tarp-tent for bridge hammocks
The geometry of a bridge hammock keeps the JRB 11'x10' or Speer winter tarp from being able to tighten up the tarp all around the hammock. As I have a JRB 11'x10' tarp, and as I'd like to be able to have a tarp-tent, I did a little sewing.
Earlier I reported on pitching my tarp with a 10' ridgeline and 5.5' long sides, and pulled out the sides at the level of the spreader bars. That worked, but needed really long tie-out lines. I then tried pulling out the sides rigging a lightweight tent pole. That was a bit jury-rigged. So I made sleeves for these poles, clinched my teeth, violated the warranty on the JRB tarp and sewed the sleeves on the edge of the tarp. Measured how the pole bends, distance to the ground and so on, made some doors and stuck 'em on.
The doors are cut for a stake-out where the tarp is wider at the bottom and sides, hence higher off the ground. In this pitch I wanted the walls closer to the ground, which creates "excess" material in the doors, which I pull out and fasten with a stake.
I want to be able to use this tarp without the doors, e.g., in the summer, so they're detachable. I took 1/2" wide FreeMagic velcro and split it down the middle to create 1/4" strips. I sewed a strip along the hem of the tarp, and along the hem of the door. Every 12", on the tarp strip, I bar-tacked 13" of lightweight cord beneath the velcro, centered. I put overhand knots (I'll call these "anchor knots hereafter") on either side of the bar tack to prevent the cord from being pulled through. This leaves a strand on the outside and a strand on the inside, so that the fabric of an attached door can be gathered up and tied to get out of the way, like in just about any tent imaginable. At the corresponding location on the door hem I took about 5" of cord put an anchor knot in the middle of it, then bar tacked over the cord looped, then tied anchor knots on each end of the cord. This creates a small secured loop. The door is first tied to the tarp by running the inside cord from the tarp through the loop, and tieing it off. The gaps between the tie points are closed up with the velcro. The picture below shows the inside view of the tarp's line passing through the door's loop before being tied off. The proximity of the loop's anchor knot and tarp's line makes the picture a bit confusing, as does the visual lack of the anchor knots. Annotation should help.
Here's a view of the sleeve for the tent pole. While the doors are DWR 1.1 oz nylon, the sleeve is made of something somewhat heavier. Almost surely nylon, it came from the WM $1 bin. I put some heavier still material on the very end...at one time I was trying to keep these poles inside the tarp and the heavier material is intended to protect the tarp from the pole tip. But, I saw that there was still considerable pressure due to the pole pushing out on a small area of the tarp at that tip, which seemed to me to be a Fundamentally Bad Idea, so I opted inside to move the whole sleeve and pole outside. The sleeve is sewn to the top of the tarp hem, while the velcro for the door is sewn on the inside of the hem.
I tossed and turned on how I would connect the doors. In the end I put full width and full length strips of FreeMagic velcro down the edges of the doors, mostly because it was getting late and I wanted to be done with it. Indeed it was so late I screwed up on one door and put it on the wrong side. Fixed by putting a copy on the right side. Aside from the weight and the extra strip it isn't a bad choice. Maybe I'll figure out a use for that extra strip...
Here's a view of the inside.
I find that it is easy to get in and out of the tarp if I leave the spreader bar at the end in use disconnected. The hammock is rigged with a JRB Nest folded back to create a double loft half length UQ.
The tarp has been out in two days of some pretty big winds, with me in it last night. It is wonderful how it cuts the wind, well worth the effort put into making these mods.
I'm ready for winter now.
p.s. someone will ask... I don't recall the weight of the tent poles. They are what ship with Spires tarp-tents, each of which is 30-40 ounces, so they can't be much. The weight of the pair of doors at one end, plus an extra strip of still-to-be-utilized FreeMagic, is 4.5 oz, so figure about 9 oz extra for the doors.
Last edited by GrizzlyAdams; 01-02-2008 at 21:04.. Reason: weight