Single block 29-57mm swivel | Master Windrider
Windrider is a series of ball-bearing blocks designed with competitive sailing in mind, but they are also a cost-effective alternative for the cruising sailor. The high-performance composite side plates are engineered to ensure optimal performance even under high loads. The blocks have high weather resistance, which protects them from failure in all types of sailing conditions and provides long-lasting durability.
APPLICATION AREA
The swivel allows the block to rotate and align itself with the direction of the pull. The block is suitable for, among other things:
- Mainsail systems, headsails, and spinnakers
- Halyards, vangs, and backstays
- Control lines for boats of all sizes
TECHNICAL SPECIFICATIONS
Materials
- Sheave: self-lubricating acetal composite
- Ball bearings: self-lubricating acetal composite
- Side plates/frames: reinforced fiberglass-nylon composite with UV stabilization
- Shackle: Forged stainless steel of grade A4/AISI316
Dimensions and loads
| Sheave Ø (mm) | 29 | 57 |
| Max. line Ø (mm) | 8 | 10 |
| Weight (g) | 25 | 89 |
| Working load (kg) | 160 | 370 |
| Breaking load (kg) | 500 | 1200 |
FREQUENTLY ASKED QUESTIONS (FAQ)
How do I choose the right size block?
Base your choice on the line diameter and the load the block will carry. 29 mm sheave: line up to 8 mm; 57 mm sheave: line up to 10 mm. The working load should always be higher than the actual load.
What is the difference between working load and breaking load?
The working load is the load the block is intended to be used with continuously. The breaking load is the load at which the block will fail and should never be used as a design value.
Does the block need to be lubricated?
No, the sheave and ball bearings are made of self-lubricating acetal composite. It is recommended to rinse the block with fresh water after use in salt water.