Love this stuff! Here's my 2 cents worth, regarding those jack rafter angles (better late than never)...assuming the plan view shows deck angles being 45 degrees as with most building hip or valley intersections , I always lay the jack on its side, draw the proper roof pitch plumb line, set the saw to 45 degrees and cut along that plumb line. No number crunching involved. Works, of course, for all roof pitches. Oh sure, what about that other line on the top of the jack? The layout line on the top of the jack can be developed by drawing a perpendicular line to the plumb line connecting to the edge (on the waste side of the plumb line). Measure that line length (call it 3" in this case). Now on the top surface of the jack, from where that 3" line intersected the top surface, draw a square line down, mark a point at 3" (remember that we know the saw angle has to be 45 since we are cutting along the plumb line, thus the line lengths must also be the same). Connect the dots from the top of the plumb line and the 3" point and you have the jacks top and bottom layout line angle. (I usually use a compass to transfer those line lengths) If I am dying to crunch numbers and check it I use my favorite trig formula ...the tangent of the saw angle equals the sine of the mitre (plumb line side of jack) divided by the tangent of the bevel (top or bottom side of jack). That formula can be applied for most situations, purlins, hip and valley ends. I find that most of angles involved in valley systems can be developed right on the timber as long as you remember to refer it to a plumb line, level line , or plan view deck angle. (We don't need no stinkin Hawkindales)...actually its great stuff but it is good to be able to visualize it all and not rely on remembering R1, P2, C5, Soh-Cah, whatever...time to have a beer!
