Larry Lenger introduced the relative turning radius in his article using his equation #4. That equation creates the cubic wing value by multiplying the wingspan times the wing area.

Neither Roger Jaffe nor Francis Reynolds used wingspan in the formula they used.

An unknown person to me, created a formula to "create" a comparative cubic value from a given, measured area value. The square root of the given wing area is multiplied three times, which is known as raising to the third power or cubing.

The same value can be derived by using the square unit value raised to the 1.5 power.

For our use in airplane modeling, the units of square feet (Imperial) and meters (SI) can give meaningful comparative values.