Axcell 650By Capt. Bill Pike
A New Breed of Cat
Does Modern Hovercraft Technology Boost The Axcell 650’s Speed and Operating Efficiency?
After pulling into the Ocean Club at Port Canaveral, it took just a few seconds to spot my test boat du jour, tied up at the fuel dock, with a humongous, shark-like swath of “gills” (i.e., air intakes) at the stern, glinting in the sun. The sight stopped me in my tracks for just a moment. But time was flying, and there was no sense wasting it gawking, particularly when an absolutely unique and possibly far-reaching bit of marine propulsion technology stood waiting for sea trial.
In profile at least, the Axcell 650 looked like an express-style monohull, not a big powercat, and as I got closer, I theorized that J.C. Espinosa, the megayacht designer who’d done both her styling and layout, had most likely intended the illusion. Bruce Barsumian, electronics engineer, counter-surveillance-detection-equipment contractor, and founder of Axcell Yachts, was just settling a fuel bill when I strolled up. With reflector sunglasses and a devil-may-care grin, he certainly looked like the type of guy who’d devote 14 years and a whole heap of cash to a decidedly edgy project.
And I do mean edgy. Thanks to a little hovercraft-related technology, the naval-engineering capabilities of Donald L. Blount & Associates, the tooling expertise of Vector Works Marine in nearby Titusville, Florida, and the aforementioned contributions of Espinosa, Barsumian had created a boat that closely resembles a swoopy conventional midrange motoryacht but by all reports, could also generate her own friction-reducing cushion of air and then ride the darn thing, magic-carpet-style.
I began to see how such a phenomenon might actually be possible as we toured the starboard engine room, a nearly identical version of the one in the port sponson. Its after half was mainstreamy enough. Besides a bunch of expensive stainless steel fuel lines, top-shelf Northstar AGM batteries, and some precisely loomed and laid-out electrical runs, it featured a single 1,015-mhp Caterpillar C18 ACERT diesel on centerline, a beefy but lightweight carbon-fiber jackshaft that faded into the transom’s shadows, and a power-takeoff pump at the rear of the marine gear. The jackshaft coupled the engine to a fully articulated ZF MiniRex surface-piercing drive, Barsumian explained, and the power-takeoff unit (in league with its twin on the port main) energized onboard hydraulics, including a Lewmar windlass and thrusters.
The forward half of the space was a total eye-popper, however. It featured a huge, chest-high, centrifugal blower that inhales vast amounts of air through the earlier-referenced gills and then, via a proprietary microprocessor-controlled hydraulic system designed to kick in at 1300 rpm, pumps the stuff into specially designed, longitudinally oriented chambers in the running surface. Once pressurized, these chambers then support roughly half of the vessel’s weight at speed, thereby substantially reducing skin friction and hydrodynamic form drag. “We’re calling it HybridAir,” Barsumian enthused, “a patented technology that lets a big boat like this go fast but with relatively small engines.”
As you’d imagine, I was big-time excited about giving Barsumian’s HybridAir technology the full PMY wringout. So after departing the fuel dock and transiting the nearby Canaveral locks, I was pleased to see that conditions for testing on the Banana River were expeditious, with little more than a one-foot chop to contend with, only light, variable breezes blowing, and hardly any traffic at all. I closely watched Barsumian wheel his 650 into position for our first speed run. The boat seemed vaguely slippery, by which I mean she’d occasionally swing wide of the course corrections he fed her, although opposite wheel invariably brought her quickly back.
The next hour proved interesting, if slightly dispiriting. The 650 achieved a top speed of 39.9 mph, a fairly sporty velocity for a 61,000-pound vessel albeit well off her potential I’d say, given that our Caterpillar C18s turned just 2100 rpm at wide-open throttle. This recording was considerably less than the 2300 rpm that Caterpillar specifies as top-hop for this particular engine and rather less than the 2350 rpm that a builder of a new boat like the 650 would presumably shoot for in hopes of accommodating future weight gains from an owner’s personal effects. The recording also helped explain the low fuel-burn numbers I recorded on the Banana River. While our C18s should have been ingesting a total of about 107.2 gph at full speed according to Caterpillar, they in fact registered a wide-open fuel burn of just 89 gph, a significant shortfall indicating an equally significant shortfall in engine loading and horsepower output.
Barsumian attributed this not unimportant performance problem to some seriously over-pitched props as well as the extra build weight that tends to typify prototypes, both likely possibilities. Operating efficiencies were not especially impressive either, particularly in view of the similar performance numbers I’ve recorded over the years for 60-something monohull motoryachts with virtually equivalent powerplants and roughly the same displacements. On-plane efficiency peaked at 0.64 mpg at 1500 rpm, not much beyond the point at which the blowers were kicking in.
I got a heck of a charge out of driving the boat, though. Visibility from the comfy Stidd helm seat was wraparound excellent at all times. Trim adjustments to the steerable MiniRex surface-piercers proved decidedly simple and push-button-easy. And while sound levels were perhaps a little robust on the high end of the rpm register, I noted no super-distinguishable blower-related noise. Moreover, although tracking was acceptable at planing speeds and turns were broad and positive, I experienced the same tendency to wander at displacement speeds I’d noticed earlier when Barsumian was at the wheel. “It’s different—a little bit floaty,” I commented while tooling through Canaveral Harbor, “but it’s fun once you get used to it.”
I completed my examination of the 650’s finely fitted zebrawood-appointed interior, which I’d commenced shortly after we’d tied up, with a wholly positive attitude. Although the layout certainly was catamaran-esque in many respects (an extra-wide lounge and master on the main deck, a relatively narrow guest stateroom and galley in the port sponson, and another narrow guest and stowage area in the starboard sponson), Espinosa had so cleverly appointed and designed its lines and spaces, that I occasionally had trouble remembering I was touring a cat, not a monohull. Nice job!
My overall take on Barsumian’s HybridAir-powered 650 Catamaran is just a tad mixed, nevertheless. Certainly, the vessel is a new breed of cat, and she’s got a carefully crafted, cleverly laid-out interior. But her open-water performance was not quite equal to the promise of her avant-garde propulsion technology in my opinion, although some extra speed and efficiency may be in the offing.“With standard, lighter engines and all the extra prototype weight squeezed out,” Barsumian claims, “our next boat will probably get an extra three or four knots and enjoy a much-improved fuel burn.” I’ll be very interested in putting that claim to the test.
This article originally appeared in the March 2012 issue of Power & Motoryacht magazine.