Interceptors have been growing in popularity, but how do they stack up against traditional trim tabs?
Trim tabs have been around forever, but in recent years many boat owners have opted for interceptors. Which begs the question, what exactly are interceptors, and why would someone trade in their trusty trim tabs for them? Are they better at leveling out the ride? Will they make yotheur boat run better than it does right now?
We all know that trim tabs are horizontal metal plates that swing down from the back of the transom, creating an upward force (lift) to raise the aft end of the boat while pushing down the bow. Tabs can be deployed unevenly between port and starboard to help a boat run level despite an uneven weight load or listing. In doing so, however, they also increase a boat's drag through the water.
Interceptors, on the other hand, are blades that sit inside a thin housing mounted to the edge of the transom and deploy vertically, pushing straight down just below the bottom of the boat. Like trim tabs, as interceptors lower below the edge of the boat, they create lift. Multiple units can be mounted along a transom to increase the amount of lift, whereas in the case of trim tabs, larger plates are commonly used for larger boats.
ADVANTAGES AND DISADVANTAGES
Since interceptors are smaller than trim tabs (extending around an inch versus six inches or so for the average trim tab) they generate significantly less drag. This makes them more efficient, and much faster than trim tabs to deploy and adjust, by as much as 4.5 to 6.5 seconds.
Interceptors also have an edge from an angler's point of view. If you've ever been fighting a hot tuna and it suddenly darted under the back of the boat and cut you off on the trim tabs, you know what I'm talking about. Plenty of fish have chaffed lines off against the tabs that stick off the transom with sharp metal edges. Interceptors eliminate those metal plates. The way tabs stick out can also be problematic in difficult docking conditions as they can catch a piling. Tabs also get in the way when swimmers try to climb back in the boat. No people, these are not steps!
There are, however, a couple of downsides to Interceptors. Boats that travel at more than 60 mph commonly can't use interceptors because the force of waterflow against the blades at such speeds can cause damage. Boats larger than 60 feet in length also have issue with mass-produced interceptor systems, because they just aren't built in large enough sizes (though there are some custom options out there). Finally, interceptors tend to cost more than traditional trim tabs. Depending on the system, they may be twice the cost.
Disadvantages aside, there are some interceptor systems that go well beyond the normal functions of tabs and blades, via dynamic trim control. These systems can be set to automatically adjust the blades to mitigate roll and pitch as the boat moves through the water. This is only possible because the interceptors can move more quickly than tabs. And these systems require some serious tech. Zipwakes dynamic trim control systems, for example, integrate gyroscopic and accelerometer sensors, GPS, a control head, and a distribution unit that controls the blade's action. These advanced systems are more expensive than the alternative but price varies from boat to boat, as the beam between chines is what dictates sizing of the system.
On the flip side of the equation, we've ridden on several Zipwakes-equipped boats and there's a significant improvement in comfort levels with vastly reduced rocking and rolling. Does the boat remain as rock-steady as one fitted with a full-blown Seakeeper gyroscopic stabilization system? No. However, the system's cost is also a small fraction of a gyro, the complexity of installation is a fraction of a gyro system, it takes up a way less space, and it can be used on boats that aren't large enough for a gyro. Additionally, dynamic trim control increases a boat's cruising fuel efficiency. Zipwakes' claim, which we haven't independently verified, is to the tune of 10 to 12 percent.
But that brings us back to our initial question... which is better, trim tabs or interceptors? As usual, much of the argument boils right down to how much you're willing to spend and what you expect to get for your money. There's no question that tried-and-true trim tab systems help a boat run better, and their cost is minimal. There's also no question that at the opposite end of the spectrum interceptor systems - especially those with dynamic trim control - will help a boat run a whole lot better. But, they also cost a whole lot more. Deciding which system your boat needs all comes down to you, and your wallet.