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Thread: Polytarp Sailmaking

  1. #1
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    Smile Polytarp Sailmaking

    I know that sails and sail plans are not the most interesting part of boatbuilding for most of you, but sails are the engines that drive sailboats, and they are getting more interesting all the time with all the colors and options available for polytarp-powered, homebuilt boats. If you are interested in seeing some of these options or following the day to day sail builds of an experienced polytarp sailmaker (17 years), I post photos and comments on nearly every sail I build on my Facebook Page at: https://www.facebook.com/pages/PolyS...11967352175070 Take a look at the timeline or photo albums to see some of these options and perhaps expand your horizons about sails.

    Dave Gray

    PS: I know polytarp sails have been roundly criticized on this site, but perhaps seeing some of these finished sails will alleviate some of that criticism--but, probably not...

  2. #2
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    Default Re: Polytarp Sailmaking

    It's true that some of the sails appear perfectly suited for some of the boats.

  3. #3
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    Default Re: Polytarp Sailmaking

    Polytarp Sails fill a real need for an economical and easy way to build a sail. Obviously they are not suited for all types and sizes of sail. All too often criticism is a case of the 'perfect being the enemy of the good'. There is a polytarp sail or two in my future when I finally get around to building some experimental rigs for my dinghy collection.

    A rather interesting PolyTarp Sail Link:
    http://www.thecheappages.com/oddsails.html

    Mass to FL on a strict budget:

    "Yep. Real polytarp sails on a real (errr, tob-o-plastic) sailboat.
    They got Cap'n Freddy from Massachusetts to Florida. He couldn't afford anything else.
    So why can't you rig your little craft with something made from tarp? Oddly enough, many older and traditional rigs are either insensitive to sail cut, or just plain flat-cut. The batwing, dipping lug and the crabclaw are examples of the latter. Bermudian sails are probably the toughest to whip up from tarp."
    Last edited by George Ray; 05-07-2013 at 10:38 AM.
    This is the first lesson ye should learn: There is so much good in the worst of us, and so much bad in the best of us, it doesn't behoove any of us to speak evil of the rest of us.
    E. Cayce

  4. #4
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    Default Re: Polytarp Sailmaking

    When I was a kid I built a sail rig for a 12-foot aluminum fishing boat we had, added a couple of leeboards and a rudder made of plywood, and a mast made out of an old tent pole. The sails were made from clear polyethylene sheeting and held on with shower curtain rings. It sailed pretty good considering, though didn't tack too well--it wanted to go straight.
    Kettlewell Cruising

    Do just once what others say you can't do, and you will never pay attention to their limitations again.--Capt. James Cook

  5. #5
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    Default Re: Polytarp Sailmaking

    Oddly enough, many older and traditional rigs are either insensitive to sail cut, or just plain flat-cut. The batwing, dipping lug and the crabclaw are examples of the latter. Bermudian sails are probably the toughest to whip up from tarp."
    Much of that statement is either just plain not true or very misleading. I think it would be more accurate to say that many older and traditional SAILORS are insensitive to sail cut. The thing that you need to understand, even with the few types of sails which actually are/were flat-cut (and dipping lugs are not among them) is that these sails are not flat in use. Older sails that were cut flat were usually done that way because the stretch (especially bias-stretch) and stability of the cloth itself was so high that the sail would essentially stretch to it's desired shape in use. With modern, drastically more stable materials (including to an extent polytarp) this does not happen nearly as much, if at all, so the shape (draft amount and location, twist, edge tensions, etc.) must be designed and built into the sail from the beginning. It is then altered in terms of adjusting broadseam amounts by the stability of the particular cloth used (harder, firmer, more stable cloth needing more broadseaming and shaping than somewhat softer, less stable cloth). You simply can not have a meaningful discussion on sailshape or start making generalizations without considering the materials being used - and generating the same exact in-use shape with different materials can, and does, often require different amounts of designed-in and sewn-in shape.

    As for polytarp, I have no complaints with the material or its use for cheap sails as long as (1) the user understands that it is not premium sailcloth and never will be. It does not have the stability, stretch resistance, durability or lifespan that real sail fabric has. You get what you pay for.

    and (2) as long as the basic principles of sailmaking which make sails that work properly are not ignored. Unfortunately, an awful lot of the people building polytarp sails, and also those who are "teaching" others via the internet how to do it are totally clueless on some of the most simple, most basic and most important aspects of what goes into any decent sail. This often includes what is arguably one of the most important things a sailmaker needs to know - what direction to point the damned fabric in the first place. Polytarp "material" is actually very similar to some of the Mylar/scrim laminated sail fabrics. The difference is that the tarp is made with the cheapest possible raw materials and brings the physical limitations of those materials into the equation. The sailcloth scrims are often made using some of the most expensive materials available for increased stability and durability and with that, they also bring higher prices into the equation. The actual construction of the sail using either material (cut, shaping, reinforcement, panel and fabric layout, etc.) is, or at least should be, surprisingly similar. I probably sound like a broken record, but I am literally amazed at how often I have to remind people on this forum that in order to build a good sail that sets decently, works decently and will live up to the potential useful lifespan of the materials used (whatever they are) you have to study and know at least the basics of sailmaking. Some hack making polytarp sails by the seat of his pants (including a couple of well known boat designers) is not going to be able to teach you what you need to know when he doesn't know it himself.

    I have looked at Dave's albums, and though I will likely never be a big fan of the material itself and may question its true value in terms of lifespan and durability vs. labor time and cost, I do see a lot of stuff there that I like in terms of things being properly constructed. Unlike many, he is practicing real sailmaking. If for one reason or another polytarp makes the most sense for your project, that would be a good place to start looking.

  6. #6
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    Default Re: Polytarp Sailmaking

    I've cut a couple of experimental sails from polytarp, ironically using information gleaned from Todd on this forum over the years, including a Crab Claw rig and a shower curtain balloon spinnaker . It's cheap and you can have some fun. But I make no claims as to their real efficiency.

  7. #7
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    Default Re: Polytarp Sailmaking

    I've been dabbling in sailmaking for use on small boats for a few years now. When I first started I read as much as I could and decided that I would start off using heavy duty white poly. My reasoning was that it wouldn't cost much and any failures could be tossed without too much regret. What I didn't realize was that the same amount-of-work/cost-of-materials equation that bedevils the decisions of many wooden boat builders also applies to sailmaking. My first effort was a success but now after only five years of moderate use the sail is stretched out and slowly losing the high stress grommets in the peak, clew and tack, despite copious reinforcement. I learned that sailmaking is a straightforward but labor intensive process so skimping on materials is foolish, just like in boatbuilding. I also found some sources for inexpensive sailcloth. After building a couple of sails out Dacron I was surprised to discover that Dacron only is about 50-60% more than white poly. Had I spent a couple more bucks, I would not be currently building a replacement sail. Given the low durability and heavy weight of poly, I can see no reason for even a novice to use anything but real sailcloth.
    Last edited by Dusty Yevsky; 05-07-2013 at 07:52 PM.

  8. #8
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    Default Re: Polytarp Sailmaking

    Yup, I agree Dusty,
    3.8 oz white dacron is less than a dollar a square foot from Duckworks.

  9. #9
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    Default Re: Polytarp Sailmaking

    The one good thing about polytarp sails is if you see one coming, you've got some warning to give a wide berth to whoever's sailing it.

  10. #10
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    Default Re: Polytarp Sailmaking

    I side with those who believe they have a place. I made a simple lug sail for my canoe, of blue polytarp and clear duct tape. It cost eight dollars and took perhaps an hour to "build". While it certainly did not last or perform like a "real" sail, it went to windward and back. It cannot be equalled in economy of time and money.

  11. #11
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    Default Re: Polytarp Sailmaking

    I have made quite a few small boat sails from discarded "big boat" sails.
    Spritsails, lugsails and jib-headed main sails (Gunter, Solent lug) were all pretty good. It was always the limitations of the hulls and appendages that were the real problem. Most small boat forms designed to row or paddle have limits. But for goofing around they were great fun and a good learning experience. You will learn that a sailmaker earns his money...

    Usually free, and so much better than any tarp, they are a better economy.
    With some carefull selection you can find one that has both shape and quite a bit of life left in it.
    And it won't be blue -

  12. #12
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    Default Re: Polytarp Sailmaking

    See, it's the "one-hour" thing that bugs me the most. If you do a decent job and attempt to design and build a sail that really does work properly, no matter what it's made from, it's going to take considerably more time than that just to do the design work - and that doesn't count the time spent studying to learn the basis you need to be able to do that design work in the first place. If it's cut, constructed and reinforced properly - even with duct-taped seams, you should be busy assembling your creation for a day or more. I'm pretty efficient after 33 years of building sails, but it still takes me a couple full days of work to design, lay out and build a small one-off lug or lateen sail. If it didn't need any stitching and could just be taped together, I might save half a day, tops. Is this a case of people who have so little knowledge of how sails and sailboats are supposed to work that they actually believe that their sails work, or do they have such low opinions of their boats and their quality that they believe anything that kind of looks like a sail must be one and will work "just fine"?

    I got into sailmaking after working on hot-air balloons for several years, where every seam, its type, size, stitch type, thread weight, needle size and even the number of stitches per inch are regulated by the FAA and the manufacturers with no wiggle room allowed. Building sails is a much less stuffy and much more creative process, but I never thought I would see so many people intent on building their own sails without ever bothering to learn even the basics of how to do it first. It's a good thing that they don't allow that with balloons - or there would be a lot more dead pilots out there.

  13. #13
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    Default Re: Polytarp Sailmaking

    If you are going to go "cheap" on a wooden boat, try an inject a little class into it. When I was a kid, I bought a canvas paint tarp and made my Lateen Rig from that and leftover "ballet bars" (my dad had a part time job maintaining a Ballet Studio in San Francisco to pay my sister's tuition). I didn't know anything about making a foil shape. I just copied the layout I found in a "Young Mechanic" magazine. I went to windward without knowing the terminology in my leeboard equipped scow on the bay. Had lots of fun. You don't need a perfect foil shape to generate lift to point. You will of course give up performance.

    You can still buy canvas paint tarps. Like any canvas, you can't stow them when wet, but they otherwise are easy to sew, and don't look horrible, even if you botch the sewing. Blue paint tarps don't belong anywhere outside. They have zero UV resistance and all they are good for is keeping dust off a car in a garage.

  14. #14
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    Default Re: Polytarp Sailmaking

    I have never, ever regretted using top quality materials in my small boats. I have, however, at times bitterly regretted some of the short cuts and cheap-out fixes I've tried to take when they turned around and bit me in the ass under vigorous use. No more for me, thanks. Quality is worth what it costs.

  15. #15
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    Default Re: Polytarp Sailmaking

    How about prototyping a sail? I intend to build a whole new rig for Matty, but really have little or no documentation to work off of. I could see putting together a simple tarp sail to establish that a size of sail will be suitable, or cutting down or adding area as needed, and then putting forth the time and money for a proper sail.

    Or perhaps tapping the knowledge of the designer and the knowledge here would yield just as useful information. I suppose some math is just as good or better than a crappy practice sail.
    There's the plan, then there's what actually happens.

    Ben Sebens, RN

    15' Welsford Navigator Inconceivable
    16' W. Simmons Mattinicus double ender ​Matty

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    Default Re: Polytarp Sailmaking

    Quote Originally Posted by BBSebens View Post
    How about prototyping a sail? I intend to build a whole new rig for Matty, but really have little or no documentation to work off of. I could see putting together a simple tarp sail to establish that a size of sail will be suitable, or cutting down or adding area as needed, and then putting forth the time and money for a proper sail.

    Or perhaps tapping the knowledge of the designer and the knowledge here would yield just as useful information. I suppose some math is just as good or better than a crappy practice sail.
    Why not just copy Tim's sail plan Ben?
    -Jim

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    1934 27' Blanchard Cuiser ~ Amazon, Ex. Emalu
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    Getting into trouble one board at a time.

  17. #17
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    Default Re: Polytarp Sailmaking

    Big Food is a very different boat from Matty. Big Food is a John Gardner design, while Matty is a Walter Simmons design. Big Food is shorter, heavier, and has a harder turn of the bilge than my 16', light, round Matty. I dare say Im also a bit more bold than Tim, although that's probably just my naiveté showing.

    Jim_cricket is building a balanced lug rig for Mouse, the Mattinicus he just launched, which will give me a good idea of what will work. But I'm sure our preferred use and style may dictate some changes.


    All that said, I'm probably way over-thinking it.
    Last edited by BBSebens; 05-08-2013 at 11:14 PM. Reason: More blabbing.
    There's the plan, then there's what actually happens.

    Ben Sebens, RN

    15' Welsford Navigator Inconceivable
    16' W. Simmons Mattinicus double ender ​Matty

  18. #18
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    Default Re: Polytarp Sailmaking

    Quote Originally Posted by BBSebens View Post
    How about prototyping a sail? .
    You will still need to properly design and construct the prototype. If it's one-off it makes absolutely no sense to prototype. You are simply doubling the amount of work you have to do and it's already a lot of work to make just one. Read Todd's "Canoe Rig", Marino's "The Sailmaker's Apprentice" and the Sailrite series. You will have enough information to design a good sail and do it right the first time. Incidentally, sails are easy to tweak after initial construction and test runs so there really is no good reason to prototype in poly.

  19. #19
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    Default Re: Polytarp Sailmaking

    Prototyping in materials other than what you finally plan to use can be pretty inaccurate. Let's say we have a dinghy and we want to put a simple lugsail on it, or maybe switch from a Bermuda sail to a lug. It's certainly possible to learn some things about how the lug will work and what it would be like to handle it, but counting on the prototype to accurately indicate any sort of performance levels or generate any accurate tuning tips isn't likely to happen.

    I've even victimized myself before by doing this. Our trimaran came with the typical working jib and about a 135% Genoa, both in Dacron. When we lived in Illinois and sailed on smaller lakes, we used the Genoa most of the time. When we moved here where we were sailing on a lake that's five miles across, we found that the boat sailed better in the bigger chop with the jib. I built a fancy new Mylar Technora radial main and working jib. The following season, I figured I'd build a new Mylar Genoa to go with them. At that particular moment, it was winter and the boat wasn't assembled, so rather than measure the boat (which is what you should do) I just used the old Genoa as a prototype and measured it instead. It had always worked fine and there was no reason to anticipate any problems. I built a new tri-radial, computer-plotted and cut Mylar Genoa to the exact same measurements as the old Genoa. The next spring I ended up having to move the Genoa tracks about a foot to get the sheeting angles right for the new sail. It was due to the stability/stretch differences between the Dacron and the new Mylar laminate. Despite being a real sail in good condition, the Dacron sail didn't make a suitable prototype.

    On small boats, we have had decent luck switching rigs and keeping the CE and sail area very close to the originals. It may change the sailing characteristics some, but doesn't usually overpower the boat or make drastic changes in the handling. There is a point though, where you start getting into righting moments and other technical stuff that really needs to be addressed by someone who knows what they are doing - and who also has accurate measurements on the hull. If at all possible, the original designer is usually the best person to check with if you're making any sort of drastic changes in the rig and/or sail area.

  20. #20
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    Default Re: Polytarp Sailmaking

    On Papua New Guinea's north coast, poly tarp sails are pretty common - in fact, I can't recall seeing anything else there used for sails. The fishermen there paddle and sail their tiny `sit on top' dugout outriggers many miles out to sea in the wee, small hours and then ride the seabreeze back to shore when it kicks in, around midday. The poly tarp sails don't seem to last very long but I don't really know how long they do actually last. They all seem to have been built from second hand scraps, although they may just look that way from their many repairs.

    Where I live, in Australia, I see a lot of old sails, often in pretty good condition, being dumped or used as things like painting drop sheets. I've often wondered whether it would be viable to collect a whole bunch of old sails and send them to PNG. I know they'd make very good use of them. What do sailmakers in other places do with old sails?

    Rick

  21. #21
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    Default Re: Polytarp Sailmaking

    I’m an advocate of polytarp sailmaking. I like the idea of having an inexpensive polymer laminate material that can easily be shaped into sails, perform adequately, and get boat builders, youths, and others on the water quickly, especially novices to the sport who are easily put off by nautical jargon and those who seem to support the sport’s reputation for yacht club exclusivity. The idea that sails have to be made to formulae that have been around for years or from stitched panels is just so much puffery. I’d submit that paneled sails are primarily constructed that way because, unless you are a force in the industry and can afford huge laminating rollers and pressers, you are pretty much limited to bolts of synthetic materials like Dacron that are only 54’ wide. You have little choice but to panel your sails and shape them within those material confines. That is not to say that wonderful, high performing sails can’t be made that way. (Todd, for example, does outstanding paneled sail work.) However, today, paneled sails are considered by some to be little more than relics of antiquity that play second or third fiddle to the really high end complex synthetic laminates coming from firms like North Sails and Dimension Polyant. Why not insist that “real” sails need to be seamless, thermo – molded in one piece, with yarns all mapped according to computer assessed wind loads? http://www.youtube.com/watch?v=jKwV6F3_Hl4

    My point is that sails can be constructed from a wide range of materials with a wide range of prices and a wide range of performance and durability characteristics for particular purposes. And, by the way, not all tarps are made from blue, non-UV-protected 2.7 oz. polyethylene containing a 6 x 8 strand/sq. in. scrim and purchased from the local big box store. Demands placed upon Pacific Rim manufacturers for canopy grade material has led to some decent polytarp laminates for sailmaking if one has taken the time to understand the product.

    Polyethylene is an oil-based, polymer that is the basis both for Dacron and poly(ethylene) tarps. In its PET form as Polyethylene Terephthalate it yields a tough, stiff polyester woven fiber we know as Dacron. In its PE form as either HDPE (High Density Polyethylene) or LDPE (Low Density Polyethylene), it yields everything from plastic drinking glasses and tableware to thin films used for packaging and other purposes. We see it as filmy plastic grocery bags that hold more than we would guess and as laminated “Bagsters,” Waste Management’s name for its huge poly bags that can hold up to 3300 lb. of construction debris. Somewhere between these two extremes are the various weights, grades, and characteristics of various polyethylene tarps. At the high end are the tough canopy grades that are waterproof and resistant to all chemicals but oxides and feature closely woven 14 x 14 scrims, UV protection, 6.0 oz. weight per true sq. yd. (not the 28.5” x 36” sailmaker’s yard for Dacron and other sail materials) multiple colors and stripes, limited stretch, great resiliency, high durability, fewer wrinkles, and a more cloth-like hand. At the low end are the aforementioned blue big box store tarps.

    Here are what I see are the most obvious advantages of using good quality polytarps for sails. 1 Polytarp comes in big sheets that stretch enough on the bias that there is little need for seaming or darting, so paneling could be regarded as superfluous. 2. With tarps, you can easily control stretch by going up in weight. I find that the 5.2 oz. (multiply by .79 to get the equivalent weight in Dacron) or the 6.0 oz. are good weights for most of the sails I construct. 3. You can make a sail quickly once you learn how. It takes me about three hours or less to make a sewn 59 sq. ft. Bolger leg o’ mutton. 4. In my limited experience and based on tales from others, the sails often perform as well as similar sails made from Dacron. 5. Depending upon their use, polytarp sails are fairly durable. As one gentleman on this forum said, he got (only) five years from his tarp sail. I would observe that if he made another polytarp sail, he could get ten years out of his two sails, and probably still have less invested than in one Dacron sail. 6. The sails can be sewn on a home sewing machine (or, if you don’t like to sew, you can tape one up and it will do passable duty until the spring rains or the summer sun cause the tape to loosen. It surprised me to learn that a couple of sailors had managed to sail the entire Texas 200 with their taped sails. 7. For groups or organizations involved in boatbuilding on a limited budget, a 20’ x 30’ polytarp and a few other supplies can make a lot of sails inexpensively. 8. You can learn some things about sailmaking with laminated materials (as opposed to woven materials) when you make a polytarp sail. 9. Since it’s a polytarp sail you made, you have the option of attaching the sail to your mast with plastic zip ties and getting out on the water even faster. In fact, you can probably build yourself several polytarp sails to experiment with while your tradition-minded boat buddy is waiting for his Dacron sail to be delivered. 10. You might attract others to sailing who have finished building a boat then discovered that a new sail will cost more than the boat cost to build.

    Polytarp sails will probably remain largely in the domain of messabouts rather than sailing clubs, Duckworks rather than West Marine, and entry level sailors rather than old salts. But I feel they fill an important need if our sport is not to fall victim to too much in-breeding.

    Dave Gray

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    Default Re: Polytarp Sailmaking

    I think I could go along with most of that, until you got to the panel width part. The reason that sails are made with narrower panels is so that their shape can be placed accurately and held in that position without relying on stretch (bias or otherwise) to generate that shape. With modern materials, you simply can't expect to get consistent, predictable shape through cloth stretch unless you have built a whole bunch of the same sails with the same fabric. The typical one-off builder has no clue how much stretch the material will have in that particular configuration, which means that he would have no means of placing his draft where he wanted it or shaping the sails leading edge/angle of attack (which can often make a drastic difference in how the sail sets and how hard it is to get it trimmed properly and maintain that state).

    When designing a sail, we can calculate the total amount of broadseaming that we need along an edge. We can use the broadseam curve to place the draft properly, the luff round to add a specific amount of extra fabric to form draft and the amount of total broadseaming needed to move that extra fabric to where it needs to be to make the draft (which will vary and be based on the stability of the particular cloth being used). This amount will be similar whether the sail is paneled 12" wide or 54" wide. The difference is in how much each available seam will be broadseamed to make up that total amount. Most of what I build is narrow-paneled (12"-18") to maintain the traditional look, but it also allows me to use smaller/narrower broadseam amounts, since there tend to be so many available seams to spread the total amount needed over. I believe it also gives me a smoother shape, since the total amount of broadseaming isn't all just being crammed into only two or three seams joining wide panels.

    If you look at something like a Bermuda or Marconi main with a fairly long luff, you really start to see the importance of having several seams striking the luff and the whole idea of making the sail with very few panels quickly falls by the wayside. Take a fast beach cat and an iceboat, for example. The fastest mainsails for light, easily accelerated boats like these will generally have pretty shallow draft, placed fairly far forward, but they may have very different entry angles right behind the mast and leading up to that draft amount. The beach cat may have a highest top speed with a very shallow and/or flat-ish entry angle, but it will rarely have one. The reason is that at those speeds, the boat is rapidly going through changes in windspeed, water conditions and apparent wind angles. Trying to keep a flat-entry mainsail trimmed properly in those conditions and rapid changes is extremely difficult. Essentially, your VMG will be better if you cut those sails with a more forgiving, rounder entry (which requires multiple luff broadseams (or curved, panel shaping seams in the case of computer-cut sails). Your top end speed may be a bit lower, but your time from point A to point B will likely be less because your sail was trimmed properly for more of your sailing time. The iceboat may be a different story and a flatter entry may be a better bet. The reason is that the boat is so fast that it is essentially creating a great deal of its own apparent wind (like 50 knots of boatspeed in 15 knots of wind). A variation in that fifteen knots of wind has less effect on the 35 knots of gained apparent wind, so the steering/trimming tends to be less touchy and it is easier to keep your flat-entry sail trimmed properly.

    If your sail is going to have and maintain reasonably consistent shape and performance these days, you can't rely on cloth stretch to provide it. The shape needs to be designed into the project from the beginning (unless you're building in something truly mushy like cotton) and to build that shape, you are going to need some panel seams. The more there are, the more you can distribute it among the various seams and the smoother and more controlled that shape will be. There is absolutely no question that you could build a better polytarp sail from six or eight panels than you could from one or two, because you can shape it more accurately and consistently. It is a very basic principle of sailmaking and sail performance and something that just about every polytarp sailmaker needs to learn.
    Last edited by Todd Bradshaw; 05-09-2013 at 03:42 AM.

  23. #23
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    Default Re: Polytarp Sailmaking

    Quote Originally Posted by polysail View Post
    4. In my limited experience and based on tales from others, the sails often perform as well as similar sails made from Dacron.
    In my fairly long term experience and based on direct observation and experiment, this is not particularly true. Your disdain of panels is based on a fallacy too, as Todd Bradshaw amply demonstrates.

    A simple polytarp sail is precisely analogous to a simplified, hard-chine plywood sharpie. They both try to simulate a complex, sophisticated curved object with only a few facets and panels. Even though they might look similar in silhoutte, they ain't the same where it really counts. They might serve well enough to get someone started, I suppose. But don't delude yourself that it's anything more than it actually is, especially if you're ambitious.
    Last edited by James McMullen; 05-09-2013 at 07:28 AM.

  24. #24
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    Default Re: Polytarp Sailmaking

    Jim, you're a nice guy, but there is room for every kind of boat and sail. Some (not I) would disdain your boats because they are plywood. Some seem to think that if you can't afford the time or money for the best, you should stay ashore. I don't want a PDracer, but I admire them as I admire fisherman in poor nations that make sails of burlap. I wouldn't put polytarp sails on Wandering Star. I also wouldn't spend the time or money for a professional sail as an experiment on my canoe. You and Todd apply high standards as craftsmen. That's great. But not everyone requires those standards. There are many boats sailing with tarp sails that would otherwise not sail at all. That makes tarp sails a very good thing.

  25. #25
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    Default Re: Polytarp Sailmaking

    And many of those boats don't sail worth a damn - and usually not due to the material used for the sails. It is what it is and it is impossible to make a case for it being anywhere near as stable or durable as real sailcloth because it clearly is not, so don't even bother trying. It simply shows how far you're willing to lower your standards. Be that as it may, the greatest fault with polytarp sails is nearly always lack of sailmaking knowledge by the person building them and clear violation of some of the most basic design principles needed to produce a sail that actually works decently.

    Anybody with a lung-full of air can blow up the bag on a set of bagpipes, squeeze it with their left arm and make sounds. They might even have fun doing it, but I wouldn't call it music.

  26. #26
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    Default Re: Polytarp Sailmaking

    I can see your point, John. But let's go into it with eyes open. A polytarp sail has serious limitations that are not just snooty fictions based on the snobbery of yachtsmen.

    Also, only some of the boats I build are plywood. I actually far prefer the artistry and satisfaction of building in trad. lapstrake and trad. carvel over any of the goo-related forms of boatbuilding, but sometimes must choose to use different techniques to achieve specific goals.

  27. #27
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    Default Re: Polytarp Sailmaking

    Using plywood as an analogy here is is not quite right.
    Now if one advocated building a boat using sheets of translucent plastic shower paneling and duct tape that would be a better analogy.
    Plywood, in spite of all the nay-sayers is still wood, it just has some additional engineering properties to consider. And these can be used to advantage (or not) but expense or skills required should not be insinuated.

  28. #28
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    Default Re: Polytarp Sailmaking

    Quote Originally Posted by polysail View Post
    As one gentleman on this forum said, he got (only) five years from his tarp sail. I would observe that if he made another polytarp sail, he could get ten years out of his two sails, and probably still have less invested than in one Dacron sail.
    I should have clarified my statement. I used that sail for perhaps 15-18 outings and then it seriously started to degrade. Seven layers of sewn corner patches were not enough reinforcement to prevent the tack, clew and peak grommets from pulling out of the sail. The sail is also stretched way beyond the original planform. And this sail was made with quality 6oz white poly, not BBS blue. It was always dried and stowed indoors. Two days of work for 18 outings, hmmm. I can only conclude, based on my own experience, that poly is not a good material for sailmaking. Perhaps if you are eking out an existence in the grinding poverty of a third world country then poly is certainly a great material. But if you blessed to live in a first world country, where the vast majority of people have more money than time, then poly is a poor choice.

    Dave, the OP, points out that I could build a white poly sail every five years and still save money over Dacron. This misses my point entirely. I could build a sail out blue poly every two years and save even more. But I don't want to spend all my time re-building sails. I think my time is valuable. I want to do a job right and do it right the first time if I can. I want to maximize the efficiency of my amount-of-work/cost-of-materials equation and produce something with the most utility. The relatively small difference in the cost of poly vs. dacron is drastically mitigated by the large amount of work involved in building a proper sail, be it poly or dacron.

    Quote Originally Posted by polysail View Post
    The sails can be sewn on a home sewing machine
    a decent home machine can easily sew mutiple layers of 4oz dacron

    Quote Originally Posted by polysail View Post
    while your tradition-minded boat buddy is waiting for his Dacron sail to be delivered. 10. You might attract others to sailing who have finished building a boat then discovered that a new sail will cost more than the boat cost to build.
    Dave the OP, seems to be implying that only a pro can make a dacron sail. This is simply untrue. Taking into account the extra sewing of panels on a dacron sail the workload is only about 25% more than a poly sail. If you have the means to build a poly sail, you also have the means to build a dacron sail.
    Last edited by Dusty Yevsky; 05-09-2013 at 12:44 PM.

  29. #29
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    Default Re: Polytarp Sailmaking

    Quote Originally Posted by polysail View Post
    I’m an advocate of polytarp sailmaking. I like the idea of having an inexpensive polymer laminate material that can easily be shaped into sails, perform adequately, and get boat builders, youths, and others on the water quickly, especially novices to the sport who are easily put off by nautical jargon and those who seem to support the sport’s reputation for yacht club exclusivity. The idea that sails have to be made to formulae that have been around for years or from stitched panels is just so much puffery.
    I've never disputed Todd's expertise as a sailmaker, though I've never met him and never seen a sail he's cut, because over many years and having known well a couple of nationally renouned sailmakers, I've learned that sailmaking is not merely a craft but also a high art form and a science, the latter moreso in recent times with computer aided design and synthetic laminate materials and construction techniques. There are few sailmakers because it really requires a special skill set that isn't easy to acquire.

    I suppose there's a bit of merit to "getting boat builders, youths, and others on the water quickly," (not least of all being that they buy WB magazines that otherwise wouldn't be published for lack of a large enough readership) but the simple fact of it is that "novices to the sport who are easily put off by nautical jargon" are simply people who lack sufficient commitment to the endeavor to progress beyond their own fantasies. Those who enable such novices to mistakenly believe they know what they are doing do them a disservice. Those who think that there are "those who seem to support the sport’s reputation for yacht club exclusivity" really betray their own lack of experience with the enterprise entirely. The only "exclusivity" anyone is going to find in a yacht club these days is the high price of membership of a very few of them. Overwhelmingly, yacht clubs are happy to get all the members they can and "exclusive" isn't in their vocabulary.

    So, yes, building a first boat out of chain store plywood and adhesives and an old bedsheet for a sail (the custom back in the day before cheap blue tarps) in a "Huck Finn" sort of way can inspire a youngster to move on towards real seamanship, but those who feel slighted by those who are less than enthusiastic about such "accomplishments" are blind to their own limitations.

    One can certainly "have fun" building "boats" with polytarp "sails," as well as all sorts of other inferior materials and construction techniques, but no matter how well it's cut, a polytarp sail is never going to be any different than a prom tuxedo made out of duct tape.

    Last edited by Bob Cleek; 05-09-2013 at 12:55 PM.

  30. #30
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    Default Re: Polytarp Sailmaking

    I have no question people who know what they're doing are right when they point out that polytarp sails don't perform as well or last as long (my own experience confirms the lack of longevity) and are overall poor substitutes for Dacron sails. It's also true that it's not much more expensive to buy materials and make your own Dacron sail, which can easily be sewn up on a home machine.

    I suspect the real issue, though, is that people who are good at something find it almost painful to watch people who are really bad at that same thing try to do it. For me, that's swimming--every day at the Y I see people flailing and floundering to swim a 25 yard length in 28-30 arm strokes and it's incredibly hard to watch their lack of skill when I know what it takes to swim well--and I could show them! They could learn it, too! And they choose not to! Why???!! It's so much more satisfying to invest the time to be good at it. Yet they swim that way for years and are not bothered by it at all, and don't even notice. They are investing their time and effort to get good at things other than swimming, which is a complex art and science that demands long experience and mindful practice to do well.

    So, not everyone wants the same level of perfection, or needs it, or (maybe) even has the awareness to notice it. As they develop that awareness (if they do), then they invest the time and effort to learn to do it well. You don't need to start on a Stradivarius to learn to play violin. And I've been in situations where (lacking a sewing machine and the skill to lay out and sew a sail, and not having the money for a kit), it was either polytarp or no sail at all.

    I can confidently report from rigorous empirical testing that my cheap, poorly made polytarp sail significantly outperformed "no sail at all" on every point of sail, in every wind strength. I'll also report that my new boat will have Dacron sails.

    Tom
    You don't have to be prepared as long as you're willing to suffer the consequences.

    www.tompamperin.com

  31. #31
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    Default Re: Polytarp Sailmaking

    Quote Originally Posted by BBSebens View Post
    How about prototyping a sail? I intend to build a whole new rig for Matty, but really have little or no documentation to work off of. I could see putting together a simple tarp sail to establish that a size of sail will be suitable, or cutting down or adding area as needed, and then putting forth the time and money for a proper sail.

    Or perhaps tapping the knowledge of the designer and the knowledge here would yield just as useful information. I suppose some math is just as good or better than a crappy practice sail.
    I made the sail for Meerkat's crabclaw rig with polytarp. Having no idea how the rig wold behave, I had no notion how it should be cut, and I don't think any of the sailmakers around here have experience of the rig. I used advice from a thread Todd and Polytarp participated in the do it. There's no sewing, just double-sided carpet tape. It's cheap enough that I won't mind the fact that it won't last. But I can already see the limitations of the material and the technique I used.

    http://forum.woodenboat.com/showthre...-catboat/page7







    I'm learning a lot of things, like the fact that the location of the attachment of the cleats to the boom makes a lot of difference in the way that the boom sits. I've got a lot of experimenting to do to get this right. Using polytarp is allowing me to do this cheaply.

  32. #32
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    Default Re: Polytarp Sailmaking

    A quick point of order for the record on sewing scrim fabrics ("fabrics" made with plastic film containing a rather large grid of reinforcing fibers sandwiched between the film layers - this can be polytarp or it can be $75 per yard Kevlar/Mylar, it doesn't matter which). Plastic films don't tend to hold stitches very well, even the expensive ones. When the seam gets stressed, the needle holes tend to stretch out, and will eventually continue to do so until the stitching thread finally rests against one of the grid fibers. This may mean that you are eventually going to end up with needle holes that are 1/4" long or more, and seams that have been creeping and changing shape for as long as the stretching has been going on. When the seams change shape, the sail changes shape - and that's not good. Even with the use of high-quality sail basting tape, you're just adding another layer of flimsy film to the equation. So a typical sewn seam on a polytarp or Mylar laminate sail may actually be a liability and not really be contributing any strength to the project at all.

    To remedy this, we use a different sort of basting tape inside all scrim-to-scrim sewn seams. Instead of the plastic film carrier with goo on both sides, this tape uses a light woven Dacron as the carrier strip. The weave of the Dacron carrier is what keeps the needle holes from elongating. On important seams joining the major sections on something like a radial sail, we may also back up those seams with adhesive-backed Dacron Insignia fabric, either inside the seam or over the top, and then we sew through the whole works. To really make a quality polytarp sail, you would need to do something similar, as the poly-film there is even weaker and more stretch-prone than Mylar. Otherwise, your stitched reinforcements are of pretty questionable merit.

    Sometimes we may even do hybrids. These sails are a mixture of a 2 oz. hard racing Dacron (the white) and Kevlar/Vectran/Mylar scrim fabrics (the gold). Any seam joining Dacron fabric to something could be basted with the normal, film-based seam tape and sewn. All of the Kevlar scrim-to-Kevlar scrim seams had to be basted with the Dacron-based seam tape before sewing to maintain good seam strength.


  33. #33
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    Default Re: Polytarp Sailmaking

    I was surprised to discover that Dacron only is about 50-60% more than white poly.
    Average difference is 800% and greatest diff is 1150%


    $1.15 / $0.15 = 766 % ( $$ are per/sq-ft ) seem the average $$ for white or blue
    $1.15 . $0.10 = 1150% Cheapest $$ found 6oz 12mil, 12x12weave white polytarp

    *********************************************

    Harbor Freight Blue Cheap Tarp: 0.14 - 0.17 / sq-ft
    http://www.harborfreight.com/catalog...l+purpose+tarp

    SailRite 4.18 oz white dacron sailcloth: $1.15 / sq-ft
    http://www.sailrite.com/Dacron-Supercruise-4-4oz-54
    Fun Fact => "A sailcloth’s weight is measured in terms of ounces in a 36” by 28.5” piece."

    White 6oz polytarp: $0.15 / sq-ft
    http://www.tarpsplus.com/poly-tarps-...ite-tarps.html

    White 6oz polytarp: $0.10 / sq-ft
    http://www.tarpsupply.com/poly-tarps...oly-tarps.html
    Last edited by George Ray; 05-09-2013 at 04:33 PM.
    This is the first lesson ye should learn: There is so much good in the worst of us, and so much bad in the best of us, it doesn't behoove any of us to speak evil of the rest of us.
    E. Cayce

  34. #34
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    Default Re: Polytarp Sailmaking

    Well, guys and other guys, it's been fun testing the waters, but they are a little cold for me. The response to polytarp sailmaking was about as I expected when I made my first post and opened this thread a few days ago, hoping at least that some members might take the time to view our handiwork. I think most of you must already know Todd's, and I do admire his work and have actually adjusted a couple of instructions based on his criticism. However, as I said earlier, I am a polysail advocate, and outside of Wooden Boat, the material has some serious supporters. There are those of us who have learned to work the material into some pretty competitive, durable sails at the small boat level and understand full well how to manipulate its folds and creases, utilize its stretch characteristics, and build all kinds of sails from this lowly, but tough synthetic. We've shared instructions, had its strength and weathering capabilities tested against other sail materials on Goretex factory testing equipment, campaigned a sail for a year on one of the SCAMP prototypes (the only one to compete in the Everglades Challenge), won a PDRacer World Championship on a boat equipped with our sails, and received scores of compliments from surprised converts. But before I slink off from another beatdown by the forum purists, I would like to invite you once again to take a look at what we do on our Facebook Page. I'm currently working on sails for a Pixie catamaran designed by Richard Woods and I posted a photo album documenting the process I used to build the jib. With over 40 photos, I think you will agree that the documentation is pretty complete. The fully battened main is taking some serious time, and I'm sorry to report that I won't be documenting that part of the build because I am now so far behind. However, I do hope to get lots of feedback from the Pixie owner. We know we can always improve!

    Dave Gray

  35. #35
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    Default Re: Polytarp Sailmaking

    I'll admit my math may be a little off. I was just going off the top of my head and the price difference may be somewhat higher. There are a couple of other factors though. Sailrite is nowhere near the cheapest. Duckworks sells 4oz dacron $6-8 a yard, depending on quantity. I've purchased sailclothe off of Ebay for 30% less than that. The other factor is quantity. If you buy into the argument that poly building eliminates seaming then you have to purchase a rectangular sheet whose l x w dimensions are as big as the biggest l and w dimensions of your sail. In my case that meant wasting about 40% of the material. Buying by the yard allows a more accurate bill of materials with almost no waste. I suppose I could buy smaller tarps and cut them up and broadseam them but that strikes me as ridiculous.

    Let me put this another way. I purchased a tarp from Tarpsplus for about $50 all-in. The replacement materials from Duckworks included sailcloth, spur grommets, leech line, basting tape and thread for about $130 all-in. I don't have the breakdown in front of me but the cost of sailcloth all-in was maybe $50 more than the tarp all-in. For me, that amount is gas money to my favorite sailing grounds. Can anyone seriously argue that "saving" $50 and using demonstrably inferior material on a project that will that will take 20 hours (at least for me) makes any kind of sense? It sure doesn't to me.

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