| CPC B21C 37/185 (2013.01) [B23K 31/027 (2013.01); E04H 12/08 (2013.01); Y02E 10/728 (2013.01)] | 7 Claims |

|
1. A structure comprising:
a first curved sheet having a pair of first longitudinal edges parallel to one another; and
a second curved sheet having a pair of second longitudinal edges, the first curved sheet and the second curved sheet forming at least a portion of a tapered conical segment, and the first curved sheet and the second curved sheet joined to one another along a first seam extending in a spiral and along a second seam oblique to the first seam, and the first curved sheet and the second curved sheet differing in thickness from one another along the second seam, wherein the pair of the second longitudinal edges of the second curved sheet are parallel to one another, and one of the second longitudinal edges of the second curved sheet abuts another one of the second longitudinal edges of the second curved sheet at an intersection of the first seam and the second seam.
|