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Harken 12:1 GP Catamaran Mainsheet System

Item #


Product Description

Harken 12:1 GP Catamaran Mainsheet System

Harken’s Grand-Prix mainsheet systems are critically important options for high-performance beachcats like the Nacra 17 or F18s. The high-efficiency blocks making up these systems feature insert-molded ceramic bearings that almost eliminate rolling resistance, greatly improving power transfer to the crew for easy, precise trimming. These compact blocks feature hardcoat-anodized sideplates that envelop composite sheaves for easy disassembly/reassembly. The system profile is the lowest on the market by far. High-performance fairing increases aerodynamic flow and protects the crew and blocks from impact damage. The lower block features a built-in cam arm that infinitely adjusts by loosening two (2) screws with a hex key. A single ratchet sheave in the bottom block ensures release is controlled and smooth. A snap shackle attaches the block to the boom. A swivel shackle attaches to the traveler.

Note: the GP mainsheet system is delivered as a 12:1 mainsheet system, but can be easily reconfigured as a 10:1 or an 11:1 to align with wind or crew preference. All necessary parts and reeving instructions are included. Line not included.


  • Sheave Ø: 2 5/16 in. (59 mm)

  • Pin-to-pin length: 8 13/16 in. (224 mm)

  • Weight: 36.6 oz. (1039 g)

  • Maximum line Ø: 5/16 in. (8 mm)

  • Maximum working load: 1200 lbs. (545 kg)

  • Breaking load: 3600 lbs. (1636 kg)