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The most difficult ship to design was the Revolutionary War man-of-war. The
designers had to combine opposing features within the limitations
of the day, confronting one contradiction with another.  Make
it wider, make it narrower; make it lighter, make it heavier;
erase your lines, crumble the paper up and start again.
The ships built in that century had to be armed, and they had
to carry goods and men. In THE HISTORY OF AMERICAN SAILING SHIPS,
Howard Chapelle describes their design as, 'The full round bow,
high freeboard and massive bulwarks, heavy displacement and rather
cumbersome appearance.'
Yet these ships were loved by their crews and captains, and performed
the duties that enabled the United States to get started as a
country of free men. This caused me to think, there must be great
virtues of these ships we can use today or at least appreciate.
Chapelle describes two problems he sees even in today's shipyards:
yachts lose their longitudinal shape, their ends sag - or hog
in the 17th century parlance - and speed must be pitted against
size and weight. Chapelle says the designers of these vessels
dealt with hogging and longitudinal shape by using heavy stiff
decks with full ends at the bow and stern. The problem of pitting
speed against size and weight wasn't really solved until another
century.
This is the Washington, a galley ship of 72 feet by
19 feet 7 inches beam. It was built on Lake Champlain in the summer
of 1776, for General Benedict Arnold against the British fleet.
Chapelle says men and tools were hard to come by that year. So
the Washington was a superior compromise of size, weight,
hull design and lateen sails.
The Washington was built at Whitehall, NY, in 1776.
Probably, more than one shipwright had significant input. Without
material, skilled workmen, ironwork, sails or rigging specialists,
someone had to pit the need for a wide bow and stern to support
guns against the need for speed.
With guns and sails, large crews were needed. But if you increase
the volume, you slow down the ship. If you make the ship longer
to make a finer hull for speed, the hull hogs and creaks with
leaks. If you added elbows and knees below for strength, it reduces
the capacity to carry men and arms. It also adds weight, which
makes sailing more difficult. The weight of crews, cannons, cannonballs,
sails, stores, water, wood, gear like blocks and tackle were enormous,
so if you fill out the ends you're back to a slow blunt boat that
leaks.
In the drawing you can see the blunt bow, the high bulwark astern,
and the long deep keel. What we can learn from the bow is the
ability to keep the ship standing on its waterline. This is not
a ship which will bury its nose in a following wind or sea, something
we should keep in mind during a downwind blow. The second obvious
attribute of this galley is the long keel, ending in a fairly
narrow rudder. The Washington had no board, only its
long keel at the bottom of a rounded hull. The hull had plenty
of wetted surface in the water, but still you see the role the
last ten feet of keel play in steering. The keel also takes some
pressure off the rudder. The third attribute of this hull is the
curvature at the turn of the bilge. What this means is that when
Washington heels, it hits that curved bilge long before
the water reaches the deck. If you've ever seen a lines drawing
of Slocum's Spray you'll see the same thing.
Now let's do as the preachers do, make some applications.
In the old ships the bow has the job of slapping waves away from
the deck and guns as well as keeping the bow on top of the sea.
The bow had to have some volume to carry sails before the foremast
and to carry the weight of guns. Too much bow, not enough speed;
too little bow not enough support for the ship. A bow too slender
would not give the hull enough strength to keep it's shape, causing
the keel or garboard to warp out of alignment. This created leaks
which couldn't be repaired at sea.
On small craft, the traditional pram bow keeps some volume forward
so you can step to the bow without swimming. It can keep the bow
dry, but as we all know it slows down the boat, especially against
waves. So what can we do?
One solution is to narrow the pram bow, but not completely. On
an 8 footer, narrowing the bow to one foot would be a nice compromise.
You'd still have enough solid wood to use as an anchor for attaching
the topsides, you'd still have some volume forward, yet an external
keel can be fastened to a one-foot bow to divide the waves, decently
well. Although I didn't show it here, the sides of the bow can
be flared, as they often are. Solid wood has its' advantages.
You can drill a hole for a painter. You can drag the boat up onto
the beach without compromising the bow structure, you can even
tip the boat on its' bow to carry it from the beach to your car
or truck. A nice attribute of this bow is leaning the bow forward
produces flare in the sides, as you can see. More lean forward,
more flare outward. Keep in mind, the more you lean the bow forward
the more it will sink down into waves.
Most of us will want some volume forward. Tipping over becomes
a nuisance after a while. It's better to be able to move around
in the boat, knowing you won't be rubbing whiskers with the catfish
every time you turn your head.
Another compromise between volume and speed is a traditional
v-bow at 45 degrees. If you use one section of plywood, the sides
will need to be bent slightly to take the turn at the first frame.
This looks good, and with enough glue and an interior keel piece
of 2x2", it can be made strong. I'd lean this bow forward
around 50 degrees to ease the flow of water. Bring the topsides
all the way up to the point of your 2x2" and you've got a
strong bow.
A third option is one I saw years ago in Popular Mechanics. It
is a laminated design by Willard Jackson, the world's most ubiquitous
designer. He had a design for every occasion. Too bad he never
worked for Hallmark. This bow was for a glass-bottomed boat. I
grew up in Tampa, so I knew of the glass-bottomed boats in Sulphur
Springs, FL, where you can see the fish through the glass bottom.
I never cared for watching fish but I did consider throwing my
brother overboard to watch him sink.
On the right are the original plans. On the left I show you how
the two pieces of 1/8" plywood are cut to form the bow. The
chines are made from solid wood, requiring some steam bending.
The long keels with nearly all the lateral plane at the rudder
shows us how much the rudder steers the ship, even into the wind.
These ships didn't point very high, so they had no particular
depth of keel beneath the sails' center of effort. Their design
was meant to create a smooth flow of water after the bow all the
way aft to the rudder, more like a canoe than a modern yacht.
What might be interesting is that good steering didn't depend
on the depth or length of keel, or even the rudder. Steering was
based on balancing the ends of the hull and the placement of masts
and sails. Chapelle says, 'If a vessel steered badly when new,
it was usually possible to improve her by alterations in the positions
of the masts or in the lengths of the spars and recutting sails.'
This gives you an idea of how important the waterlines were in
creating lateral resistance to help the rudder out.
For small craft, the waterlines are just not long enough to
create steering. However, the rudder can be made larger, deeper,
or smaller without any trouble. Still a good designer will take
some care about his mast placement, the size of the sails, and
the center of effort to make steering easier. Two designers I've
had great conversations with concerning the care of details in
small boats have been Warren Jordan and Arch Davis. Warren's designs
are natural to the eye, they go together smoothly. Arch's plans
are expensive but he takes the care with every detail which produces
beauties.
The usual rule of lateral plane to sail area is 4%. However,
this doesn't work out in practice for small craft. A keel 6 inches
below the waterline, no matter how long, just won't get most small
boats to windward. Normally, rudders on 8-12 footers reach 2 1/2
to 3 1/2 feet below the waterline. So if you have a boat like
Teal, a keel 2/3 the length of the waterline, ending with 2 feet
of depth at the rudder is a good compromise between wetted surface
and grip.
The single biggest headache for the designer of Washington,
was hull strength and stiffness. The Washington carried
19 guns, for the action against the British in 1776. These were
2 18-pound guns, 2 12-pounders, 2 nine-pounders, 4 four-pounders,
1 2-pound gun, and 8 swivel guns of small size. The weight of
these guns meant the bow and stern had to be fully shaped, without
sacrificing too much speed. It needed to be shallow-draft, but
not necessarily weatherly since the oars would be used on a windward
tack. If the designer adds weight to stiffen the hull, he slows
down the full-bowed hull. To overcome the slow hull speed, more
sail had to be added, but that meant greater volume to support
the sail area. And that meant a wider slower ship. The problem
could not be solved until metal strapping 100 years later.
For small craft, stiffness has different implications. A stiff
hull will keep its paint job better than a creaky one. It will
not strain an epoxy glue exterior as much. The plywood will last
longer and the hull will perform smoothly.
This is the little beauty, Apple Pie, by Merrins Watercraft.
You can see four corner knees, a seat, a thwart, a rudder and
rub rails. All of these stiffen the hull without adding much weight
or being in the way. Apple Pie will perform.
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Applie Pie
Click HERE
for complete plans of Apple Pie (PDF) |
Personally, I'd put the bow and stern corner knees a foot above
the bottom panel. It lowers the weight just a bit and gives me
a shelf upon which to put things-what things I don't know, just
things. In small craft support near the bottom chine have the
greatest effect on the stiffness of the boat. Notice the two supports
for the seat, one vertical and one horizontal.
If you wanted to build Apple Pie as a sailing boat with
a keel, I'd make the keel extend from just below the seat support
to the bottom of your rudder. A slightly concave curve to the
bottom of the keel, parallel to the bottom rocker, might look
cool. Keep in mind the keel needs to be attached to the boat so
it doesn't affect the beautiful curving rocker, while still being
secure. An interior piece would do the job, say, a 3 inch wide
strip of 3/8" plywood glued inside the bottom through which
the keel is glued or screwed.
Then I'd use 2 plywood sheets-3/8" each-laminated for the
keel. To secure the outside of the hull I'd use 7/8"x 1 3/8"
chine logs curved around the bottom's rocker on either side of
the keel. I did this on the first Elegant Punt I ever built years
ago, and it works. In fact, I could have shaved some of the keel's
depth off without any loss of performance. This was probably due
to the sharp chine at 12 degrees of flare. It acts as a soft barrier,
especially with the external chines Bolger used. Less flare, better
sailing.
The Bolger Brick has this long shallow keel with plenty of ballast.
With its sharp chine it sails to windward remarkably well.
Now let's take these lessons from Washington, and apply
them to a small craft. Texas has many rivers deep enough for camp
cruising, one of them fairly close to where I live. So I thought
about the lessons from Washington for a camp cruiser
which could navigate small rivers and a lake.
First, a camp cruiser can't be too wide. When the river is too
shallow for sailing, I'll need to be able to paddle it. I've made
it 3'6" wide, knowing I can paddle with an 8 foot double
paddle. I'll need 12 feet to give me 6 1/2 feet in which to sleep
while still having plenty of space for personal and sailing gear.
I'll use the full ends of Washington to put the center
of buoyancy near the center of lateral resistance while still
having closely parallel topsides. I'll also use the shallow draft
with a box-like hull structure for the most capacity and volume.
I'm going to use three bulkheads. The bulkhead at the stern will
be the compartment wall for buoyancy and a dry compartment for
any gear which needs to be kept out of rain. It will also as secure
the mizzen mast. The forward bulkhead is the forward buoyancy
compartment. Both compartments at the ends will have a hinged
top. The middle bulkhead will secure the mainmast. I'll also sheet
the jib to the bulkhead a foot below the coaming so I don't slice
my arm or hand on it.
I'll use the seats when I'm sailing and the thwart near the mainmast
when I'm paddling or rowing. The seats will have a vertical wall
to form a compartment and give me some protection when I sleep
between the seats. I'd have a tarp to go over me, from seat to
seat.
A river boat just about has to have leeboards. I'd put pivoting
leeboards in a case, inside the seat compartments. This gets them
out of the way, but there's another reason for putting them there.
I can use them as props when I beach this boat at night. The rudder
will have to be a kick-up rudder. I'll carry a spare rudder and
leeboard.
The sail rig is a cat-ketch with an optional jib. The cat-ketch
has superior air flow lines, while the optional jib is for windy
conditions when I'll lower the main and sail on mizzen and jib
alone. The mizzen boom will extend beyond the stern to give me
some protection from wind, waves, and extreme heat in the summer.
Shade over a cockpit in summer is good. I'll make the mainsail
a sprit rig with loose-footed boom to save my cranium from destruction.
The mizzen will be a simple tall marconi, to keep the tackle and
sheet layout simple at the stern.
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Paul
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