29 mm Zircon Block

Harken 29 mm Zircon Block

The Harken 29 mm Zircon Block expands the Zircon line to eighteen models, adding six configurations with 29 mm sheave diameters suited to control lines where multi-part purchases are required. Zircon is not an all-purpose alternative — no block is — but these smaller sizes make Zircon the right choice when instant, precise response matters most. Whether easing a 24:1 Cunningham rigged under the deck or letting the jib lead forward for more power through chop, this block delivers immediate feedback.

At the core of Zircon performance are industrial ceramic ball bearings mounted inside caged races. The cages keep bearings separated so they cannot bunch up, contact each other, or impede rotation. The result is a remarkably free-running block with minimal energy lost to friction — give an unrigged Zircon a firm spin and it will continue spinning for a remarkably long time. Zircon ceramic bearings are more than 700% stronger in compression than stainless bearings of the same size, so they remain smooth and resist deformation within recommended load limits. Critically, they absorb far less energy before beginning to roll, which becomes evident when easing a sheet or multi-part control line in light air: the sailor can react to very slight fluctuations in line load. When applied expertly, that means better sail shape and more boat speed.

Key Features

• Industrial ceramic ball bearings in caged races for ultra-low friction and free-running sheave rotation
• Ceramic bearings more than 700% stronger in compression than stainless equivalents
• 29 mm (1 1/8 in) sheave diameter optimized for multi-part control line purchases
• Maximum working load of 80 kg (175 lb); breaking load of 240 kg (525 lb)
• Accepts line up to 6 mm (1/4 in) diameter
• Compact 43 mm (1 11/16 in) length and ultralight 10.5 g (0.37 oz) weight
• Immediate response in light air enables fine-tuned sail shape adjustments
• Part of an 18-model Zircon range for small boat and control line applications