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the basics of sailing
sails, hull and rudder
Let's get basic. This is the first of a few short
features on sailing for beginners. All terms will be defined assuming you
are a complete newcomer to the sport.
Fabric sails attached to a mast intercept the
wind and carry the boat along. "Squareriggers" and Viking longboats tend
to have square sails. Most modern boats are rigged with sails that are
closer in shape to triangles because they are easier to handle and more
efficient. These are called fore and aft rigs because at rest the
sails lay along a line that could be drawn from the forward
(pointy) end of the boat to the aft (blunt) end of the boat.
These boats usually have a rigid pole, called a boom
on the bottom of the sail. Sometimes they have another pole, called a
gaff across the top of the sail. Most boats carry more than one sail
and the other sail is likely to be a triangular jib that has
neither a boom nor a gaff. We'll get into some other rigs in another
article.
The sail pivots off the mast which allows the boat to
catch wind at a variety of different angles. This makes it possible for
the boat to sail against the direction of the wind.
The hull is a rigid, streamlined shape that must cover
enough surface area to support the weight of the boat itself, plus the
contents. It floats because it weighs less than the water it displaces.
Within certain practical limitations, the longer it is, the greater its
potential speed. The hull includes a component that extends down into the
water to keep the boat from being blown sideways. This component could be
a keel, or in smaller boats a daggerboard, or a
centreboard. These components also help the hull track in a straight
line as the boat sails.
Wind, currents and swell all effect the boat's
movement, but let's ignore them for a moment and look at the simple
mechanics of steering. The hull cuts through the water as it moves. If the
rudder is held straight, the water passes by with little effect. But if
the rudder is turned, the boat pivots on a point forward of the centre
point of the hull and takes off in its new direction. This is useful to
remember that when you sail close to some object harder than your boat,
that unlike a car, both the bow and stern are turning,
rather than one just following the other.
If you are using a tiller, you move it away from
the direction you want to turn; if you're using a wheel, the hidden gears
have been designed to turn the rudder in the proper direction and you can
steer very much the way you steer a car.
The
Mechanics of Sails
A sail is a pretty obvious propulsion device to
anyone who has ever staggered down a street against a stiff
breeze. Wind blows, the fabric fills, the boat slides downwind.
And that's just what happens with a sloop or ketch running free.
Pointing the boat directly downwind, and
swinging the boom out at a 90° angle to the centreline of the boat
allows the sail to block the wind and propels the boat in the same
direction as the wind blows. It works very well, but limits your
choice of destinations and unless the wind changes makes it
impossible to sail home again.
No problem. You're sailing a fore and aft
rigged boat and they can sail upwind by turning their simple sails
into airfoils that pull your boat upwind. Complicated? Not
terribly and if you want, you can ignore the whole airfoil
business and pretend the sails push your boat at every point of
sail.
Either way, here are the practical details you
need to know:
If you want to sail in a direction 90° from the
wind, you would haul the sail in until it's at about a 45° angle
to the centreline and point the bow perpendicular to the wind.
That's known as sailing off the wind or reaching.
If you want to pretend that wind just pushes
the boat, skip the rest of this paragraph, though I don't think
you'll find it too hard to understand. You've heard how the wings
of an airplane work a time or two, haven't you? Wind flows under
the flat bottom of the wing and over the curved top of a wing at
different rates of speed which creates lift, allowing the plane to
rise off the ground. Take a look at the overhead view of the sail.
It's shaped a lot like the side view of a wing. The wind flowing
along the forward, curved edge of the sail must get to the
trailing edge of the sail at the same time as the wind moving
along the shorter, boom-side of the sail, so it must travel
faster. This creates a low pressure area on the forward
surface of the sail which pulls the boat toward it. The rudder and
keel or centreboard compensates for this sideways pull and allows
the boat to glide forward at nearly 90° to the wind.
A third point of sail, close hauled or
on the wind, makes it possible to actually sail upwind.
Once more, the sail acts as an airfoil, drawing the boat forward
as the centreboard compensates for some of the sideways motion.
All of these points of sail can be
steered on either a starboard (the wind is coming over the
right railing of the boat as you look forward) or a port
(the wind's coming over the left railing) tack. By shifting
back and forth between these two tacks and the different points of
sail, you can plot a zigzag course to just about any place you
want to go.
Tacking
You probably know
that you can sail a boat in various directions, including
upwind, by shifting the relative position of the sail and
rudder. You can get where you want to go, but almost never in a
straight line, which is one of the most pleasurable features of
sailing. You need to tack-- zigzagging back and forth across your
desired course-line and shifting the sail and boom from one side
of the boat to the other.
There are two ways to change tack, coming
about-- generally the preferred method-- gybing.
To come about, you steer the boat through
the eye of the wind, that is, into and across the flow of the
wind. The sail empties of wind on one side, and the boom swings
gently across the boat and fills on the other side.
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#1- Bottom Figure- Old Course
You're traveling upwind on a starboard tack. You call out "Ready about,"
and turn your helm into the wind.
#2- Middle Figure- Crossing the wind
You're crossing the eye of the wind and if you loose power you'll be
stalled out, in irons. But that doesn't happen and your sail again
fills with wind from the other side of the boat.
#3- Top Figure- New Course
You are now on a port tack and everyone has shifted their position across
the boat to improve the balance.
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Gybing is a more difficult operation and must
be approached with caution, particularly in heavy winds. To gybe,
you turn away from the wind, allowing it to hit your sails from
the stern and slap the boom across the boat with all the force the
wind can offer. This extreme shift can throw the boat over on its
side and in heavy seas can cause the boat to broach--veer
dangerously on her side-- or capsize. Not good.
So why would you ever jibe instead of coming
about? Well, there are a few times when a controlled gybe
is the more practical move. When you gybe, you only turn the boat
90°, while coming about means you swing around 270°. The action of
turning into the wind to come about drops the boats speed, and if
you don't have enough speed going into the tack you may end up
in irons-- nose into the wind, sails flapping uselessly. So,
instead of coming about, you sheet in your sails so that the boom
is as close to the centreline as you can get it, and still sail,
then you holler, "Prepare to gybe!" to your eager and
obedient crew, all of whom duck, and then you turn away from the
wind. The boom sweeps over you, the crew throw themselves from
their position on one side of the boat to the other and you slide
across your seat as well, all secure about the deck.
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#1- Bottom Figure- Old Course
You're travelling downwind on a port tack. You call out "Prepare to jibe,"
and turn your helm away from the wind. Depending on the size of
your boat, you may have a crewmember release a preventer and sheet in the
boom so you're running close-hauled.
#2- Middle Figure- Crossing the wind
The wind catches the outboard side of the sail and pushes it across the
boat. You, or the crewmember minding the main sheet, takes up the slack as
the boom moves across the boat and lets the slack out as it swings to the
opposite side of the boat.
#3- Top Figure- New Course
You are now on a starboard tack and once more on a broad reach.
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What you most seriously want to avoid is an
uncontrolled gybe. Picture this: You're running free, wind at your
back, sun beating down in glorious fashion, when your attention is
caught by a three-headed duck cruising past. You're not minding
your helm and you fall off the wind just a couple of points.
Whap! Boom smacks you in the head, and
it's all over in an instant.
If only you had rigged a preventer. Just
a simple line tied to the boom and tied on someplace forward to
prevent an accidental jibe. With your preventer in place, you'd
sing out, "Release the preventer and prepare to jibe," your eager
crew would make it so, and you'd follow the duck for an impromptu
photo op.
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