So after over a year of waiting, I finally decided to pull out one of my large pieces of polycryo/cross-linked polyolefin (aka window shrink film) and make "Prototype 2" of my half pyramid. I wasn't able to pull it off in time for my recent trip with my boys, but I have Scout training this weekend with some good storms and winds in the forecast.
I had already had in mind a few design changes and I incorporated others from Dan's research and threads the past couple months - using the supplied double-sided tape to "hem" the edges and nylon washers instead of loops of tape for my tieouts. So here is the first pitch as barebones as it gets.
I bought a pack of 50 nylon washers at Fastenal for $2. They were too small for my trekking pole tip at the peak so I just used a metal washer I had. Detail of the pole connection.
Cross-linked polyolefin is known for being tricky to adhere to and I can tell the weatherproof adhesive on the 3M 2120 tape does not stick as well to it as it did to the LDPE so I used more tape than I would have otherwise. That may also make adding netting without sewing a challenge if I do that again. Here is a view with a full-size pad in it, where I'm playing around with differing peak heights and how far out the sides are pulled.
It took about 3 hours, which included cutting the size down to 6' x 9', taping all edges, taping the 2 ridges, adding all the tieouts and running to the store for washers.
There are a few things I'm still not decided on yet.
1. Adding shockcord loops to some or all 4 corners as I did on #1. This material isn't as stretchy as LDPE so it takes much more force to deform (though I had reinforced the LDPE with tape pretty well). My gut tells me it should be fine without them.
2. Adding tape down the center. I was forced to on #1 since that was a seam, but it did seem to keep the pitch tauter. The LDPE would deflect a fair bit in the wind. I may compromise and add a tieout a couple feet up from the edge.
3. I may add a bit more tape on some tieouts as I get a better feel for how the forces act on the material. For now I distribute the load perpendicular to the "ideal" force, but I've already seen where I don't always pull the front corners from close to 45 degrees. I may also need to change to the Gorilla Glue tape if 2120 does not hold long term.
4. Put the pole washer just a wee bit farther out from the edge so it's not on as much an angle.
Specs: 6' x 9' (finished size about 1" shorter because of the "hem"), total weight with the tieouts and washers but without guylines - 150 g (5.3 oz). FYI, the tieout tape and washers (9 plastic and 1 metal) added 22 g.
Thoughts on improvements?