Aerodyne 47

by George Day

Blue Water Sailing
July 2001


 

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THE PURSUIT OF CRUISING PERFECTION

The new Aerodyne 47 is the fruit of a collaboration between a veteran offshore cruiser, a noted “performance” designer and a world-class, high-tech builder. BWS test sailed the boat in small-craft-advisory weather and came away smiling

As we untied Eagle’s Wing from her perch at the Harbortown Marina dock in Ft. Pierce, Fla., we noticed a dozen or more transient cruising boats in the facility. A strong easterly wind had been blowing for the previous ten days, kicking up a maelstrom in the Gulf Stream offshore and tossing a four- to six-foot swell against the narrow St. Lucie inlet that leads to the sea. Pinned, that was the word on the docks.

We dropped the lines aboard the new Aerodyne 47 and motored toward the inlet, not knowing what to expect when we got to the narrow channel that leads seaward. The wind, topping 20 knots when we set out, diminished to 18 or so and the swell rolling into the channel remained steep but in no way impassable. With just the mainsail set and the motor humming, we punched into the swell making a steady 5.5 knots as we bucked our way out toward clear water.

As fate would have it, the engine overheated just as we cleared the last pair of bell buoys, stopping us short in the headwinds and seas. We threw the wheel over to starboard, and the 47-footer backed obediently on her large spade rudder as the bow fell off and we unrolled the jib. Within a minute we were surging ahead at 6.5 knots into five-foot waves and making good ground against 23 knots of apparent wind. Soon we were in deeper water and, with the wave train spreading out, Eagle’s Wing put her shoulder down and accelerated to 7.3 knots – all the while sailing at 40 degrees off the true wind.

Our first impression? Here was a sailboat that handles beautifully, can get you out of trouble with ease, doesn’t mind a good breeze and does it all at impressive speeds.

THE DESIGN
Aboard Eagle’s Wing with us were her owners Vic and Peg DeMattia, who conceived of the new boat and put together the collaboration that saw her to creation. Good experienced sailors, Vic and Peg brought a vision to the Eagle’s Wing project that pushed the limits of what we normally think of as a performance cruiser. They had spent three years cruising more or less fulltime aboard a Sundeer 56, a vessel they also had built, which made them more than familiar with Steve Dashew’s unique and innovative slant on cruising boat design.

The priorities that Vic wrote down at the project’s beginning included the basic notion that the new boat should be a very fine sailing boat – that it should be fast, weatherly, easy to manage solo (because couples are often, effectively, singlehanders while on passage), comfortable for a couple living aboard for extended cruises, and in need of minimum maintenance and repair. Many of these notions drive the Dashew design philosophy, which has led from the breakthrough Deerfoot boats of the early 80s to the monster metal cruisers of the Beowulf line today.

But Vic and Peg were not getting any younger and felt that the heavyweight component of equipment on a 56-footer and the associated high stress-loads were more than they wanted or needed to handle. Vic tackled the problem from a slightly novel angle. He started with the idea that the combined working sail area must not exceed 1,000 square feet, and that modern composite building techniques could achieve a Ballast/Displacement ratio of nearly 50%. Minimum sail area, a light hull and a high degree of ultimate stability would translate into a fast boat that could point well, go like mad off the wind and be small enough to enable a lone 64-year-old (fit and able) to operate all sailing systems from the safety of the cockpit.

The design concept was influenced by designer John Fox – well known and highly respected in Mini Transat circles – and ultimately drawn and designed by Rodger Martin. Martin has developed a well-earned reputation for boats that are good looking, extremely fast, comfortable in a running sea and thoughtfully conceived with the lone watchstander in mind.

The final plans show a short-ended vessel with a simple stern, a straight, sloping sheer and a slightly flared bow. The rig is small for a 47-footer, with a mast that tops out at 63’6”. The keel is a composite foil with a large, 10,000-pound squashed lead bulb on the bottom. It draws only six feet.

The hull form marks an evolution of hulls that Martin has been working on for several years, most recently with the Aerodyne 38 and the new Aerodyne 43. Some key elements are its reduced wetted surface, topsides that flare dramatically from a narrow beam at the waterline, and a fine, slightly concave bow with an entry angle of only 10 degrees. Aft, the buttock lines run out very straight, although the stern is tapered enough to give the hull balance; this is particularly important when running before a strong breeze in a large seaway.

Fox and Martin had been working with Zach de Beer of Aerodyne on the Aerodyne 38, so they knew what the South African composites wizards were capable of doing with heat-cured, epoxy-fabricated structures. By adding Aerodyne to the collaboration, DeMattia now had in place a team that could bring the prototype Eagle’s Wing to life.

The design for the 47 fulfills requirements set forth by DeMattia in some very interesting ways. The 47 tips in with a final “light” displacement of 25,370 pounds on a 42-foot waterline. While not ultra-light, the 47 earns a Displacement/Length ratio of 152, which puts it decidedly at the performance end of the spectrum. With an easily driven light hull, the boat carries ballast of 10,330 pounds on a draft of six feet. The Ballast/Displacement ratio of 46% is relatively high when compared to other boats in the performance category and accounts for the vessel’s stability underfoot and beneath a press of canvas. Further to this thought, the boat has an IMS stability index (limit of positive stability) of 128 degrees.

To meet the requirement that working sail area be kept under 1,000 square feet while providing enough horsepower for spirited sailing qualities – and a rig, by the way, compatible with the 65-foot fixed-bridge clearance along the Intracoastal Waterway – the team came up with a powerful sloop configuration featuring a high-roach main, a 100-percent headsail on a jib boom (a Hoyt JibBoom derivation), and downwind sails that include a Code 1 reacher (very flat) and a cruising spinnaker. The mast has been positioned at Station 4 to reduce the foretriangle and jib size, while maximizing mainsail acreage. The high-roach main adds efficient sail area without adding excess weight and drag. This in part is what allows the jib to remain small and manageable.
The combination of a light, highly stable hull, with a restrained, efficient, self-tacking sailplan, promises to deliver a cruising boat that is the best of both worlds – fast but very easy to handle.

CONSTRUCTION DETAILS
The Aerodyne 47 project operated under the “less is more” principle from the start. To achieve easy sail handling and a good turn of speed, the boat as noted had to be light and powered by a small but efficient rig. To make the boat light, the obvious choice in construction technique was to build the hull and deck from high-modulus composite materials; the final specifications called for vacuum-bagging cored sections in an epoxy, E-glass and Kevlar structure that then would be post cured in an oven. In the place of stringers and ribs, the internal bulkheads and furniture are tabbed together forming a pure monocoque structure made up of more than 40 panels plus the deck and hull.

The keel foil is molded integrally along with the hull, then filled with epoxy so that there is no keel-hull joint to leak or weaken during a grounding. The 10,000-pound ballast bulb is attached to the base of the keel foil with massive bolts and epoxy.

The whole structure is more than the sum of its parts, being as light as is reasonable in a cruising boat and stronger than boats built by conventional hand-laid methods. The Aerodyne 47 meets or exceeds the Offshore Racing Council’s Category 0 requirements –the same requirements that have to be met by Vendée Globe, Around Alone and Volvo/Whitbread boats. Meanwhile, the construction technique enables the builder to save more than 5,000 pounds in raw displacement over conventional fabrication techniques.

Systems for the 47 have been given the same thought and attention to detail as the construction. The goal was to locate heavy objects near the boat’s center of gravity to reduce pitching in head seas and to smooth out the boat’s motion when surging downwind. The engine sits under the galley counter amidships; the 1,000 amp/hour battery bank is directly over the keel; and more than a ton of water and fuel is placed directly amidships on either side of the keel.

The huge battery complement is fed by a custom alternator installation – one of the best, incidentally, that BWS has ever seen. Using a flexible coupling on the front of the main engine to drive a fixed-mounted power take-off unit, the engine can drive a massive 150-amp Balmar alternator that delivers more than 100-amps of effective output even after heating up, without adding weight, vibration or extraneous brackets to the engine. Having made a real effort to reduce electrical consumption – florescent and halogen lights, vacuum-panel insulation in the fridge, and so on – daily power consumption has been reduced to under 100 amp/hours, which in turn translates into less than an hour of engine-battery charging time per day.

If the devil is in the details, then this Aerodyne’s construction and systems engineering make her one devilishly fine boat.

UNDERWAY
The engine failure in St. Lucie Inlet was one of those things that happens to all sailors. We determined later that the cause was overheating due to a leak in the freshwater cooling circuit – the last item, incidentally, that the local boat yard (allegedly) had repaired! Sound familiar? Still the incident gave us a chance to see how well the 47 handles in a jam and how much confidence one derives from the boat’s ability to sail its way in or out of just about any situation.

One of the questions that many sailors have of a light-displacement, fin-keel performance cruiser is this: How will it handle sailing into head seas? Will it pound or crash off waves and knock out everyone’s fillings? So, we were delighted to discover as we cleared the inlet in a short steep chop that the 47 does not crash and bang in these conditions, even at seven knots. The hull lands with a firm swoosh and continues sailing ahead at speed instead of stopping short and shuddering like a startled mule.

With the high-roach main spreading extra sail area 50 feet aloft, we also wondered how the boat would react in gusty weather. First, in 23 knots of apparent wind the boat heeled over to approximately 18 degrees and stayed there – a comfortable angle. There was no need to shorten sail. Second, as puffs came at us, piping up to 25 and 27 on occasion, we felt her heel a bit, but more impressive was the way the boat surged forward, translating wind power into boatspeed. The ride was exhilarating, not unlike the sensation one gets from a little added pressure on a Porche 911’s accelerator.

Once we were a few miles away from the coast, we cracked off onto a beam reach to see how she handles a running beam-on swell of four to six feet. At 10 to 11 knots, the boat was sailing fast and easily, with very little pressure on the helm and no tendency to round up in puffs or as big swells rolled under us. This steady-as-she-goes, positive-tracking behavior in bouncy conditions comes from the forward position of the mainmast, the hull’s balanced water plane, the shape and size of the keel and the size of the rudder. After a few minutes we switched on the autopilot and watched with pleasure as the 47 held her course with no groaning from the equipment or corkscrewing in the somewhat crazy seas.
Falling off to a broad reach, she continued to accelerate and was able to hold elevens easily. The main is the prime driver on this angle and here is where all that roach really shines. But the 100-percent jib on the jib boom does its share as well; the jib boom holds the jib flat and keeps the head of the sail closed as it is eased – unlike a free-flying jib – so the sail adds real power to the downwind rig.

It was blowing too hard to hazard the reacher or cruising chute, so the only downwind suit we got our teeth into was wing-and-wing as we sailed back through the inlet. It was an interesting test, as the running sea and 15 knots of breeze were now meeting two-and-a-half knots of ebbing tide. The inlet was a washing machine of breaking seas, cross seas and swirling currents.

We popped the jib out to port and with the main out to starboard we rolled in through the seas at seven-plus knots – making less than five over the bottom. Eagle’s Wing corkscrewed a bit in the cross seas, but she was easy to steer and managed to surge ahead before the larger waves.

The last impression? Here was a boat that has real manners in lousy conditions and is at its best when you need it most. Plus, she’s fast.

BWS THOUGHTS
We have not dwelled on the accommodations package aboard the new Aerodyne 47 simply because the boat’s other qualities are so outstanding and warrant such comment. Having sailed her for a few hours and having seen what she can do, we rest assured that the 47 passes with flying colors the sailing and performance requirements her owners set for her.

Back in the marina we did take some time to explore the boat’s interior and found it a comfortable and commodious floating home. Unlike any number of lesser cruising boats, the 47 does not wrap a hull around an interior, but rather it has an interior fitted to a hull shape designed to give the boat optimum sailing characteristics. Significantly, no real sacrifices had to be made to create an interior with a double cabin forward and one aft, bracketing a main saloon that is eminently comfortable. The galley is large and useful, with good access to the fridge and freezer, and with the Force 10 stove offset aft slightly where it presents no danger to the cook in high-seas conditions. A huge double pantry has been built in under the companionway. The main dinette has a nifty folding table that works well both as a dining table in port and as a secure sea-table while underway. The bench seats of the settee and dinette are both long and wide enough to be good sea berths. One could live easily and comfortably aboard her.

As the collaboration of a team of experienced and innovative sailors, the Aerodyne 47 is a voyager’s boat. She is, in fact, the type of boat that circumnavigators often design for themselves after spending years motoring and motorsailing heavy boats around the world. She’ll knock off 200-mile days without breaking a sweat, will give up 240-mile days as a matter of course, and can give you the elusive 300-mile-day if you are willing to go for it.

In the end, the new Aerodyne 47 is one refinement of a performance cruising concept that sets a new standard for the cruising fleet. Cruising perfection? For cruisers who love to sail, the 47 comes mighty close.

Aerodyne 47 Specifications:
LOA 46’7” (14.2 m.)
LWL 42’1” (12.8 m.)
Beam 14’4” (4.37 m.)
Draft 6’0” (1.83 m.)
Disp 25,370 lbs. (11,508 kgs.)
Ballast 10,330 lbs. (4,686 kgs.)
SA (100%) 990 sq. ft.
(92 sq.m.)
Aux 56-hp. Yanmar
Water 200 gals.
(757 ltr.)
Fuel 100 gals.
(378 ltr.)
Mast ht. 63’6” (19.4 m.)
SA/D 18.2
D/L 152
Ballast/Disp. 46%
SRP $420,000

Aerodyne Yachts
Vic DeMattia
541 Hall Hill Rd. • Somers, CT 06071
860-749-2390 • Fax: 508-861-0266
www.aerodyneyachts.com

Rodger Martin Yacht Designs
PO Box 242 • Newport, RI 02840
401-849-9850 • Fax: 401-848-0119

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