Red Hornet is the prototype of an advanced racer/cruiser from DynaYacht of San Diego. After seven years of development, this program is inching toward the production stage, but it looks like that could be just around the corner.
The reason I believe people will want to buy derivatives of the Red Hornet is straight forward enough it sails just like an ordinary keelboat but a whole lot faster, more comfortably, and with less effort. The prototype DynaFlyer 40 has been racing boat-for-boat with ultralight-displacement boat (ULDB) sleds and IMS-style boats of 45 feet and up. Considering the amazing performance it has achieved, it is also downright cheapless than $150,000.
The innovation that makes this possible is called canting ballast twin-foil (CBTF) technology. It’s an amalgamation of two proven, but still fairly offbeat, ideas: canting ballast and dual, fore-and-aft rudders. As will soon become clear, this combination is a synergistic one, with each factor neatly overcoming the deficiencies of the other.
Canting keels have been getting a lot of attention lately thanks largely to the demonstrated speed superiority of Open Class 60s that are so equipped. The fact that the canting keel Vendee Globe boats also appear better able to recover from severe knockdowns than their water-ballasted counterparts is another strong point in their favor, and of particular interest to voyaging sailors.Canting keels are definitely not a new development, and Francis Herreshoff, among others, is known to have played with them. More recently, an experimental 55-footer called Red Herring has been sailing out of Bristol, R.I., since the early ’80s, and may be the first contemporary cant keeler. Only eight feet wide and sporting a rotating mast ketch rig, she uses canting ballast to overcome her obvious lack of form stability. And because the hydrofoil strut that supports the ballast bulb loses all effectiveness as an anti-leeway device once it’s inclined far to windward, Red Herring is equipped with tandem centerboards that can be deployed in various combinations for upwind and reaching work. Compared to conventional yachts, Red Herring gets a lot of speed from a very modest sail area,12 knots-plus in many conditions. However, twin centerboards, rudder, canting keel, and two rotating spars added up to rather more complexity than most folks would care to handle.
The direct forerunner of DynaYacht’s CBTF configuration was the 1987 America’s Cup challenger U.S.A.arguably the most peculiar yacht to ever race under the 12-meter class rule. Several California-based designers played a role in her development, notably Alberto Calderone, Matt Brown, and the late Gary Mull. History is unclear as to just who came up with the original idea, but the end result was a hull with a massive ballast bulbknown as “the geek”suspended by a ridiculously tiny strut made of high-strength steel. The 12-meter rule allows two moveable underwater appendages, which ordinarily meant a rudder and keel trim tab. Instead, U.S.A. had a second spade rudder positioned a short distance behind the knuckle of the bow.
Sound logic
The logic behind this highly unconventional underbody was, in fact, very sound. The 12-meter rule dictates very deep-bellied hulls while at the same time puts severe restrictions on overall draft. U.S.A.’s bow and stern rudders were both high-aspect foils with spans of around 10 feet, whereas the keels of ordinary 12s had a short three- to four-foot span. To further boost upwind performance, U.S.A.’s twin rudders could both be set up with a positive angle of attack. This angle of attack eliminated or even reversed leeway. In match racing maneuvers, the two-rudder configuration enabled U.S.A. to out-turn her opponents; and, when coming about, the forward rudder pulled the bow to windward slightly and gained her a bit of weather distance with every tack.
Many knowledgeable observers believed that, given a few more months of development time, U.S.A., skippered by the late Tom Blackhaller, would have won the challenger elimination trials and gone on take the America’s Cup. As it was, malfunctions in the complicated steering linkages (and some fairly severe discord within the crew) hobbled U.S.A. during a few key matches. Dennis Conner’s Stars and Stripes brought the Cup back to San Diego, and 12-meters were never again used in America’s Cup racing. Nevertheless, the potential value of separating the ballast function from the lift-producing and steering roles was clearly established.
For some of the personnel involved in the U.S.A. project, it seemed evident that the fore-and-aft rudder concept had potential. Chuck Robinson (now president of DynaYacht and gradually “retiring” from a highly successful career in business and politics) was enthusiastic about the idea of combining canting ballast with twin steerable foils and really got the ball rolling. Around 1990, Alberto Calderone and Matt Brown converted a 26-foot Soling day-racer into the first CBTF sailboat. Heartened by the dramatic boost in performance they achieved, the DynaYacht team went on to convert a Catalina 30 (average 10% speed gain), and a Hobie 33 ULDB that was stretched to 38 feet with a stern scoop. With the latter boat, Green Hornet, the hydraulic ballast canting equipment and twin-foil steering controls reached their current high state of refinement. Along the way the team composition changed a little: Calderone moved on to other projects, while 1992-95 America’s Cup veteran Bill Burns join his friend Matt Brown at the design desk and professional sailor Peter Isler signed on to look after demonstrations and sales. Faced with the prospect of selling the world on a sailboat that looks pretty weird by almost anyone’s standards, the team decided to convince the least conservative element in the sailing communitythe gung-ho racers. According to Burns, “The racing market is the one we’re focusing on initially because the racers will do anything for speedand racing gets us more media coverage.”Going for a test drive
Viewed in profile when afloat, there’s little to distinguish Red Hornet from the crowd of look-alike IMS-oriented racers. Seen end-on, it becomes evident that she’s an exceptionally narrow boat10-foot maximum beam with only seven feet of beam at the waterline. However, a wide stern and flared topsides allows for a spacious racing cockpit extending about half the length of the boat.
Skipper for the day was Bill Gladstone, a Chicago sailing school operator who had raced to Mackinaw Island in Red Hornet the previous week. All together we had four aboard, including a 12-year-old.
Close-hauled in a feeble three- to four-knot breeze, it helped to cant the ballast to leeward slightly, inducing heel to shape the sails and to “dial out” all traces of lee helm. Port/starboard push-button switches adjacent to the main traveler controls on either side of the cockpit are used to swing the ballast, a effortless procedure that takes just 12 seconds from lock-to-lock. This turns out to be quick enough to roll-tack the boat quite nicely in light air: ballast to leeward to head up into the tack, then back to near vertical as the sails pop across.
Later, when the breeze built into the 10-knot range, swinging the ballast from the neutral position to “maximum up” levered the boat up from a heel angle of at least 30° to a comfortable 10° or so. At the same time, Red Hornet accelerated from 5.5 knots to seven knots, still hard on the wind and with no one on the weather rail.
At six knots and above, a unique control known as “the collective” can be brought into play. Its role is to pivot the forward foil (rudder) to windward slightly, so both forward and aft foils will have a positive angle of attack while the boat is sailing straight ahead. By applying the correct amount of collective, leeway can be eliminated entirely, and with it, the extra resistance of cross-flow beneath the hull. According to Gladstone, the effect while racing is that the boat seems to climb almost magically away from nearby boats who appear to be pointing as high or higher.
Despite the need for mechanical linkages to interconnect the tiller and the two widely separated foils, Red Hornet has a light, pleasant helm. Because the forward and aft foils are hydrodynamically balanced and rotate in opposite directions during turns, steering requires minimal tiller force. And when we gybed the asymmetrical chute a few times in light air, I found that the two-foil steering system enabled the boat to carve through major turns exceptionally cleanly.
Unfortunately, we didn’t get to explore the boat’s heavy-weather potential, but those who have raced Red Hornet in a breeze describe two-finger steering while planing at 15 knots. For optimal control at higher speeds and in rough water, the steering foils are situated equidistant from the ballast strut and close to the locations where the bow and quarter waves crest.
When the ballast was deliberately swung all the way to leeward while sailing close-hauled in nine to 10 knots of true wind (about 16 apparent), Red Hornet lay over to around 45°, the foils lost their grip, and she headed up slightly into a mushy sort of broach. It was certainly not a round-up in the usual sense, and a touch of the canting control button brought the ballast up to windward, levering the boat back on her feet at once.
The masthead asymmetrical chute is flown from a retractable, non-articulating bowsprit, so in light-to-moderate airs it definitely helps to heel to windward to help the spinnaker luff roll out of the mainsail’s wind shadow. This, of course, is easily accomplished with the aid of the canting ballast. All in all it is a lot of fun to play with the canting feature, particularly at dockside when heeling the boat over to the maximum 18° will cause some bystanders to speculate that the thing must be sinking!
The inner secrets
In fact, there are no hidden secrets in the CBTF technologythe ballast canting system is housed beneath a compact lift-top box, and the steering linkages are fully exposed to anyone who comes aboard. The people at DynaYacht believe they have solid patent protection and may, in the future, sell rights to other builders; but at this stage they feel it’s advantageous to show the world how straightforward their systems really are.
The canting ballast mechanism centers on a four-inch-diameter stainless steel torque tube about 2.5 feet long. The ends of this tube are fitted into robust bearings that, in turn, are bolted to substantial transverse girders glassed to the hull skin. The torque tube is recessed about two inches into a longitudinal channel which forms a slender, blister-like bulge on the underside of the hull. This feature allows the ballast support strut to swing through 110° from side to side without contacting the hull.
The 1,800-pound lead torpedo is suspended from a six-foot strut made from a two-by-eight-inch (estimated dimensions) high-strength stainless steel billet. The billet has been milled down toward its outer end, and is enclosed in a streamlined fiberglass shell. To swing the ballast, there’s a lever arm about one foot long keyed to the forward end of the torque tube that is connected to a double-acting hydraulic ram. The system works at a mechanical disadvantage of approximately 1:6no sweat for hydraulics that are ideally suited to high-force/short-throw applications.
A high-efficiency 24-volt electric pump supplies hydraulic pressure to the system, with solenoid-actuated valves for manual control and limit switches to prevent over-rotation. Four six-volt batteries totaling 250 amp-hours power the unit. With this system, according to Bill Burns, the ballast can be tacked every five minutes for 18.2 hours before the batteries are 50% discharged! If the electrical pump fails, four minutes of pumping on a manual back-up will hoist the ballast to leeward. If the hydraulics go too, the keel can be swung down by gravity and locked in the midships position, allowing the DynaFlyer to sail like a conventional fixed-keel boat.
The steering system looks complex at first glance, but it is, in fact, very straightforward. Because the tiller is about six feet aft of the rear foil, it’s linked to the rear steering quadrant with a crank arm and tie rod. Low-stretch synthetic lines interconnect the quadrants on the two steering shafts. The so-called collective control is simply a pair of interconnected tackles operated by a continuous line that leads across the cockpit just behind the traveler. They deflect the two lines that connect the quadrants, effectively shortening one while lengthening the other by the same amount. Thanks to low-friction rudder shaft bearings and the hydrodynamic efficiency of the extremely high-aspect foils, the whole arrangement works very well.
A voyaging future?
No doubt the DynaYacht folks are right about racers being generally less reluctant than voyagers to go for CBTF technology, but a day aboard Red Hornet left me thinking more along voyaging lines. This boat is so pleasant and comfortable to sail short-handed, yet so remarkably quick, that notions of heading off to distant destinations just naturally come to mind.
The ability to heel or flatten the boat at will offers secondary advantages too, such as bottom scrubbing or recovering a man overboard by swinging the keel to leeward and rolling the victim over the lee rail.
A 60-foot cruising/racing boat using DynaYacht technology is about to be launched in Europe by former Maxi-boat owner Sandro Buzzi. This yacht is only 12 feet wide, displaces 16,500 pounds, and, although not palatial, is fitted out for comfortable voyaging. Whether it will be allowed to race against the Open 60s, Whitbread 60s, and so forth remains to be seen because the CBTF approach entails static heel angles nearly double the generally accepted 10°-per-side limits.
I asked Bill Burns about self-righting and received the answer I expectedthat these boats are so narrow that they are not at all inclined to remain inverted regardless of ballast position. If Red Hornet was thrown over directly to leeward by a huge breaking sea when the ballast was canted fully to windward, computer modeling suggests it would roll 360° with little or no delay.
Red Hornet can reputedly achieve 12 to 13 knots on a beam reach under spinnaker in just 15 knots true wind. The hull and rig remain almost bolt upright, and “Kevin the canting keel” swims along clearly visible just off the windward rail. These are speeds approaching the multihull range, achieved by a relatively low-tech monohull with aluminum spars (no carbon) and contemporary, but not exotic, hull construction. The CBTF underbody is, of course, the key, giving a narrow, low-resistance hull the stability to carry a comparatively outsized rig (SA/D= 29.2), while at the same time not bogging it down with tons of ballast. The displacement-to-length ratio of 73 hints at the potential for surfing and planing. Bill Gladstone summed it up nicely when he said, “Usually a boat is either powerful or nimble. But the DynaFlyer 40 is both. It has the power to sail upwind in strong winds, yet is swift off the wind and in light air.”
So why not CBTF for voyaging? Besides the “new-and-unproved” factor, there’s the issue of eight-foot-deep draft in the case of Red Hornet. Bill Burns is confident that a short ballast strut combined with a heavier bulb would still dramatically outperform conventional voyaging yachts.
Alternatively, the strut and foil could retract vertically when the keel was locked in the vertical position. The deep, slender fore-and-aft foils could conceivably also be retractable to allow a collision-damaged blade to be replaced while at sea. In any event, the DynaYacht CBTF program should give open-minded voyagers plenty to think about.
Contributing editor Sven Donaldson, a former sailmaker, is a marine technical writer based on the West Coast.
