Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 04-11-2015, 10:19   #31
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 6,057
Re: Barrier coat now or later?

Quote:
Originally Posted by donradcliffe View Post
I think most posters who say to leave the gelcoat alone have never had a boat in the tropics where osmosis proceeds an order of magnitude faster. Sanding it down (RO 60 grit and shop vac to the sander) would take me about 2/3 days. Barrier coat it-as mentioned, bottom paint really sticks to a green barrier coat.
I would have to disagree. The gelcoat is the reason he has no blisters to date. Why disrupt a good thing. A barrier coat is epoxy and will adhere to the gelcoat. I cannot see braking that barrier and getting down to a layer that will wick water. Maybe we a speaking the same thing? 60 grit is reasonably fine and may provide some tooth for the barrier coat. MHO
__________________

__________________
Cadence is offline   Reply With Quote
Old 04-11-2015, 10:22   #32
Guy
Registered User

Join Date: Feb 2013
Location: So. Oregon, USA
Boat: Seafarer36c
Posts: 4,308
Re: Barrier coat now or later?

Quote:
Originally Posted by donradcliffe View Post
I think most posters who say to leave the gelcoat alone have never had a boat in the tropics where osmosis proceeds an order of magnitude faster. Sanding it down (RO 60 grit and shop vac to the sander) would take me about 2/3 days. Barrier coat it-as mentioned, bottom paint really sticks to a green barrier coat.
Well I'm one of those who is in the tropics and I have more paint problems than gel coat problems. My gel coat is just fine, it's the barrier coat that has blisters. Yes it's hot water, sometimes 90 deg.
__________________

__________________
Guy is offline   Reply With Quote
Old 04-11-2015, 10:35   #33
Registered User

Join Date: Apr 2011
Posts: 2,243
Re: Barrier coat now or later?

Quote:
Originally Posted by Cadence View Post
The gelcoat is the reason he has no blisters to date.
The reason he doesn't have any blisters is that the original fibreglass layup was a top quality job.

You need two things to get blisters :

1) Moisture content in the hull. All boats have this to some degree.

2) Voids and other flaws in the layup. These then interact with osmosis to make blisters.

It's almost unheard of for a Bristol of that vintage to get blisters. Mine certainly never has. If the boat has a properly done layup, it simply won't ever get blisters. It can't.

However, having said that, if I had gone to the trouble of stripping the current bottom paint, and was heading to the tropics, I think I'd put a layer of barrier coat on. Why not?
__________________
Bristol 31.1, SF Bay.
MarkSF is offline   Reply With Quote
Old 04-11-2015, 13:59   #34
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2007
Location: Santa Cruz
Boat: Boatless Again
Posts: 4,314
Re: Barrier coat now or later?

Quote:
Originally Posted by Guy View Post
Well I'm one of those who is in the tropics and I have more paint problems than gel coat problems. My gel coat is just fine, it's the barrier coat that has blisters. Yes it's hot water, sometimes 90 deg.
I said most, I didn't say all. How old is your boat and what kind of resin was it built with??

My own experience with the Bene was that the gel coat broke down after 20 years and had tiny cracks in it. They weren't impact cracks, but they let water through. Barrier coating the gel coat didn't work, and I ended up planing it off.
__________________
donradcliffe is online now   Reply With Quote
Old 04-11-2015, 14:16   #35
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 6,057
Re: Barrier coat now or later?

Quote:
Originally Posted by donradcliffe View Post
I said most, I didn't say all. How old is your boat and what kind of resin was it built with??

My own experience with the Bene was that the gel coat broke down after 20 years and had tiny cracks in it. They weren't impact cracks, but they let water through. Barrier coating the gel coat didn't work, and I ended up planing it off.
Just to stir the pot. I would guess gelcoat is more likely to brake down exposed to UV. If he has had no problems why do anything other than add another layer of protection. It is just being proactive.
__________________
Cadence is offline   Reply With Quote
Old 04-11-2015, 14:29   #36
Registered User

Join Date: Apr 2011
Posts: 2,243
Re: Barrier coat now or later?

I believe that the usual reason for fine cracking of gelcoat is that the cure process effectively continues indefinitely, albeit slowly. The gelcoat shrinks as it cures. The process is speeded up by heat. Hence boats that have been in the tropics can show cracking.

This cracking is not due to UV oxidisation, which is a different mechanism. It would happen where the hull gets hot, but is not directly exposed to UV.

For example, my boat has fine cracking on the forward part of the cabin where it is most exposed to the sun. I have sanded through the layer of dull, oxidised gelcoat, to shiny stuff. But there are still fine cracks.
__________________
Bristol 31.1, SF Bay.
MarkSF is offline   Reply With Quote
Old 04-11-2015, 14:36   #37
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 6,057
Re: Barrier coat now or later?

Quote:
Originally Posted by MarkSF View Post
I believe that the usual reason for fine cracking of gelcoat is that the cure process effectively continues indefinitely, albeit slowly. The gelcoat shrinks as it cures. The process is speeded up by heat. Hence boats that have been in the tropics can show cracking.

This cracking is not due to UV oxidisation, which is a different mechanism. It would happen where the hull gets hot, but is not directly exposed to UV.

For example, my boat has fine cracking on the forward part of the cabin where it is most exposed to the sun. I have sanded through the layer of dull, oxidised gelcoat, to shiny stuff. But there are still fine cracks.
UV or heat? I can't see someone grinding down bottom gel coat exposed to neither that hasn't failed to keep out blisters? JMHO
__________________
Cadence is offline   Reply With Quote
Old 04-11-2015, 16:12   #38
Guy
Registered User

Join Date: Feb 2013
Location: So. Oregon, USA
Boat: Seafarer36c
Posts: 4,308
Re: Barrier coat now or later?

[QUOTE=donradcliffe;1954031]I said most, I didn't say all. How old is your boat and what kind of resin was it built with??

I thought I acknowledged the "most" part? Our boat is pre-revolution polyester. Not sure when the bad rap for gel started. I know a guy with a 40' Valiant from back in the day, they used some discount resin in the lay-up of his boat and he gets blisters above and below the waterline. He has to redo the whole boat every 5 years. It doesn't matter how much barrier coat he puts on.
__________________
Guy is offline   Reply With Quote
Old 04-11-2015, 16:38   #39
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 6,057
Re: Barrier coat now or later?

[QUOTE=Guy;1954141]
Quote:
Originally Posted by donradcliffe View Post
I said most, I didn't say all. How old is your boat and what kind of resin was it built with??

I thought I acknowledged the "most" part? Our boat is pre-revolution polyester. Not sure when the bad rap for gel started. I know a guy with a 40' Valiant from back in the day, they used some discount resin in the lay-up of his boat and he gets blisters above and below the waterline. He has to redo the whole boat every 5 years. It doesn't matter how much barrier coat he puts on.
He has a bad lay-up. Rolling the air out wasn't done. I guess I can see the vacuum bagging today.
__________________
Cadence is offline   Reply With Quote
Old 04-11-2015, 16:45   #40
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,352
Re: Barrier coat now or later?

The Valiant problem was boats used with mil spec fire retardant resin. I think they built a lot of Viet Nam boats with that. Maybe they used left over resin? At any rate it didt work out well.
My Rawson had quite a few small blisters when purchased, Quick sand and fill and recoat and I went South. After being south about 2 years and returning to Seattle, it had many blisters and very large deep ones. Some might have been 3/16" deep and 8" long x 2" wide!
It dried out about 4 months or so, I glassed and filled the big ones and filled the small ones with "marine bondo". 3 coats of real epoxy resin and it never broke out again (for 3 years anyway, don't know after that)
A non blister boat I had was repainted all over. I had the bottom stripped at the time and had them put on Interlux barrier, then primer, then bottom paint. On my first haulout there were a few (maybe 25 blisters) but they were not in the glass, just the barrier coat. It seemed a bit "rubbery" to me.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 04-11-2015, 16:54   #41
Guy
Registered User

Join Date: Feb 2013
Location: So. Oregon, USA
Boat: Seafarer36c
Posts: 4,308
Re: Barrier coat now or later?

Quote:
Originally Posted by Cheechako View Post
The Valiant problem was boats used with mil spec fire retardant resin. I think they built a lot of Viet Nam boats with that. Maybe they used left over resin? At any rate it didt work out well.

That's the story. The good part of that story is he got a hell of a deal on a beautiful boat, he just has to pay the Piper every once and a while.
__________________
Guy is offline   Reply With Quote
Old 05-11-2015, 18:04   #42
Registered User
 
Nicholson58's Avatar

Join Date: Jan 2011
Location: Live aboard
Boat: Camper & Nicholson58 Ketch - ROXY Traverse City, Michigan No.668283
Posts: 3,466
Images: 83
Re: Barrier coat now or later?

Quote:
Originally Posted by Guy View Post
So you are saying all gel coats blister?
In short -
YES
Its different when the boat spends 360 days/year in warm water. No further issues after 6 coats of Interprotect 2000E.
Attached Thumbnails
Click image for larger version

Name:	IMG_0045 ex.jpg
Views:	130
Size:	411.9 KB
ID:	112315   Click image for larger version

Name:	P1010072.jpg
Views:	131
Size:	415.7 KB
ID:	112317  

__________________
Nicholson58 is offline   Reply With Quote
Old 09-11-2015, 08:08   #43
cruiser

Join Date: Jan 2012
Location: Lake Ontario
Boat: Douglas 32 Mk II
Posts: 1,921
Re: Barrier coat now or later?

Quote:
Originally Posted by Cthoops View Post
Our new-to-us Bristol 29.9 has very likely spent her whole life in the northeast. She currently does not have a barrier coat, and she doesn't have any blisters.

The plan is to cut the lines and head for warmer climates in May 2021, so we'll definitely want to put on a barrier coat before we leave.

Whoops. Yes, do a barrier coat if going from cool fresh water to warm sea water. My response above is to customers who are staying in Lake Ontario.

The bottom paint job by the prior owner's yard left a lot to be desired with patches that are flaking off down to the gelcoat, so it seems like a logical time for us to remove the existing bottom paint and put on a proper barrier coat before repainting.

Sure.

How long can we expect a barrier coat to last? 10 years? Longer?

No set life expectancy. Depends on how well the job is done. If the hull is still wet when barrier coated, it will most definitely blister up again. If desert dry, the barrier coat could last forever.

I don't want to undertake this big DIY job too soon only to be hauled out in who-knows-where having to sand everything down to the fiberglass again.
Not sure if this was intended to be literal, but do not sand down to the fibreglass, just until you touch the gelcoat.
__________________
ramblinrod is offline   Reply With Quote
Old 09-11-2015, 08:38   #44
cruiser

Join Date: Jan 2012
Location: Lake Ontario
Boat: Douglas 32 Mk II
Posts: 1,921
Re: Barrier coat now or later?

[QUOTE=HappyMdRSailor;1953679]Pretty encouraging ain't it?

ramblin'.... a really great post, but I don't understand the logic of this one particular point ???

So if a boat isn't worth 100k+, it isn't prudent to prevent possible blistering and all of the time, expense, and work to repair a sub 100k boat after it does develop major problems?

Response was my standard for customers staying in fresh water (Lake Ontario). RE: Cost/Benefit Justification. This is to customer's querying about "hiring bottom job completion". There is a good chance that a 20 year old hull that has not blistered already, never will; so it becomes a risk/benefit decision.

The average person owns a boat for about 6 years. Chances are, the boat will not blister in the next 6 years, and will sell for the same amount, whether barrier coated or not. Only in the unlikely event that the hull does suddenly blister in those 6 years, only then would the barrier coat pay back.

(Few prospective buyers will pay more for a barrier coated perfect bottom, than a non-barrier coated perfect bottom.


I counter that with.... The person owning a sub 100k boat takes a harder hit on the wallet and back (arms) because he's the one that's got to perform the "un-affordable"... nightmare...

Depends on owner skills, perspective, and what they value their time at. If an owner wants the DIY experience, and doesn't consider the value of their time, then a barrier coat can be easily cost/benefit justified in almost all cases.
__________________
ramblinrod is offline   Reply With Quote
Old 09-11-2015, 09:27   #45
Registered User

Join Date: Aug 2014
Location: Groton, CT
Boat: Bristol 29.9
Posts: 236
Re: Barrier coat now or later?

Quote:
Originally Posted by ramblinrod View Post
Not sure if this was intended to be literal, but do not sand down to the fibreglass, just until you touch the gelcoat.
OP here. Yes, thank you. I didn't mean to put "fiberglass" - I meant gelcoat. We will just sand down to the gelcoat. I'd edit the post if I could.

We got started scraping on Saturday and managed to complete 20% in 3 hours. It was definitely work, but not quite as bad as I anticipated. At that completion rate, we'll be ready to start sanding after another 12 hours.

Sure glad it's a 29.9, and not something larger!

Thanks.
__________________

__________________
Our blog: http://www.adventuresontheclub.com
Cthoops is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Do I Really Need an Epoxy Barrier Coat ?! Help Needed ASAP ! windtraveler Construction, Maintenance & Refit 29 14-01-2013 15:44
Fairing Under or Over Barrier Coat Sandero Construction, Maintenance & Refit 4 30-04-2010 15:55
Barrier Coat Longevity Keegan Construction, Maintenance & Refit 7 21-06-2007 05:24
Barrier Coat Project Benny Construction, Maintenance & Refit 11 11-03-2007 19:55
Epoxy barrier coat and blisters StoutWench Construction, Maintenance & Refit 10 02-08-2005 21:28



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 18:51.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.