The math said that 18 - 4" triangles should be 6', but apparently I've mismeasured those triangles, because it came out more like 8'. What?
I guess the triangles were already a little longer than 4", and I guess the knots connecting them added a little, but I did not expect this much.
Of course, they haven't been washed and blocked. The plan is to get an entire row done, stitch it together, and then block that. But even with 10% shrink, it'll be more than 6'. Oh well, not complaining.