Gladwell's Line- America's Cup - the Riddle of the Rudders

by Richard Gladwell on 26 Nov 2009
After today's Hearing in the Appellate Division of the New York Supreme Court, the Challenger for the America's Cup stated that the inclusion of rudders in the crucial Load Waterline length measurement would disqualify GGYC's yacht.

Calculations by Sail-World from photos show that the length of BOR90, as the Challenger has been known to date, would extend to around 98ft, if the rudder on the outer float, or ama, were included in the length measurement, as argued by Societe Nautique de Geneve.

In one of 14 points that the New York Supreme Court has been asked to rule in the two year legal tragi-comedy that has been the lot of the America's Cup, Justice Shirley Kornreich ruled in late October that rudders would not be included in the vexed Load Waterline Length measurement, which is peculiar to the America's Cup. That ruling was not accepted by the Defender who Appealed in early November.

The 19th century Deed of Gift for the America's Cup prescribes that if of one mast the competing yachts shall not be less than 44ft nor more than 90ft on the load waterline. The Deed does not specify how Load Waterline Length should be measured. It is over to the organising club/Defender to specify how that should be done, when the match is being conducted without Mutual Consent - as was done in 1988 for the Big Boat Challenge (or MisMatch) between the catamaran of San Diego yacht club and the 130ft monohull of Mercury Bay Boating Club (New Zealand).

On 6 August 2009, Societe Nautique de Geneve issued rules for the measurement of the yachts which included the rudder in the length measurement.

The first of the seven rules covering measurement, issued by SNG, stated:

'For the purposes of measurement, the 'length on load water line' is the distance between a line perpendicular to the yacht’s centre line and passing through the furthest forward point of intersection of the yacht with its water-line plane, and a line perpendicular to the yacht’s centre line and passing through the aftermost point of intersection of the yacht with its water line plane.'

While the rule's language is complex, the measurement practice is simple.

With the yacht, floating in still water, and with all the required gear on board, the measurer marks the point where the yacht's hull meets the water at its forward point. He/she then moves to the yachts stern and puts a second mark at the point where the hull exits the water.

Standing on deck, maybe with the use of a plumbline or similar device the measurer will extend the waterline up to deck level, as a measuring convenience, and will measure between the forward and aftermost points.

That distance, between the two points, must not exceed 90ft.

Because she is a trimaran, BMW Oracle Racing have been able to 'cheat' the measurement length rule by having a main hull which measures less the the 90ft Load Waterline Length. However her design team ave cleverly designed her two outer hulls/floats/amas so that they sit just clear of the water when in measurement mode. They 'kiss' the water at their centrepoint - enough to comply with the maximum waterline beam measurement, but no more - and most of the length the ama does not touch the water.

('Cheat' is measurement and maybe design slang, for a way in which the designers have developed a design feature to meet a measurement point. But clearly if measured while a sailing a much longer measurement would come into play. Overhangs are a good example of 'cheats', as are knuckle bows, and bumping the hull in the International Offshore Rule days. There is nothing illegal about the 'cheats' and they are usually recognised as innovative design, and give speed advantage. With the passing of time, history generally treats such yachts kindly, terming them 'rule-beaters'.)

BOR90's amas are estimated to be around 110ft long or more, and increase the sailing length and potentially the speed of the trimaran when immersed.

At face value the rule announced by SNG includes rudders, the effect of this measurement dictate is that the measurer would still take the same forward measurement point (where the bow of BOR90 entered the water), but the aft measurement point would move from the main hull exit/intersection point, to the point where the back edge of the rudder on the ama of BOR90 left/intersected with the water - increasing the measured length by some eight feet, and putting the Challenger out of the America's Cup.

The SNG measurement system looks at the multihull yacht as a platform, not three separate hulls of which the centre one is used for LWL measurement. With this platform approach, a catamaran and trimaran can be consistently measured.

Of course, Alinghi 5, is subject to the same platform measurement rules. Because she is a catamaran her two hulls are of equal length. Her designers have been able to use the same 'cheat' as BOR90 in that a substantial part of her hull(s) forward sections overhang the water when in measurement mode, and such are not 'seen' for measurement purposes. Of course, in sailing mode the overhanging length soon becomes immersed and becomes effective sailing length. It is believed the two yachts are of similar sailing length.

Alinghi 5 has her rudders positioned just forward of the transom of her two 'main' hulls, and aftermost hull measurement point would be close to the intersection of her transom with the water, and not her rudder, as they are immersed.

What's the point?

Simply that if SNG can enforce their interpretation, then BOR90 will be measured out of the Match, as she exceeds the length permitted by the Deed of Gift, and this excess length would appear to be a margin of 8ft.

It would not be possible to move the rudders forward to fall within the length measurement, and Alinghi 5 would win the Match by default.

The Appellate Division of the New York Supreme Court reserved their judgment in the matter.

For a previous Sail-World commentary on this Waterline length issue, published two months ago, http://www.sail-world.com/NZ/index.cfm?SEID=2&Nid=61713&SRCID=0&ntid=0&tickeruid=0&tickerCID=0!click_here