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Thread: Straight stitching a sail

  1. #1
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    Question Straight stitching a sail

    I recently ordered a sail kit from Sailrite. I getting myself prepared to start the project, and would like to know your opinions on the stitching. The sails I've seen are all zig zag stitched. I don't yet have a zig zag machine, but might be getting one used. I do however own a Tacsew model T111-155 which is a straight stitch, industrial, compound walking foot, with reverse. I'm sure it can handle the job, but does my sail really need to be sewn with zig zag stitches?

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    Default Re: Straight stitching a sail

    Of course Todd would know better, but...

    By using a zig-zag it spreads the stresses that are pulling the seam apart over different warps of the weave. In other words, if it was straight sewn, all of the strain would pull on one single line of thread across the fabric. If you zig-zag it distributes that over two different runs. One way to do it with a straight stitch would be to use felled seams. You sew together with an extra seam allowance on half of the fabric, and then fold it over and sew it again. So that makes the double reinforcement. However, that also makes a (slightly) bulky seam which might disrupt the flow of air. But I'm not sure if it would be enough to be significant.

    Of course Todd would know better.

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    Default Re: Straight stitching a sail

    Felled seams on modern Dacron would be quite difficult to make, especially on a computer-cut sail because computers cut panels with curved edges instead of broadseaming. Plus, the fabric is awfully stiff for that sort of seam. Two lines of straight stitches can be used (V46 or V69 thread and a #16 or #18 needle and about 8-10 stitches per inch) but as mentioned, it isn't ideal for strength because it is making what are essentially perforated lines on the sail that kind of say "tear here". This is accentuated by the tearing properties of modern, resin-coated Dacron.

    Unlike most other fabrics, Dacron's low stretch means that the individual yarns don't help each other out much when stress is applied. Essentially, the first yarn tries to take all the stress (until it breaks) then the second yarn does the same thing and this scenario just repeats over and over, yarn after yarn. This is why I can take a hunk of heavy Dacron sailcloth (12 oz. or better) give it a sharp tug and tear it right in half. Even though it happens quite fast, I'm essentially only having to tear one yarn at a time. Other synthetics, like nylon, work differently. Stress will concentrate on the first yarn, but will also be spread out to some extent to its neighboring yarns. We take advantage of the Dacron's non-stretch properties in order to make sails that will keep their designed shape in use, but we make allowances to preserve it's strength where we can. The typical zig-zag puts maybe a quarter of an inch or more between the needle holes and yields seams with a higher tear strength and less in the way of a perforated line.

    The other thing that really helps is double-sided seam basting tape. Not only does it instantly make sewing easier, keeping panels aligned for seaming, but it adds a tremendous amount of seam strength. Once the adhesive has had a week or two to completely cure (dwell time) it makes seams that are hard to disassemble without messing up the cloth.

    The various types of seams would probably grade out like this:

    Strongest - Seam tape with two lines of zig-zag stitching (maybe 3 lines, with wider seam overlaps, and heavier cloth on big offshore sails).

    Production Sails - Many of these are now sewn with a 3-step machine, which sews a single line of stitches in a wider zig-zag pattern, but each zig or zag is actually made up from three straight stitches. Less strength, but the sail only needs half as many passes through the sewing machine, making them cheaper to build. Good ones are seam-taped first. Not so good ones are seam "basted" by pricking the fabric with a hot knife with a tiny needle-like tip every few inches, melting the layers together. It saves a substantial amount of time, but adds no additional strength to the seams beside that of the stitches.

    Straight stitching - Even when tape-basted and double-stitched, the lines of perforations are still a concern, but they still may be as good or better than a needle-basted 3-step seam because the tape adds so much strength to the seams. If straight stitching is all you have and you aren't planning on crossing any oceans, you can probably get away with it. Sailrite's plotter cuts with a spinning cutting wheel that generates enough heat to slightly melt the cloth - so the fact that you aren't pinning down the cut edges of the seams with a zig-zag probably won't be a problem. On hand-cut edges, it likely would cause some raveling.

    Lap-feld seams with two lines of straight stitching were (still are) the norm on cotton sails and are quite strong, but cotton has far more stretch than Dacron, so the perforated lines aren't a problem. They also work great on nylon and other soft synthetics (backpacking tents, clothing, and even hot-air balloons - we used to be required to use them for patching balloons when I worked on them). Zig-zag stitching is less popular on these things because the stitches are easier to snag and tear.

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    Default Re: Straight stitching a sail

    Quote Originally Posted by Todd Bradshaw View Post
    The other thing that really helps is double-sided seam basting tape. Not only does it instantly make sewing easier, keeping panels aligned for seaming, but it adds a tremendous amount of seam strength. Once the adhesive has had a week or two to completely cure (dwell time) it makes seams that are hard to disassemble without messing up the cloth.
    Todd, is there some variety of special sail maker's seam basting tape, or is the stuff at the fabric store what is used?

    And, again, thanks so much for posting all the sail making info, and answering questions - it has been an education.

    Dave

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    Default Re: Straight stitching a sail

    I've always used the stuff I get from the sailcloth manufacturers, so I don't know how different it is (if at all) from the tape sold at local stores. There are differences though, even in the stuff I get. Somewhere I have a sample chunk of Dacron that's about 20 years old with a bunch of different taped seams on it, to see how they age. Early on I noticed that with age, some types (the cheaper ones) tended to stain the cloth and become visible after a couple of years. The seams were still plenty strong, but not very pretty. On white or cream-colored Dacron, you can almost always see the tape to some extent, but some brands were a lot worse than others. I used one (from France, I think) called "Pico tape" for a while that didn't stain and didn't even have the Mylar carrier strip. The backing essentially just put down a neat line of goo on tissue paper when peeled off. It was good stuff, especially on spinnaker nylon, because the paper backing allowed the seams to stretch better with the stretchy cloth than the normal Mylar carrier does.

    As I remember, it eventually became non-available. Then I tried "3-M Super Tape" which is great stuff, but really expensive. Once it has had a couple weeks to dwell (cure) many seams are plenty strong enough that you don't need to sew them, and you only sew the high-stress spots, like corners and big section seams on radial sails. This can make a smoother sail shape than on sails with sewn panel seams, especially on Mylar-laminated fabrics. I had a Mylar radial Genoa on our trimaran that I made that way. I originally had visions of opening it up for the second season and finding just a bunch of sail pieces in the bag, but it held up fine. Seams which are conventionally sewn on Mylar fabrics get a special tape that comes with a light Dacron carrier. The woven carrier keeps the stitch holes from stretching and elongating in the Mylar, which they will do over time without some sort of reinforcement fibers present.

    For regular Dacron sails I finally settled on "Venture Tape" about 15 years ago, which is probably a 3-M product, but is private labeled from Challenge Sailcloth. It's really strong and sticky, not horribly expensive, and doesn't discolor much at all with age or eventually stain the fabric the way some do. My only gripe is that it will bleed a little bit around the stitch holes. I finally figured out that this is caused by the industrial thread lube (which comes on the thread and is some sort of oil/silicone-like stuff) mixing with the adhesive on the tape at the stitch holes. Luckily, it's minor and eventually evaporates away. You can see the tiny oily spots on this sail around the stitch holes. Not a big deal, but I hate annoyances that aren't my fault. I think our entire household would probably collapse without a few rolls of seam tape around, as we also seem to find a fair number of non-sail uses for it here and there.



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    Default Re: Straight stitching a sail

    I have built 7 sails from Sailrite kits, they are very complete and come with a comprehensive instruction booklet. The "seamstick" tape they ship is tenacious and unlabeld so you can't tell who makes it for them...but it comes with the kit. For the most part the instructions call for either a double row of zig-zag or triple row of straight stitches so sew the panels together. Their online video library is comprehensive too.

    The thread needs to be pulled off the top of the spool, not unreeled like regular thread so you'll need to make a little hanger to do that.

    You can see the bent coat hanger wire I used to hold the spool and feed the thread. Working hunched over on the floor to hem the edges of the assembled sail was the hardest part off the whole process. I have threatened to cut a hole in the floor but in truth my crawlspace is pretty nasty or I might have done it.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

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    Default Re: Straight stitching a sail

    I have built 7 sails from Sailrite kits, they are very complete and come with a comprehensive instruction booklet. The "seamstick" tape they ship is tenacious and unlabeld so you can't tell who makes it for them...but it comes with the kit. For the most part the instructions call for either a double row of zig-zag or triple row of straight stitches to sew the panels together. Their online video library is comprehensive too.

    The thread needs to be pulled off the top of the spool, not unreeled like regular thread so you'll need to make a little hanger to do that.

    You can see the bent coat hanger wire I used to hold the spool and feed the thread. Working hunched over on the floor to hem the edges of the assembled sail was the hardest part off the whole process. I have threatened to cut a hole in the floor but in truth my crawlspace is pretty nasty or I might have done it.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

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    Default Re: Straight stitching a sail

    Thanks for the responses.
    And especially Todd for sharing your expertise so willingly. Much appreciated.
    I had an inkling the straight stitch maybe wasn't the best idea.
    Steve -
    ...and it looks like you are sewing your sails with a Necchi --- which is what I just won - a Necchi BU Mira - on fleebay.
    So I will be sewing zig zag as long as this machine works out. It seems like it will be a tough little machine.
    How do you like yours? Does it work well for you?

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    Default Re: Straight stitching a sail

    Step #1 with a new, used machine -
    Check the web for instruction and parts manuals, many of which are available free in PDF format.

    Step #2 - Check YouTube for videos about that machine. Some may actually be helpful.

    Step #3 - Check eBay for assorted parts and accessories. It's a pretty good source and prices tend to be pretty good on them.

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    Default Re: Straight stitching a sail

    The Necchi has proven to be a tough little machine and worked great on the smaller sails but I ponied up for one of the Sailrite machines for my last build. Once I was up to 8 or so layers of sailcloth I needed a machine with a bit more oomph.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

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    Default Re: Straight stitching a sail

    Both the Necchi and the sail kit came today. It will be a little time before I get started on it though. The Necchi s built like a tank -- a little tank -- it's a little smaller than I imagined, but hopefully should work out OK. Beats hell out of my wife's plastic Singer anyhow.

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    Default Re: Straight stitching a sail

    Then I tried "3-M Super Tape" which is great stuff, but really expensive. Once it has had a couple weeks to dwell (cure) many seams are plenty strong enough that you don't need to sew them, and you only sew the high-stress spots, like corners and big section seams on radial sails.
    Just out of curiosity, how likely is it that eventually dacron sails will be more commonly glued instead of sewn? Is anyone (3M, etc.) experimenting in that direction, with a permanent, tenacious glue? I'm not sure I'd trust a chemical (glued) bond over a mechanical (sewn) bond along a seam, but that's probably because I'm in many ways a luddite.

    Todd, thank you for all your expertise. I may not be building sails right now, but I'm handing your lessons in and stowing them away for later use.

    Alex

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    Default Re: Straight stitching a sail

    It's already been done. Probably about ten years ago Dimension Polyant Sailcloth brought out a hot-glue gun for sailmaking. It was air-powered and used special glue cartridges. Essentially you baste the panels together with a thin strip of seam tape along one edge of the seam, just to keep the fabric aligned. Then you slide the tip of the gun under the loose edge, shoot a bead of the glue in there and roll it down with a hand roller. The finished seam is claimed to be stronger than the fabric itself. There are a couple limiting factors though. As I remember, the gun was somewhere around a thousand bucks. Secondly, the cartridges were expensive and you needed to use the whole thing in one session - couldn't just keep a partial one in the gun as you can with a regular hobby glue gun. So, production lofts would get several sails basted with tape and then heat up the gun and do them all in one gluing session.

    I don't know how many they sold, but the price was out of reach for most small lofts, and it doesn't really seem like it would save much labor time. In the time it takes to tape and glue a seam, I can tape and sew a seam, and both will be perfectly adequate in strength. The gun (and also the Super Seam Tapes) do make smoother sails from an airflow perspective, but in reality the potential speed increase for most boats and recreational sailing situations is likely extremely tiny, if even noticeable. Since much of sail shaping is a matter of joining curved fabric edges to other curved edges, or to straight edges, or joining two straight edges into a curve, any adhesive needs to have instant tack, so things stay put as you join them. Some kind of seam tape like the Super Tape seems to be the best bet for stitch-free seams that can be made in just one pass.

    In general though, even current "regular" seam tape technology is awfully good. The modern adhesives don't seem to dry out and crumble away with age the way some adhesives do, and taking old seams apart when doing sail repairs is pretty difficult, even after picking out all the stitching.

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    Default Re: Straight stitching a sail

    Cool idea, but too much work and too expensive. There's already enough specialized equipment necessary; why add more?

    Hmm... I wonder if someone could formulate a basting tape that, once the seam was taped, you could then further activate by a quick pass with a hot iron to create an even more durable seam.

    And I'm just playing what-if games. It sounds like the situation is already pretty efficient and effective.

    Thanks for the info on the sail-glue.

    Alex

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    Default Re: Straight stitching a sail

    Hopefully not railroading your thread, Timo, but Todd, we are finishing a new mizzen tomorrow and hope to use it next week. You mention earlier in this thread the idea that the glue must "dwell", which I understand to mean permanently cure...three weeks is much less than two days. Is it not advisable to immediately use a new sail? This is a little 22 sq. ft. mizzen, so not going to matter much either way, but if the sail were a mainsail of some size, I might be tempted to ponder over this issue and not use it if it needs to cure. What do you think?
    Re-naming straits as necessary.

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    Default Re: Straight stitching a sail

    I wouldn't take a brand new sail out for the first time when the wind is really screaming, but otherwise I wouldn't expect any problems.

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    Default Re: Straight stitching a sail

    I ran the Necchi for a bit last night and it did pretty well for what it is , I think.
    Using a #16 denim needle and #69 thread I was able to sew 8 layers of sailcloth with some help getting it started by hand. Six layers went better, and is probably the limit of what I will need to construct my little sail.
    Six layers of duck canvas was pretty easy as well with the same needle and thread. Nice looking zig zags either way.
    I may tinker with a stronger motor, or some pulleys and belts to slow the motor and increase the torque for some more punching power. But may just leave it as is. It may just handle what I want to do as is.
    Most times I can't just avoid wanting to tinker with something though...
    Last edited by timo4352; 12-18-2015 at 04:26 PM.

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    Default Re: Straight stitching a sail

    ...and it sounds like the seamstick is kind of a must have for making a strong sail. I never would have guessed that.
    I'm always learning something here.
    Thanks

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    Default Re: Straight stitching a sail

    Yep, the tape adds dramatic seam strength, keeps the pieces of slick fabric aligned properly for sewing, and also acts as a visual guide as you are joining the panels together.

    For punching power you could possibly add a jack drive. Instead of just having one belt from the motor to the balance wheel, you stick a double pulley between them. The motor drives the large diameter part of the pulley with one belt and the small diameter part of the pulley drives the balance wheel with the original belt. It both slows the machine down and gives it more power. Sailrite used them on their original Sailmaker machine with a simple metal bracket that bolted to the head and they may still have the parts available if you can't scrounge some. In a non-production situation, sewing slower with better control is better than high stitching speeds. There are a few small spots on sail corners where I end up sewing through about nine layers of Dacron (panels, corner patches, luff tapes and foot tapes, all stacked up) along with up to eight layers of seam tape, so it's nice to have good punching power. Canvas work is easier. The needle goes through cover fabrics and webbing with less resistance and in most marine canvas applications if you're having to sew through more than about five layers there is probably something wrong with your design. That stuff will also usually be straight-stitched, and that mode is less likely to show timing problems and skip stitches in heavy cloth.

    My old, but reliable, Sailmaker with the jack drive.



    I bought an old Consew heavy duty machine for sewing leather this year. I put a servo motor on it and it's really fun to watch it just effortlessly cruise through heavy leather. A lot of these pieces were stuck together and aligned with seam tape before sewing. It's instant, it lasts, and it's as strong or stronger than most leather cement.




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    Default Re: Straight stitching a sail

    These small pulleys, in double or single, are proving pretty difficult to locate!
    I've got an email in to Sailrite to see if they have that double reducing pulley laying around somewhere...
    Other than that I'm coming up empty...

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    Default Re: Straight stitching a sail

    These look promising, but I would check the last one to make sure it's a double. Kenmore was one of the most common machines where some models used the double pulley system. There are industrial versions available, but they run between $125 and $160 for basically the same thing, only bigger.

    http://www.ebay.com/itm/KENMORE-SEWI...4AAOSwAYtWMNUa


    http://www.bonanza.com/listings/Kenm...FZGMaQod2QwC9A


    http://www.ebay.com/itm/Kenmore-Sewi...3D171981815438

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    Default Re: Straight stitching a sail

    Just how big is your sail? The Necchi was pretty comfortable working it's way through the 106 square foot balanced lug for my KDI. It is a good little machine, don't mess with it unless you have too.
    Steve

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    Default Re: Straight stitching a sail

    Thanks - I did see a couple of those pulleys - something there might work.
    My sail is 55 sq ft. - I think the machine can handle it but it would be nice to slow the top speed down some.
    I'll have less chance of screwing things up that way, I think.

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    Default Re: Straight stitching a sail

    I ordered the one double pulley setup from Bonanza. Thanks for posting it - I never heard of them before.
    I'll try this thing out - hopefully make it work just like the one in this video here... Looks fairly simple. The guy did a nice clean modification there.

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    Default Re: Straight stitching a sail

    I did a little sample sail piece to see how I can do at making my own sail.
    This is a test... this is only a test...
    Not too bad to start, but I'll do a bit more practicing before I start on the real thing.
    from my scanner -

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    Default Re: Straight stitching a sail

    I'm ready! I got my double pulley rigged up on my new to me machine, and it looks almost exact to the one in the video I posted. Might be the same donor pulley on both. I ran some samples and it works really good. I can run it quite slow --- so I shouldn't lose control because the thing takes off too fast on me. I did some numbers calculations on the pulleys - and using 5000 rpm for the motor, the pulleys and belts drop that to about 730 rpm. Or about half of what it was in stock form. So I guess that doubles the torque and/or punching power then. 8 or 9 layers of sailcloth went pretty easy. So I had to try more - 12 to 15 layers with a little help on the balance wheel to get it started. All with no nasty noises or missed stitches or binding up. I don't expect to need to go through that much, but I am happy with the result. Most of the sail will be much less layers than my test pieces so it should be no problem for the machine. With a little more practice I'll be ready to start my first sail.

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    Default Re: Straight stitching a sail

    Sounds good. One thing I've done ever since I started sewing sails is to draw two fore and aft lines on the top of the presser foot with a Sharpie - from the needle area, all the way to the front edge of the presser foot. The space between them is the same approximate distance as the zig-zag stitch width that I am using. Since most of the seams you will be sewing on a sail are right at, or very close to the edges of the panels, the lines will help you aim as you steer fabric into the machine - especially if you're sewing from a less than ideal position as you try not to wrinkle or crease the sail. When the sail is done or you change stitch width the lines wash off with a dab of alcohol.


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    Default Re: Straight stitching a sail

    Thank for the great tip Todd. Sometimes the simplest things like this just don't occur to me, and then when someone mentions it - it's like "what a great idea - why didn't I think of that?"
    I will use it for sure.

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    Default Re: Straight stitching a sail

    Man, I can't believe it but the sail is done!
    Having the past 2 days off --- I got all the sewing done. A couple hours Thursday putzing around, and an all-dayer yesterday, and it is done. The Necchi machine worked great. The slow stitching with the speed reduction was most welcome. Everything under control. I worked on two 8 foot folding tables in my 11x17 family room --- not ideal but I managed. I just have to install the grommets yet. Thanks for the help getting me started, and on the right track with this project.

    Dave - stick with the Sailrite seamstick. It did the job without problems. I ran out right at the end and tried this other tape -- I only had one hem to do to finish -- but the tape did give me some trouble sticking to the needle and I had to redo that seam because of it. I managed to get through anyhow by putting some soap on my needle -- but I don't think I would have had any problem except for this tape. I just wanted to get the job done, but next time I'll just order the Sailrite tape and wait .

    Go ahead and make that Sailrite kite - it is easy...
    Last edited by timo4352; 01-02-2016 at 04:33 PM.

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    Default Re: Straight stitching a sail

    Hi Timo: my wife is interested in building from scratch at this point. We use Sailrite double sided tape. Problem is I don't spend any time on the machine, unlike, say, planers or chainsaw or bandsaws--and therefore when something gets out of adjustment, I am really challenged to figure out what is going on. A couple of weeks ago, sewing very rapidly, she ran a brass grommet through our industrial machine (1.5 hp, 1800 s/m) and it knocked the hell out of the timing. I haven't been able to get it right since then, and it might mean that, given the domino effect, something is bent or out of adjustment quite far from the needle bar/crank bar, which definitely took the brunt of the impact. They are complex things, but I certainly like your and Todd's multiple gearing setups.
    Re-naming straits as necessary.

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    Default Re: Straight stitching a sail

    Dave - Look online for a service manual for your machine. I was lucky enough to download one for the Necchi, and went through it to check the head out before I started stitching. It explained things very well. You might luck out too.
    I have a speed reducer / jack drive that I rigged up on my commercial machine. Angle iron, a length of shaft, and a couple washing machine type pulleys from the hardware store. It slows things down a lot, but it can still get away from you if you are not careful.
    I have a clutch motor - I guess a servo motor is much easier to control - I have not tried one.
    I'll try to get a picture of my setup for you if I can.

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    Default Re: Straight stitching a sail

    Quote Originally Posted by Todd Bradshaw View Post
    Felled seams on modern Dacron would be quite difficult to make, especially on a computer-cut sail because computers cut panels with curved edges instead of broadseaming. Plus, the fabric is awfully stiff for that sort of seam. Two lines of straight stitches can be used (V46 or V69 thread and a #16 or #18 needle and about 8-10 stitches per inch) but as mentioned, it isn't ideal for strength because it is making what are essentially perforated lines on the sail that kind of say "tear here". This is accentuated by the tearing properties of modern, resin-coated Dacron.

    Unlike most other fabrics, Dacron's low stretch means that the individual yarns don't help each other out much when stress is applied. Essentially, the first yarn tries to take all the stress (until it breaks) then the second yarn does the same thing and this scenario just repeats over and over, yarn after yarn. This is why I can take a hunk of heavy Dacron sailcloth (12 oz. or better) give it a sharp tug and tear it right in half. Even though it happens quite fast, I'm essentially only having to tear one yarn at a time. Other synthetics, like nylon, work differently. Stress will concentrate on the first yarn, but will also be spread out to some extent to its neighboring yarns. We take advantage of the Dacron's non-stretch properties in order to make sails that will keep their designed shape in use, but we make allowances to preserve it's strength where we can. The typical zig-zag puts maybe a quarter of an inch or more between the needle holes and yields seams with a higher tear strength and less in the way of a perforated line.

    The other thing that really helps is double-sided seam basting tape. Not only does it instantly make sewing easier, keeping panels aligned for seaming, but it adds a tremendous amount of seam strength. Once the adhesive has had a week or two to completely cure (dwell time) it makes seams that are hard to disassemble without messing up the cloth.

    The various types of seams would probably grade out like this:

    Strongest - Seam tape with two lines of zig-zag stitching (maybe 3 lines, with wider seam overlaps, and heavier cloth on big offshore sails).

    Production Sails - Many of these are now sewn with a 3-step machine, which sews a single line of stitches in a wider zig-zag pattern, but each zig or zag is actually made up from three straight stitches. Less strength, but the sail only needs half as many passes through the sewing machine, making them cheaper to build. Good ones are seam-taped first. Not so good ones are seam "basted" by pricking the fabric with a hot knife with a tiny needle-like tip every few inches, melting the layers together. It saves a substantial amount of time, but adds no additional strength to the seams beside that of the stitches.

    Straight stitching - Even when tape-basted and double-stitched, the lines of perforations are still a concern, but they still may be as good or better than a needle-basted 3-step seam because the tape adds so much strength to the seams. If straight stitching is all you have and you aren't planning on crossing any oceans, you can probably get away with it. Sailrite's plotter cuts with a spinning cutting wheel that generates enough heat to slightly melt the cloth - so the fact that you aren't pinning down the cut edges of the seams with a zig-zag probably won't be a problem. On hand-cut edges, it likely would cause some raveling.

    Lap-feld seams with two lines of straight stitching were (still are) the norm on cotton sails and are quite strong, but cotton has far more stretch than Dacron, so the perforated lines aren't a problem. They also work great on nylon and other soft synthetics (backpacking tents, clothing, and even hot-air balloons - we used to be required to use them for patching balloons when I worked on them). Zig-zag stitching is less popular on these things because the stitches are easier to snag and tear.
    I know this is an old thread but one of the few things that comes up if you Google straight stitch sail sewing. I was researching the subject because my sailrite clone machine is just too small for the size of sails I'm now sewing. The layer penetration is fine but the narrow throat is not. So I've been researching what industrial machine to replace it with. The pricing on a used walking foot zigzag was well out of my price range. There are quite a lot of straight stitch machines with not only the walking foot but also the needle advance that are in my price range. After reading this thread and this entry I became doubtful of straight stitching despite my sailrite instructions saying it is an option if you don't have a Igzag machine. Also the tear line logic only made sense if you were using a very short stitch length which some industrial machine can go as long as 3 points per inch.

    So I

    called up the sail designer at sailrite to ask his opinion and the long and short of it is straight stitch is absolutely fine for making sails including those depended on in blue water. The down sides are 2 you will need to make more passes on the seams and traditionalists will think you sails have been stitched incorrectly.

    In summation save your money and by a nice walking foot industrial machine with compound feed.

  33. #33
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    Default Re: Straight stitching a sail

    Who says you need a walking foot? I have one on my big straight stitch leather machine, but I've made hundreds of sails on my sailmaking machine, along with a few previous "small" repairs like replacing the top half of a hot air balloon all with no walking foot. In my experience, most of the people who are adamant about the need for a walking foot have never actually done enough sewing to know whether or not they really need one.

    All you have to do to see the difference in tear strength between a line of zig-zag stitching and a line of straight stitching on Dacron is to tear test it using a scale.

  34. #34
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    Default Re: Straight stitching a sail

    Quote Originally Posted by Todd Bradshaw View Post
    Who says you need a walking foot? I have one on my big straight stitch leather machine, but I've made hundreds of sails on my sailmaking machine, along with a few previous "small" repairs like replacing the top half of a hot air balloon all with no walking foot. In my experience, most of the people who are adamant about the need for a walking foot have never actually done enough sewing to know whether or not they really need one.

    All you have to do to see the difference in tear strength between a line of zig-zag stitching and a line of straight stitching on Dacron is to tear test it using a scale.
    I've done it with and without a walking foot and with my limited space and lack of a giant table I found the walking foot easier. Especially with the slippery nature of dacron.

    Regarding the tear testing I find it odd that a line of holes at an equal spacing to any other line of holes will have a different tear strength. Unless the thread laying on the cloth can somehow encourage a tear? Perhaps akin to cutting glass. Of course I could see this being the case if you set your stitch width tight and poked more holes than the recommended zigzag which according to sailrite is 3/16.

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