I had a technical problem along about the time that family obligations spiked, which led to me eyeing but not touching the loom for a while. I'm back now.
The technical problem I experienced involved those selvedge yarns. While I had no trouble with their unspinning themselves, they did nevertheless loosen. The Navajo warp is so loosely spun that it slowly lengthened and eventually pulled apart. After I'd mended a selvedge thread for the third time, I decided to replace rather than repair.
First I needed a good replacement yarn. I found something at the local yarn shop that would serve: Kraemer Natural Skeins Eileen, a DK-weight merino yarn. It is tightly three-plied, soft but not at all delicate, and the appropriate off-white color of undyed wool. (After this project is over, I'll come up with some interesting way to use the rest of it; it's not a bad weight for nålebinding.) Instead of the two ends of Navajo warp per selvedge, I'm using two ends of this yarn per selvedge.
The second challenge was to replace the selvedge yarn. Using a tapestry needle, I tried threading one end up through the woven selvedges to parallel the Navajo yarn. The selvedges are in a wrapped technique (two additional turns of yarn between each pick), which means I had a lot of tiny weft loops through which to stick the needle. Standing on my little wooden stool and doing that was such fiddly work that I gave it up after an inch's worth. Instead, I anchored the new selvedge yarn around the warp beam, leaving a generous unworked end at the top. Then I weighted the new selvedges, put them where they belonged, and set the loom to rights.
When I remove the web from the loom, the first thing I will do is, as they say in the weaving magazines, "correct the errors." I'll start by threading that unworked end of each new selvedge yarn through the weft loops in a way that does not involve me teetering on a stool with arms outstretched leaning forward against thin air. (Tables are a grand human invention, and I wonder that we fiber folk do not make more use of them than we do.) Then I'll remove the vestiges of the old selvedge yarns. Then I'll fix any warp threads that have had to be repaired.
Oh yes, warp repairs. So far three warp yarns have broken. They all belong to one weight hanging at the back of the loom, i.e., they all come from the heddled back layer rather than the laced front layer. (I expected that broken warps would occur with the laced layer, which is secured firmly at a fixed point rather than movable, but so far that layer has held up beautifully.) The weight in question comes from the central point of the warp, the area where the two shed sticks overlap, the area I have to baby along with every change of shed. This area is subjected to more movement, stress, and displacement than the rest of the warp combined; it's not surprising that even this really high quality warp yarn is showing signs of wear. Fortunately, I have some experience fixing broken warps on my horizontal loom. The same principle applies here, so I'm not sweating it. If warps continue to break in that area, though, it could become a problem.
With about a foot of weaving done, I have to say that I'm not entirely convinced about the theory of using two short shed rods rather than one long one on a wide warp. My experience so far suggests it's more of a hassle than otherwise. The central two inches of the warp display a much looser sett than the rest of the warp, which is not surprising given how much more manipulation it undergoes than the rest of the warp does. Since I'll be working in that area to rectify the broken warps, maybe I'll also be able to ease the sett a little closer, drawing from the surrounding area where the sett is (naturally) a little tighter.
On the other hand, perhaps if both the rods were pulled at the same time, as by two weavers working side by side, it might be a fine solution. But for one weaver working alone at a wide warp, I'm just not sure this is the way to do it. But then, that was the whole point of this project, wasn't it? I'm looking for proof (or not) of concepts.