Marty Rieck was Harken's Sales Manager for many years. Both professionally and personally, boats were his life and his knowledge of sailboat hardware and systems continuously amazed those who worked with him. A prolific writer, Marty wrote the following article on winches for Sailing World Magazine.
Low Power = Fast Trim (Light Loads)
High Power = Slow Trim (High Loads)
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Because sailboats depend on human power to
perform such tasks as sail trimming, rig adjustment, steering and sail
changing, a wide variety of mechanical devices have evolved to allow relatively
weak people to control highly-loaded systems. Block and tackles, hydraulics,
and winches are the most common devices to magnify "people power."
Levers increase force and torque
Winches use the principle of physics called Levers to increase force and torque. Two types of levers are used: one internal, the other external. The external is the lever arm (the winch handle) and the internal is the revolving sets of rotary levers called gear sets. Power and torque increase as speed decreases.
Power Ratio
Power ratio is the term we use to describe the ability of winches to pull a load.
Harken uses a winch's power ratio as the winch name.
For example, a 48 has a power ratio of 48:1 in the
final gear. This means a kilo of handle input, generates 48 kilos (106 lbs)
of power.
Calculating Power Ratio
Power ratio is calculated as follows: (Handle Length/Drum Diameter) x Gear Ratio=Power Ratio.
• Calculate power ratio using a 254 mm (10") winch handle
Shorter handles: decrease power because they have shorter levers
Drum rpm increases: handle turns through smaller radius
• Measure drum diameter or find specifications in Harken catalog.
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Gear ratio can be determined from the Harken specifications.
Speed/Power Inversely Related
In winches, as in any simple machine, speed and
power are inversely related. If you want fast trimming, you will have lower
power. If you want high power, you will have slow trimming. This is the reason
that all moderate and large winches are offered with two or three speeds. For
light loads, you can use a fast speed that doesn't offer much power, and as the
load increases, shift to a higher power and trim the last few feet at lower
speed.
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Wide Drum Diameter:
High Line Speed
= Low Power
Short Winch Handle: Line Speed = Low Power
Each revolution of the winch handle pulls in an amount of line equal to the circumference of the drum.
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Winch Speed
When we talk about speed in a winch, we mean the amount of line that is pulled for each revolution of the
handle. The primary considerations in determining winch speed are the gear ratio
and the drum circumference. Since the line is wrapped on the drum, each
revolution of the winch will pull in an amount of line equal to the
circumference of the drum (Circumference= pi x diameter).
When you are looking for a "fast" winch, you
will use a wide body winch with a large diameter drum. Unfortunately, since the
drum diameter is also a function of the power ratio, the wide body winch will
offer less power for the same gear ratio. The average racing boat that uses
wide body winches compensates for this loss of power by simply cranking harder,
though a crew of musclemen is a luxury most club racers can't afford.
Faster Speeds
Faster winch speeds can also be achieved with
three-and four-speed winches. A typical smaller three-speed winch, like the 60.3ST
offers direct drive in first speed. The drum turns one revolution for each revolution of the handle, so under low loads, sheets can be trimmed very fast. While this speed is not geared, there is a slight mechanical advantage obtained from the relationship between the lever (handle) and the drum diameter. Larger three-speed winches, from the 56.3 up, typically have a geared first speed because even under low loads, some additional mechanical advantage is required.
four speed Winches
Four-speed winches are typically three-speed
winches which offer a choice of a direct drive first speed or a geared first
speed. The crew selects the appropriate first gear and then uses the three
speeds available. For example, in light air upwind, or for most spinnaker
trimming, they might well choose a direct drive speed for very fast trimming,
while for tacking in a breeze they would use the geared first speed.
handle length
Another way to increase the speed of a winch is
to use a shorter handle, typically an 8" (203 mm) handle. The 8" handle is
faster because it swings in a smaller arc and a crew can rotate the handle
faster. The same power problem is experienced, though, as handle length is a
part of the power ratio calculation and decreasing the handle length 20%
reduces power by 20%. Still, the 8" handle is a very effective and inexpensive
means of increasing winch speed in light and moderate conditions.
Lines lead to winch at
5-to-8-degree angle.
Ls=Sheet Load
Lgh=Gearing Housing Load
Ldp=Drive Pinion Load
ALIGNMENT:
Line Entry at Final Drive Gear Location = Decreased Load on Gear Housing and Drum Bearings 
Ls=Sheet Load
Lgh=Gearing Housing Load
Ldp=Drive Pinion Load |
Winch Alignment key
Other factors that influence the final power of a winch include whether two people can grind the
last few feet of sheet using a doublegrip handle and even the placement of the
winch on the deck. Many winches are positioned on coaming, which forces the
crew to lean across seats or otherwise assume uncomfortable and inefficient
postures. Runner winches are often difficult to grind because they are to
windward where the crew is reaching up, rather than leaning over the winch.
line entry angle important
Winches are further affected by how they are
mounted on the boat. The most important factor is to ensure a proper line entry
angle. Lines must lead up to a winch at about a 5-to-8-degree angle to prevent
overrides of the sheet on the drum. If lead blocks are too high to allow this
angle up to the drum, the winch must be raised slightly, or you will have
serious problems preventing overrides.
It is also important to mount the winch so the
line is properly aligned to the final drive gear pinion. Improper alignment
dramatically increases the load on the gear housing resulting in inefficient
operations, and in severe cases, in winch failure.
Let's look at two examples:
one with the load aligned properly and one with the opposite situation. In case
A, with the proper alignment, the load on the gear housing is minimized since
Ls and Ldp are in opposite directions. In case B, where the load is improperly
aligned, the load on the drive gear is maximized - Lgh+L1+Ldp - but this time
the loads are in the same direction and adding up.
Links:
Brion Toss article: www.harken.com/winches/BrionToss_Winchpower.php
Harken article: www.harken.com/servicingwinchesmikelee.phpr.php
Harken article: www.harken.com/charts/captivereelwinch.php
