Tunnel tent design help: Purpose of slanting poles?

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    Roger Caffin
    BPL Member


    Locale: Wollemi & Kosciusko NPs, Europe

    Geoff – is that Ionosphere a one-man bivy? I suspect it may be, and the same for a lot of other designs. Which really makes a lot of my comments ‘not to the point’ as I am always thinking in terms of a 2-man shelter, for me and my wife.


    Sam Farrington
    BPL Member


    Locale: Chocorua NH, USA

    Randolph J, aka Randy,
    Funny that just as I thought of a design, Geoff posted the Ionosphere.  Heavy though, especially for a ‘glorified bivy.’

    The threading operation for the Warmlite poles seems incredibly tedious, so don’t think you should base your decisions on that. With pole sleeves broken at the top center, you can also add elbows to create more defined peaks and help shed rainstorms. While not a great idea for a 2P tent, this takes up minimal extra space on a 1P, and the gothic, or pointed arch created will be stronger than a simple hoop. But no reason not to stick with the parabolic flexed hoops if you are set on them. But please do not put too much faith in Slumberjack’s tent designs. Can’t recall their tents being well rated on BPL, not to say that it could never happen.

    Since the tunnel is small inside, and a quick exit can be critical for any number of reasons, the side zips can help, but they can also be a source of leakage. Another way would be to make the rear hoop lower, and the front hoop a little higher to create a larger front vestibule, not to mention still more water shedding. This would allow moving the front hoop a little closer to the back one, and increase and open up the front vestibule for quick entrance and exit. And provide more inner space near the front of the tent. And with a smaller pole at the rear, the design will lend itself better to one peg holding the rear cone-shaped cover tightly. You can always run two short cords to two stakes in a windy pinch. Just leave enough space in the rear walls to avoid rubbing the inside wall when condensation does form.
    A drawback is that on entry and exit in rain you’d need to keep back from the area under the unzipped vestibule flap. Canted hoops or arches help with this also. With the higher front peak, which weightwise should be a wash what with the lower rear peak, you’d have more room to move about.

    The floor projecting into the vestibule will need something to hold it in place. One approach is to offset the center of the vestibule slightly, so more space is covered when the vestibule door is open. The single door zip, which should be flapped, should run from the front peak straight to the vestibule stake point, and can be opened part way in rain storms. How far you want the floor to extend toward the vestibule stake point should avoid flooring under an open vestibule door, and allow for the inevitable water that will splash inside. It is a rare tent with vestibule walls all the way to the ground. Theoretically impossible with all the ground cover and irregularities, unlike a totally flat surface.

    The pole sleeves, with or without the pole sections folded inside, should be fairly narrow, unless you intend to add the silvered fly, in which case a wider sleeve would allow more space for ventilation. With an inner tent that is coated waterproof, ventilation is needed even more to limit condensation; although from what I read on BPL, and on your posts, your locale creates far less condensation than most other areas. Warmlite has long used inner and outer tent walls that are both coated. and it apparently works, to some extent at least.

    Finally, you could create a bivy with some supported coverage over the head area. This has been done often. But my impression is that this is not what you are looking for.

    Again, good luck with your project, and please let us know how it turns out and performs.

    Geoff Caplan
    BPL Member


    Locale: Lake District, Cumbria

    The Ionosphere is very much a 1-person shelter – though it’s long enough for taller people.

    I’ve only been inside one in a store. Not easy to get into, but surprisingly spacious inside – except that there’s no way you’re sitting up in it. Didn’t feel claustrophobic. Plenty of room for gear, but no covered vestibule for cooking. So basically a luxurious bivy.

    And extremely stealthy, which accounts for much of it’s popularity in England where lowland camping is mainly illegal.

    Most reviews suggest that condensation is not a problem. Presumably the inner helps here, because the venting options aren’t extensive.

    It uses a cheap and heavy fabric, which accounts for the weight. But it certainly looks robust, and seems to have been selected to appeal to the military market. It’s quite widely used by US and UK infantry.

    Moab Randy
    BPL Member


    OP back again:

    I guess we should rename this thread “Bivy tent design” or end it now.

    Geoff—I’m sure my minimalism would wear on me if I were in a wet climate or found myself tentbound for long periods, and I would be wanting more space. But for me a small, snugly, warm shelter that I know can weather the storms I encounter—my storms—and that I know I can erect quickly and just collapse into is very appealing. It will be my coccoon. It will let me hike into the night without so much worry about finding a good spot or having the time to pitch while exhausted. It’s a lifestyle choice, as you can relate to from the alpine side of terrain.

    re: the Ionosphere: Wow, 14 stakes—sounds like a record, especially for a small tent. I guess we can be pretty sure it won’t be blowing away anytime soon. For mine, I suppose I could get up to 8 if I were really worried—ends, corners, two side guys.

    I never used the Slumberjack in really cold conditions, just a lot of wind and heavy rain. No issues with condensation, despite the lack of upper vents. It is a double-walled tent (noseeum interior), which mine will not be (but mine will have better ventilation).

    Sam—the tent you are describing is a different one from what I have in mind. Maybe I’ll try those ideas for the next build. Sounds a lot like the Lofoten.

    I’m intrigued by the 45 degree elbows offers and the notion that it will be stronger than a parabola. Maybe for my next tent. So many tents still to make! I’ve never had any issues with either of my tents shedding rain, so I’ll probably be ok using the rear pole from my 1980 Warmlite with alteration. I never meant to say that Slumberjack made a good tent, only that it gave me the idea for a lightweight coccoon with big side windows/door, all for only two stakes.

    Thank you all again. See you on the next thread



    Geoff Caplan
    BPL Member


    Locale: Lake District, Cumbria

    Randolph – no need to justify your choices to me. As I said, sounds as though you are right on point with your thinking, and far clearer than most!

    The great thing about MYOG is that we can make ourselves something that fits our needs precisely, even if they are unconventional.

    Do let us know how it goes!

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