I'm going to make make my own rather large trap for Winter camping (and probably as a dinner fly for non-hammock family/group trips). Similar to JRB's 11'x10' Cat Tarp and/or Speer's WinterTarp. I've made another large silnylon shelter (2# 3.5 person tarptent), so I don't have any major concerns about the project, except for this one...
I'm trying to determine how much of a difference having shallow catenary edges helps over simple straight edges. I own a Catenary tarp (only the ridgeline is catenary) and it is obvious that it helps to make an easy setup, but I'm not sure about edges. Any thoughts? "Everyone is doing it, so it must be good" is the obvious response, but I was looking for more.
One particular question I have about both JRB's and Speer's winter tarps, is that the edge with the catenary curves becomes the "doors" when setup in "winter mode". Yet, due to the curve, the "doors" don't close completely, so why have the catenary curve if that is going to be my primary configuration? I can sort of see how it helps reduce edge flapping in configuration in which the catenary edge is parallel to the ridge-line, but I see it more as a defect in the "winter mode".
That said, if I were to make catenary edges using the various spreadsheets floating around the 'net, how do I determine what is "the best" depth for those curves over a given length? Is there a "rule" like "make the depth 5% of the length"?
And while I'm probably not willing to spend the money, anyone have a source for Spinn fabric?