A patent issued this week for modifications to an American football that would give it better stability when thrown in a spiral. The patent (8,128,523) is owned by Russell Asset Management, which is related to the Spalding brand of footballs.
On the outside, the new football is indistinguishable from an ordinary football. But on the inside, it has a series of weighted strips (400) that extend around the middle.
The concentration of weight in the middle increases the moment of inertia about the weighted football's major axis, which helps improve the rotation of the football around that axis.
According to the patent, the standards for footballs govern the shape and total weight of a football, but they don't specify where that weight is located.
Generally, the footballs of the present disclosure will still meet these standards, although differing in the weight distribution.
The total weight of the strips is expected to be 80-90 grams, around one-fifth of the allowable weight of the football. Presumably, regulation weight is achieved by using lighter materials elsewhere in the ball.