Ronstan Series 75 Two-Speed Mainsheet System 4:1 / 8:1 – Top & Bottom Blocks – RF72900
The Ronstan Series 75 Two-Speed Mainsheet System (RF72900) is a high-power control system designed for sports boats and keelboats up to 12m (40ft), where increased purchase and load handling are required.
This complete system delivers a versatile two-speed configuration, combining a fast 4:1 ratio for rapid trimming with a powerful 8:1 ratio for precise control under higher loads. The continuous mainsheet runs through the system and exits via twin cam cleats on the lower block, allowing instant selection between speed and power.
When sailing upwind, one tail can be cleated while the other is used for fine trimming via the higher purchase. During manoeuvres such as mark roundings, both tails can be worked together to quickly dump or trim the mainsail, ensuring fast and controlled sail handling.
With a Safe Working Load of 1100kg across all components, this system is engineered for higher-load applications and larger sail plans. It is suitable for boats with mainsail areas up to:
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End-boom sheeting: 42m² (452ft²)
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Mid-boom sheeting: 27m² (290ft²)
Built to Ronstan’s Series 75 specification, the system features 75mm sheaves optimised for lines up to 12mm, acetal ball bearings for low-friction performance, and anodised aluminium cheeks for strength and durability. Ratchet sheaves provide additional holding power, reducing effort on the trimmer under load.
A powerful, race-ready mainsheet system offering enhanced control and mechanical advantage for demanding sailing conditions.
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