How far can you stretch bottom paint coverage by thinning?

There were only two cans of paint on my yard invoice for last year
when I looked back to see how much to buy this year. That didn't seem
like very much but it is supposed to go on quite thin. According to
the coverage table on the can, I should need about six cans.

I couldn't get the proper thinner so I put it on straight which seemed
quite thin and to work very well. I ran out about half way down the
second side. I drove back to Portland and bought the last two cans of
VC 17 M Extra in the city. Saving half a can for the bottom of the
keel and under the hull supports I was able to put the recommended two
coats on the keel, rudder, and forward part of the hull where fouling
creates the most drag. It will be interesting next fall to see the
difference between the single coat and double coated areas.

If the yard last year put on just one coat, it is possible that they
could have done it with two cans if thinning could stretch it from 75%
to full coverage. Is that possible or did they just forget to charge
me for a can?
Unless the yard forgot to bill me for two cans last year, the boat
only had a single coat which might account for the marginal
performance.

BTW thanks to whoever suggested the nail holes in the lid trick for VC
17 M. Not only did it keep this very volatile paint from skinning up
in the roller tray, I was able to keep shaking the can as I went. I
poured out just enough each time to wet the roller. Being able to
turn the can all the way over when pouring also helped keep the copper
distributed.

--

Roger Long

I just saw the typo in my post header. Must have been a Freudian slip
from the way I was feeling after wiping the boat down and putting on 1
1/2 coats of paint

--

Roger Long

Roger Long wrote:
I just saw the typo in my post header. Must have been a Freudian slip
from the way I was feeling after wiping the boat down and putting on 1
1/2 coats of paint

I was just about to congratulate you on finding a lotion to rub on that
obviously works!

In article ,
"Roger Long" wrote:

How far can you stretch bottom paint coverage by thinning?


Why?

(yes, I read the other posts) Bottom paint effectiveness depends upon
film thickness. As long as you decant the next few minutes' amount of
paint and close the can otherwise, you'll get a proper thickness.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

On Tue, 23 May 2006 06:03:09 GMT, in message

Jere Lull wrote:

In article ,
"Roger Long" wrote:

How far can you stretch bottom paint coverage by thinning?


Why?

(yes, I read the other posts) Bottom paint effectiveness depends upon
film thickness.

I'm not sure that's generally true.

With ablative paints the duration of protection depends on film
thickness, as they disappear in time.

With hard paints all the action is supposed to be at the surface, so
there isn't much plus to extra coats unless you are going to wear them
off. (Yes, I wore off VC17 from the bottom foot of the keel in
shallow, sandy, weedy places last season, but that was physical
antifouling, right? Yes, Lake Erie is Shallow)

Ryk

On Mon, 22 May 2006 02:38:35 GMT, in message

"Roger Long" wrote:

If the yard last year put on just one coat, it is possible that they
could have done it with two cans if thinning could stretch it from 75%
to full coverage. Is that possible or did they just forget to charge
me for a can?

I'm in fresh water, so one coat is enough. I got a full coat of VC17M
on the bottom of my Hughes 35 with 2 cans and no thinner. Admittedly
it was cold weather, but without special anti-evaporation tricks I
still had about 1/4 can remaining for under the pads and passing on to
the next boats in the launch parade. (Our club charges by crane time,
so our launch proceeds rather quickly...)

I think it may depend on the substrate. I used a lot more when I was
painting directly onto fresh InterProtect rather than last year's
VC17. Or maybe the weather was warmer.....

Ryk

Interesting. If your Hughes has a fairly modern underbody it should
be about the same wetted area as my E32. That makes it sound like the
yard did get it all done with two cans (one coat). There was just
about a quarter can left over for the pad areas.

I must have been putting it on thicker but it's hard to see how. The
temperature was at the lower end of the recommended range, I used the
shortest nap roller I could get, and the roller was just barely wet
out each time. It doesn't look thick and there are even some spots I
want to hit when we lift her out of the blocks.

It may be a matter of paying close attention to the overlap. Thinking
back, I may have been using the same technique I've used for walls.
If I overlapped strokes by 25%, that could account for the difference
in coverage. Maybe the yard thinned a little as well. No one in town
had the thinner for this paint.

It's a question of some interest as I used a hundred bucks more paint
than the yard did last year.

There's also the question of why Interlux tells you to buy six cans of
paint for a boat this size. The answer to that's pretty easy. Same
reason the dog food companies tell you to feed your dog twice as much
as the vets says is healthy

With two coats on the critical areas, I hope I get less fouling this
year.

--

Roger Long



"Ryk" wrote in message
...
On Mon, 22 May 2006 02:38:35 GMT, in message

"Roger Long" wrote:

If the yard last year put on just one coat, it is possible that they
could have done it with two cans if thinning could stretch it from
75%
to full coverage. Is that possible or did they just forget to
charge
me for a can?

I'm in fresh water, so one coat is enough. I got a full coat of
VC17M
on the bottom of my Hughes 35 with 2 cans and no thinner. Admittedly
it was cold weather, but without special anti-evaporation tricks I
still had about 1/4 can remaining for under the pads and passing on
to
the next boats in the launch parade. (Our club charges by crane
time,
so our launch proceeds rather quickly...)

I think it may depend on the substrate. I used a lot more when I was
painting directly onto fresh InterProtect rather than last year's
VC17. Or maybe the weather was warmer.....

Ryk

On Thu, 25 May 2006 00:41:52 GMT, in message

"Roger Long" wrote:

Interesting. If your Hughes has a fairly modern underbody it should
be about the same wetted area as my E32. That makes it sound like the
yard did get it all done with two cans (one coat). There was just
about a quarter can left over for the pad areas.

I must have been putting it on thicker but it's hard to see how. The
temperature was at the lower end of the recommended range, I used the
shortest nap roller I could get, and the roller was just barely wet
out each time. It doesn't look thick and there are even some spots I
want to hit when we lift her out of the blocks.

I use a very thin foam roller, and I hurry enough that passers by
think I'm being rude. That, and your point about overcoating -- you
can put on a whole lot more paint if you aren't aggressive about
spreading it out. With the new formulation it doesn't really dry in
the tray, but it dries on the hull in a real hurry.

Modern is relative ;-) The Hughes shows a distinct IOR era influence
with skinny ends and substantial overhangs, full skeg rudder and a
more or less square, swept back fin keel. I'd guess at about the same
area.

Ryk

"Ryk" wrote

That, and your point about overcoating -- you
can put on a whole lot more paint if you aren't aggressive about
spreading it out.

That's probably where the thinning comes in. It was drying so fast on
the hull (good drying day even though cool) that I couldn't move it
around much after it was rolled on.

It doesn't look very thick but, if it was only 25% thicker than the
yard put on, it would account for the coverage difference. In other
words, you don't have to add 25% thinner to increase coverage by that
amount with a fast drying paint like this which is what I was thinking
when I first posted.

I'll try foam rollers next year as well.

--

Roger Long