If you're looking for the ultimate low-friction sailing block, the Harken Zircon Block range represents the pinnacle of Harken's small block technology. Designed for sailors who demand the smoothest possible control systems, Zircon blocks combine advanced ceramic bearing technology with lightweight construction to deliver exceptional efficiency where every adjustment counts.
Originally introduced in 40mm and 57mm sizes before being expanded with a compact 29mm range, Harken Zircon Blocks are now available in 18 different configurations. Whether you're upgrading a single control line or building an entire purchase system, there's a Zircon block designed for the job.
What Makes Harken Zircon Blocks Different?
The biggest difference lies inside the block.
Rather than conventional stainless steel ball bearings, Harken Zircon Blocks use industrial ceramic ball bearings running within precision caged races. The bearing cage keeps each ball perfectly separated, preventing them from bunching together under load and allowing the sheave to begin rotating with remarkably little effort.
This significantly reduces start-up friction – the force required to get the sheave moving in the first place. While that might sound like a small improvement, it's exactly what sailors notice when trimming sails in light airs or making constant, precise adjustments to control lines.
The result is:
- exceptionally smooth operation
- outstanding responsiveness
- reduced effort when trimming sails
- more consistent sail shape
- maximum mechanical efficiency in purchase systems
For racers chasing every percentage of performance, these small gains quickly add up.
Why Are They Called Zircon Blocks?
The name comes from zirconium, the metal element used to manufacture the ceramic bearings.
These industrial ceramic bearings are significantly harder and more resistant to compression than conventional stainless steel bearings. Because they deform less under load, they absorb less energy before they begin to roll. That translates directly into lower friction and faster response whenever the load on the rope changes.
Rather than simply fitting ceramic balls into an existing design, Harken engineered the entire bearing system around them, creating dedicated ceramic bearing races that maximise the efficiency of every rotation.
Where Do Zircon Blocks Sit in the Harken Range?
Harken has long been recognised for producing some of the finest sailing blocks available, with each range designed for a particular balance of performance, durability and value.
The Zircon range sits at the very top of Harken's compact block family.
While popular ranges such as Carbo Blocks continue to offer outstanding all-round performance for cruising and club racing, Zircon Blocks are designed for sailors who want the absolute lowest friction available from a compact Harken block.
That makes them particularly attractive for:
- performance dinghies
- sportsboats
- racing keelboats
- one-design classes
- high-performance cruising yachts
- any application where sail trim precision matters
If reducing friction is your priority, Zircon is the premium choice.
Three Sizes of Zircon Blocks, Eighteen Configurations
The Zircon family has been designed so the same bearing technology can be used throughout an entire purchase system.
The range includes three sheave sizes:
Sheave Size | Maximum Rope Diameter |
|---|---|
6mm | |
8mm | |
10mm |
Each size is available as:
- Single Block
- Single Block with Becket
- Double Block
- Double Block with Becket
- Triple Block
- Triple Block with Becket
This makes it easy to build complete low-friction control systems using matching blocks throughout your rig.
Harken Zircon Blocks Typical Applications
Harken Zircon Blocks are ideally suited to any control line where reducing friction improves trimming accuracy or makes adjustment easier.
Popular applications include:
- traveller controls
- vang systems
- cunninghams
- outhauls
- barber haulers
- backstay cascades
- mainsheet fine-tune systems
- custom purchase systems
Because the blocks are available in single, double and triple configurations, they can be combined to create a wide variety of compact mechanical advantage systems.
Are Harken Zircon Blocks Worth It?
Harken themselves acknowledge that Zircon Blocks aren't designed for every sailor.
They cost more than conventional ball bearing blocks, but they're also engineered to deliver the highest level of efficiency in Harken's compact block range. For sailors who appreciate the difference between a good control system and a truly exceptional one, the reduction in friction is immediately noticeable.
If you're building or upgrading a performance sailing yacht, they're one of the simplest ways to improve the feel and responsiveness of your rig.
Harken Zircon Blocks Available from Upffront
We're pleased to stock the majority of the Harken Zircon Block range for immediate dispatch, including all three sizes and the full selection of single, double and triple block configurations.
Whether you're replacing an individual block or designing a complete low-friction purchase system, you'll find the full range in our online store.
If you have any questions about Harken Zircon Blocks please feel free to contact us or click below to browse the complete range:
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Harken Zircon Blocks: The Lowest Friction Small Blocks from Harken