Spinnaker Fabrics

While the advances in spinnaker fabrics have not been as dramatic as we have seen in the fabric for working sails, there have in fact been some subtle improvements, mostly in terms of finish. Nylons are not set with as much heat so there is quite a bit of bias stretch, but ever since fabric makers started to weave warp-oriented nylons specifically for tri-radial sails, this bias stretch has not been as much of a problem. Spinnaker nylon comes in a number of weights including 0.5 ounce, 0.75 ounce, 1.5 ounces, and 2.2 ounces. The actual finished cloth weighs about a quarter ounce more than these designations.

For spinnakers that are used for reaching where there is still quite a bit of attached flow, low stretch and an aerodynamic shape are important and sailmakers have been using laminate scrims and light Cuben Fiber. These fabrics are relatively heavy, but the trade-off between low stretch and extra weight is a reasonable one, especially on a reach.

This is fine for light spinnakers. Once you get into heavy-air sails, however, the fabric needs to have some give. A spinnaker that collapses and refills does so with a large amount of shock loading, and that load has to go somewhere. It's better that it be

Figure 8.4

To remove horizontal panels from radial spinnakers, a new generation of spinnakers with panels oriented along expected load paths were created.

Modern spinnaker designs are becoming more complex with panels changing direction to match the loads in the sail.

Modern spinnaker designs are becoming more complex with panels changing direction to match the loads in the sail.

absorbed by the fabric than transmitted onto the sheets, halyard, and mast where it could possibly do some real damage. Light-air reaching sails are less likely to collapse and refill, so stretch resistance is key to good shape retention and speed. As soon as you bear away onto a reach or run, the apparent wind drops, and loads on sails are dramatically reduced. The loads on the body of a spinnaker with the wind from behind are fairly minimal, and therefore stretch resistance can be traded for give in the fabric that will absorb shock loads.

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