Mitre and Cross Cut Sails

Before we look at some of the latest sail designs, it's once again important to look to the past. As was the case with sail fabrics and yarns, if we understand how we got to where we are today, we will have some idea of where we might be going. Sail engineering is all about making good use of raw materials, both raw fibers and sailcloth.

Back in the days of square-riggers and trading schooners all sails were made in much the same way, i.e., with their panels laid parallel to the leech of the sail in what was referred to as a Scotch-cut pattern (Figure 4.3). This was true for both square sails and triangular headsails, despite the face that they were subjected to markedly different forces. Then in the middle of the last century a company by the name of Ratsey and Lapthorn Sailmakers, based in Cowes on England's Isle of Wight, realized that fill yarns had less stretch than their warp counterparts, and that this fact could be used to some advantage in terms of sail shape. Specifically, the company discovered that by rotating the fabric 90 degrees, it was suddenly able to achieve a moderate

MITRE-CUT HEADSAIL

Magnified section —

note yarns meeting at the miter on a bias.

Mitre seam on a heavy bias.

Figure 4.4

The panels meet in the body of the sail with adjoining panels cut at an angle to both the warp and fill yarns on what was called a heavy bias.

amount of leech control, something that had until that point eluded sailmak-ers. For mainsails, where two out of three edges are supported by rigid spars, they ran the fabric all the way across the sail from the leech to the luff in what came to be called a cross-cut pattern. For the headsails, which were only supported along the luff by a headstay, they ran the panels perpendicular to the leech, and perpendicular to the foot as well so that both parts of the sail would benefit from the stretch-resistant fill yarns (Figure 4.4). The panels met in the body of the sail with adjoining panels cut at an angle to both the warp and fill yarns on what was called a heavy bias. Fortunately, the middle of most sails is a low-load area so this bias didn't result in too much distortion, although it could be very difficult to get the sail to look good when there was so much opportunity for stretch. In the old days, when sailmaking was more art than science, sailmakers were often judged by how well they could sight and cut the mitre line.

As designs developed and sailmakers gained some say in the way fabrics were woven, they were able to get fill-oriented and balanced fabrics made that, depending on the aspect ratio of the sail, could be used to build increas

Figure 4.5

As sailmakers gained some say in the way fabrics were woven, they were able to get fill-oriented and balanced fabrics made that could be used to build increasingly efficient cross-cut sails, both headsails and mainsails.

Cross-cut Dacron sails are the most common sails seen on weekends as small cruising boats head out for a sail.

Cross-cut Dacron sails are the most common sails seen on weekends as small cruising boats head out for a sail.

CROSS-CUT MAINSAIL

In woven fabrics the strsngth runs across the hanels, i.e., in the hirection the greatest load.

CROSS-CUT MAINSAIL

ingly efficient cross-cut sails, both headsails and mainsails (Figure 4.5). For example, as Figure 4.2 on page 53 shows, a low-aspect sail like a No. 1 genoa of the kind used on an old IOR racer has the loads fairly evenly distributed throughout the sail. Therefore, if you had to choose a single fabric it would likely be a balanced one. If, on the other hand, you were choosing fabric for a No. 3 blade jib where the loads run right up the leech of the sail, you would definitely choose a fill-oriented fabric (Figure 4.6). As fabrics became more sophisticated and sailmakers gained a better understanding of their craft, sail designs improved, and the demands for better sails increased as well. The quest for light sails that did not stretch when they came under load remained a top priority for sail engineers.

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Responses

  • barbara austerlitz
    What is a miter cut sail?
    1 year ago
  • NIKLAS
    Is there any broadseaming cut on the mitre line if a headsail?
    10 months ago
  • rina mazzi
    What are mitre cut sails?
    2 months ago

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