Forces on sheet lines can be overcome by the use of winches, which combine gear reduction and leverage. Winch handles exert leverage on drums around which the sheet line is wrapped. Gears inside drive the drum and have ratcheting pawls that prevent the winch from turning in the wrong direction.
The difference between drum radius and winch handle radius is the leverage. Increasing power is accomplished by gear reduction, which is the number of times the drum rotates for every rotation of the winch handle.
Mechanical advantage, known as power ratio, is created from the combination of leverage and gear reduction, which is stated as:
Length of handle x gear ratio
Radius of drum
In other words a winch handle length of 12 inches, a gear reduction of 2:1, and a drum diameter of 6 inches produce a power ratio of 4:1. The higher the power ratio, the more power is offered and the slower the drum turns to pull in the sheet—more power equals less speed.
Factors used in selecting a winch include sail area, rig type, displacement, and hull type (mono or multi).
STYLES
- Standard winches are usually defined as not self-tailing and are commonly found on smaller boats for sheet lines or on medium size boats for halyards.
- Self-tailing winches are recommended for all applications, particularly when sailing short handed.
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GEARING
- Non-geared, single-speed winches offer the least mechanical advantage. The handle and drum rotate in the same direction, usually clockwise, and the number of rotations of the drum is the same number as the rotations of the winch handle.
- Single-geared, two-speed
winches offer increased power when the handle is rotated counterclockwise. A clockwise turn offers a non-geared 1:1 power ratio; a counter clockwise turn may offer up to 5:1 power ratio. Gear ratios vary by manufacturer and model.
- Multi-geared, single-speed winches, with gear reduction in one direction, offer more power than non-geared winches. The handle works a series of gears in the drum. If the handle is turned counterclockwise, it works as a ratchet, allowing more leverage on a shorter throw of the handle.
- Multi-geared, two-speed winches,
with gear reduction in both directions. First speed (fast speed) is first gear, usually the clock-wise direction (but not always!). Second speed (low speed) is the second gear, usually the counterclockwise direction.
- Multi-geared, three-speed winches
offer high power ratios and fast trimming and are usually found only on race boats.
POWERED WINCHES
- Electric winches are recommended for higher loads and shorthanded crews, but only when no systems on the boat are hydraulic, and there are few electric winches. Standard voltages are 12 or 24-volt DC. Battery and charging capacity may need to be added to accommodate electric winches.
- Hydraulic winches are also recommended for higher loads and shorthanded crews, when there are other hydraulic systems on board. These are not recommended for a retrofit unless the vessel already has an on board hydraulic system.
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DRUM MATERIALS
Four basic materials are used for drums, each with their strengths and weaknesses.
- Anodized aluminum
is easily gouged by wire halyards, but is the lightest and least expensive of the body materials, usually in black.
- Chrome on bronze looks good until stripped by wire halyards, but is otherwise durable.
- Bronze
is also durable, but requires polishing, unless the traditional green appeals to you. Stainless steel is the most durable of the drum materials and maintains its looks, but it is also expensive.
TIPS
- Lewmar recommends that "the rope enter onto the drum at an angle of 5 to 10 degrees to the base axis of the winch. To achieve this angle it may be necessary to use a base wedge when installing the winch. The winch must be mounted on an even surface."
- If replacing a winch, carefully check the mounting holes of the new winch against the old holes to be sure they match, if at all possible.
- If installing a self-tailing style winch, the stripping arm should be pointed toward the location of the grinder, usually between five o’clock and seven o’clock.
INSTALLATION
The average mechanically skilled person with minimal tools can install winches.
Toolbox:
- Drill and bits
- Wrench
- Screwdriver
- Sealant
- Possibly allen wrenches
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