When the boat is the issue

 

Simrad® autopilots are in use across a wide range of boats from displacement boats with deep V configurations to high-speed vessels. But such a variety also means that the autopilot systems need to be able to cater for an equally wide range of boat performances. So, while some boats are naturally directionally stable and require very little assistance, others need more frequent heading alterations.

 

How much assistance will your boat need from the autopilot, and how do you establish this?

“Establishing how easy it is to hand steer the vessel will reveal how much effort the autopilot will have to put in to maintain a heading. It’s particularly useful to assess this by hand if you’ve had trouble tuning the system to work accurately across a range of speeds,” says Simrad product manager Eirik Hovland. “Going back to basics is the key here.”

“Different boats will require different amounts of assistance, depending on several design characteristics. Some boats will require more steering input than others. For example, lightweight RIBs with flat bottomed hulls may be less directionally stable in say windy conditions than a heavy displacement motorboat”.

“One of the key issues here is that when you’re handling the boat manually, you may be anticipating the required corrections. Yet, the autopilot can only correct for an offset; it usually can’t predict in the way that a human can.”

 

“Typically a V-hull is more stable than a full planing hull,” he continues. “But there are other factors that can affect how a boat behaves and the demands it puts on an autopilot”.

 

“One of the test boats that we have here in Egersund fishtails and steers poorly at slow speed. No matter how well you tune the autopilot, it will oscillate around the heading. That’s partly because of the hull design but also because it has a sterndrive which in this case tends to make matters worse”.

“If you have a single shaft drive and a centreline rudder on a V-hull or a keelboat, then you’re heading is going to be much more stable and easier to tune.”

 

The physical constraints of the steering system can also influence the effectiveness of an autopilot. Understanding where potential problems are starts with knowing whether you have a mechanical or hydraulic steering system. But how do you know which you have?

 

“If you’re not able to see behind the scenes, it is still relatively easy to identify what steering system you have,” explains Simrad product expert Tonnes Haavarsen. “When the autopilot is switched on if the wheel moves, you have a mechanical system. If it doesn’t you most likely have a hydraulic system.

“Either of these methods can develop issues that may at first make it look like there’s a problem with the pilot, but where the issue lies with slack in the steering system.

 

“For mechanical drives, it’s important to ensure that there is no play in the connections and the mountings, while the air in a hydraulic system could cause issues for this system. In both cases, you need to iron out these problems as no amount of tweaking of the pilot will compensate for this.”

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Eirik Hovland

Product Manager

Based in Egersund, Norway he is an experienced sailor and motor boater with expertise in both recreational and commercial autopilots. His work with autopilots began as a software developer before moving on to become a system engineer where a large part of his work involved the validation of autopilot systems.
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Tonnes Haavarsen

Product Expert

Having started in the business back in 1978 he has extensive knowledge of autopilot systems and has seen considerable development in this field. Also based in Norway, his work focusses mainly on the technical side for a wide range of recreational and commercial autopilots.