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Old 01-11-2006, 23:51   #1
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Is preventing Blisters possible?

There is a lot of discussion on all forums about Blisters. Nobody really has a fool proof answer on how not to get them. A LOT of money is made by fixing them and I am wanting not to spend it. A few questions to the group for those of you who have kept a boat in the water for a year or more.

Did you get blisters or not? How long did it take or not?
Please give details like, did a pro do the work, what you used on the bottom, how many coats and what location did you keep the boat. If you did the work, what skill level are you.

From what I can tell the prep and aplication is just as important as the material used.
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Old 02-11-2006, 01:54   #2
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Hi Lynx,

I think most know that with modern build methods the longer term risk of osmisis is significantly less than on regualr GRP hulls built a decade or more ago.

IMHO the major progression since has been in the increased density of gel coat, which now minimises water intake. I doubt is most boats built today with epoxy resin / gelcoat will ever see osmosis problems.

Modern build methods where vacuum bagging and pre-preg cloths also helps to reduce voids in the layup has also significantly reduced osmosis risks whatever resins are used.

And finally a lack of cleanliness when the layup was underway is also accepted as a contributory cause years back which modern yards now avoid. It was not uncommon for workers to walk in dust and dirt when laying up into a female mould. It was thought those voids created when the dirt particles trapped in the layup evenutally degraded, provided an opportunity for osmosis to get a hold.

In my opinion if one has an older hull - it is down to luck whether one will see osmosis at some later stage dependent on all the above. A barrier cost of epoxy over a regular GRP hull inside and out can only be beneficial - but if the hull has already soaked up some water even thats not going to stop the blisters eventually appearing and requiring treatment.

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Old 02-11-2006, 03:19   #3
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Treatment is mostly about getting the huul moisture level down to the point where the barrier coat warranty will kick in. You can have high moisture without blisters but it won't be the other way around.

The problem is from moisture absorption so you need to get the water out. Just sitting out on the hard will over time lower it. It can take a long time. Vacuume proceses are now avialble to help remove moisture faster but it's a higher cost for you since it uses expensive equipment. After that it's just a lot of labor to grind out the problems and then patch, fair, barrier coat, then bottom paint.

So yes it is about the prep. Wait for the moisture level, then expect a lot of hours of work. It's not complicated. There is just a heck of a lot of it.

A retired friend spent the better part of a year redoing a Tartan 37. He was picky of it and took his time and has a real life that requires his time for other things too. There is a lot of surface area on a 37 Tartan.

Quote:
A barrier cost of epoxy over a regular GRP hull inside and out can only be beneficial - but if the hull has already soaked up some water even thats not going to stop the blisters eventually appearing and requiring treatment.
That's about it. If your moisture level is already low a new barrier coat would protect you. You just need to remove all the paint so you can re coat it.

My boat is never out of the water except for haul outs to do work. There is nothing that says if you leave the boat in the water it will get blisters and if you don't you never will. Boats that tend to get blisters usually always tend to get them. Manufacturing and materials as noted above play into it. Boats from the early 80's may have more problems as resins were more expensive (oil crisies) and the cheap resins of the day were not very good. It's not all boats of the era. Poor materials can still be purchased on the cheap. Companies can still do a poor job.

It may look terrible but boats don't sink from blisters. You can haul out and check the moisture level if you think you may have a problem. It's not something that goes wild unless you ignore it.
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Old 02-11-2006, 05:56   #4
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Lynx,

All you ever wanted to know about blisters.
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Old 02-11-2006, 07:24   #5
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When I first purchased my (second owner) 1973 Pearson 36 I was aware of the possible blistering in the fiberglass hull. The first season I sanded off all the antifoulant paint down to the gelcoat. Then preped it and put on 4 coats of the InterProtect Barrier Coat. It must be about 20 years ago since I did it and still no signs of any blisters.

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Old 02-11-2006, 07:33   #6
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Thermocure

In Australia they use a process called Thermocure, from what I have found it is in the high 90%'s for preventing osmosis. Holding Pattern was Thermocured in AUS during her circumnavigation and we have many pictures as well as a detailed "in-process" photo set to show what was done.
From what I have recently read there are several competitors in the EU but one source said only the Aussies have the process mastered. I've been trying to find out more about the process recently. If you have in-depth knowledge please contact me.
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Old 02-11-2006, 08:29   #7
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Vasco, your link doesn't work...

Paul, I would refer you to several articles written by Steve C. D'Antonio for PassageMaker magazine. In those articles he details causes and repair details. What you have described, IMHO, is a cosmetic fix not a long lasting repair.

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Old 02-11-2006, 10:18   #8
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Quote:
Originally Posted by Lynx
There is a lot of discussion on all forums about Blisters. Nobody really has a fool proof answer on how not to get them. A LOT of money is made by fixing them and I am wanting not to spend it. A few questions to the group for those of you who have kept a boat in the water for a year or more.

Did you get blisters or not? How long did it take or not?
Please give details like, did a pro do the work, what you used on the bottom, how many coats and what location did you keep the boat. If you did the work, what skill level are you.

From what I can tell the prep and aplication is just as important as the material used.
I have never had blisters on my 1985 Union 32. I did however epoxy the bottom as a preventitive measure. ( I don't remember the exact year, but it was probably 1990 or so). We stripped the bottom to bare gelcoat, and then rolled on many coats of West system epoxy. After that we faired the epoxy smooth (definitely the most time consuming part of the process), we put on a different color paint then we normally use to paint the bottom (for a visual indicator to let us know when we are getting close to the epoxy layers) and then painted the bottom with our usual bottom paint.

Did this make a difference in keeping our boat blister free? Who knows - but it certainly didn't hurt. (other than my aching arms and back!)
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Old 02-11-2006, 11:56   #9
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Lynx, A bit of advise for what it is worth. You did not say if your boat has blisters or not. But "if it ain't broke don't fix it". Leave the boat alone if blisters have not been a problem. Poor prep and or poor product application can create problems you didn't have before. No boat has ever sank from blisters and the cure is no costlier than an attempt ot stop a problem that you might never have. If on the other hand you do have an issue than be cautious as to who you have do the job. Talk with the owners of other boats that have had the work done from them and what the results have been after more that two years.
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Old 02-11-2006, 16:39   #10
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Yeah, I agree with Chuck here. If it ain't broke, don't fix it. How many people have done barrier coats like this that don't have blister problems at all, just out of fear of them? Are there many of you out there?

I know when I looked at buying my boat, I was careful to avoid any boat with an epoxy barrier coat, as it was a sign in my mind that the boat once had trouble.
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Old 02-11-2006, 21:23   #11
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Thanks for the replies, please keep them comming.

I have an 06 MacGregor 26M. I keep it on the trailer, no blisters and have been cruising for 7 weeks this year and plan on another 3. All in South Florida.

I am hopeing to go cruising in another year and expect (hope) that I can keep cruising for 3 to 5 years.

The Mac 26M is a good costal cruiser but is designed to be used as a weekender. There has been some problems with minor blisters. No reports if these have been in the glass or just surface. The factory does recommend a barrier coat if the boat will be kept in the water. Some of the older Mac's have had blister problems. I am trying to avoid proplems when I need to replace the anti-foul paint.

Again, thanks for the replies from people who do not make their living repairing boats.
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Old 03-11-2006, 17:27   #12
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Lynx,

Barrier coat and anti fouling paint is what we all use too. I can't see why you wouldn't do it too once you keep the boat in the water full time. Small boats around here use boat lifts to avoid the hassle. I've seen a few 40 ft sail boats on lifts as well.
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Old 14-11-2006, 19:33   #13
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What, avoid buying a boat with a barrier coat... ARE YOU INSANE???? Just because a boat has a barrier coat does not mean there was a problem. I did mine to avoid any problems and to reduce maintenance work. When I hauled out the other day after 2 years in the hot water of the Florida keys I had ZERO blisters... ZERO.

If you want to get rid of a problem, get rid of what creates a problem. Get rid of the gellcoat. Grind it off man. It is evil stuff!!!!

Barrier coats are a lot of work but worth every cent!!! Since I did it... ZERO blisters. I charge $250 to $500 a foot to do a good 4 layer barrier coat.

To pass on a boat because it has one is a big big mistake. Just because you have blisters does not mean you have a bad boat. You have a better boat with a barrier coat.
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Old 14-11-2006, 22:14   #14
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Roy - We don't appreciate or allow (please see our rules) insults to other members. Since there is some information in your post, I'm leaving it. May I suggest that you remove the offending part?
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Old 23-11-2006, 21:07   #15
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I am not sure where you see I am insulting another member, in any case it was not my intent. My wife tells me I am insane all the time... I was never offended by it... I had to be to marry her!

Anyway, looking at some of the other posts I think a basic summary can make things a little clearer,

Epoxy barier coats can be done by the owner (very time consuming and a labor intensive) But to me it is friendlier than using vinylester for a barier coat. When I say remove the gelcoat I am talking about mainly gel on polyester BUT I still see no reason to have gellcoat on the bottom of ANY boat that is in the water full time and has a bottom covered in bottom paint???? It makes no sense at all. It is the weakest link, weakest link, weakest link.

So without spending a lot of money, well compared to what a new house costs, and kissing your weekends away for a couple of months, if you have a polyester boat the best thing to do is remove the gellcoat, cover the "virgin" glass with a 8 oz finish cloth and epoxy (optional) and then do 4 to 6 layers of epoxy. On the last layer just rinse the blush off the epoxy and DO NOT SAND it before you apply the bottom paint. Sanding the last layer increases the surface area of the last epoxy coat and will allow it to gain moisture faster than if you just leave it alone. So what if the bottom paint falls off over time, less of that nasty stuff to sand next time you haul out.

The best thing to do for bottom paint over a barrier coat is apply a red tracer coat of hard bottom paint like trinidad (bonds to epoxy well) and then 3 coats of ablative. Next time you haul out you just powerwash off all the old ablative to the tracer coat and then paint more on... ZERO SANDING and in and out, or should I say out and in, in 2-3 days!!! But this will cost you $1,000 to $2000 in paint alone for the first bottom job you do after the barrier coat on your average size boat (35 to 45 foot).

A good rule of thumb is that if you havent put on at least a gallon of epoxy per foot (2 gallons for 45 footers and up) then you have a basic lightweight job that will last about 3 to 5 years. My method should give at least 10 years but I have never had any blisters or warranty work so at this point I am 100%... ask me again in 10 years.

As far as adding aluminum to epoxy.. well I know what they say it is supposed to do but I dont really agree with it. I think your better off adding a little cabosil (colodial silica) than aluminum. cabosil is used in concrete to reduce water needed for mixing and also results in a concrete that has a higher density.. and we all know how hard cabosil is to sand.

One other note, make sure you know what cabosil is... you have no idea how many people I have met that think microballoons are cabosil. WHATEVER YOU DO NEVER EVER NEVER EVER USE MICROBALOONS BELOW THE WATERLINE. Take this as word and dont listen to anyone who says different. Always do your hull repairs below the waterline with cabosil/epoxy on your basic fiberglass boat.

Trust me on this
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