Pox

[FlimFlamII]

My boat has a serious issue with pox. It was pulled three years ago and the pox dealt with at that time. According to the shop that did the work pox can be on ongoing issue for some boats. He claims it will probably need to be pulled every couple of years and deal with the pox.

Any ideas on sources to read up on ways to deal with this myself?

Thanks,

 

[Bill1565]

Not sure what you mean by "pox". If it is blisters, there are thousands of resources.

 

[centerline]

cant tell by the photos what you are actually seeing in person.... and it may or may not be a serious problem.

hull blistering can occur on any FRP hull at anytime, and it can be, but not always, more serious for ocean going boats that are taking a pounding....

just because your boat has it is no reason to worry yourself sick or get into a panic and spend your life savings to have the hull stripped and epoxy coated.... although the boatyard may disagree with me, not because im wrong, but because they want your money.

the blistering is very unlikely to cause you any harm other than your worry about it... if you arent racing the boat then what little drag they may ever induce will go unnoticed.

if you bought the boat without having a survey, it was an unwise decision... not so much in the purchase, but in not having a survey done. the price for that will be the hit you take when you sell it and the next owner does have a survey done.

the boat will be just as much fun with hull blisters as it will be without them, and no matter how well you treat the bottom or what you spend on the problem to make it go away, you will never recoup the money when you sell, as its an expensive process.

even though it is a blem in the boat, for most lakers, river sailors and bay sailors, the pox problem is more painful to the owners pride than it is an actual problem that needs money thrown at it....

on the bottom of my 34 there are three blisters the size of silver dollars, and i did a LOT of research on it before I bought the boat.... some boats have much worse blistering problems but its not a worry, but just something that you either fix or dont...

 

[Joe]

Don't know what "pox" is... but it simply looks like a crappy paint job.

First I would find out EXACTLY what they did three years ago.... have them define "pox' and then take it to a different "expert"... for another opinion.

 

[SteveB]

FlimFlammII

I am in the middle of a repair job myself, so suspect I know how you feel. (see attached pics) A few points:

1.Centerline is right--"just because your boat has it is no reason to worry yourself sick or get into a panic....." Take it slow and do a lot of research and evaluate your hull.

1a. (You are going to get a lot of opinions and advice. At least half don't know what they are talking about. Read a lot and seek out those with experience.)

2. Don Casey's book "Sailboat Hull and Deck Repair" is a good starting point. I have collected several more in-depth pieces that are balanced. Send me your e-mail in a PM and I can send you copies.

3. Ask for someone outside the yard who's experience and perspective you trust and have them look over the hull with you. Perhaps a local surveyor who can sound the hull and take moisture meter readings.

4. Sound the entire hull with a phenolic hammer (plastic end screwdriver works as well) listening for potential areas of delimitation (see my third pix). Listen carefully for dull thuds.

5. Have them take take moisture readings.

6. Pop a couple of "pox" see if they weep. If so, smell the discharge to see if it smells like vinegar.

7. Let the boat dry out for a couple of weeks and see if they disappear. Look for other signs of compromises in the gel coat.

At that point, you can make a determination on the level of "fix" you need: good sanding job, sandblasting, or (god forbid) peeling the gel coat to expose the glass/resin.

Materials I send you are a good source on what to do if its the later. Good luck.

 

[FlimFlamII]

Thanks Centerline and Steve B.

Three years ago they just sanded (a lot), filled with epoxy resin (a lot) and applied an antifouling paint.

 

[BigEasy]

I had a similar experience with a 1988 Hunter 33.5. Upon initial survey, thousands of dime sized blisters were detected. The surveryor that I used, assured me that the problem could be successfully treated. I negotiated a great price on the boat and used it over the summer & fall. Around Thanksgiving, I had it hauled and had the gelcoat peeled and allowed it to dry out for 5 months. Vinyl ester resin barrier coats were applied and finally anti fouling paint. One and one half years later, the boat was hauled and the pox was back again just as bad as before. I kept the boat for approximately 7 years and it was totaled in Hurricane Katrina.

Take my advice as well as Centerlines. Enjoy your boat and don't spend a bunch of money & time trying to fix a problem that has no end. In short, pox CAN NOT be fixed. If any yard is telling you otherwise, ask them for a 5 year warranty and see what happens!!

As long as the blisters remain small, there shouldn't be any compromise to the structural integrity of the hull. I would be willing to bet that the blisters are all located in the superficial layers of the layups, between the gelcoat and chopped strand layers. When you finally decide to sell, it may take a bit longer to sell and you will likely get a lower sale price; however, it will sell. There was a broker who once told me that " he had never listed a blistered boat that didn't sell"

I did a lot of research on the matter when I was contemplating having the blister problem treated again before I would sell. As I stated previously, there is NO long term fix for this problem. Boats in the North likely have a longer success rate because they are out of the water for 6 months per year; however, in the South where boats are in the water year round, water absorption occurs in the laminates and the blisters return again rather quickly. Years ago, I had read that there was a high quality yard in the North East that repaired blistered hulls. They peeled the gelcoat and placed the boat in a temperature & humidity controlled building. The hull was washed repeatedly to remove the amine blush that occurs while it is drying. Controlled heat was applied to the hull to further dry it and to further "cure" the resins. The entire process took about 6 months. The cost was approximately $1000 per foot! They provided a 5 year warranty and were honest enough to admit that the problem would eventually reoccur.

If there are isolated blisters, the usual fix is to grind them out, dry, fill, and place a vinyl ester or expoxy barrier coat. Unfortunately, with pox -- you cant do this treatment because there are thousands. The only way to remove them is to peel off all the gelcoat. Even if you do this job yourself, it will be expensive because the yard storage costs. After the gelcoat is peeled, the hull needs to be "tented" and heaters/dehumidifiers placed to attempt to dry the hull before a barrier coat is applied.

Again, the best course of action is to enjoy the boat now; sell it when you are ready to move on.

 

[shemandr]

And, buyer beware. When you see a boat listing that reads something like "New bottom two years ago," you should know from this thread alone what that means. Someone wants to git, while the gitin' is good.

 

[centerline]

Don't know what "pox" is... but it simply looks like a crappy paint job.

First I would find out EXACTLY what they did three years ago.... have them define "pox' and then take it to a different "expert"... for another opinion.

Boat pox is just a slang term like so many others.
blistering and damage of/to the hull skin similar to what chicken pox can do to a persons skin.. its not life threatening, but forever blemished without cosmetic repairs

And I agree that from the photo it looks more like a crappy and blistering paint job rather than hull blisters... Paint pox?
any given competent surveyor you choose to look at it may not be an expert in the repairs of actual hull blistering, but they can rationally tell you what level the seriousness of it is, make recommendations, and then direct you to a decent repair yard if you decide to throw money at it.

 

[TENACITY CS36T]

Totally agree with BigEasy.

 

[BigEasy]

Agree with others that perhaps you should have a competent surveyor who has experience with blisters to take a look. Blisters & Pox usually appear as a bump on the surface of the hull. They are more visible when the boat is hauled out and immediately inspected while still wet. Smaller blisters become less visible as the hull drys. As SteveB mentioned, if you press on the visible bump with a sharp object, the blister will discharge an acidic fluid. Hopefully, as Centerline observed, you may only have a blistering paint problem that is easy to remedy.

Also noted on your second picture that there appears to be rust in the bottom of the exposures. Is this a photo of a cast iron keel that is rusting?

 

[RonRelyea]

some required reading ...

I've found David Pascoe's articles quite helpful ...
http://www.yachtsurvey.com/blisters.htm

 

[Ken Cross]

Based on your photos

It looks to me like it was too long between applications of bottom paint. Also it is a pretty simple DIY project. I guess I'm too cheap to have someone else do it. I just completed and launched ours yesterday and the results are in the photo. Because we have a steel keel, it was a bit more work stripping and re-finishing the keel. As I often do, I also look for advice on this forum before I undertake a job of this size. Often I find new ideas I hadn't thought of. There are some smart people here.

Ken

 

[shnool]

Wow, I guess it depends on how bad they are... the OP's picture doesn't actually look all that bad, and honestly I don't see osmotic blisters in the picture, just a lousy bottom job (or perhaps a good one that is past due)..

I had VERY few osmotic blisters on my Capri 25, but I needed to do a bottom job anyway. When I scraped the whole bottom off, I came across several blisters that popped and weeped, and they stunk. I allowed those to dry and checked for signs of standing water. Here's the rub, everyone expects problems from a poor bottom job, to create blisters (and it does)... but very few address the problem coming from long standing bilge water. Blisters are merely water intrusion into the laminate. The "smell" is from the resins that get compromised in the process of the intrusion.

From the outside, once dry, a good barrier coat, with proper thickness can do a world of good... from the inside, A) you gotta keep the bilge dry, and B) you should figure out how water might get into the laminate. A similar approach on the inside of barrier coat and paint might be in order.

My present racing sailboat (S2 7.9).. has the very early formation of blisters. Entertainingly it's been dry docked for 7 years! Tell me how does one get blisters sitting on the hard? Bilgewater! My approach right now is to knock down the blisters, repair where necessary, and wait. I'm keeping water out of the bilge and looking season on season for re-formation. The particular layup the builder uses has a lot to do with how "readily" blisters form. The early years of the S2 builds 1982-1984, are more prone than the later ones.

Here's how I attacked my Capri 25 with them. Most of my blisters were directly under the trailer support pads. I suppose because they had the "least attention" to them because of how difficult it was to work under them (trailer only had 4 supports)..

Barrier coat..

It all worked out....

 

[Kenneth Frehm]

I had beginning of this problem many years ago. I sanded off all the anti-fouling paint as well as cleaned gel-coat. Then I called Wes Coat ... that was a difficult job as you use their 2-part epoxy and mix in aluminum powder. You also need their cleaner. I put on 4 or 5 thin coats, following all their directions and then top coated with good bottom paint. At end of year I power wash and boat is ready to go back into water. No blister problems since. Call Wess Coat... they will have products to fix it once and for all.

 

[captjim1]

I had to fix what you call POX, But it is a BLISTER. If you water blast you will break the weaker Blisters, which may have water in it already. I find using a Dremel Tool with a burr bit. You will be able to do a very clean job of removing anything that is not green Polyester or if Epoxy it will be shiny. Fill the clean blisters with the same hull material. After this is all done and finished, use a couple of barrier coats. Then lightly sand the bumps and brush tracks, to make the hull very smooth, coat it with Bottom paint.

 

[splax]

My hull was like orange rind below the waterline when I had the boat hauled out, and it showed some evidence of previous blister remediation. I used a belt sander with 80 grit sandpaper to smooth the surface, then sealed the hull by painting on epoxy. That was two years ago, and so far so good.

 

[jzuk]

My new to me Oday is luckly has an insignificant amount to bother.

As a teen in the late 80's I remeber my father buying a CS 27 that had the pox. We carefully sanded her down popping the blistes (as a teen I thought of them more like zits). Barrier coat and antifouling paint up to the waterline, which before cleaning was at the water line scum mark.
When we got the boat in the water, she was floaring a good 2" highier at the waterline. Figure the pox added a bunch of water weight and the PO kept moving the water line up a touch each year.

In the far future if thinking of updatung my barrier coat, after I find all the deck leaks. Not much point barrier coating outside if my bildge is always wet and water can sneak in from inside (kinda like schnool said).

 

[FlimFlamII]

Additional photos. When I did a sample sanding this is what I uncovered. It appears that the pitting is restricted to the brown colored area. the areas that are not brown show no pitting. The gray in the bottom left is fiberglass and I assume the lighter color is the gel coat. Can anyone tell by the pictures. It would seem that the 'fix' is to sand off the brown and then follow the advise given is some of the previous posts.