Autopilot in a sailing boat

When choosing an autopilot for a sailing boat you first have to consider the type of sailing you want to do. Next thing is to select a drive unit that will work with your existing steering system. You have to take into account the length of the boat and the torque you need to move the rudder. The last thing has to be calculated based on the dimensions of the rudder. Allow us to help you with that.

For day cruising on a smaller sailing boat in not too heavy sea conditions you basically have two options dependent on you existing steering system. For a sailing boat with tiller an inexpensive tiller pilot can be a good choice. In the same way if your sailing boat is wheel steered a wheel pilot can be used. On a wheel pilot a motor is mounted to the outside of your steering pedestal and a belt attaches to a hub mounted immediately forward of the wheel. For day cruising and in not to heavy sea conditions they can both handle the boat in a satisfactory way. However for more demanding use in any weather they are usually not strong enough. The exposed placement of these drive units also makes them prone to damage. It should be noted that we do not sell these two types of drive units for the simple reason that many customers are not satisfied with them.

If you want to use your autopilot in more demanding weather condition, and sooner or later you will want that, you have to install a stronger inboard drive unit. The most common are linear drives directly connected to the rudder quadrant which can be either hydraulic or mechanical. For large sailing vessels a hydraulic linear drive can be the only possible alternative. For smaller boats when space is tight the size of the ram can rule them out. If this is the case and if your boat is less then 38 feet we recommend to use the Saildrive RS. This linear drive kit can be fitted into very small spaces which makes it ideal for the smaller to mid sized modern yachts which have limited space to fit drive units. A nice feature is that the rudder feed-back unit plugs neatly into the drive housing, taking very little extra space and making installation straightforward. The  drive unit is connected directly to the steering quadrant by a cable as shown in the picture to the right.

ML40+For larger sailing vessels the only alternative is an hydraulic linear drive. They consists of a ram, an electrical pump and an electrical by-pass valve. For the ML40Plus to the left all this is combined in one compact unit. The ram is connected directly to the steering quadrant. In auto mode the autopilot will lock the by-pass valve and take command of the rudder. In stand-by mode the by-pass valve will open to allow steering the boat in the normal way.

Please allow us to make a calculation for your needs of torque if you should want to install this type of drive unit.

As an alternative to linear drives a rotary drive can be a good choice for many boats. They are usually mounted inside the steering pedestal. With this drive unit a chain runs from the sprocket of the drive unit up to a sprocket affixed just forward the existing chain sprocket inside for example the pedestal. Rotary drive autopilots use your existing cable steering system to steer the boat. This poses an advantage in that the drive itself isn’t subjected to extremely high loads like with a linear drive. With a rotary drive autopilot however, if you lose your normal steering you will also lose the ability to steer using your autopilot as well. Note that this is not the case with the two systems of linear drives we have described earlier. They are independent of you existing steering system which can be a safety aspect.

The primary benefit of an autopilot in a sailing boat is convenience. Instead of handling the steering all the time, you’ll be able to tweak the sails and control your navigation. If you’re a couple out cruising, the benefits extend beyond just convenience. This third crew member, the autopilot, helps to reduce the fatigue that can result from spending countless hours at the helm. A clear mind free from exhaustion allows you to fully evaluate impending situations at sea and render proper judgments. An autopilot is such an important piece of safety equipment for long distance cruising that it’s worthwhile to invest in installing one.

See also this article: AP47S installed in a Maxi95 for information on Saildrive RS

See also this article: AP47SL used for around the world sailing for information on ML40Plus

See also this article: AP55 and rotary drive in tug boat for information on rotary drive Mech1