Page 24 - WestlawnMasthead19_Sept11.pub

This is a SEO version of WestlawnMasthead19_Sept11.pub. Click here to view full version

« Previous Page Table of Contents Next Page »
One of the most common errors I encounter is in laying out
and painting bootstripes (also called boottops)—the paint
line separating the topsides from the anti-fouling bottom
paint. I've even read through quite a few articles that care-
fully explained how do it—all wrong! The thing to keep in
mind, before painting a bootstripe, is that your
Grackle
Crackle—
along with every other boat in harbor—never floats
at the same line or at the same level two days in a row.
If she's a typical 30 to 45 footer, the additional load of pas-
sengers, fuel, water, gear, food and stores could easily come
to a ton or two, for a long cruise. This would sink
Grackle
Crackle
a good 2 inches, or so, in the water. Naturally, at the
end of the cruise
Grackle
will be floating 2 inches higher
again, and in between, well, she'll be in between. Even more
important is that all this stuff isn't exactly going to be scien-
tifically distributed. (I've always had special difficulty keep-
ing my crew scientifically distributed, but—as skipper—I have
to take full responsibility, of course.) The result is that
Grackle
will seldom float level. Sometimes she'll be down by
the bow, sometimes by the stern. This is all normal, and un-
avoidable. (The nice waterline drawn on the architect’s plans
is really just a reference line. In fact, that's why it's usually
labeled the "DWL," which stands for datum waterline or de-
sign waterline.)
The trick to painting a good bootstripe is not to make it
straight as a rule and parallel to the imaginary waterline—as
some articles indicate—but to make it curve up at each end,
just as the sheer curves up on most boats, as in the drawing
above. Like the sheer, it should be higher at the bow than at
the stern. Not only does this compensate for
Crackle
's incon-
siderate tendency to float at different attitudes, but it will
improve her looks as well. In fact, a boat with a straight
bootstripe has a dull lifeless appearance, whereas her exact
twin with a sheered bootstripe will have flair.
I usually take the profile drawing of my designs, draw on
full loaded displacement waterline and sketch in the desi
curve and thickness by eye. On a 30 to 40 footer, I allow
about 3 to 4 inches from the bottom of the bootstripe to
loaded waterline—a bit more doesn't hurt—and have the l
est point of the curve about 70 percent of the waterline
length aft of the bow at the waterline. Doing this by eye
takes some practice and a bit of trial and error. A reliable
rule of thumb for defining the bootstripe exactly is as fol-
lows:
Take a profile drawing of your
Crackle Grackle
and draw
three vertical lines up from her design waterline. The first
vertical should be right at the intersection of the waterlin
with the bow (called, "station 0"), and the aftermost verti
should be right at the intersection of the of the waterline
with the stern (station 10). The third or middle vertical
should be at 70 percent of the length of the waterline aft
the bow. (This location is known to designers as "station
Station 7 is the lowest point of the bootstripe curve, and
narrowest point of the bootstripe itself.
The heights of the bottom of the bootstripe above the D
at each of these three locations are found by dividing the
waterline length, in inches, by the following numbers:
This gives you the height above the waterline at each loc
tion in inches. If
Crackle Grackle
were a 35-foot waterlin
boat then, the bottom of her bootstripe would be 3.5 inc
above the waterline at station 10; 2.97 inches above at s
tion 7; and 4.55 inches up at station 0. To paint this line
mark these points on her hull and connect them in a sm
fair even curve. Of course, since
By Dave Gerr, © Dave Gerr, 2011
75-Ft.
Windglimmer
by Dave Gerr
HEIGHT OF BOTTOM OF BOOTSTRIPE ABOVE DWL
Stern
Station 7
Bow
120.0
141.4
92.3
Continued page