Linear drive/hydraulic packages now come in a
single unit with a ram to attach to your quadrant or tiller and a built in hydraulic
pump and reservoir all in one unit. You hook up your DC feed wires to the unit and the
motor drives the hydraulic ram that pushes/pulls on the
rudder quadrant/tiller. There are many versions built by many of the major
autopilot companies. And you can normally mix and match the various units with various
autopilot computers.
- - Autopilots now come with a whole menu of fancy features most of which you will never use more than once. What you do use most often is the
compass heading mode which simply holds the
boat on a heading you select. For this feature to be best utilized you need a "rate gyro fluxgate" rather than a simple "fluxgate". Fluxgates are solid state without an internal "floating compass". As you start a turn to a new heading every fluxgate/wet
compass will start to turn in the opposite direction. The rate gyro
fluxgate senses this and prevents the heading information from feeding this "opposite direction" information to the autopilot computer. That's the theory, anyway.
- - The feature that hooks into your
wind direction
instruments is worse than useless in most cases. The little
wind direction vane at the top of the
mast is normally swinging and moving all over the place due to wind variations and
mast swings. If you want constant wind angle sailing buy a real
windvane for your transom.
- - The "navigation" feature is nice but can really get you in trouble as it will steer the
boat according to the
route and
GPS information you have entered in your
navigation system computer. The autopilot will attempt to constantly keep you on your plotted course line which with moderate seas and varying wind will result in constant autopilot "grinding" to turn the boat. But the big "brown you pants" moment with the
GPS navigation mode occurs when you have entered double waypoints on top of each other. At the waypoint the autopilot will attempt to turn to the hidden waypoint usually resulting in a 180 degree turn just when you don't expect it. Talk about a Mexican circus as
sails, booms and crew dash about trying to figure out what is happening. If you are entering a harbor when this happens, it really gets exciting/terrifying. It takes supreme discipline and carefully
route entry procedures to prevent this.
- - So you end up with the "compass mode" being the most used. Try to find a reputable unit with solid
history of "just working" and has a good "rate gyro"
fluxgate option. I use the
Simrad Robertson series units primarily because of their reputation as solid, just keep working, units.