09 Sep New Stabilizers for Starr
2025 update: Two years and 15,000nm after installation, the Humphree fin stabilizers have proven to be a disaster. The clunking noise and vibration has not been resolved. The main seal has failed at half its expected lifetime, allowing seawater to enter the boat. Factory service is slow and unreliable and third party service doesn’t seem to exist. See www.humphreestabilizers.com for more information.
A year ago we tore out Starr’s original Naiad hydraulic stabilizers and replaced them with a brand new set of Humphree electric stabilizers. This was a big project!
The primary goal was adding stabilization at rest, a feature that would make cruising Hawaii dramatically more comfortable. Naiad offers this as an option, but their system requires hardware that we didn’t have space for, needs generator power, and isn’t particularly quiet. The Humphree fins, by contrast, operate at 24VDC off the house batteries. We were told they’re nearly silent.
With the new fins on order, we set about removing the Naiads. Frustrated by the pace of the boatyard, Don and I broke apart the heavy, greasy cast metal fin mounting hardware. We pulled out miles of wiring and hydraulic hose and removed the hydraulic tank and PTO. The boatyard seemed a little surprised by our pace of disassembly! Unfortunately it all happened so fast that we neglected to take photos!
With the old stabilizers gone, we started thinking about the new installation. We had a number of puzzles to solve:
- Add alternator capacity to account for increased electrical consumption
- Wire new servos and control systems
- Reconfigure the stabilizer mounting location for the new actuators and fins
The Fiberglass Phase:
Physically mounting the new Humphree fins is quite different from the old Naiads. The picture below shows the size difference. The new cutout is about 18 inches across!
First we had to create a physical “pad” for the new actuators (servos). The specs for this are demanding: not less than 84mm thick (3.307 inches), not greater than 86mm thick (3.386 inches), and the inside and outside planes have to be exactly parallel. This phase of the project was slower and messier than expected. Lots of grinding, lots of dust.
Naiads removed and glass work beginning
Inside the starboard stabilizer alcove, with no stabilizer
First look at the new servos…will they fit?
Once the layup was complete, we had to cut new holes. Doug Janes at Pacific Yacht Management created a jig to make this easier. Doug is a prince! He just celebrated his 80th birthday and has at least 200 years of knowledge of working on boats. He’s thoughtful, careful, and has built a tool to make nearly any difficult boatyard task easier. He’s an extraordinary problem solver, generous with his knowledge, kind–a true joy to work with. I wish I had a fraction of Doug’s knowledge and ability. Thank you for helping us with this and so many other projects over the years Doug!
Cutting through 85mm of vacuum-bagged fiberglass was dusty and challenging. The $200 diamond-encrusted router bits built for bow thruster installations proved woefully insufficient. Boeing surplus composite bits did the trick.
When the first router bits burned up, we tried hole saws and a sawzall. They made lots of dust, but little progress!
With the right bits, cutting was “easy” for 79-year-young Doug!
Doug Janes measuring twice. Looking good!
With the holes cut, we dry fit the servos and their mounting bolts.
This sounds easy, but maneuvering 200+ pound servos into tiny stabilizer alcoves was a project unto itself!
Lifting the servos onto the swim step with a forklift…the easy part!
The starboard side was easy with the help of a new lifting eye overhead and a chainfall
The port side, with no room overhead, was harder, but we worked from inside and outside to get it done!
With the servos in place, we sealed the outside with 5200 (tubes and tubes of 5200) and filled the cavity between the hull and the servo with chockfast.
Fred Madrid, Nordlund’s fiberglass lead. Fred was awesome!
Then we bolted the fins on and torqued them to spec. Ready to launch!
We returned to SBMC with fins physically installed but not connected electrically. Over the next few weeks, we tackled the remainder of the installation.
The Electrical Phase:
Each servo can pull more than 100 amps of power at 24VDC. With a 100 foot round trip distance from the battery bank to each servo, we had to use 4/0 electrical cable, which is heavy and stiff. After some trial and error, we figured out a path from the battery bank to the tank room amidships, then out to each servo. We installed a circuit breaker at the battery bank for each servo, (so they can be shut down independently if needed) and pulled two hundred feet of cable through the bilge.
The control wiring was simpler. The Humphree control panel fit in the abandoned Naiad hole at the helm. We re-terminated the Naiad control cable with the correct Deutsch connectors for the Humphree system and avoided having to pull more cable from the bilge to the bridge. The control wiring in the bilge was remarkably simple: one wire from each servo to the control box and 24VDC to the control box. Overall, fewer components and far less cabling than the Naiads.
With the system wired up, it was time to turn it on. Humphree fins can rotate through 360 degrees, and in the process, they can hit a dock, so we cautiously powered up only the fin away from the dock. We were instantly impressed by how quickly and quietly the fins are actuated (click to play):
Generating the Electricity:
We still had one problem: the single 175A, 24V alternator on Starr seemed insufficient to cope with the additional electrical demand the fins might require. We decided to install a second, identical alternator where the existing belt-driven raw water pump was, and find a gear driven raw water pump to go on the PTO pad abandoned by the old Naiad hydraulic system. Sounds easy, right?
We wrongly assumed that someone else with a Cummins 855 had already done something similar. We quickly realized nobody knew how to do what we were doing. We ordered a number of Cummins alternator brackets, but none was exactly correct for our configuration. Thankfully, Aaron at S3 Maritime modified the Cummins hardware to make it work.
A rebuilt spare 175A, 24V Leece Neville alternator pressed back into service
Nobody had an off-the-shelf gear-driven raw water pump for a Cummins 855. Several people suggested using an electric pump, but that brought a whole bunch of additional failure modes we were uncomfortable with. After comparing pump output curves, port configurations, and mounting configurations, we settled on a Sherwood pump sold for John Deere engines. To make it work on the Cummins, we just needed an 8-to-11-spline adapter for the shaft and inlet and outlet elbows. Don found an off-the shelf spline adapter manufactured for John Deere commercial mowers, and Aaron modified a pair of Cummins elbows to work with the flange-mount ports on the Sherwood pump.
Perhaps the only gear-driven raw water pump on a Cummins 855 anywhere!
Crossing the Pacific:
A few days after completing the installation, we departed Seattle for Hawaii. Nothing like a November Pacific crossing to iron out any problems with the new charging system, cooling system, and stabilization system! Happily, it all worked.
After a winter in Hawaii, we’ve had quite a bit of time to test out the stabilizers. Underway, they function very similarly to the Naiads. At rest, they’re awesome. It’s amazing to look over the rail and see them flapping around wildly, almost like a whale tail, stabilizing the boat.
They really work. Pushing a button is a whole lot easier than deploying the flopper stoppers. We can run them for many hours on the batteries alone. The actual electrical consumption varies dramatically with sea state. In a calm anchorage, they use essentially no power; anchored off the surfers at Diamond Head, they probably use 100+ amps every hour. They use much less power underway than at rest. In the tropics, we run a generator overnight for air conditioning, so the electric at-rest function has added no generator run time. They make whale watching and cutting fishing nets away from the prop at sea much more comfortable!
Unfortunately, Humphree has fallen short in one area: noise. Our stabilizers make an annoying clicking noise when the fins reverse direction. Occasionally, they make a clunk so loud it jars me from sleep. We’ve been discussing the issues with Humphree. They admit some servos were shipped missing a washer, and think this is the problem we’re dealing with. The fix, they say, is to haul the boat and have techs from Sweden, where they’re made, take the servo apart and install the missing washer. Frustratingly, we’ve been waiting for a few months for this resolution and don’t yet have a service date. Hopefully we can update this soon with a happy resolution. You can hear the sound of the stabilizers below, with the loud thunking occurring at about 40 seconds:
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