I've decided to set about making myself a replacement shelter for both my two-person Tarptent Double Rainbow and my solo tarp/bivy set-up. This decision was largely inspired by recent backpacking trips that left me less than happy with the protected area provided by my tarp and bivy – they kept me dry and free of bugs for the most part, but not in any manner of decent comfort.
My thinking (aided with input from the always helpful forum members here at BPL) lead me towards a mid-style tent. By making the tent myself, I can save a few $$$ over what I would get from any of the cottage manufacturers, and more importantly, have something that is designed to meet my exact specifications. Basically, I am hoping to design something that meets the following criteria:
- considerable weight-saving over the Double Rainbow (1150 grams)
- not too much heavier than my solo set-up (370 grams)
- bug and rain-proof enclosed space that will be cozy for two people, but ample for one
- simple enough design to not provide too many headaches in construction
- cost less that my current solo and two-person shelter values (about $400)
This thread is intended to be both a progress-update thread, where people can see how my shelter is progressing, but also a place where I can solicit opinions and ideas on design decisions.
My first major decision was what material to use for the shelter – I eventually settled on cuben fiber, after a little bit of deliberation, because it is only about twice the price of 1.1 oz sil-nylon, and is about half the weight. Furthermore, I actually think it is easier to work with than sil-nylon, as it doesn't stretch, making patterns easier to cut out, and bonding cuben allows for more precise seam tolerances and eliminates the need for seam-sealing. Having worked with it a few times before, I'm pretty comfortable using it – this decision is pretty much set in stone.
My next decision was the dimensions. I was less interested in the snow-handling abilities of a mid tent like the MLD Duomid, and more in wind-shedding properties, hence I decided to make the peak height a bit lower – 48” when pitched to the ground instead of 58”. With this lower height obviously comes less head room, which I decided to mitigate by using a hex- or tipi-style design. The sides of the tent will bow out, giving more room where it is more needed, and keeping the overall fabric demand down. For my 'tight for two, spacious for one' fit, I decided on a head and foot tent width of 44” (two sleeping mats plus a tiny bit extra). The mid-tent width was 16” wider on each side, for a total width of 76”. I'm pretty happy with these dimensions, after doing some CAD mock-ups and playing around with a few different dimensions. The following drawing shows the tent pitched at 6” above ground and at ground with 20” wide, 72” long and 12” high boxes representing slumbering backpackers inside. Though I'm pretty happy with the current dimensions, I would welcome any input people have here – experiences, opinions, etc.
We are now getting into design decisions I am much less certain of. I have though about putting catenary curves on some or all of the seams. Do people think this is needed and/or helpful with cuben fiber? I've never used them before, but I don't think they would be too hard to implement with CAD design.
As far as additional features go, I am planning on having two high vents, on on the door side, on opposite it that are protected by bug netting and closeable with velcro. I will have guy points on every corner, and in the middle of the two side panels. Not decided yet if I will make the guy points out of all-cuben fiber, or if I want to use Dyneema patches bonded to the cuben with tie-outs sewn to the patches.
Another big question mark I have is what to do with regards to the floor and bug netting. I basically see three options here. One, go floor-less (use a polycro groundsheet) and have bug netting attached around the perimeter of the tent that is long enough to keep the mosquitos at bay. Two, put in a cuben bathtub floor and attach bug netting from the perimeter of the tent to the top of the bathtub. Three, put in the same cuben bathtub and bug netting, but also add netting behind the two door panels and a zipper so that it would be possible to open both the shelter doors in nicer weather for ventilation and views and still have a bug-proof space. The second option is the lightest, the third the most comfortable and versatile, and the first the easiest to design. What are people's opinions here? I'm a little concerned about using cuben as a tent floor – anyone with relevant experience?
Finally, as I don't use trekking poles, I need a good mid-pole. I've looked at most of the tent-specific pole offerings and have been largely unsatisfied – most are designed to bend (to accommodate the bent-hoop design of most tents) which is exactly what I don't want, or are heavier than I think they should be. I've looked at a number of carbon fiber tube suppliers, and a 0.5” diameter, 0.03” wall thickness wrapped carbon tube looks the best bet (from here: http://www.rockwestcomposites.com/index.php?p_resource=items&p_itc_pk=1). I'd use small sections of 0.5” inner diameter tube for the ferrules, and find some decent end caps for the top and bottom.
The preceding discussion pretty much sums up where I am with the project. Still working on getting my pattern finalized, and figuring out how best to do the vents, tie outs, zippers, bug-netting and floor. Any input would be much appreciated. I'll be sure to update this thread as the construction moves along.