How to Tackle a Trim System

Enjoy increased control and diminished drag with a system that uses blades instead of full tabs.

The Zipwake Dynamic Trim System operates like trim tabs but provides greater control with less drag than conventional systems. The interrupters are blades that extend a little more than an inch out of their housing when fully deployed, instead of the six inches trim tabs go down into the water. They fully extend in one and a half seconds and can be controlled manually or set to automatically achieve the desired result. When turned to auto, they reduce both roll and pitch without driver input, even during turns.

The project includes three primary parts — interrupters, distribution unit and control panel — and involves drilling quite a few holes in the hull, so inexperienced do-it-yourselfers may want to take a pass. Anyone with doubts should leave this one to the pros or at least work with someone who has a strong background in working with hulls. That said, the installation is straightforward and can be done in a few hours.

Because of its modular design, the Zipwake system (zipwake.com) can fit on a wide range of boats, from 20-somethings all the way to yachts. Smaller boats need one pair of interrupters; larger boats can take up to three per side. Owners can control up to six (three pairs) with one distribution unit that ties into the boat’s NMEA 2000 backbone, which is what the other electronics tie into.

The first step might be the most important: placing the interrupters, which come in different sizes. For maximum effect, place them as far outward on the transom as possible. If the hull has spray rails or reverse chines, a limited amount of overlap over the gap is OK. To install more than one on each side, like on my boat, start with the outer ones first. If you have multiple outboards or sterndrives, space the interrupters closest to the outside of the transom like this: outside the propeller’s diameter plus an additional distance of the prop diameter divided by four. The interrupter toward the keel should be inboard of the prop’s diameter plus the diameter width halved.

Zipwake can be installed on boats with a negative-angle transom, which allows a sterndrive or outboard to be trimmed at a negative angle for quicker planing. My boat has inboard engines, so I didn’t have to jump through that hoop. Interrupters should be mounted on a flat area. Once I found the spot, I taped the supplied template in position (1).

I drilled 1/8-inch pilot holes (2), removed the template and drilled 3/16-inch mounting holes. Folks who want to run the power cable behind the interrupter, which is a tidier option, will have to drill a 3/4-inch hole below the waterline. I elected to run the cable above the waterline, so I didn’t have to drill the hole, but if you’re going to mount the cable concealed behind the unit, now’s the time to drill a hole with a hole saw with a 3/4-inch bit.

Since I ran the power cable above the waterline, I didn’t have to remove the servo unit on the mounting plate, but folks using the concealed cable method should remove the servo and pop out the round disk to create a hole on the back of the plate. The next step is incredibly important. Apply the Sika Sikaflex-291 Fast Cure Adhesive/Sealant liberally to each hole in the hull and on the mounting plate. I held the mounting plate close to the transom, inserted the screws through the holes, lined them up with ones I’d drilled and used a T30 bit on a power drill to screw them into the holes. Then I mounted the cover onto the mounting plate (3).

To install the power cord, I measured to a place four inches above the waterline where I wanted to drill the hole. The distance above the waterline doesn’t matter, because there is a wire cover that can be cut with a hacksaw for a custom fit, but the covers on the left and right should match for aesthetic reasons. After drilling a 1/8-inch pilot hole, I used a 3/4-inch hole saw to cut the hole before cleaning the hole and slathering Sika sealant around it and onto the screw part of the through-hull fitting near where it presses against the inside of the hull. It’s above the waterline, but I sealed it well, because water can still enter the transom and ruin it. I fed the fitting through the hole and attached the nut on the other side. If the boat will be kept in the water, paint the area with antifouling paint.

I installed the distribution unit inside on the hull — high enough to always be above any bilge water — ran a cable to the dash and ran the power cable from the unit to the battery (4). Be sure to place a 15-amp fuse in between and plug the interrupter cables into the unit.

Using the supplied template, I installed the controller at the helm. (Find a good location on the dash that’s at least 20 inches away from a compass, to avoid interference.) I taped the template in place and drilled 1/8-inch pilot holes. I drilled the three-inch center hole (5), attached the cable from the distribution unit and screwed down the controller (6) — after applying more Sika sealant. Once everything was hooked up, I tried it on land to make sure everything was working properly.

Zipwake is incredibly easy to use. When in manual mode, slightly twist the ring around controller wheel to make the boat lean in the desired direction and use the mouse wheel to raise and lower the bow. In auto, just press the button and it does everything for you. It’s incredibly responsive and the panel always lets you know what’s being deployed.

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