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New bottom paint, old barrier coats?

Sep 23, 2009
1,450
O'Day 34-At Last Rock Hall, Md
20201203_162056(1).jpg
This is the appreance of our hull every time she is hauled in the fall. Usually we power sand the bare areas, apply one cost then another coat over the whole bottom. The bottom paint is Pettit Hydrocoat and she has barrier coats. No blisters have been found. This will be our seventh season and I would like a more permanet solution. She could be soda blasted or chemical stripped. However I would like to avoid the application complexities of adding more barrier coats. Could a primer be used over the existing barrier coats before reapplying new bottom.
Thanks in advance for any advice.
 
Sep 23, 2009
1,450
O'Day 34-At Last Rock Hall, Md
Hydrocoat works great to keep barnacles and slime off but there are patches where new and old coats come with the pressure washing during fall haul out. I suspect po waited too long to apply bottom paint after barrier coats.
 

Ward H

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Nov 7, 2011
3,077
Catalina 30 Mk II Barnegat, NJ
Hydrocoat works great to keep barnacles and slime off but there are patches where new and old coats come with the pressure washing during fall haul out. I suspect po waited too long to apply bottom paint after barrier coats.
Hi Larry, My Catalina has the same problem and I suspect the same cause as you do.
i’ve been wiping down the bare spots with acetone/thinner before applying bottom paint. Seems to help. On my boat the loose paint/bare spots are mostly where the thickest paint is letting loose and are fewer each year. Hoping in another couple of years the thickest paint is gone, will save me the cost of having the bottom blasted clean.

This will be my 4th season using Hydrocoat. It has been working well here but the local shop reports a lot of boaters are happy switching over to Seahawk Monterey for the 25% cost savings.
 
Sep 23, 2009
1,450
O'Day 34-At Last Rock Hall, Md
Patches seem to be different random spots every year. I sand bear spots with 80 grit, apply one coat over bare spots then one coat over entire bottom. Soda blasting would be about 1700 but biggest headache for me would be two new barrier coats and timing of applications.
 
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Sep 23, 2009
1,450
O'Day 34-At Last Rock Hall, Md
Hi Ward. I just ordered Pettit hrt neptune. It is water based single season and half the cost of hydrocoat. I think maybe part of the problem is the slow speed and low milage results in min ablation leads to too thick leads to flaking. Hopefully hrt will ablate off faster. Will follow up with pic next fall haul if we still own her.
 
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dLj

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Mar 23, 2017
1,770
Belliure 41 Snug Harbor, Lake Champlain
Musetta has a similar bottom. At the yard I was just at that guy there told me I should get the bottom blasted to remove all the old paint the next time she is hauled. Soda blast or I guess walnut shells? That flaking is due to excessive build up of bottom paint. On my boat, it is not felt it has anything to do with how the bottom paint was applied after the barrier coat, it's simply 20 years of bottom paint buildup.

dj
 
Sep 23, 2009
1,450
O'Day 34-At Last Rock Hall, Md
Sounds reasonable but i wonder how may boats are soda blasted at high cost every ten to twenty years. After soda blasting comes two or more two part barrier coats then bottom paint that must be applied in a norrow hot coat time frame. Should ablative paint ablate away fast enough to prevent build up?
 

dLj

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Mar 23, 2017
1,770
Belliure 41 Snug Harbor, Lake Champlain
Sounds reasonable but i wonder how may boats are soda blasted at high cost every ten to twenty years. After soda blasting comes two or more two part barrier coats then bottom paint that must be applied in a norrow hot coat time frame. Should ablative paint ablate away fast enough to prevent build up?
Blasting is not very expensive. I guess that always depends upon your budget. But for my 41 footer I was given a ball park of about $3k. So, is that expensive? Given my other option of suiting up and sanding the whole bottom over a period of a few days, dealing with the respirators, clean up and everything else that goes into sanding a bottom I'm looking forward to getting a hard quote...

You also do not need to put another barrier coat on. Unless it needs it, and in that case better to know....

As far as ablative paint ablating away preventing build up, all I can say is my boat has only used ablative paint in the past 20 years and the build up can be measured with a ruler...

dj
 

Ward H

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Nov 7, 2011
3,077
Catalina 30 Mk II Barnegat, NJ
@njlarry,
I had my O'day 25 media blasted and @Scott T-Bird had his blasted by same yard. Both ended up bare gel coat. I'm not sure if a barrier coat was on either boat and taken off by the blasting.

As far as hot coating barrier coats, Interlux InterProtect 2000E can be over coated up to 6 months per Maine Sail. I just used some on a keel cleanup and the only mention to hot coating was after the last coat of IP2000E to put on bottom paint while the barrier coat was "thumb print" soft. I did find instructions for IP2000E a little intimidating but I think I would tackle it.

I checked my notes and only spot painted last year. This spring some of the black bottom paint put on 3 seasons ago was showing through the blue I've been using so I believe the Hydrocoat is sloughing off or coming off during power washing.
The Seahawk Monterey tech sheet says it is a harder ablative for fast moving boats. I'm sure a softer ablative will build up less on our slow boats.
I like the lower cost of the Neptune HRT. Noticed it has 25% copper compared to Hydrocoat being 40%. Interested in learning if it is softer and ablades faster for less build up. Looking forward to your fall report.
 

dLj

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Mar 23, 2017
1,770
Belliure 41 Snug Harbor, Lake Champlain
@njlarry,
I had my O'day 25 media blasted and @Scott T-Bird had his blasted by same yard. Both ended up bare gel coat. I'm not sure if a barrier coat was on either boat and taken off by the blasting.
@Ward H So what did the blasting cost for each boat?

dj

p.s. blasting is not supposed to affect the epoxy barrier coat is my understanding.
 

Ward H

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Nov 7, 2011
3,077
Catalina 30 Mk II Barnegat, NJ
So what did the blasting cost for each boat?
In the fall of 2012 I paid $1800 for my 25’ boat. Don’t know what Scott paid a year or two later for his 27’r.
 
Apr 21, 2014
182
Hunter 356 Middle River, MD
@Ward H So what did the blasting cost for each boat?

dj

p.s. blasting is not supposed to affect the epoxy barrier coat is my understanding.
I will count myself lucky as I just had my 36' done and it was $1250, but I had sanded a lot last year prior to launch except for some patches and the keel and there was not a lot of build up.

Jeff
LegaSea Bare Bottom.jpg
 
Oct 26, 2008
4,967
Catalina 320 Barnegat, NJ
@Ward H So what did the blasting cost for each boat?

dj

p.s. blasting is not supposed to affect the epoxy barrier coat is my understanding.
@Ward H , I'm surprised if you paid $1,850 just for the media blasting. I don't have the receipts in front of me but I think it was $1,400 for mine. Perhaps you had something else built into that price and perhaps I got a little break because I had them do the entire job. @dLj , there is no way in the world that you would ever find me sanding a 41' boat on my own! :biggrin: I could think of very few things that could be more tortuous! I would gladly pay $3K to avoid that job if I thought it was needed. But I will say that you might want to be prepared for the consequence. I don't think Ward had the same issue, but the blasting revealed thousands of tiny blisters just into the gel coat. They were about 3 mm diameter and were everywhere on the hull below the waterline. I think I spent around $2 K to have the hull faired with thickened epoxy before applying the barrier coats. After fairing the hull, I had 3 barrier coats applied before the ablative bottom paint. The result was very satisfying, but expensive. I think that if I had sanded the bottom smooth by getting down just past the built-up paint, I might not have exposed the blisters. It's hard to say. They were just into the gel coat. I didn't have any blisters into the underlying fiberglass. But, it was a little odd to see it. The exposed gel coat was white, the underlying fiberglass at each divot was a reddish color. I learned that the underlying resin has a reddish tint.
 

dLj

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Mar 23, 2017
1,770
Belliure 41 Snug Harbor, Lake Champlain
there is no way in the world that you would ever find me sanding a 41' boat on my own! :biggrin: I could think of very few things that could be more tortuous! I would gladly pay $3K to avoid that job if I thought it was needed.
My sentiments quite well put... I've done plenty of sanding of bottoms on boats of various sizes - I have done more than my share of penance.... I'm thinking the $3k may be high. That would be good....

But I will say that you might want to be prepared for the consequence. I don't think Ward had the same issue, but the blasting revealed thousands of tiny blisters just into the gel coat. They were about 3 mm diameter and were everywhere on the hull below the waterline. I think I spent around $2 K to have the hull faired with thickened epoxy before applying the barrier coats. After fairing the hull, I had 3 barrier coats applied before the ablative bottom paint.
A fundamental reason one does this is to reveal the consequences - in addition to getting the bottom into better shape for bottom painting. Otherwise it's just running around with your head in the sand not looking at the reality. As my boat has already had an epoxy barrier coat, it's been extensively examined, and I've had it surveyed professionally; I'm fairly certain of what I'll find. But time will tell, and I'm never one to shy away from reality....

dj
 

Ward H

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Nov 7, 2011
3,077
Catalina 30 Mk II Barnegat, NJ
@Scott T-Bird and @dLj
That's what I get for relying on my memory instead of checking my notes from back then.
I just did and found that I paid $825 for the media blasting, not $1,800.
 
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Oct 22, 2014
15,740
CAL 35 Cruiser moored EVERETT WA
You got a Steal.
Ward. How can you live with yourself? I'm guessing you may want to make a contribution to the retirement kitty or the beer fund for those boys who cared for your boat...
 
Sep 8, 2020
45
Merit 22 Honker Bay
I've been several years between boats and things seem to have changed. I always removed the bottom paint with grill blocks and water. $20 plus paint and I was ready to go back in.

Does no one do this anymore?
 

MitchM

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Jan 20, 2005
953
Nauticat 321 pilothouse 32 Erie PA
what's a 'grill block?' i think i need some. bottom of my new to me 04 boat is in rough shape...