Directions for Making a PolySail

White polytarp sails or PolySails are inexpensive polyethylene sails that are simple to construct and nearly indistinguishable from traditional sails in looks and performance. Research shows that 5.5 oz. white polytarp material is about twice the breaking strength as ripstop Nylon and about three-fourths as strong as Dacron.

Using one of our White PolySail Kits and the following simple construction process, even a novice can create a taped PolySail within a few hours. Most customers are able to make a sail in the morning and be on the water by afternoon. Allow additional time for constructing and rigging multiple sails, large complex sails, and sewn sails.

Here’s what you need:

· A PolySail Kit (available from Dave Gray at PolySail International (317) 915-1454).

· A large, clean, dry, and open work space inside or out, e.g., lawns (but not with wet or freshly mowed grass), garages (but not with oily or dirty floors), clean driveways, large decks, gym floors, etc.

· A long, fairly stiff steel measuring tape to lay out the sail plan and stakes or large pole barn nails for stretching out the material on a lawn. On other surfaces use heavy weights for holding down the material, such as full gallon paint cans.

Sailmakers mainly use two methods to create the curvature (camber or belly) needed for sails to work. Professional sailmaking lofts create part of this curvature by cutting and shaping panels of cloth or synthetic material and then sewing these panels together. This part of the process is generally labor intensive and very expensive.

The second method involves cutting the edges in a curve. The more curve, the more belly in that edge of the sail. When the curve is straightened by a mast or the tension of a rope, shape is forced into the sail. This edgecut method probably preceded the “shaped panel” approach by centuries. We use this simple edgecut method along with carefully placed V-Darts on large sheets of white polytarp material to construct PolySails. Follow the simple steps below to construct a polysail.

1 Lay Out the Material

Unfold the polytarp material and stake or weight the corners and edges.

2 Lay Out the Sail Plan

Mark out the rough dimensions of the sail on the polytarp material with the kit’s dry-erase marker. (You can remove these marks later by rubbing them off with your finger.). Use the tape measure to make a line of dots or dashes between each corner. Sight along the measuring tape to make certain the baseline is straight and make a mark at each foot of measured length. These lines becomes the baselines. Do the same for each side.

3 Mark the Edge Curves and Insert V-Darts (If Needed)

Triangular sails have some edge “rounding” in the foot (bottom) and luff (edge next to the mast) to help create belly or fullness while the leech (back edge) is often straight or slightly “hollow”(curved inward). Four sided sails have rounding in the foot and head (top edge) and sometimes, as with a gaff sail, in the luff as well. After you have marked the baselines, use your tape measure to create a fair curve to the outside of the luff and foot baselines as shown in the illustrations below. These “rounding lines are about 3” from the baselines at the apex of the curve for smaller sails up to 80 sq. ft. Next, run double-faced tape along the new lines in the luff and foot and along the outside of the baseline in the leech.

Notes on the illustrations:

The illustrations shows a 3"- 4" cutoff at the head and tack of a triangular sail. The lower cutoff allows you to insert a V-Dart in the tack of the sail. The cutoff at the head simply allows the tape to be folded over properly. Instructions for forming V-Darts are included with each kit.

Certain triangular sails, such as the Leg O’ Mutton and lateen sails, do not require a V-Dart at the tack to function well. The combination of the edge rounding, rope reinforcing in the edges, the natural “wrinkles” in the body of the polytarp material, and the tendency of polytarp to stretch diagonally provide a natural wing shape to the sail.

4 Cut Out the Sail Shape

Starting from the tack of the sail, work your way counterclockwise around the outside edge of the tape, cutting out the sail shape with a utility knife or sharp shears.

PRECAUTIONS:

Fold and tape up any V-Darts before cutting out your final sail shape. Note that finished V-Darts will affect edge shape and dimensions.
Use the outside edges of the double-faced tape as a guide for cutting. Just open the scissors part way and run them along the outside edge of the tape to make a clean, quick cut.

5 Tape in the Reinforcing Rope

Once the sail shape has been cut out, fold up the excess material and remove it. Make certain that you have a clean place to work, then stretch out and weight or stake the sail at the corners. Remove the protective covering from the top of the double-faced tape and lay rope along the inner edge of the carpet tape all the way around the edges of your sail. The rope should be just to the inside of your exposed double-faced tape. At the head, the loose ends of the rope can be spliced, knotted, or overlapped and sewn together.

6 Fold Over the Edges

After laying out the rope, fold the edge with the exposed double-faced tape back over the rope and lightly smooth the taped edges down. Because this step gives you the final shape of your sail, make certain that all curves are fair and the sail shape is what you expected before you firmly tape down the overlap.

7 Tape the Corners

After the rope is covered and the overlaps are folded down, reinforce the corners as shown in the diagram. Add double-faced tape to the heavier tarp edge material to form 1 ½” wide strips of reinforcing material to place in each corner of the sail. For sails that will see heavy use, place one of these strips on each side of the sail at each corner. After positioning these reinforcing strips, the corners should be reinforced further with vinyl tape as shown in the diagram. White vinyl tape is usually preferred, but colored vinyl tape can also be used to customize a sail to your needs. This reinforcement technique results in very strong corners for our sails.

The tape alone will normally last for a few uses without sewn reinforcement, but all adhesives eventually loosen from the slippery polytarp surface. As a guideline, we use a rubber mallet to pound down and “set” all tape into the polytarp material. Then, we stitch around all the overlapped edges and reinforce the corners with even more stitching before adding grommets in the next step.

8 Add Grommets

In order to attach the sail to a mast or boom, place grommets into the tape at intervals along each side of the sail that will be attached to a mast, boom, or spar. These grommets have other functions, as well. They help hold the tape and internal reinforcing rope firmly in place and provide a means of varying the "belly" of the sail. Grommets should be spaced no more than 18" apart on a PolySail to avoid overstressing the material. Separate instructions for setting the grommets in the sail are included with the grommet kit that is a part of the regular PolySail Kit.

9 Attach the Sail to the Mast and Boom

Once the grommets are installed, you can attach the sail to the mast, boom, or spars in a number of ways. Our kits contain plastic cable ties rated at 75 lbs. that can have you out on the water quickly. If attached very loosely, these plastic ties will slide up and down the mast with a pull on your halyard. Later, you can replace these temporary ties with wood mast hoops, rope mast hoops, or the illustrated lacing technique to attach the sail to the mast. An even better luff tie technique is featured at http://www.polysail.com/lufftie.htm Attach the sail to the boom or other spar with a spiral lacing technique or by individual lengths of rope attached with a clove hitch at the grommet and a square knot under the boom. (See the knot-tying guide enclosed with your poly rope.)

Here is a picture of a finished jib-headed, sprit boom PolySail on my test boat Essence. (Some designers also call this sail a Leg O’ Mutton sail.) Only edge rounding and a single V-Dart in the tack were used to create shape in this sail, but note the nice curvature and lack of twist in this simple sail. For additional instructions on making specific sail types, visit our PolySail Library and sail database at www.polysail.com