Trying to decide what tent to make & going crazy over it

[Roger Caffin]

Hi Bender

Rasant is an industrial thread made by the German Amann group:
http://www.amann.com/en/industrial-sewing-threads/rasant.html
They even have a web shop!

They also make pure polyester Serafil. This may be slightly stronger, but I found that it has problems in a domestic machine (eg kinking).

OK, very brief primer on sewing thread technology. Btw, you probably won't get any of this from a young salesman in a shop. They just wouldn't know.

Sewing thread can go through a needle at fairly high speed – and this can happen even when you are sewing on a domestic machine. The eye of the needle is highly polished (how to do this well is an arcane art known to few) to minimise friction, but even so, there is friction. And friction makes heat. OK, you are sewing away, the needle gets a bit warm, then you stop. All of a sudden the thread is sitting up against a hot needle. What happens?

Yep, it can melt slightly if the thread is all synthetic. Then when you start the machine again there is a terrible mess and the thread breaks. Bad enough at home, but hell on a production line. What to do?

Well, the standard response is to use a poly-cotton thread, but it has to be the slightly more expensive 'core-spun' variety, not an el cheapo simple mixture. What this means is that the core of the thread is nylon or polyester, and the cotton fibres are on the outside surface of the thread. They do two things there during sewing: they reduce the friction through the needle and they prevent the synthetic core from getting too hot and melting. Yep, natural fibres do have some advantages!

In practice, a good core-spun poly-cotton thread of a given gauge has nearly the same strength as a pure polyester thread of the same gauge. Yes, I have tested this myself.

Now, what happens when a poly-cotton thread gets wet? No, it does not lose any significant amount of strength, but the cotton layer can swell up a *little* bit and help seal the stitch hole against water. Don't rely on this though: seam seal!

Some cheap (Chinese) stuff is made with a cheap cotton thread. This stuff breaks down fairly easily – I am not sure why, but it does. So nobody who is anywhere near professional uses plain cotton thread in any critical application these days. It does get used when the manufacturer wants to dye the finished (cotton) garment.

You can use a bonded nylon thread for slower heavy-duty sewing, but you need to use a large needle (larger hole, less friction) and it helps to have a lubricated thread too.

The cheap polyester thread sold into the consumer market is sold on price, to people who sew consumer fabrics at slow speeds. It is not really meant for the specialised synthetics we use in gear. On the other hand, I am happy to use Gutermann or Metrosene thread on the Taslan fabric I make into our clothing. It is matched for weight there.

I buy Rasant at my local specialised sewing shop. They stock it because they have many customers who know enough to want it. They don't promote it – they don't have to.

OK, onwards.

Critical areas: the main stitch lines in the pole seams, the guy rope anchors, and the bits of tape or webbing at ground level which hold the poles etc. Yes, a good guide is most reinforced areas.

On the other hand, if you are sewing netting onto silnylon, you are hardly likely to need Rasant 75: the 120 will do fine. Something like 12 – 16 stitches per inch please, not coarser.

No, Rasant may not seem to be cheap. Funny about that. But if you are going to spend 100 hours and hundreds of dollar building a tent, should you be skimping on the thread which holds it ALL together?

Cheers

[Miguel Arboleda]

Roger, I have been sewing my own tarps and simple tents for years, but never knew this about threads. Thanks so much for the primer. This one comment alone is going to make a huge difference for me. I'm copying it and pasting it as documentation!

[>> Bender <<]

Roger again thank you for the priceless information! Can you tell me what size needle works best with Rasant 120? I was planning on getting something like size 70 sharp. I was looking back on your post in my stuff sack making thread and the seam sewing information is helping a tremendously, so thanks again. I'm ready to start cutting fabric but I'll have to wait for thread and needles to get here for assembly. I would like a different color thread than my gray material but since I am new to this, my seams aren't nice enough to show off!

[Roger Caffin]

Hi Miguel
My pleasure.

Hi Bender
I use a #60 sharp with Rasant 120. Many How-To books or advice columns will say to use #70 or #80, but that is going overboard on the safety side (ie don't break thread or needle). You can run Rasant 75 through a #60 needle quite happily if you don't go too fast – I often use that combination myself.

To match or contrast thread colour – ha! But note that black thread will last a lot longer than light-coloured thread as it UV-degrades much more slowly. The yellow dyes in particular seem to be very sensitive to UV. Some of them can make the fabric go brittle after a while it's due to the chemistry etc etc etc.

Cheers

[Ethan A.]

Is Permatex Silicone Windshield Sealant better than Mcnett Silnet? Where did you read/hear of this? Have to seal up a tarp tent soon.

The sewing thread and needle information is very helpful as I'm planning on modifying an existing design soon.

Anyone know how http://owfinc.com/ compares with Seattle Fabrics for price on fabric and materials?

[Ken Thompson]

EJ Look here
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=29884

[Ethan A.]

Thanks Ken, looks likes that stuff was made-to-order.

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