Polytarp sails

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Polytarp sails refer to sails constructed from rectangular polyethylene tarpaulins. Home boat builders often favor these synthetic "sheet" sails because the materials are inexpensive and easy to assemble into functional, durable sails. The usual construction method involves: laying out the tarp material, measuring the sail dimensions, creating baselines from corner to corner, placing double-faced carpet tape around the sail outline with sufficient rounding on selected edges to shape the sail, placing a reinforcing rope along the inner edge of the tape, and folding the taped overlap back over the rope to create the sail shape. At this point, the amateur sailmaker can choose to strengthen the sail by adding reinforcing material to the corners and/or stitching around the edges of the sail. The sail is then finished by adding grommets to the corners and edges in order to attach the sail to the mast and spars. Because these grommets are placed through at least doubled material and behind the reinforcing line inside the sail edge, the resulting attachment points have tremendous strength.

The most attractive, durable polytarp sails are usually made from a heavier white polytarp material. Sails made from this heavier "canopy grade" white material are often called polysails to distinguish them from sails made from the lightweight blue or other colored polytarps available in many retail stores. These sails are often difficult to distinguish from traditional sails out on the water. Generally, polysails are made from white ultra violet-protected (UV-protected) material that is 12-16 mils in thickness and weighs about 6-8 ounces per square yard--about twice the weight and thickness of the common colored tarps which usually have no UV protection. The density of the weave of polyethelene strips in the inner layer of the material also helps to determine the quality of the material. Common tarps will have a weave of about 6 x 8 of these polyethylene strips per square inch in the inner layer of the three layers of material that make up the tarp. "Canopy grade" white polytarps, on the other hand, have a weave of 12 x 14 or 14 x 14. Increasingly, white polytarp is used for the construction of mainsails, jibs, and mizzens, while the lightweight polytarp materials are reserved for making spinnakers.

Polytarp has been used to construct nearly every type of sail. However, the material seems best suited to traditional sail types such as sprits, lugs, gaffs, gunters, lateens, junk sails, and jib-headed sprits. Polytarp sails are less suited for sails that depend upon being highly tensioned, such as the marconi or Bermuda types of triangular sails. A wealth of additional information, including instructions for constructing a polytarp sail, can be found on the Internet by searching under "polytarp sails."