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Blistering

11K views 83 replies 20 participants last post by  sailingdog 
#1 ·
Good day all,

I have 1981 22' Catalina that has been in the water most of her life. You all know what that means BLISTERING. I have to get her out of the water to do some other work on her, knowing that she will have blistering I 'll need to fix that along with the other work. My question is what is the best path to take when it comes to blistering. I would like to do the work my self and have a few insights on what to do, but would like a few more just to make sure I'm going the right way. My first step will be to have her surveyed.

:rolleyes:
 
#2 ·
Depends on how deep the blisters go. If they are mostly superficial, and in the gelcoat, then sanding, letting the hull dry and then re-fair and epoxy barrier coating is probably the way to go. If the blisters go deeper into the laminate, then you'll have a lot of nasty work cut out for you...not that blisters aren't nasty to begin with.
 
#6 ·
Treating the blister problem is a relatively simple procedure and you'll get plenty of advice from links like the above.
The biggest part of the procedure, and one that probably gets short-circuited the most is the drying out of the hull once the blisters have been opened up. This can take literally months, up to 6 or more. A good way to address this is to write off the latter part of the season, haul in the fall, seal off the boat in a tarp or shelter of some sort and keep it dry and warm over the winter. Then address the repairs in the late spring.

We did just that a few years back on a 1981 boat, used Interlux barrier epoxy, laid on 6 - 8 coats, and have not had a recurrence .
 
#7 ·
dry time

Yes the drying of the hull is important. More of an issue in the northern climates. Mine dryed in a metal warehouse in Houston in the summer. It was there for 2 years. Hard to beat that. There are ways to hasten the process up north with lights and what have you.

pigslo
 
#8 ·
Yes, making sure the laminate is completely dry is the most important part of repairing blistering. Unfortunately, the only easy way to do that is TIME, hot dry air, and patience.
 
#9 ·
The link above would not open but it sounds like people are saying you can just open up the known blisters dry out and and then epoxy.
In my experience you should take off all of the gel coat and then dry the hull. There will be internal blisters trapped within the gel coat that have not appreared yet.
On a 22 ft boat it is not that big a job to remove it all. I just completed a 30 footer and that was fun.
I found a powerful ( 3 amps) random obital sander to be the best method.

Gary
 
#10 ·
Time

If there is one thing I have it is time. My job is taking me away for three mouth,(three of the hottest mouths in GA.) I'm just wondering if I should open the blister before I go away or wait till I get back. I can always do the other work over the winter and let the blister wait till spring.:confused:
 
#11 ·
A couple quick points here,

-You should open up the blisters before your leave. If you do grind them out, make sure that you grind down into solid glass, and not just through the gelcoat. You should also cover the hull against driving rain but leave the cover open so that air can circulate.
-There was a misspelling in the above link to David Pascoe's site is http://www.yachtsurvey.com
-Peeling is generally believed to be better than grinding. Grinding builds up heat and at least one paper that I have seen suggests that the heat build up can undermine the immeadiate sub-layers.
-I am a big believer in laying up the repair with cloth and epoxy resin. I agree with David Pascoe's point about removing all unsaturated laminate and filling all pinholes and with his point that unreinforced epoxy does not have the strength to bridge gaps. Using cloth adds to the labor involved in making the repair but it also helps guarentee a more permanent fix.
-While I understand and essentially agree with his point on Osmotic blistering, I personally have seen cases where water from the bilge has moved through the laminate causing major delamination. The worst cases of that that I have seen have been in keel cavities where poor laminate is more prevelient (its hard to work properly in a confined space like a keel cavity) and where water is often trapped against the interior of this inferior laminate.

Jeff
 
#12 ·
Was there a year of manufacture in the industry that breakthroughs were found or technology was improved that made blistering occur less often?
Maybe even some of the individual builders who have been more successful than others at eliminating the problem?
 
#13 ·
Each manufacturer had a period of years during which their boats had the worst blister problem. The specific years varied from manunfacturer to manufacturer. In a general sense resins began being reformulated during the mid-1970's due to the "Oil Crisises". For most U.S. manufacturers the worst period for blistering was somewhere around 1979-1983, with the problem tapering off throughout the 1980's as better resins and building techniques came on line. It was during the 1979-1983 period that the worst of the true osmotic blistering was a problem and boats with true osmotic blistering can never permanently be repaired. (These boats often have lower prices than the same model produced in earlier and later production years). The European and Asian yards seemed to take longer resolving the problem than the better U.S. yards.

Jeff
 
#14 ·
I had to relaminate my Little Harbor 38 back in 1996. Like your boat she had sat in the water year round. I tried sand blasting but the problem was too deep and I would have been better off going straight to having the boat blister peeled as it would have produced a fairer surface to build back on. Anyway I did have to boat peeled and then spent days sanding. This part was a lot of fun in a tyvek jump suit in the 95 deg. / 95 humidity NC sun. After that I relaminated with layers of 12.5 oz cloth and West System. I stuck with West System on the barrier coat too using their barrier coat additive. Start to finish I probably used something on the order of 20 gallons of West System!!! Ten years out now I've had no problems. Tips: figure at least six months to let the hull dry. Send me a message if you want to buy a Traumenx (sp) Skipper moisture meter as I have one that I bought for the job and never bothered to sell. Also, when you relaminate, if you have to, plan your work so you get a chemical link between West System coats or if this is not possible use their release fabric as it will help you get a better mechanical bond.
 
#15 ·
Jeff_H said:
A couple quick points here,

-You should open up the blisters before your leave. If you do grind them out, make sure that you grind down into solid glass, and not just through the gelcoat. You should also cover the hull against driving rain but leave the cover open so that air can circulate.
-There was a misspelling in the above link to David Pascoe's site is http://www.yachtsurvey.com
-Peeling is generally believed to be better than grinding. Grinding builds up heat and at least one paper that I have seen suggests that the heat build up can undermine the immeadiate sub-layers.
-I am a big believer in laying up the repair with cloth and epoxy resin. I agree with David Pascoe's point about removing all unsaturated laminate and filling all pinholes and with his point that unreinforced epoxy does not have the strength to bridge gaps. Using cloth adds to the labor involved in making the repair but it also helps guarentee a more permanent fix.
-While I understand and essentially agree with his point on Osmotic blistering, I personally have seen cases where water from the bilge has moved through the laminate causing major delamination. The worst cases of that that I have seen have been in keel cavities where poor laminate is more prevelient (its hard to work properly in a confined space like a keel cavity) and where water is often trapped against the interior of this inferior laminate.

Jeff
Believe Jeff meant all saturated laminate above... otherwise I agree with what he has said. :D
 
#16 ·
Actually, I meant 'unsaturated' by which I meant, remove all laminate that did not appear to be properly saturated with resin. As I read that back to meyself, this was a case where what I meant was perfectly obvious to me as I was writing it but was not clear to anyone else from what I had written. I hate when that happens, but thanks for pointing out the ambiguity of that sentence.

Jeff
 
#18 ·
Definitely, open them up before you leave. Strip whatever you are going to strip off the bottom, so it dries more thorougly, and make sure no water will acucmulate INSIDE the hull (from rain, etc.) while you are gone. When you come back it should be much drier and that's when you want to do the repairs. Don't be surprised to find you are floating higher in the water after a 3-month dry out!<G>
 
#19 ·
More info

The link that Rich H was displaying is yachtsurvey.com (he left out the 't'). Other information at zanhisers.com, a marina in the Chesapeake Bay. Follow links to their paper on hull blistering. It's based on a coast guard funded study by the University of Rhode Island by Thomas Rocket and Vincent Rose, The Causes of Boat Hull Blisters, 1987.

Google their names and you'll find more infomation.

Also, search this message board for blistering. Sailor Mitch helped me with my blistering problem. There are several posts on the topic.

Good luck- blisters suck.

Max
 
#20 ·
Out of the water

Will she is out of the water and she looks like a 15 year old that just had a run in with the cookie jar. I don't thank that I'm going to have the time before the 30th to do the work. As far as I can tail everything from the water line down will have to come off. I have to go back out to her in the morning to check the covering (We got rain this evening, first in a mouth). I'll post some pic's so you all can see what it looks like.

I would like to say thanks to all the great seaman that have posted very helpful info on this problem.

Thank You,
May the sun aways be on your face and the wind at your back. Good sailing to you all.

:D
 
#21 ·
JeffH-

I thought you were speaking of water-saturated...not resin-unsaturated laminate. :D Thanks for clearing that up.
 
#22 ·
Sonny...While there's been lots of great advice onn repairig blisters here...one thing you have to consider is that this is a 25 year old boat worth perhaps...$2k??
Aside from the hundreds of $$ of materials you will need to make this really right...there is a lot of unpleasant labor involved and you have to put some value on that. If the blisters are as extensive as you seem to indicate, I'd try to do a cheap and dirty job that will keep ya good to go for a few years before the boat is trashed. I would sandblast below the waterline, throw on a couple of coats of barrier coat and a couple more of bottom paint and just go sailing!
If you want to go for the right job...no problem...but I just thought I'd offer a contrary opinion! If you do decide to go ahead...check out thhis article on how you can do it without spending months waiting for the blisters to dry out:
http://www.epoxyproducts.com/blister4u.html
 
#24 ·
pictures

Here are some pictures of the job ahead. As you can tail it is going to be along one. The bigger yellow box(the smaller of the two picture) is 1' square. The smaller yellow box (the bigger of the two picture)is a bubble if you will. It is about 2" across and 1-1/2" top to bottom and stands out about an 1/16 of an inch. I thank that water has gotten in between the layers of gel-coat and the glass to make this one. Anyway, it is going to sit for three mouths and dry out. I wrapped it up like a Christmas gift today. Just in time we got more rain this evening. Again thanks for all the help.

View attachment 49

View attachment 50
 
#25 ·
Hi Sonny,

Unless you open the blisters there will be almost no drying of the laminate in that three month period. A partial cause of the blistering is that the outer raised surface of the blister isn't pourous enough to relieve the pressure building up, and so the pressure pushes the membrane away from the hull. With the membrane that forms the outside of the blister in place, very little water can pass through compared to with the membrane removed.

One minor suggestion, having seen the photos it would probably make sense to have a shallow peel and then grind out the deeper delaminated resin. On a boat like the Catalina 22, another suggestion, for what it is worth, it would sure be a lot easier to do the layup and grinding with the boat turned upside down.

Jeff
 
#26 ·
Time

after the boat has been peeled and the blister have been sanded, how much time will it she need to dry out. How about on here side I'm not to sure I can get her turned over. I have to do it in a self service yard or in my on yard. The marina want allow you to do this kind of work in the dry slip. You have to do it in there yard and of course there is a daily charge.
 
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