it. The boat we have now was barrier coated since new and the PSS shaft seal was installed essentially since new so that gives me a good comfort feeling. Hint: When puting a barrier coat on it's a good idea to add some pigiment so it has a different color than the white gel coat.