Association Forum

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Blister?

New Topic

Topic Locked

Printer Friendly

Author

Topic

Steve Blackburn
Master Marine Consultant

Member Avatar

Canada
1091 Posts

Initially Posted - 03/23/2008 : 20:02:02

Presure washing my ablative paint off releaved about 5 of these damaged areas:

About the size of a quarter. You can clearly see the thickness of the white gel coat and the sturdier fiberglass underneath. This one is the most bizarre shapped one where the others are pretty round.

This would start by a small hole done quite easily where applying more of the pressure washing would grow the hole to about the size of a quarter (25 cents) then stop growing. I believe these to be weak spots and like a dentist I am removing the weak areas. I think this is good since the discovery of these weak spots gives me the opportunity to make a good repair by applying new gel coat.

Are these blisters? From touching the area it seems that the infected area a little below the gel coat thickness. Maybe a bubble in the underlying fiberglass?

What do you think these area?

Steve Blackburn, Calgary, AB
C250WB - 1999 - Hull 396

Edited by - Steve Blackburn on 03/23/2008 20:03:24

Voyager
Master Marine Consultant

Members Avatar

USA
5369 Posts

Response Posted - 03/23/2008 : 20:27:56

WWDCD? I was reading Don Casey's "Complete Illustrated Sailboat Maintenance Manual" (bought it slightly used at Amazon) and he talks about delamination and/or blistering of the hull. Since this is my first read, I could have gotten this wrong, but he suggests cleaning out any rotted wood, then refilling with penetrating epoxy to fill the resulting void.

But he also warns, if you find one or a few, look for more. He suggests tapping the hull with the back end of your screwdriver handle every 2-4 inches. Listen for a dull thud, or solid sound. Dull thud is bad, solid sound is good.

If you have some blisters, you could have a few or a lot. He says that if there are a lot, it is usually bad news. If only a few, you're in good shape to repair them.

Edited by - on

Dave Bristle
Master Marine Consultant

Members Avatar

Djibouti
10005 Posts

Response Posted - 03/23/2008 : 20:52:07

Steve: That picture looks less like a blister than some damage from an impact. The "round" ones you mention are more likely blisters, and hopefully are just between the gelcoat and the laminates. The book Bruce references is a good reference for repairing these things--basically by grinding them out (if necessary), letting them dry, filling with something like Marine Tex, sanding down, adding either a gelcoat or barrier coat layer, and then painting. If you have bottom paint now, it might be a good time to strip it to make these things easier to find. BTW, "osmotic blisters" are more of a problem in fresh water than salt--evidentally fresh water can get through the gelcoat more easily by osmosis. Thus, an epoxy barrier coat (like Interlux 2000) is more advantageous in fresh water.

Edited by - on

sweetcraft
Admiral

Members Avatar

USA
816 Posts

Response Posted - 03/23/2008 : 21:10:08

I agree with Dave that this one looks like an impact spot but also look inside for cracking. Could this also be a repair area that didn't bond? How close are the other spots?

Edited by - on

Steve Blackburn
Master Marine Consultant

Members Avatar

Canada
1091 Posts

Response Posted - 03/23/2008 : 22:13:11

They have about 3-4 feet in between them. They do indeed look like impacts that were painted over with the ablative paint. I say impact because they are all about where one would hit the boat with the dock under the water line. The fiberglass underneath is very healthy, pretty much looks like only the gelcoat has been damaged. Was thinking of using MarineTex, but then wouldn't just filling in with Gel Coat restore it to the original state? Of course in the scenario where the problem is only Gel Coat deep (deeper I would use MarineTex and just sand it smooth).

BTW: I'm in the process of removing all my old ablative paint. Doing this with a 3100 PSI pressure washer then sanding the remaining film with 150 grit. I need to use the 0 degree nozzle which is about 1/4 inch in size. I go over the whole boat this way, believe me if there is a weak spot I will find it (no need to tap). The pressure washer serves 2 purposes which is to remove the paint and check for weak spots. I will be applying VC-17 (Interlux suggest to sand with 150 grit for better adherance). Was thining of putting the VC-17 straight on the bare hull. Should I still use Interlux 2000?

Edited by - Steve Blackburn on 03/23/2008 22:20:34

John Russell
Master Marine Consultant

Members Avatar

USA
3444 Posts

Response Posted - 03/23/2008 : 22:18:31

I think Dave's right. It looks an awful lot like the spot I had to repair subsequent to a close encounter with a rock.

I'd be a little worried about blowing open blisters with high pressure. I'd worry that I'd be making a relatively insignificant problem (blister) into a big problem by introducing pressurized water under the gelcoat. Yes, yes, I know that water pressure is what causes the gelcoat to blister in the first place but, I don't think it amounts to 2500psi or more as is generated by the pressure washer.

Edited by - on

Steve Blackburn
Master Marine Consultant

Members Avatar

Canada
1091 Posts

Response Posted - 03/23/2008 : 22:23:59

Pressure washing the way I am with a 0 degree nozzle at 3100 psi is defintely dangerous if ever I would already have slight delamination. Would make things much worse. Luckily I don't have delamination. But as I have said I clean out the holes and it stops at about the size of a quarter. I plan to further clean them out with a dremel tool then fill with either MarineTex or Gel Coat depending on how deep they are.

Edited by - Steve Blackburn on 03/23/2008 22:25:09

Steve Blackburn
Master Marine Consultant

Members Avatar

Canada
1091 Posts

Response Posted - 03/23/2008 : 22:27:41

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by John Russell
 I think Dave's right. It looks an awful lot like the spot I had to repair subsequent to a close encounter with a rock.<hr height="1" noshade id="quote"></blockquote id="quote">

I agree. Now that I think about it, I have one exactly the same at the tip of the bow under the water line. Definitly an impact damage. So this is good news, it's not blistering. I've also decided to fix all of them with MarineTex, that's good stuff. Thanks guys.

Edited by - Steve Blackburn on 03/24/2008 00:56:33

OLarryR
Master Marine Consultant

Members Avatar

USA
3462 Posts

Response Posted - 03/24/2008 : 05:49:20

When I bought my 1989 in 2005 and had it taken out for a pressure washing, I noticed about 20 blisters mostly about a dime size and a few a bit larger. The marina guys looked them over and their advice at the time was to leave them alone since the boat was an '89 and the blisters could have been that way for many years without growing any larger. They indicated to just keep an eye on them the next time I take the boat out.

I keep the boat in the water all year round but in 2006, that was a total of 5 years since it was last bottom painted w/ablative paint(Potomac River - freshwater), it was time to do it. When we had the boat in the yard and inspected the blisters again, they were about the same size as before but as the guys prepared the bottom, most of the blisters turned out to be paint blisters. I had perhaps 5 real blisters but they were not all that bad. Even so, they sanded them down and opened/repatched maybe 3 of them but not sure what they used. Then they used a barrier paint (not sure which one) over those areas. Two of the blisters were very faint and they left them alone...not sure if they put barrier paint on those.

On an older boat, the basic advice was that unless there are many true blisters thru the gel coat or they grow to the size of a quarter or larger to leave them alone and just check their growth yearly.

On a more recent boat such as yours, sounds like you are doing the right thing taking action now.

Edited by - OLarryR on 03/24/2008 05:53:17

Steve Blackburn
Master Marine Consultant

Members Avatar

Canada
1091 Posts

Response Posted - 03/24/2008 : 10:31:54

Larry,

I wonder why an older boat would need to be left alone as they have suggested? Maybe water left behind creating osmotic pressure under the repair rendering delamination? I would let it dry for a week or more, remove the totality of the infected area and repair.

On a particular area it was clear that ablative paint was used as a filler. Probably a minor gelcoat chip but still totaly unacceptable from my point of view. It's so easy to apply Marine Tex then sand it. What I believe happened is that my boat incured several impacts over the years which probably didn't look all that bad with the ablative paint over it. This is a good opportunity for me to restore the hull and keel to original factory conditions.

Edited by - on

stampeder
Master Marine Consultant

Members Avatar

1608 Posts

Response Posted - 03/24/2008 : 12:09:34

Marine Tex is good stuff. I used it to fix an impact spot and a couple small blisters.
Take a very close look at the Marine Tex container before you buy - as it generally comes in black or white - but for some reason they don't print the color on the container in an obvious way.
When I bought mine out at GL Marina, the white had a black lid and the black had a white lid, but in small print on the bottom of the label it showed the colour.
Expect that you may have to apply the marine tex twice to get the exact level/smoothness you want. Apply - dry - sand, apply dry sand. That advice came to me from a Navy Mechanic. In the little spots I did fine with one application, in the big spot by my bow eye, I did two applications. Whatever kind of applicator you use, make sure you've got several. I used plastic scrappers... a piece of semi-rigid plastic about 4" X 4". They are sold in paint stores and are very good for feathering marine tex or other adhesives. Use them, then throw them away.
I used a can of compressed air to get every bit of gunk out of my repair spots. When I did my bottom job, the port side was in full sun and the Stbd side was in the shade, so I used a hair dryer to ensure that my cleaned out blisters were dry and warm, which is especially important for that impact spot you show the picture of. Now you can see exactly how thick your gel coat is and you'll know for the future if you can sand any of it.
I decided that mine is quite thick and that a very small amount of sanding would be okay.

Edited by - on

OLarryR
Master Marine Consultant

Members Avatar

USA
3462 Posts

Response Posted - 03/24/2008 : 12:54:33

Steve,

I believe their thinking regarding an olde rboat was that I had just bought the boat about a month prior to the pressure wash. There first thought was that the blisters i had were not all that bad and they may have been that way for many, many years with no further growth. It would have been easy for them to suggest to me an expensive fix-up job but they felt that I could wait till I needed a new paint job which was estimated to be the next year and then they could assess them again. As it turned out, most of the blisters really were not blisters but more or less paint dimples. The few blisters I did have they took care of except for two that were barely raised. I will check them out this year.

I have read a bunch of articles on blisters and it does not necessarily mean having a few is a catastrophe. But I would think if blisters developed pretty early in a boat's life, then that would be something that probably would need more immediate attention because it could mean future development of addl blisters. Also, if you have easy access to your boat - take it out in the winter, then you have your own time to deal with any blisters that arise. When you keep a boat in the water all year and have limited services for raising it out of the water and they charge per week that it out and no dry storage except if you put your name on a waiting list, you think twice about the necessity for hiring the guys to do the work - time is money.

Edited by - on

tinob
Master Marine Consultant

Members Avatar

USA
1883 Posts

Response Posted - 03/24/2008 : 13:04:04

Steve,

I'd go with impact damage as well. But before using any sanding filler it is recommended that the inner glass(that which is within the gelcoat) be primed with the likes of Interlux 1000, then Interlux two-part filler which is sanded down and then barrier coated. In my experience the best paint is CCP ablative from WM.

It is also necessary that when the gel coat is opened up like that that a considerable period of drying time be exhausted before doing anything further. Interlux recommends months (I know that we sailors haven't got months to exhaust) but to repair a wet hull is counter productive. Contact the Interlux web-site and ask for their recommendations.
Several years ago I had the bottom of my boat('83)sand blasted which exposed several hundred osmotic blisters on both sides of the boat. I Dremmeled each open with burrs and waited half of a very hot summer for them to dry out before priming them. The choice of bottom paint is up to the individual, I at first went with Micron CSC but there was problem with adequate adhesion and later switched to CCP. The CCP has been on for the past five years and is only now starting to show the SIGNAL coat. Unfortunately here in New York it is illegal to do ones own bottom paint. This leaves me with the dilemma of having the yard do it( yeah I know) or having the boat transported to my home and doing the job right.

Val on the hard DAGNABIT, # 3936, Patchogue, N.Y.

Edited by - on

stampeder
Master Marine Consultant

Members Avatar

1608 Posts

Response Posted - 03/24/2008 : 14:15:07

can't say it often enough, call interlux to find out what the best stuff for the job is, in your climate and sailing conditions.

Edited by - on

John Russell
Master Marine Consultant

Members Avatar

USA
3444 Posts

Response Posted - 03/24/2008 : 15:15:43

This is my absolute favorite article on fiberglass blisters. the opening line is:

"I'm going to say this right here, right now: "Gelcoat blisters don't matter!" "

He goes on to make a convincing case for his comment.

[url="http://www.sealakeyachts.com/service/blisters.html"]Jan de Groot on blisters[/url]

Edited by - on

Nautiduck
Master Marine Consultant

Members Avatar

USA
3704 Posts

Response Posted - 03/24/2008 : 16:51:22

This is my favorite site on blisters. He also doesn't think they are usually a problem. Same reasoning as Jan de Groot. The blister forms on the outside of all the structural material.

[url="http://www.yachtsurvey.com/blisters.htm"]blisters[/url]

Edited by - Nautiduck on 03/24/2008 16:52:32

Steve Blackburn
Master Marine Consultant

Members Avatar

Canada
1091 Posts

Response Posted - 03/24/2008 : 19:20:42

Excellent, thanks for all the info guys.

Mike I bought Marine Tex from GL. Only carries the smaller quantity like 2oz for about $12. You can get a 14Oz for $32. I wonder if I can get it from Industrial Plastics.

Edited by - on

stampeder
Master Marine Consultant

Members Avatar

1608 Posts

Response Posted - 03/25/2008 : 14:17:02

I don't know Industrial Plastics but Glenmore Sailboats (Hunter dealer) up on Blackfoot NE carries it.

Edited by - on

Cloudveil
1st Mate

Members Avatar

USA
60 Posts

Response Posted - 03/25/2008 : 17:57:19

Steve - The April '08 Cruising World mag. has an excellent article on osmosic blisters and their repair(s).

Edited by - on

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.