The structural bases of the winch pods (left) continue through the deck and on down to the hull inner skin for maximum robustness and rigidity. Clean and simple tack area (centre) belies the huge loads involved. Interior (top right) is kept civilised with judicious use of white paint while the external solid carbon foredeck beams (lower right) also conceal various tack lines with their hydraulic rams
for a somewhat wider range of conditions than what could be achieved on only one headstay. With Read being super-sensitive to having any excess weight onboard, not to mention a limited space available for these bulky sails, getting more out of fewer sails in the inventory was also an impor- tant mandate.
Another constraint on inventory is the sheer physicality of these sails: Comanche’s record quest often includes restrictions on the use of non-manual power, so fewer sails also means less hauling them around by the team.
Another major factor in this process was assessing the loads on the sails, rig and spars, since this was critical feedback into the design loop. This part of the process was made easier since North and Southern Spars use the same software tools, so Braun could easily converse with South- ern’s Jarrad Wallace once the design itself got close. These studies indicated some massive loading expected on this boat: for example, jib sheet loads are expected to reach nine tons, and one look at the running backstay system tells you this will not be trivial either.
After using CFD modelling tools like Flow for upwind shapes and the Wolfson Unit’s Open Foam for downwind, Braun then needed to decide which combinations of aramid, carbon and Dyneema tapes would be used in the engineering of the 3Di RAW sails in the inventory. He described this part of optimising the design process as ‘operating in paradise’, because the flexible nature of 3Di construction allows placing the right materials at the right places in the sails without parasitic weight and bulk.
‘With 3Di RAW construction we could actually add a little more off-axis material to increase the durability of these sails, and still keep them light and strong. We think
36 SEAHORSE
they will actually hold up really well.’ Since high boat speeds will push the apparent wind forward so that it will never be further aft than 60°, Comanche’s sail inventory will be a remarkably light load of only a main, one AP spinnaker, seven headsails and two staysails.
Details in design = details in the build
Once Braun and Verdier/VPLP had agreed on their shapes and loads, it was then the engineering and build team led by Tim Hacket and Brandon Linton who needed to transform this into reality. Using the Hodgdon Yachts facilities in Boothbay Harbor, Maine, and working in close col- laboration with VPLP/Verdier, they used most of the same team who built Read’s last Puma VO70 to fabricate a newer, larger and even more sophisticated off- shore greyhound.
The size of the project necessitated the large workspace available at Hodgdon. As with most high-end boats nowadays, the hull was built in female tooling; intermedi- ate-modulus T800 pre-preg carbon from Gurit laminated in multiple 120g layers was used throughout the hull and deck to give greater strength than the standard modulus material, while Hacket says it took many months to get the Kevlar Nomex blocks fabricated then cut into the thicknesses needed for the various cores. This was only one of many key elements needed in a complex timeline to provide critical parts for the hull structure that could not be fabricated on site. The 25mm-thick monolithic keel frame struc- ture, for example, was built at Hall Spars in their autoclave, while the keel assembly jig was built at KZ Marine and shipped to Maine – the digital miracles of CNC milling and machining allowed both to fit perfectly when first installed. And it was
Guillaume Verdier and VPLP who suggested that the steel keel fin itself be produced by a specialist foundry in France – despite a six-month lead time. With strict weight targets in mind, the team found ways to shave off valuable kilos here and there without sacrificing the strength needed to accommodate the massive loads that this boat will develop when underway. It’s no longer sufficient to just minimise the fairing and eliminate as many voids as possible in the best carbon laminates: now every piece of carbon is sized and shaped precisely to meet the laminate requirements in the structure… there is no excess.
Thus the interior elements and even the non-working portions of the exterior elements resemble webs of criss-crossed unidirectional carbon tapes, all precisely sized and placed to direct loads from one location to another so the entire structure remains strong, light and stiff. The lami- nates and structures were all reviewed and the plan approved for compliance with ISO standards by Germanischer-Lloyd. One example of how the structural design works for both strength and light weight is the web of frames underlying the deck-stepped mast that ties together rig loads with the canting-keel assembly underneath. Design refinements to this frame assembly ultimately saved some 200kg and, while not spacious, there is an openness to the interior even in this critical load area of the boat.
And while there is not one extra gramme spent on creature comforts (even navigator Stan Honey says he feels a bit cramped in his nav space below), the inte- rior panels all feature a white-coloured non-skid to brighten up the carbon cave; in fact, there are no unfinished surfaces any- where… the finish quality even for such an aggressive raceboat design is excellent.
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