The pulleys of a sailing boat: Definitions, techniques and uses

There are several types of pulleys for boats. While their mechanics always remain the same, they serve different functions. A closer look at this highly varied deck hardware.

Pulleys are found on all types of sailing boats, from the simple dinghy to the sailing yacht. They are used to trim the genoa, the mainsail or the spinnaker, among other things. But they can also serve many other purposes.

A block (pulley) on a sailing boat makes it possible to multiply mechanical advantage and to redirect a line — a halyard or a sheet — and to move a load in a different direction. As such, it must withstand two types of loads: a static load and a dynamic load.

What are the different parts of a sailing boat block?

A boat block, like all other pulleys, is a mechanical component. This component is more or less robust, depending on the requirements, its function and the size of the boat. Blocks on sailing boats are made of different materials: plastic, stainless steel and, more recently, textile. Let us look together at the important parts of a block:

•  The sheave: The sheave is the moving part over which the line runs.
• The becket: The becket is a fixed pin to which the line is attached, the starting point of the tackle.
• The jammer: The jammer locks the line as it exits the block.

What are the different types of blocks for a sailing boat?

As we have seen above, a block can serve different functions. It can be used as a mainsheet tackle, to redirect lines at the foot of the mast, or simply to run a sheet. Different functions mean different blocks. Indeed, blocks have adapted to their function over time. Here are the different types of blocks:

• Single block: This is the basic block, consisting of a single sheave. It can be used for various manoeuvres.
• Fiddle block: The fiddle block allows a line to be run in a double configuration (a larger sheave alongside a smaller second

  

  sheave). It is generally used for a tackle in the cockpit.
• Block with becket: This block can be attached to a fixed point and can be used for tackles.
• Block with jammer: This block can grip the line and is also used for tackles, allowing the trim to be locked.
• Double and triple blocks: These blocks are used only for tackles and are found at the opposite end of the block with jammer.
• Deck block (flush-mount block): This block is designed to be fastened to the deck and is often used for the sheets of the forward sails. It can be fitted with a jammer or a stopper.
• Snap shackle block on a spring (stand-up block): The stand-up block is mounted on a spring, so it does not bang against the deck. It is often used for spinnaker manoeuvres (guy/brace).

The different bearing types of blocks

Standard blocks, without ball bearings

This block is the most economical and the simplest. The sheave rotates on a stainless steel axle. They are largely sufficient for static loads, for example at the foot of the mast, but can be used for all functions, especially for a cruising programme.

Ball bearing blocks

On a ball bearing block, the sheave rotates on ball bearings. These blocks are much faster and… more expensive. They are very useful for spinnaker manoeuvres, for example. Their drawback is that they cannot withstand loads that are too heavy — the balls get crushed.

Roller bearing blocks

The roller bearing block is the top-of-the-range block. The balls are replaced by rollers, providing the same qualities as a ball bearing block while withstanding high loads. Its drawback is its… price.

Friction rings

A friction ring can replace a block in certain situations. It is a simple and less costly alternative. The advantage of a friction ring is its strength-to-weight ratio: a friction ring is roughly 10 times lighter than a block. It is increasingly used in rigging and rope work.

How to choose your sailing block?

To make the right choice of block, we have already provided some answers. First of all, it must meet your needs. You must therefore choose a type of block that suits the function you intend to give it.

Next, you will need to take two other factors into account when choosing your block:

• The size of your line: Indeed, first of all, your block must be suited to the diameter of your sheet or halyard. If you have a 6 mm line, for example, the block must be at least that size.
• The breaking load of the block: This is one of the most important factors. The breaking load is the force the block can withstand. Manufacturers sometimes give the working load limit of the block instead. This corresponds to half the breaking load. Note that the greater the deflection of the block, the higher the working load. For example, a block deflecting a halyard through 180 degrees will have a working load twice as high as the load on the sheet.

Calculation of the working load of a sheet: approximately 25 kg per square metre of sail area, shared between the halyard point, the tack and the clew. For example, take one third for the clew.