SAIL - April 2015

highest gloss levels. They also maintain their color and gloss level longer

than single-part paints.

There are two main types of polyurethanes used in the marine in-

dustry—acrylic and polyester polyurethanes—and there are advantages

and disadvantages to both. Both have long lasting color and gloss reten-

tion. However, acrylics dry faster, and they can be buffed and repaired

in case of a problem in application (or if you happen to bump into the

dock and scratch the surface). Also, due to the speed with which they

dry, acrylics can only be sprayed. Polyester polyurethanes dry slower,

which means they can be brushed as well as sprayed. Polyesters also

have a harder, more scratch-resistant finish, but they generally can’t be

repaired or buffed like the acrylics. Finally, they require less mainte-

nance and have better chemical resistance.

APPLYING THE FINISH

The first thing you want to do before applying any paint is read the in-

structions carefully. If there is something you don’t understand, contact

the manufacturer and ask; paint companies would much rather help

you get a good result than try to determine how to fix a problem. Next,

figure out how much material and what supplies are needed. Determine

the area to be painted and divide by the coverage recommendation on

the label. You will have to figure in a loss factor, which is usually 10

percent for brushing or rolling and 25 to 30 percent for spray.

Try to make sure that the finish you buy is all from the same batch.

Batch numbers are usually printed on the lid of the can. If you must

purchase paint from different batches, open all the cans and mix them

together before starting. Painting professionals call this “boxing” the paint.

Some paint must be thinned prior to application, and some will need to be

thinned only when environmental conditions make it necessary. Be sure to

purchase the recommended thinner when you purchase the paint.

ROLLING AND TIPPING

The most common method for application is the “roll and tip” method.

This is where the paint is applied to the surface using a roller and then

“tipped off ” with a brush to spread the paint and to remove the roller

marks. This is best achieved by having two people working shoulder to

shoulder. One applies the paint by roller in vertical stripes from as wide

as the roller to about 1-foot wide. The goal is to keep a small wet edge on

PROJECT—PART II

BOAT

WORKS

SPRAY TECHNIQUE

Spray technique is not the easiest thing to mas-

ter, and the best way to improve your application

technique is to practice. I am not by any stretch of

the imagination a good spray applicator, but here

are some things I’ve learned that work for me.

1. As you squeeze the trigger of the spray gun the air starts
   pumping, and as you keep squeezing the paint will finally
   get to the tip. Getting used to the rhythm of when to start
   the air and when to start the paint takes some practice.


2. Use your wrist rather than your elbow as the pivot
   point when moving the gun. If you move the gun with your
   wrist locked the gun moves in an arc and more paint is
   applied in the middle of the arc than at the ends. Using
   your wrist as the pivot point will help keep the spray tip the
   same distance from the surface and you get a more even
   application of the paint.


3. Get a couple of 4-by-8-ft sheets of Masonite that are
   finished on one side to practice on. (You can find these at
   most major hardware stores.) They can be cut into 4-by-
   4-ft pieces, and they are inexpensive enough that you can
   throw them away when the job is completed. Set a couple
   of pieces next to the boat to make sure you get uniform
   conditions on the hull. When the paint is mixed properly
   spray it on the Masonite and watch the flow of the paint. If
   it stops too quickly you can add thinner, or if it runs or sags
   you may be applying the coating too heavily. In any case, it
   is better to work out the problems on the test panel rather
   than on the boat.


4. One good suggestion is to go online and search out
   some application videos (sites like YouTube can be a great
   source). Ask questions of applicators manufacturers and of
   the paint companies.

Acrylic finish paints

must be sprayed on and

are best left to the pros

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APRIL 2015 PHOTO BY BILLY BLACK