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Do You Need an Attitude Adjustment?


Captain Bill explains VACS- Vessel Attitude Control Systems - and how they control a boat's pitch, roll, and yaw.


Some of the auto driving features available today for boats are nothing short of amazing.


A good example can be found with automatic attitude adjusters. We know the importance of continuous trim adjustments when boating in choppy seas, but few of us are able to operate standard tabs and trims to effectively keep our boat in the best attitude to deliver the smoothest possible ride. As a result, we either live with a less than perfect ride, or we find ourselves continuously adjusting trim and tab settings.


When boating in smooth surface water you can adjust trim and/or tabs until your ride is good, and then only make periodic changes. Unfortunately, most boat trips encounter less than flat water and that necessitates continuous trim adjustments. From light chop waters to sea swells your ride is negatively affected. Enter the high tech ride adjusters.


While hull designs are improving every year, we are seeing new control technologies capable of operating faster and more accurately than manually adjusting appendages such as horizontal trim tabs. Such ride control systems are called VACS, or Vessel Attitude Control Systems. These utilize sensors and actuators to actively counteract the pitch and roll motions of a boat while underway, resulting in a smoother and more comfortable ride. Several companies such as Volvo Penta and Seakeeper have developed some amazing advances in ride control. Lets take a look at a VACS that can be added to almost any boat and see how the system works. Seakeeper provides such an example.


Seakeeper ride controllers are mounted to the transom below the waterline. Using inertia sensing hardware and software, the system calculates the boat’s motions on all three axes and instantly moves the in-water blades to counter pitch, roll, and yaw. The adjustments are performed at a remarkable 100 times per second to counter wave motions with no buttons to push. To do this, the Seakeeper system takes 1.000 measurements every second, and the controllers move at speeds up to 300 mm per second. This is certainly faster than a finger or thumb, even on a good day.


Seakeeper turns on and off with a simple keypad, or it can be interfaced with your electronic control screen. Actuators interface with an electronic three-axis sensing software module that calculates how the boat is ­behaving in terms of pitch, roll and yaw, then sends commands to the actuators to instantaneously control bow ­oscillation and roll. It can ­also learn a boat’s reaction to varying sea conditions and recall how to deliver the best ride when those conditions reappear.


One test drove a 22’ center console into three foot waves at 36 mph. With the Seakeeper system “off,” the bow pounded vertically into each wave. However, with the system “on,” vertical movement was significantly reduced, eliminating close to 50% of the vertical motion. In addition to a more comfortable and less tiring ride, this results in greater overall efficiency. Not to mention, the ever annoying tendencies to list (lean to port or starboard) were almost eliminated with Seakeeper on.


During turns, a deep-V craft will often lean more steeply than you would believe is necessary. Surprisingly, the Seakeeper system reduces the lean to a more comfortable angle.


As you might expect, there are VACS systems today that are designed for boats from 20 to 100 feet. Humphree and Zipwake offer a VACS system that employs vertical composite blades that change the hydrodynamic flow under the hull to modify lift factors as may be needed. Whether you should install a VACS on your boat depends on how often and how far you boat, and how long you plan to own it.


I believe auto stabilization systems are here to stay. What boater doesn’t want a smoother ride, better visibility and less effort to drive? As new models hit the market, we should certainly see more VACS being installed as OEM. #tips #quicktips


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