Thread, water proof fabrics and pvc.

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I heard someone talk about sewing tents, and they had found an extra strong thread that expands when it becomes wet. Has anyone heard of this before? The expanding part prevented water from leaking through seams.

I first thought it might be practical when sewing transparent pvc and bike seat covers. I came to think of shoemaking, but I think they use waxed thread, double seams and a general shoe wax to keep water from seeping in.

[BrendaP]

I found this article about sewing tents.

My earliest forray into using a sewing machine was helping my Dad to make a tent, about 60 years ago!

He decided that the most ecconomical way of obtaining a good size tent for family holidays was to make one, even though it meant buying a sewing machine as well.  (The machine was a black hand-crank Jones with a long shuttle bobbin, but alas I don't know what happened to it).  I can remember turning the handcrank for the never ending felled seams.

I also remember that he bought yards and yards of canvas, which I think was linen, and some special strong thread.  I'm pretty sure that thread would have been linen, but knowing what I know now about linen thread most of it is less suitable for machine stitching because linen thread is nearly always S twisted and you need Z twisted thread on a sewing machine.  The direction the bobbin turns will tighten a Z twist and loosten an S twist.  Maybe the slower speed of hand crank, or maybe the vibrating shuttle made it less of a problem.

Linen and cotton both absorb water which means that they expand when wet.  The advantage of linen is that it is actually stronger when wet than when it is dry.

Some of the linen threads here are described as reverse twist.  I *think*, but I'm not certain, that means that they are Z twisted to suit sewing machines.  35/3 or 40/3 sizes are similar thickness to top stitch thread.  The other sizes will be somewhat thicker.

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Sounds like a very fancy tent, linen is the most durable next to a hard woven nylon fabric, much more expensive too. You gave me an overload on info here, but I think I go the essential; linen thread needs to be particularly for machine sewing, natural fibers expand when wet. Maybe it was a linen thread they taked about. I know those who stitch leather by hand use all kinds of special threads.

[sewmuchmore]

this is the thread i used for sewing the waterproof vinyl seating on our boat and used it when making the canvas covers. It is a heavy weight thread but you can get a lighter version V69 or try Gutermann Tera 60.

[BrendaP]

Sounds like a very fancy tent,

No it wasn't fancy, it was a very plain shaped ridge tent but it was big - about 6 feet high (nearly 2m) in the middle and room to sleep four and still have room for all the other stuff inside.  The poles were made of wood which my Dad turned on his lathe.  We had quite a few holidays in it but I don't think there are any photographs whic include it, I don't have any.

So long as we didn't touch th esides when it was raining it was waterproof.

[Bodgeitandscarper]

I would have thought if you use cotton or linen thread, the water would actually seep through the thread?  Modern nylon tents are always seam sealed - or the proper ones are, I doubt they bother on the supermarket tents!

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I guess felled seams with linen or cotton are water proof when waxed. The expensive light weight telts handles storm, rain and all kinds of weather, the less expensive are usually water proof enough when it says so on the lable, but they can't sand up to the harshest conditions.

I wasn't thinking of seam sealants particularly, I have had a few that just fell off after a bit of use. Some are like a glue that's brushed on, some are a sort of iron on ribbon. I will probably end up using a regular polyester thread unless I need something completely waterproof.

Thanks of the links and suggestions, the problem with water proof seams turn up from time to time.