Sound of Silence
On the Adler 76 Suprema, it’s what you don’t hear that will make you happy.
The Adler 76 Suprema is a clever new European motoryacht I saw at the Cannes Yachting Festival, and she presents us with a number of noteworthy details. One is that Adler is a Swiss company, but the yacht was built in Monfalcone, near Trieste, and also designed in Italy, by the well-known studio of Nuvolari Lenard. Tank testing for the hull took place in Vienna, and engineers from both Austria and Germany were involved in the concept and execution of the Suprema’s complex core. The structure is carbon fiber, and the interior fully customizable.
The accommodations layout is equally unusual. There is a wholly unexpected double cabin in the stern. This is reached down the aft salon companionway, which also offers access forward, via the crew’s quarters, to the engine room. The machinery space lies dead amidships, and the remaining two cabins consist of a luxurious full-beam master stateroom and a voluminous VIP forward that has excellent headroom and a pair of scissor berths, which can be slid apart or together as required.
There is a five-cabin layout as an option, but with just three suites in a hull this size there is no shortage of space on the lower deck, and it’s the same story overhead, where the sociable, open-plan galley and curved glass cockpit doors accentuate sightlines in the salon and capitalize on the light provided by the floor-to-ceiling windows. The interior design is modern, edgy and minimal, and the quality of finish meets the standards one expects from a modern Italian shipyard.
There is only one way up to the flybridge, from inside, which creates extra space in the cockpit. The flybridge itself is huge and remarkably well appointed, with space aft for a tender. Closed-circuit cameras allow all external areas of the yacht to be monitored from the lower helm, including the carbon-fiber propellers: You can watch them spinning. Other alluring attributes include under-floor heating and chilled cup holders. You can draw the curtains, dim the lights and switch on the air-conditioning using your iPad while still finishing your dinner ashore. This yacht is fully loaded.
Gallery: Adler 76 Suprema
She also comes with immense reserves of battery power, 170 kilowatt-hours—enough to run all of her electrical systems at anchor, including the air-conditioning, for up to 17 hours without resorting to the generator. Which is just as well, because she doesn’t have a generator.
Now we’re getting to the interesting part.
The Suprema features a hybrid propulsion system, many years in gestation. Her twin Caterpillar C18s can be used to spin a pair of conventional propeller shafts, or to generate power for the yacht’s two 100-kilowatt electric motors, which are built around the prop shafts and also function as generators. The diesels also charge the yacht’s huge bank of batteries, stowed under the engine room floor and extending well aft along the centerline. According to Adler, they can be fully charged by the engines in an hour.
One look inside the Adler’s engine room and you can see there’s something unusual going on. The Cat C18s look conventional enough, mounted at a modest angle and evidently driving straight shafts. Aft of each engine, though, there is a magnetic clutch, an electric motor that doubles as a generator, and then the transmission. The prop shafts can be turned by the Cats, the electric motors, or both. Or by battery power.
But even that is not the most clever thing I found aboard the Adler Suprema 76.
The cleverest thing about this yacht is that this propulsion technology, perhaps the most complex and versatile ever fitted in a vessel of this size, operates entirely automatically. The owner simply uses the boat as he would any other, while the hybrid system’s electronic control unit makes all the decisions about whether to use diesel power to push the boat along, electricity, or both.
Our usual test data shows the Adler’s performance as a conventional twin-diesel motoryacht, with no assistance from the electric motors. What it doesn’t show is how Adler’s hybrid system cleverly takes its cue from your inputs on the throttle levers, and supplies whatever is needed to produce the speed that you demand.
When we left the crowded harbor in Cannes, we were on battery power only, with which the Adler can cruise at 8 knots for up to an hour. As we ghosted in utter silence among the noisy chaos of show traffic and headed for the harbor mouth, the colorful graphic on the helm screen showed what was happening both visually and digitally: 5.8 knots, using 40 kilowatts, 20 from each electric motor. Once in less congested water, the picture changed with a gentle nudge forward on the throttles. One diesel started up and ran at 600 rpm with both electric motors still producing 20 kilowatts. Our speed increased to 7.6 knots.
As we cleared the harbor wall, turning south around the Vieux Port’s cheerful striped lighthouse, another push of the throttles woke the other diesel up. The screen’s graphic now showed us making 11.4 knots with both Caterpillars running at 1200 rpm and burning 11.9 gallons per hour of diesel between them, while the electric motors were now producing 80 kilowatts apiece. With the bow pointing at open water, we accelerated again: 13, 15, 17 knots, up the rev range on the diesels, with the electric motors continuing at 80 kilowatts each, until at 19 knots and 1850 rpm they cut out and the boat transitioned seamlessly to pure diesel mode and accelerated to maximum speed.
There is a “boost” mode, where you can augment maximum engine speed with maximum electric power and gain an extra knot or two, but it hardly seems necessary. As a conventional diesel motoryacht, the Adler handles and performs in exactly the way you would expect. Acceleration is steady and helm response is precise. An incisive stem and fine entry do an excellent job of slicing through head seas, and the boat felt reassuringly solid under way. With neither fins nor gyros fitted, we were curious to test the yacht’s stability by edging beam-to of its own wake. In spite of all the top hamper that comes with modern motoryacht design, there was surprisingly little roll—possibly because of all those batteries way down low on the centerline.
We pulled back on the throttles and the Adler eased off plane and settled into displacement mode, just like any other competent 76-foot motoryacht. A glance at the screen showed that the hybrid system had brought the electric motors back online. One diesel slowed to idle and then shut down, and the yacht slipped seamlessly into hybrid mode.
According to Adler, this was the Suprema at its most fuel-efficient. One diesel engine operating at 800 rpm was spinning one propeller shaft, while that shaft’s electric motor simultaneously ran as a generator. This provided the power for the other electric motor, which spun the other prop shaft. In this mode the yacht was cruising at 8 knots, burning around 3 gallons per hour, and therefore had a cruising range, allowing our usual 10 percent reserve, of around 3,300 nautical miles.
The Suprema 76 is complicated, but it works. The cleverest thing about its remarkable propulsion system is how simple it is: The boat just monitors your demand for speed and decides how best to deliver it. If you aren’t looking at the screens, you don’t know what’s happening in the engine room. And you don’t need to know—so you’re free to get on with enjoying your boat. And that’s probably the cleverest thing of all.
Adler 76 Suprema layout diagrams
Test Conditions: Air temperature: 68°F; humidity 57%; seas: 1-2’; wind: 5-10 knots.
Load: 16 persons.
Adler 76 Suprema — Final Boat Test Numbers:
Speeds are two-way averages measured w/GPS. GPH taken via Caterpillar display. Range is 90% of advertised fuel capacity. Sound levels measured at the lower helm. 65 dB(A) is the level of normal conversation.
DISPL.: 108,025 lb. (dry)
FUEL: 1,374 gal.
WATER: 232 gal.
TEST POWER: 2/1,150-hp Caterpillar C18, each coupled to both conventional prop shafts at 3:1 reduction ratio, and to combined electric motors/generators and magnetic clutch
OPTIONAL POWER: None
Adler Yachts, +41 41 729 39 48; adleryacht.com