No owner loves a boat with a bad attitude. Today, with the advent of adaptive vessel attitude control systems, there’s really no excuse for a boat that exhibits poor behavior, including excessive bow rise on acceleration, listing and heeling and pounding through wakes. A new generation of “smart trim tabs” employs sensors and digital technology to offer an unprecedented level of pitch, roll and yaw control with no input from the captain. The result is a boating experience that is significantly more comfortable, convenient and efficient, and is rapidly elevating the expectations of owners of boats up to about 50 feet in length.
“We think adaptive attitude control is a real game-changer for the industry,” says Victor Gonzalez, chief marketing officer at Sportsman Boats. Sportsman equips all of its models from 21 to 35 feet with Seakeeper Ride and has invested in slightly modifying its hulls to optimize Ride’s performance. “Think of all the adaptive systems we take for granted on new cars, from stability control to predictive cruise control. So many of our customers, especially new boaters, have such a learning curve with manual trim tabs. Now they just get on the throttles and go. And the systems really work. Ride makes our 21 feel like a 28.”
MANUAL TO AUTONOMOUS
Charles Bennett is credited with the invention of remote-adjustable marine trim tabs and in 1960 offered his idea to the public after founding Bennett Marine in Detroit. Lowering the tabs into the flow of water behind the boat created an area of high pressure that lifted the stern. Original Bennett trim tabs would look familiar to a modern boat owner, and modern control systems still function by generating lift at the transom.
What’s recent is technology that replaces manual control of the trim function with an autonomous system that utilizes input from a GPS receiver and, most critically, an inertial measurement unit (IMU). The GPS reports vessel speed, while the IMU measures and reports the force and rate of vessel movement in the axis of pitch, roll and yaw. As a reminder, pitch is the motion of the bow moving up and down. Roll is the rotation of the boat along an axis running from bow to stern. Yaw is rotation of a boat along a vertical axis, experienced as the bow pointing to port or starboard.
The IMU is not new technology. Apollo-era spacecraft were equipped with a stabilizing IMU system, but modern IMUs are much smaller and lighter and more precise. An IMU is part of the stability control system in automobiles and can measure five different axis of motion on a motorcycle to calibrate traction control and ABS. An IMU flips the screen in your smart phone and measures the motion of tracker video game controllers.
The IMU component of a vessel attitude control system uses an internal gyroscope and accelerometers to detect and measure pitch, roll and yaw forces at an incredible rate—up to 1,000 measurements per second. This data feeds an algorithm in the vessel trim control system that manufacturers claim can make up to 100 adjustments per second to the trim devices on the boat transom, working so quickly and making adjustments so subtle that those aboard don’t even feel them. There is no way even the most-experienced captain could make corresponding manual trim adjustments.
HOW THEY WORK
All of the attitude control devices on the market today enhance boat performance in the same way.
Pitch Control: At idle speed the devices automatically adjust to their maximum setting, to generate transom lift to improve time-to-plane and limit excessive bow rise that can block the captain’s view forward. Once the vessel is on plane the system is programmed to maintain the desired running angle. On an OEM installation this angle is determined by the boat builder, say 3 degrees of bow elevation above the boat’s resting state, an angle the builder has determined to be most efficient and offers ideal control and comfort. As the vessel encounters waves, swells or wakes, the system detects the change in boat pitch, ideally before captain and crew are even aware of the change, and adjusts the control devices to damp the pitch movement. The result is a reduction in pitch by as much as 70 percent.
It’s important to remember that these trim devices can only generate lift at the transom and lower the bow. For bow lift the captain must still rely on changing the prop thrust angle by adjusting the trim of an outboard or sterndrive. All of these systems have a manual over-ride function, so the captain can choose to temporarily trim the bow down for a prevailing sea state, such as before entering an inlet passage.
Roll Control: The roll control function seeks to keep the boat horizontal athwart by adjusting the port and starboard controls independently. This could counter vessel heel in a cross-wind, the rolling motion induced by a quartering sea, or on smaller vessels the movement of passengers in the boat or the unbalanced placement of gear. Of course most boats roll into a turn, and in this situation the control systems are programmed to permit enough roll to allow the boat to turn efficiently but not so much as to make passengers uncomfortable.
Yaw Control: This function is infrequent but it may come into play when the boat is in the wake of another vessel, for example, and the front side of the wake causes the bow to hunt. This may also occur in a following sea state. The control system will add lift to one side to counter the yaw motion.
AUTOMATIC OPTIONS
Boat builders and owners can now consider three different approaches to adaptive attitude control.
Self-Adjusting Trim Tabs: Bennett Marine and Lenco, two leaders in the traditional trim tab segment, offer automatic control systems. Bennett AutoTrim Pro ($660 to $700) was introduced in 2017 and is sold as a control system that can be mated to most Bennett electric or hydraulic tabs, and to other brands. This makes the Bennett system an affordable option and installation is easy on a boat already equipped with tabs. Complete kits are also offered. Lenco Pro Control Auto (from $2,550) was introduced in 2024 and won an Innovation Award at the 2024 IBEX marine trade exhibition. The system includes specific tabs (in three shape/size options) and electric actuators, a dash-mounted control keypad and the IMU hardware. For ease of retrofit, the actuators are designed to use the same mounting holes as previous Lenco units, and existing Lenco tabs may be used.
The traditional tabs used by Bennett and Lenco offer more control surface area than other designs, which the manufacturers claim results in superior vessel authority, especially in rough seas. They may also perform better in the aerated water flow created by step hulls. Both are easy to calibrate after installation.
Interceptors: Zipwake (from $3,160) introduced its innovative interceptor attitude control system in 2017, and it has become a very popular OEM feature on a wide variety of boats, with 50,000 units reportedly in use today. Based on a concept for commercial ships, the Zipwake system uses a horizontal interceptor blade located at the bottom of the transom to create lifting pressure. The blade moves up and down in the water flow, like a guillotine. A vessel can be equipped with two, four or even six interceptors, depending on vessel size. The interceptors are offered in two series and 25 sizes and shapes for vessels up to 100 feet LOA. Zipwake says the advantage of its interceptor system over traditional tabs is speed of actuation—up to five times faster than tabs. Zipwake further claims its interceptors produce less drag than tabs at speed and pinpoint the lift pressure directly under the transom.
Zipwake offers a dash-mounted control panel but the system can also be fully controlled through an MFD, eliminating dash clutter. Made of composite materials, Zipwake units do not require anodes and have an auto clean feature that prevents marine growth. The system is designed for easy DIY installation on a flat surface. Retrofitting to a boat equipped with tabs will require filling the old mounting holes in the transom. Calibration is not complicated, according to Zipwake. Humphree offers a similar interceptor system.
Rotary Control
The Seakeeper Ride system ($4,500 to $17,500) utilizes a concave surface controlled in a rotary fashion. As the control surface rotates, it engages the water flowing from below the boat. There are currently five Ride controls for boats up to 42 feet LOA. The system begins having trim authority at 10 mph and full stabilization benefits begin around 20 to 25 mph. Seakeeper claims its system actuates at even greater speed than Zipwake’s interceptors. Sea trial reports published by Seakeeper indicate a wide range of pitch and roll reduction, depending on boat model and sea condition. It can range from a 23 percent pitch reduction for a Boston Whaler 27 Challenger to 68 percent for a Sportsman Boats Open 262 CC. So, your results may vary. The system can be fully controlled through an MFD, but an optional keypad is offered. Each controller has a sacrificial anode. For a retrofit, Seakeeper recommends professional installation of its system, unless you are comfortable grinding a fiberglass surface and working with methyl methacrylate adhesive (MMA), which is used to secure the Ride controls to the transom. A detailed video on the Sportsman Boats website shows the installation process in an OEM setting.
It’s clear that adaptive vessel attitude control systems are much more than “smart trim tabs.” Each offers self-adjusting control that simply can’t be replicated by manual trim tabs, an evolution of the concept introduced 50 years ago by Charles Bennett, that offers real advantages in comfort, performance and economy.
February 2025
