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Blister Questions

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CB
1st Mate

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54 Posts

Initially Posted - 05/09/2002 : 09:55:57

Hey everyone,
I went under the '81 C25 we purchased this winter yesterday to clean off the bottom, and realized that there are MANY, like a hundred or so small (half the size of a dime) blisters just below the waterline. All of them were hard, and none were spidered or anything. The bilge always stays dry.
We bought the boat knowing that we were going to have to repaint the bottom this year, but am I in for a real treat or what? Is this somewhat common? How serious is this? What type of repairs am I looking at and how long should the boat be out of the water for this type of undertaking?
I appreciate any comments and links that anyone who has experienced or is knowledgeable on this could provide.
Thanks!

Edited by - on

jm
Captain

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Canada
290 Posts

Response Posted - 05/09/2002 : 10:09:44

similar thread on blisters at

http://www.catalina25-250.org/forum/topic.asp?TOPIC_ID=1077

and many of the fix product sites have how-to literature on the subject (i.e. www.interlux.com --> http://us.yachtpaint.com/usa/
and http://marinesurvey.com/yacht/blisters.htm or http://www.boatowners.com/osmosis_l.htm

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 05/09/2002 : 10:23:02

CB,

Yes, indeed you are in for a treat, but it is not the end of the world. Although I personally do not have firsthand experience with blisters and their repair, the basic procedure is to sand the hull, grind the blisters open, rinse and dry the opened blisters, fill the blisters, then put on a barrier coat and bottom paint. From what I've read, the crucial part is the drying of the opened blisters. Some recommend letting the boat sit for 12 weeks after the blisters have been opened. If I were you I would get as much information as you can by scouring the internet and getting a book of two on the subject, because this is a labor intensive job and you only want to do it once. Coincidently, Sailnet has an article about blister repair that was submitted by someone who owns a 1981 C25. http://www.sailnet.com/collections/articles/index.cfm?articleid=caseyd0036

Don Lucier, Northstar
C25 SR/FK

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CB
1st Mate

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54 Posts

Response Posted - 05/09/2002 : 11:02:28

Thanks for the links, there is a ton of useful info out there, my next question would be, should I bother repairing these? Can they be painted over?
Many of the articles I found almost tried to discourage repair of small blisters b/c it is rarely done correctly and small blisters don't compromise the integrity of the hull.
I consider myself pretty handy, are there any special tricks to grinding down those things?
Just not sure what to do here?
Thanks in advance for your replies.

Edited by - on

MarkTM
Navigator

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USA
178 Posts

Response Posted - 05/09/2002 : 11:15:40

CB,

You don't say where you live and your profile doesn't give us any hints, either. If you live up north and haul out during the winter, you might wait until then to fix the blisters. If here in the hot south, then wait for the dead of summer when the wind disappears. The extra heat will help dry out the laminate once the blisters have been ground out. Regardless, I wouldn't compromise my sailing fun during this season <img src=icon_smile_wink.gif border=0 align=middle>

Mark Melchior
C250wb "Lorelei" #384
[url="http://www.texassailor.com/"]<img src="http://www.texassailor.com/texas.gif " border=0>[/url]
(click flag to visit Central Texas Sailor)

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Bristle
Admiral

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USA
834 Posts

Response Posted - 05/09/2002 : 11:46:26

My surveyor told me that small gelcoat blisters around the waterline are quite common, and not to worry about them. Our boat had pinhead-sized ones under the stripe when he was doing the survey--I don't think they've changed in the year since then. I think they're caused by some sort of algae that thrives in the constant combination of air and water at the waterline.

Dave Bristle, 1985 C-25 SR-FK #5032 "Passage" in CT

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CB
1st Mate

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54 Posts

Response Posted - 05/09/2002 : 11:51:30

Mark,
I'm in the Lk. Norman, NC area. So waiting until Fall probably wouldn't hurt anything I guess?

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OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 05/09/2002 : 12:54:02

Hello CB,
I also have a 1981. What's your hull (or sail) number?
I'd enjoy the season and wait until you're on the hard again this coming winter. The $3 manual on this subject from West Systems is the best money I've ever spent. When finished filling the blisters you'll want to apply a water barrier product. It's not a difficult project, just time consuming and tedious.
Interesting theory on blisters there Mr. Bristle. I read that the reason you get more blisters near the waterline is because the water temp is higher near the surface, which is consistent with the fact that tropical climate boats have a higher incidence of blisters.

Steve Madsen
#2428
OJ(Ode to Joy)

[url="http://catalina25-250.org/photo0.htm/"]<img src="http://www.catalina25-250.org/photo/ode075.jpg" border=0>[/url]

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Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 05/09/2002 : 13:01:03

I did a full bottom job on Wind Lass this past winter. I would recomend that you finish out the season and get to grinding this next winter. Pictures can be seen on the general site if you do a search for my posts (Bottom Rework). I did find an excelent bullet proof barrier coat material. I was fortunate with my rework. I had aprox 15 dime size blisters. Some were only gel coat problems and a couple went deeper. I used a dremel tool to grind them out very cautiously. Filling also takes some care. I used a two part epoxy filler and a block sander to finish them off. I would be glad to help all I can from here. I hope I never have to strip the entire bottom again.

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CB
1st Mate

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54 Posts

Response Posted - 05/09/2002 : 14:22:10

OJ, my hull # is 2672 sk/sr. And one more question, can it worsen over the next few mos if some of these areas have paint worn off?
My intent is to haul it out in Sept and go to work.
Thanks to all for the helpful info.

CB

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Dave Seely
1st Mate

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46 Posts

Response Posted - 05/09/2002 : 15:18:03

CB

I am also on Lake Norman and I can tell you that when I bought my c25 about a year ago it also had small blisters all over one side right at the water line. While cleaning all of the old paperwork out of the boat I found several articles on blisters and quotes to get it repaired. They were dated in 1994. My guess is that the blisters havn't gotten much worse since then and I know that the bottom hasn't been painted in the last 5 years. I wouldn't worry about postponing the project another season. Thats what I'm going to do.

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Bristle
Admiral

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USA
834 Posts

Response Posted - 05/09/2002 : 15:20:06

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
I read that the reason you get more blisters near the waterline is because the water temp is higher near the surface, which is consistent with the fact that tropical climate boats have a higher incidence of blisters.
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>
Theories abound, Steve... The highest incidence of blisters seems to be in fresh water--often colder than the salt water in many areas. Fresh water permeates materials more readily than salt water. Also, maybe the suspected algae likes the higher temps.

Question: Why do you supposed epoxy barrier coats are so great when water permeates epoxy-based laminations so readily and polyester gelcoats are used to retard that. Now we're supposed to put epoxy on top of the polyester? <img src=icon_smile_question.gif border=0 align=middle>

Dave Bristle, 1985 C-25 SR-FK #5032 "Passage" in CT

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Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 05/09/2002 : 17:23:27

Bristle there are as many types of epoxy as there are colors in the rainbow. If your going to do a barrier coat you need to study the speck sheet on the products. High solids epoxy is a better deal. Many sold are as much as 25 % solvents. That means by the time it is set you have lost 25% of what you paid for. I. E. the can has a lot of product that evaporates. This is one way the manufacturer rips you off. The big thing to look for is the absorbtion rate. How resistent the epoxy is to water. You can realy do a lot of homework in this area. There is lots of info to read.

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OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 05/09/2002 : 18:24:10

Auh boy. Sure would be nice to have time to read up on stuff like this and get the real answer instead of all the crap that crosses my desk every day.

Okay Dave, answer me this one. How come when I opened my blisters I didn't have green algae squirt me in the eye <img src=icon_smile_blackeye.gif border=0 align=middle> ?

CB, Dave Seely is right - don't give it a second thought for this sailing season. I don't know if you're pulling in September because of the blisters. Open them up sometime in the fall, let them dry out over the winter and fill 'em in the spring. Again, the West System manual will take all the mystery out of it.
Don't worry and enjoy the summer <img src=icon_smile_cool.gif border=0 align=middle> !

Edited by - OJ on 05/09/2002 18:32:12

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Bristle
Admiral

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USA
834 Posts

Response Posted - 05/09/2002 : 21:43:26

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
Okay Dave, answer me this one. How come when I opened my blisters I didn't have green algae squirt me in the eye <img src=icon_smile_blackeye.gif border=0 align=middle> ?
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>
OK, OJ... I don't have a clue about the algae--just repeating what an old salt told me. And Douglas: Thanks for the reading assignment. I'll get right on it--as soon as I've splashed. <img src=icon_smile_wink.gif border=0 align=middle>

Dave Bristle, 1985 C-25 SR-FK #5032 "Passage" in CT

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