Framerman
While this is 100% true, one of the previous threads was describing how to do it "by the book" This would be for simple roof stick ins using a framing square and calculating the hip length as well as the amount to drop to allow it to lign up correctly. By calculating the length of a hip, you are actually figuring its length at the center of the rafter. Its impossible for us to lay out the hip rafter from the center, so therefore it must be "dropped" appropriately to make up for this. That being said, myself. I usually don't calculate the hip length. I usually measure it in place, being sure to measure at the edge of the rafter where it planes at the wall. Sounds like you do it this was also. While knowing all the math of roof framing is important, many times in the field we come up with more practical methods that allow us to adapt to situations as they arise.
Absolutely agree, especially with adapting. I figured I may have been vague and debated whether to CAD it out and post it to give some visuals, but being in the morning and busy, I didn't have time. I may do it in a few minutes so I don't confuse everyone.
While the common description is to say to "drop the hip", my procedure is essentially the same, but my previous explanation may be confusing. The "by the book" method is what I was taught as the "theoretical", the calculations and such. The dropping of the hip is essentially moving your theoretical measurement half the distance of your hip member. This would make the face of the hip line up with your vertical measuring plane, thus when you mark and lay out your hip, the HAP is the same as the commons.
It's a different method with the same results.
The reason I do it this way is so I can have someone on the roof, that may not be as talented as I am, installing the hips in the correct place. My method of laying out the hip places a visual plumb line where the face of the plate is. All they need to do is match the vertical line with the face of the plate.
The method of dropping the hip usually indicates that you are laying out where the corner point of the house is on your hip and dropping the HAP to plane the hips in with the commons. This gives you a vertical layout line for the theoretical and you would have to do either 1) make a few more layout lines so the tard on the roof knows where to put the hip, or 2) assume the tard can figure out where that point is under the hip.
I chose my method because it eliminates a few unnecessary steps in laying out a hip and to try to eliminate the confusion for the guys on the roof. Two lines laid out on a hip and the guys are asking "which line?"