An idea for the lightest, warmest sleeping pad ever

>Ever made a good double lap seam with silnylon?
http://www.hilleberg.se/images/allmin1.jpg

no. But it looks pretty tough seem. I was planning to use french seam for my gear. Any advice on seams?

A French seam you use when you don't wanna see the seam or when you have transparent fabrics. This is not the best seam for a tent. Even for seams with less loads i wouldn't use this seams. There i would use a folded or welted seam.
For high load seams i would use this lapped-fell/ flat-felled seam/double lapped seams. Sry found several translations for this one.

Greetings from Germany
Oliver

> Ever made a good double lap seam with silnylon?
> http://www.hilleberg.se/images/allmin1.jpg

I don't know how you get to that pic, but I don't believe it anyhow. Not exactly as it is shown, anyhow.

Cheers

Why do you not believe it Ô.o?

I've googled a bit and found this on the "english"web.
http://www.garmento.org/751Astitchesandseams/LSc.htm
http://books.google.de/books?id=BKTuTXrXQu0C&pg=PA482&vq=gbs_search_s&sig=hwy8DDtOwSc1XBI9GONnXHF7vd4
http://www.the-needles-eye.com/NewReleases/35800/35800DNUB/35800DNUB9.htm

As you see in industrial use there are special machines that only sew this LSC seam. But it works also on home sewing maschine. But it would need some training. Silnylon won't make it easier ^^

If you still don't believe it, than I can grab my machine and make a sample and photos of it. I have a normal domestic machine without any special folding attachment. Not even a twin needle.

Roger here you find all kind of seams:
http://www.amefird.com/seam_type_matrix_flyer2.pdf

Oliver

Roger,

it might be a realistic picture for an industrial sewing machine not a domestic one.

Pfaff do produce a foot that is designed to help with felling seams on a 'domestic' machine by folding fabric as you go.

I've looked at seams on commercial tents and in general it does suggest that they were sewn with a twin-needle. It's very difficult to sew perfectly parallel seams.

Is this the correct double lap seam?

Why don't I believe it (as it is shown EXACTLY)?

Because I have spent maybe 10+ years making UL tents out of silnylon and other UL gear out of a range of fabrics. Trying to make that EXACT seam in a UL fabric like silnylon is a nightmare – especially on curved edges.

Yes, I do have seaming feet for at least one of my sewing machines. You can make it work with some stiffer fabrics at low speed. But dimensional stability is not great.

However, if you make the seam in a two-step process as Huzefa shows, then it is easy. But the original pic does not show the first line of stitching, and it is that lack which prompted my disbelief for UL tent fabric.

Cheers

Well you are right on (narrow) curved shapes its hard. But when you straight edges it works good.
At the moment i am sewing my second lavvu/tipi/teepee and i am using this seam.
Some glue may also help (for the beginning)

Oliver