Safety factor query

**Moondog55** · 12-28-2023, 06:58

I am in the process of sewing up my first gathered end hammock.
I'm 1840mm tall and mass 120 kilos, I'll make an assumption that my sleeping gear and ancillaries won't mass more than 10 kilos.
I'm wondering what thread to sew with and what safety factor I should sew to?
I was planning on using Ipcafil180 which sews very well but only has a static strength of 840 grams, I also have Rasant but that isn't as strong, I have Guterman upholstery thread to but that won't work in my Singer 201.
I've pinned up with a 25mm triple roll edge and I have pinned in 200mm of 75kg polyester twill tape at the end of each side seam.
If I assume a safety factor of 3 and sew using enough stitches to hold 400kg at the ends will the M-180 thread be strong enough?
Or should I oversew the ends where the twill tape is with something stronger such as M-60 bonded nylon?
I normally sew rucksacks and pulk harness and I'm not used to dealing with LW fabrics; my sleeping bags are not pretty to look at.
If it matters the fabric is cheap 30GSM nylon bought cheap as military surplus and was used in the Australian army windshirts, quite durable but a sleazy weave

**Cruiser51** · 12-28-2023, 09:57

You may be overthinking this part of the build.
Guterman Mara 70 is more or less the go to thread for most "hanging" projects and that will work on pretty much any machine. Personally, I have migrated to Guterman Tera 80, a bit harder to find, but it is thinner and easier to to use (IMO), but just as strong.

There was a whole discussion thread here https://www.hammockforums.net/forum/...p/t-98200.html was a very informative read for me, maybe help with your questions as well.

Brian

**mattnin** · 12-28-2023, 11:08

You can use the upholstery thread in your 201 if that is what you wish. I have a 201 set up for Mara 50 which is tex 60. All I had to do was lower the bobbin tension.

**Moondog55** · 12-28-2023, 18:13

Maybe I should get myself a second 201 and set that up for my heavier thread.
The older 201 sews so much better than my Janome MyExcell
OK I'll use the lighter weight 180 and see what happens

**Moondog55** · 01-13-2024, 02:39

Some small slow progress. I've sewn up the long sides and I am about to start sewing the end channel. If using UL thread such as the Rasant how many times do most people sew? Two lines of three lines of stitching? Do people normally do a bar-tack or zig-zag at the edges of it this overkill?
I have to admit to a little paranoia about having the stitching fail and dumping me on my arse in the middle of the nite.
At a finished length of 3900mm there's a lot of fabric here, I don't think I really have the patience to work with UL fabric that would be even more slippery that this stuff

**Zingger** · 01-13-2024, 08:16

I am not familiar with the material you are using but when sewing hammocks, a simple rolled hem down each long side is sufficient. Don't make the stitch too tight, I use 8-12 / inch and make sure there is a good balance between the bobbin tension and the thread tension. Three lines of stitching at the ends with no bar tacks just a couple of back stitches on each line at the start and finish. Sometimes I will make a 2" hem and fold that over again at 2-1/2 inches, then three lines of stitching which goes through 3 layers of fabric. I worry more about failure of the fabric itself due to a pointy object. Do you plan on using a ridgeline?

**Moondog55** · 01-13-2024, 08:27

I was advised that using a ridgeline made for a better hang so was going to get one, what cord I have may not be strong enough at only 375kg static.
OK so three lines of stitching, I've made the 25mm side seams already so no going back on that, I wasn't going to whip the end so I was worried that my weight would cause strain at the stitch lines and tear the fabric at the edges, hence the tape reinforcing.

**BillyBob58** · 01-13-2024, 09:04

Originally Posted by Moondog55

I was advised that using a ridgeline made for a better hang so was going to get one, what cord I have may not be strong enough at only 375kg static.
OK so three lines of stitching, I've made the 25mm side seams already so no going back on that, I wasn't going to whip the end so I was worried that my weight would cause strain at the stitch lines and tear the fabric at the edges, hence the tape reinforcing.

I don't think you have to worry too much about the RL strength- not near as much as suspension strength- as long as you are not intending on pulling it guitar string tight before you get in. I remember back in the day about 18 years ago, when Hennessy was close to a lot of folks favorite, many tightened that RL quite a bit. This was before it was well known how much extra force that put on trees and suspension, and before shooting for about 30º in the main suspension/tree angle became the norm.

The main purpose of a RL, once the optimum sag has been determined for a given hammock, is to make it easy to reproduce that sag each and every time, quickly and without guess work. IMO, at least. So, all you really need is an almost completely straight RL with little to no sag in it before you get in, does not need to be tight. Often I find that the RL loosens up a little more once I get in. Or often I am able to flex it 90º with my fingers after getting in. What all of that amounts to is little to no force on a RL. It is simply serving to make sure that I don't pull the ends of the hammock too far apart when setting up, resulting in a too tight pitch with shoulder squeeze and too much force on the main suspension and trees. And of course, it is handy to hang things from.

**slugbait** · 01-13-2024, 11:25

I agree with Zingger- 3 stitching lines on the end hems with good quality thread (I use Gutterman All-Purpose because that is what Joann Fabrics carries). This method has not let me down (ha ha) yet. I will say that on Christmas night my indoor hammock dropped me to the floor suddenly. I keep several layers of closed cell foam pads under it for this reason- I wasn't hurt. It turned out to be the suspension that failed- not the hammock itself. Upon inspection I found that the webbing had pulled apart right next to (but not involving) a stitched loop. This was polypropolene webbing also from Joanne Fabrics. I've replaced the webbing with a better quality. Moral of story- inspect your entire system regularly.P.S. I think your Singer 201 could handle upholstery thread with no problem. I have a Singer 1200 which is basically the same machine.