Harken Blocks
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Harken Blocks: Engineering the Perfect Redirect
Sailing blocks are the unsung workhorses of every rigging system, and no manufacturer has devoted more engineering attention to them than Harken. At their core, blocks are precision pulley systems that redirect and manage control lines with minimal friction. A Harken block uses a rotating sheave mounted inside a housing to redirect control lines with minimal friction, spinning on a bearing — either a simple bushing, a ball-bearing race, or a Harken-patented Carbo composite bearing. The result is a system that creates mechanical advantage through block-and-tackle arrangements, allowing sailors to manage loads far exceeding their own physical strength.
Iconic Product Lines
Harken blocks are famous for their ball-bearing technology, which ensures sheaves spin freely even under extreme tension. This commitment to low friction runs across their entire lineup, from small-boat hardware to big-boat performance gear.
- Carbo Air Blocks — Carbo AirBlocks® are 60% stronger and 30% lighter than classic blocks and are the go-to for mainsheets, vangs, and control lines on everything from dinghies to offshore racers.
- Carbo Ratchet & Ratchamatic® Blocks — Harken ratchet blocks hold part of the sheet's load, let you trim and ease with complete control, and enable higher trimming speeds — making it much easier to hand-hold higher loads by only allowing the sheave to turn in the trimming direction. When holding or releasing the load, the faceted sheave grips the line to reduce fatigue and give you more control. The Ratchamatic® features a spring-loaded pawl mechanism that locks under load, reducing hand fatigue on mainsheets and vangs. Lightweight Carbo Ratchets are available in 40mm, 57mm, and 75mm sizes.
- Black Magic® Air Blocks — Designed for big-boat applications, these high-load blocks feature Torlon® roller bearings for strength and carbon-black UV stabilizers for a long life in the sun. Their combination of efficiency, strength, and size makes them appropriate for boats in the 30' range and larger.
- Zircon Series — Harken Zircon Blocks are the most efficient small-boat block Harken has designed yet, featuring industrial ceramic ball bearings mounted inside caged races that keep the bearings separated so they don't bunch up, touch, and stop each other.
- Micro Blocks — Harken Micro Blocks stand out with a compact design, excelling in scenarios where a smaller footprint and finer control are crucial — such as on smaller dinghies or lightly loaded control lines of boats of all sizes.
- Cruising ESP Blocks — These blocks offer a simpler design with less expensive construction while remaining strong and efficient, with sleeve bearings to handle high static loads — ideal for halyards or limited purchase systems on cruising boats.
Intelligent Design Details
Harken blocks feature densely packed nylon resin side-plates with long-glass fibres for a high strength-to-weight ratio, machined aluminium hard-coat anodised sheaves for excellent break load and robust corrosion resistance, and UV-stabilised ball bearings, sheaves, and side-plates incorporating carbon black for maximum sun protection.
A valuable feature of the Ratchamatic® block is its "load-sensing" ability, which can be adjusted to suit the user's strength or the prevailing conditions by simply changing the setting with an Allen wrench. Meanwhile, Harken Carbo Ratchet Blocks are also available with Power3 Grip Sheaves, offering holding power up to twice that of a standard Harken Ratchet Block — providing small one-design racers with increased options to handle a variety of wind and sea conditions.
From Dinghies to Megayachts
Harken has grown from a backyard dream of two brothers to a global reality with offices around the world and distribution in 48 countries — their sailboat blocks and hardware have performed at the highest level in events like the America's Cup, the Volvo Ocean Race, and the Olympics, appearing on everything from the smallest dinghies to the largest megayachts.
Whether you're rigging a one-design racer or upgrading a bluewater cruiser, browse the full selection of Harken Blocks to find the right block for your application, or explore the complete Harken brand lineup and the full Blocks category for more options.