DCF Shelter failure during a hailstorm in Alaska – Skurka video

[Dan]

Is your tent DCF, sil nylon or sil poly?  Any harm to the tent?

I was in a nylon tent and there was no damage. At the moment I was kind of wishing I was in my Plexamid so I could report back to the forum, but it won’t fit me with two dogs, and I’ve been indecisive about buying another 2P tent. So this summer I’ve gone back to using an old Nemo Hornet 2P.

[John S.]

https://www.startribune.com/the-hunt-for-big-hail/600204160/

That title is on several news sites over last day or so, all written  by same journalist.

[Jerry Adams]

I wonder if a pyramid tent would be better in hail because of steeper sides

[Sam Farrington]

“I wonder if a pyramid tent would be better in hail because of steeper sides.”

Several posts say yes, and it sounds logical.  However, the steeper walls of a mid (or an A-frame for that matter) also encroach more on the space inside.  That can be addressed by a larger mid; but that, along with the height, increase the fabric area and add considerable weight.  Seems a lot to carry for the rare hail storm.  And the OP states in the first post that “reports” were that those with Skurka had no hail damage if their tents were of woven fabric, like silnylon or silpoly.  So on balance, I think the advantage is with the silpoly, so long as there is at least some slope on the walls.  Some of the domes that are almost horizontal up top, in the name of maximizing inside space, may be more vulnerable not just to hail, but also to wear and tear from pounding rain in windstorms.

My home is normally immune to storms; but every year or two, we get storms with microbursts, or pounding rain reinforced by severe winds, and there is some leakage.  So some recaulking around the windows is on the to-do list.  An old nylon tent that I carried for years, also eventually started to leak up top in an all night pounding rain storm, despite recent resealing, and had to be replaced.

[Philip Tschersich]

“When you think about it, it’s honestly kind of weird that hailstones haven’t killed all of us already. I mean, they’re chunks of ice that plunge from the sky!

“Hailstones fall from really high up. There’s a popular myth that a penny dropped from the Empire State Building can kill you. The myth isn’t true, but for anyone who believes it, hailstones should be terrifying—after all, they often fall from the height of ten Empire State Buildings.”

XKCD- Hailstones

[Dan @ Durston Gear]

“I wonder if a pyramid tent would be better in hail because of steeper sides”

Pyramid tents do avoid flat roof panels but still often don’t have that steep of sides. They tend to have a fairly large base and then only one pole near the center, so you tend to have somewhat shallow slopes on some sides.

For example, a typical mid for 1P or 2P has a length around 110″ and a pole around 50″, so you’ve got a slope of 42 degrees. That’s a lot better than a 10-20 degree roof panel but not going to be as good for hail (or snow) as what a dual pole tent can do. When you have two poles you have steeper panels if they are spread out along the long axis of the tent (e.g. Beta Light, X-Mid). Two poles won’t help if they are positioned perpendicular to the long axis (e.g. Duplex), and they can be worse if there are end struts to flatten these panels further (e.g. Dipole).

[Piney]

Someone from the Skurka trip posted a detailed write up and analysis of this incident over on Reddit. Their shelter had the worst failure of the group:

 

DCF vs. Hail: an involuntary case study from Ultralight

[Bruce Tolley]

Very interesting! Thanks for sharing. Nothing beats getting first-hand information.

[DWR D]

He seems to conclude that the older type mylar DCF was the main problem. But I also note that his was the oldest DCF tent by a few years. I would think that the added solar/uv exposure over those extra years was at least part of the problem.

[Todd T]

Previous-generation material, age of material, and sun exposure are all plausible explanations, but with N=1, it’s impossible to say anything with confidence.  Was his tent was made with a bad roll of DCF?  Did he stuff instead of fold for those 7 years?  Had he racked on his tent fabric along the bias at some point?  Etc.

The good news is a bit more certain:  how well the sil{nylon|poly} tents did and how almost well the rest of the DCF tents did.

[Tyler P]

That Reddit post, and the shelter, are mine.  I wish someone had told me about this BPL thread at the time, because then I could have participated.  Late the game, but still happy to answer any questions anyone might have.

To recent questions and observations:

• I always roll and use an oversized stuff sack to pack my shelter.
• I’m a hike to dark, start first light kind of person when I’m hiking alone — so even though the shelter had ~70 nights of use, it would have a relatively low amount of UV exposure.
• It’s possible I racked on the tent at some point, but I never noticed any DCF deformation before this trip.

I still think it’s possible my shelter was made with a bad batch of cuben. Especially since one of the other Duplexes on that trip (that received two very small holes) had been on a full AT-thru the season before.  That tent would have had more pitches, more UV, and more packing/unpacking than mine.

[Aubrey W. Bogard]

Tyler,

Thanks for sharing these details. I believe that it adds significant context and puts my mind much more at ease about DCF for shelters.

[Brad Rogers]

<p>Thanks Tyler for sharing your details.</p><p>First off let me say, I’m glad you’re OK.  It’s an awesome epic story and video now, but I’m sure it wasn’t fun at the time and could have had a different outcome.   I’ve used a DCF Shelter (Duomid) in Brooks Range and got both rain and snow, but no hail.  I’ve had some small hail, but nothing 1″ size.</p><p>Currently I’m using a Sil-Poly shelter (X-Mid 1P v1) and though I’ve been using it several years, I’ve never really had it out in an epic storm, so it’s interesting to hear how different shelter types hold up in epic weather as it something that can be hit or miss on testing out – and pretty scary when you do get to do a “test”.  </p>

[Sam Farrington]

“All 5 of the DCF shelters had punctures, in the following amounts: 1, 2, 2, 8, 36. Mine had 36.”

“All 5 DCF tents used 0.51 oz/sqyd.”

So the median # is  2 punctures.  That is two too many for me if their is a better alternative.  One is heavier but stronger DCF.  Another is the lightest durable mini ripstop silpoly like the one Yama uses.  The weight difference between the two alternatives is around a quarter ounce per square yard.  Given the other issues with DCF reported on BPL, I will choose the latter silpoly.  If silpoly equivalent to the Yama is found, as is hoped, will post the news, and will make a new thread, even though I have to tend the dam things.

 

[Tyler P]

After reviewing some photos of the trip, I realize there were no Silpoly shelters in our group — the shelter that I thought was a Lunar Solo is actually a Gatewood Cape.

So the non-DCF shelters, all silnylon, were:

• Gatewood Cape (15D)
• 2x MLD Mids (brown, so I think they’re 30D?)
• Tarptent Notch (30D)

Wish I’d caught that detail sooner, sorry folks.

[DWR D]

Another thing comes to mind that might affect the DCF fabric over time:

Leaving it in a hot car for hours or even days at a time.

[Sam Farrington]

Tyler,  I don’t think the immunity to severe hail depends on whether the fabric was silpoly or silnylon.  Both are woven fabrics with some elasticity on the bias, and the silcoats are also elastic.  Neither of which can be said of DCF.

 

[Tyler P]

Sam, I was simply submitting a correction regarding the facts of the event.

[Eric Blumensaadt]

“DWR D”, I too have a TT Notch Li and I hope if I ever camp in a hail storm mine also holds up well.

I dunno if maybe a DCF tent in a “slack” pitch would help v.s. a taut pitch in a hail storm.

[Roger Caffin]

maybe a DCF tent in a “slack” pitch would help v.s. a taut pitch in a hail storm.
Somehow, I doubt it – speaking now as a physicist.
The distortion created in elastic nylon fabric by the impact of bit of hail or a glass marble is going to be very localised. I doubt the distortion would extend beyond a radius of 3 times the radius of the ball. The same would apply (I think) to Mylar and DCF. Even if it goes a bit further, I really don’t think having a slack pitch would affect the results much at all.

The elastic nylon does absorb all the energy from the ball by stretching, and the stretch means the peak force is limited. With a non-stretch fabric the peak force would be much (much) higher, beyond the burst strength of the Mylar in some cases (as the photos have shown).

By way of comparison, think of what happens when you compare a nylon tow strap with a length of chain for towing. You won’t snap the chain, but you might damage the towed vehicle with a chain.

Cheers

[Sam Farrington]

“All 4 of the Sil shelters (3 nylon, 1 poly) were unscathed.
All 5 of the DCF shelters had punctures, in the following amounts: 1, 2, 2, 8, 36. Mine had 36.
All 5 DCF tents used 0.51 oz/sqyd.
2 of the tents were the identical make and model as mine (1 and 2 punctures each).
All DCF shelters were 2-3 years old, except mine which was 7 years old.”
(From Tyler P’s reddit post, guoted in Piney’s post above)

Hope I’ve got the attributions correct. It appears there were no silpoly shelters involved, and we can only speculate that silpoly would have fared as well as silnylon, on the theory that both fabrics are elastic; that is, they will stretch to protect from damaging force, but will also return to their original shape once that force is withdrawn. Moreover, that theory would apply to a slightly heavier DCF, because while stronger, is just as inelastic.

Looking at my collection of silnylon, silpoly, DCF and Cuben fabrics, I’ve noted that none of them is particularly elastic running parallel to the grain; but the silpoly and silnylon are much more elastic running diagonal to the grain, a/k/a on the bias. So it appears that it is the bias stretch that gives the woven fabrics their elasticity against punctures, so long as an inelastic coating is not applied. And it is likely that the interweaving of the fibers in the sil coated fabrics is what makes them elastic on the bias.

That is why my first assault on DCF was to open it up and see if the dyneema threads were interwoven. Possibly they might have been, but they were not. So I don’t think it involves ‘rocket science’ to see that a thin material with next to no bias stretch will be far more susceptible to puncture than a thin material with bias elasticity and the ability to absorb puncturing force.

Please take a look at some DCF tent fabric and see how elastic it is on the bias compared with silpoly or silnylon tent fabric, and be your own judge.

Apropos pitching the shelter with slack, and more diagonal to the ground; please consider the side-effects. Given severe weather, the slack will make it very uncomfortable in the tent, and the slim pyramid or A-shape will present a better target to the wind, and would have to be heavier to provide the space needed to be comfortable inside. A fairly rigid and aerodynamic shape would be better.

[Roger Caffin]

A fairly rigid and aerodynamic shape would be better.
Just so.
And it would not flutter: a damaging condition which abrades fabric, weakens attachment points, and pulls out stakes.

Cheers

[Murali C]

I never put up my tent to take shelter from a passing thunderstorm during the day. I just wear my rain clothes and keep hiking even if it is hailing. If the hail is really big, then I suppose I could get into the lightning position and use my backpack to protect me from the hail if there are no trees or big rocks around. So that would be my recommendation….don’t put up your tent.

I feel, reducing the slack of the DCF tent will help as it could provide a trampoline effect or elasticity instead of a flat rigid, taut inelastic surface.

Regarding difference between 0.5 and 0.8 – doesn’t 0.8 have more dyneema threads? Will the increased dyneema threads not reduce the probabiility that the hail is hitting a spot where there is no thread and hence make a hole? Its like the egg carton with eggs where you can stand on it and not break any eggs. But, if the distance between the eggs increase and you stand on the egg carton, you will most likely break the eggs. I think of the dyneema threads as a lattice work – a denser lattice will be able to support the mylar much better than sparser lattice. Anyway, I am no expert – just my intuitive reasoning of the problem. I may be totally wrong:-)

[Sam Farrington]

Murali C,

The lattice work image is OK, but the strips have to be fastened to each other at every point where the strips cross; otherwise, you get just a bundle of loose sticks.  Will take another look at the dyneema threads with the mylar removed to see how uniformly the threads are held together and in place by heat, adhesive or whatever.  The verdict from the first tests was ‘not so much.’  If only the threads were woven together like a fabric.

[Author]

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