Bottom stripping questions...

[Sprinter99]

Hi,

We started to sand our bottom for a barrier coat (petit protect) then a trinidad sr application...

How deep should we sand? The photo attached shows a sample of my hull sanded. There was already a thin barrier coat applied a long time ago (white and grey) but what is the brownish paint? It is the one that takes the longest to sand..

Any tips or info will help. I am sanding with a orbital sander, tried a grinder with a sanding disc but it was a little rough.

Thank you!

[Franziska]

The brownish stuff is most likely a fairing compound with phenolic microbubbles in it.
Often this is thickened epoxy.

What type of boat is it and what hull material?

[rbk]

Grey coat is most likely epoxy primer, brown coat is epoxy barrier coat. Just take it down to the brown barrier coat and save yourself applying a new barrier coat and a ton of sanding. Touch up any barrier coat breakthroughs with epoxy and additive.

Edit: just saw how much you’ve done already. Ouch, that was some work. No need to continue taking it off. Looks well bonded as I’m sure you’re aware. I would re-prime the areas you’ve taken down and apply a new epoxy barrier coat on places you’ve sanded, paint and go sailing.

[shrspeedblade]

I did the same job (Ugh!) last November/December using Petit Protect/Trinidad. On the recommendation of the yard manager I went down to the gray layer but no further, which at least limited the misery and was a good idea as I felt the new barrier coat adhered more readily to that than the exposed gel coat areas anyway. Just make sure you get ALL color removed, I could see the result from the previous barrier coat not being done as carefully how it started to be compromised but fortunately no blisters!

I started with only 80 grit discs, which was ridiculously slow, but then dropped down to 50 and I believe even 35 grit for the initial removal which saved some pain and then back to 80 grit for final removal, edges, etc. Good luck- no other way to say that it sucks but the final result was worth it which is saying a lot!

[wingless]

Always follow all the manufacturer's instructions.

When I did mine (working alone) I discovered that I was having difficulty w/ the pot life on a full gallon, so I switched to half gallon batches and that was perfect.

Looong ago I purchased a Blair Tornado II Paint Shaker. This has been invaluable for bottom painting and especially for barrier coating the bottom.

When I did mine I took it down to gel coat using a Festool RO150FEQ vacuum sander and their dust extractor w/ the heavy duty vacuum bags and then applied six coats of Interlux 2000e Barrier Coat. The vacuum sander is AMAZING and makes the process sooo much better than dry sanding, almost NO mess.

One really handy tool is a club to beat off the hoards of people that enjoy boating throughout the season that want to help in the process.

When I do mine I remove everything except the cutlass bearing struts, so I can paint barrier coat up into the through hull fittings.

[Sprinter99]

Originally Posted by Franziska

The brownish stuff is most likely a fairing compound with phenolic microbubbles in it.
Often this is thickened epoxy.

What type of boat is it and what hull material?

It is a Watkins 36C and solid glass hull.

[Sprinter99]

Originally Posted by rbk

Grey coat is most likely epoxy primer, brown coat is epoxy barrier coat. Just take it down to the brown barrier coat and save yourself applying a new barrier coat and a ton of sanding. Touch up any barrier coat breakthroughs with epoxy and additive.

Edit: just saw how much you’ve done already. Ouch, that was some work. No need to continue taking it off. Looks well bonded as I’m sure you’re aware. I would re-prime the areas you’ve taken down and apply a new epoxy barrier coat on places you’ve sanded, paint and go sailing.

Ouch lol. That's what I imagined but I was questioning myself because I never saw brown colored barrier coat ! Thanks for the reply

[shrspeedblade]

I would strongly advise you to get an in person opinion from someone very experienced at doing barrier coats. I’m skeptical about leaving anything other than that light gray previous barrier coat. When I was prepping my boat for Petit protect I fully intended to go completely down to gelcoat everywhere and only altered based on being advised by a very experienced yard foreman.
If you try applying barrier coat over something it doesn’t adhere to well you are risking wasting a lot of money and even more effort. Don’t go by an Internet analysis. Even mine!

[wingless]

Originally Posted by wingless

Always follow all the manufacturer's instructions.

Originally Posted by shrspeedblade

I would strongly advise you to get an in person opinion from someone very experienced at doing barrier coats. I’m skeptical about leaving anything other than that light gray previous barrier coat. When I was prepping my boat for Petit protect I fully intended to go completely down to gelcoat everywhere and only altered based on being advised by a very experienced yard foreman.
If you try applying barrier coat over something it doesn’t adhere to well you are risking wasting a lot of money and even more effort. Don’t go by an Internet analysis.

Or just follow the manufacturer's instructions.

Another option is to directly contact the barrier coat manufacturer.

They have the most expertise w/ their product and any supplemental information they provide has more weight than that provided by others.

[Tetepare]

I did it. ONCE. Worst job I’ve ever had to do on a boat.

I’ve seen others use the sticky sheets that dissolve paint. It seems to remove most of the paint. Others report it doesn’t work well. I don’t care, if I had to do it again I’d take that risk and try the paint removing sheets.

[rbk]

Originally Posted by Sprinter99

Ouch lol. That's what I imagined but I was questioning myself because I never saw brown colored barrier coat ! Thanks for the reply

The barrier coat additive gives the epoxy a brownish copper look. Here’s a pic in this link:

https://www.google.ca/amp/s/www.prac...update%3famp=1

There’s no reason to remove the old barrier coat unless it is failing, which by the amount of sanding you seem to be doing it is well bonded. I would sand smooth what you’ve already done, apply new primer coat, where you’ve sanded and then apply new barrier coat where it’s been removed. Take the rest of the bottom paint off down to the old barrier coat apply new bottom paint following the instructions and get back on the water.