IanM wrote:

Armond Perretta wrote (on 25 April 2009):
I use a foam
roller and about 3 quarts per coat on this full keel boat with a 22
foot waterline. At this rate every 3 years I've had enough paint on
hand to avoid buying a new gallon.

Well for what its worth, 5 litres of Jotun Seaguardian will do over 4
coats on a full keel 26 footer. That's two coats per year rolled on,

I read it as every third year he avoided buying a new can so that's 2 US
gallons for 3 years and he's reduced to 1 for 2 years by diluting it.

His narrative makes clear that he didn't actually write what he must have
meant: He did write "every 3 years", but obviously meant that after the
3rd year he had enough left not to need to buy more for the 4th year.

Year 1: He buys a gallon and uses 3/4 of it.
Year 2: He uses the rest, buys a 2nd gallon and uses 1/2 of that.
Year 3: He uses the rest, buys a 3rd gallon and uses 1/4 of it.
Year 4: He uses the 3/4 gallon left.

How he got 3 quarts left after two years and reckons to save half by
thinning, I do not know,

He has 3 quarts left after *three* years. But it's obvious that if
he uses the same volume of diluted paint per year as he previously
used of undiluted paint, then if he thins to 75% he can only save a
quarter, not half, and if he thins to 67% he would save a third,
not half. Dare he thin to 50%? It'll be so runny then that it
will probably need to be applied in several coats.

but unless he's measured what's left in the can
accurately I wouldn't believe his 3 quarts per coat.

I don't see why not. Since a quart is about a litre, as you say,
his 3 quarts per year is in the same ballpark as your 2.5 litres
per year.

Unless he's getting more paint on himself and the hard standing he's
slapping it on far thicker than we do as we are doing two coats.

Possibly, but it's neither here nor there whether he puts on one
thick coat or two thin ones, if the combined thickness is about
the same. Or he could have been using the word "coat" to mean
one year's coating even if it was in fact applied in two thin coats.

The biggest saving would be buy a radiator roller handle and the *GOOD*
(i.e. EXPENSIVE) rollers to go on it. A fully loaded large roller is to
heavy and awkward and cheap rollers break up too much and waste paint.
The extra length of the radiator roller handle makes the job go much
quicker with less stooping.

I was really pleased when I "discovered" (followed someone's advice
to use) radiator rollers (for the avoidance of doubt, we're talking
about the small ones, about 5 inches long and 1.5 inches in diameter,
the handle being about 2ft long). They're so much easier to use and
make a quicker job of it than brushes. I also tried ordinary full
size rollers and found them too heavy and went back to the small ones.
But then I tried the big rollers on a long handle, and they really make
fast work of it. They're not too heavy when you hold them with both
hands.

I use cheap rollers and don't understand what you mean about them
breaking up. Nor do I understand why using rad rollers should use
less paint overall.