How did your DCF shelter age (and expire)?

[Monte Masterson]

You’re right John, for weather conditions most people face silpoly will hold up, however Trekkertent has the 40D silnylon option that many Scotts choose and for good reason. Scottish winds are legendary. But I only had to experience disaster once with 50 mph plus winds at the brunt of a thunderstorm to appreciate more durable materials. But if weather predictions for trips less than a week don’t include volatile hot and cold air masses colliding I often just pack a 7D tarp.

I’m going to put the silpoly tarp I just made to rigorous testing this Winter. It’s constructed with Dutchware Xenon Sil Wide and the material comes in at 1.18 oz per square yard on my scale. With sleveage removed it’s 70″ wide. Dutch is very high on the material and swears it has an HH of at least 4000. I wouldn’t mind seeing other independent tests to corroborate that though. It’s a little expensive at $11 per yard. I bonded same material reinforcements on for each tieout. I believe this is the same silpoly Borahgear uses on their solo tarps. And correct me if I’m wrong, but I don’t think the Borahgear tarps have bonded reinforcements. At $67 I don’t see how they could with all of the extra time and labor properly bonding reinforcements involves. I could be wrong so if I am please correct me. Nevertheless, I’m convinced that reinforcements greatly increases the durability in strong winds.

I hope my reservations about 20D silpoly are wrong and it’s stronger than I think. It sure would be nice because it certainly does hold less water than silnylon and has less stretch. I don’t like the feel of silpoy when working with it as much though. I know many will say they find it easier to sew than silnylon because of its lower stretch, but I don’t. And when I shake a piece of the silpoly hard it has a very brittle sound to it. Seems stiffer and not as supple. As has been mentioned in other threads, a little stretch in strong winds might be a good thing. Anyway, we always get very windy days during the Winter in Southern Indiana so I’ll see what the field testing bears out. I’m not a materials expert, but I figure challenging real world conditions are the best way to evaluate.

[Sam Farrington]

Dan, Thank you for the additional info.  I remember Richard Nisley’s ‘dirty little secret” thread, and the low HH he found testing Cuben; so it is good to hear about some improvements.  I see that both Dutchware and Ripstop by the Role currently have shortages with DCF.  As was suggested in earlier posts, this may create a fait accompli for MYOG, along with delays and still higher prices for DCF tents and tarps.

John and Monte;  Earlier this year Stephen Seeber was kind enough to test samples I provided of new 20D silpoly from both Dutchware and RBTR, both in lighter shades of green or tan.  The weight on my scale of the Dutchware was 1.18 oz/yd2 (osy), as Monte notes, and 1.24 osy for the RBTR, both purchased earlier this year.

The RBTR tested out at 3515 mm HH as received, and 1476 HH mm after simulated aging.  The Dutchware tested out at 1335mm as received, and 1265 after aging, but sprung leaks at lower pressures at some points on the large sample.  Please note that Stephen has tested a number of fabrics at my request, but I’m not sure about whether he has time to continue to do so.  I sent a copy of a photo of of Stephen’s latest set up for testing HH to Roger Caffin, and gathered that Roger was impressed.  Stephen has put a lot of his time and personal resources into perfecting his testing, and I’m comfortable with the accuracy of the results.  We are fortunate to have someone who has been willing to perform this service at no charge; but that could well change.

Of course there are other issues with testing; such as puncture, tear and abrasion resistance.  I see that Extrem Textil in Germany has specified test results for some of these issues, while the American companies generally have not.  So I think we are left to our own devices.  It is sometimes taken for granted that a given fabric will have consistent performance; but I have found that changes made by the manufacturers and the degree of quality control also affect test results.  So a new roll of fabric may not perform as well as an old one.

All this relates to the subject of this thread affecting choices of fabric used for ultralight tents and tarps.  My take from this thread and Stephen’s tests is that 0.67 osy is desirable for DCF, and RBTR’s 1.24 osy ripstop is desirable for silpoly.  That is a difference of 0.57 osy.  With or without an inner wall, my designs for a 1.5 person tent (self + dog(s) + gear + cooking space) run around 10 sq. yards of fabric, not counting netting and a < one oz DWR inner ceiling fabric from Extrem Textil.  That comes out to around a 5.7 oz weight penalty for using silpoly instead of the DCF.

A tapered A-frame as discussed on this thread would greatly reduce the yardage, but would not be anything I would like to be stuck in after hiking in the rain much of the day and having to cook and eat in the shelter with a storm continuing into much if not all of the night.

But we don’t have a lot of experience yet with silpoly, as we do with silnylon.  And a ~5.7 oz weight penalty may be acceptable to some, but not to others.  A 2-3P shelter would of course present a higher weight penalty.

So I’ve been thinking again about 10-15 denier nylon, and even a < one oz Porcher ripstop paraglider 6.6 nylon that is strong but not highly waterproof, although not being silicone coated, might be reinforced with products such as Gear Aid’s Tent Sure.  It would not be the first time BPL members have resorted to enhancing coatings.  But an order for some of the Porcher from Extrem Textil is now over a month old, so am not sure about whether difficulties remain with shipping to the USA.  There are companies in France that sell the fabric, though.

Sometimes the challenge to come up with an all-purpose backpacking tent seems daunting and even endless, so it’s no surprise that many prefer to order gear that is ready-made.  A big advantage with MYOG is the ability to design to your own needs, and do it well enough to feel both confident and comfortable in the harshest backpacking weather.  Besides, it makes for a very enjoyable hobby that goes hand-in-hand with backpacking.

[Monte Masterson]

Sam, was the Dutchware silpoly you got the Xenon 1.1 or the Xenon Sil Wide because they are as you probably already know 2 different materials? The Wide is supposed to be better.

[Jon Solomon]

Monte,

I share your reservations about 20D silpoly.

After having used shelters made with 20D silpoly extensively over the past two years, I feel more confident in talking about its relative strengths and weaknesses. The two kinds of silpoly with which I have experience are the 20D version from RBTR and the 20D version used in the X-Mid. These are fabrics with different coatings and a noticeably different hand. The former has a coating on both sides that is a mixture of silicone and PU. RBTR don’t provide any information about the ratio of the mix. The fabric is soft, drapes well, and has quite a bit of stretch. Apply force along the bias, it is quite easy to permanently deform the fabric (probably not a relevant real world use case scenario but I don’t know). The fabric used in the X-Mid has silicone on one side and PEU on the other. It is much stiffer. This stiffness did not work well, IMHO, with the first generation X-Mid design, which was difficult to pitch tautly at the base. (Note: Dan Durston claims that this issue will have been resolved by the soon-to-be-released updated design with the addition of cat cut hems). While these fabrics both perform like a champ in the face of high humidity and rain, I haven’t been very impressed with the way they have performed in strong winds. Of course, it is almost impossible to talk about the fabric apart from the design in which it is used but this is not my goal or focus. The 20D silpoly from RBTR has a lot of give to it. I’ve used it in single pole asym mids (Tipik) and single pole Rainbow-type designs (Trekkertent). In a strong wind it is one heckuva floppy fabric. The 20D silpoly used on the X-mid is stiffer because of the PEU coating on one side, but the first generation X-Mid was plagued by major design flaws (lack of load-bearing side tieouts and a base perimeter that was notoriously difficult to pitch taut on uneven ground) that accentuated the inherent unsuitability of that fabric to resist strong winds.

Unfortunately, I can only provide anecdotal evidence, no field measurements, so you’ll inevitably have to take what I say with a grain of salt.

The new 30D silpoly from Extremtextil looks like a different beast entirely. First of all, it has a pure sil coating on each side, with two coats. The hand is much better than either of the two 20D silpoly fabrics I’ve used in the field, both more supple and more robust. Second, based on the numbers given by ET, the tear strength and tensile strength are a huge improvement, comparing well to silnylon, all at a weight lower than some 30D silnylons. This fabric is much more robust than the 20D silpoly and I cannot get it to permanently deform by pulling along the bias as I can easily do with the 20D from RBTR (didn’t have a sample of the X-Mid silpoly to try that with).

I will be field testing over the next year a shelter made in the ET 30D silpoly using an octagonal design. A copy of the now legendary Jumperhome Mountain House 2P by Haitao Li RIP. The weight penalty over a 20D silpoly or silnylon is worth it to me. I think that wind resistance is one of the aspects of UL shelters that has been largely overlooked. Probably it’s not a big deal to a lot of people. But as I get older, I really value quality sleep on the trail. Recent studies show the importance of sleep to brain maintenance and repair, especially more important the more you get older. While many UL shelters I’ve tried can “getcha thru the night,” so to speak, it’s often at the cost of getting a good sleep due to the huge amount of noise caused by panel deflection and other flappiness in strong winds (Zpacks shelters are notorious for this and when I see them I always look for a different campsite; check out that photo recently posted by Ryan of a funky Zpacks pitch). Last summer I used a symmetrical octagon Mountain House 2P in CTE2.08 DCF (410g) for about two weeks in the Pyrenees and was blown away by the stability of the tent in fierce hailstorms. Much much more stable than a rectangular mid under similar conditions. Of course, either would do the job of keeping me “sheltered” but there is just no comparison in terms of a quiet ride. The octagonal design has inherent features that seem to stress DCF more than I’d like, so I decided, after consulting with a more knowledgeable friend, to have made a copy with some improved design updates using the 30D silpoly from ET. A bug-free, noise-free bomb shelter at under 700g may sound heavy to some (me included) but I think it’s a trade off I’m willing to make.

Cheers,
Jon

[obx hiker]

OK that was a really interesting and informative post. Speaking for myself the post and maybe the thread is becoming much more technical and maybe or therefore difficult to follow for the average reader but maybe that’s just a projection on my part. This seems to happen pretty frequently on BPL on various subjects (stoves etc. -wow!)  and really it’s one of the great things about this blog; the detailed, specific and often technical info about gear.

Anyhow the post above sent me down the rabbit hole. The first thing I didn’t really understand and learned was the specific definition of ‘bias’ as it relates to fabric.

“The bias grain of a piece of woven fabric, usually referred to simply as “the bias”, is any grain that falls between the straight and cross grains. When the grain is at 45 degrees to its warp and weft threads it is referred to as “true bias.” Every piece of woven fabric has two biases, perpendicular to each other.”

Dan’s link above describing the fabrics he is working with taught me something about PU and PEU along with silicon coating of fabric. I recommend it again.

Along the way I learned that the Mountain House 2P shelter was made by a fellow named Jumper Home who was tragically killed in an accident in August. Looking at his shelters he must have been a really talented individual who will be missed. I found some photos of that shelter over on the Trek-Lite blog and it is indeed an 8 sided octagonal ‘pyramid’  That one had me confused. Might be better to say an 8-sided shelter supported by a single pole. Octagonal sided single-pole shelter. Ok obviously octagonal ‘pyramid’ is a lot shorter.  Bet Teepee Walter might find it interesting. There’s a reason that form of shelter was the standard mobile shelter for the original experts travelling and living on our western high plains. Big footprint. Lot of material ‘wasted’ in the upper cone part but that might be a potential advantage in designing for venting and condensation issues.

Anyway just maybe presumptuous of me but that’s my translation of some of the info above presented as hopefully helpful to anyone else who knows as little about this stuff as I and is also curious or stubborn enough to have made it this far with this thread.

[obx hiker]

BTW another question. Which bias is more critical with ‘tent’ shelters?

Warp or Weft?

What are the differences between warp and weft fibers?

“Warp” is a series of threads that run from the front to the back, and “weft” is a series of threads that run in a pattern through the warp. Weft is a yarn that runs back and forth whereas a warp is that which run up and down. Continuous yarn is used in weft knitting for forming courses and rows of loops.

[Sam Farrington]

Monte, re: “Sam, was the Dutchware silpoly you got the Xenon 1.1 or the Xenon Sil Wide because they are as you probably already know 2 different materials? The Wide is supposed to be better.”

It was the Xenon 1.1, moss green.  Could you advise the difference between the materials you have in mind.  Thanks.

Jon, re: “Apply force along the bias, it is quite easy to permanently deform the fabric (probably not a relevant real world use case scenario but I don’t know). ”

Yikes, that is awful news.  I think that permanent deformation of a tent wall is likely to create the dreaded flapping, makes it impossible to make a tent wall taut, and makes me wonder about strength.  The whole shtick with silnylon is its elasticity; that is, its ability to snap back into shape and not permanently deform.  Unfortunately, it absorbs moisture and becomes flaccid, losing its elasticity until it dries out.

The 30D silpoly from Extrem Textil does not appear to be that much heavier.  It is spec’d at 1.3275 oz/yd2, not much heavier than 1.24 osy for the RBTR 20D silply. (multiplied by .0295 to convert from metric).

Guess I will have to do some more fabric buying and testing before making any final choices.  The paraglider material I mentioned earlier is interesting because although it is 20 denier, it is lighter, less than an oz/sq/yd.  I bought some from a company in France several years ago, and was impressed with its ability to hold its shape compared to fabrics bought in the US.  It would be ironic if, after all the testing, ripstop nylon with a PU coat becomes the choice.

So besides waterproofness, I think it’s also worth checking out for moisture absorption and elasticity.  It is easy enough to do that with the plastic embroidery rings I’ve mentioned before, and the weather here is just right for that now (wet).  The rings can be used to check for permanent deformation by placing a weight in the center of the ring a while to see if permanent deformation is an issue.  Something not tested before.

Thank you all for sharing your observations about these fabrics.  Never thought I’d get hung up on the fabrics, the tent design and construction having been the main focus.  And will try to make posts more readily understandable.  Granted, photos and diagrams help a lot with that, but it can be a lot of work, and laziness and time pressures are always lurking.

[Matthew / BPL]

Does this shelter have the DCF going then”wrong” way with strain applied along the bias? I think it’s oriented well with major stresses going horizontally along the hem and near-vertical stresses coming down from the poles. There are clearly some forces going at diagonal angles, though. Any thoughts?

[J-L]

@ Jon Solomon – thanks for sharing your experiences with various fabrics. The 30D silpoly from Extremtextil sounds like a good middle ground and possibly an ideal tent fabric.

 

@ Matthew – the Cirriform Min design does seem to have some tension along the bias, but so does almost every DCF tent out there. It can’t be avoided entirely and by itself, shouldn’t be an issue. What Dan said on page 1 of this thread is important (bold is my added emphasis):

Major lines of tension like that need to be aligned with the dyneema strands, not diagonal to them. If that’s not possible, then what is needed is a strip of DCF tape along that line of tension that has the strands parallel to the tension, so resist the tension so the material doesn’t pull apart. That’s what basically everyone else does (e.g. HMG, TarpTent, Locus Gear).

Here is a cartoon illustrating my understanding of the issue (someone correct me if it’s wrong!). The left image is a panel from something like a ZPacks Duplex. The right image would be a panel from something like a pyramid tarp. Without a reinforcement along the bias, DCF can stretch and fail early:

[Murali C]

maybe you could show the dyneema strands in the diagram? Like for example, on the zpacks damaged one, one set of dyneema strands are parallel to what you have shown and then there are another set of strands almost parallel to tension created by the stake? these set of strands are not parallel – but a little bit off – are these the one that are the problem? and hence putting tape along that will fix it?

[Dan @ Durston Gear]

Yes that sketch looks good. Rectangular panels can be a problem because you get that diagonal force across the panel (assuming there is a fixed point at all four corners, such as a stake or pole tip) and if the DCF is oriented square to the panel then these diagonal lines are on the bias. Most shelters use triangular panels (mids, X-Mid, Stratospire etc) so the edge panel are the lines of tension between fixed points, and there aren’t major lines of tension across the middle of the panel. Those lines of tension along the edges can be easily reinforced with DCF tape if the bias is an issue. Whereas rectangular panels would need tape applied across the surface or the panel to be divided up into triangles.

As an example, the Duplex has that rectangle whereas the HMG Dirigo was a similar shape but divided that area into smaller rectangles. Another solution would be to orient the material so the diagonals are parallel to the strands and then the edges are on the bias, and then the edges of the panel can be easily reinforced. That avoids adding tape across the open panel but this isn’t done because a there would likely be more material wastage and/or a big rectangle doesn’t fit onto the roll if if it’s patterened diagonally.

“the first generation X-Mid was plagued by major design flaws (lack of load-bearing side tieouts and a base perimeter that was notoriously difficult to pitch taut on uneven ground)”
Perhaps a bit harsh, but it is true that the side panel guyouts we’ve added to the 1P and 2P for the next batch help a lot in high winds to reduce deflection, and the additional cat cuts around the base do make it noticeable easier to get a tight base and tight sidewalls. We’ve also done some work on re-oriented some panels to better match the bias with where we do and don’t want stretch. That also makes it more sturdy (less deflection) in high winds.

Back on the topic of DCF, it is impressive how the low stretch of DCF makes it quite sturdy. There is an appreciable improvement with DCF.

“two points for me that are irritating character of DCF, bulk and cost. The bulk when compared to silnylon is just way too much.”
To expand on what I said earlier, it really is those 1.0 – 1.2oz/yd DCF floors that are the culprit. You can get a great woven at a similar weight with IMO better durability and certainly much better bulk. To illustrate, here is the X-Mid Pro 2, which is a 2P DCF tent but with a woven floor. It’s also singlewall, which makes it quite compact.

[J-L]

Murali, I added a grid to the cartoon. It gets a little busy with a full grid in the image.

Here’s the tension lines added to the failed tie out posted by Arthur on the 1st page. It’s obviously deforming, so isn’t a perfect 90 degree angle:

[Murali C]

Thanks…..should ask Joe at Zpacks about this…..as to why they have not fixed it on Duplex.

[Jon Solomon]

@ obx hiker: no explanation is as good as getting your hands on some fabric samples (don’t use your precious shelter) so that you can see what bias means in the real world.

@Sam and @John. A few numbers of tests actually performed on the ET 30D silpoly. Tested weight is 47g/m2 (1.39 osy) so slightly heavier than advertised, tear resistance is 10.5 and 8 daN depending on the direction (1 daN = 1.0197kg), and HH when new is 3200mm. The figures were provided to me by a respected and reliable tester (whom I’m not going to identify so that s/he can choose when to make those figures official). Pretty awesome stats, if you ask me.

@stumphges has mentioned on other threads the existence of a DCF variant, called HB, that has dyneema strands in two sets running at 90 degrees to each other, thus eliminating the problems of stress along the bias. It’s a mystery to me why this version hasn’t been brought to market in UL applications. Conceivably the cost would be much higher than the “standard” DCF in which the strands all run in the same direction.

[Dan @ Durston Gear]

HB (high bias) DCF makes a ton of sense and I have asked DSM about it, but the cost is extreme.

Regular DCF is expensive partly because it is assembled in a manual process (the strands perpendicular to the roll are laid by hand in ~18″ segments). When Big Agnes started producing DCF tents they got a sweetheart price because they said they’d have the production volumes whereby DSM could justify a new manufacturing line that was fully automated. So they got a great price on the expectation of a new production process that would have benefitted everyone, but Big Agnes went with the crazylight 0.3oz DCF and that combined with ~$1000 price tags meant those tents never really took off. DSM was losing money on that for a couple years, until they formally scrapped the plan this year and jacked the price back up especially for Big Agnes but also for everyone. Last I checked, the DCF tents from Big Agnes were out of stock and perhaps not coming back.

Anyways, all that is to say that DCF is expensive and only getting moreso because unfortunately DSM hasn’t made the investment in more efficient production.

I asked DSM about high bias DCF earlier this year and they confirmed they can do it. The problem is that then they outsource the production to another company where the whole production process is far more manual than even DCF. All 4 orientations of DCF are laid by hand. They gave me a price that was 5-6x the price of regular DCF, so the high bias stuff costs about $150/yd. It’s better, but the cost is insane.

[Jon Solomon]

@Dan Durston Thanks for sharing that info from DSM and confirming the astronomical cost of HB. Heck, even “standard” DCF is outrageously priced.

One reason for those costs might lie not in the production process itself but in the legal fees required to defend Royal DSM’s intellectual property rights. A web search reveals that they have a long history of successfully defending IPR in patent infringement cases. Last year they concluded a case in China related to protective gear using Dyneema.

Against that kind of well-defended IPR regime, the only option to bring prices down starts with a consumer boycott.

[Dan @ Durston Gear]

I think the DCF patent is up soon if not already. Also, DSM is considering selling their materials division, so perhaps things will change under new ownership.
https://www.canplastics.com/materials/dsm-mulling-sale-of-its-materials-business/1003457240/

[Jon Solomon]

I have read, too, that the patent did run out on the fiber itself but not the applications.

It’s encouraging to read that a concern for the circular economy (i.e., a greener approach to production/consumption) is behind DSM’s interest in selling off the materials division.

[Stumphges]

John,

Your diagram is good. However, although reinforcement tape can stabilize the ridgeline, the panel immediately adjacent to it will suffer deformation quite easily despite this. Although DCF is least stable on the bias (or 45 deg from the “grain,” or “warp/weft,” so to speak), if you have a piece of DCF lying around it’s quite easy to see that it is still very unstable even at 20 deg from the grain.

The only thing holding it together at those angles is the extremely thin and weak mylar layer (and the proprietary glue), and both deform permanently with just a little bit of tugging.

Forces along the bias also deform sil-coated woven fabrics, but there the weave of the fabric provides some constraint, and the elasticity of the silicone coating ensures that the weave distortion is reversed as soon as the load is removed.

So with a sil-coated woven tent, the panels adjacent to those angled ridglines will be deformed on the bias as you tension the corner tie-outs. But no problem, that distortion actually adds to the total panel tension. In addition, the cat cut ridgelines, when tensioned, will further load the panels, distorting the panels along their biases further. Again, no problem, the silicone-coating can elongate extremely before suffering permanent damage. And once taut, the panels can be deflected by wind impacts, further deforming them along their biases. But as soon as each wind passes by, the panels will bounce back to their original conformation, because sil-coated fabrics are a highly elastic composite.

But where the bias is deformed temporarily/momentarily in response to static/dynamic loads with sil-coated fabrics, those same static and dynamic forces will deform DCF’s mylar layers permanently.

In my opinion, DCF as currently produced, with no bias stability, is a lousy fabric for tents. It is overpriced, strong in two dimensions but shockingly weak in all others, and destined to deform and bag out over time.

As Dan Durston and others have pointed out, careful attention to reinforcement and seam layout can help with the instability issue along the seams, but this does little with respect to the adjacent panels.

The weakness of sil-coated woven fabrics is that they are too flexible under wind loading; their strength is that they are elastic. When silnylon or silpoly bend, they bounce right back.

The strengths of DCF are its stiffness (in two directions), low weight and hydrophobicity; its weakness is its lack of elasticity. When DCF bends, it deforms permanently.

A shelter that is permanently deformed is unlikely to pitch taut, and if it doesn’t pitch taut it won’t stand strong and silent in the wind, and at that point the stiffness advantage of DCF is lost.

I remember Henry Shires commenting in the BPL DCF podcast that, years from now, we’ll all look back and laugh that we used shelters made from DCF. Technologically, it’s an interim solution, and a rather bad one.

Now, if DSM would get off their asess and scale up production of bias-stabilized “high bias (HB)” DCF, rather than jacking up the prices on the unstable junk they are selling with monopoly leverage now…well, we’d be having a completely different conversation.

[Sam Farrington]

From Jon’s post above: “@stumphges has mentioned on other threads the existence of a DCF variant, called HB, that has dyneema strands in two sets running at 90 degrees to each other, thus eliminating the problems of stress along the bias. It’s a mystery to me why this version hasn’t been brought to market in UL applications. Conceivably the cost would be much higher than the “standard” DCF in which the strands all run in the same direction.”

Comparing this post with others, I’m not sure we are all on the same page, and that may relate to the poster who was confused by the use of the term, “bias”.  If bias means in a direction that is diagonal to the selvedge (side of the fabric roll), fine.  That would apply to both woven and nonwoven fabrics.  But if “bias” means diagonal to the “warp and weft” (the direction of the threads on a woven fabric), it expresses the reason for the greater stretch on the diagonal, because the weave allows it to happen if it is neither perpendicular nor parallel to the warp and weft lines of the thread.  If you pull along the thread lines or grain there is very little stretch in the woven fabric.  The challenge is to design and orient the fabric in the tent so the high stretch on the diagonal is where it is most beneficial, and the low stretch in the direction diagonal to the thread lines is most beneficial.  You can’t do that with DCF, and gather that it has been quite a challenge for Henry Shires and others to design and produce DCF tents that take that into account.

It’s hard to see much in the way of a weave in DCF, even though the fabric is often translucent.  I’ve found the DCF has virtually no bias stretch in any direction, so am not sure how the Dyneema fibers are laid out is of much use.  I do confess to not understanding the points made about damage due to the orientation of the stress forces on the fabric.  If parallel to the selvedge, or side of the fabric roll, is what is meant; then that may be doable with the simplest tarps.  But as soon as things get more complicated, as with a pyramid, or beaks on ends of a simple tarp, there will be seams running diagonally to the lines parallel to the selvedge.  However, if that is a big problem with DCF, it is hard to explain the success of all the more complex DCF designs put out by TarpTent, Locus, Trekkertent, and many others.

In order to get a grip on these issues, I think we have to do what many contributors to this thread have done, and focus more on our experience and observations of these fabrics, both in testing and in the field, as opposed to relying on the latest scuttlebutt from the self-appointed experts who abound in every facet of media and merchandising in our society and economy.  Or as Roger Caffin would put it, most of it is “BS.”  And being in the fabric business for much of his life, he should know.

The one thing that does concern me about DCF, is the permanent distortion mentioned above, for the reasons expressed about silpoly in my last post on this thread.  When DCF first came out as “Cuben,” I was looking at it for some bias stretch for a design in progress, but found none, so put it aside, and did so reluctantly since it halved fabric weight.  Then out came the heat gun, providing lots of stretch on a scale model frame; but what a mess.  But without the heat, there was no permanent distortion, just a lack of bias stretch which would have allowed it to conform to the model frame.  Perhaps the permanent distortion of DCF is a new thing, or something that develops over longer use.

Not having delved into DCF myself, here is an excerpt from a post by Nick Gatel, an experienced BPL contributor, on August 17, 2016 in a thread entitled, “We have the next Cuben Fiber and it’s amazing!” (The OP was promoting the Rockywoods 7D):

“I’ve been happy with my Cuben. I have a cat cut 8 x 10 tarp that is around 6 years old and my main shelter for around 5 years was a Hexamid.  Last year I replaced the Hexamid with a much larger Deschutes CF, which is probably the last shelter I will ever buy.”

So I think there is another side to this story, and have not ruled out DCF as one of the ways to get to an all purpose superlight shelter, assuming the stuff remains available at an affordable cost.  This thread seems to have attracted some attention, so I hope we get to see more posts responding to the the OP.

[Dan @ Durston Gear]

Lots of good comments here. I’ll just quickly note that I do find the orientation of the fibers in DCF fairly easy to see, and I find that deformation is substantial when tensioned diagonal to that.

TarpTent has a video at the top of their StratoSpire Li page which is in good sunlight so it makes the orientation of the strands easy to see. Below is a screenshot from that. Those thicker lines you see at regular intervals are perpendicular to the roll. They occur because they lay the strands on perpendicular to the roll (“selvage”) in 18″ wide bundles. Each bundle overlaps by an inch or so each time (giving double the dyneema strands there). So when you see these lines you know you have dyneema parallel and perpendicular to them:

Then for deformation, if you simply take a 6″ x 6″ square of DCF and pull on two opposite corners it’s quite easy to permanently deform it (assuming your square has the strands parallel to the sides). A 6″x6″ square will stretch about 0.5″ on the diagonal and not really rebound at all (e.g. it’s permanent deformation). This is the same thing that is occuring at the previously mentioned Duplex corners, where there is permanent deformation that is stressing the mylar until it eventually breaks down.

Conversely, a far high force does not cause appreciable deformation when applied parallel to the strands. That’s why adding DCF tape along the diagonal is so useful. It effectively stops this deformation. The key is having dyneema strands inline with all of your major lines of tension (e.g. running between all fixed points like stakes, guyouts, and pole tips). Of course there will be other lines across the fabric panels that are not reinforced, but if those lines are not between fixed points then there isn’t nearly as much stress on them so deformation is relatively minor and doesn’t seem to be a real world issue.

Anyways, I like DCF. It’s certainly expensive and has it’s downsides, but it’s the best material we have near 0.5oz and can work well with careful design.

[obx hiker]

I’d like to acknowledge that asking some of you to explain things that you understand so inherently from experience is to some degree a distracting and time consuming potential PITA but I sincerely thank you all for the information in this thread. Just looking back at page one it’s impressive how this has progressed and I can only believe and certainly hope it makes our community stronger by sharing more knowledge.

Now I have (of course) a couple of additional questions.

On page one there was this comment: “Major lines of tension like that need to be aligned with the dyneema strands, not diagonal to them. If that’s not possible, then what is needed is a strip of DCF tape along that line of tension that has the strands parallel to the tension, so resist the tension so the material doesn’t pull apart.”

Or could they be perpendicular (and BTW thanks John for the great diagram!)

And is there a source of .75 dcf tape?

Also it still seems to me that dcf,  like almost everything else in life; has advantages to go along with it’s disadvantages. Seems like the top issue would be catastrophic failure like Dirtbag’s hammock tarp and other episodes that can easily be googled up. While most seem to involve pretty extreme events and maybe some questionable sites as Sam pointed out that’s exactly when you don’t want to be dealing with a complete failure of your ‘shelter from the storm’.

The equally troubling problem is lack of longevity by any reasonable definition.

If we can find ways to avoid the one and ameliorate the other while hopefully the material improves or design improves or something new comes along…. Well that seems like where we’re trying to go.

[Sam Farrington]

Dan, thank you very much for your efforts to clarify understanding, if not my eyesight.  Like obx, I still have some concerns, the chief one being the lack of elasticity and ability of a fabric to maintain a taut shape.  Unfortunately, many nylons appear to lose this ability when wet, and the observations reported here about silpoly also raise questions about permanent distortion.  So I will need to test both some high quality nylons and polyesters with this in mind.  And I’ll study your Tarptent image to try to get a better sense of how to orient DCF panels and address these issues with taping .  Thanks again.

[Sam Farrington]

obx:  One source of DCF tape is Dutchware:

https://dutchwaregear.com/product/single-sided-dyneema-tape/

[Stumphges]

John, apologies for requisitioning your diagram, but I think this is a bit more complex than tension along ridgeline and hem. If tension were only along reinforced ridgeline and the hem (which is already oriented with the Dyneema strands in your diagram), we’d be fine. Some foresight by the designer with respect to panel orientation and stresses, as Dan says, would take care of the problem.

But the ridgeline seam and hem are not the only parts of the tent put under tension. What about the panel itself?

I’ve attempted to add vectors from the tieout to the diagram on the right, as well as corresponding tension vectors on the panel. I’m not certain – I’m no engineer – but I think this is a halfway decent representation of the lines of force (tension) on the panel, with arrow direction denoting tension direction and arrow length denoting tension magnitude.

So the greatest tension will be on the ridge. Great. And if we wanted to protect the panel bias from excessive tension, we would also have a high degree of tension on the hem, but tension on the hem is actually very low in comparison to the ridgeline tension. I’ve drawn a short, black arrow on the hem to better represent the magnitude of tension there.

And in between ridgeline and hem we have a lot of tension transmitted directly to the panel. We can artificially break that up into several vectors, as I’ve done with arrows added to the diagram. We can see that each of these vectors is of non-trivial magnitude and oriented perilously, deformingly, close to the “bias.”

Now, to make matters worse, many people, in an attempt to get the hems taut, will pull the stakes further apart than is ideal. This has the effect of applying greater tension to the hem, yes, but since the vector arrows on the panel above the hem will always be greater in magnitude than the hem tension vector, the net effect is to apply even more tension to the intermediate angles on the panel that are oriented on or near the bias. So any attempt to increase hem tension increases bias tension, and therefore, I would think, the tendency toward mylar and glue deformation along that bias.

Now, I’m sure this too is an oversimplification. We have forces coming from other seams. and the apex, and so forth. Perhaps all these forces balance out in some synchronistic and highly unlikely fashion, flowing harmoniously across the ductile biases without harm. I doubt that very much, but if I were selling DCF tents that’s the story I’d be telling. After all, who’s out there taking measurements of their DCF shelters at unboxing and at intervals thereafter?

What would we be finding out if we were?

Yama Mountain Gear has a nice page on their materials, and their comments about DCF are interesting: https://yamamountaingear.com/pages/materials

 

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