Light (<2oz) urethane coated nylon

Colin,

Going from memory here – checked all of the Pertex line? Seems like they had a couple different light urethane fabrics at one time.

Ryan

I was just searching for some fabric on Ebay the other day that you might want to take a look at. There are various colors and they are all listed as waterproof, PU coated nylon with a weight of 70gsm which works out to just about 2oz/sqyd. However, I have never used this fabric so I am unsure of the quality or the accuracy of these measurements. Some of the fabric can be found Here.

Chris, thanks. Your link doesn't work for me, but I searched for it on ebay and found it. I don't know how I missed it before. That's exactly what I was looking for. Thanks again.

You're right, for some reason the link is no longer working for me either. It is possible the ebay listing was taken down. Glad you were able to find it however!

I hope you don't mind but I have to inquire about the purpose of this fabric. Is it for use as a tent floor?

It's for a gravity filtration water bag.

Ah gotcha. I knew it had to be intended for something that would be subjected to pressures too high for sil-nylon's HH. Let us all know how the fabric works out. I'm intrigued to know how waterproof the fabric is, and an accurate measure of its weight.

Colin,
Some of the < 1.5 oz silnylon can be had with HH around 3Kmm.
Much of the PU of that weight is said to be less than half that. Big Agnes, for example, regarding their own products.

So am doubting the HH is the issue as suggested by another post; rather, maybe it is the need for a tight seal on the water bag seams. Would be interested to know if you think the PU will give a better seam seal, and if so, how and why.

I've got some TNF PU around 1.6 oz, and some Warmlite about the same.
Problem is, the fabrics were made over ten years ago, and the PU degrades over time.

One Planet is currently making tents with 15 den PU nylon, but don't know where just the material can by obtained. It's out there, though.

Yes, HH for some kinds of silnylon (like Thru-hiker's Shield) is good, and tenacity per unit material weight is much better than PU nylon, but PU nylon can be easily taped and a urethane elastomer valve can be easily bonded to it.

My current silnylon water bag has a vinyl kite valve (from Airtime Kites) bonded to the bottom with silicone, and it looks sloppy and I worry about the strength of the bond. A PU nylon water bag could have tidy taped seams and a TPU valve neatly bonded to the bottom, and bond strengths would be better. The PU wouldn't be as resistant to UV or hydrolysis as silicone, though, as Samuel mentioned. I'd like to try it.

Colin,
Looked through Extrem Textil's offerings, but as in the US, only the silcoated nylons get down below 2 oz with a high HH. They have plenty of light PU coated nylon, but are quick to note that it is not WP. If you could find it sold separately, you could probably use a material like the low denier nylon with a WP PU coat such as that used on the recent GoLite and Mountain Hardware Super Omega tents, as well as the One Planet tents from Australia that I mentioned.

I doubt that the older stuff I mentioned would hold up to continuous water pressure.
What I've seen on the market are nylon outer bags for strength with welded plastic (polyethylene probably) bag liners for waterproofness. But if I run across anything, will let you know.

Colin,

For what you need, I would suggest the 30D heat sealable nylon that Seattle Fabrics sells. It is 3oz per sq/yard, but if you are looking to weld valves to the fabric, you are going to burn through a standard waterproof PU coating prior to getting the desired adhesion.

In the alternative, you could take off the shelf nylon fittings with threads to eliminate the need to weld a valve to the fabric see the examples here http://gear-report.com/how-to-make-a-diy-gravity-water-filter-for-backpacking-camping-survival-emergency-myog.

Marc, actually, I tried using heat to weld a TPU valve to the 30D heat sealable nylon from Seattle Fabrics. It didn't work well. I suspect that the TPU of the valve has a different softening temp than the TPU laminated to the nylon.

I plan to bond the valve to the fabric with urethane adhesive, and I'd like something lighter than the heat sealable stuff. When I used the heat sealable 30D from Seattle Fabrics before, I found that the real weight was close to 3.3 oz/yd. I'm even considering designing my own valve, fabricating it in wax, making a bottomless silicone mold, and casting the new valve directly on the fabric (and cutting out an orifice later).

Colin,

Assuming you don't cast your own valve, what kind of TPU valve will you use? Pic? I have been contemplating a gravity bag lately.

Ryan

Ryan, I have a couple of blue TPU valves that I removed from two 1980s era inflatable sleeping pads. They are fairly similar to kite surfing valves from Airtime, but a bit more squat. I'll take a photo of one of them and post it when I get home this evening.