Ronstan Series 55 Orbit Block™, Ratchet, RF56100

Ronstan Series 55 Orbit Block™ Ratchet – Automatic & Manual (RF56100)

High-performance 55mm ratchet block with automatic and manual engagement modes, delivering industry-leading holding power for mainsheet and spinnaker systems.

The Ronstan Series 55 Orbit Block™ Ratchet (RF56100) is a high-performance ratchet block engineered for demanding sailing applications where control, holding power, and versatility are critical.

Designed with both automatic and manual engagement modes, this block offers unmatched flexibility. In auto mode, the ratchet engages under load and disengages when load is released, allowing sheets to run freely for fast easing and smooth gybes. In manual mode, sailors can switch the ratchet on or off as required, providing a more traditional setup preferred by many experienced racers. This dual-mode functionality allows you to fine-tune your setup to match your sailing style and conditions.

At the core of the block is Ronstan’s advanced Generation 2 ratchet sheave design, delivering exceptional holding power of up to 20:1—significantly higher than traditional ratchet blocks. The CNC-machined anodised aluminium sheave features 12 gripping faces that provide direct resistance to rope movement, distributing load evenly while reducing rope wear. The unique geometry draws the rope into the gripping area under load, improving both control and efficiency.

Built for strength and durability, the block features a toughened glass fibre reinforced nylon frame, high compression strength acetal ball bearings, and a grade 316 stainless steel head fitting. This robust construction ensures long-term reliability in high-load, high-performance environments.

Ideal for mainsheet systems, spinnaker sheets, and control line applications on dinghies, sportsboats, and small keelboats up to 8 metres, the Series 55 Ratchet Orbit Block™ delivers the control and confidence needed for competitive sailing.

Ideal For

• Dinghy mainsheet systems

• Spinnaker sheet control

• Sportsboats and keelboats up to 8m (26ft)

• Halyard, vang, and backstay applications

• Performance sailing requiring high holding power

Key Features

• Automatic ratchet mode engages under load and disengages when released

• Manual ratchet mode for user-controlled engagement

• Generation 2 CNC-machined sheave with up to 20:1 holding power

• 12 gripping faces for improved load distribution and reduced rope wear

• High-performance ratchet system for precise sheet control

• Smooth easing for gybes and rapid adjustments

• Durable construction for high-load applications

• Designed for both racing and high-performance cruising setups

Technical Specifications

Model: RF56100
Sheave Size: 55 mm
Ratchet Type: Automatic + Manual engagement
Holding Power: Up to 20:1

Materials:

• Sheave: Anodised aluminium (CNC-machined)

• Ball Bearings: High compression strength carbon black acetal

• Frame/Cheeks: Glass fibre reinforced nylon

• Head Fitting: Grade 316 stainless steel

Applications:

• Boats up to 8m (26ft)

• Mainsheet, spinnaker sheets, halyards, vang, backstay