image011If one does not know to which port one is sailing, no wind is favorable.

Twenty years from now you will be more disappointed by the things that you didn’t do than by the ones you did do… Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.
-Mark Twain

One ship drives east and the other drives west by the self same winds that blow.
It’s the set of the sails and not the gales that determines the way they go.
-Ella Wheeler Wilcox

We cannot direct the wind, but we can adjust the sails.
-German Proverb


PolySail International
High Performance/Low Cost Sails for Small Sailboats


By Dave Gray

All Rights Reserved


 White polytarp sails or PolySails are inexpensive polyethylene sails that are simple to construct and nearly indistinguishable from traditional sails in looks and performance. 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) 385-3444 or on our Products Pages).
  • 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. You will also need heavy weights for holding down the material, such as half concrete blocks. Outside you can use narrow tent stakes or large pole barn nails for stretching out the material on a lawn.

PolySails are constructed to take advantage of the materials’s strength, stretch, and resiliency. Polytarp or polyethylene is all around us today in everything from those flimsy-looking plastic grocery bags that still manage to hold a gallon of milk safely to Waste Management’s Bagster that holds 3300 lbs. of remodeling trash. And, like most of today’s sails, it is a light, strong synthetic that can be shaped without paneling into a high-performing sail. These instructions are based upon over 16 years of experience in constructing hundreds of PolySails. Simply follow the steps below to become a believer.

1. Lay Out the Material

Unfold the polytarp material and stake or weight the corners and edges.
image016 image017-1 image019



2. Lay Out the Sail Plan

image021-2Mark out the rough dimensions of the sail on the polytarp material with the kit’s dry-erase marker. If at all possible, orient the leech or back edge of the sail along the long side of the polytarp. This approach will allow the sail to stretch more where it needs to—along the luff—and help prevent the leech from stretching too much and flapping in the wind. Use a steel tape measure to make a straight line of dots between each corner marking a dot at each foot of measured length

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

Follow the designer’s sail plan to shape the sail’s edges. After you have marked the dotted baselines, use your tape measure or a long batten to mark a fair curve to the outside of the luff and foot baselines as shown in the illustrations below. These dashed lines are usually about 3”-5” from the baselines at the apex of the curve, at least for smaller sails up to 80 sq. ft. For larger sails, this rounding can be 6’ or more. Once the dashed “rounding” lines are in place, run double-faced tape along these curved lines in the luff and foot and along the outside of the straight or hollowed line in the leech. The diagrams below outline this procedure. Follow a similar procedure for 4-sided sails.

image025 image023-1Notes on the illustrations:
The illustrations shows a 3″ 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 near the end of these instructions.

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 polytarpmaterial, and the tendency of polytarp to stretch diagonally provide a natural wing shape to the sail.

4. Cut Out the Sail Shape


  • image026-1Use 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.
  • Fold and tape any V-Darts before cutting out your final sail shape. Note that finished V-darts will affect both the edge shape and edge dimensions.
  • Starting from any corner of the sail, work your way counterclockwise around the outside edge of the tape cutting out the sail shape with a pair of sharp shears.

5. Tape in the Reinforcing Rope

image028Once 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 all the corners. Install the reinforcing line at the inside edge of the tape in all sail edges working with one sail edge at a time. Tension the line and sail edges using the weights. Remove the tape backing along one edge and fold the taped edge back over the reinforcing line. TIP: Use less tension on the line in the leech to keep the leech from “hooking.” Double up the line on both sides at the head of the sail by leaving the backing on a small section of the tape on either side of the head until all the other edges have been taped. Finish by positioning the two ends of the line next to each other and sewing them together.

image0306. Fold Over the Edges

Secure the overlaps by running the handles of the scissors along the taped overlaps. Some tape experts even suggest hammering down the tape with a rubber mallet for better adhesion.
Acrylic-backed tapes such as those in our NO-SEW kit will especially benefit from the resulting tight bond.
If the adhesive loosens, run a zigzag stitch around the perimeter of the sail along the inner edge of the overlap to assure long lasting durability.



7. Tape the Corners

After the rope is covered and the overlaps folded down, reinforce the corners as shown in the diagram and photos. Add double-faced tape to the heavy tarp edge material to form 1 ½” wide strips of reinforcing material and place one of these strips in each corner of the sail and in reef corners. After positioning these reinforcing strips, the corners can be further reinforced with vinyl tape and with stitching. White vinyl tape is the standard, but colored vinyl tape is popular for customizing a sail to match a boat’s color scheme. Unlike polytarp sails with corner patches of polytarp material, this well-tested reinforcement technique prevents corner and reef grommeta from tearing out and results in very strong corners for our sails. Our finished and custom sails use larger rolled rim spur grommets in the corners for even more strength.

Note: Rubber-backed carpet tape alone will normally last for a few uses without sewn reinforcement, but this adhesive eventually dries out and loosens from the slippery polytarp surface. Double-faced acrylic tapes tend to bond better with polytarpsince the bond improves over time. If acrylic tapes loosen, they can usually be the material. These more expensive tapes are used in our NO-SEW PolySail Kit.


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