Bushwalk Australia

Hi All, I am looking for help with making my pyramid or bell tents with un-coated and breathing polyester woven fabric (umbrella fabric) and would appreciate suggestions from those who have 'gone before me'.

Sorry if there is an existing topic and I have just not been able to search properly for it. Please point me to such a post if I have missed it.

I am able to make strong, light and comfortable tents with silnylon (even if the stitching of the slippery silnylon is a bit ugly). They are 'walk-in tents for two and a tent stove and gear storage when the 300mm bell wall is deployed (as in the first photo below). They become a bomb-proof cramped stooping-walk-in tent for the survival of two under adverse weather conditions (as in the second photo). The only negative issue is the dreaded condensation inside on some nights. When it combines with buffeting winds, it is like having fine misty rain inside.

I should also add that I have no formal floor sewn into my tents (I use separate light groundsheets instead.) so that they can easily accommodate a tiny tent stove. They do have generous breeze/bug/snake/snow skirts around the whole base, so if any water should wick down the surface, it would not be an issue. For more details please see my website post on the tents:
https://timtinker.com/ultralight-tent/





I have done a little side by side test of scale model pyramid tents that were pitched for about a week at home on my green moist lawn, where water transpiration was guaranteed. (sorry I can’t find the photo). Both had no floor, one was made of silnylon and the other of un-coated polyester (fashioned from an old cheap but colourful umbrella).

They both shed the rain well with no apparent leaks. Each morning, the silnylon tent was always coated with much condensation inside and the polyester tent was always dry. Even when I put a large dinner plate of water at the bottom of the polyester tent, there still was no condensation.

My question is: Can polyester without waterproof coating or silicone rubber impregnation provide a waterproof shelter without condensation issues? I would treat the seams/stitches with diluted acetic cure RTV silicone rubber to make polyester/cotton sewing thread repel water.

I would like to hear from others about their experience with using un-coated polyester for single skin tents. Tim

Hi Tim,

I have no direct experience of uncoated polyester tents. I sometimes bring prospective diy fabrics up to my mouth and blow/suck through them to test their permeability and suitability for my intended purpose. Just take care in the fancier stores!. You could probably do a more scientific pressure column test. I am building a skin on frame kayak with an uncoated polyester skin but that will be coated after heating shrinking on the boat.

It sounds like crazy question, can a fabric without waterproof coating be waterproof. But it may well be the case that the DWR coating will serve to repel rain, up to a point. And only as long as the DWR lasts.

You don't even need to get too scientific about it. Take a big square of fabric, gather it so that you have a kind of bag, then fill that "bag" with water. Observe.

Orion wrote:It sounds like crazy question, can a fabric without waterproof coating be waterproof. But it may well be the case that the DWR coating will serve to repel rain, up to a point. And only as long as the DWR lasts.

You don't even need to get too scientific about it. Take a big square of fabric, gather it so that you have a kind of bag, then fill that "bag" with water. Observe.

Hi Orion, Most innovations start with apparently crazy questions (according to those who are stuck in the rut). That is how we have been able to move out of the cave to tents and houses! There is no such thing as a stupid question it is usually the answer to the question that is demonstrably stupid.

I have not proposed anything 'scientific' in support of my tent idea. On the contrary, I described a simple side by side test of scale mode tent made of umbrella fabric or silnylon and observed what happens. This was not so different to your suggestion of making a 'bag' of the fabric and filling it with water. "observe'. That is exactly what I would do if I was making a water bag, but I was wanting to make a water shedding device called a tent.
Tim



For thousands of years, unproofed cotton fabrics and similar have been used for comfortable and dry tents way before the invention of synthetic fabrics.On the other hand, your suggested 'scientific' test of a kind of bag of may be appropriate for testing a fabric

Not waterproof but unproofed fabric can shed water.
Parachutes are very LW and the old style were relatively porous compared to modern stuff and could be used to make highly water resistant emergency tents in the tipi style.
It was a combination of steep walls and at least 2 layers of fabric well separated that allowed such structures to work.
Ditto early tents
Not sure that helps tho

Moondog55 wrote:Not waterproof but unproofed fabric can shed water.
Parachutes are very LW and the old style were relatively porous compared to modern stuff and could be used to make highly water resistant emergency tents in the tipi style.
It was a combination of steep walls and at least 2 layers of fabric well separated that allowed such structures to work.
Ditto early tents
Not sure that helps tho

Thanks Moodog, Very constructive. I will be trying it as a single skin tent to see how it goes. Tim

For sure there are stupid questions. I'm not saying your idea has no merit, simply that you have little hope of achieving a high degree of waterproofness. You already know the fabric sheds rain to a certain extent. My non-scientific suggestion was simply an easy way to test the limits.

My partner's pack cover wetted through during a recent storm. Back home it appeared to shed water just fine. But the bag test showed that under stress it leaked like a sieve. It was still fine for light rain but worthless in more serious weather. We replaced it.

Orion wrote:For sure there are stupid questions. I'm not saying your idea has no merit, simply that you have little hope of achieving a high degree of waterproofness. You already know the fabric sheds rain to a certain extent. My non-scientific suggestion was simply an easy way to test the limits.

My partner's pack cover wetted through during a recent storm. Back home it appeared to shed water just fine. But the bag test showed that under stress it leaked like a sieve. It was still fine for light rain but worthless in more serious weather. We replaced it.

Hi Orion and others, I have now done quite a bit of backyard testing of the polyester tent including side-by-side testing with an equivalent silnylon one and it has performed without fault so far:
No rain leakage on long wet nights,
Much less condensation than with an equivalent silnylon tent,
Worked well on two sub zero nights up on the Bogong High Plains, froze inside and out,
Survived very strong and gusty winds,
Packs up as small as the silnylon tent,
Did not go saggy like the silnylon tent and needed no pitch adjustment over two days and nights
Weighs about 100g more than the silnylon tent, and
Dries very much more quickly compared with silnylon.

For more details of the tent testing, please see:
https://timtinker.com/diy-breathing-polyester-tent-for-backpacking/




Here is a video tour during heavy rain:
[youtube]v=W47QauLAXgs[/youtube]

Tim

Hi All including the sceptics, The tent continues to perform well in all seasons for extended backpacking walks. No condensation problems (compared to my silnylon equivalent) and the outside of the tent dries quickly for early morning pack ups.

Tim

Orion wrote:It sounds like crazy question, can a fabric without waterproof coating be waterproof. But it may well be the case that the DWR coating will serve to repel rain, up to a point. And only as long as the DWR lasts.

You don't even need to get too scientific about it. Take a big square of fabric, gather it so that you have a kind of bag, then fill that "bag" with water. Observe.

Hi Orion, I thought you might like to see the results of filling a silnylon bag with water. Not exactly waterproof! I have stopped using silnylon for tent canopies and was using it to make an ultralight 'hot bush shower'. Does not leak fast enough for a good shower. Tim



Maybe this video is more convincing if you think that I may have sprayed the bag with water, just to make my point.

There is silnylon and there is silnylon...
Anything from 500mm to 5000mm waterhead so don't judge all silnylons from one test or two.
Years ago I took this photo . That silnylon was rated at around 1500mm.
I don't know how many gallons of water I put in there but I think you get the idea.( no it wasn't dripping hours after....)

( I found my comments about that photo, I had 16 litres of water in there)

Exactly.

I had posted previously about a home made pack cover that repelled water but leaked when subjected to any significant water head. But that was not an argument for avoiding silnylon. The pack cover was about 10 years old and had seen a lot of abrasion. It was simply worn out. From the same silnylon source I made a tent that, ten years later, still keeps me dry in the rain. The fabric is just as old but hasn't had the same sort of physical abuse.

Our Hilleberg tent is also made from silnylon, a superior version of it as compared to the no-name factory 2nds silnylon that I purchased from a fabric store for MYOG projects. That tent is 13 years old and could probably use new main zippers for the fly but it's still quite weatherproof.

Franco wrote:There is silnylon and there is silnylon...
Anything from 500mm to 5000mm waterhead so don't judge all silnylons from one test or two.
Years ago I took this photo . That silnylon was rated at around 1500mm.
I don't know how many gallons of water I put in there but I think you get the idea.( no it wasn't dripping hours after....)

download.jpg

( I found my comments about that photo, I had 16 litres of water in there)

Hi Franco, Thanks for your insight. Yes, I agree that there is probably a big range of silnylon qualities. Mine is evidently on the low end (described as cosmetic seconds from Oware I think). Mine failed at about 250mm when new off-the-roll! Imagine how bad it would be after 10 years of rough real use! Nevertheless, I made my first silnylon tent from it. It has been very serviceable (rain waterproof) for many years and for many nights out.

My only complaints were the condensation that it collects inside (can't breathe), the stretching when it gets cold and wet (property of nylon) and the slow drying under early morning cold conditions (nylon is a hydrophilic polymer). I have not yet done a similar HH test on my preferred tent fabric (breathing polyester that is one of the most hydrophobic polymers) but will do so soon and post. However, I hasten to say that I think this HH test is irrelevant for testing a tent fabric IMHO. My reason for posting the leaky photo was to point out this issue to Orion who had suggested this HH test when he was negative about my use of non-waterproof polyester fabric for my tent. My polyester tent does not leak rain drops and has none of the above listed problems of a similar tent made of silnylon. For me, this is a major improvement for backpacking functionality of a MYOG tent. Tim

telemarktim wrote:My reason for posting the leaky photo was to point out this issue to Orion who had suggested this HH test when he was negative about my use of non-waterproof polyester fabric for my tent. My polyester tent does not leak rain drops and has none of the above listed problems of a similar tent made of silnylon. For me, this is a major improvement for backpacking functionality of a MYOG tent. Tim

It's well known that polyester has the advantage over nylon in terms of water absorption and consequent stretch. Polyester is weaker than nylon, so there is that tradeoff to consider, depending on the context. The real question here is whether an uncoated polyester fabric is sufficient for wet conditions. Your anecdotal testimonials are insufficient to establish this.

What fabric, specifically, are you using?

Orion wrote:

telemarktim wrote:My reason for posting the leaky photo was to point out this issue to Orion who had suggested this HH test when he was negative about my use of non-waterproof polyester fabric for my tent. My polyester tent does not leak rain drops and has none of the above listed problems of a similar tent made of silnylon. For me, this is a major improvement for backpacking functionality of a MYOG tent. Tim

It's well known that polyester has the advantage over nylon in terms of water absorption and consequent stretch. Polyester is weaker than nylon, so there is that tradeoff to consider, depending on the context. The real question here is whether an uncoated polyester fabric is sufficient for wet conditions. Your anecdotal testimonials are insufficient to establish this.

What fabric, specifically, are you using?

Hi Orion, Yes, my evidence is anecdotal and that surely is the nature of the stuff that is shared freely on a MYOG forum such as this. If you looked the boring detail in my full post you will see that the tent made from polyester has stayed dry during days of heavy rain. I will leave others with more open minds to judge its sufficiency for wet conditions for themselves. Tim

telemarktim wrote:If you looked the boring detail in my full post you will see that the tent made from polyester has stayed dry during days of heavy rain. I will leave others with more open minds to judge its sufficiency for wet conditions for themselves.

That is offensive that you are implying that my mind is not open, particularly when in my first post I said that it was quite possible that you could achieve some degree of water resistance. You report that a particular fabric works for you. The question is: what are the limits?

I asked about the specific fabric. I had forgotten that in your original post you said it was salvaged from an old umbrella. So we don't have details. Fabrics are complicated: weave type, yarn weight, thread density, calendaring, DWR, etc. Surely you are not making the case that all uncoated polyester fabrics are sufficiently water resistant for this application.

Next time I buy some fabric I'll include an order for a yard of generic uncoated polyester and fashion a model of a simple pyramid tent. As a control I'll make an identical one out of the cheap silnylon I use sometimes and then give them both 5-10 minutes spray with the garden hose.

Orion wrote:

telemarktim wrote:If you looked the boring detail in my full post you will see that the tent made from polyester has stayed dry during days of heavy rain. I will leave others with more open minds to judge its sufficiency for wet conditions for themselves.

That is offensive that you are implying that my mind is not open, particularly when in my first post I said that it was quite possible that you could achieve some degree of water resistance. You report that a particular fabric works for you. The question is: what are the limits?

I asked about the specific fabric. I had forgotten that in your original post you said it was salvaged from an old umbrella. So we don't have details. Fabrics are complicated: weave type, yarn weight, thread density, calendaring, DWR, etc. Surely you are not making the case that all uncoated polyester fabrics are sufficiently water resistant for this application.

Next time I buy some fabric I'll include an order for a yard of generic uncoated polyester and fashion a model of a simple pyramid tent. As a control I'll make an identical one out of the cheap silnylon I use sometimes and then give them both 5-10 minutes spray with the garden hose.

Hi Orion, I remind you of your own words: "It sounds like crazy question, can a fabric without waterproof coating be waterproof. But it may well be the case that the DWR coating will serve to repel rain, up to a point. And only as long as the DWR lasts. You don't even need to get too scientific about it. Take a big square of fabric, gather it so that you have a kind of bag, then fill that "bag" with water. Observe."

I have only commented about the fabrics that I used (not all polyesters, just cheap umbrella fabrics). The scale model tent was made from an old very used polyester umbrella. It was not coated and I don't know if it ever had DWR and the warp and weft threads appeared to be quite coarse. Importantly, my side-by-side tests showed that it did not form any condensation inside (as the silnylon equivalent did) and did not leak rainwater or heavy water spray from a hose.

My real tent was made with new simple woven very cheap polyester umbrella fabric. It was specifically custom manufactured with no waterproof coating or DWR, but it had a silver coating applied to one side and I was assured by the manufacturer that it would still 'breathe' moisture through this reflective coating (This breathing characteristic has been confirmed by my side-by-side tests).
It would be good if you do the test that you suggest. I will wait with an open mind to hear about your findings. Tim

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