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Electronics

Game Changer?

Twin Disc challenges pod drives with a smooth, quick joystick system for shaft-drive boats.


Most likely, it was the eyebrow that got me. I was winding up a pleasant dinner with a boatbuilding friend at the recent Fort Lauderdale International Boat Show and gabbing about one of my favorite topics—the super-sophistication of oil-field vessels—when he turned to me, dabbed his mustache with a linen napkin, and raised an eyebrow while pulling a business card from his shirt pocket. Lots of people pull cards at boat shows, but few raise their eyebrows so intriguingly.

“The thing I am turning you on to here, Bill, is confidential,” he said while writing something on the back of the card, “but if you call this number and mention my name, I think they’ll let you see the system.”

The next afternoon, hot on the heels of several phone conversations, the corporate folks at Twin Disc had finally agreed to let PMY do a story about something that was still very hush-hush, which is why I was standing at a designated spot well beyond the hubbub of the show, waiting for a ride to an undisclosed location. At length, a Lincoln Navigator pulled up, a side door opened, and as soon as I climbed inside, we sped off, while Twin Disc’s managing director of Australian operations, Glenn Frettingham, launched into a fast and furious dissertation.

Here’s the gist: Not long after pod propulsion systems were introduced to the recreational marine marketplace, first by Volvo Penta in 2005 and then by Cummins-MerCruiser a year later, Twin Disc saw the writing on the wall. Due to the exceptionally easy dockside maneuverability their joystick control systems were likely to soon afford, Volvo Penta and Cummins-MerCruiser were poised to corner the market on recreational marine propulsion, leaving purveyors of inboard-drive system components like Twin Disc to potentially fade from the scene. Clearly, an alternative system was called for.

Twin Disc’s engineers began looking for a solution by examining the commercial side of their business, where for years oil-field support vessels have had maneuvering and dynamic-positioning (station-keeping) capabilities that were equal to—if not more sophisticated than—those being touted by manufacturers of recreational systems today. Indeed, some two decades ago, when I was working on such vessels, joystick-DP systems were already common and spreading rapidly throughout the industry.

The next step entailed the purchase of a test bed, a mainstream, off-the-shelf 47-foot inboard-drive sportfisherman. It was equipped with Twin Disc’s QuickShift transmissions, unique marine gears that are not part of the pod systems on recreational vessels but are currently part of many commercial systems. The Quick-Shift is a robust, patented, and proven piece of machinery (see “How It Works,” this story) that offers several maneuverability-enhancing features standard transmissions lack, among them lightning-fast clutch response; smooth, seamless gear engagement; and the ability to output extraordinarily low propeller velocities. More to the point, where a conventional marine transmission typically shifts with a delayed thunk and offers a comparatively narrow range of output revs, QuickShift responds smoothly and almost instantaneously and outputs a broad range of revs, from low to high.

The QuickShift is the heart of Twin Disc’s new system precisely because it is fast. A pod system takes time to swing from hardover to hardover. (Remember: a pod-drive boat has no rudders, and the pods must accelerate then decelerate through each maneuvering iteration, which takes time.) QuickShift, on the other hand, can apply torque to a propeller virtually instantaneously, then apply torque in the opposite direction also instantaneously. This, claimed Frettingham, makes a boat equipped with the Twin Disc system faster to react and more agile than any pod system. Moreover, he continued, the greater time required for a pod drive to swing from one extreme to another to affect a maneuver—particularly when the accelerations and decelerations necessary to preserve both onboard comfort and transverse stability are factored in—is simply not a factor in a system equipped with QuickShift.

Twin Disc’s engineers modified the 47-footer only slightly, adding a computer programmed with proprietary software and BCS hydraulic bow and stern thrusters, the latter chosen because electric thrusters typically lack the durability necessary for extended operation in applications that approximate commercial ones. The upshot, Frettingham assured me, was a system that outperforms pods at the dock, can be retrofitted to virtually any inboard boat, is easily be adapted to accept full dynamic-positioning capability in the future (if Twin Disc opts to offer it), and requires none of the hull alterations that pods do.

“We’d like you to give the system a try,” Frettingham concluded as we slammed the Lincoln’s doors and began walking toward a little marina on Fort Lauderdale’s New River. From a distance, the 47-footer looked like any other well-maintained mid-range convertible. Her flying bridge steering station, though, announced a difference. Alongside the 316L stainless steel EC300 Twin Disc Power Commander electronic engine controls to the right of the wheel was a solid stainless steel joystick with a large knob atop it. After cranking up the engines, Twin Disc’s skipper, Capt.

Marty Mason, settled into the co-pilot’s seat and said simply, “She’s all yours, Bill.”

During the ensuing two hours, I docked the sportfisherman stern-first in several different slips, negotiated a couple of tight fairways with dead-end turnarounds, spun the boat within her own length numerous times between the confines of two fingerpiers (sometimes at exhilaratingly fast speeds and sometimes quite slowly), negotiated a doglegged channel through a railway bridge (with and without traffic), and finally, after trying every conceivable maneuvering trick I could think of (with total success), returned the boat to her slip, stern-first—all using only the joystick.

My overall impression? The system is smoother than warm butter, as unfalteringly constant as a Swiss watch, and church-mouse quiet. And because QuickShift also governed propeller speeds during my maneuvering, our engines maintained a constant 900 rpm throughout, even as I spun the boat with a vengeance. At no time could I discern an appreciable delay or hesitancy. Applying the slightest pressure to the joystick—whether to rotate the boat, walk her sideways, or move her forward, astern, or on the diagonal—produced an absolutely instantaneous result.

Frettingham was not able to tell me whether Twin Disc’s new system will debut at the Miami International Boat Show this February, how much it will cost exactly, or what it will be called, although EJS (Express Joystick System) seems to be the front-runner. Nor was he able to speculate on the cost relative to the two pod-drive systems, although it would seem that Twin Disc’s would be less costly based on its greater mechanical simplicity. And certainly, Twin Disc is not claiming increased operational efficiencies, a reduction in installation time and complexity, and the interior space savings associated with pod drives.

But judging strictly on the basis of dockside maneuvering, I believe Twin Disc’s got a viable alternative to pod-type propulsion here, one that could conceivably give Volvo Penta and Cummins-MerCruiser a run for their money.

Twin Disc (262) 638-4000. www.twindisc.com.

This article originally appeared in the January 2010 issue of Power & Motoryacht magazine.

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