Making New Sails for Beowulf

	Here and below are three images taken aboard of the new mainsail. Note how nicely the top of the mainsail twists off the leeward - even in these light airs. Steve & Linda can now get all of the telltales, even those on the top batten, to flow when beating or close reaching.

Making new sails for Steve and Linda Dashew is always a mixed blessing. They know exactly what they want. Accordingly, we end up with a thick file of notes and detail drawings that require extra time and attention from our design and sail production teams. But in balance, we invariably come away from the job with new ideas and a better understanding of how bluewater sails are used.

This summer we built replacement sails for Beowulf's mainsail and mizzen. The sails we replaced were the original sails built for the boat about 5 years and 28,000 miles ago. These original sails were designed and built from drawings, while the boat was under construction. The fit and detailing was close enough that the sails only had to come off the boat once, in New Zealand, to replace the back end of the batten pockets where the battens had chafed through. But after living with the sails for 5 years, the Dashews had a list of things that could be improved. And we were anxious to give it another shot with the benefit of measurements taken from the rigs as they were set up in real life. Following is a list of their requested changes and our solutions:

Sail Profiles

Steve wanted more sail area on the same spars. We added 6" to the leech length of the mainsail and 10" to the leech length of the mizzen. We were able to add 2" to the luff length of both sails because the Dashews replaced the 2:1 halyard blocks with new, lower profile hardware. The largest addition of area was in the roach above the midpoint of the leeches. The new sails have very aggressive roach profiles at the head, resembling the sails used on the Americas Cup class boats.

Sail Shape

The Dashews wanted more open-leeched sails that could be sheeted harder without creating as much drag for sailing to windward. The objective of a more open-leeched sail, coupled with the very aggressive roach profile, creates a problem for the sail designer. The easiest way to support extra sail area (sail area outside a straight line drawn between the corners) is to add depth to that part of the sail. On the high roach sails that we build for the Sundeer boats, the additional depth has to be balanced with the cloth stretch along the leech. With more than half the length of the sail batten behind the straight line, wind pressure on the leech area has the effect of leverage to stretch the sailcloth, causing the leech to get more "open", or flat. If the sail designer errs on the side of making the sail section too shallow the sailcloth might stretch enough to remove all the camber in that part of the sail, and the batten will collapse to leeward, causing an S-shaped cross section. If the sail designer makes the mistake of too much camber, the sail will be tight-leeched in lighter winds.

Another view of the mainsail. A key factor in figuring out how agressive we could go on the roach was ease of getting the sails up and down the mast. With America's Cup and Whitbread sails, the head of the sail must be removed from the mast when the sail is stowed. That is NOT the case with these - they furl just as nice as the old ones.

Rich Bowen was the sail designer for these two new sails. Rich did some of the detail work on the initial inventory of sails for Beowulf. He and Kenny Read came sailing with us before the new sails were designed so that we could get a feeling for the flying shape relative to the design shape of the current sails. In about 17 knots of wind, we had Steve and Linda set up the boat and we measured the mastbend under load. Kenny identified a "hard spot" in the mainsail mastbend that was causing the sail to invert at maximum bend, but otherwise we were happy with leaving the rigs alone and making the new sails to fit them.

Rich took this information back to his computer and ran comparisons of the original sail designs and luff curves with the measured mast bend curves. He then modified the original designs so that they more closely fit the real-life mast bend. The second step in the redesign was to make changes to the broadseaming of the initial sail designs (which we call "molds") to address the differences in cord shapes that Steve requested. At this stage we had molds that we would have used if Steve and Linda wanted new sails of exactly the same size as the original sails. The minor changes to the edge lengths were then changed with a matter of a few fields of input.

Once he had the shapes, luff curve and size of the sails to this starting point, Rich modeled an IACC roach on the mold. Because Beowulf's sails are much more low aspect than an IACC rig, the roach had to be modified in the lower half, and then the sail cords adjusted to address the much greater upper girth. Finally, Rich ran the sails through a series of fairing runs, to insure a smooth vertical transition of the horizontal cord sections that he was working with.

The shape and depth of the completed sails is very close to the ideal that we were shooting for. The new, larger roach area appears to be adequately supported, and the boat seems to be responding to the added horsepower with improved performance in all directions. But the very large upper roach does not come without a price. When the sail is unloaded, with little pressure on the sail to stretch the fabric, the head sections are deep and tight in the leech area. The added area and the difference in depth of the unloaded sail make it flog more erratically than the previous sails, with their more balanced roach curve. Because the Dashews regularly sail onto and off their anchor, the manner in which the sail flogs is a concern.

Fabric Selection

The first set of sails was built using Bainbridge Sailcloth's SCL line of spectra fabrics. This fabric was selected because of its rugged combination of woven taffeta skins covering mylar film and a "scrim" layer with large Spectra yarn in both directions. The tradeoff with the scrim-based fabrics is that they are incrementally heavier and stiffer than the alternative, woven category spectra fabrics. For the new sails we selected North Cloth's Gatorback Spectra line. The Gatorback Spectra fabrics have been improved recently with larger dacron filling yarns. The size of the dacron yarn used in the "nonload" direction of the fabric is significant because these yarns are often the first to degrade from UV exposure.

The new sails were also ordered with only one set of reefing points while the first sails had two sets. (The Dashews elected to leave off the first reef and keep the second, higher reef for storm conditions). The combination of the more high performance fabric and deleting a reef set yielded weight savings in the area of 10%. Reduction of weight also means reduction of bulk, so the new sails lay flatter on the booms at rest.

Construction Detailing

Most of the construction specification on the first sail inventory was successful, so we stuck with it. Here are a few things that we changed:

Batten Pocket Chafe Protection- On the first sails we used a very heavy UHMW (ultra high molecular weight) plastic sewn over the batten pockets wherever they came into contact with the standing rigging. The plastic did its job but it dried up and cracked after years in the sun. For the new sail we used a lighter weight UHMW and covered it with an adhesive backed dacron cloth. The dacron will wear away right where the contact with the rig occurs, but will protect the plastic, which is protecting the pocket, everywhere else. The pockets themselves are made from a woven spectra material.

Slide Reinforcement- Just before the first sails came off the boat; the mainsail broke behind the lowest slide grommet. For the new sail we made sure that the lowest slide (just above the tack) and the slide just above the reef tack were in the way of reinforcing layers that extended farther into the body of the sail. In addition, we attached these slides and the slides directly above them to the sail with progressively longer loops of webbing than the other slides. These slides take a large portion of the clew loading if the main halyard stretches or slips and the luff gets loose. By increasing the offset of these slides we are ensuring that the slides won't load to the point where they rip out of the sail.

Steve's comments: "Did someobody ask for a flat sail? We've always had a battle between the ability to control the roach on the top of the sail and draft up high. We want the roachy profile, but also want the sails flat. Until recently, you had to have enough draft to make the sail stand up. So, we paid an excess draft penalty to get the profile and area we desired. However, with the new sails, as you can see, we get our flat shape and our roachy profile. This is a much faster configuration, and one which loads the the keel less, tacks faster, and heels the boat less. We'll be recommending these new sail shapes to the owner's of our various designs as they are ready for new sails."

Single Line Reefing- We changed the setback of the tack reef hardware to accommodate Steve's plans to modify his reefing setup to single line reefing. The tack reefs are set up with triple web loops that can be pulled to either side of the sail, through a pressed ring, to facilitate the attachment of a turning block.

With the reefs so far up the leeches of the sails, there is a problem of containing the very long loop of reefing line that flies behind the sail when it is raised and lowered. If the line is allowed to fly around it can catch on antennas, radar units, deck gear or peoples necks. To address this we added reinforced grommets along the leech of the sails and tied stainless "O" rings through the grommets using small diameter shockcord. Each leg of the reef line is passed through a ring and the shock cord keeps them close to the sail.

Headboard Slides- The first main and mizzen for Beowulf had simple stainless rings at the head with 2 plastic coated stainless slides shackled to each head ring. The slides were lashed together with seizing wire. This is not a very neat looking arrangement but it did work. For the new sails Steve wanted a longer bearing surface of slide material at the head. Our solution was to use Antel headboards with aluminum Scheafer luff slides, scavenged from one of their batten end fittings. We thought that the luff slides could be coupled with the Antel headboard carriage part but the pin sizes were not compatible. Our quick fix of lashing the new, longer slides directly to the headboard did not work. So Steve is currently struggling to find a way to couple the old plastic coated stainless slides with the new headboard.

Most boats of the size of Beowulf have track and car systems (Harken, Antel or Frederickson) on their masts. Beowulf has been through enough miles with simple luff slides to prove that the setup is valid. The problem is that there are not any standard parts made to address the high loading at the heads of these sails. This could be an example of the "if it ain't broke don't fix it" line of thought, but hopefully by the time Beowulf leaves again for the Caribbean we will have worked out a nice clean solution.

Batten System

The first sails were delivered with solid rod fiberglass battens that proved to be great in a blow but too stiff for light air coastal sailing. Those battens were replaced with Bluestreak brand, rectangular vinylester resin battens. The Bluestreaks were better in light air and marginally too soft in breeze when the sails had to be feathered. The new sails are equipped with RBS brand epoxy resin battens. The RBS battens are very resilient and stiff for their weight battens. The battens are laid up in flat sheets, cut into rectangular sections and then ground to the specified taper. The battens are fitted into new Scheafer Marine adjustment boxes at the luff end. These very nicely machined alloy parts represent an extension of the Sailpower batten hardware developed by Russ Foster.

(To read how these new sails perform, and to see more photos, read the Dashews' September 6 report.)