pi r^2 to find the area of a circle
- pi is 3.14
- r is radius, or half the diameter of a circle
- ^2 is squared, or the number times itself
- pi r^2 is 3.14 X the result of radius squared
- pi r^2 gives you the square inches of a circle
You want to change the shape of the opening but keep it the same square inches. The length of the port is not a factor and you will leave it exactly the length it already is.
- Find the square inches of your circle using pi r^2 (ex. a 6 inch diameter circle yields 28.26 square inches)
- Decide on the longest side you want your square or slotted port opening to be
- Divide the total square inches of the circle by that long side, in inches (ex. 28.26 / 11.5 = 2.46)
- The result is the measurement of the shorter side of the port opening
In the example, the 6" round port equals a slotted port 11.5 X 2.46 inches. Round measurements to the nearest Imperial or metric value. 2.46 would be 2 7/16 to 2 1/2.
You should keep the ratio of length to width of the slotted opening at no greater than 8:1.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.