VECTOR, SAILBOAT, 15' X 5.5', 350 POUNDS
Every now and then I draw up a sailboat
with a centerboard. A boat with a centerboard can have
a prettier rig sometimes because the rig does not have
to be centered over the hull's widest beam, as it does
with a leeboard boat. But the sail area still has to be
right above the centerboard for the boat to balance well.
In Vector's case, the widest hull beam is 10' aft and
the centerboard is between 4' and 8' aft. And that is
the downside of the centerboard - it takes up some the
prime space inside the hull.
Some designs will skimp on the centerboard
size in order to take up less prime space but the result
of that will always be more leeway when sailing to windward.
In round numbers the area of the board that moves through
the water needs to be about 4% of the sail area to efficiently
counteract the full side force of the sail. Essentially
the centerboard "flies" through the water in
the same way that an airplane's wing flies through the
air. True, water is about 900 times as dense as air but
things conspire to keep the centerboard from getting 900
times as much force from a given area. First the centerboard
cannot develop a really high lift coefficient since it
must be symmetric in cross section in order to operate
on both tacks, unlike a soft sail which can be shaped
with camber to reach a Cl of 1.5 in a good sail and maybe
2.0 in a great sail. Worse yet is the fact that the centerboard
will flow through water at a fraction of the wind speed,
and if your boat is beating to windward at 3 knots in
a 15 knot wind, the 4% rule works out almost exactly.
That is the worst case - beating to windward especially
in rough water. If your boat were to hit a big wave and
slow down below 3 knots, or if the centerboard were undersized
to start with, the board will "stall" and develop
no more lift no matter how much angle of attack (leeway
to a sailor) you demand of it. The only solution would
be to "fall off" the wind, pick up more speed,
and try again just as an airplane pilot needs to recover
airspeed after a stall.
Vector was inspired by the 12' Skat.
It will be a much better family boat than Skat because
of its greater capacity. Two adults and two kids would
do it. There is a huge water tight storage volume behind
the cockpit. The transom is quite wide and will take a
small motor on a bracket mount, or you might try building
in a motor notch to one side.
She's V bottomed as you see. Should
be fast and handy, better than a flat bottomed boat although
she will be a bit tippier and draw a bit more water than
the flat bottomed boat.
There are two prototype Vectors that
I know of. The first was by Peter Mohylsky down on the
Gulf Coast (hope it is still there).
I never heard much of that boat but
the second by Mike Sandell showed up at the 2006 Rend
Lake Messabout much to my surprise (I had to ask what
it was) and I got to talk to Mike and see it sailing for
two days. Mike has a website
where the building is well covered. He was still quite
new to the boat but especially on the second day, after
he had tweaked the lines on his polytarp sail, he had
no trouble sailing and sometimes leading the fleet.
I asked Mike to write a bit about the
experience and he responded:
"My Vector was built over a period of five months
in 2005, beginning in March of that year. The wood used
was AC grade plywood purchased from the Menards home
improvement store, with framing purchased both at Menards
and Home Depot. The large pieces were cut to shape using
a table saw with the blade set to a shallow cut. Small
pieces were cut with a sabre saw.
"The glue used in the project was Titebond III,
produced by Franklin International. which is an ANSI/HPVA
Type I waterproof glue. Clamping of parts on the project
was accomplished using a combination of deck screws
and PVC clamps.
"Parts were cut in my basement workshop, and assembly
was done in the garage. Taping of the seams was accomplished
using marine epoxy and fiberglass tape purchased from
Chuck Lienweber at Duckworks Boatbuilders. Two layers
of tape were applied to both the inside and outside
of all seams. Filling was done using both epoxy filled
with wood flour, and also polyester auto body filler,
depending upon the application.
"The boat was finished using an oil-based alkyd
primer and oil-based industrial enamel, also purchased
at Menards. Brightwork was various types of moulding
pieces, held in place with stainless steel wood screws
and stained with a Minwax water-based light oak stain.
Final finishing of the brightwork was done using Johnson's
"Fittings were all purchased from Duckworks. Running
rigging is all braided nylon line from the home improvement
stores, except for the mainsheet, which is twisted polypropylene,
which is easier on the hands than nylon cord. The sail
was made using a kit from Polysail International, and
was completed in a single day, as advertised. The working
lines for the sail are both led to cam cleats on the
rear top end of the centerboard box. The mainsheet goes
through a traveller mounted on the rear deck, and from
there through turning blocks on the underside of the
boom and finally to a block on the back of the centerboard
box. The rig includes a boom vang, and the boom sets
on the mast about fifteen inches above the deck when
the sail is properly set.
"My boat includes four minor departures from the
plans. The first is centerboard box. The plans call
for cutting the bottom of the box to fit the curve of
the hull bottom, setting the box on top of the hull,
and then glassing it in place. I didn't see any way
that I would successfully cut the box to precisely match
that curve, so instead I cut the bottom slot wide enough
to fit the centerboard box through it. I then glassed
it in place from the inside, carved and sanded the protruding
end of the centerboard box to match the outside curve
of the hull, and then glassed the outside edges to finish
"The second change was in the seats. I'm a fairly
big guy, and found that changing sides during a tack
or jibe was difficult due in part to the limited foot
space between the seats. The original seats were fourteen
inches wide, and I replaced these with twelve-inch wide
seats. The extra four inches made a huge difference
"The third change was in the jaws for the boom.
On a windy day last summer (before I had installed the
boom vang) I broke the jaws while running downwind.
Rather than build a new, long set of jaws, I cut off
the broken set short, and then just used a longer cord
to wrap around the boom. The cord is waxed to help ease
movement, and does not carry any parrell beads. This
has worked fine for me since then.
"Lastly, I did not construct my gaff and boom
from laminated lumber as specified in the plans. Both
are banister rail pieces purchased at Home Depot. The
piece used for the gaff felt stiff and heavy, and was
used as-is. The piece for the boom felt less robust
to me, and got another piece of wood laminated to the
flat surface on the bottom. I think I cut that one a
bit too low, however, and it still worried me a bit.
I plan on making a new boom this winter, which will
have a deeper piece glued to the bottom of the railing
to produce a "keyhole" shaped boom, similar
to the T-booms seen on other small wooden boats.
"My Vector was named "Valkyrie", in
homage to my Swedish ancestry on my father's side. Because
of the gaff rig, it takes a bit more tweaking of the
sail to get things just right than on simpler rigs.
But once set, she really screams. "Valkyrie"
accelerates very quickly on reach, and will point nearly
as high as a sloop rig. But if the sail is not set properly,
she'll flutter and stall in a heartbeat. Really keeps
me on my toes! The only additional change I feel the
boat needs is a longer tiller for single-handed sailing.
Other than that, she is a joy to sail, and was worth
every last minute put into her creation.
Taped seam construction. She needs four
sheets of 1/2" plywood and six sheets of 1/4"