/ 
In the world of sailing, every component plays a crucial role in the boat's performance and safety. Among these components, blocks are essential for the rig's smooth operation, enabling sails to be handled with precision and efficiency. Choosing the right pulley is not a task to be taken lightly, as the wrong selection can lead to malfunctions, premature wear or even accidents at sea. To guide boaters in this important decision, it is essential to understand the main criteria for choosing a pulley. This article explores three fundamental criteria to consider.
1 - Workload and type of shift
Manufacturers' data sheets give two indications: working load and breaking load. In most cases, the breaking load is twice the working load.
- Working load: The working load is the maximum force the pulley can withstand in normal use. It is crucial to choose a block with a rated working load that is appropriate for the forces being exerted on the sailboat. This depends on the size of the sailboat and the function of the block (halyard, sheet).
- Breaking load: This is the force at which the pulley will fail. It is recommended not to use a pulley under these forces.
Working loads depend on the bearings used in the pulleys. Bearings play a crucial role in pulley performance, reducing friction and enabling smooth movement. There are three main types of bearing used in sailboat pulleys:
- Friction pulleys these bearings, also known as bushes, are often made of synthetic materials such as nylon or Delrin. They are simple, robust and require little maintenance. Although they have higher friction than ball or roller bearings, they are often sufficient for applications where loads are not excessive and strength is paramount. They are ideal for static applications, such as halyards that don't work too dynamically.
- Ball-bearing pulleys these bearings consist of steel or ceramic balls placed between two rings. They offer low friction and excellent durability. However, even ceramic balls deform under heavy load. As a result, these pulleys are very pleasant under dynamic loads (e.g. spinnaker sheeting), but less so under heavy loads (e.g. runners).
- Roller pulleys : Instead of balls, these bearings use cylindrical rollers. They are particularly effective in supporting high radial loads, and are often used in pulleys subjected to high forces. Roller bearings offer a larger contact area, which can improve load distribution.
2 - String diameter
The pulley must be compatible with the diameter of the rope used. Using a pulley that is too small or too large can lead to premature wear and sub-optimal performance. The sheave groove must be adapted to the rope.
Similarly, the diameter of the pulley influences the strength of the rope: the wider the arc, the lower the stress.
3 - Materials and corrosion resistance
On deck or in the mast, pulleys are often exposed to severe marine conditions (salt water, sunlight...). It is therefore essential to choose sheaves made from corrosion-resistant materials, such as stainless steel, anodized aluminum or certain engineering plastics. Bearings (if present) must also be of high quality and corrosion-resistant to ensure smooth, long-lasting operation.
By taking these 3 criteria into account, you can select pulleys that will meet the specific requirements of your sailboat and ensure safe, high-performance sailing.
