Written by Ben Stein on Jan 15, 2018 for Panbo, The Marine Electronics Hub
As I sat down to write this article I flashed back to an eye-opening technology experience at the 2015 Fort Lauderdale International Boat Show. My wife and I found ourselves on the Seakeeper roll stabilization demo boat in the mouth of the Port Everglades inlet with a Viking 60-foot sportfish doing circles around us throwing as big a wake as possible. Our demo ride led to a major install on our Carver motor yacht, which I can recall in vivid detail, but which also significantly improved our subsequent family voyage around the Great Loop...
By that Lauderdale show my wife and I were seriously discussing the Great Loop trip. Years before, when I started bugging her to take this "little trip" we were both in our mid-thirties with two young children and I was working very full time in financial services technology with travel most weeks. I think she felt it safe to ignore my pestering as day-dreaming.
As 2015 drew to a close my satisfaction with the work was rapidly declining and I negotiated my exit six months into the future. Suddenly, my idle day-dreaming turned into full-on possibility. If we left in the summer of 2016 our kids would be six and nine, hopefully a good time for a year of travel and home (boat) schooling. We did debate a fair amount but ultimately decided that while there were plenty of reasons not to go, we were going to give it a try.
We already owned a Carver Voyager 570. We contemplated purchasing a new boat better suited for the Great Loop, but research mainly pointed to a smaller one. With four of us on the boat we wanted the space we had and ultimately decided that our boat was as good as any.
Now on to the next issue. My wife has never been overly comfortable with the natural side-to-side rolling action of our boat. My youngest daughter, Madelyn, seemingly inherited this discomfort but without my wife's grace in managing the discomfort. The entire summer of 2013 consisted of her chanting "Maddy go home" every time the boat rocked. So, as we walked through the boat show looking at all the pretty new boats and gadgetry, the Seakeeper booth got our attention.
I'd been intrigued by Seakeeper's gyroscopic stabilization technology since they first started shipping product. While at the show I talked to my friend Mike Walsh from Marine Services Corp. and mentioned Seakeeper in jest, thinking it too expensive and too difficult to install.. He quickly convinced me that I should really consider it. His facility hadn't done an install yet but he was confident they were up to the task and he was interested in taking one on.
So we circled back to the Seakeeper booth and signed up for the demo ride. We were soon heading out the inlet to meet the big Viking. When it circled us a few times, the Seakeeper handled the wake really well, but then the captain locked the gyro and the boat rolled nearly rub rail to rub rail.
At this point my wife, Laura, was holding on and not looking too happy. The captain unlocked the Seakeeper and about seven seconds later all rolling stopped; the boat rode up and down over the wake with pretty much no perceptible roll. At that moment I knew that my normally very frugal wife was sold. What I didn't fully understand yet was how much the Seakeeper would improve our displacement cruising.
Seakeeper has now evolved to making many models for different sized boats and different power options but each is a gyroscopic stabilizer. They work by spinning a large, heavy counterweight inside of an enclosure at high RPMs, creating a spinning-top-like inertial force. In the case of our Seakeeper 9 that's a 900 pound counterweight spinning at 9,000 RPM. A near vacuum inside the enclosure and water cooling help make this possible, but it still takes significant power.
So how does it actually work? The stabilizer is mounted in the boat so that it precesses (gyro jargon for rolling back and forth) forward and aft. This forward and aft precession produces force countering the boat's natural tendency to roll side to side. Basically, Seakeeper is taking advantage of the same property that keeps you upright on a bicycle when the wheels are spinning. A great illustration of this property is available from the Exploratorium.
Seakeeper has developed an advanced control unit that sits in the back of the gyro enclosure above the ball. Taking input from sensors on the unit, it controls the motor that spins the counterweight as well as the hydraulic brake you can see on the right side of the unit. When you see the ball precess back and forth in an active Seakeeper video (around the 1:08 mark in this Seakeeper promotional video), you might think there's a motor or hydraulic ram moving it around. But that's not the case. What you're seeing is the force of the spinning counterweight move the ball.
Because the ball can only move in one axis, fore and aft, the desire of the ball to move side to side is transferred to the mounting bracket and ultimately the hull of the boat as stabilizing force. The control unit is responsible for making sure the gyro operates safely within Seakeeper defined limits. For instance, the braking circuit can stop the gyro from precessing (which stops it from stabilizing), as well as slow its precession when it nears the end of its 140 degrees of precession.
Once we returned from Fort Lauderdale we got down to the business of figuring out how to install a roughly 1,200 pound, three foot cube in our boat. Even though Seakeeper says it doesn't need to be centered in the boat or even particularly low, this wasn't an easy proposition. The fuel tanks on a Carver Voyager 570 are at the aft end of the engine room, are only a little more than two feet apart, and there was no way to get the stabilizer forward of that point. So we settled on the lazarette as our install location. After some measuring, some mocking up, some head scratching, and some more measuring, a plan emerged.
We'd have to relocate the shore power isolation transformers but the gyro would fit center line aft over the steering gear. It turns out the engine room hatch was about half an inch smaller than the smallest dimension of a Seakeeper 9, so we anticipated an adventure just getting it into the boat. With a vague plan in place, even some emerging confidence that we could make this all happen, a Seakeeper 9 was ordered. As the calendar flipped to 2016 a nondescript wooden crate arrived with precious cargo inside.
Meanwhile we worked with a marine fabricator to build the needed custom bracket, and in turn the fabricator worked with a naval architect to ensure the boat's hollow stringer structure stood up to the maximum loads the stabilizer could impose, which equate to roughly 14,000 foot pounds of torque.
It was during this stage that we encountered one limitation of working with Seakeeper. Although the company understandably requires approval review of your installation design, in our experience it does not help much in the design process. I suspect this is due to liability concerns but it's difficult when your fabricator complains that he's working in an information vacuum. I understand that the installer must take some responsibility in the process, but I wish Seakeeper would share more of what must be a vast trove of install knowledge.
That said, the design our fabricator ended up proposing incorporated all four main longitudinal stringers in the boat. The overall bracket starts with a u-shaped base over about a five foot section of those four stringers. In the picture above you can see the base for the center two stringers with the core box the stabilizer bolts to welded on. The outer two stringers' base sections then bolt to this core box.
Seakeeper does specify that the bracket be glued to the structure of the boat rather than bolted. In fact, a representative described a phenomenon where the bolts can act a little like a wire cutting through butter. In other words, with the force levels involved, the bolts can become cutting instruments turning the stringer holes into slots, allowing the Seakeeper to walk and possibly worse.
So once the bracket was fabricated, it was time to glue it down to the stringers. This was a one try affair, as the adhesive used is the same used in bonding aluminum automobile structural members and, from what I understand, once cured it doesn't let go easily. I'm not a naturally patient person and the process of creating and installing the bracket was trying.
Thankfully, the fabricator was methodical in his approach, diligently avoiding miscalculations, and we saw his success during the March, 2016 install. The process involved a couple of fork lifts, a couple of come-alongs and a porta-power to stretch the engine room hatch opening to fit the stabilizer. Actually it had to be put in on end and then rolled into place.
While it was stressful to watch this process knowing that several months of effort could have been in vain, the install ultimately went off without a hitch. Now the electrical connections needed to be made, the control system installed and the commissioning work completed.
Fortunately we have a 23kw generator so the 3kw maximum draw from the Seakeeper wasn't a major factor. Also, the control units use standard DeviceNet Micro-C connectors like NMEA-2000 networks, and I was just completing an electronics refit on the boat. So running those cables was pretty simple as all the cable chases on the boat were open and accessible.
One cloudy April day it was time to get the boat off the dock and see what the stabilizer could do. But since Have Another Day's winter home on the Little Calumet River is an hour plus from Lake Michigan's potentially rough waters, we simply pulled the boat off the dock along with a 20' skiff which we then used to throw wakes.
The wakes were no match for the Seakeeper. It precessed a few degrees, and the boat never rolled at all. The early returns, though highly incomplete, were very positive. The next test was a run out to the lake, but as Mr. Murphy would have it, we managed to pick what was likely the only flat-calm day in early April. So that's why possibly puzzled observers saw a big Carver doing donuts and then stopping dead in its own wake. Again the boat behaved very favorably but I still didn't feel like we knew the full capabilities of our boat and Seakeeper working together.
Actually, fully appreciating the Seakeeper took some time. Next up was finishing the lazarette install with new shelves and component dressings. Then the summer spent on the Lake was more about Great Loop preparations than extensive cruising.
But we did spend a fair amount of time at anchor and one of the great things about gyroscopic stabilizers is they work at rest. In fact, a gyro is most effective at rest and becomes less effective the faster the boat travels, and this characteristic nicely aligns with a planing hull like ours.
Have Another Day generates reasonable lateral stability on plane from the two large spinning screws underneath her. Her Achilles heel has always been at low speed where the smooth-bottomed planing hull allows a fair amount of roll. During our time at anchor and at low speed cruising around Chicago's waterfront we had the opportunity to see and feel the stabilizer in action. We were impressed.
The boat's pronounced tendency to roll at anchor and at low speed was nearly entirely eliminated. The worst wake or wave would only roll the boat a few degrees before she came back to a level and stable footing. Gone were the pendulum-like rolls going back and forth first with the wave and then with the resulting momentum.
On the morning of August 29th, 2016 Laura, Molly, Madelyn and I left for our Great Loop adventure. For the next two months we were on calm rivers while the stabilizer mostly just rested. But upon arrival in Mobile Bay, it was quickly back into service, and was helpful as we travelled alternately in exposed waters and the Gulf Intracoastal Waterway. It even neutralized a beam chop as we crossed the Florida panhandle to St. Petersburg on plane.
But it was in open waters ahead, and especially our crossing back from the Bahamas, that we really experienced improved comfort, even at displacement speeds.The forecast was 3-5 footers with an 11 second period, but we encountered higher waves with shorter period. This meant hours of steep five footers on our beam but the Seakeeper kept the boat flat and level even at 9 knots.
In conclusion, the Seakeeper has done what we hoped it would. A boat that we were previously comfortable cruising only on plane is now comfortable at nearly all speeds. In fact, our preferred cruising speed became 9 knots. With the new-found stability at that moderate speed everyone is more comfortable with the gentle motions of the relaxed pace. We also are able to cruise above 1 nautical mile per gallon instead of our just over 2 gallon per mile fuel burn on plane.
At the same time we can now sit at anchor comfortably without worry of rolling from waves or wake. But it's also important to realize what the Seakeeper can't fix. Our boat has an unfortunate tendency to pound in a head sea, for instance, and the stabilizer can't do a thing about that. There's also the Seakeeper 9's $72,400 price plus the installation cost. Living on our boat for 14 months makes the investment easier to justify, and I think it will help the resale value, but I'm also realistic that resale return may be pennies or dimes on the dollar.
Overall the experiment was a success. Like every boat related decision, the finances aren't always pretty, but the payoff our family received has been tremendous. When we finished the Great Loop last October 9th, we had enjoyed the trip even more than we ever thought we would. My once reluctant wife is now the biggest advocate of getting back on the boat and continuing to cruise. My children experienced first hand things most of their peers only have the opportunity to read about. If you want to read more about our trip we blogged the entire experience at www.haveanotherdaysgreatloop.com.
I probably don't have to ask, but please give Ben Stein a warm welcome for his first Panbo entry ~ Old Ben