DCF Shelter failure during a hailstorm in Alaska – Skurka video

[Roger Caffin]

It is worth remembering that DCF was originally meant for spinnakers, where a weight high up in the air is not good for the boat.

But there are many stories in the yachting game about DCF spinnakers ‘blowing out’ – as in bursting and shredding. But if you can afford that sort of yacht and the cost of a DCF spinnaker, then the cost of a replacement might not matter too much to you – except that you probably lost the race as a result.

It is also worth remembering that while DCF may have a fair strength in tension along the film (due to the embedded Spectra fibres), it is nothing more than a couple of layers of Mylar film when hit by hailstones. And it does puncture easily on the ground.

I ONLY use nylon for my extreme weather winter (and summer) tunnel tents.

Cheers

[Kyler B]

They just recorded a softball sized hail stone east of me in Alberta. Hail frequently damages cars, windshields siding and roofs. These types of hail events would destroy probably any type of tent.

I am starting to think that I better develop a better understanding for weather and maybe make a hail emergency plan. Happy that we can learn from other peoples experiences.

[Sam Farrington]

Roger,
Thanks for your insights on this issue. Much appreciated.

[Roger Caffin]

I would have thought that a ‘softball sized hail stone’ could even be injurious or potentially lethal. Small wonder that it might damage hardware.

That said, a metal roof or a glass window are hard unyielding surfaces, and the impact of a hailstone on them is going to be sudden with very high forces. The impact on a stretchy yielding span of nylon fabric might actually let it survive better, by slowly absorbing the energy. A bit like the difference between hitting the concrete and landing on a trampoline.

Hailstones that size – very dangerous. Get under a roof or a large tree.

Cheers

[Maurício Melati]

I just looked on the zpacks website and saw this data:

.55 oz/sqyd DCF: Tensile Strength: 63 lb/in (552 N/5cm) and Puncture Strength: 1.8 lb (8 N)

.66 oz/sqyd DCF: Tensile Strength: 63 lb/in (552 N/5cm) and Puncture Strength: 1.9 lb (8.5 N)

.75 oz/sqyd DCF: Tensile Strength: 104 lb/in (911 N/5cm) and Puncture Strength: 3.1 lb (14 N)

I saw on the internet two cases of hail-damaging tents, both were duplex: 0.55 and 0.66. Skurka did not inform with details which other tents were damaged.

This data shows how 0.74 has better parameters than the other two versions and which could have superior performance against hail. Close to twice as strong compared to tensile strength and considerably stronger in relation to puncture strength.

The thickest material in a duplex is only 55g more. It seems more than prudent to opt for version 0.74 after this discussion. Mainly because the weight difference is quite low

I will love to hear from someone from MLD, Hyperlite or Locus (brands that sell pyramid tents using the thickest DCF) if they have ever received any reports of catastrophic hail failure since they started selling tents in this thicker (0.74 or 0.8 oz/sqyd DCF) material. I mean catastrophic because any small damage to the DCF is easy to repair.

Thanks all for the discussion, I learned a lot.

[Chris R]

Walnut sized hail was enough to put dents across the hood and roof of my Subaru. Shredded all the leaves on our rhubarb too!
Interesting to see that the .66 dcf brings very little benefit.

[Ron Bell / MLD]

We’ve never heard any reports of our .75 mids getting hail damage tears.  In the past we were always very careful to only market the .55 and .67 as 3 season below treeline only and no warranty. This year we totally dropped all the lighter DCF versions but the .75.  It can stay out of the landfill about 3 times longer and the weight difference in a 1P mid is about the same as one fig bar snack.

[Jeff McWilliams]

I’m pretty surprised that TarpTent only offers .55, seeing as how they were traditionally skeptical of DCF durability.  Reports such as these would definitely have me avoiding the lighter stuff.

[Henry Shires / Tarptent]

FWIW, we’ve never received a report of hail damage to the 0.55 Dyneema.  I don’t know the odds but I have to think the odds of really severe, damaging hail in any given location are relatively low and much would depend on site location, wind speed etc.  Silnylon is without a doubt inherently more resistant to point forces.  Silpoly isn’t as good as silnylon that way but still better than Dyneema given its ability to stress along the bias.

-H

(Tarptent)

[Dan]

I don’t know the odds but I have to think the odds of really severe, damaging hail in any given location are relatively low and much would depend on site location, wind speed etc.

Just one more example of balancing weight against the risk of a rare event.

Some people read about this event and say that they’re going to stay away from 0.55 DCF or from DCF altogether, but I suspect that many of those people were already amongst the DCF skeptics who are always posting that they don’t mind carrying the extra weight of sil-nylon because it’s cheaper or stronger, or more proven, etc.

For those of us who have had good first-hand experiences with DCF, even in severe weather  … it’s an unlikely event that won’t change our choice.

[Roger Caffin]

Puncture Strength: 1.8 lb (8 N)
Blimey! That is LOW!

Cheers

[DWR D]

Puncture Strength 1.8 lb…

not sure that says anything… 1.8 lb applied to what??? a needle? a one foot square of plywood? a finger tip? a one inch square?

 

 

[Peter C]

Why choose a .55 dcf over a .74 dcf when you have DOUBLE the Puncture Strength? If we talk about added weight of a .55 dcf to a .74, it barely gets to 11% (56g added on a duplex .74 over a .55, like Maurício mentioned above). Is it worth choosing a less reliable material EVEN if a hail event is “rare”? I mean, isn’t that the point in the first place? an airbag should only works once to prove its value.

Some people seems to treat this hail thing like something simply manageble, but if instead a group to help you squeeze in others tent,  you were completely alone, miles away from civilization… that could be a life or death situation.

Those arguments stated by tent manufactures like “we’ve never received a report of hail damage to the 0.55 Dyneema”  adds zero relevant information to this discussion, what is the point? just because you don’t have a “report” of the event, doesn’t mean it doesn’t happen….

or others saying “I don’t think .74 dcf is a full solution” than what is? . 55 definetely is NOT.

 

[Murali C]

Roger – what is the puncture strength of Silnylon 20d, 30d and silpoly 20d – would you know? just curious.

Dan, if I were to buy a new DCF shelter now, I would definitely opt for 0.75 and use mitigation strategies like loosening the guylines etc in a hailstorm. I have been primarily using DCF for the last 6 seasons. – 0.51 osy. I don’t know about using it without a care – I think it will always be in the back of my mind.

 

[Roger Caffin]

Hi Murali

As I don’t know how the mfr measures ‘puncture strength’, or even how they define it, I can not help you with this.

On the other hand, looking at the physics/engineering of DCF and (say) silnylon fabrics, I can say with great confidence that the silnylon will be stronger.

For further information on ‘puncture strength’ in general you could consult testing standards such as ASTM D751, ASTM D3787, and ASTM D4833. They often specify the diameter of the puncture probe that applies force to the specimen being tested. Puncture fixtures are offered with sharp puncture probes with small diameters (think thorns on the ground) as well as with large diameters for ball burst testing. I would think the large balls version would be appropriate here, with hail.

Cheers

[jscott]

People in the back country ahve been mauled by bears. Or hit by lightning. etc. I’ve read about far more instances of these than of hail damaging a dcf tent, or any tent really. Maybe it’s because bears and lightning are more dramatic. But, again, I don’t ever recall hearing about this on this forum. Of course in exposed conditions, hail would be more damaging. Usually if one sees weather coming in, you look for shelter from trees or such. Sometimes that’s not possible.

But, yeah, what are the odds of this happening? I really don’t know. Better or worse than a bear mauling? etc.

[Matthew / BPL]

Those arguments stated by tent manufactures like “we’ve never received a report of hail damage to the 0.55 Dyneema”  adds zero relevant information to this discussion, what is the point? just because you don’t have a “report” of the event, doesn’t mean it doesn’t happen….

I get your point here that just because Henry doesn’t have a report of a specific type of event doesn’t mean it didn’t happen. That said, Henry has sold a considerable number of DCF tents (several thousand DCF tents) which gives him a large data set to pull from. My perception is that Henry is known for having reasonable judgment and I can’t think of any situations where he has made wild or outlandish claims. His opinion means something to me.

My $.02

[Dan]

Is it worth choosing a less reliable material EVEN if a hail event is “rare”?

Reliable is a loaded word, every material has its specifications. However, even if I accept the premise, for me the answer would be “yes”. For you … apparently “no”. Which is fine. Let’s accept the fact that other people may make different choices, and those choices might be right for them. IMO, there is way too much “my way is the right way” attitude on BPL.

This is representative of every gear choice we make, no different. I will make my own choices based on my own risk tolerance, my understanding of the conditions that I encounter, my assessment of my ability to improvise (and tolerate) solutions and/or alternatives. I would not presume to make a universal statement about what everyone else should do.

We are almost always trading off weight against reliability. I could collect rare failure stories of virtually every part of every piece of gear, and use the above-quoted argument to convince myself to upgrade everything to heavier and more reliable gear. The forum is replete with failure stories. The pole failed, the burner failed, the filter failed, the strap failed, etc.

Every piece of gear that I choose to use has a more reliable and heavier option that I could have chosen. And I also choose to omit back-up gear from my pack if the chances of needing it are sufficiently low. I think that we all do this at some level. I’m trying to avoid the “pack your fears” cliche, but it seems to apply.

[jscott]

“I get your point here that just because Henry doesn’t have a report of a specific type of event doesn’t mean it didn’t happen.”

I’m thinking Henry WOULD hear from someone whose tent was shredded in a hail storm. They would be angry. We live in a world where we let our feelings known, and demand payback and satisfaction. He says that it hasn’t happened. I believe him.

I’m still waiting to hear from someone that HAS had their tent shredded in hail. I literally don’t know if it’s far more common that I might guess. So far, nada.

[Matthew / BPL]

Well said, Dan.

This thread has made me reconsider my choice to camp in exposed spots above treeline in the past. Like so many other discussions here I’m reminded that it is technique, judgement, and experience that is more important that gear.

I think that is what RJ was getting at a couple pages back when he mentioned that even fragile Polycryo tarps have an appropriate use.

[Murali C]

C’mon guys – there is enough evidence that 0.5 osy tents get shredded by hail. Of course it depends on the size of hail and sure it is a rare event. There is nothing unique in the construction of Tarptent’s DCF offering that will make it immune to hail. Or when Dan Durston says his tents have steeper sides and so perhaps his 0.5 osy tents will fare better against hail. The only reason Henry/Dan may not have heard is because there are lots more Zpacks DCF tents out there than theirs at this point. I am sure we will hear about failures in their 0.5 offerings in coming years.

And yes, 0.5 DCF tents do survive many times from what we have heard as well. But to deny that 0.5 is not susceptible to hail is being in denial.

Given certain sizes of hail, I am sure 0.75 will also suffer similar fates. Though I hope Ron is right and perhaps 0.75 is the answer. Who knows! It will be nice to do some surveys or hear about instances where 0.5 got shredded and nothing happened to 0.75.

If a pole breaks, you can always get a stick. If your filter breaks, you can always not filter for a few days till you can get it fixed. If your burner fails, you can cold soak. You are not going to die.

But, a shelter getting ripped in hail, however rare it is, can be dicey especially if your sleeping bag gets wet because of that.

You cannot control bear attacks or lightning or hail. But you try to control what you can control. And tent/backpack etc is something you can control.

Going lightweight is not taking unnecessary/unneeded risks, but still being safe while being lightweight.

“We are almost always trading off weight against reliability”

I disagree with this statement. I don’t think I have ever told myself that it is okay to take something that is unreliable because it is lightweight. I take Steripen because I have heard way too many stories about Sawyer filters freezing etc. And I take backup medicines in case Steripen fails. I have used Pocket tarp with a tall bathtub because I know I will be extremely dry – without a tall bathtub – that is taking unnecessary risk in my book. But, if you can make it work – all the power to you. Hike your own hike. I take frameless backpacks because they are very reliable and lightweight.

I bought DCF tents because, yes, it is lighter. Ignorant of the fact that 0.5 can get shredded by hail. If there was any question of its reliability, however rare the event is, then I would have probably bought the 0.75 shelter. In fact after hearing this, I am not going to buy Tarptent offerings because they are only availanble in 0.5. If I buy one more from Zpacks, it will be 0.75.

[Roger Caffin]

We are almost always trading off weight against reliability
Errr – no.
I won’t do that.
But I will take some effort to make my UL gear reliable: that is very different.

Cheers

[Dan @ Durston Gear]

Good discussion. Lots of passion here for sure :)

I think weight and durability are a tradeoff – almost everything is. You can always make a tent stronger and thus more resistant to extreme scenarios with heavier materials, but at some point you have to ground that in the real world and decide how strong is good enough because no one wants to backpack with a 10 lbs 4-season tent.

So yeah you can say “0.8 oz is more resistant to large hail and only a little heavier” but why not take that a step further and say “1.0 oz silpoly is much better yet and again only a little heavier” or “1.3oz silnylon is even better and again only a little heavier” – the weight creep never ends if you don’t ground these choices in some basis for how good is good enough – which is always going to be a compromise. For some conditions 0.5oz is good enough, for other conditions only a 1.9oz 70D woven is good enough.

I don’t think there is a good argument that 0.8oz is some great solution to hail when the puncture specs really aren’t that different than 0.5oz (only about 1.5x) and a woven is way better. If 0.5oz gets shredded, having only 1.5x on that puncture strength spec is dicey. If you’re serious about wanting resistance to severe hail, you need a woven fabric with stretch. But rather than flee to woven fabrics for all uses, we should keep in mind that these hail damage incidents are super rare. There’s a ton of reports of 0.5oz shelters surviving hail and maybe 3-4 reports ever of serious damage over the last decade. Most hail doesn’t damage DCF but severe hail can.

I’m in the 0.5oz DCF camp because it’s the only variant of DCF that actually saves meaningful weight over a woven fabric. If you go to 0.8oz you’ve given up the majority of the weight savings compared to a 1.0oz woven, so why not accept a little more weight to get even more protection against hail with a 1.0oz woven while saving hundreds of dollars?

Aside from hail, I also see minimal evidence that 0.8oz lasts meaningfully longer. The main ways that DCF eventually fails are delamination, pinholes, and abrasion – which are highly similar for 0.5oz and 0.8oz because they use the exact same mylar and adhesives. These failure methods are partly related to weaknesses inherent in DCF, but moreso are the result of how some of the most popular DCF shelters are constructed (some of the most popular DCF tents have major forces acting diagonally on the fabric without reinforcement, which deforms the material and leads to early failure). With thoughtful design against deformation like you see on most brands of DCF tents, the material can last a lot longer than one thru hike and longer than almost everyone will ever hike.

So I think 0.5oz is a great material for the vast majority of people, and then if you need something closer to a 4 season shelter then I’d look at wovens. I originally preferred 0.8oz but over the last decade I no longer see a big role for 0.8oz because it does give up most of the weight savings for only small improvements in the things that matter.

[Sam Farrington]

Quite a ride through the valley of risk assessment, which from what I’ve read, is a very debatable science.  And there are other considerations besides hail damage.

Recall Ryan J’s post not long after Cuben became in use for tents.  His photo showed seams with threads that had become very loose.  Most likely because neither the fragile mylar, nor the unwoven Dyneems fibers could hold the threads tightly in place.  So now we hear that some use adhesive without sewn seams.  But also that the adhesives fail below certain temperatures, and lately the effects of heat have been raised as a concern.  Which is good because the climate is getting warmer with no end in sight.

A problem with DCF is that the mylar on each side of the laminate is very thin and fragile, much more so than common kitchen materials like saran wrap.  The mylar can be easily torn.  But with the addition of Dyneema threads in the laminate, tents are manufactured.

Experimenting with adhesives applied to strips of DCF for the purpose of testing adhesion, I found that when the best 3M adhesives were used, DCF  strips could be torn apart and shredded without a great deal of effort.  But with ~half ounce DCF the material tore apart in many places along what would be the warp (parallel to the sides of the roll) if it were woven.  With ~3/4 oz DCF, there was less tearing, but the Dyneema threads separated along the warp because the weft threads were not secure.  They were just laid in place, but not woven with the warp threads, nor sufficiently held in place by adhesive.  So the fragile mylar simply split apart when the warp threads separated because the weft threads were not holding them in place.  On a tent, this would appear as splits parallel to the warp.  However, if the warp and weft threads had been woven together in the laminate, this would not have so easily occurred.

DCF also has no bias stretch, so that when pulled diagonally across the warp and weft, there is no elasticity as there would be with a woven fabric.  This makes it very difficult to get a tight canopy that will better resist severe winds.

In short, the concerns were:
– fragility of the mylar
– adhesive seams that would fail in excessive heat or cold
– absence of a weave between the warp and weft threads
– lack of bias stretch in the material

There are other concerns like the bulkiness of the laminate and additional pack volume needed for carrying.  However these concerns do not relate to failure of a shelter, although they are a PITA for someone who values a compact pack that will keep a pack’s center of gravity close to the body. This is important to me to avoid excessive stress and long term damage to the spine; however, from the bulk and size of their packs, many backpackers do not appear concerned on this score.

As several on this thread have recognized, the most important concern is a viable shelter that will protect the user from unpredictable weather events, only one of which is hailstorms.  We have also been treated to unexpected weather that brings severe cold, rain and wind, the most recent such event this summer in the NH White  Mountains having resulted in one death, and a number of hospitalizations for hypothermia.  Hardly a day goes by here without a search and rescue.  What would happen for these folks in a large and less accessible wilderness area in the Rockies is something I don’t like to think about.  A lifetime of hiking has shown me that such events can be reduced in number by prudence, but are also unavoidable at some point, particularly on longer wilderness treks.  At such times a tent that will withstand the elements is our ace in the hole.

While it is certainly a pain to carry a slightly heavier shelter that would not be needed under most circumstances, I won’t hesitate to do so.  When Dyneema or the like is woven into a fabric, well waterproofed, with substantial weight savings, I would pay for it. But not till then.

[Dan]

We are almost always trading off weight against reliability
Errr – no.
I won’t do that.
But I will take some effort to make my UL gear reliable: that is very different.

 

I disagree with this statement. I don’t think I have ever told myself that it is okay to take something that is unreliable because it is lightweight.

Perhaps “reliability” wasn’t the best word, but I was trying to respond to the previous post by using the same language they used. If you look back at my post, I tried to make this clear. In any case, I’m surprised that the two of you didn’t get my point, or perhaps you are both choosing to take a Straw Man approach in arguing your point. Nobody is proposing to use gear that is inherently “unreliable”. I think it’s clear that we are talking about inevitable compromises that come with weight, and that this is not a black-and-white question. It’s a question of what is good enough for the conditions, skill level, etc.

To invent some arbitrary numbers (just to make a point), ulralightweight gear may be appropriate for the conditions 99.9% of the time. Using heavier gear may increase that to 99.99%. What failure rate are you looking for? In some sense, this can be construed as reliability-weight tradeoff, or durability-weight tradeoff, or choose a different word if you prefer. As I mentioned in my previous post, we are talking about the specifications of materials, and by choosing lighter weight materials (DCF, carbon fiber, etc.), we are usually making a compromise. This is how engineering works in the real world; cost is also a factor, obviously.

I only need to get through my lifetime without having my tent punctured by hail, I don’t need to get through 10 lifetimes. And despite this recent report that has a few people riled up about DCF (and long-time skeptics re-emerging, which is fine), other first-hand reports of such events appear to be virtually non-existent. And even if I get some holes, I trust that I can figure out how to get through the night, in the same way that I have managed other gear failures in the past. YMMV, HYOH, etc.

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