Unit 7 MKIV Hydraulic
Harken® MKIV Hydraulic Jib Reefing and Furling allow sails to be reefed, furled, or set with the touch of a button. Both tack and head have double swivels, improving sail shape when partially reefed. MKIV hydraulic furlers are used on cruisers and high-performance cruising yachts with headstays up to -170 rod or equivalent fiber stay.
Swivels on Units 4 and larger are lashed on with Spectra® line to evenly distribute loads and eliminate heavy shackles. Aerodynamic aluminum foils handle extreme reefing loads, while double foil grooves allow faster sail changes. Large-diameter Torlon® ball bearings in halyard and tack swivel minimize friction and don't require lubrication or isolating seals.
An over-the-turnbuckle system allows easy headstay adjustment. The lower toggle assembly fixes at 90-degree intervals to accept any chainplate direction. An optional hydraulic cylinder installed below the unit adjusts the headstay tension while luff tension remains constant. This prevents halyard and tack attachments from overloading when the headstay is adjusted.
The torque tube, motor, and gear housing are machined from tough and UV-resistant hardcoat-anodized aluminum. Hardened steel gears are permanently lubricated in an oil bath for minimal maintenance. A standard transmission engages the motor and manual gear drive. Compared to a diverter valve, this reduces mechanical friction and hydraulic pressure losses for efficient powered and manual operation. The motor has no case drain line, reducing the number of hoses plumbed on the boat from three to two. A worm gear drive prevents backwinding and unloads the hydraulic motor when reefed.
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Torlon® is a registered trademark of Solvay Advanced Polymers.
Spectra® is a registered trademark of Honeywell International, Inc.