spectra fishing line for thread?

You might want to test Spectra's elasticity (almost none) against whatever fabric you would sew with it. In applications that repeatedly stress seams, it seems better to match or approximate the elasticity of the thread and fabric. Otherwise one will saw against the other and the one that has the highest tensile strength or the most abrasion resistance will win. This can be a problem, for example, when light polyester thread is used on nylon tarps; the nylon can stretch, popping the thread. A stonger, low-stretch thread can open up the stitch holes in light fabric. IOW, you might want to test before committing the fate of a project to an unknown factor.

thanks. I think that was the answer I was looking for. So what would you recommend for a ultralight fabric such as silnylon or spinntex?

I have been using Rasant 120 poly-cotton thread on my summer and winter tents. The seams have taken a hammering OK.

Cheers

Does that need seam sealing Roger? Or is it like the cotton combo thread Golite use which swells when wet to seal the thread holes?

Well, the way I design my seams does mean that they don't really leak under reasonable load, which is nice.
The thread is a polycotton, and the cotton fibres will swell *slightly*, but frankly I don't believe the story that some threads will *really* swell up enough to seal the needle holes.
So I seal the seams with silicone anyhow!

There's a reason of course. Imminent thunderstorm late in the evening, with severe winds building up. We made it to a known flat open area where falling (big) trees would not hit us (serious concern here). I hastily started to put my new (MYOG) tent up as the rain came down. Sue got inside quickly while I looked after the guys. By the time I got inside we had an inch of water on the ground and the bathtub groundsheet was floating. Yeah, floating. Kinda amusing.

Well, that was OK, but as the storm continued I realised that the ridgeline was very slowly dripping. AARRGGHH! Traumatic! Actually, the amount was not serious, and storms like that one are always short-lived, but ever since then I have been a shade fussy about leaks …

Rasant is by Amann of Germany, so it should be available in the UK.

Cheers

Good story.

My unsealed Hex 3 hasn't leaked a drop in several windy downpours, so I guess Golite are onto something.

Thanks for the thread name, I'll see if I can get any.