Patent ID: 8256168

Claim:
A structure comprising: a plurality of regular hexagonal tubes, wherein: the tubes have central axes that are straight lines and parallel to each other, each of said tubes has at least one hollow, the tubes are open on both ends, the ratio of outside perimeter to wall thickness in at least one cross section perpendicular to the central axis of each tube that includes at least one of said hollows is greater than 27.7 to 1, and the tubes are placed end-to-end such that an end of a first of said tubes is contiguous to an end of a second of said tubes; and a minimum of five inserts, wherein: each of said five inserts comprises a region having an exterior shape from a set of a 60/120 degree rhomboid prism and a 60/120 degree rhomboid cone, the exterior shapes of said inserts in said regions are similar to one another, the exterior shapes of said inserts in said regions are similar, the exterior shapes of said inserts in said regions are equal in size, said regions of three of said inserts are at least partially inside one of said hollows of said cross section of said first hexagonal tube, said region of one of said three inserts is at least partially inside one of said hollows of said cross section of said second hexagonal tube, said region of the two of said minimum five rhomboid inserts that are not at least partially inside one of said hollows of said first hexagonal tube are inside one of said hollows of said cross section of said second hexagonal tube, and the longitudinal axes of the inserts in said regions are parallel to each other and parallel to the central axes of the tubes.