How did your DCF shelter age (and expire)?
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Arthur – that damage looks pretty severe to me. Sadly I would be quite hesitant to trust that shelter any longer.
For general reference, here are pictures of two of the corners on my first generation (Nov 2013) 0.74 duplex. I see absolutely no deterioration of any kind with the possible exception of some wrinkling from being packed and unpacked. And as Joe mentioned, you can clearly see the black hybrid fabric reinforcements. Another obvious difference between these corners and those on Arthur’s shelter is the double row of stitching at the corner attaching the tie-out, and the lack of the box stitch near the top of the reinforced patch. Could that box stitch be a contributing factor?
The back yard is a great idea. Unfortunately for this exercise, I live in the SW and storms are rare here until summer. I posted this earlier, here is the patch that Zpacks suggested with their patch own material. Stay tuned.
IMO, reinforcement patch size depends on how much the stress is spreading/fanning out. If you have stress from a single point that is fanning out (sketched below) then by definition the stress will be lower as you get further from that point. In this type of situation, you need the reinforcement to extend until the stress is sufficiently low/fanned out.
Conversely, if you have stress acting between two points (e.g. along a ridgeline) then the stress is not fanning out. Rather, you have similar stress along the entire path between those two points. In that case, if you have a failure it may not work to just make the reinforcements larger because it can just move the point of failure to somewhere else along that path that has similar stress yet isn’t reinforced.
Fanning stress typically occurs in tents that use traditional tent poles since the canopy is anchored and supported along lines (where the poles are), whereas trekking pole are supported only at single points (where the poles, guyouts, and/or stakes are) so most of the stress runs along straight lines and does not fan to nearly the same extent. With that said, in the real world stress does still dissipate on trekking pole tents due to factors like stretch, catenary cut, and because it’s getting further from other lines of tension that are also converging at that corner. So yes a larger reinforcement will help for these reasons (and a few others like spreading the strain of stitching) but because the tension that caused the failure is mostly along a straight path (between the corner and pole tip) it may just move the failure point outwards. That’s why almost all DCF tents have a reinforcement tape running the entire length of the span if there is substantial tension on the bias.
Disclaimer: I own Durston Gear where we design DCF tents.
Ahh yeah…that DCF dome tent, which was really a DCF fly I built to fit on an REI Quarterdome T2 tent. On hind sight, that fly must have been one of the first DCF domes ever built (circa 2010). The actual creation of it went pretty well, especially for a first attempt. Most of it was bonded but the few spots where I did sew (e.g. zippers) were a bit unsightly as I had a terrible sewing machine back then.
Unfortunately I don’t know how it turned out. The next year someone offered to buy it off of me and I wanted the money for some other gear, so I sold it and never heard of it again.
Regarding DCF and domes, any “stretch” that DCF has is more like deformation. Certainly you can stretch it on the bias, but it doesn’t rebound and that stretch is hard on the material (in addition to distorting it, it leads to delamination). So I certainly wouldn’t be comfortable relying on that stretch to make it work for a dome. Rather, I’m quite opposed to stretching DCF in that way. However, not all dome shapes need that.
If you think of DCF rolled up onto a roll of fabric, of course it rolls up nicely. That’s because even though the material is created flat, you’re only bending that plane onto a single (simple) curve. There are no wrinkles. Conversely, if you tried to fit a piece of DCF around something curving on multiple axes (e.g. a sphere) it wouldn’t work well at all. Imagine trying to put wrapping paper on a baseball – there’s a ton of wrinkles because it’s curving in multiple directions/axes.
Circling back to tents, a trekking pole tent almost always has the panels as flat planes so no problem using DCF there. Then for a dome tent, the panels could be single/simple curves where DCF can also work great, or they could be multiple/compound curves where wrinkles are going to happen unless you have a lot of stretch, so DCF is not going to work well there. To illustrate, consider the Locus Gear Djedi:
The Djedi is a dome tent, but all four sides are just simple curves so when you break up the shape into those 4 panels then it’s easy to construct with DCF. If you tried to create the fly with a single piece of DCF it would be massively wrinkly (obviously) because it’s a complicated shape, but when that shape is broken up into 4 panels they now just have simple curves where the fabric will fit perfectly. That’s the key thing – the shape needs to be broken up to give panels that only contain a single curve.
Unfortunately that’s not always possible because some shapes are curving in multiple ways at the same spot. Consider the Sierra Designs Mojo (below). It had a much more complicated shape where the panels are curving in complicated ways and you’re simply not going to fit DCF to that shape and have it look good. Flat panels like the door look good, and some parts with simple curves look good, but the sides with compound curves are always wrinkly and loose. I haven’t given this tent too much thought, but I don’t think it would be possible to break it up enough more panels so that you get everything to simple curves – DCF simple doesn’t work with this shape.
So to sum it up, I’d only use DCF on a dome tent where I can break the pattern up into simple curves. I wouldn’t rely on stretch to fit the material to the shape. With that said, some other companies are doing just this. It can be done – I just don’t think it’s ideal design. I’d prefer to work with a shape that doesn’t have those issues – and also needing to break the shape up into a ton of panels adds a lot of weight and cost so it’s the opposite of minimalist design.
Disclaimer: I own Durston Gear where we design and sell DCF tents.
Regarding peak guylines, if you have a situation where there is a problematic line of tension from a peak (e.g. running on the bias from a peak to a stake point) then yes a peak guyline would help in mitigating that since it would shift away some of the load. However you couldn’t be sure users would always use them, as they might pitch without and then a wind picks up, so I wouldn’t do this instead of solving the core problem but it is a nice augment. Of course a guyline helps for any line of tension that sees a lot of stress since issues can always come up (e.g. pulling out a stake). As for the location, the key thing is getting the guyline pulling along the ridgeline (for a 2 pole tent) or off the peak (for a 1 pole tent, ideally opposed with a matching peak guyline on the opposite side). Either way you are trying to pull on the peak, so the closer the guyline can attach the lower the risk of deformation. But as long as you have heavy reinforcement between the peak guyline and peak, there’s probably minimal risk of deformation since you’d never just have unreinforced DCF between a peak guyline attachment and the actual peak.
Regarding mid-panel guyouts, Henry mentions avoiding mid-panel guyouts on DCF tents because they pull at angle that are not in line with the material and that deforms the material via permanent pockets/bubbles of loose fabric. I agree with him on this. This point relates to the bias stretch I’ve been talking about (this bias stretch is largely what allows this to happen), but also is a bit more complicated (long story). Anyways, we agree on avoiding mid-panels guyouts on DCF since they are either pulling in a poor direction causing deformation, or if they are pulling parallel to the panel (staked right along the edge of the tent) where they aren’t really doing anything. Of course some other tents mentioned here do have these. They do work for adding space when you use them, but since it permanently deforms the material you have to always use them or you get loose ‘pockets’ on the panel from deformation, and over time it increases the risk of delamination. That’s much different than a woven tent where there is stretch but it rebounds rather than permanently distorting. Even then, you don’t really want to pull out/distort the shape, but rather just avoid it from deflecting inward, as MLD recommends.
With the upcoming DCF X-Mid, we have side panel guyouts, but they are designed to avoid the distortion Henry mentions. That’s because they are not mid panel guyouts (e.g. in the middle of the panel where they pull out at some perpendicular angle), but rather they are along a seam where the side of the tent changes slope, so the guyline extends the slope of the upper panel and thus does pull in line with the material. This sketch may make this more clear:
Disclaimer: I own Durston Gear where I design and sell DCF tents.
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