Sailmaker's log

Development work for Rio

Posted by Mikko Brummer on Tue, Aug 09, [email protected] 04:16 PM

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For London 2012, WB-Sails made a big research & development effort, mostly centered on Star sails. With the Star out of the Olympics, our R&D focus between 2012-2016 has been much on the Finn, but also on the 470. These two are the only Olympic classes left for which independent sailmakers are still allowed to design sails.

Obviously, most development work has been around sail shape, but also about sail materials (cloth, battens, lines, fittings etc.), mast shape & bending, and the 470 centerbord & rudder. If you thought that keeping up with the cutting edge is easy, take a look at the following list:

  • Hundreds of hours of video, from the mast head and outside, over Finn & 470 sails
  • Motion analysis of Finn & 470 in waves & pumping downwind
  • Thousands of simulation hours in the computer, tens of Terabytes of data
  • The EU sponsored PRACE-project over sail CFD (computer fluid dynamics)
  • A new lightwind Maxx material for Rio with Contender
  • A new membrane sail for Finn with Incidence Technologies
  • A novel Finn mast with Illy Brummer & Heol Composites
  • A new Finn headboard with Rutgerson & Axxon composites
  • Very special carbon battens for 470 & Finn with BlueWorks in Finland
  • A new 470 centerboard with a special structure, together with the Swedes
  • 470 centerboard case slot details with the Finnish
  • A comprehensive study around X-35 sails

And much more. From the list you can see that we have kept ourselves busy within the Olympiad. Some of the innovations are now sailing in Rio, some, despite the huge efforts spent, have proven to be dead ends. Or perhaps something to build on in the future.

The following is mostly a pictorial showing examples of various subjects covered, with comments above the illustrations. The splash screen image is about turbulence around the Finn sailing upwind in light airs "Sailing in whipped cream". The simulation is done in the TAITO Supercomputer at the Center of Scientific Calculation (CSC) in Keilaniemi, Espoo, as a part of the EU PRACE-Shape project. The illustration below ditto.

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This photo shows the lamination of membrane Finn sails - the sail is laminated in one piece, then Laser-cut into smaller panels, which again are assembled into a sail with an ultra-sound welding machine.

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Testing the membrane sail against "traditional" Maxx sails. If you look close you can see the video camera at the mast top, for recording the sail shape from the horizontal stripes.

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Turbulence around the 470 sails (and crew) with the boat pitching in waves upwind in 20kn+. The sail force varies in a little over one second cycle by some 50%, but in the average the sail forces are close to flat water conditions. It would not be impossible that sail forces in waves would be even more than in flat water - then the sails would be harvesting energy from the sea, transmitting it into aerodynamic forces.

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Our principal CFD partner has been Next Limit Technologies in Spain, through theirthe leading edge Flow simulation software XFlow . Some of our work is featured at the home page:

A parametric model of the 470 for downwind simulation. All aspects of the sails design can be varied through numerical control, with an excel-like interface, to allow quick evaluation of systematic changes.

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The computer simulated spinnaker featured in a photo on the World Sailing front page.

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470 centerboard structural simulation. The stiffness of the board has a big influence on performance, and the aim is to get the bending such that it helps to propel the boat forward when loaded in waves or through deliberate crew motion.

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Measuring the bending & the twist of the centerbord under a realistic sailing load.

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Differently shaped boards simulated in downwind position. The tolerances on the centerboard are very tight, but you can always do something with the shaping of the tip and the edges. The structural considerations are more important, though, than the centerboard profile shape, strickly controlled by the OD-rule.

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Scanning the Finn mast shape with a laser scanner at ENV France. All existing popular masts were scanned, to get a benchmark for our own mast design.

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Flow around the Finn mast at a section about 1/3 up from the deck. The computer simulation reveals, that the mast section shape is not a very importanta factor. You can think of the mast as part of the sail area, and the more efficient the mast is the more it disturbs the sail behind it. So it's a zero-sum game. The bend characteristics of the mast are much more important for the performance than its aerodynamic shape.

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Carbon fiber battens & headboards, and a new ultra hard aluminium headboard with Rutgerson in Sweden.

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A headboard designed a bit too light, twisted in heavy air testing.

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Partnership for Advanced Computing in Europe, PRACE, to enable European SMEs (small & Medium sized enterprises) access to supercomputing. This project is on-going until the end of the year. Our partners are the Center of Scientific Calculation (CSC) in Keilaniemi, Espoo, and Next Limit Technologies in Spain. Next Limit are the developers of the leading edge Flow simulation software XFlow, examples of which you can see in this blog.

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The TAITO supercomputer at CSC is a 16 cabinet HP cluster with 17704 cores in total. Your regular PC may have 2 cores, or 4 if you are lucky.

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In addition to all the Olympic work, we managed to find the time (somewhere) for a very comprehensive development project around the X-35 One-Design, with our partners X-Sail Racing Team. With respectable results, I might add, 1st & 2nd in the 2015 Worlds in Copenhagen (there wasn't but 2 boats with WB-Sails in the fleet).

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Mikko Brummer has been simulating sail flow and performance in the computer since 1977, and has since long heard to the leading experts in the world, when it comes into sailboat aero- or hydrodynamics.

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Topics: Finn, Olympic sailing, Sail aerodynamics, Sail design, 470