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Sail Port Stephens 2026

Measurer Ken explains the Public Interpretations

by America's Cup Media on 20 Apr 2007
Alinghi’s keel bulb unveiled. The strut deflection caused by a 20 tonne bulb is an engineering challenge but the Public Interpretations are clear, as to what can be done to reduce strut deflection. Ivo Rovira /Alinghi
Chief Measurer Ken McAlpine explains the Public Interpretations

Gaining an edge in design often means getting close to the boundaries of the rule. With so much at stake, discovering that your pride and joy doesn't measure and qualify as being a legal America's Cup Class boat could be disastrous

The measurement team led by Ken McAlpine is equally keen to make sure that there are as few grey areas as possible and that the rules that govern the design of the boat remain clear-cut.

In order to ensure that there is a dialogue between designers and the measurers, teams can ask for an official interpretation on any aspect of the rule. Before April 1 2006 teams can ask for the questions and answers, the interpretations to be kept confidential or put into the public domain. After that date all interpretation are published directly into the public domain.

Q - How does the process work?

A – If there are elements that designers aren't sure of they have the right to ask for interpretations. Following a request, the interpretations are issued by the whole measurement committee. Sometimes there are many drafts until a consensus view of the answer is achieved.

Q- Is the identity of the team or person always confidential?

A - Yes.

Q- What if a measurer rather than a team is unsure as to a particular rule?

A - There is a process where if a measurer is unsure of the interpretation of the rule, he can ask for an interpretation as well.

Q – Is the source of the question made public in this case?

A – No. The source of the request for public interpretation remains confidential

Q – Where are the interpretations available?

A – On the web site. www.americascup.com

Q – Do the questions come on a regular basis over the period of the build up to the racing or do they come in a rush at the end?

A – They come in a pretty steady stream and pretty regularly although just before a regatta we get a flurry of activity.

Q – Is there any discernable pattern to the questions?

A – The questions are usually spread over a number of issues and we normally expect there to be a concentration of questions around certain issues. Sometimes the answers are clear-cut, sometimes they're not.

Q – More recently and in the case of Interpretation 22, are the questions looking for a loophole?

A – I don't think so. The team that asked it were looking for it were interested to see how far the issue could be pushed. But I don't think there is a loophole there.

Q – Are the questions that are asked always clear-cut?

A - Sometimes we get a batch of questions where one question leads to another, then another, then another and you've got to be very careful. Quite often the question is not the one that they really want to know and we can find ourselves boxed into a corner. We are very conscious of that and when the first question comes we're already thinking where this could be going.
sMRT AIS Man Overboard Beacons AUS / NZSydney International On-Water Boat Show 2025Kingfisher Yacht Ropes at METSTRADE 2025

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