The Ronstan Series 55 Orbit Ratchet is a 55 mm ratchet block offering both automatic and manual engagement modes, up to 20:1 holding power, and a lightweight 82 g build. Built around Ronstan's patented Generation 2 sheave with 12 gripping faces, it suits mainsheet, spinnaker, vang, backstay and halyard control on dinghies, small keelboats and sportsboats up to about 26 feet.
Ronstan Series 55 Orbit Ratchet at a glance
| Specification | Detail |
|---|---|
| Sheave size | 55 mm |
| Weight | 82 g |
| Maximum line diameter | 10 mm (3/8 in) |
| Engagement | Auto + Manual (switchable) |
| Holding power | Up to 20:1 ratio |
| Pin size | 5 mm |
| Maximum working load | 250 kg (550 lb) |
| Breaking load | 750 kg (1650 lb) |
What makes the Series 55 Orbit Ratchet different?
The Series 55 Orbit Ratchet is one of the only ratchet blocks on the market to offer both automatic and manual engagement in a single block. In auto mode, the ratchet mechanism engages the moment load is applied and releases as soon as the line is eased. This relieves the strain of holding a loaded sheet for long stretches, yet still lets the line run out smoothly when easing sheets or gybing an asymmetric spinnaker. In manual mode, the sailor switches the ratchet on or off as needed — the setting most experienced crews prefer for precise control.
How does the Generation 2 sheave improve grip?
Holding power comes from Ronstan's patented Generation 2 crosshole sheave geometry, NC-machined for precision. Where traditional ratchet sheaves have only 8 gripping faces, the Gen 2 sheave has 12. Its resistance faces are straight, which spreads the load evenly and reduces rope wear, and each face is offset from the radial line so the rope is drawn down into the gripping area under load. The result is the highest holding power in its class — up to 20:1 — on a block that still weighs just 82 g.
Which boats and applications suit the Series 55?
The Series 55 Orbit Ratchet handles lines up to 10 mm, which places it mainly on boats up to about 26 feet. It is ideal for the mainsheet systems of single-crewed and medium dinghies, and for the spinnaker sheet, halyard, vang and backstay applications on small keelboats and sportsboats. The table below shows typical rigs and where the block is used.
| Boat | Type | LOA (ft) | Application |
|---|---|---|---|
| Optimist | Centreboard | 8 | Mainsheet |
| Moth | Centreboard | 11 | Mainsheet |
| Sunfish | Centreboard | 14 | Mainsheet |
| International 14 | Skiff | 14 | Mainsheet, Shroud Tensioning System |
| Finn | Centreboard | 15 | Mainsheet, Traveler |
| 470 | Centreboard | 16 | Mainsheet, Spinnaker |
| 49er | Skiff | 16 | Mainsheet, Spinnaker |
| Melges 20 | Keel | 20 | Mainsheet, Spinnaker and Jib System |
| Viper 640 | Sport Boat | 21 | Mainsheet, Spinnaker |
| J24 | Keel | 24 | Mainsheet and Spinnaker System |
What is the Series 55 Orbit Ratchet made of?
The block is engineered for high load in a light package. The sheave is hard-anodized aluminum running on carbon-black acetal ball bearings, the frame and cheeks are glass-fiber-reinforced nylon, the rope link is SK75 Dyneema, and the head fitting is Grade 316 stainless steel.
| Part | Material |
|---|---|
| Sheave | Hard-anodized aluminum |
| Ball bearings | Carbon-black acetal |
| Frame / cheeks | Glass-fiber-reinforced nylon |
| Rope link | SK75 Dyneema |
| Head fitting | Grade 316 stainless steel |
Frequently asked questions
What is the difference between auto and manual mode on the Orbit Ratchet?
In auto mode the ratchet engages automatically when load comes on and releases when the line is eased, ideal for smooth spinnaker work. In manual mode you turn the ratchet on or off yourself for full control.
How much holding power does the Series 55 Orbit Ratchet have?
It offers the highest holding power in its class — up to 20:1 — thanks to the 12-face Generation 2 sheave.
What size line does the Series 55 take?
It accepts lines up to 10 mm (3/8 in), which suits most control lines on boats up to about 26 feet.
How much does the Series 55 Orbit Ratchet weigh?
Just 82 g, making it one of the lightest ratchet blocks in its size class.
What boats is the Series 55 Orbit Ratchet best for?
Single-crewed and medium dinghies, small keelboats and sportsboats — on mainsheet, spinnaker sheet, halyard, vang and backstay systems.
Why does the Generation 2 sheave have 12 gripping faces?
The extra faces (versus 8 on traditional designs) with straight, radially offset resistance surfaces distribute load, reduce rope wear, and draw the line into the grip zone for stronger, gentler holding.
Shop all Ronstan Orbit Blocks →