Archive for the ‘Ultra Light Backpacking’ Category

Understanding Thread Types and Thicknesses

Saturday, October 19th, 2019

This convenient listing of the types of thread is at 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: gutermann-thread 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: 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: gutermann-tera 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: 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: 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)


Silpoly / PU Coatings

Sunday, February 3rd, 2019

Here is an interesting discussion on 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:

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.

Polycryo ground sheets – cross linked polyolefin

Monday, January 26th, 2015

I'd noticed the difference between different heat shrink film (aka, polycryo) a while back while cutting out ground sheets for two tents, one was using Gossamer Gear ground sheet, which was slightly stiff and felt very strong, and has held up very well now over many long trips, and the other made out of the Ace Hardware store bought film (comes in a roll), which felt soft and thinner. Now I see why, it was thinner, and didn't feel like it would be as durable or puncture resistant.

Keep in mind, Ace hardware stores are very helpful and can just order the thicker polycryo for you if they store doesn't carry it, you just need the part number: 5604277

BPL thread

Not that anyone is all that interested, but i found out that the 84 in X 120 in and 1.5 (as of 2017-01-25, was 1.2 mil previously) mil thick window insulation sold online at Ace hardware IS indeed cross linked polyolefin (in BPL slang, "polycryo").

Previous thread on this:
another BPL polycryo thread

Doing a little research and have identified the following brands and thicknesses.

Ace Hardware – Most kits are .6 mil, but they do have 1.5 mil outdoor kits available, item number 5604277. Check your store first, sometimes they have them, sometimes they don’t. Probably more likely in winter months. The 1.5 mil is quite thick and strong.

Scotch – 3M – Indoor and outdoor kits are .75 mil

Dennis – interior are .6, exterior are 1.2

Duck – Exterior kits are .7 mil

Frost King – They replied to my email and say the exterior kits are .75 mil

84 in X 120 in (or 62×210) available now, 2017-01-22, and 1.5 mil thick window insulation sold online at Ace hardware IS indeed cross linked polyolefin.

Here is it:


Titanium Grades (for your ultralight projects)

Wednesday, October 8th, 2014

Ok, ok, I know, you are saying, who cares? But I was curious about titanium wire grades (for my ultralight titanium pot stands) so I found this chart here.

Element Composition,%
Grade1 Grade2 Grade3 Grade4 Grade5 Grade6 Grade7 Grade9 Grade11 Grade12
N max 0.03 0.03 0.05 0.05 0.05 0.03 0.03 0.03 0.03 0.03
C max 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08
H max 0.05 0.015 0.015 0.015 0.015 0.015 0.015 0.015 0.015 0.015
Fe max 0.2 0.3 0.3 0.5 0.4 0.3 0.5 0.25 0.2 0.3
O max 0.18 0.25 0.35 0.4 0.2 0.2 0.25 0.15 0.18 0.25
Al 5.5-6.75 4.0-4.6 2.5-3.5
V 3.5-4.5 2.0-3.0

Note that lower grades are really soft, so I wanted to know what grade 5 is. Now I know.

Further, from wikipedia we learn:

Grade 1 is the most ductile and softest titanium alloy. It is a good solution for cold forming and corrosive environments. ASME SB-265 provides the standards for grade 1 titanium sheet and plate.[4]

Grade 2 Unalloyed titanium, standard oxygen.

Grade 2H Unalloyed titanium (Grade 2 with 58 ksi minimum UTS).

Grade 3 Unalloyed titanium, medium oxygen.

Grades 1-4 are unalloyed and considered commercially pure or “CP”. Generally the tensile and yield strength goes up with grade number for these “pure” grades. The difference in their physical properties is primarily due to the quantity of interstitial elements. They are used for corrosion resistance applications where cost, ease of fabrication, and welding are important.
Grade 5, also known as Ti6Al4V, Ti-6Al-4V or Ti 6-4, is the most commonly used alloy. It has a chemical composition of 6% aluminium, 4% vanadium, 0.25% (maximum) iron, 0.2% (maximum) oxygen, and the remainder titanium.[5] It is significantly stronger than commercially pure titanium while having the same stiffness and thermal properties (excluding thermal conductivity, which is about 60% lower in Grade 5 Ti than in CP Ti).[6] Among its many advantages, it is heat treatable. This grade is an excellent combination of strength, corrosion resistance, weld and fabricability.

“This alpha-beta alloy is the workhorse alloy of the titanium industry. The alloy is fully heat treatable in section sizes up to 15mm and is used up to approximately 400°C (750°F). Since it is the most commonly used alloy – over 70% of all alloy grades melted are a sub-grade of Ti6Al4V, its uses span many aerospace airframe and engine component uses and also major non-aerospace applications in the marine, offshore and power generation industries in particular.”[7]

“Applications: Blades, discs, rings, airframes, fasteners, components. Vessels, cases, hubs, forgings. Biomedical implants.”[5]

Now I know, that’s why people use Grade 5, and that’s what I am looking for. Specifically, 0.08″/2mm titanium wire. They call it wire rather than rod when it’s thinner than about 0.125″ I believe, give or take. Anyway, for stuff of about 2mm it’s wire, no matter what the cutoff point.

Note: it’s really hard to find grade 5 2mm titanium online, but you can find it if you google for titanium bike spokes, they run about $2 each, make sure to get longer ones, most are for bmx bikes, and are too short for things like pot stands etc. 14 gauge spokes are 2mm which is about 0.08″. Spokes will be made out of very strong alloys.

Protecting silnylon against misting in heavy driven rains

Tuesday, August 19th, 2014

I came across this very good explanation of how to add a bit more silicone to your silnylon tent/tarp to protect against heavy driven rain, which causes inner misting. I was not completely sure that this actually happens, until my last trip, where it clearly happened. All doubt was removed in my case because I had pitched the tent on a dry spot, relatively, thunder was booming in the distance, then it started to rain, then almost immediately, a heavy hail (3/8 inch or so), I got in my tent, zero time for condensation to form, and the misting started instantly, it’s very clear and defined, nothing to do with condensation, so if you read people trying to pretend this phenomena is just inner condensation getting knocked off by the outer rain, they don’t know what they are talking about, but probably think they do.

In an unrelated heavy rain in Norway discussion thread Eric Blumensaadt gave this excellent short summary on how to treat your silnylon to fix the misting problem, I’ve read several, and this one seems to be about perfect, thanks.

Re-coat the silnylon tent with a 5:1 ratio by volume of 5 parts of odorless mineral spirits to 1 part clear GE Silicone II (or European equivalent). Place in a suitably sized jar with a tight lid. Shake well to mix and shake every 5 minutes while using.

Apply in sections with a very short nap, narrow paint roller – pour small amounts in a roller pan. You can also use a fine bristle brush. Spreading the tent sections on a smooth top table is far better than using the floor.

BE SURE to wipe the excess off each section immediately with a heavy duty paper towel (“shop towel”). Rolling on the mix is faster and gives a more even coat than brushing. Wiping immediately after leaves only the necessary amount on the silnylon, thus reducing weight AND GREATLY REDUCES DRYING TIME by days. Silnylon floors or ground cloths (“footprints”) can be coated twice using this method for a heavier coating.

BTW, this procedure will seal the tent exterior seams but I would recommend also coating the interior seams as well. If seams ever leak after this treatment (doubtful) use a 3:1 ratio of mineral spirits to clear silicone caulk for re-sealing. Do NOT wipe this seam seal treatment. Just let it dry in the hot sun. The Netherlands does have hot days, right? My experience with Dutch weather was in late October when it was cold and rainy.

I didn’t want this little gem to just vanish in the never ending churn of gear talk etc on, so I am saving it here so it doesn’t get lost.

Technically, I believe you can use Coleman white gas type fuel instead of the mineral spirits, and I believe silicone cures better in humid climate, though I’m not positive about that. Also of course, it’s hard to use rollers if you don’t have a big work space.