Tarp fabric resistant to hail and extreme weather

I don’t know if this might help anyone, plus I don’t know much about deniers or fabrics.

I’ve owned a Chouinard Pyramid since the mid ‘80s. The shelter alone weighs 41 ounces. It is PU coated nylon. I don’t know what the specs are, but I just looked it up in Colin Fletcher’s Complete Walker III, and he wrote it is 1.5 ounce waterproof ripstop nylon. Back then this could have been weight before or after waterproof coating, I suppose.

Anyway, the PU coating was delaminating, the zipper broke the last time I used it, and the long Velcro zipper flap closure was coming apart. I really didn’t want to get rid of it, but it would probably cost as much to renew it as buying a similar new pyramid, especially since a long zipper like this is apparently a big job, plus I don’t sew or have access to a sewing machine.

Anyway, while thinking and researching for a new shelter, I wrote an “obituary” for the shelter on my blog. Then I ordered a new Black Diamond Mega Light, which is almost identical. There are several large mids on the market that are almost identical to the Chouinard in size and design. Most are 30d silnylon and all weigh around 26 ounces versus 41 for my old PU coated shelter.

The Mega Light arrived and the design (cat cut) and dimensions are identical to the old Chouinard.

Right after I got the new Mega Light and seam sealed it, Patagonia Worn Wear contacted me and offered to repair the Chouinard for free (Black Diamond was originally Chouinard Equipment). But they couldn’t renew the waterproofing. I accepted their offer, and decided I would recoat it myself, which I originally planned to do anyway.

I washed it in Joyce’s washing machine (for those who know Joyce, don’t worry, I got the necessary appliance permitting ahead of time). This removed most of the PU coating. I pitched the shelter inside out (easy with a mid) to let it dry and ensure all the old PU was removed. There was some powdery residue left, so I adjusted the guys to make it taut so I could clean all the panels with a soft brush. That did the trick. Then I thoroughly rinsed it with a hose . . . Oh yeah, the coating was gone, and I couldn’t believe how much the entire shelter sagged, it looked like it was going to collapse on itself. Keep in mind the shelter has four sides and each is about 110 inches long.

After it completely dried, I readjusted the guy lines and brushed a single thin coat of tent PU coating. Let it sit outside for a couple of days, then set it up right side out to seal the seams (from the outside per the instructions). While it was drying, I set up the new Mega Light to compare. The wind started up, maybe a steady 15-20 mph and the Chouinard hardly bowed in, while the 30d silnylon Mega Light had considerable bowing, although nothing I would worry about on a trip.

I left both shelters out for a couple of days. Each night and morning the automatic sprinklers water the lawn. In the mornings the new silnylon shelter had sagging, but the Chouinard very little. The PU coating gives the fabric a stiff feeling, but not too much, as I can still put it into the stuff sack as normal.

The difference in tension after sitting all night and exposure to a lot of water is significant between the two shelters. I don’t know if it is a combination of heavier nylon and the PU coating, the nylon alone, or just the PU vs silnylon.

Anyway, here are more details.

Obituary: Chouinard Pyramid 1985-2020

New Mega Light

Resurrection: Chouinard Pyramid Rises From the Dead

you have a lawn?  and you sprinkle it???

I’m amazed

(this is chaff isn’t it?)

hmmm, maybe heavier nylon and/or PU sags less?  I guess that’s your point.  What did you use for PU coating?

Patagonia’s Worn Wear program sounds amazing, Nick. There’s nothing like that outside of North America.

What did you use for PU coating?

TentSure. It is explained in the “Resurrection” link.

I have a Hilleberg Niak for above treeline treks where I am expecting dodgy weather.  I believe the fabric is a 20d and it has held up to hail, driving rain, and a foot and a half of wet snow.  Fabric still looks new.

So I am not sure the denier is the absolute determinant of fabric strength.  I suspect it helps but the weave is more important than the thickness and as well, how much waterproofing it actually has (i.e. PU or Silicone, etc).

We had a similar thread a few years back. I’ll just remind folks of my correspondence with Mike Cecot-Scherer, a veteran of the industry with over 250 lightweight tent designs to his name.

He has had the advantage of full access to the labs and repair shops of many of the big brands. He has also done some interesting wind-tunnel testing.

He is very much a fan of silpoly over silnylon. He believes that the lower stretch means it performs better in high winds because the shelter doesn’t spoon and keeps its shape, and that this is a real and significant advantage.

He is much less concerned with tear strength. First, he says that fabric strength will vary considerably from producer to producer and batch to batch, often more than the difference between silnylon 6.6 and silpoly. Second, he agrees with Dan’s point that the tests are done on unweathered silnylon, but in the field it degrades faster under UV and quickly loses its advantage. And finally, he says that according to busy repair shops issues with fabric failure are very rare, provided reinforcements are properly designed. Is his view, lightweight silnylon and silpoly are both relatively weak fabrics – in terms of strength there’s not much to choose between them and the best you can do is carry a good repair tape.

tests are done on unweathered silnylon, but in the field it degrades faster under UV and quickly loses its advantage.
Actually, I think it is some dyes which are most susceptible.
Anyhow, the answer is to not leave your tent pitched during the day.

My blue silnylon tent has seen many 2-month-long trips and many shorter ones over the years, with little or no degradation – but I never leave it up during the day.

Cheers

In DCF  obviously one looks to thicker versions that can be used (.74 to .8), but also the design as the wind shift will hit the exposed shelter more than the one set up in the trees.    I’d want one where a trekking pole would be placed point down and handle up after seeing wind bounce a shelter up and down.  Having DCF impales by a pole tip would be irritating though easier to repair than sil.  Note that framed lightweight tents bent until the fabric was in the sleepers face.   Either way bring earplugs in case it gets wild and windproof campsite (basically secure gear) before sleeping.

Then there’s the mountaineering oriented waterproof bivy (think MLDs eVent Soul bivy is still highly rated).  The bivy takes a bit of adjustment,  but people like to “cowboy camp” it seems, so it takes that to the next level.

Forgive me if you’ve heard this before, but I’ve tested numerous 1-2 oz/sq/yd (osy) coated fabrics stretched in 9″ dia. plastic embroidery loops to see how they respond to moisture.  For several years, laid them clamped flat over pails on the back deck.  Then switched to setting them upright in casement windows, exposed to weather between the window glass and the outside screens.  So long as rainy weather lasted most of a day or two, whether the fabrics were rained on, or just next to falling rain made for no noticeable differences in sag.  And they were often exposed to dew when it had not been raining at all.  All of the silnylon fabrics sagged and wrinkled when it was raining or dew was heavy. The fabrics that were silcoated on one side, and PU coated on the other (Sil/PU), sagged less, but still noticeably. The polyesters did not sag noticeably.

In addition to the above, flexible knitting needles, cut to fit, were placed in the embroidery loops to stretch the fabrics on the bias, sometimes with two needles crossed to stretch the fabrics in both bias directions. With the needles in place, the silnylons sagged only close to the perimeters of the loops, but remained taut over most of the fabric area during all the window tests.

A big concern was the effect of heavily sagging fabrics on comfort in a tent, or entering or leaving a tent, due to noisy flapping in the wind, and shedding water when wet in the rain, particularly in heavy winds.  And ultimately, as was mentioned, the threat of hypothermia.

Based on the above, tent models were designed to place canopies over a framework of poles that would stretch the main canopies on the bias over the sleeping areas inside the inner walls of a tent.  Silnylon was planned for those areas.  More recently, with the availability of highly water resistant polyester tent fabrics, attempts to deal with vestibule design led to the conclusion that slightly heavier silpoly ripstops were worth the extra weight for vestibules.  Still, slightly lighter Sil or Sil/PU fabrics would be used for the main canopies due to their greater strength, as shown in the chart posted above by William Chilton, which also jibes with my own experience using nylon vs polyester gear and observing wear and tear, and fabric failure while on many backpacking trips.

There was no concern about sun damage to nylon for the reasons expressed by Roger Caffin above, and also because if I were to need to occupy the tent on a stormy day, sun would not be an issue.

Re: “I’m less worried about damage that is expensive rather than situations that pose a risk to health and life.”

I’m worried about both, but of course agree that risks to health and life are of greater concern.  It is difficult to know what stresses will be placed on a tent, and what materials will withstand them.  So I think much guesswork is involved, because there is a large element of uncertainty. So as much as 7-10D fabrics will provide substantial weight savings in a tent, my guess is that 20D coated fabrics that hover over an ounce per square yard are a wiser choice than 7D fabrics around 0.8 osy, which for me is a small weight penalty considering the potential risks on a longer trek. (Note that the Rockywoods 7D that was spec’d at a lower weight, was found to weigh 0.8 osy by Richard Nisley in his tests posted on BPL.)

For those placing a high priority on going light, it is all about using equipment that is as light as possible without becoming Skurka’s “stupid light.”  It is always a crapshoot, but if we are careful, I think we can avoid the stupid part.

It is always a crapshoot, but if we are careful, I think we can avoid the stupid part.

That would at a minimum mean eliminating or reducing the crapshoot aspect of trip and gear planning in situations where the consequences of a bad roll of the dice would be unacceptably dangerous. Like having to break camp prematurely in a site far enough away from reliable shelter with only two hours of sleep and all your gear soaked because hail stones resulted in catastrophic failure in your shelter.

A considerable part of accepted UL technique hinges on eliminating planning for extremes. With the increase in extreme weather due to human causes, however, I wonder if there is a solid basis for revisiting that style of planning in certain categories, like shelter.

Hi Jon,
Re: “A considerable part of accepted UL technique hinges on eliminating planning for extremes.”

I was talking about shelter materials, intending to stay on piste (for once).
Re the above, I’ve found that the lighter I go, the more carefully I have to plan for extremes. I decide on my own BPL techniques, and by nature, do not run with the herd. If there is such a thing as “herd immunity,” it does not apply to BPL, and the folly of thinking otherwise is obvious from following many of the experiences related in the BPL forums.

On a related note, should have mentioned the RBTR sub 1 oz, non-ripstop membrane silpoly as a cautionary example of the risk of going too far with light materials. I’ve posted about how this material comes apart just in making scale tent models, an issue I’ve never had with sub 1 oz silnylons in MYOG.  To its credit, RBTR has a chart on its site stating that the tear resistance of membrane silpoly is low.  Would never suggest it for a mountain tent.

I’ve found that the lighter I go, the more carefully I have to plan for extremes.

+1
Thanks for sharing your valuable insights, Sam.

I’d like to revive this thread.

I feel a need to push back on the idea that “polyester is more resistant to UV degradation than nylon”.

Tap into chemistry here, and it really doesn’t make sense. You have an amide bond (nylon) and an ester bond (polyester). These are both organic bonds. Organic molecules are going to get destroyed when exposed to UV.

And actually, there’s a bit of research into this issue. Not a big difference between the two.

Where does that leave us?

Coatings.

You have sil (inorganic) and PU/PE (organic). Organic coatings probably aren’t going to fare well in response to UV exposure. Inorganic should be “more OK”.

So maybe we should focus less on nylon vs. polyester and focus more on coating chemistry?

We already know that titanium oxide in coatings is going to vastly improve UV resistance. And we know that sil/sil coatings preserve fabric integrity over long periods even with Nylon (hello Hilleberg).

But poly + Sil/PE or Sil/PU or PU or PE/PU – we already know these fabrics degrade rapidly in sunlight. Big Agnes: hi there! FYI Some of your tent flies don’t really last very long in the bright CO sun…

There are fundamentals here we can’t ignore.

There is basic hard chemistry, and there is unrestricted marketing spin.
You choose.

Cheers

The real world tests run by Xavier Nitsch of Tipik Tentes (thread in French but includes posts with graphs that are easily understandable for non-French speakers) seem to show that coatings matter more than the substrate — which is exactly what Ryan is saying above. Anything coated with pure silicone lasted longer (better HH and tear resistance over time) in Xavier’s tests than anything coated with some variation of PU.

Personally, I’d like to know more about the environmental footprint of various coatings. Hilleberg discontinued use of 10D fabric (introduced for one year on the Enan tent when it was first released; see the section “Kerlon 600” in the archived link) because the coating didn’t conform to EU standards and the eco replacement was too difficult to work with at a mass production level.

Similarly, it would be nice to know how the environmental footprint of coated polyesters and nylons compares to that of DCF.

Where does that leave us?

Coatings.

And deniers. Until recently, lightweight polyester fabrics were made with higher denier threads than light(er)weight nylon. A higher-denier thread, with higher diameter, will expose less of the thread-interior fibers to UV. So higher-denier fabrics should last longer in direct sunlight.

Much like Nick’s 1980s Chouinard Pyramid. Or 30D polyester rainflies versus 15D or even 7D nylon. Or almost any much-high-denier (and tougher) backpack fabric exposed to sunlight all day, versus tents exposed to far less.

Actual testing of same-denier, same-coating fabrics in high-altitude sunlight might prove, ummm, enlightening.

— Rex

Quickly reviewed the French threads — Safari auto-translation helps a lot. Looks like denier doesn’t make as much difference as coatings. Would still like to see similar tests at higher elevations / much higher UV exposure.

Also mentioned in that thread (and other sources): fabrics and coatings change without notice. That XYZ brand 20D silpoly might test great this year, terrible next year. Much like too many other lightweight backpacking products.

— Rex

I don’t know if the coatings are exactly the same, but Xavier’s tests do include a 40D silnylon and a 40D silpoly. So at least the denier is the same and the coatings are comparable, if not exactly the same.

This post here has two graphs, one for tear resistance, the other for water resistance, with results at new/1month/2months/4months. You can see that the silpoly retains a higher HH rating after 4 months than the silnylon, which experienced a dramatic loss of HH after 1 month of constant exposure. In fact, all of the silpolys tested showed better performance over time than all of the silnylons. Another thing that surprised me is that the lower denier fabrics in the 15D and 20D range tended to end up with better HH ratings than their higher denier counterparts.

Looks to me like the substrate plays a role in the performance of the coating across time. Both denier and material seem to make a difference in the durability of similar coatings.

Sliced and rearranged the tear strength graph to focus on substrate versus denier:

Clear as mud. Must be other confounding factors.

And how does tear strength increase slightly over time in three different fabrics?

My brain hurts.

— Rex

At least part of the graph makes some sense:

No surprise, higher denier is tougher and ages better, other apparent factors being equal.

— Rex

But when you look at water column resistance (HH) the result is totally different
The endurance of lower denier fabrics is better over time.
The arrows point to results for silpoly 15D, 20D, and 40D at 4 months of exposure. The HH of 40D is lowest of the three at that point despite having started higher than the other two.

I’m going to take a wild stab and guess that HH is a reflection of the interaction between coating exposure to UV and denier while tear strength is a reflection of the interaction between fabric substrate and UV.

One of the things that is a bit confusing about the results of Xavier’s tests is the fact that all of the fabrics listed as “silpoly” were sourced I believe from Ripstop by the Roll. The coating that RBTR uses on those fabrics isn’t pure sil but is mixed with PU in a special sauce that is a house secret.

Anecdotally, the Taiwanese 30D silpoly sold by Extrem Textil is coated with two layers of silicone on both sides without any PU mixed in. The hand of that fabric is noticeably different from the silpolys sold by RBTR and it is, IMHO, definitely superior. Would be interesting to know how a pure sil/sil coated silpoly fares in a similar test to the one that Xavier did with the silpolys from RBTR.

Finally, a correction. In post #3673723 of this thread, I mentioned that I thought that the silnylons sold by Extrem Textil might be the same as those used by Hilleberg. While I do not have any privy information this is surely incorrect, as the silnylons ET sells are sourced from Taiwan while the ones used by Hilleberg are, according to Chinese sources, sourced from Korea.

Two important things to remember about HH :

The leakage happens BETWEEN the threads: the larger the threads, the larger the gaps which have to be bridged by the coating. If you put the same thickness of coating on a 40D fabric as on a 15D fabric, the bridging across the larger gaps will be so much weaker. We have known about this for decades.

The gaps between large ripstop threads are where the leakage always occurs first. That figures of course from the previous point. I have many photos of HH testing which show lines of droplets running along the ripstop threads. The presence of any ‘ripstop’ feature is seriously negative for the long-term HH.

A further point worth considering: with a flexible silnylon coating the load is distributed across many threads. Having any large ripstop threads contributes nothing (as in zero) to the tear strength. They are there just for the marketing spin.

Cheers

Long-time tent designer Mike Cecot-Scherer had a lot to say about tent fabrics, including comments on tear strength and hydraulic head in this BPL interview: https://backpackinglight.com/standards-watch-mike-cecot-scherer-on-tent-design/

— Rex