This shot nicely illustrates the composition of the Hybrid Wing: a modest chord wing spar is made up in the now traditional way with the forward D-section carrying the primary loads, but with light, solid carbon top-hat pre-formed ribs to shape and support the wing covering in place of the more usual honeycomb-core webs. The super-high aspect mainsail attaches on cars while the trailing edge of the wing is convex which allows the leech twist of the sail to be controlled with less mainsheet tension than using a straight luff
lHalyard locks for the screacher, jib and mainsail. l The wing ribs were redesigned and the engineering of the composite structure of the spar was optimised. Testing the Hybrid Wing on the Caliente
delivered some eye-opening moments. One occurred motoring back to the dock with the sails down, when my 15-year-old son pushed on the ‘clew’ of the freely rotating Hybrid Wing. Instantly, within one boat length, we came to a dead stop despite the motor still churning forward! The wing has its pivot point close to the centre of effort so a small clew deflection engages a lot of aerodynamic power. We also learned not only that the new wing could be used for reverse power, but it also made for an effective side-thruster when docking. Meanwhile, our claims of the free-
feathering capabilities of the Hybrid Wing would also soon be put to the test. While moored off Bristol, Rhode Island in 2017 with its Hybrid Wing aloft, Caliente rode out a succession of hurricane feeder bands bringing winds of 50-70kt. When the weather improved a close inspection revealed that boat and rig had no issues (there was some relief at this point). Sailing performance was also full of
learning. We found that when over - powered we could effectively reef the hybrid ‘mainsail’ by easing the sheet, twist- ing off and depowering the top of the
42 SEAHORSE
square-top rig in a very reassuring fashion. The mainsail design on the Hybrid is very flat, since it is essentially just the trailing edge of the wing so very little drag results when it is twisted off in this way. Off the wind this feature was also effective to not only depower, but to lower the centre of effort and reduce heeling moment… and with it the bow-down forces that ulti- mately limit all multihull performance. Compared to Caliente’s conventional
rotating mast sailplan the Hybrid Wing made it easier to fly a hull smoothly. Small amounts of mainsheet adjustment were all that was required to find the sweet spot for hull flying. Caliente’s wing rotation was also highly effective in adding power when reaching and downwind VMG sailing. Even with lots of rotation we were impressed with how the tell-tales on both sides of the wing and sail were flowing smoothly. This confirmed our expectations that we could have both high lift coeffi- cients and low drag with the Hybrid Wing. Another factor that is important in
larger multihulls is the high structural loadings produced by mainsheet tension. As multihulls sail faster the apparent wind moves further forward. In power-up con- ditions reducing twist in the leech of a conventional multihull mainsail is crucial. However, reducing twist requires lots of mainsheet load and a corresponding high count of carbon in the mainsail leech itself
(as well as increasing the structure required at the take-off point). The Hybrid Wing reduces mainsheet
loads dramatically in two ways. The first is the simple one: since the wing accounts for a high proportion of the sailplan area the mainsail itself is much smaller than on a conventional rig. The second factor is a little more subtle.
With a convex curve on the trailing edge of the Hybrid Wing, rotating the wing causes the middle of the luff to sag to leeward. So if the leech twists the same amount as the luff sags, the wind sees zero effective twist. Thus there is no reason to try to grind (or hydraulically pump) the leech into a straight line as with a conventional main- sail… Mainsheet loads are reduced further. Windage is another performance killer
for fast multihulls. Since the Hybrid Wing is thick in chord it has immense inherent structural strength. No spreaders, dia- monds, intermediates, lowers, running backstays or jumpers are needed. Standing rigging is reduced to only two shrouds and the forestay for a major reduction in para- sitic drag. Weight savings from the mini- mal standing rigging are an added benefit. The Eagle 53 will travel to far horizons,
often aboard ships as deck freight. Eagle’s Hybrid Wing is built in two sections which allows safe transport with the wing halves secured between the hulls. So far the Eagle has been sailing primarily
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