Remember whining about math? When will I ever use this in real life? Well, I had one of those moments proving how math is important in real life

Problem: Standard L-flashing needs to be re-bent to a different angle to provide a runoff slope for rain. How do you determine the proper angle and (practically) how do you bend the 10 foot long flashing segments easily in the field without a metal break? The original flashing is 3 x 3, bent at 90 degrees.

Answers: The flashing is being applied to a wall and a horizontal ledge. An obtuse angle will allow for a good slope to shed rain water from the roof above it. The decision was to put a ½ lift on the wall side. This requires a new angle on the flashing because 90 degrees will not shed the water. Using my smart phone, I located a site that could calculate the sides and angles for a triangle with a 0.5 side and a 3 hypotenuse.

http://www.csgnetwork.com/righttricalc.html
The website calculated the interior angles of the triangle ABC. The interior angle at B was about 81 degrees, making the outside angle at B equal to 99 degrees. The field solution (rounded) is to add 10 degrees to the L-flashing (totaling 100 degrees)

Bending: Without a sheet metal break, how do you open the angle on the long flashing segments accurately? Original Euclidian geometry and early trigonometry was based on lines intersecting a circle. The answer to opening up the angle is easy.

Using a common 4 diameter length of ABS pipe, simply lay the L-flashing on top of it. Using a 2x4 lengthwise along the flashing, press down firmly along the corner to re-bend the flashing. Using a protractor, measure until the angle is 100 degrees.

Then we finished the application of the flashing to the wall !