Ronstan Core Blocks™

Core Blocks Logo

Use Them Anywhere

>A balanced design approach incorporating functionality, performance and style makes our Core Blocks™ the right choice for performance cruising or racing applications. A tuned 2-stage bearing system provides excellent performance across the full working load range with an integrated thrust bearing feature and the resilience to handle high dynamic or static loads. Acetal & aluminium sheave options, alloy cheeks and stainless fixings complete the durable package.

Ronstan Red Dot Award Winner 2011


Dynamic and high static load performance

Core Blocks™ incorporate our proven 2-stage bearing system.

Stage 1 - Under moderate loads, acetal ball bearings ensure minimum friction.

Stage 2 - Under heavy loads, where deformation of ball bearings alone would result in increased friction, a sliding acetal bearing on a polished stainless steel race takes over, maintaining low friction performance. Additionally the ball bearings are configured to act as a thrust bearing between the sheave and cheeks, preventing the sheave from rubbing on the cheeks and causing friction when the line lead in and out of the block isn’t perfect; particularly important for foot blocks.

Aluminium alloy cheek plates

Block cheeks are manufactured from the highest quality alloy for maximum strength. Material optimisation and the cut-away design minimises weight and allows easy fresh water rinsing of salt and debris from the bearings. Cheek design has been further styled with flaring at the block throat and reduced gap between the cheek and sheave, minimising rope wear, and the hollow hub can be used as a becket take-off or tie-up point.


Aluminium sheave options

Selected models are available with an aluminium sheave which has a deep groove profile specifically made for use with wire.

Universal head

The head assembly incorporates a brass bearing washer to provide smooth 360° rotation of the post and shackle. A set screw arrangement allows the head to be locked at 0° or 90°. Shackles are high quality forged grade 316 stainless steel.

Suits pre-spliced lines

Removable becket pins allow fitting of pre-spliced lines. The flush fit becket pin head is kind on deck surfaces and won’t snag lines.

Fully articulated stand-up

Stand-up models have a low profile linkage that provides full rotation and articulation. A high strength precision cast padeye minimises the footprint and a dedicated rubber boot ensures the block is held upright when not loaded.

2-Stage Bearing System
Acetal and Aluminium Sheave Options
Aluminium Alloy Cheek Plates
Universal Head
Suits Pre-Spliced lines
Fully Articulated Stand-Up

Half the friction

Ronstan Core Blocks™ have half the friction, or less, compared to the nearest competitor; a feature that delivers easier and safer sailing, particularly when short-handed or cruising with the family.

Core Blocks Friction Graph

Core Block™ Demonstration Video - Range overview, product features, applications and usage information