Archive for 2019

Understanding Thread Types and Thicknesses

Saturday, October 19th, 2019

This convenient listing of the types of thread is at hammockforums.net but I’m preserving it here as well in case it goes away, and because I need this information myself for sewing projects, and always forget what the various mara and tera and tex sizes actually are, and how they interact and relate to things like needle sizes.

Note that the spools sold by ripstopbytheroll and diygearsupply work fine on regular sewing machines spindles though they tend to rattle around a bit, you can get around that issue by simply making a larger spindle to go over the regular thin metal spindle on the sewing machine if you find it annoying or hard to work with.

Units of Textile Measurement
Gütermann Numbering System

1 tex = 1 gram per 1,000 meters = 10 dtex = 9 den
Nm = 1000/tex
The No./Tkt. is a development of the Nm, but does not inform about how many individual threads the ply-yarn has been produced. No. 100 may be a Nm 65/2 or a Nm 100/3 thread for example.

Mara 100 = Sew-all Thread = tex 30 = dtex 300(2) = two-ply yarn.
Recommended needle and needle size: universal needle NM 70 – 90 / #10 – #14
“Mara 100” is sold to industrial customers, “Sew-all thread” to end customers in retail shops.
The quality is the same, but the price in retail shops is often too high.

Mara 70 = tex 40 = dtex 400(3) = three-ply yarn
Recommended needle size: NM 90 – 100 / #14 – #16 [Note: I’ve used #12 for years, with no issues]
Mara 70 is sold to industrial customers only, but available here:

dutchwaregear.com gutermann-thread
ripstopbytheroll.com gutermann-mara-70

Mara 50 = tex 60 = dtex 600(3) = three ply yarn.
Recommended needle size: NM 90 – 110 / #14 – #18
Mara 50 is sold to industrial customers only, but available here:
ripstopbytheroll.com mara-50-thread

Tera 80 = tex 35 = dtex 350(3) = three-ply yarn.
Recommended needle size: NM 70 – 90 / #10 – #14
Tera 80 is sold to industrial customers only, but available here:
diygearsupply.com gutermann-tera
rockywoods.com Gutermann-TERA-80-Polyester-Thread

Tera 60 = tex 50 = dtex 500(3) = three-ply yarn.
Recommended needle size: NM 90 – 100 / #14 – #16 [Note: I’ve used #12 for years, with no issues]
Tera 60 is sold to industrial customers only, but available here:
diygearsupply.com gutermann-tera

Tera 40 = tex 75 = dtex 750(3) = three-ply yarn.
Recommended needle size: NM 90 – 110 / #14 – #18
Some household sewing machines don’t work with a #18 needle and Tera 40.
Tera 40 is sold to industrial customers only, but available here:
diygearsupply.com gutermann-tera

Kite Sewing 101 Recommendations. Also helpful for us:
kites4all kite-sewing-101

A quick cheatsheet reference:

Mara; Tex; Needle
220; ; 13; ?
120; ; 25; ?
100; 30; “10-12” (sew-all)
70; 40; “14-16”
30; 100; ?

TERA; TEX; Needle
80; 35; “10-14”
60; 50; “14-16”
40; 75; “16-18”
30; 100;
20; 150;
15; 200;
10; 290;
8; 375;

Quilt seams & hems: M50/M90/1.1 rip (uncoated) – Microtex 70/10 with Gutermann “SewAll” ie Mara 100 (Tex 30)

Tarp & pack seams & hems: 1.3 sil (1.1 coated) – Microtex 80/12 with Guterman Mara 70 (Tex 40)

Tarp tie-outs; pack attach points & buckles (shoulder, sternum & hip straps) – Microtex 90/14 with Gutermann Mar 70 (Tex 40)

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State of the Electric World

Saturday, February 16th, 2019

Every so often I’ll post a quick review of current green (sic) technolgies. These items are sourced from a variety of places, including some of the better youtubers, along with more standard web e-stuff sites. So here it goes, in no particular order.

  • Audi and BMW and Mercedes, paid for the dismantling of the Tesla Model 3 recently, and concluded, much to their chagrine, that Tesla is way ahead TODAY of what they had developed to compete, particularly Audi/VW, to the tune of something like 4000 dollars more expense to produce the primary powertrain system than what Tesla is spending, a powertrain that is basically also inferior in most ways to what Tesla is producing now, today. This caused some dismay, but what do these morons expect? they outsourced their early e-stuff development, thus losing the ability to generate inhouse expertise, and as with GM, often had the power train supplied by people like, oh, Tesla (Mercedes City Car), or Rimac, whatever. Who piled up said expertise, and pulled away further and faster.
  • Some of the big Germans also, grudgingly, admitted they are making a big mistake by not controlling their own battery sourcing, dugh, I mean, I said a while back, ad nauseum, the battery is the primary component, like an engine in a fossil car, if you outsource that, your company is little more than a kit car assembler, if you are honest.
  • Rumors swirled last few weeks, we recall that GM was ‘thinking about’ making a lot of EVs. Not actually making them, note, particularly remembering that the Bolt, their single EV, runs a full LG power train/battery pack, ergo, GM knows nothing about EVs, like, literally nothing. So what was this thinking about referring to? Well it came out, GM was thinking about investing in Rivian. Apparently, that thinking was too tiring, and it came out this week that Amazon is the one that ended up dropping a cool 700 million into Rivian. Smart investment. With this said, it has struck me, you recall that GM went bankrupt in the 2008 crash, and the US gov ‘saved’ them. This probably should not have been done, sad to say, for what do we see now? we see a massive resurgence in the USA vehicle industry, but none, not one, of those companies are in any way connected to the big 3 fossil USA car companies, none of whom can make anything remotely resembling a good vehicle, particularly not a car anyone outside of the Americas wants to buy (except, of course, Tesla, who cannot meet global demand, and who employs some 45,000 American workers, while GM closes plants and lays off workers).
  • Rumors were also swirling about Ford partnering with VW on the VW sled, that is, VW produces the sled part, and Ford sells the assembled cars. Note the aggressive refusal to actually make their own e vehicle? Anyway, it turned out, this won’t work, because Ford has no interest in selling lower cost EVs, though they are testing an e-F150, but given Rivian’s lead, pardon me while I stifle a yawn.
  • Ok, ok, I lied, GM is in fact producing, or at least, putting their name on what is probably a Chinese produced, vehicle, fully e powered. Very reasonable pricing, about 3-4 thousand dollars. I see you react with surprise, what? 3 or 4 k? yep. Ok, it’s a bicycle, an e-bike. Yawn. I doubt they even make the motor and battery.
  • Real solid state batteries are here, as I noted, look for the weak spots, in the unspoken parts, and I have read enough solid state battery stuff, including a few now in real production, to find the fine print, which in some cases, had to be grudgingly put into the very fine print, it’s charge cycles. So, what happened, there is a new UK solar powered drone, weather satellite sort of, except flying in atmosphere, can stay up about 90 days. Why, do you ask, is it limited to 90 days? certainly running highest kwh/kg packs, since weight is a premium, and though they did not say this specifically, it is because they are using solid state batteries, that have only a 100 charge cycle life time, 100 days, that is. Also note, that means, you replace the battery pack cells every 90 days. Obviously a no go for phone or car, and this is why you still are not seeing this tech in phones or cars, which require a 1000 minimum charge cycle life for phones, and many thousand for cars.
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Silpoly / PU Coatings

Sunday, February 3rd, 2019

Here is an interesting discussion on BackpackingLight.com on Silpoly durability and PU coating types: Geoff Caplan on backpackinglite. Some things tend to get lost in backpackinglight from the endless churn, so I want to preserve the main points here.

I thought I’d give a heads up to the views of Mike Cecot-Scherer. He’s a freelance designer of backpacking tents, with over 250 designs to his name for many of the major brands. He has access to their labs and repair departments, so is in an usually strong position to cast light on this issue.

He is a strong proponent of 20d poly as a fly fabric, particularly with a sil/PU coating.

Some take-home points from his site:

  • Sag when wet: silnylon can stretch as much as 4″ across the longest dimension of a small tent, leading to serious flapping and increased wind load. Silpoly retains its pitch in the wet. He sees this as a big deal.
  • Tear strength: while nylon is a few percent stronger in theory, in practice strength will vary a lot between manufacturers and batches. After a few days of UV exposure, the silpoly may well overtake the nylon because of its much superior UV resistance. And in any case, repair departments report that fabric tears aren’t a significant cause of failure.
  • Puncture & abrasion resistance: he argues that these are terrible on all lightweight tent fabrics, so there isn’t much to choose between them. Provided you reinforce the stress points, he feels that all you can do is carry a good repair tape in case of issues.
  • Waterproofing: he feels that a 1500-2000 coating is fine for both flies and floors. If you want a bit more robustness, you could take the floor up to 3000. Anything more is overkill. In his experience, users often mistake condensation or vapour transmission (lightweight fabrics breathe) for leakage. He prefers a sil/PU coating as you can seal the seams reliably. He doesn’t discuss the longevity of the PU coating, so I’ve dropped him a line and will post if he replies.

He’s recently developed his own comfort-oriented range of freestanding backpacking tents with some bleeding-edge features. He subjected them to multi-directional wind tests – possible the most comprehensive yet conducted. They were stable and quiet up to Force 8. When tested to failure, it was the DAC poles that went, not the fabric. There are videos of the tests on his site, which is well worth exploring:
thetentlab.com

A bit further down that thread George posts another comment by Mike:

… But here’s the thing: no one actually bases their tear strength requirements or even their desires on what’s NEEDED because no one knows what that too-low number is. So we’ve gotten into a sort of tear strength arms race even though it’s obvious that it’s the tensile strength that a tent primarily needs (and all fabrics available are WAY overkill).

So I’ve taken it upon myself to ask repair departments of my clients (and Kelty, of course, when I was there) what, if any repairs they saw were caused by the tear strength being too low. Tents age, UV damages fabric, surely there should be some indication of a lower limit to tear strength in use. But the answer was always no. No repairs ever because tear strength was too low. Actually is was quite striking. There were even tents sent in for repair that you could literally push your finger through which weren’t being sent back to be fixed because of that; the customer hadn’t damaged it and it was sent back for something else entirely!

As to abrasion resistance or puncture resistance, ALL the lightweight fabrics we use are just terrible – it takes the barest swoosh against a sharp rock or a gnarled tree to put a bunch of holes or a tear into a rainfly. About the only thing one can say about higher tear strength is that there’s the theoretical possibility (and hope) that a tear won’t propagate as much in a higher tear strength fabric. But prevent a tear? No way. This is when having some of the truly excellent repair tapes available can really save the day. I love modern repair tapes.

Then an important bit of information on PU coatings from Mark:

I asked him about the longevity of PU coatings on lightweight fabrics, and also to look over this thread and give his responses. As you read this, it’s worth bearing in mind that he’s one of the most experienced people in the industry.

The durability of PU coatings can be all over the map and they can’t be distinguished between without some very fancy equipment. The most common PU coatings are called polyester-based polyurethanes. These will degrade with water (!) over time through a process called hydrolysis which basically means that water causes the polymer chains to break apart. It’s what’s responsible for sticky and stinky coatings and short tent life on all kinds of fronts.
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