Left: all the Cup teams are now using foil-adapted Nacra 17s to accelerate crew handling and increase general familiarity with foiled sailing. In the course of this small boat training the crews are regularly experiencing this kind of sudden and catastrophic ‘episode’, as foil instability leads to porpoising which can lead to a sudden and instantaneous loss of control
Army, he started to take an increasing interest in the controls system aspect of aerodynamics. ‘In 1966 I spent 15 months at Cranfield University in the UK doing a master’s degree in aircraft dynamics. And from that time on I was involved in the design of flight control systems for unmanned vehicles.’
Smith notes that the trial and error method of design has long since left the aero- space industry, and can’t help thinking the sailing world could benefit from a similar change of approach. ‘The Wright brothers started off very ad hoc in their approach, but it wasn’t long before they decided they needed to build a wind tunnel to get some real data to design their aircraft. ‘However, it wasn’t until the 1930s that serious dynamic stability studies were first applied to aircraft; and it was with the post- WWII era of guided weapons development that these techniques actually became well understood in the aviation world. Nearly all the work that was done on aircraft up until then was based on experience and on what they learned in the field.
‘It was common practice in the aircraft industry to always build two or three
‘The trial and error, the ad hoc approach to design, almost irrespective of what area you’re looking at, is by far the quickest and cheapest – if it works. The scientific approach is expensive… but it works all the time,’ adds Smith. All the time? There are some glaring examples, not least from the build-up to the 2013 America’s Cup, where some well- funded design teams got some of the science seriously wrong. How to explain that? ‘One of the problems, I believe, is that within these organisations they are lucky if they have someone who really understands the dynamics,’ says Smith. ‘They become preoccupied with all of the issues that relate to performance and don’t have a handle on those things that make the device stable to use. I mean, it’s fairly obvious in the 2013 America’s Cup that they didn’t have a clue about how to go about designing the foils for lifting the boat out.
prototype aircraft before you entered production. And you never designed an aircraft and a new power plant at the same time; you took an established power plant and put it into the aircraft you were designing. But over the past 20 years the likes of Airbus and Boeing have developed the science to such an extent that they can build the first aircraft and after flight test- ing and certification sell it as a going passenger aircraft, and they do that with- out the significant wind tunnel testing that was required up until about 1980.
‘There’s a huge amount of trial and error that went into the shape of those foils and even in the end I don’t think they understood the issues that are involved in making a foil- ing yacht fly at a stable, constant height. You go back and look at the videos of the Amer- ica’s Cup races and, for that matter, look at the videos of any of the catamarans that are now putting J-foils on their boats, and you’ll see that they have a very long-period por- poising motion… and that’s because they’re bloody close to being unstable.’ Next month… Going forward and going faster
The 80th Anniversary Mount Gay Round Barbados Race Series January 16th - 24th 2016
Three spectacular days of coastal course racing The Mount Gay Round Barbados Race The Ocean Passage Race to Antigua
Join us for Barbados’ ultimate sailing challenge Win your skipper’s weight in Mount Gay Rum Extra Old
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2016
www.mountgayrumroundbarbadosrace.com mount gay rum round barbados race
SEAHORSE 39
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