Technical
In this study for a MAT 1180, inhauling gives a slight increase in the coefficient of lift. Even though the drag increases, in light to medium winds the boat will sail faster with the jib inhauled
delivered in the Mediterranean. We were able to give him a plan for setting the sails in a range of wind strengths (6, 10, 15, 20+) including detailed guidelines on mast bend, headstay sag, jib car/traveller positions, in-hauler setting, and more. When he set the sails for the first time, he knew exactly how to set up the boat and sailed away having benefited from our in- depth look at the flying shape for the sails we created using FSI. I’m pleased to say this customer was ecstatic with these guidelines...and the sails.’ It should be noted that UK Sailmakers
has applied the FSI technology in ways that will positively impact customers who aren’t buying premium-priced sails or looking to pay for FSI input for their new sails. One example of this is Considine’s work with the Chicago-based Tartan-Ten fleet. The Tartan-Ten is a 1978 33ft one- design with a 7/8 fractional rig and a non-overlapping jib. A popular class in Chicago, there had been one jib design that was winning all the races... but wasn’t able to point as high as desired. The specifications of the original jib were input into SailPack FSI and a baseline assessment was made using widely accepted inhauled settings. UK Sailmakers then created a number of new Tartan-Ten jibs, each with the objective of matching the current jib’s speed but pointing higher. The key was that the inhauler settings were evaluated for the old jib and the new prototypes. By varying the designed-in leech twist in the sail, a new jib was arrived at, meeting both the speed and height objectives. This new UK jib has revolutionised the Tartan-Ten fleet in Chicago and benefit of this this “twist” logic has trickled down throughout UK Sailmaker’s one-design and non-overlapping jib designs ever since... bring the benefits of FSI to all their customers. Importantly, UK’s use of FSI isn’t an
empirical exercise where once the design is out the door, the designer moves on to the next project. Definitely not! In fact, there is as much information flowing back up to Considine and his design team as flowing down. UK’s sailmakers report back
62 SEAHORSE
Above: in the 16 knot image the runner tension is increased which adds mast bend, flattening the main, increasing twist and depowering it. The jib is depowered by moving the jib car aft, which adds twist in the sail
on the real-world, on-the-water performance results from sails output from FSI. Here is art informing technology both before and afterwards. Considine explains that in changing FSI
model inputs, it’s not as if you can see the sail shifting shape in real time. ‘The minute shifts in performance data as loads change positions, leads and trim are adjusted, and conditions change can only be realised from the data... making this part of the process more technology than art. Look at the data points in these exhibits and you will get a feel for how precise and subtle the improvements are projected by FSI. Subtle changes in where the JPK owner set the leads for his new
sails, subtle changes in the shape and trim of today’s winning Tartan-Ten jibs, subtle changes in the properties of the materials used to build a sail. This is where the technology is required to access and evaluate these often imperceptible differences,’ he says. Without that technology, we would not
have the sails we have today. However, without the artistry of a sailmaker to create the original design concepts, the technology alone would be lacking. That’s why it takes people like UK Sailmakers’ Pat Considine, Barry Hayes, Stuart Dahlgren, Pedro Gianotti and others to provide today’s needed blend of art and science.
www.uksailmakers.com
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