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Scuttlebutt News:

Pete Melvin: Stored Power on Catamarans and Trimarans

(July 14, 2009) Perhaps the disclosure of the event rules under which the 33rd America’s Cup would be run was deemed a non-issue. Normally, the Notice of Race for an event does not contain anything too earth shattering. However, this is the America’s Cup, and around every turn there are landmines.

When the Deed of Gift says the event must be run using the defender club’s “rules and regulations”, the BMW Oracle Racing (BOR) team determined that would be those rules used in the club’s annual regatta (which is another stipulation of the Deed). At the time of the challenge in 2007, the SNG annual regatta used the International Sailing Federation (ISAF) Racing Rules of Sailing (RRS) without any significant changes. Same again in 2008. But for 2009, the SNG annual regatta modified the RRS to delete Rule 51 and 52, which are the rules that prohibit movable ballast and non-manual power.

Stored power… that is what all the fuss is about. Alinghi wants to use it, but is not yet ready to disclose the rules that would permit it. Too much time would give BOR the opportunity to create their own system. The fact is that Alinghi, because she is a catamaran, may have to use stored power to be competitive. Here are some comments on the subject from esteemed multihull sailor and designer Pete Melvin of Morrelli & Melvin:

“On the Alinghi cat, it appears that they are going with hydraulic winches and some hydraulic cylinders for other controls such as shrouds, forestays, and possibly mainsheet.

“I have done some quick weight calculations and think that if you added an internal combustion engine, hydraulic fluid reservoir and fluid, hydraulic pump, and hydraulic control system and piping but then eliminated winch pedestals and six 200 lb grinders, that you would save about 400 lb. A downside to this (stored power system) is that the weight of the grinders is movable, whereas the weight of the hydraulics is fixed. You can always add more bodies to increase righting moment.

“Having powered winches is more important on a cat with Alinghi's configuration because a lot of the sheets and control lines need to be lead to the windward side. You end up with some winch and hardware redundancy since this hardware needs to be located on both sides of the boat. Then there is the issue with space to place pedestals and grinders. With powered winches, you save the cockpit or deck space and associated structural weight that would be needed to support pedestals and grinders.

“Then of course there is the advantage that the engine does not get tired and could be sized to provide more power and faster trimming than humans.

“On a trimaran with a central cockpit, you do not have winch and hardware redundancies as on a catamaran, but the boat could be sailed more efficiently if you were able to trim the sails faster. Imagine if you were sailing your Tornado catamaran and could only move the mainsheet at the rate of six inches per minute. You would need to do a lot more steering to keep the boat in the groove and you would not be able to sail as aggressively in puffy conditions. Maneuvers would also take a lot longer!

Note the engine compartment off the rear crossbeam of Alinghi 5. Photo by Stefano Gattini/Alinghi.

A close-up of the engine compartment. Photo by Philippe Chaplin.

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