Technical
It’s not just the tools...
... it’s about how you use them. And after 30-plus years of intensive development UK Sailmakers reckon they can use them pretty well!
U
K Sailmakers’ lead designer Pat Considine’s capabilities and skills in the use of state-of-the-art sail design software are at world-class
level. There are many things in life that you may know how to do... but can you do it on a world-class level? Sure, you know how to drive, but could you win a Formula One race? You know how the pieces on a backgammon board are moved, but can you beat a master backgammon player? You know how to sail, but can you win a foiling moth championship? Sure, your sailmaker may know how to
use a computer to design a sail, but does your sailmaker know how to make that design software perform at a level comparable with winning that F-1 race, making a living playing backgammon, or being the foiling Moth World Champ? Probably not. Considine has been working for UK
Sailmakers leading its Chicago loft for 30 years. Over the past decade, his design work has blended his intuitive artistry as a traditionally trained sailmaker with BSG Developments’ leading edge sail design software applications. BSG Developments is the leader in
sail design software providing a suite of related products. Perhaps their most widely used product is SailPack, the core design software that allows the sailmaker to configure a “mould” on which to “attach” the sail panel layouts after which
60 SEAHORSE
reinforcements and other finishings are added. The SailPack output is a three- dimensional model of the boat and its sail plan that can be viewed from any perspective. This allows the sailmaker – and the customer – to visualise the sail before the first panel is cut. When loading in the SailPack data, a vast range of data points are input ranging from sailcloth being used, mast/spreader/shroud specifications for optimised rig setup to yarn thread paths, deck layouts indicating where sails will be trimmed to hull, batten specifications, and hull/ballast characteristics. SailPack is an
excellent platform for primary sail assessments, but if the designer wants to further ensure performance levels, a fluid structure interaction (FSI) is required. BSG’s SailPack FSI is made in collaboration with K-Epsilon. This is BSG’s most advanced and accurate solution for FSI calculations, adding layers and layers of detail and understanding well beyond what the core SailPack delivers. Ideally, UK’s SailPack and eventual FSI modeling starts by importing the boat designer’s 3D composite images of the boat including the range of rigging, systems and nautical specifications that went into creating the yacht. Sometimes, the designers don’t like giving up those
‘Pat Considine is one of the few who can make SailPack FSI really sing’
files, so UK have to create the boat/rig model themselves from the sailplan and line drawing of the rig. Then they need to define everything they’re going to study including the characteristics of the mast so we know what to expect when we put on more backstay in different amounts of breeze. They go on to define the angle of the spreaders, composition of the shrouds, kinds of battens being used, etc. Polars of speed and angles also come into play. They designate where the jib tracks, inhaulers and travellers are, too. The SailPack design starts with a standard sail configuration. UK Sailmakers creates the “design shape” of the sail vs. the “flying shape” of the sail – when flying, a
sail can be trimmed in an infinite number of combinations that can’t always be anticipated by the designer. Trim, leads, inhaulers, halyard tension are all variables. By starting with the design shape, adjustments can be made to approximate various flying shapes using FSI. An example of flawed logic is that many people have tried to design a sail’s design shape that will twist around the spreaders but can never achieve that in the flying shape. FSI modeling starts with the detailed
data originally input for SailPack: models of sails and rigs, mechanical properties,
The sail design for a Santa Cruz 50’s light No1 alongside a photo of the actual sail flying – the two are virtually identical
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