RONSTAN Series 55 Orbit BB Cheek Block, RF55151

Series 55 Ball Bearing Orbit Blocks™ feature our 2-stage bearing system and are engineered to achieve the highest possible strength-to-weight ratio. They are lightweight and high-performance 55mm blocks commonly used for mainsheets and spinnaker sheets on dinghies, sports boats, and small keelboats up to 9m (30').

Lightweight

Kilogram for a kilogram of working load, BB and RT Orbit Blocks™ are the world's lightest. The unique orbital design allows the bearing to only be in the active areas of the floating sheave. This minimizes the mass of the inactive return race and hub.

Weight and bulk are further reduced in the different block configurations. The ball-bearing single and becket block has a through-sheave becket arrangement. The result? The lowest weight possible.

Multi-sheave blocks have only single intermediate cheeks and an ultra-light and efficient head arrangement. This gives a 30% weight-saving advantage over the nearest competitor. Other brands just link together their single blocks. This results in unnecessary double cheeks between each sheave, held together by a heavy steel channel across the top of the block.

Highest working load in its class

The orbital ball-bearing arrangement gives the largest possible bearing race diameter. This maximizes load performance. The proven Ronstan 2-stage bearing system features high compression grade acetal ball bearings and a secondary full-contact bearing. This gives minimum friction across the full working load range.

The floating sheave and bearing system is supported by a fibre-reinforced load frame. The design was computer-modeled to be stress-optimized. The Dyneema° Link is produced from FSE Robline SK75 fibre, which is 10 times stronger and lighter than steel, and provides the final connection from the block to the load point.

Note: Special Order Only

• Ultra Lightweight
• Low friction 2-stage Orbital ball bearing system
• Highest working load in its class
• Low profile and compact
• High-performance cleating
• Recessed underside to suit curved mounting surface

Applications

• Mainsheet systems on dinghies, sports boats, and small keelboats to 9 m (30 ft)
• Spinnaker sheets on dinghies, sports boats, and small keelboats to 9 m (30 ft)
• Halyard, Vang, and Backstay application on boats to 8 m (26 ft)
• Control line applications on larger yachts

Materials

• Ball bearings - High compression strength carbon black Acetal
• Stage 2 bearing - Carbon fibre reinforced, PTFE-impregnated Nylon
• Frame/Cheeks - Toughened, glass fibre-reinforced Nylon
• Rope Link: UV stabilized, multi-strand impregnated SK75 Dyneema°
• Sheave: Carbon fibre-reinforced, PTFE-impregnated Nylon
• Head fitting: Grade 316 stainless steel
• Ball Bearings: High compression strength carbon black Acetal
• Stage 2 Bearing: Glass fibre-reinforced, MoS2-impregnated Nylon
• Frame/Cheeks: Toughened, glass fibre-reinforced Nylon