Thank you for looking into it Henry. I tried unfolding a loft created by scaling the larger arc down to create the smaller arc. This worked, the start and end angles identical. I then modified the start and end angles of the smaller arc, from the example that would not work, to match the larger arc. I did this in the selection info window. Once again I could not select the loft to unfold. It appears that this tool will only work if the arcs used are concentric.