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sink-me
Getting the Most from Your Boat
By Thomas P. Lake
Important shortcuts that good sailors use automatically and the novice should
master. Tells all about location of pivoting point, fullness of sails, trimming,
and how the helm is a clue to sail balance
There are many shortcuts in getting the most from your boat, whether it is a
10-ft. dinghy, a 40-ft. racing sloop or a 50-ft. heavy cruising type. First in importance
is the fullness of a sail, for if it is either as flat as a board or as full as
a sack of flour, best results in sailing cannot be obtained. A sail gains power
by causing the air to flow past it in smooth lines; air on the leeward side (side
away from the wind) travels a greater distance than that on the weather side (side
toward the wind), as illustrated in Fig. 1. The leeward air is "stretched out" when
it passes along the sail, and is at a lower-than-atmospheric pressure. The sail,
in trying to move into this low-pressure area, transmits its pull to the boat. The
air on the weather side is slightly compressed and adds its small effort to the
total effect. The weather side supplies about twenty percent of the total, while
the leeward side supplies about eighty percent.
Although the fullness of a sail is cut and sewed into it by a sailmaker, the
sail must be set properly if it is to take its correct shape. This is especially
true of a gaff-headed sail (sail with the gaff or spar at the head or top portion
of sail). The shadow of the mast on a sail provides a good clue to how well a sail
is hoisted. Fig. 2 shows a small cruising yawl with poorly hoisted gaff-headed sails.
The bro-ken curves indicate hard spots (taut areas), which break the smooth flow
of air across the sail, both windward and leeward as well. Such hard spots tend
to cause little eddy currents that prevent the proper air flow over the sail and
reduce its power. The smooth curves shown in Fig. 3 are the sign of well hoisted
sails. Jibs (triangular sail forward of the foremast) and marconi mainsails (without
a gaff) must be set properly also, and the shadows will help in determining this.
Avoid hoisting a sail or stretching its foot (lower edge) any more than just enough
to make it set smoothly, free from wrinkles.
Fig. 5 gives the correct terms for the points of sailing, A close-hauled boat
is sailing as close to the wind as is possible with advantage. When she is not as
close to the wind as possible, even though only a few degrees from it, she is said
to be close-reaching. When the wind frees (moves aft as seen from the boat), the
reach changes from close to broad, and when the wind comes over the quarter (45
degrees from astern), or from astern (over the stern), the boat is said to be running
(going with the wind).
While there is wide difference of opinion concerning the fullness of sails, most
American sailors seem to prefer a curve in a horizontal direction, with a depth
of about 1 ft. in 15 ft., as indicated in Fig. 6. This curve is the camber of the
sail. The fullness of a mainsail can be measured as shown in Fig. 7. If a mainsail
is too flat, it can be given more camber by easing the outhaul (line to haul the
corners of a sail to the end of a boom or gaff) and distributing slack of a few
inches throughout the length of the foot. This is especially valuable when broad-reaching
or running, and the results are well worth the trouble if such a course is to be
held for even a short time. A flat mainsail is good for heavy weather because it
is not efficient; there is then a surplus of wind and high efficiency is not desired.
A flat sail may require less luffing (slight shaking while spilling wind out of
sail) to enable the boat to stand up to the wind. A gaff-headed mainsail requires
different trimming than a marconi mainsail as explained in Fig. 9. The angles given
are for apparent wind (the angle made by the wind over the moving boat); not for
the true wind.
The draft (air flow) of a jib can be altered by shifting the jib-sheet lead in
combination with trimming the sheet. The effect of moving the lead is shown in Fig.
8. When close-hauled as in Fig. 4, the lead should be in its forward position in
order to distribute more strain to the upper portions of the jib and to make it
set somewhat flatter. When reaching, however, the mainsail twists much more than
it does when sailing close-hauled, and the jib must be allowed to twist to match
it. If the lead is not changed, the jib backwinds the mainsail (blows against its
leeward side) unless the jib is eased off (sheet slacked) until the lower portion
is not pulling properly. To obtain the twist without slacking away too much on the
sheet, the lead is moved aft 2 or 3 in. on small boats and up to 2 or 3 ft. on larger
ones. Fig. 10 shows how the jib must be matched to the angle of the mainsail at
various heights above the deck for close-reaching and broad-reaching. Accuracy in
following these directions will help to increase the speed of your boat.
Probably the least understood factor in good sailing is the location of the pivoting
point or center of gravity, which should be about under the center of buoyancy.
In loading a boat, serious changes may occur. The center of gravity may be moved
forward or aft by such things as installing a larger motor than was intended in
the design of the boat, the addition of a larger water tank, the placing of food
stores, the stowage of luggage or spare sails, etc. Fig. 12 shows the effects of
correct and incorrect ballasting. The top details show what happens when there is
too much weight at the stern, the center details show effects when ballast is too
far forward, and the lower details show results with a correctly balanced boat.
You can determine the pivoting point by looking across the deck and moving forward
and aft until the point about which the boat seems to pitch is located. It is usually
best to determine the pivoting point of a boat in a somewhat choppy sea. If the
pivoting point is about one-third the length forward from the stern, the ballast
is approximately correct. Fig. 13 shows the effects of various pivoting points on
a small boat. Also, with proper weight distribution disturbing sail motion is reduced.
In the photo, Fig. 11, you can see a comparatively large bow wave. This large
wave exists only on the lee bow, for the weather bow wave is much smaller. Fig.
15 shows how the bow shape of most boats produces a larger bow wave on the lee than
on the weather side. The lee bow wave becomes in effect a large roll of water which
tends to force the bow to turn into the wind and this wave becomes more pronounced
as the angle of heel is increased. For this reason a squall, which heels a boat
considerably, can be expected to create a very heavy weather helm quickly. Unless
the thrust of the lee bow wave is met with an equal thrust at the stern, (from the
rudder), the boat will turn to weather. Under such conditions however, the mainsail
can be eased off slightly until only the jib is closely trimmed. The jib may be
considered as being too weak to balance the mainsail, and the latter must be eased
as the jib is actually well trimmed and working. Otherwise, the entire balancing
force must come from the rudder, which comes into play when the tiller is held to
the weather side.
There are times however, when a slight amount of weather helm is of great advantage.
Fig. 16 shows two common types of sailboat hulls - the fin keel and the deep keel.
The fin keel should have its sails balanced very accurately because even a slight
helm is a serious drag. The deep keel, on the other hand, becomes more effective
than it is when the boat is sailing close-hauled with a slight weather helm. This
is due to the fact that the keel and rudder are continuous and streamlined in a
single unit, which forms a curve similar to the air-foil curve of an airplane wing,
or of a sail. This curve is formed on the weather side of the keel-and-rudder assembly,
(with slight weather helm), and makes it act somewhat like a wing or sail. The result
is that there is a distinct tendency to draw the boat to windward. It becomes especially
noticeable in the marked reduction of the leeway (sideslip), which is normally experienced
when sailing close-hauled. With a deep-keel boat, you can determine the most advantageous
position for the tiller when the boat is out of the water by laying a straightedge
along the rudder and the after portion of the keel or false keel, and forcing the
rudder over until a straight line is formed. Then carefully note the angle made
by the tiller, and trim the sails when close-hauled or close-reaching so that this
angle will hold the boat on a straight course. When this is done, a marked improvement
in performance will be observed. The helm is the clue to sail balance when reaching
as well as when sailing close-hauled. Fig. 14 shows the four conditions of poor
sail balance dis-closed by pronounced weather or lee helm.
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