Dan Durston/Massdrop X-Mid

Discussion in 'Shelters & Accessories' started by theoctagon, Aug 3, 2018.

  1. Enzo

    Enzo Thru Hiker

    Mole and WilliamC like this.
  2. paul

    paul Thru Hiker

    Ive always found that line lock holding power isnt linear. Slipping is usually caused by the constant loading and unloading on different sides of the shelter do to leeward pressure drop and reloading in gusts. The bar on any line lock works great under constant tension and can easily be measured but real world reality is very different.
    oreocereus, Mole, dandurston and 5 others like this.
  3. dandurston

    dandurston Trail Blazer

    Yeah for sure the real world side of it is a lot more complicated. I think if a setup doesn't do well under a simple load, then it's not going to work well in the field since it'll also slip under a gust, whereas a setup that does test well under a simple load might be good in the field, but could be thwarted by other factors like constant load/unloading, ice, off-axis pulling etc.

    Those sure look like the right ones. I don't see "woojin" listed but they are called "string tensionlock" which is Woojin's name for them, and they look identical and are 10mm width. If you buy them, you should see a small "WJ" printed on them.
  4. Enzo

    Enzo Thru Hiker

    I've ordered 24 so will have 3 sets of 6 available for others.
    dandurston likes this.
  5. oreocereus

    oreocereus Thru Hiker

    I'd pay for postage down to NZ if they can fit in a reasonable size envelope :) But feel free to prioritize more locals if that makes more sense
  6. Enzo

    Enzo Thru Hiker

    I'd be happy to do that, but probably be cheaper to get adventure expert to post direct. If they won't, let me know and they're yours!
  7. vaguehead

    vaguehead Backpacker

    I've pre-ordered the Xmid 1P and should be getting it in the November run. The main reason is it's such a great design. By that I mostly mean the offset pole and sleeping diagonally. It solves the main issue with single pole pyramid design which is lack of head and feet room and also offers a very nice double vestibule for a little extra weight in material.


    Does anyone know the history of the basic design? I know this tent is designed by Dan Durston but I believe Andrew Surka was involved in the Sierra Designs High Route which is very similar. Did they collaberate? Is the basic idea from earlier? I'd be interested to know.
  8. Lempo

    Lempo Thru Hiker

    I'm sure the man himself, @dandurston can shed some light on the matter.
  9. vaguehead

    vaguehead Backpacker

    Ah! :) Thanks.
  10. Lempo

    Lempo Thru Hiker

    vaguehead likes this.
  11. dandurston

    dandurston Trail Blazer

    There is an article here on this topic that you might find interesting:
    https://backpackinglight.com/forums/topic/dan-durston-his-x-mid-how-it-came-to-be/

    But to sum it up, it evolved conceptually from the single pole pyramid. I was using a few of those (MLD DuoMid, Locus Gear Khufu) with a solo inner in the back half. I really liked the simplicity of the design but did find the lack of headroom to be key downside along with a few other smaller downsides, such as (1) the central pole being in the way, (2) having to sleep next to the back wall which would sag in under snow load, and (3) a lack of length due to a lot of inward wall slope on the ends.

    So I wanted to improve headroom/space while keeping the simplicity. I recognized that the simplicity was coming from:
    1) The rectangular base shape is easy to stake.
    2) Internal pole locations. When the poles are located inside the base, the pitch is simpler because the poles won't require guylines, it's wind stable throughout setup, and when the base is staked first you don't need to measure them. You can simply insert them and extend until taut. Whereas if a pole is at the edge of the base (e.g. pup tent) there won't be fabric on all sides to limit it to the correct height, so you need to measure the length plus it'll require a guyline and you have to support the tent during setup until you get that guyline in. Note that many tents have internal pole locations but you still measure the poles during setup. That's because you could fully stake the base and then not measure the pole, but when the base shape is really complicated (e.g. 6-9 sides) then it's hard to stake out accurately so an easier approach is to measure the pole, and then use that to reduce guesswork in staking the rest of the base.

    When I hiked the 4000km PCT in 2014 I spent a lot of hours mulling this over. I was contemplating add-on structural components that might improve space/headroom, such as struts at the corners (like TT's PitchLoc corners) or at the peak (like Zpacks Plexamid and TT Aeon), or a hoop at the peak. I came up with many ways to do it, but always lukewarm about those ideas because I didn't think the gains in space were worth the added weight/complexity, For example, the TT Aeon is a nice tent that is similar to what I was picturing back then. It is trying to accomplish a similar goal where it is sorta like a single pole pyramid but adds struts at two corners, along the backwall and at the peak to improve the volume. There is big gains in space but it loses the rectangle shape and adds a total of 6 struts, which is a pretty major penalty in added complexity and weight to get that volume.

    Fast forward to 2017 and I was thru-hiking again and thus had more time to mull this over. I decided that it didn't make sense to add a pile of struts when I had a second hiking pole anyways that was going unused. I realized I wanted to incorporate that second pole, while keeping the two key elements of a simple pitch (rectangular base, internal pole locations). As soon as I focused on that the X-Mid layout became obvious. If you're going to have two poles inside a rectangle base and still be able to sleep there, pretty much the only way to do that is have the poles on one diagonal with the sleeper on the opposite diagonal (which forms the "X" in X-Mid). The X-Mid name refers to this "X" layout plus "mid" background.

    In order for a pole to be reasonably stable without guylines, it needs to be set back from the edge by about 60cm or more. So in a typical single pole mid base of 250cm x 170cm you're left with a relatively small area near the center where the dual poles could go (shaded in grey, below left). The X-Mid positions the two poles as far apart as possible within this area (center panel) which maximizes the volume from two poles while giving enough width to sleep on the crossing diagonal. This works really well not only because you get as much headroom as possible in a guy-line free dual pole rectangular shelter, but also because other aspects fall into line such as (1) the sleeping position is centered under the highest area, (2) it creates large doorways with no pole interference, (3) it's radially symmetrical so it can have doors on both sides, and (4) you're not sleeping along the fly wall where wind and snow might cause it to deflect inward to disrupt you.
    [​IMG]

    The only other viable way to do get two "internal" poles in a rectangle is to put the two poles along the center line (above right) and sleep behind that like a single pole mid (or go a bit further here and shift those poles towards the door). That might be an improvement over a single pole mid, but compared to the X-Mid you're getting less volume from the two poles since they're closer together and more importantly, you're not making as good use of the volume because the occupant isn't centered under the high point. Rather, the occupant is against the backwall with potential issues from wind and snow deflection, and the doorway into the inner is potentially a bit tight as you squeeze between the two poles. That is interesting and maybe better than a single pole mid, but I don't think better than the X-Mid layout. I don't think anyone has done this with a side entry, but there are a few tents that put a sleeper on both sides of the poles with an end entry (e.g. Black Diamond Beta Light). That's alright but then you have poles between the dual occupants, single vestibule, one small doorway etc. Comparatively, the X-Mid 2P offers more volume via a longer ridgeline, while avoiding the poles between the occupants and further has dual doors, dual vestibules etc.

    I'm convinced that the X-Mid lay is the optimal layout for what can be done with two poles and a rectangle base. Nearly all previous rectangular tents have had the poles along the perimeter (e.g. pup tent, SD High Route). Aside from the downsides of perimeter poles that I've mentioned (need to measure, mandatory guylines) these are also less volumetrically efficient shapes (more fabric for the area) and have more vertical walls (such that wind performance is lessened).

    As it pertains to other shelters that have similarities, there are three other shelters I'm aware of with a diagonal ridgeline (the TT StratoSpire being the first and then the SD High Route and Yama Swiftline). At the time I designed the X-Mid I was only aware of the StratoSpire (I owned one). These shelters do share a diagonal ridgeline but are still quite different because the X-Mid is rectangular (vs hexagon) and uniquely uses a diagonal floor (the SS floor is square to the fly like a normal hexagon tent). So the X-Mid is likely the first tent to use a diagonal floor, and for sure the first rectangular tent with a diagonal floor. It's also the first "double diagonal" tent (both a diagonal ridgeline and diagonal inner). I wasn't aware of the High Route at the time the X-Mid was designed so it wasn't an inspiration, but it is aiming to accomplish a similar goal of getting more volume from two poles. It accomplishes that in a way I was trying to avoid (poles along the perimeter) so these shelters have their pros and cons. The High Route has a smaller footprint which can be nice, but the cons of perimeter poles (mandatory guylines, measuring poles, vertical sidewalls) and minimal vestibule area. I think the High Route makes sense if footprint area is a top consideration, but otherwise the X-Mid offers more vestibule area, dual doors, and a simpler design at the same weight.

    One last thing I haven't touched on much is volumetric efficiency. That sounds like a boring topic, but I wrote an article here to counter the conventional wisdom that a single pole pyramid is the lightest shape because it's the simplest. Actually, single pole pyramids have a relatively inefficient shape (e.g. require a lot of fabric for the volume they provide). The X-Mid achieves a more dome-like shape compared with both single pole mids and dual pole shelters like pup tents, so it optimum for what can be done with 2 poles. As that article explains, the X-Mid has more volume than a MLD DuoMid while using less fabric, so it is a much more efficient design. That's why the X-Mid fly can be as light as the DuoMid (both are 18oz in 20D) yet the X-Mid fly has dual doors, dual vents and more volume.
    Last edited: Nov 5, 2020
  12. Lempo

    Lempo Thru Hiker

    @dandurston

    How much do you think 1p and 2p would weigh in DCF?
  13. dandurston

    dandurston Trail Blazer

    The 1P uses 13 sq yds of fabric, so changing all of that from 1.2oz material to 0.55oz DCF would save 13 * 0.65oz = 8.5oz (240g), dropping it from 800g to about 560g.

    But I wouldn't use 0.55oz DCF for the floor, so let's say 600g, but there are potential weight savings if I stripped some durability and function, such as switching to #3 zippers, maybe 1 vent etc. So 550g might be possible in a double wall. Singlewall would be lighter yet. A singlewall stripped back to 1 door, 1 vent etc could get close to 400g.

    Similar proportions would apply for the 2P. Roughly 750g for the same thing in double wall and as light as about 600g in lightest possible singlewall.
  14. Lempo

    Lempo Thru Hiker

    I think sticking to double wall setup gives it more versatility with mesh & solid inners.

    Double wall at 750g sounds very tempting, as it's very spacious inside. With the DCF fabric width limit, would you be able to use the same pattern? Henry @ Tarptent said they couldn't do wider Strat Li (narrower than the standard Strat 2) because of this restriction.
  15. dandurston

    dandurston Trail Blazer

    I think what's going on with the Strat Li is that they prefer to do a narrower version due to the roll width (and maybe some other factors like wanting it to be lighter). You can always add seams to the tent if the panels are too large - either one down the middle to make it symmetric or one near a corner to minimize the length of the seam. But that adds weight and cost whereas a smaller tent saves weight and cost.

    In most cases a small corner seam isn't a big deal (TarpTent does this on some models, such as the Notch Li). A more notable seam pertains to the floor width. We have a seam on the 2P floor because we couldn't make a 50" wide floor plus bathtub from a ~56" roll. TarpTent might able to avoid that and some other seams with their 45" floor. If we someday do a DCF version of the 2P we'd consider that factor and could end up preferring a smaller tent too, but I can't say at this point which way we'd go because I haven't looked at it enough to know how much added hassle that would be. There would be some added seams if it was the current size, since many of the 2P panel just barely fit on the roll.
    peregrino_tom, Robin, Lempo and 3 others like this.
  16. oreocereus

    oreocereus Thru Hiker

    On this point, a single pole pyramid is hard to beat for the footprint:weather protection ratio. It may be volumetrically inefficient, but there aren't many other options that compete on weight for the weather protection. Yes the xmid weighs the same as the duomid, but a solomid sized tent works with less weight and a very compact footprint. I wonder how you improve the volume of something with a footprint that small? The xmid's very clever design necessitates it be as big as it is to provide enough sleeping space.

    I suppose the High Route and a-frame/pup tents go some way to addressing that, with the issues you've already noted.
  17. dandurston

    dandurston Trail Blazer

    I can agree with this if by "weather protection" you really mean wind performance specifically. Comparing the X-Mid and DuoMid which have similar footprints, the X-Mid is substantially better at snow performance because it doesn't have the low angled end walls where snow doesn't slide as well and accumulates on the tent, and also for wet/rain/condensation I think there are advantages to the X-Mid shape since more volume is helpful for staying sane in extended wet weather, and the steeper end panels help condensation run down the fabric moreso than drip.

    But for wind the DuoMid would have the edge. This occurs not because of the wall slopes, but just because the DuoMid has so much less volume in the upper half. The slopes of the largest (door) walls are near identical at 59 degrees (DuoMid) vs 60 degrees (X-Mid) but the area of this side (e.g. the profile to the wind) is much smaller in the DuoMid due to less volume from one pole. The optional peak guylines of the X-Mid help to compensate for that, but ultimately I do agree the DuoMid shape is higher wind performance. Since the wind performance is fundamentally coming from the low volume, I think it's an unavoidable trade-off where you can't retain the wind performance while gaining volume/headroom. For example, if you added peak struts to the DuoMid, wind performance would suffer.

    Wind performance versus footprint size is another unavoidable trade-off. With any of these tents you could use a smaller base, but you'd get steeper walls for less wind performance - unless you shortened the poles to accept less volume instead. For example, we could move the X-Mid poles closer to the perimeter to reduce the footprint (with the very small SD High Route being the logical conclusion of this journey) but wind performance (and volumetric efficiency) suffers. Combining these two trade-offs, if we wanted more volume in a DuoMid we'd have to accept a larger footprint or less wind performance. If we wanted a smaller footprint in the X-Mid, we'd have to accept less volume or less wind performance, etc.

    Overall, if someone is not concerned about wind at all, the High Route shape would make the most sense (max volume:footprint), whereas if someone is very concerned about wind the DuoMid would make the most sense (max wind performance:footprint), with the X-Mid in the middle on these ratios.

    The other side to this is not reducing the wind load, but just handling it better. The X-Mid has higher drag than the DuoMid, but also peak guylines to help with that. We could go further here and add a side panel guyout above the door (perhaps we should) which would better support the same wind load. Quite a few people are using the door toggles for this now, but the strength of that loop for this unintended use is questionable (although no one has broken one), so we may add a grosgrain loop here in the future to better allow this.
    Last edited: Oct 28, 2020
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  18. oreocereus

    oreocereus Thru Hiker

    yeah fair enough. I don't camp often enough in significant snow, to have the issue of the shallower walls. Haven't had dripping inside in a mid from condensation. I meant overall wind performance and "360 degree coverage" from rain or wind blown rain.

    the volume of the x-mid is very generous, without a nest at least. But with necessary shape of the design, I don't think you could reduce the volume much without making the inner too cramped. So it's large footprint is an inevitable trade off of its clever design (and a bonus in many situations - it's more vestibule than I need, but in use I'm never *inconvenienced by that once I have it pitched on a suitable site)
  19. dandurston

    dandurston Trail Blazer

    Yeah I wouldn't want to reduce the size of the inner as a means to reducing the footprint. I'd have to trim footprint off the vestibules, which means steeper walls/reduced wind performance, which I don't think is an improvement.
    cathyjc, Lempo and oreocereus like this.
  20. vaguehead

    vaguehead Backpacker

    @dandurston

    Thanks a lot for your response, really interesting and learnt a lot. Plenty of stuff I hadn't considered. Can't wait to get my hands on the Xmid, have a trip planned for it in Wales.
    dandurston likes this.
  21. vaguehead

    vaguehead Backpacker

    @Lempo Thanks! Will listen to that!
  22. vaguehead

    vaguehead Backpacker

    That's really the icing on the cake for me. I don't need two vestibules, but very nice to have two. Bag and shoes go in one. Contents of bag go in the other. I think I'll make a polycro groundsheet that covers the ground in one of the vestibules so nice and clean there.
    oreocereus, dandurston and SteG like this.
  23. oreocereus

    oreocereus Thru Hiker

    A nice bonus of this, if you're on grass, is that it traps moisture under the sheet and reduces the condensation inside the fly. Anecdotally, anyway.
    peregrino_tom, vaguehead and Lempo like this.
  24. Enzo

    Enzo Thru Hiker

    Adventure expert line loc lite have arrived and have wj on so they are the real deal :thumbsup:
    FOX160, WilliamC, Lempo and 1 other person like this.
  25. dandurston

    dandurston Trail Blazer

    A quick note to say that Drop is now selling the updated version of the 1P and 2P that have the thicker 2.5mm cord for excellent holding power, and new V stakes. Collectively this gives far better holding power in stormy conditions than the previous 1.5mm cord and ti skewers.

    If someone has a previous version and wishes to retrofit, any 2.5mm accessory cord will do and the stakes are the same as these ones - although there are many good options for wider stakes.
    https://vargooutdoors.com/titanium-crevice-stake.html
    FOX160, Arne L., qy_ and 4 others like this.

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