The Nitty-Gritty of an NFL Football

I want to get to the nitty-gritty of the design of the NFL football.  Kids love them; grown men love them.

Obviously, I love them, too. On my recent visit to the Pro Football Hall of Fame in Canton, Ohio, I took a picture of the NFL football display.

I am using the words "nitty-gritty" in the context of getting to the heart of the matter or to the basic essentials of the design of an NFL football. 

Those basic essentials of the design of an NFL football are based on scientific and mathematical concepts.

The details of the manufacturing of the NFL football took me by surprise. The precision, science and mathematics are fascinating.

Here are some of the specifications:

"The ball is about 11 inches (28 cm) long.

"It is about 22 inches (56 cm) in circumference at the center.

"The exterior of the ball is made of leather, which is required in professional and collegiate football. Leather panels are usually tanned to a natural brown color, which is usually required in professional leagues and collegiate play.

"At least one manufacturer uses leather that has been tanned to provide a "tacky" grip in dry or wet conditions.

"The leather is usually stamped with a pebble-grain texture to help players grip the ball.

"Some or all of the panels may be stamped with the manufacturer's name, league or conference logos, signatures, and other markings.

"Four panels or pieces of leather or plastic are required for each football.

"Two of the panels are perforated along adjoining edges, so that they can be laced together.

"One of these lacing panels receives an additional perforation and reinforcements in its center, to hold the inflation valve.

"Each panel is attached to an interior lining. The four panels are then stitched together in an "inside-out" manner.

"The edges with the lacing holes, however, are not stitched together. The ball is then turned right side out by pushing the panels through the lacing hole.

"A polyurethane or rubber lining called a bladder is then inserted through the lacing hole.

"Polyvinyl chloride or leather laces are inserted through the perforations, to provide a grip for holding, hiking and passing the football.

"Before play, the ball is inflated to a specified air pressure

"The ball weighs 14 or 15 ounces."

More research revealed the following:

"Since 1941, Wilson Sporting Goods Company, currently based in Chicago, Illinois, has been the official ballmaker for the National Football League (NFL).

"For all NFL games, the only sanctioned ball is a Wilson brand ball.

"The ball must measure 20.75-21.25 in (52.7-54 cm) around its middle (also called the girth, short axis, or belly); 27.75-28.5 in (70.5-72.4 cm) around its ends (the circumference, long axis); and 11-11.25 in (28-29 cm) from tip to tip (the length of the long axis). It also must weigh between 14-15 oz (397-425.25 g).

"All balls designed for professional use are stamped with "NFL" on them for the National Football League and they also bear the signature of the League commissioner.

"A box containing 24 new balls is opened before each game; 12 balls are put into play during each half. After the game, the balls are used for practices.

"Those balls that are used in the Super Bowl game also have the names of the participating teams along with the date and location of the game."

When I read the statement below, I thought, let's learn the "nitty-gritty" about footballs:

"There have been many attempts to alter the football's design; for example, dimples on footballs have been tried, but there was a tendency for dirt and mud to get caught in them."

The football is not a simple spheroid, it is a something else, according to a mathematician:

"An Americal football is a prolate spheroid. This means that its axis of
symmetry is longer than its other axes. An M&M candy, on the other hand, is
an oblate spheroid.  Its axis of symmetry is shorter than its other axes." Richard E. Barrans Jr., Ph.D.

Another enlightening comment by Vince Calder:

"A football is not really an ellipse. The equation of the projection onto
the x/y plane of an ellipse of revolution is (x/a)^2 +(x/b)^2 = 1. where 'a'
and 'b' are the semi-major and semi-minor axes, respectively.

"The football is too "pointed" on the ends to be an ellipse according to the definition
above.

"The general name for objects that have an axis of symmetry, like a
football ignoring the sewing and the laces, is an oval of revolution.

"There are methods for generating analytical equations of such geometric
figures, but space does not permit that discussion in this forum."

This B/R scribe's comment is that the football can be considered a "deformed sphere," a term used in mathematics and engineering.  It is called deformed because it has undergone a transformation altering a = b to a < b or a> b.

In other words, if in the equation (x/a)^2 +(x/b)^2 = 1, we have a = b, then it would be the equation of a ellipse.  If the ellipse is rotated in space, it yields an ellipsoid.

Note, however, the football is too pointed to be called an ellipsoid, although there are some similarities. 

This is getting to the nitty-gritty of the design and manufacturing of an NFL football.  As you can see, there is science and mathematics in everything, even in your favorite autographed football.

Enjoy NFL football.  Remember, as you watch all of that action, you are watching science, physics, and mathematics in action.

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