Paint compatibility

[Roger Long]

Over a half dozen people and sources have universially agreed that you can not put VC-17M over any other paint except itself because it has such aggressive solvents in that the older paint will lift.

When I decided to bring my bottom paint all the way up to the top of the boot top last year to avoid stern "fringe" from weight that has accumulated in the stern (windvane, etc.), I used Pettit copper paint for the boot top. I would like to use VC-17M all the way up.

The VC-17M almost flash dries so it is hard to see how the solvents are going to have much effect on the Pettit. There also has not been any sign of the inevitible slight overlaps at the junction lifting the Pettit. I plan to try a small test patch of the VC-17M without the copper. I'm pretty sure it won't cause a problem.

My question is: Is it possible for the solvents in a paint that dries within just minutes to work their way down without causing apparent loosening of the underlying paint but break its bonds in such a way that I'll find paint falling off in dual layer patches days or weeks later after the boat is in the water?

 

[Maine Sail]

What..

What was the Pettit copper paint? Was it an ablative? Solvents can do damage to underlying coats of paint. As a kid I saw it often when restoring antique cars with my father. We would always test a small part first to see if it lifted.

If you want to apply VC-17 I would personally choose to do a full strip. Why do you want to move away from a traditional paint? VC will require some diving and cleaning when use in the ocean where an ablative will self polish. We have a lot of racers in Falmouth and they are constantly diving on the VC paints to wipe them clean. A friend of mine has to dive on his four times per season. This is probably not something you'd want to be doing in Labrador or Newfoundland..

Just curious as to the switch?

 

[sailingdog]

Over a half dozen people and sources have universally agreed that you can not put VC-17M over any other paint except itself because it has such aggressive solvents in that the older paint will lift.

When I decided to bring my bottom paint all the way up to the top of the boot top last year to avoid stern "fringe" from weight that has accumulated in the stern (windvane, etc.), I used Pettit copper paint for the boot top. I would like to use VC-17M all the way up.

The VC-17M almost flash dries so it is hard to see how the solvents are going to have much effect on the Pettit. There also has not been any sign of the inevitible slight overlaps at the junction lifting the Pettit. I plan to try a small test patch of the VC-17M without the copper. I'm pretty sure it won't cause a problem.

My question is: Is it possible for the solvents in a paint that dries within just minutes to work their way down without causing apparent loosening of the underlying paint but break its bonds in such a way that I'll find paint falling off in dual layer patches days or weeks later after the boat is in the water?

The real problem is that the solvents work both inwards towards the hull, through any existing paint, as well as outwards through the new paint layer. While the surface may dry fairly quickly, there is still quite some solvent dissolved and trapped beneath the paint that takes much longer to outgas or blow off. It is this minor amount of solvent that really does the damage to the underlying paints, often damaging them or their bond to the hull, leading to widespread flaking and peeling later on. This is especially true on the softer ablative paints.

Generally, it is wisest to get down to bare gelcoat or barrier coat if you're not sure what the interaction between the paints will be. Surface preparation is 95% of the work and is what ensures the quality of any paint job—bottom paint included. According to this PDF from Interlux, basically, the only paint that VC-17 is really compatible with is itself.

I, too, am curious why you'd want to go with a non-ablative paint, like VC17, particularly if you're not racing. IIRC, it is a hard epoxy paint that will build up slowly over the years. I also don't know how well it handles being hauled out for extended periods of time. Maine Sail's point about not wanting to dive to scrub/polish the bottom paint in the waters your in is a good one... pretty cold up there almost any time of year.

 

[tsmwebb]

an ablative will self polish.

I've yet to find an ablative that will really self polish. I dive my boat's bottom regularly (and did so even in the Bay Area where it isn't balmy or fun by any means).
I've tried several ablative paints (currently Micron Extra) and have used hard epoxy paints and CopperBot. To me the advantages of ablative are the much easier scrubbing and multi-year coverage. They do sluff stuff off a bit, but even on a boat that hits double digits on a pretty regular basis the bottom doesn't self clean to an extent that I'd be happy with. This all goes with a big YMMV local conditions vary significantly.

--Tom.

 

[Roger Long]

Why do you want to move away from a traditional paint? VC will require some diving and cleaning when use in the ocean where an ablative will self polish. Just curious as to the switch?

It's just the boot top we're talking about here. The boat came from the Great Lakes where VC 17 is universal. Stripping and switching to ablative was high on the list this winter but the radar used up the time and money. Next year.

I wanted to switch to the no boot top all anti fouling scheme I'm used to on commercial boats and to solve the problem of the back half of my boot top being slightly immersed. Because of the warnings about VC 17 solvents, I put a Pettit red copper non-ablative over the OEM boot top. I'd like to just skip that step this year with the double masking, pulling away of paint, and unprotected line at the junction. I'm in quick and dirty mode below the rail this year. The boat is going up to Canada to raft up with fishing boats and I'm just not going to get too compulsive about anything that is going to get banged up anyway.

I put a test patch of VC 17 M extra without copper on the Pettit this morning. An hour later is was hard as a rock and felt no different when scraped off with a putty knife than the stuff put on last spring. Scraping onto and off of the test patch with a putty knife and digging right down to the white gel coat gave absolutely no hint that the solvents had damaged the underlying paint.

I'm going to try it. We'll learn something and it's hardly a problem if patches do fall off the boot top. I'm planning to take everything off next winter anyway.

 

[Roger Long]

I, too, am curious why you'd want to go with a non-ablative paint, like VC17, particularly if you're not racing.

Actually, it is not a bad paint, at least up here in Maine. I had the boat cleaned in the middle of the 2007 season but didn't touch it last year and there was only a bit of slime and some barnacles just around an area with lots of thru hulls.

It's very thin and build up is minimal. I can take the old stuff back to almost no detectable thickness in a couple hours with wet Scotch brite pads on a sanding handle.

My only reason for wanting to switch is to have the option of heading south in the fall without having to haul first and not having to paint every year. Just bought $450 worth of VC 17 m, Ouch! I would have to switch to something else anyway if I headed to waters where fouling is worse unless I wanted to do a lot of diving to clean the bottom.

 

[Roger Long]

What was the Pettit copper paint?

Pettit Unepoxy 1628.

 

[tommays]

Well


Perfection topside paint can fail Up to TWO years after application from solvent issues

 

[RichH]

Roger
Methinks possibly you have it backwards.

VC17 is a PTFE, etc. based coating therefore you cant put anything on top of VC17 due to the adhesion problems with 'anything' attaching to the PTFE base.

My ILYA Scow has had VC17 'over' a hard bottom paint .... for over 12+ years with absolutely no 'adhesion problems'. I recoat the VC17 often as Im always 'polishing/burnishing' the VC17 to keep it as smooth as a baby's ass.
Even with 'recoating' VC17 the very fast 'flash time' of the acetone will certainly attenuate any reaction with 'deeper' coatings.
For 'real life' evaluation, simply take a wad of paper towels, soak with acetone, overlay with polyethylene sheet and quickly seal it to the hull with tape to prevent the 'flash off' ..... wait a few days, etc. and then 'see' what happens. If you dont visualize any distortions or degradation of the existing coating, then you're probably 'good to go' with a VC17 application without need to remove the old coating.

 

[Barnacle Bill]

Not sure why anyone would want to put VC 17 over another type of paint. VC is excellent for racing, never builds up like most paints and because of her Telflon properties, is very fast stuff indeed and it has been shown to be very effective against zebra mussels. But, it is recommended more for fresh water rather than salt water use. Most other types of paints are not racing smooth and so you are negating the features of the racing slick bottom afforded by VC17 when applying it over another type of paint regardless of compatibility.