Enhanced crush strength construction multi-grade paperboard tubes

A multi-grade spirally wound paperboard tube of enhanced flat crush strength construction comprising:

• a cylindrical bodywall having a plurality of structural paperboard plies formed from paperboard of at least two predetermined densities comprising a first density and a higher second density that is at least 3% greater than the first density, said cylindrical bodywall being defined in radial cross section by a plurality of contiguous, centrally located paperboard plies formed from the higher second density paperboard, said centrally located plies being disposed between at least one inwardly located structural paperboard ply and at least one outwardly located structural paperboard ply, each of said inwardly and outwardly located paperboard plies being formed from said first density paperboard or paperboard of a density lower than said first density, and wherein between about 15and 85% of the paperboard plies in the paperboard tube are formed from said higher second density paperboard plies.