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To barrier coat or not to barrier coat?

Stuart 28-2

Member II
I am asking for opinions on whether or not it is a bad idea to barrier coat just select areas of the hull before bottom paint.

I have repaired a handful of large blisters and don't want to leave the areas around them that are sanded down to gel coat vulnerable to further blistering. However, I don't believe I should barrier coat over other parts that still have a couple of layers of previously applied paint. Also, my plan is to haul out again in around 18 months to repair all blisters, meaning I would likely be trying to sand away some barrier coat I apply now.

Thanks for any input.
 

kapnkd

kapnkd
I am asking for opinions on whether or not it is a bad idea to barrier coat just select areas of the hull before bottom paint.

I have repaired a handful of large blisters and don't want to leave the areas around them that are sanded down to gel coat vulnerable to further blistering. However, I don't believe I should barrier coat over other parts that still have a couple of layers of previously applied paint. Also, my plan is to haul out again in around 18 months to repair all blisters, meaning I would likely be trying to sand away some barrier coat I apply now.

Thanks for any input.
We first removed all previous bottom paint before repairing gel coat blisters and any other areas in need of attention.

The Interlux barrier coat was then applied, let dry/cure per instructions and then sanded smooth (PITA to do) before new bottom paints were applied.

The barrier coat has worked well and blisters are a thing of the past for us for many years.
 

mjsouleman

Sustaining Member
Moderator
I did the same as Kapnkd and 1. had the peace of mind when I found 50 or so very minor blisters and 2. knew that I would not have to think of blisters for the remainder of the boats life.
 

toddster

Curator of Broken Parts
Blogs Author
I too did the whole bottom at once. If you’ve ever wondered why those darned trainers at the gym want you to do “overhead squats,” sanding the bottom of a boat is what they’re for. Doing one or two sessions a day, it took most of the summer.

IDK about attempting to “spot” barrier coat. Seems a bit futile.

However, a lesson learned: Paint the barrier coat well up above the waterline. I wish I’d done it to the top of the boot stripe. If the boot stripe area is not barrier-coated and it gets immersed, new blisters will form there.
 

kapnkd

kapnkd
I too did the whole bottom at once. If you’ve ever wondered why those darned trainers at the gym want you to do “overhead squats,” sanding the bottom of a boat is what they’re for. Doing one or two sessions a day, it took most of the summer.

IDK about attempting to “spot” barrier coat. Seems a bit futile.

However, a lesson learned: Paint the barrier coat well up above the waterline. I wish I’d done it to the top of the boot stripe. If the boot stripe area is not barrier-coated and it gets immersed, new blisters will form there.

YEP! ...Longest (painful) summer in my life too! ;-)) Yet in the end well worth the efforts and yes - we went all the way up to the stripe.

Matter of fact, when living in Miami where I kept the boat, it was constantly subjected to wave action going up and on the boot stripe. On my first haul out we cosmetically raised the complete stripe upwards six inches and brought the bottom paint up accordingly - problem solved and brings back a distant memory.

...TRUE STORY: While doing this work myself, an old and very salty looking gruffly dressed worker walks by. With stubby cigar hanging in a somewhat toothless mouth, captain’s hat cocked to one side, he casually glances over commenting to me with a chuckle, “Raising the pot line ehh??!!!” (Seems that was a then common trick to make many boats not look heavily loaded with “Square Grouper”.)
 

Afrakes

Sustaining Member
I am asking for opinions on whether or not it is a bad idea to barrier coat just select areas of the hull before bottom paint.

I have repaired a handful of large blisters and don't want to leave the areas around them that are sanded down to gel coat vulnerable to further blistering. However, I don't believe I should barrier coat over other parts that still have a couple of layers of previously applied paint. Also, my plan is to haul out again in around 18 months to repair all blisters, meaning I would likely be trying to sand away some barrier coat I apply now.

Thanks for any input.
If it's not possible to do the entire bottom at this time there is no harm barrier coating the exposed areas of repair.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
The bottom job for my boat cost the previous owner $15,000 at Marina Shipyard in Long Beach, CA.

The back pain involved was confined to the wallet area.
 

Afrakes

Sustaining Member
After futility trying to chemically and mechanically remove multiple layers from the 87' I hired a local mobile soda blaster. Fortunate to have the space, he did it in my yard. I spread out three tarps on the ground under the boat to catch the debris. For $1,200.00 I considered it a bargain.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
After futility trying to chemically and mechanically remove multiple layers from the 87' I hired a local mobile soda blaster. Fortunate to have the space, he did it in my yard. I spread out three tarps on the ground under the boat to catch the debris. For $1,200.00 I considered it a bargain.
At boat yard labor rates of $100. plus per hour, this sounds like a big ol' bargain. :)
 

Stuart 28-2

Member II
I too did the whole bottom at once. If you’ve ever wondered why those darned trainers at the gym want you to do “overhead squats,” sanding the bottom of a boat is what they’re for. Doing one or two sessions a day, it took most of the summer.

IDK about attempting to “spot” barrier coat. Seems a bit futile.

However, a lesson learned: Paint the barrier coat well up above the waterline. I wish I’d done it to the top of the boot stripe. If the boot stripe area is not barrier-coated and it gets immersed, new blisters will form there.
I too did the whole bottom at once. If you’ve ever wondered why those darned trainers at the gym want you to do “overhead squats,” sanding the bottom of a boat is what they’re for. Doing one or two sessions a day, it took most of the summer.

IDK about attempting to “spot” barrier coat. Seems a bit futile.

However, a lesson learned: Paint the barrier coat well up above the waterline. I wish I’d done it to the top of the boot stripe. If the boot stripe area is not barrier-coated and it gets immersed, new blisters will form there.

Just to be sure I'm on the same page: you are referring to rasing the boot stripe so it is above where the barrier coat ends, like Kapnkd describes below?
The reason I bring this up is I have read gel coat can't be applied over epoxy as the bond will be poor.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
The reason I bring this up is I have read gel coat can't be applied over epoxy as the bond will be poor.
Well meaning advice from other sailors, but it's not always true. I have applied gel coat over an epoxied surface with no problem later. I surmise that it gets back to cleaning, sanding, and just good surface prep, first.
Perhaps all of us, including me, have to learn to do a very complete job of prepping before applying a surface coating... of any product... :)
 

Gaviate

Member II
If it's not possible to do the entire bottom at this time there is no harm barrier coating the exposed areas of repair.
Agreed, Its good practice to do all the right things for the spot that you are working on...if the rest has to be later then so be it, but the steps needed don't change just because its a small area. Some overlap should be expected with this but your boat will thank you with no returning blisters.
 

toddster

Curator of Broken Parts
Blogs Author
Just to be sure I'm on the same page: you are referring to rasing the boot stripe so it is above where the barrier coat ends, like Kapnkd describes below?
The reason I bring this up is I have read gel coat can't be applied over epoxy as the bond will be poor.
No, I mean covering up the bootstripe (gelcoat) with the barrier coat, then repainting it either in the original position or higher up.
I tried to do it with just bottom paint, without the barrier coat, and it didn't work out.
 

nquigley

Sustaining Member
If it's not possible to do the entire bottom at this time there is no harm barrier coating the exposed areas of repair.
I guess there's nothing to stop one doing that, but it'll waste a lot of expensive paint. I don't think barrier coat comes in less than 1 gallon pots. Also, I don't think you can use only part of a pot (and safe the rest for another time) because it's a 2-part product: all of both parts need to be combined because the paint settles in it's can.
 

Gaviate

Member II
I don't think barrier coat comes in less than 1 gallon pots.
Well actually, I did the bottom on Emgee this past spring using Total Boat's Barrier/primer combo and was available in quart size as well as gallon but you're right in that the entire container had to be used or tossed, no saving for later once mixed.....
 

Alan Gomes

Contributing Partner
My experience,
6 weeks, sanding, washing, barrier coat, paint, 3 months of back ache, ibuprofin, and whisky.
My experience as planned for spring 2023 (and based on a previous experience on a different boat from 2007):

This is the "Six Step Ensenada Method"

1. Load two of my good sailing buddies on the boat, together with copious amounts of food and adult beverages.
2. Sail the boat to the excellent Baja Naval yard in Ensenada.
3. Point at the bottom of said boat and say, "Kindly remove all the old layers of paint, then barrier coat and repaint, por favor."
4. Meanwhile, consume large quantities of delicious roasted chickens from a dandy eatery up the street, followed by some tasty Cuban cigars.
5. Gladly pay the yard bill (which in 2007 was about 60% of what the identical work would have cost in Southern California).
6. Load my buddies back on the boat and harbor hop back up to San Pedro.

Works for me!
 

Tin Kicker

Sustaining Member
Moderator
Hi Stu -

Lots of good advice and hard experience of others, in that they decided to do a full job at once, but that was not your question.

Yes, barrier coat can be applied to sanded areas, then have bottom paint over it.

Especially here in the sorta-fresh/brackish Chesapeake waters since you expect to pull the boat again before too long & when the bottom paint should be totally shot, assuming occasional bottom cleanings. From the technical perspective, the spot barrier coat being applied is going to cover & protect the exposed glass, then extend to become a layer over where the sanding exposed the existing barrier coat, then over any existing bottom paint, and all of it will be beneath the new bottom paint.

& fwiw - I've been really happy with the Total Boat paints and epoxies but not yet used their barrier or bottom products.
 
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