Kevlar thread.

I have seen a lot of posts about using kevlar thread. Problem: As I understand it Kevlar is very vunerable to U.V. Something about it going brittle in 72hrs unless it has been coated. Comments please.

No experience with kevlar myself. Looking at the US and European forces are now preoccupied in the middle east: I havent heard of any UV problems... they cover it with textiles of course. What they were told is dont bang it around to keep it free of cracks.

I use spectra or spiderwire fishing line, which (since intended for outside use) is more UV stable. I've been able to sew with them, and have used the 30# test line to lash a shelter. Some knot choices don't work well on this line, but the spools usually come with instructions about this.

I took Doug's PSK pencil, put it in a drill motor, tacked the first row of Spiderwire with hot glue, and cranker 'er up! You can wind many yards of this line on that pencil and not increase the bulk that much. Then I finish the spool with a tiny strip of electrician's tape to keep it from unspooling.

I've never used kevlar thread, but can't imagine what it would give me that the Spiderwire won't.

Sorry, thought you were on about the bulletproof stuff not the thread... <img src="/images/graemlins/crazy.gif" alt="" /> <img src="/images/graemlins/blush.gif" alt="" /> <img src="/images/graemlins/tongue.gif" alt="" />

Spectra is pretty ideal but it suffers from one weakness: creep. It will stretch under a sustained load. I have no idea how much Spectra fishing line will stretch or what kind of load will stretch it, though. So, maybe your A-tent will be hanging a bit lower after a couple days. <img src="/images/graemlins/grin.gif" alt="" />

The link below is a BYU paper on the use of these materials, mostly related to reinforcement fibers, but at the end of the paper there are tables of properties. Properties of Kevlar & Spectra

I'm still not sure of the UV sensitivity of Kevlar. I know sailmakers noted a problem but then Kevlar is used for lines in both parachute and paragliding wings. For now I'll stick with Kevlar as it is fire resistent, where Spectra "burns readily".

Bare Kevlar does degrade significantly when exposed to UV. As dbeeksci pointed out in a different thread, high performance racing sails are often made of Kevlar. Sailmakers try to protect it in various ways, like with mylar skins and various UV coatings, but I've read that once a Kevlar sail is "sunburned" and turns from gold to brown, it has lost about a half of its original strength. Then again, Kevlar starts out about 5 times stronger than a Dacron sail, so it's still going to be strong. I'm not sure if UV degradation actually makes Kevlar more likely to fail catastrophically (e.g. brittle and snap) or if it just not as strong as original.

That said, I'm not sure if this sailcloth info has much bearing on using Kevlar thread as a paracord replacement in a survival situation, though, so YMMV.

I don't think it is a particular issue when used in a North European climate, at least in terms of short term usage. It might be a problem in a desert or tropical scenario. Hence the question. Oh, and the stuff in the bullet proof vests is exactly the same material. The reason why you dont drop the vest is that dropping it might fracture the top layer ceramic trauma plate(s).

Of, it is. It is lots and lots of layers of cloth made by weaving the threads, and quilted, that are bullet resistant. (Armour can be beaten by a bigger weapon.)