Preferred stitch (not talking about seam... referring to needle pattern)

[g0bez]

Not sure if my terminology is right here, but I know the various seams I want to use (flat felled for the ridgeline, etc.) but I'm wondering what people have found to perform well on their sil in terms of stitch length (and width, if you use a zig?) and the like.


My wife claims her sewing machine is the bee's knees... she quilts alot, so at the very least it works well for her purposes: http://www.babylock.com/a-line/sofia/ All i know is that it looks to have *alot* more options than the last sewing machine I used. She has made it very clear that she is going to give me very thorough instructions before she lets me have free use of it... but I'd like to at least be able to say "I'd like to use such and such a stitch for this part with this stitch length, and preferably that stitch width."


Am I way off my rocker here or are there good parameters to stick with here?




Fortunately, there is 50% chance of rain all weekend long here in chicagoland... which means there is a 50% chance I'll be staying inside all weekend working on this tarp!

[Ramblinrev]

Straight stitch roughly 3 mm long would be my choice.

[PuckerFactor]

For a tarp, all you'll need is a plain jane straight stitch for the body, and zig-zag for the tieouts, if you want to get fancy. As far as stitch length, anything in the 15-20 stitches/inch should be fine. The higher you go, the more perforations you get, which, if you go too far will eventually weaken the fabric. My machine goes from 0-4 on stitch length, and I usually leave it on 2.5 or 3 for long runs of stitching, if that helps any.

Hope that helps ya some,
Acer

[MacEntyre]

I used to think I needed zig-zag for bar tacks on PALS arrays for Molly Mac Packs, until I learned that straight stitches are a whole lot stronger. Now I'm wondering why the military uses zig-zag stitches at all... probably because it looks better, and they get away with it by layering two short zig zag passes under a wider covering zig zag. (I know how they do it because I visited the Industries for the Blind and watched the automated Juki making PALS arrays for hydration packs.)

So, now I use nothing but straight stitches, 6 to 8 stitches per inch.

[Youngblood]

Straight stitching works fine for most of what you will be doing making a tarp. Zig-zag stitching is required when the stitch must stretch with the fabric along the length of the stitch line or sewing elastic or a few other things. The few machines I have used use millimeters for setting the stitch length (and width for zig-zag). There are 25.4 mm in an inch, so a 2.5 mm stitch length is about 10 stitches per inch, a 3 mm is about 8, and 3.5 is about 6-ish. To me, for straight stitiching, 2.5 mm is a very fine stitch, 3 mm is general pupose, and 3.5 mm is for sewing long hems where all it has to do is basically hold it together.

Stitch's per inch, thread strength, and the number of inches of sewing that is supporting a load work together in determining the strength of the connection. The hems and flat felled seams on a tarp aren't all that demanding on the thread and stitch length because of how the loading is spread out. Longer stitch lengths use less thread and the sewing goes quicker.

The guy outs are a different matter and a lot of different approaches work. You can use light weight thread with a good bit of stitching (x boxes, row(s) of tight zig-zag, a triple stitch, etc), and reinforcement patches to spread out the load to more stitches as well as surface area of the tarp. I've seen some where they seem to fore-go that and use heavy duty thread to just sew the guy outs in with the hems but I haven't tried that myself.

[g0bez]

Excellent information -- that is really helpful!

Intuition tells me that zigzag is somehow better/stronger, but I don't ahve any practical experience to back that up... thanks to you all I'll be foregoing the zig and staying with the straight stitch. My wife's sewing machine has been fantastic so far on my practice (on non-sil). I've just cut my first sil for making a stuff sack.... we'll see how it goes!!


Thanks again!!!

[TiredFeet]

The first time you have to rip a seam that you sewed all nice and neat with those little bitty stitches that looked ever so pretty and straight.

You will forever more sew the longest stitches your machine is capable of and never more sew little bitty stitches.

[Ramblinrev]

The first time you have to rip a seam that you sewed all nice and neat with those little bitty stitches that looked ever so pretty and straight.

You will forever more sew the longest stitches your machine is capable of and never more sew little bitty stitches.

That will certainly be tempting. But it could also be a very big mistake. Stitch length can have a lot to do with the overall strength and quality of a project. A longer stitch length is indeed easier to pick out. However a long stitch length is not as strong as a shorter stitch length. Stitch up a straight line of the longest stitches your machine can sew. Let's say about 2 feet from one end to the other. Now stitch a line the same distance, in the same fabric using a length in about the middle. Do the same in a stitch almost as small as you can the same distance in the same fabric. Hold an end of the stitch line in each hand. Bring your hands together and snap them apart as hard as you can. You should find the longest stitch pops stitches easier than the middle length or shorter stitches. Now apply that experiment to an actual project which will come under some level of dynamic force. The longer stitch will be more likely to break than a shorter or middle stitch. You may also find the shortest stitch will rip the fabric easier than the middle or longer stitch length. In application, too short a stitch, while stronger under stress is more likely to rip the fabric. The middle stitch length is the best.

Now draw a circle on a piece of fabric. It doesn't really matter how big but a dinner plate size would be fine. Using the longest stitch on your machine follow the circle as closely as possible. This of course will depend on your abilities as a stitcher. Do the same experiment with the other two lengths as above. You will find it is much easier to go around the circle with the shortest stitch than it is the longest one. Covering less of the circle arc with each stitch makes the curve smoother and easier to guide than the longer stitch. My We Make Gear vid "Behind the Mysteries" or something like that talks more about stitch length and when to do what.

[g0bez]

Well, the wife's sewing machine was already on 2.5mm stitch, so I just went with that for the practice round. Stuff sack and accessories were a success! I can tell that this isn't going to be perfect, so I've resigned myself to that. And as long as my tarp ridgeline holds, I'm going to stay dry because silnylon is much more awesome than I.

I do think, however, that I'm going to move to a 3mm stitch for my next practice and see how that goes.


I like your testing idea rev. -- makes sense. depending on how the cat curves go, I may shorten the stitch to make them go a bit more smoothly.


Thanks for all the input!