Barrier coat over antifouling!?!?

[Sailing ixion]

Hi everyone. Work is progressing on rehabbing our E34-2. One of the projects on my list is redoing the bottom since the antifouling was failing (large chips/flaking).

Im using Aqua Strip to do the majority of the job and then plan on sanding the rest to get as fair a surface as I can. But I’m running into a bit of a problem. It looks like sometime in the life of this boat someone used barrier coat on top of old antifouling and it’s that old antifouling that is failing, but it isn’t universal. Because of this the paint thickness is varying greatly leaving a very uneven unfair surface. Should I remove the barrier coat and get all the way to gelcoat or at the very least fairing compound?

im looking to fix this the right way, but I don’t want to needlessly overwork the problem. I feel like I should get to a point where all the antifouling is gone and start clean even if I run into a barrier coat. Am I making more work for myself?

 

[appick]

In short yes.

The only way a barrier coat is going to properly adhere to the hull is with a good mechanical connection to the gelcoat. All of the previous barrier coat that was put over the old anti fouling needs to come off. It'll be much more work for you now, but much less than doing the job twice.

 

[Sailing ixion]

In short yes.

The only way a barrier coat is going to properly adhere to the hull is with a good mechanical connection to the gelcoat. All of the previous barrier coat that was put over the old anti fouling needs to come off. It'll be much more work for you now, but much less than doing the job twice.

That’s what my gut was telling me, thanks for the confirmation. Glad I’m starting this now and not in the spring!

 

[appick]

That’s what my gut was telling me, thanks for the confirmation. Glad I’m starting this now and not in the spring!

Perfect time to get it done! Start planning out your stages of the project and factor in plenty of time and spare sand paper. Having a whole winter to work on it makes it a bit easier.

One thing that will make the job go much easier and quicker will be a LARGE sander. I've used my Bosch 7" with a option for a powered orbital "turbo" mode to paint 6 boat topsides and decks. It was a bit of a pain to separate from the money at the purchase but has more that paid for itself in quickly completing the work. As for doing a bottom job I'd possible look at a large 9" orbital sander to really put the sanding into overdrive, however they can be trickier to handle.

Either way hook any sander up to a shop vac and one of the dust collector bucket setups they sell in any big box home improvement center. Proper PPE, eye protection, coveralls, and quality comfortable 3m mask (might be worth springing for the full face shield type) is an absolute must when dealing with bottom paint.

 

[dcoyle]

You can also contact customer support for whichever barrier coat you decide to go with, and get instructions on surface prep. I have used both Interlux 2000 and the Seahawk product. I would choose the Interlux, it is much easier to sand than the Seahawk. Full body protection too, you dont want to breath the dust or get in your eyes or on skin.

 

[klb67pgh]

Another data point for you. I sanded our E25 hull this spring, removing 2-3 coats of ablative anti foul paint, and I think a grey barrier coat below that, to get back to gel coat. The barrier coat was spider cracked in many areas. The gel coat looked great except for a few scrapes amidships. I ground out those cracks, and filled with thickened epoxy, and then Total Boat TotalFair. I started with a 5" harbor freight orbital sander with not good dust collection and relatively quickly purchased a 6" DeWalt orbital with good dust collection hooked to my shop vac. I used 80 grit to start, and switched to 40 grit in some places where the paint was more stubborn before finishing with 80 grit. It got the job done well enough. A Bosch might have made the job easier. I think a pad much bigger than 7" wouldn't really help given the curves in the hull. The stern on my boat was the most difficult given the curves and I ended up using a Dura-Block sanding block and hand sanding that area. I applied Interlux Interprotect 2000E, alternating between grey and white coats, and then 2 coats of VC-17. The grey interlux covered very well and I really liked how the paint applied and sanded. Given all the work to sand and paint, I'd be inclined to take your boat back down to the gel coat - then you'll know you have a good base for many years.

 

[frick]

Soft paint can go over hard, never hard paint over soft