Carbon Sails and
During the last two years two of the biggest changes in sailmaking have been the wide acceptance of asymmetric spinnakers, and the increase of the use in carbon fiber sail materials. Both changes are quickly working their way down through all levels of sailing.
Carbon fiber became legal for general use in sails in December of 2000 after long debate regarding the durability and price of carbon in sail materials. Dimension / Polyant Sailcloth has lead the way in producing new lines of carbon fabrics available as standard items, that have both good durability and pricing that makes them very competitive with aramid fabric. They have done this by producing carbon warp sheet fibers bundled into flat ribbons that while on the low end of modulus for carbon, still have a higher modulus than aramids. By laminating them in a system that doesnÃ¯Â¿Â½t infuse the fibers with resin they have produced a fabric has both excellent flex properties, and very low stretch. Carbon is also unaffected by Ultra Violet. For this reason carbon is exceptionally well suited for use in paneled sails.
We have been building sails using these fabrics for two years, and have been very impressed with their performance and with their durability. In that amount of time they have shown less change in shape than comparable aramid sails. The advantages we see are better long term shape holding, and much better long term strength. Any aramid sail will loose between 40% and 50% of its strength over the first year due to flex and UV degredation, while the carbon fabrics loose between 20% and 25% during the same time period. The carbon sails are also somewhat softer in feel due to the non-resinated fibers and seem to hold up better to impact. Because of the excellent resistance to UV breakdown the sails will have a much lower chance of catastrophic failure as they age.
Price wise they are quite competitive. Currently in the lighter weight styles a finished sail will run 8% to 10% higher in cost but as the weights go up the price difference goes down. When you reach the range of "sled" type mainsails or heavy jibs the carbon sails are actually slightly less expensive. We expect to see the carbon become even more competitive in price as the volume of cloth, and numbers of suppliers go up.
The only downside to carbon is that it is presently not available in as wide a range of styles and weights as the aramids, which means that in some cases the sails may be slightly heavier than can be built using grand prix aramids. This should change over the next 6 to 9 months as the carbon product lines are increased. The sails do also require slightly different construction methods. Carbon and stainless steel are not compatible. Stainless rings in carbon sails do rust and corrode, so we donÃ¯Â¿Â½t use any stainless fittings in our carbon sails. Corners are finished with either titanium rings or spectra straps. On sails that need a snap shackle in the tack we have developed a spectra loop and toggle to replace the traditional fittings. We have also perfected a method of building the corner reinforcements by widening out each radial gore as it comes into the corner. This way all of the strength is built in as an integral part of the sail, not as a series of patches that are added on. The corner is stronger, lighter, and conforms much better to the shape that is built into the sail.
A bigger change in the type of sails now being used is the switch from symmetrical to asymmetrical spinnakers. A spinns are generally faster and easier to use than symmetric spinnakers. There is a very slight tactical advantage in gibing symmetrical spinnakers in running conditions, but it is more than overcome with the increased performance of asymmetrics. And gibing asymmetrics is certainly easier and safer, even if it does take a little more time to get ready.
Along with the switch to asymmetrics has been the introduction of a new set of spinnaker terminologies. By now IÃ¯Â¿Â½m sure you have all heard the "code" designations, but may not be that sure about what they actually mean. Basically odd numbers are reaching sails, even numbers are running sails, and the infamous Code 0 is a specialty very tight reaching sail.
Code 1: For light air reaching. It is for basically the same conditions as what you now know as a VMG spinnaker, going downwind in conditions light enough that you have to sail tighter apparent wind angles, 60 to 90 degrees apparent.
Code 2: Medium air running. It is used in the same conditions as a symmetrical AP spinnaker, 90 to 135 degrees apparent, for going downwind from 8 knots to 20 knots.
Code 3: Medium air reaching spinnaker. Used for reaching in 10 to 20 knots apparent, the wind angle where you can carry it will vary with wind speed but generally between 70 and 110 degrees apparent.
Code 4: Heavy air runner. Full size, used for running in 20 to 30 knots.
Code 5: Heavy air reaching for over 20 knots.
Code 6: Storm runner for over 30 knots.
Code 0: The Code 0 is a specialty tight reaching sail, and can also double as a heavy air spinnaker. Current rules require the midgirth to be at least 75% of the foot, which is meant to prevent making a 180% genoa and calling it a spinnaker. (On a genoa the midgirth has to be 50% or less of the foot) They are made with the luff as close to straight as possible, and the shape as flat as possible, without having so much roach on the leech that it flaps too much. In light air they can be flown with an apparent wind angle as tight as 40 degrees.
Early asymmetrics were generally made as reaching sails. It wasnÃ¯Â¿Â½t until the introduction of the pole boats that a lot of work was done on running asymmetric spinnakers. The concept of the long sprit instead of a movable pole brought new challenges to the sail designers to develop a new generation of asymmetric spinnakers. We started a concerted effort 2 years ago in the J105 Class, and while it is still on going, the results have been very good. The J105 Class in an excellent platform to work with because the spinnakers are built to an area rule rather than a specific set of measurements. We found that by varying the plan form for a given area we could produce a much better running spinnaker. Our spinnakers are generally shorter on the foot and leech, but bigger on the midgirth and quarter girth with more luff round. This produces a sail that rotates out to weather better and has more area exposed to weather. It was interesting to see the new North spinnaker
built the week before the Lipton Cup was substantially different than their standard J105 spinnaker, and had dimensions very similar to ours.