Is your bottom blistered?

[sgharford]

100% with Dan on this one – Look out for the blisters that have hairline cracks propagating from them. I had about 50 blisters or so when I took bottom down on 1976 43DC. There were about 5 that had small hairline crack(s) emanating from them. These 5 in particular went halfway thru the hull when I finished grinding them out and definitely deep enough to be of concern. . Other than the almost undetectable hairline cracks, these 5 looked just like the other 45 'inconsequential' ones.

Talking smack about crack - there was a 1.5" hairline crack (looked like a spider crack) in stern starboard corner right below the boot stripe. It was never visible until all the bottom paint was taken off. I was going to ignore it until I discovered how bad damage was under all those hairline cracks from blisters. When grinded out, this pecker went over 3/4 of the way thru hull and 8" long.

My theory - I think winter storage on jack stands, especially placed on an unpaved yard, put stresses on a hull that make what would normally be a benign blister propagate into something more substantial.

[Boatsb]

100% with Dan on this one – Look out for the blisters that have hairline cracks propagating from them. I had about 50 blisters or so when I took bottom down on 1976 43DC. There were about 5 that had small hairline crack(s) emanating from them. These 5 in particular went halfway thru the hull when I finished grinding them out and definitely deep enough to be of concern. . Other than the almost undetectable hairline cracks, these 5 looked just like the other 45 'inconsequential' ones.

Talking smack about crack - there was a 1.5" hairline crack (looked like a spider crack) in stern starboard corner right below the boot stripe. It was never visible until all the bottom paint was taken off. I was going to ignore it until I discovered how bad damage was under all those hairline cracks from blisters. When grinded out, this pecker went over 3/4 of the way thru hull and 8" long.

My theory - I think winter storage on jack stands, especially placed on an unpaved yard, put stresses on a hull that make what would normally be a benign blister propagate into something more substantial.

Hatteras never mad ice cube trays. Freezing can cause a lot of damage.

[jim rosenthal]

My Hatteras (71 36C, always on the East Coast, Chesapeake and New York areas) had extensive blistering when I bought it. I didn't know about it; it was totally missed on the survey. they became apparent after the boat was hauled for other work. She also had water inside the hollow keel.

I repaired some of the blisters myself, by grinding them out and filling them with West epoxy and their barrier-coat additive. (I also repaired the keel damage) After I realized that the entire outer layer of gelcoat was covered with blisters, literally thousands of them, I had it done completely by a yard in Crisfield, MD. We noted that my repairs had held up, but that the gelcoat had been "repaired" with something- probably auto body filler- troweled into the blisters, which had not stayed in there and was now coming loose.

I was advised by an impeccable source (Tom Slane) NOT to peel the boat's bottom, but to repair the blisters in situ. Here is what the yard did:

-the boat was dried for months in the winter in Crisfield, a cold, windy area. She arrived in November and the actual repair did not begin until April or May. The rest of the time, if memory serves, she was tented with plastic and had fans under the boat.

-all of the loose material was removed using a needle gun, and the hull glass-beaded, and further dried.

-the blister areas were filled and faired with VC-Watertite

-seven coats of Interprotect 2000 were then rolled on, followed by bottom paint.

Years later, the boat's bottom was cleaned up again with soda blasting and additional Interprotect rolled on. So far, so good. It seems to be holding up fine.


At that time, I spent a lot of time and effort researching blister repairs and the significance of hull blisters. While I still would not peel and relaminate the bottom, I think the experience and skill of the operators matter just as much as the method chosen. My own feeling is that the repair method which preserves as much as possible of the original laminate structure should be preferred, and that peeling and relaminating of a hull bottom ought to be a last resort. I think that no matter how well it's done, it will never be as strong or as secure as the original laminate structure. If a layup of FRP in multiple layers is done correctly, the successive layers are chemically cross-linked as the resin polymerizes. One ought to remove only that part of the laminate which has not remained adherent to the hull bottom.

Interestingly, the blister repair industry seems to be gradually disappearing as the older boats which were prone to blistering are either repaired or leave service as a function of their age and condition. Although blistering is associated with Hatteras yachts, they are not the only ones with bottom problems; some other makes (Krogen trawlers, for one) have much more serious bottom construction issues and structural problems, on occasion. I am not aware of any Hatteras hull that has ever sunk because of blistering.

[Avenger]

My experience was similar to Dr. Jim's. Buried under forty years worth of bottom paint, initially there did not appear to be any blisters. We too had water in the keel from a crack that we assume resulted from an improper blocking job somewhere in the boat's history. Not being aware of any blisters, there were a lot of other things that motivated us to strip the bottom such as, well,... forty years of bottom paint and a crack in the keel. There were also two dead transducers with giant fairing blocks sticking out in the hydraulic breeze. *the other 'ducer with a canoe attached is on the other side of the hull.



We ended up sandblasting. I was going to go with soda, but the yard used this guy and I had seen an Oh$#it Yacht that he had done previously and found the work satisfactory. Plus it was a lot cheaper.

Funny story behind the soda blasting; I had an outfit strip the failing paint off the concrete foundation of my house and mentioned to the admiral that they do boats too, so she assumed I had already used them and asked how their work was. For future reference the best answer is not "I don't know. But if they do a good job on the house, I'll have them do the boat."

Anyhow, it was a good thing we used sand because we discovered that there were some blister issues hidden under all that paint:



The entire bottom looked like it had a rash. The sand saved us from having to grind all of that out. So about a gallon of epoxy was mixed up and shmeared into all those little pockets. Then multiple layers of barrier coat and two coats of Unepoxy anti-fouling. The hard anti-fouling was recommended as a base, then after two seasons on that we started using ablative.

She went back in much lighter, smoother and with a lot less proturderances (crap sticking off the bottom of the boat) to slow things down.



So far no indication of any new blisters and she's been in water year-round since '09 when this work was done.

[Regal2800]

Very interesting thread. I have a 1988 52' c which also has a bunch of small (quarter sized) blisters on the bottom. the surveyor and boat yard both told me not to worry about it and leave it alone but i can't help but wonder what it would take to fix. Bottom peeling i have been told will cost roughly $17-20k. The idea of repairing each blister individually is very interesting. My boat yard charged me $15 for each blister they repaired (They repaird 5 of them). If i have 500 blisters on the bottom it only comes out to $7500. Even if i have 1000 blisters it still comes out ahead of a complete bottom job. is this really a viable alternative to bottom jobs?

[kwerges]

Our 1975 42C has very few dime-size blisters. The 58YF has a three small blisters on the hull under the bottom paint, but quite a few under the new hull paint (PO) at the water line. My thinking is that the hull may not have prepped quite right prior to the paint job, as the blisters are only under the Awlgrip paint and do not extend under the bottom paint...

[wndsr]

Our 1973 53' had a lot of silver dollar blisters when we bought it. Was basically always on Chesapeake. Many I talked to said "yea, no big deal, all Hatteras' blister" I was also told "did you ever hear of a Hatteras sinking due to blisters?" All seemed to make a certain level of sense. But in the end, we had the bottom peeled and relayed. Our intensions were to restore the boat and I just could bring myself to own a boat that was restored on top and have blisters on the bottom. If we had bought our boat to simply use and use hard, or fish etc and didnt care about its overall condition, I may have chosen another route. To this day when the boat is pulled for zincs etc, it sure is nice to see a nice smooth bottom.

[jim rosenthal]

Don't peel the boat, Ariel. The photo you see above of Scrod's boat looks just like mine did. You are far better off just soda blasting or glass beading it and then filling and fairing. The worst outcome you could have from that, if you think about it, is that the fairing compound that is used to fill the blisters wouldn't stick, and you'd have to do it over. But if you peel the boat, then the part you've taken off is gone forever and you are depending on the relamination process etc to stay on. Which, according to Tom, it doesn't always do. He's restored more of these boats than anyone else and I don't think he's ever had one peeled. The repairs on mine have held up just fine and if they fall out, I'll do them again. But I will not peel the boat.

[TopHattandTails]

"She went back in much lighter, smoother and with a lot less proturdances (crap sticking off the bottom of the boat) to slow things down."

Interesting comment. Any idea as to how much lighter? Was she sitting noticeably higher in the water? The fwd 3rd of my boat sits right at the water line. So much that if I don't have water in the water tanks, the deck drains won't drain rain water. I've always attributed that to 300' of chain, no water in the tanks, granite in the crew head (floors and counters), a real hardwood floor in the dinette, a stocked refrigerator, washer dryer in the crew quarters, and all of the Admiral's shoes in the Crew closet. I've scratched the bottom and I don't believe there to be a tremendous amount of bottom paint on her. I've got no barrier coat and 3 layers of VC17 (4 layers come launch time in the Spring). She drys out real well in heated storage over the winter too. Could there be some blisters under the paint that I don't see and they're all sucking up water? I haven't moisture metered the hull since I bought her - there was nothing remarkable at that time (4 years ago), and weight doesn't seem to have changed. I just thought we all added a little weight as we aged. Wonder if its worth opening that can of worms: lighter boat = faster boat! Would sure be nice to plane her out and get 15 knots at cruise.

[Fanfare]

My bottom was peeled about 3 years ago. Took off about 1/16 inch from the gel coat. However there were six large garbage bags of old bottom paint removed.

Got about 25 years on the last bottom prep. Then blisters started returning. After a lot of barrier coat, none since. That means after 1,200 more years I will be totally out of bottom. Oh, the humanity.