By Dave Gray
HR Solutions/PolySails 

I've been messing about with polytarp sail construction for about nine years and selling polytarp sail kits under the name of PolySails for over half that time. During that time, I've probably cluttered up my mind with way too much information on polytarp sailmaking, old boats, and online marketing as nearly any visitor to my PolySail website can attest. To make this proliferation of data even worse, I try to dream up tests for the tarp materials I supply in the kits. I also send out surveys to people who buy kits from me to learn what they think about the polytarp sails they make. Of course this obsession makes a convenient scapegoat for lapses of memory, an overflowing job jar, and a failure to sock away adequate funds to retire even by 90. Fortunately, I have a forgiving wife and a family history of eccentricity to fall back on if I really get desperate for excuses about spending time with polytarp sailmaking.

The gist of what I've learned so far is that some kinds of polytarp make pretty damn good sails for some people who just want to mess about with small boats. Now immediately some readers will think to themselves, "Well, he's just a biased so-and-so who wants to drum up some business," or some similar thought. So I'm going to admit from the outset that self-interest is 90 percent of the reason for writing this article and sharing what I've learned is only about 10 percent of my motivation. After all, retirement is looming; and a part time income from selling sail kits is better than no income at all.

Let me clarify what I mean by "some kinds of polytarp make pretty damn good sails..." Polytarp is generally made from three to four layers of polyethylene. The inner layer is woven from strands of the same stuff, but the weave can be very loose or fairly tight. Only when the weave is fairly tight is the polytarp material much good for sailmaking. Much of the common blue polytarp that you buy from your friendly home improvement store has only about a 6 x 8 scrim, or weave, per square inch. My white and light gray tarps have at least a 12 x 12 scrim and a 14 x 14 scrim if I can get it. In terms of weight and thickness, the cheap polytarp might be only a 3 mil; 2.5-oz./sq. yd. material while the better grade is an 8 mil, 6.0-oz/sq. yd. material.

Another differentiating factor is color. White and some other light colors of polytarp tend to be U-V (ultra violet ray) treated. Dark colors are not. If you've ever used one of those cheap blue tarps outside for a boat cover for a season (if it holds up that long), you might know what happens when one of those tarps disintegrates. The darker, lightweight tarp tears at a touch and rains down microscopic flakes of tarp that are harder to get rid of than head lice. On the other hand, a marine firm that supplies the 14 x 14/sq. in. scrim, light-colored tarps to the US Navy has to meet a standard that their tarps will last for at least one year in any weather conditions. One of my white tarp boat covers is now in its third year with no patches or visible signs of deterioration except that the bright white color has dulled somewhat.

I've attempted to do some backyard tests on the polytarp I offer versus some other plastic types of material other people have tried for sailmaking. One is the popular house wrap Tyvek and the other is a pond liner material that a West Coast business uses in sails and kits they offer. I used a spring loaded fish scale to check stretch on the warp, weft, and diagonal. The polytarp showed the least tendency to stretch each direction. I also used a 16-penny nail attached to a small postal scale to measure how much force was required to penetrate the materials. The polytarp offered about twice the resistance as the heavier pond liner and considerably more resistance than the house wrap. However, I'd highly recommend keeping all these materials away from sharp objects if you are planning on using them for sails. Of course, I'd follow that recommendation with any sail material unless you just like that patched-up look.

To check the strength of the white polytarp material, I supported a 42 lb. battery on a 3' x 4' piece of white polytarp that I suspended from a couple of two by fours with six nails, three on each side. If my calculations are correct, the force exerted by the battery is about ten times more than would be exerted on the material by a gale force wind under the Beauford Scale. Even so, I wouldn't want my customers to test their sails or their luck in that kind of wind. For more detailed information on this particular test as well as other tests I've tried, check my web site at  

Earlier, I qualified my thesis by saying that some kinds of polytarp make good sails for some people. If you are a big boat, long-range ocean cruiser type, or one of those overly serious club or class racers, then polytarp sails are definitely not for you. Similarly, if you are of those Wooden Boat aficionados with a fat wallet, a penchant for classic boats, and friends in high places; then tarp sails probably seem like a travesty to you and your commercial sailmaker.

I usually get to talk with people who are buying my kits, unless they simply decide to pay online. Most of the time, I try to find out what kinds of boats they've built or what kind of boat will carry their finished sail(s). Of the folks who buy my kits, it turns out, many are novice builders and sailors. (I have to insert here that messabouters are universally nice people to work with.) Their projects are smaller boats with one sail, or at most, a jib and a main. Inevitably, their boats have unstayed masts they've built themselves, too. I speculate that as these builders get near the end of their initial boat projects, they start calculating how much more they spent than they intended on their boats--and how much they still might have to invest in a functioning sail. That's about the time that many of these folks start seeking out a less expensive alternative and end up calling me.

There also appears to be a group of customers who just want to be able to say that they've constructed everything, including the sail, all by themselves. For some reason, this group of customers seems to be dominated by professionals--you know, doctors, lawyers, consultants, etc. I'm always a little puzzled about why someone with an MD or PhD attached to the name would want a cheap sail kit. That's one question I probably won't be asking in my surveys, though.

Another group of customers seems to be made up of experimenters. A customer from this group usually buys a kit with the idea of making more than one sail from the material. This customer expects to find the best sail shape(s) for his or her boat, with the idea of developing a completely unique sail and/or upgrading to a "real" sail later. 

Recently, Sam Hamlin, a teacher at the Shore Country Day School in Massachusetts, contacted me for material to make nine D-4 sails for the boats his class of 15-year olds had constructed. We were able to work out a deal using the "economics of scale" so that the sails cost considerably less than $40.00 each. This was the second school order I've processed; and, as a former teacher myself, I'd like to reach far more of this group of "customers." 

For the last two years, I've sent out surveys with self-addressed, stamped envelopes to everyone who purchases these PolySail kits to get feedback on product quality and service. (My real job often involves evaluation projects.) The response rate was a phenomenal 38% last year and 30% (so far) this year. Altogether that means 36 individuals took the time to fill out this survey. (Those numbers should tell readers that this is not a high volume or high profit business - just in case one of you was considering selling polytarp sail kits.) I asked 23 questions in four categories that covered everything from the ordering process to the performance of the finished sails. Customers could also add comments and did not have to respond to all questions, but most did anyway. In the interest of space, I'll try to sum up their responses.

Everyone who responded was very positive about the service and the product. I got high marks in the categories of Price/Value and Ordering, Shipping, Handling, and Packaging. Nearly everyone thought the kit was fairly priced, advertised accurately and fairly, and would consider purchasing another kit if the need arose for a new sail. One customer suggested that I didn't need to include some items that were duplicates of items already owned by most messabouters, such as the utility knife and measuring tape. Another person said he would probably buy all the kit materials locally if he could find the white polytarp. Everyone responded positively to the questions about how we handled their order and questions.

Another category where we asked questions was identified as Instructions/Construction. Here we asked about problems following the generic instructions, construction time, and whether customers stitched or taped their sails. All but two of the customers responded that they had encountered no major problems following the generic instructions or using the kit materials. Of the remaining two customers, one reported problems making the tapes adhere in high humidity areas such as Florida and suggested that we warn others of this potential problem in the instructions. Another customer indicated that we had allowed too much for the shrinkage of taped edges, reporting that his sail ended up four inches too long along one side. When asked how the instructions could be improved, one customer recommended more diagrams, while another suggested a short video. Most customers, however, seemed to agree with the people who said, "They worked for me!" or "Instructions were fine."

Construction time was a major variable, depending upon the number and complexity of the sails, and whether the edges were taped or stitched. Most of the fledgling sailmakers reported taping their sails and said the construction time was about 4 hours or about what our ads had led them to expect. One poor fellow reported taking 16 hours to construct a taped jib and main for a 12' dinghy. A couple making a jib and main for a Weekender said it took them a full day to complete. Another man reported 8 hours of construction time. No one else reported over 6 hours construction time. At the opposite end of the spectrum was Steve Bosquette, a customer who reported taping up three sails for his schooner in only two hours. I think that's quite a feat.

Chuck and Sandra Leinweber's Caprice 

The fourth category was identified as Performance/Appearance. I first asked about the kind and size of the sail(s) customers were making. Again, the responses were highly varied. Shipp Webb of Sewanee, TN made a little Leg 'o Mutton sail for his small canoe that couldn't have been much over 10 sq. ft. Chuck Leinweber and his wife Sandra, on the other hand, used up a 550 sq. ft. PolySail Kit to make a 200 sq. ft. lug main and a 30 sq. ft. mizzen for Pearl, their Jim Michalak-designed Caprice. Sprits, Bermudas, lugs, gaffs, junks, crabclaws, lateens, jibs, mizzens, genoas, spinnakers - our customers have made them all from polytarp. Occasionally, I'll find that the material was not used for sails at all. Paul Gray noted that he had built a roof for his kids' playhouse. Others have made bimini tops, boat covers, and temporary boat-building shelters. Our most common requests, though, are for kits to build sails for the Stephenson Projects' Weekender or one of the many Phil Bolger designs that uses the 59 sq. ft. Leg 'o Mutton sprit boom sail.

The survey next asked what kinds of boats the sails powered. Once again, the responses were many and varied. Up to the time Chuck Leinweber told me of his plans to use PolySails on his Caprice, all of the boats that I knew carrying PolySails were within our recommended limits of 20' and 1000 lbs. I think that, as sailed, Chuck's boat was pushing those limits at 25' and about 1300 lbs. with three crew aboard. Smaller Bolger-designed boats, such as the Brick, Teal, Featherwind, and Surf are among the more popular boats using PolySails. Jim Michalak's designs also carry their share of polytarp. However, PolySails have also been constructed for a 14' Lund fishing boat, a 14' West Wight Potter, an 11' Capri, a customer-designed 19 1/2' sharpie, and a 20' Trimward? Kayak. While I have yet to get a response from catamaran owners, I know several kits have been ordered for cats, as well. Each call, it seems, broadens the list of applications that are possible. The limits of the material are still being tested, with doubled polytarp offering further possibilities for heavier boats.

When we asked if the sail performed as well as the customer expected, the answers were nearly all positive from those who had actually had a chance to try their sails. (Some northern customers who responded were still ice-bound when the surveys went out.) One first timer reported a "hard experience," but that was our only negative response. Some sailors said the performance was "fine,""better than expected," "exceeded my expectations," or "surprisingly effective." Most simply answered "yes."

A similar question asked if the sail measured up to their expectations in appearance, and whether they had received any comments from others. Again, most responses were positive. The fellow from Florida who had trouble with the tape adhering offered the only outright "no" response. Others would probably agree with Don Williams of Olympia, WA who responded, "Yes. However, I was not able to make it wrinkle-free 100%." Other comments ranged from, "That's a tarp!" to "Could not tell that they were not Dacron." One man stated, "It looks great. It would be perfect if sewn." Another said, "Appearance is good. May be heavier than necessary, but don't know if lighter material would hold up." Another customer said, "People are stunned that I made them myself."

Only a few of our customers were sailors experienced enough to respond to the question about whether PolySails were comparable in performance to commercially made sails. Five who did respond replied "yes" to the question; however, one of the five qualified his response with "...relative to price/value."

I also asked questions about the adhesion of the tapes used in construction and the overall durability of the sail. It was clear from five of the customer responses that the vinyl tape tends to lift after a period of time. How soon that happens depends a great deal on the location of the customer, the relative humidity, how the sails were stored, how often the sails were used, whether the sails got wet, and other factors. One customer responded, "I regret not stitching the sail. After wet storage, the [vinyl tape] edges came undone." Another said, "The vinyl tape did not stick all that well. I would have liked it to be wider." Still another customer reported, "Tape has let go in last four months since sail construction." Two other customers whose projects (not sails) were constantly exposed to the elements reported that the double-faced tape failed after a year of exposure. However, most of the builders, including four of the ones that reported troubles with the tapes, responded "yes" when asked if the sails were as durable and long lasting as they expected. "Only used one season, but seems fine," was the description by one customer. Another commented, "Hasn't fallen apart yet," while still another customer said, "Tape stayed put, even though we didn't sew the sail." The man in the middle seems to be the fellow who said, "Vinyl held almost all season."

I recognize that the vinyl tape presents some adhesion problems, as does the double-faced tape offered in the kits. However, our backyard tape tests demonstrated that only a very, very expensive tape offered better adhesion than the vinyl tape we were using. Of four double-faced tapes we tested, the brand we supply held best in our weather conditions. Stitching the sail perimeter still offers the best long-range results, but taping is great for getting a new boat out on the water or trying out a different sail plan.

For people who like to mess about with homebuilt sailboats, polytarp sails offer an inexpensive, easily constructed means of powering a boat. As Emeliano Marino, author of The Sailmaker's Apprentice, wrote, "Perfectly acceptable [dinghy] sails can be made from Tyvek, polyethylene tarp, London Fog raincoat material, bag nylon, or tent canvas, not to mention old sails. Tarp or Tyvek sails may be taped together and require no sewing." If my surveys are representative of just my customers' views, there might well be over 100 polytarp sailmakers from the USA, Canada, and Australia who agree with this veteran sailmaker. And judging from the number of hits on my website instructions, there could be hundreds more.

(If you want to try your hand at making a polytarp sail, see the instructions on my website at  or call me to order a kit at 317 915-1454.)