Originally Posted by hangnout
Looks great! In the pic above I was trying to figure out what purpose this seam was for? Easy way to sew in end or other purpose?
I've been experimenting with a different way to attach an endcap. See below.
The idea is to start with a rectangular piece whose long edge is exactly the fabric width of the fabric under the spreader bar and make a couple of honking great darts in it (red lines). The 4" offset is needed to get the two cuts in a dart to be the same length. The seam you comment on is bias tape that brings those cut edges together.
I have been frustrated in the past with getting a parabolic endcap cut to have exactly the right arclength (including seam allowance) and to deal with fabric stretching and slipping so that I end up with a out-of-skew endcap. This design uses a little more fabric, but is a lot more forgiving in terms of sewing errors. Fault tolerant endcap design is what I call it