From the author’s own back catalogue… Left: HS Denison – Grumman built this for the US Maritime Administration to study the potential of large hydrofoil craft. My contribution was working on the down angle diagonal foil on the 19ft manned model of the boat. The foil was roughed out with machine cuts, my job as ‘nipper’ was to file it smooth in the large seaplane hangar. This runabout (left) is a test vehicle for fully submerged foils that were then being considered for a much larger naval craft. And (above) an experimental boron F-14 stabiliser. This project was my introduction (seduction, actually) to advanced composites. It had a titanium frame and boron skin, the 3-inch strip layers of which can be seen in the picture. Look closely around the edge of where the boron stops; this is the titanium ‘picture frame’ to which the boron was bonded. This frame was then fastened to the stabiliser frame. My job was to design the boron-titanium connection. Depending on thickness the connecting frame had between three and eight steps. Figuring out how to smoothly transition from one step to another took a fair bit of thinking
with a two-spreader plus jumper diamond shroud rigging system. Before the Duralumin mast was stepped
both wooden masts were tested. The bare weight of the heavy mast was 100lb under its 5,000lb design weight; the bare wood mast weight was 150lb over its 4,600lb target, so a 400lb difference ended up only 150lb. But Duralumin fittings on the light mast weighed 300lb less than the Monel and bronze fittings of the heavy mast so there was a total saving of 450lb on the lighter wooden mast. When the Duralumin mast was delivered
and stepped in early June its substantially smaller diameter was a big difference in looks and windage. But, as might be expected, it was a bit squirrelly, ultimately requiring a change to a much larger second spreader. The diamond configuration was also eliminated. Another innovation was a lower spreader
that could be folded upward on the leeward side to provide space for overlapping jibs. Before tacking, to prevent loss of the mast, the leeward-side spreader was pulled straight by lines tended by a crewmember specifically assigned to the job. As could have been predicted, there were
some close shaves, making things exciting. Once, in an unplanned-for tack, the spreader man was not at his post. In another incident on approaching the Fort Adams shore while tacking out of New- port, the tending line jammed. In both cases last-second action saved the day. But
30 SEAHORSE
the excitement was a bit much for Vander- bilt and he had abandoned the system by mid-summer. (In a bit of interesting America’s Cup
trivia, Alan Payne designed folding upper spreaders on Gretel II in 1970 for the same reasons of genoa leech clearance. They were slightly less risky as shroud tension ‘automatically’ pulled them straight during a tack.)
Trulok fittings Another Burgess innovation that year was the invention of the ‘Trulok’ or swaged connection for wire cable. Burgess knew that 19-strand cables were
stronger and stiffer but could not be spliced onto fittings as conventional cable could. Working with the American Cable Com- pany he created what we know today as swaged fittings. His were soft steel sleeves that were pressed onto the stay, work- hardening in the process. The sleeves were then threaded to attach to eye or turn- buckle bodies. The new Truloks developed 100 per cent of the cable strength where splices could only achieve 85 per cent of a cable’s strength. The ability to use 19- strand cables produced a 33 per cent saving in standing rigging weight. The combination of the Duralumin mast
and the 19-strand cables left Enterprise’s weight aloft far lower than her competi- tors’, a significant factor – perhaps the most significant – in her victories in the Defence trials and Cup Match.
Park Avenue boom As mentioned, by 1930 the aerodynamics of sails was an ever-higher priority. Because of his aviation background and his intimate knowledge of the work of fluid gurus Prandtl, Munk and Von Karman, Starling Burgess knew that optimising sail shape was key to keeping a performance edge. He had never liked the fact that a track-
mounted mainsail foot* created a large, flat area in the lower part of the sail, rendering it relatively ineffective drive-wise. To maintain the sail’s aerodynamic shape right down to the boom he designed a flat- topped triangular-shaped boom with mul- tiple flush-mounted cross tracks at 45cm spacing enabling the foot of the sail to ‘tack’ from side to side, maintaining the aerodynamic shape over its entire height. The cross tracks had removable pegs
that limited athwartships movement of the slides and had three settings, each set defined by green, yellow and red lines, similar to, as Vanderbilt described, the New York subway map. According to Burgess, they even named
each set Seventh Ave, Times Square Shuttle and Lexington Ave. In another reference to Manhattan, the fact that two men can walk along the boom side by side inspired the name Park Avenue Boom, a name that has survived to this day. Burgess also recognised early on that the boom’s more exaggerated endplate offered a worthwhile aerodynamic advantage over a conventional boom. Typical of many
America’s Cup w
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