Improve Performance with Trim Tabs

September 21, 2007
Trim tabs are easy to install and will improve the performance of any boat by allowing the helmsman – or an automatic trim-control system – to tweak the hydrodynamics.

Most boats come with trim tabs either as standard or optional equipment these days, but that wasn’t always the case. Some builders used to believe that hanging a pair of tabs on the back of their boats amounted to an admission that the boats had some sort of inherent problem that needed correction. Conventional wisdom held that “good” boats didn’t need tabs.

That meant, of course, that a whole bunch of consumers took home boats that ran on their side when all the kids sat on the port gunwale, or squatted when a cooler full of fish was shoved back against the transom on the way home from a successful day offshore. Fortunately, most builders have wised up because, as we all know, all boats benefit from trim tabs.

Let’s review why. Trim tabs work like ailerons and elevators on an airplane, providing lift when and where you need it. Tabs are usually a pair of stainless-steel planes mounted on the boat’s transom that are raised or lowered by a hydraulic or electric ram. The size of the tab, the angle of deflection and the boat’s speed combine to create lift at the stern.


Plane and Simple

This helps in a wide variety of situations. When getting the boat on plane, for instance, lowered tabs create substantial lift to raise the stern faster, so you’re off and running quicker. That is often a big concern in small boats like flats skiffs in situations where you have to jump on plane in a short distance. Alternatively, bolt-on cavitation-plate extensions (the wing-like devices that attach to your outboard’s lower unit) provide some of the same lift that a full set of tabs does, but at a much lower cost. Cavitation-plate extensions offer the benefit of placing lift in the farthest aft spot possible, so that the greatest lift per square inch of tab surface is achieved.

Tabs enable you to correct for unbalanced loads and help keep the boat on plane at slower speeds, a major benefit when you’re offshore and trying to make headway through rough seas. Normally, you have to slow down to keep from pounding, but when you do so, the boat wants to fall off plane as the stern settles. Tabs help the boat run level at slower speeds, which also helps maintain unobstructed visibility. It’s dangerous to mush along at slow speeds with your bow high in the air. A level running attitude lets you keep a lookout in all directions.

You can also run faster into a chop in an outboard boat by experimenting with a combination of trim settings involving both the tabs and the engine outdrives. By setting the tabs down somewhat, and then trimming the outdrives up slightly, you can make the hull ride perfectly level, and it’s amazing how much faster you can run in a short chop after trying different combinations of the two trim adjustments. And when the outboard’s props are providing thrust parallel to the water’s surface, efficiency is enhanced, too.


Automatic Tabs

Like all boating systems, however, trim tabs are growing increasingly sophisticated. Most of the major trim-tab companies now offer features like LED indicators to let you know the position of the tabs at any given time with a quick glance. Another useful feature is auto-retraction, which has saved many a boat owner a few bucks! When you shut the engine off, the tabs are automatically brought back to the fully upright position. Lots of tabs get broken every season when owners put their boats onto a bunk trailer without raising the tabs, or when a forklift operator picks your boat up to return it to the rack with the tabs down. These problems are eliminated with auto-retraction.

Bennett Marine has raised the technology bar substantially by introducing its Auto Tab Control, or ATC, a system that promises to make tab use easier and more foolproof than ever. “The main benefit of Auto Tab Control is simply that it’s automatic,” said Tom McGow, Bennett’s Director of Client Services. “You aren’t tied to adjusting the tabs all the time, so you can concentrate on more important things, such as navigation.”

The ATC system works with an attitude sensor that is remotely mounted in the boat and coupled to a microprocessor (CPU). The system is set up initially by running the boat in the trim position you feel is optimum. The ATC then “remembers” that setting and automatically keeps the boat running at the desired attitude.


The sensor samples the boat’s attitude at high speeds and feeds that data to the CPU, which then takes a rolling average of the boat’s attitude movements. The CPU is programmed not to react to every wave the boat encounters, but reacts instead to slower changes in trim. That way the tabs don’t constantly adjust every time you hit a wave, but instead react to more long-term movements, such as those caused by load shifting.

“The ATC knows the optimum attitude for the boat. As the boat deviates from that attitude, the ATC automatically corrects it,” McGow explained. “It’s a very sophisticated system. It constantly adapts the sensitivity and response to maintain a better constant attitude than the helmsman can accomplish manually.”

Similar to automotive cruise control, the ATC can be easily overridden. The CPU is connected directly to the tab system’s wiring harness and comes with its own operating keypad, which allows you to turn it on or off. But the ATC can also be disengaged simply by pushing one of the manual tab switches. This ensures that you have instant tab response in case you need it in a hurry, such as when running through a breaking inlet.


Electric Tabs

Other trim-tab companies offer different innovations. Lenco Marine occupies a somewhat unique niche in the market because its tabs are electric, not hydraulic. The rams extend and retract as a ballscrew, driven by an electric motor housed in the tab casing, spins on 12 ball bearings at both ends of its stroke. The stainless-steel ram won’t flex, even under extreme conditions, and a nitrile O-ring and tetra seal make it completely waterproof. And because the ballscrew locks into position in machine-cut brass drive gears, the ram won’t drift or pull down, even when backing down with the tab extended.

Lenco’s Troll’n Tabs combine the benefits of electric-ram trim tabs with electric trolling motors in one compact package.|

Lenco may be best known for its Troll’n Tabs, though. These combine stainless-steel trim planes with high-thrust electric trolling motors. This system puts the motors in an optimum location where they are completely out of the way – plus they are permanently attached. A lightweight hand control clips to your belt, giving you full control from anywhere in the boat. The motors develop 164 pounds of thrust, and feature independent forward and reverse thrust so you can back up or even spin the boat in its own length.

Most tab companies also offer high-speed tabs for you speed freaks out there who like to go 60-plus mph on the water. These tabs usually feature small rudder fins on the bottom of the planes for stability, and many have dual rams to handle the extra pressure.

The point is that there’s a tab for virtually every boat. Most new boats come with them, but if you have a boat without tabs, it’s usually not a problem to add them. If you’ve got them, experiment to see if you can optimize your boat’s performance and economy. If you don’t have them, get a set and see what you’ve been missing. Compared to the overall price of a boat these days, trim tabs are a bargain. They’ll help you discover a whole new world of performance, plus you won’t have to yell at your passengers when they move from one side of the boat to another. That might make it easier to find a fishing partner each weekend!

Trim Tab Manufacturers Bennett Marine Deerfield Beach, FL (954) 427-1400 www.bennetttrimtabs.comLenco Marine Stuart, FL (561) 288-2662 www.lencomarine.comDoel-Fin/Davis Instruments Hayward, CA (510) 732-9229 [email protected] ¿ ¿ ¿ ¿ ¿ Hydro-Shield Edgewater, FL (800) 218-0890 [email protected]Trim Master Marine St. Charles, MO (888) 874-6822 www.trimmaster.netInsta-Trim/Boat Leveler St. Louis, MO (314) 385-7470



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