Few, if any, pieces of wood will pass the scrutiny of an 8’ level, and the superintendent of Bill Milburn’s homes in Texas wielded his level like a weapon. When I walked those houses, I needed a level, plumb line, string line, and more. Today, I have some of the same capabilities in my pocket, in the apps and search functions.
My favorite app is Clinometer, available on most phones, which measures angles, and consequently, plumb. Upon opening the app, the screen displays the angle, in relation to the body of the phone. For example, by placing the side of the phone against a vertical surface like this wall stud, it reveals that it’s about 1° out-of-plumb. A good place to use Clinometer is to verify the plumb of any member of a truss that will receive an interior finish. Because these types of members almost never line up exactly with pucks on a truss table, they will not receive additional jigging that maintains their straightness. Readings should remain within a range of approximately 1° when sliding the phone along the length of the member. [For all images, See PDF or View in Full Issue.]
Checking heights with Clinometer is straightforward, especially if you can position yourself on flat ground a distance away from the object, and roughly equal to the expected height. In this example, I sighted on the top of the tower’s platform along the side of the phone, while I walked away from the tower. In default mode, with the phone held still, Clinometer announces the angle. When I heard “45 degrees,” I verified that I was standing at a spot that was about level with the base of the tower. Then, I counted eight steps to the base and calculated: (8 steps x 3’ per step + 6’ my height) = 30’ height of upper platform.
I can check my results with a Google search, where I also learn that selecting a 45° angle yields an isosceles right triangle, and the advantageous result of rise = height.
A Google search can also determine truss parameters without resorting to math functions. For example, here’s a Google search to determine the end height of a 2x8 rafter. The heading “AI Overview” should prompt us to check the source cited, “rooftrusses.ca,” to ascertain the accuracy, which points to Roof Trusses & Components Ltd. near Toronto, Canada.
As with most AI inquiries, by entering further prompts, in this case “find the heel height of a truss to match,” we uncover the calculations that produce the result.
In this example, two sources are listed, “ChiefTalk” and “Plumb,” which are not recognizable to me. By clicking on the three dots, called an “overflow menu,” we see Google’s caveat, “AI is a work in progress.” However, we can probably rely on the result, because two different sources agree and one is from a truss company. Or, we can check the math ourselves.
These examples illustrate the increasing usefulness of the Internet, AI, and apps like Clinometer, of which there are many. While these provide valuable quick checks, they should be regarded as rough checks that point us in the right direction before verification with the standard tools of the trade, including measuring tapes, stringlines, levels, and, in the best case, surveying instruments. Yet they also provide valuable math lessons that can lead to a better understanding of the fundamentals of the truss business.