Measuring an America's Cup yacht

Once a yacht wins the America's Cup they have the right to dictate the rules for the next one in consultation with the Challenger of Record. They will usually sit and discuss what they liked and what they disliked and will make the corresponding alterations in the rules that govern the world's top sailing yachts. As a result, there have been significant changes from version 4, used in Auckland, to version 5, used in the Louis Vuitton Acts in 2005 and 2006 and of course all racing in 2007.

Ken McAlpine and his team are involved fairly early in the process of measuring an America's Cup yacht. All boats are built on a mold, either female or male, and it has now become practice for the teams to ask them to take the core samples which are part of the class rule at the time when the boat is just ready to come off the mold or immediately off the mold. The reason behind this is that if there is a problem at that stage, it is much easier to correct it.

Then, the measurers visit the boat once it has a deck and has become more rigid. They either go at the boatbuilder's shed or the dedicated facility some of the teams have. The hull measurement is carried out with the boat on the ground not on the keel. This is due to the fact they can make a much more accurate measurement with the hull on the ground rather than 4.5 meters up in the air. They measure substantial distances and accuracy is primordial and being up on a forklift makes it very difficult to be precise.

This particular measurement is treated as sacrosanct because it is the only time the boat will be measured like that and they would be very loath to change anything from that original measurement unless there was a great error found. As a result, that measurement is very important and screws are put in each of the boats, reflecting the measurement points at that time, and these screws are referred to each time the boat is modified or changed into configuration as we go into the regatta.

As a result, even if the general public saw some of the boats here in Valencia at a late stage of the America's Cup, McAlpine had measured all of them in their particular place of construction or modification as the process was evolving. As stated previously, once the boats arrive in Valencia they will be stored on their keels, reducing substantially the precision and exactness of the measurers.

However, when the boats arrived in the team bases in Valencia they went through a process McAlipne called a "macrocheck", rechecking the original measurement using the best efforts they can. It would require a major mistake in order to alter the original dimensions that were listed when the boat was measured on the ground.

Ken McAlpine weighing chunks taken out of the hull of CHN-95. Photo copyright China Team

Sail numbers are issued as the boat is first laminated. The first lamination on the hull requires the team to ask for a sail number. There is no physical verification of the lamination and measurers rely on photos sent by the team. They are reasonably on the pulse of what is going on and know what team started laminating their boat. Still, there is a difference between allocating a sail number and issuing it. No sail number is formally issued unless a certificate is issued. Given the importance of some particular numbers in some cultures, countries or civilizations, there are always people trying to manipulate the system trying to have a specific number and McAlpine is tough on that issue.

Despite the fact that the hull comes already measured when the boat arrives in Valencia, there is still a lot of original measurement carried out here. It would be quite unusual to have the mast or sails already measured. Spinnaker poles and booms are also measured here. In addition, when the boat is here on its keel they would measure its draft. They drop the boat on the water and make sure it floats at the points the designers indicated it should float.

They also carry out the big test of weighing the boat. The instruments used are 8-9 years old and are very accurate. Its precision is 20kg, a small amount if one considers that these boats can weigh up to 24 tonnes. If the measured weigh trips over by 20kg then, as McAlpine put it, "you hear the sound of chainsaws". McAlpine estimate is that from the moment construction starts until a boat starts racing in Valencia, his team of 2-3 specialists will have spent up to 80 hours measuring it.

Sails are the "engine" of all yachts and obviously occupy an important place in the measurer's task list. According to the rules, each challenger has the right to use up to 45 sails for the Louis Vuitton Cup. The strategy and timing of measuring sails differs from one team to another. The bigger teams, with more resources, will initially measure the absolute minimum number of sails that they think would allow them to go through the first stages of competition, keeping as many sails as possible for the crucial later stages. Smaller teams will measure most the their sails right at the beginning.

There is a difference between measuring and declaring a sail though. Teams have the right to declare and use 45 sails but the number of sails McAlpine and his team measure is certainly bigger than that. They measure sails that, especially in the bigger teams, will never see the light of day. Usually teams would declare 2-3, maybe 4 mainsails and the rest would be evenly balanced between jibs and spinnakers.

Ready to drill a hole on the the hull of CHN-95, under the watchful eyes of Ken McAlpine. Photo copyright China Team

Teams are also allowed to replace up to 10% of a mainsail or jib and up to 20% of a spinnaker after an accident. Nevertheless, according to McAlpine, in most of the cases teams get most of the sail's pieces back and from previous experience so far in the vast majority of cases it's not considered to be a change.

The Louis Vuitton Cup notice of race allows for changes to be made on the boats between the two round robins. There are two sorts of modifications. The first one doesn't require to reweigh the boat and refloat it on the water. The second type of changes requires to have the yacht weighed and floated after being carried out. The notice of race permits one change of each type or two changes of the first type. Each of these changes has to be done on a case by case basis. The team first submits a plan with calculations showing the impact of the changes and the measurement committee makes an assessment of that, based on the calculations and then decide whether the modification requires to reweigh and refloat the boat.

A typical minor change that falls into the first type is a change in the angle of tack of wings. A change in the rudder is a "fifty-fifty" modification. Sometimes it requires a reweigh and float, sometimes not, depending on the weight and volume of the rudder. On the contrary, the change of fin or bulb certainly requires a reweigh and float.

Masts, booms and spinnaker poles can be changed at will, as long as the sailing weight after the change (excluding crew and sails) is not more than 100kg greater than the original measurement weight. Assuming a team want to change their mast, they advise the measurement committee and if, for example, the new one is 10kg heavier it's well within the limits but then they will have 10kg less maneuver in other changes. According to McAlpine, practically, this will be translated into carrying 10kg less of spares.