Paint and Varnish Tips
©1998 Daniel Boren
Of all the things I've learned about from the car guys, the longboard is my favorite. A longboard is a stiff but flexible sanding board that is 3" wide and 16" long. It has clips on each end to hold sandpaper, handles on each end that look a bit like the handles on a jointer plane, and a thin piece of padding on the bottom. It is stiff enough to bridge the low spots in your hull but flexible enough to conform to the curves of you hull. If you rub it on your boat long enough, you can get a beatifully fair surface.
When you use the longboard, it is best to move it at a small angle relative to its length instead of just sawing it back and forth in a straight line. If you are using a longboard on wood prior to varnishing, be hold the longboard at a 20 or 30 angle as you move it in the direction of the wood grain.
If you are sanding primer, it is often helpful to move the longboard in one direction only so that all of the scratch marks from the abrasive run in the same direction. Then, when you move to the next finer grit of paper, choose a different direction. Even in poor light, the difference in the direction of the scratch marks will be a big help when you're trying to determine when you've gotten out all the marks from the last grit.
Watching an experienced friend sand primer with a longboard was instructive. He
took maybe three or four long, deliberate strokes with the longboard, and then stopped
to knock the dust off before the paper was clogged. He said that when working in his
own garage, he keeps a piece of welding rod handy. A couple of good whacks with it and
all those little balls of galled up paint and primer come off. I had good results using
a plain wooden stick instead.
An autobody trick for getting a fair surface
When sanding any surface that is to be painted (bare wood, fiberglass or primer), it
is far easier to see small, sharply defined surface defects that it is to see broad
low spots and unfair surfaces. An autobody trick that I've learned is to use a
guidecoat. Get youself a can of spray paint (I used enamel, although laquer was
recommended) in a color that is slightly different from the color of your primer.
If your primer is white, a light gray would work well. It should be visible on the
surface of the substrate, but be easily covered by your next coat of either primer
or paint. Hold the can much further away from the surface than you would if you
were trying to paint it, and put on the lightest possible dusting of the spray paint.
The idea is that you just want a lightly speckled bit of color on the surface you're
working on. Now, go after the surface with your long board. Low spots should jump
right out at you, allowing you to take whatever corrective measures you need to.
Tired of sanding your fingerprints off?
Although I try to block sand as much as I can, there are many places where you
have to simply fold up a piece of sandpaper and do it by hand. This can lead
to some raw finger tips at the end of the day. A friend of mine who worked for
a time as a piano refinisher suggested that I get those rubber finger tip covers
from an office supply store.
My favorite primer
When I first painted the outside of my hull, I thought I had done a reasonably
thorough job of sanding and filling. Six months later, when re-examining the
surface in a glancing light, I was horrified to be able to see all sorts of
screw heads, print through from the underlying fiberglass cloth, etc. I couldn't
believe I had done that poor of a job of prep work and never noticed it.
One problem with conventional, solvent based primers is that they continue to shrink up over a period of several months. This makes your paint job look quite a bit worse 6 months after you've painted it.
One product I learned about that I really like is System 3's epoxy primer. It is a two part epoxy that you can thin down with a 50/50 mixture of water and isopropyl alcohol. Since it is primarily an epoxy, the shrinkage is much, much less than you'd get with conventional primers. I also found it to be nicer to sand. It is a bit harder than other primers, but when cured (usually in a day) it sanded to a fine, dry powder.
It would probably work best if it were sprayed on, but I just thinned it a bit (maybe 5% or 10% in 75F Seattle weather) and rolled it on. I used it inside my cockpit and on the top of my cabin, and there is a real difference in the quality of the finish between these areas and my hull. I wish I'd discovered it sooner.
The primer is intended to be used under System 3's water-based LPU paint, but I and
several of my friends have used it underneath both old-fashioned marine enamel and
Interlux's single part polyurethane. We have had no problems in two years and the
adhesion of the paint to the primer appears to be excellent.
When have you sanded enough?
You can drive yourself nuts trying to decide when you're finally "done"
sanding and filling and ready to paint. Here's some bad news: you'll never be done.
A friend, whose car restorations I admire greatly, told me that he has never in his
life painted a car that he thought was ready to paint. You just reach a point where
you've messed around with it all you can, and then you paint it.
Especially for us amateurs, give yourself permission to do less than a perfect
job. You should either decide how much time you can budget for the task, or decide
that you will be happy with a "6 foot" paint job (one that looks really
good from at least 6 feet away). Do the best job you can, but don't lose sleep over
it.
A few primer mistakes I've made
For whatever reason, I seemed to have a lot of trouble when I first started using
primer. I had particular problems learning to use solvent based primer, though
I soon got the hang of it. Here are a few of the mistakes I've made, and what I learned
from them.
Let it dry completely before sanding it. I applied the first coat of primer on a Friday evening, with the idea that I would show up Saturday morning and spend the day sanding it down. When I set to work Saturday morning, the surface felt quite dry to the touch, yet the sandpaper seemed to clog hopelessly in a very short period of time. In retrospect, the problem seems obvious, but at the time I didn't quite know what to think. One of my car friends came over, took half a dozen stokes with the longboard, and told me to let the primer dry some more. By the next day, the primer sanded off in a fine, dry dust-- just like I expected.
Be carefull when following the directions (sic!). I used
Interlux's Brightsides primer. I dutifully read and tried to follow the directions on the
back, which recommended wiping the surface down with cheese cloth dampened with
their 333 brushing liquid. Imagine my horror when the solvent attacked and lifted
the primer anywhere it was very thin, essentially ruining my prep work! I called
Interlux's technical assistance phone number, and the guy seemed to be as puzzled as
I by this problem. He was concerned that I might have too much solvent on the
cheese cloth, and told be to be sure that it was just very lighly dampened. I tried
again, but was never able to make it work. Maybe I was doing something wrong-- but
now I use isopropyl alcohol for a wipe down.
A trick to get a good surface for brightwork
The standard drill for examining a sanded wood surface prior to varnishing is to
wipe down the surface with mineral spirits and then to examine the surface in
glancing light. This worked pretty well for me, but I got tired of continually
messing with thinner, and the results I had with guide coats
gave me this idea: when I get the wood surface close to where it should be
for the first coat of varnish, I apply a sacrificial first coat of highly thinned
varnish. This serves as a sort of guide coats, and it lets me see right away where
more attention is needed. Most of it gets sanded off, and I just try to make sure
that any remaining varnish has plenty of tooth for the next coat. Apply your first,
highly thinned sealing coat of varnish just like you normally would.
Painting on your own name
I hate the look of vinyl letters, especially on a wooden boat. I painted mine on
myself, in spite of my laughable artisitic skills. I started by laying out the name
on a computer using WordArt in Microsoft Word. I expanded the name as large as possible,
trying to get the aspect ratio just the way I wanted it, and then printed it on a laser
printer. On the printout, I drew a horizontal line below the letters and another one
above . Next, I took it to a xerox machine that could enlarge the image, and made
successive copies until I had the letters the desired size. By that time, there was
only one full letter on each sheet of paper. Using the horizontal lines and overlapping
letters as a reference, I taped the whole mess together. I did the name and the home
port seperately.
Once that was done, I went to an art supply store and bought a roll of clear plastic film that had a low-tack adhesive on one side, which was covered with a peel away paper backing. The backing also had a grid drawn on it. Using the full sized template I'd taped together, I traced the letters onto the plastic and then cut out a full-sized stencil with an x-acto knife. Again, I did the name and home port seperately on seperate pieces of plastic.
I gave the transom a light sanding with #400 wet-dry sandpaper, and used masking tape to make horizontal reference lines for both the name and home port. I peeled the back off the stencil and stuck it to the transom. This took some time, but it was fairly easy to peel and re-stick the plastic, the only difficulty being trying not to stretch the stencil in isolated areas. Next, I masked the rest of the transom off and then spray painted the name with plain, white Testors brand model airplane enamel. I repeated this for the home port, using black paint.
When the stencils are peeled off, there will be isolated areas where small amounts of paint have crept under the edges of the plastic. I cleaned these up by scraping lightly with an x-acto knife. If you really want to finish the letters, get yourself a lining brush and add some drop shadows to the letters. I had an artist friend do it-- his hand is steadier than mine! He thinned a bit of the blue paint that I used for the cabin top, and added the shadows by hand.
Finally, add a couple of coats of varnish. Don't sand the letters before doing this or
you'll grind fine white sanding dust into the rest of the transom. The rest of the transom
will still be scuffed up from the prep you did before adding the letters. Brush on a
coat of varnish, let it dry, scuff it up lightly and then add a second coat.
What kind of paint, varnish, etc. did I use?
Almost everybody knows that the brand of paint or varnish you use has a lot less to
do with the quality of a finish than the amount of sandpaper you use. Still, people
are curious to know what has been used and what sort of problems were encountered,
so I'll name names. I don't work for any of these companies, so if I recommend
anything it is only from the standpoint of a happy (or not) customer.
To be honest, I've switched to plain old mineral spirits out of the harware store. It works better, and I can get a gallon for less money than I'd spend on a quart of 333.
One other thing worth mentioning is that Clipper is a very clear varnish. If you want the golden color that traditional varnish adds to the wood, this might be a poor choice for you. However, the wood on my boat is already fairly dark, and I prefer the clear finish on my wood.
This paint is tough as nails. For two years, I climbed in and out of my cockpit while the boat was on the hard on a dirt surface. This stuff stood up to muddy shoes, dust, dropped tools, etc. For a deck or cockpit, I think it would be tough to beat this stuff.