Water Drive - SailNet Community
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post #1 of 1 Old 12-05-1999 Thread Starter
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Water Drive

Autopilots are under constant use on long passages, consuming considerable power and requiring frequent engine running to recharge the batteries. Harnessing the energy of moving water in the wake of a sailing vessel is not a new idea, but The Water Drive is unique. It uses hydraulics to drive the autopilot, thus relieving one of the largest electrical draws offshore, and generates 12-volt power at the same time.

The Water Drive employs a small turbine propeller deployed from the stern of the boat on a length of rope. The propeller spins in the water causing this rope to rotate, turning a hydraulic pump and a generator. The hydraulic pump, in turn, drives a ram connected to the quadrant of the rudder, which then steers the vessel. The result is that the existing autopilot provides only a tiny steering signal and no longer consumes power from the battery banks to steer the boat. Instead, the grunt work is left to the Water Drive. At the same time the built in generator automatically charges the batteries, whether or not the steering function is in use. Water Drive comes with a unique two-position switch to select between "Battery Powered" and "Water Powered." In the Battery Power position, the vessel's existing autopilot works normally with energy fed from the ship's batteries. Switching the unit to Water Powered activates the hydraulic pump and uses energy from water flowing past the vessel.

Owner installation, maintenance and overhaul is encouraged, an important consideration when faced with remote destinations where qualified service may be hard to come by or nonexistent. The hydraulic unit is lashed to the aft rail and a roll of flexible tubing is run through the deck to the hydraulic ram at the rudder quadrant. The selector switch is inserted in the existing autopilot's output cable and then to its motor or actuator. Tubing and wires are included. Ordinary motor oil is used to drive the hydraulic unit, alleviating the headaches of purging a straight hydraulic fluid system of air.

The Water Drive is also appealing to long distance cruisers because it lightens the load on expensive autopilot equipment. Autopilots driven by electric motors have limited lifespans and failure after 800-1,200 hours is not uncommon. By taking the load off the conventional autopilot, the Water Drive extends this life expectancy. Even if the autopilot's drive unit does fail, the Water Drive will still be able to steer the boat.

The most apparent drawback to the system is that unless the vessel is underway, electricity will not be produced. Additionally the propeller is vulnerable to collisions with underwater objects and may be fouled by heavy seaweed or other flotsam. It's also a great lure for large fish. There are six different models for vessels 32 to 80 feet in length. Prices start at $1,899 and go to $5,581.

A three-year warranty covers defects in materials or workmanship. If energy conservation on extended voyages are on your sailing itinerary, the WaterDrive may be a welcome addition to your electrical and autopilot systems.


Mark Matthews is offline  
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