myog mountaineering cuben tunnel tent?
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Hi Pierre
In my opinion … you need to reinforce the key bits of fabric and sewing properly.
In the image here you will see what I mean.The thick red lines are a layer of Cuben fibre which has been folded over to protect the seam in the fly itself. The sewing (thick blue line) in this line of stitching is CRITICAL to the whole tent. It must be strong, and it must be reinforced. I use Rasant 70 thread here.
You will also see that the sewing on the pole sleeve is protected in the same way: the pole sleeve fabric has a reinforcing strip over the top.
This is probably a bit over the top for a summer-use tent for sheltered situations – but you did say you are building a tunnel for the mountains.
Cheers
I just tested Roger's technique for the sleeve attachment and… The reinforcing tape under the fly (on top in my testing) started to peel of almost instantly at 20lbs of load. I'll let it overnight to see where it gets. (This is because I DID NOT PUT ENOUGH TENSION ON THE SEAM BEFORE APPLYING THE TAPE!!! Roger's sleeve works great when you do it right!!
My own sleeve rig broke off at 40lbs just at the junction of the reinforcing cuben tape but not for the sleeve I was testing. I'll have to retry this one with new fabric strips.Here is a pic from my attempt at Roger's technique.
Cheers
PierreYeah, I agree with Roger. But I believe that the forces applied approach infinite across the tent fly as it pulls down on the fabric. Even if you apply the tape under tension, as was suggested, it will try to pull itself apart as the tension is removed and the cuben springs back to the rest position. Hence, every set-up and tear-down of the tent will eventually, probably in a few uses, cause the tape to loosen. I have a couple suggestions:
1) Use a heavy sleeve. You can likely do this with 2.4oz cuben.
2) Tape will not work in peel without reinforcement.
3) Tension on the tent will offset tension on the sleeve. This means they will work together. Usually, a distributed loading will be stronger than single point loading.
4) Three or four stitches are needed for strength in severe wind.
This is not an engineered static load joint. Rather it is a dynamic load joint. The more wind, the more tension on the tent body. The more tension on the poles/sleve. The joint will ofset the extreme load deformation causing the tape to peel loose inside. The heavy cuben fabric should resist any catastrophic pole collapse, but you will always have this item present, poles are just so strong. The tape should provide any sealing at the seam, and, reinforce the joint, too. The stitching will reinforce the joint without all the pressure being applied to one row of stitches. This will much reduce hole elongation in the tent body. This will likely not test really well under your rig. You need the tent fabric under dynamic tension as you increase the load. This happens naturally in a wind, though.
Nick Bedouin had some to say on this subject here: http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=58096&disable_pagination=1
Roger C: "I doubt you can bend CF tubing tight enough for a real tunnel design"
Fibreplex seems to manage it. This image is from Doug Johnson's BPL article
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Anyway, the company supplies 145* elbows, so using three for an included angle of 105* using 4 of their 31.5" sections would give a free width at the pole feet of 80.55" (allowing for the additional length the elbows provide. Pulling that in to 72" for a generous porch space plus sleeping room for two would put a bit of outward stress into the pole to resist wind and leave me with a generous 46" of headroom at the apex sloping down to a windcheating 20" at the secondary pole.
Too tall! I hear you cry, but then people have been telling me that since I was 15. ;-)
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