After you are all done with the plumb cut it should look like the three photos to the right.
Measure and Mark Rafter Length & Tail
Stand the rafter on edge with the crown facing up and hook a tape measure on the long point of the plumb cut and mark the length to the backside of the birds mouth.
Next measure and mark the amount needed for the tail. Now make two 45 degree lines from the center and back up towards the top plumb cut. These will be plumb cuts for the tail.
Now is the time to flip the rafter back on the side and layout the birds mouth. I lay the rafter out with the same stand as a common rafter.
In order for the jack rafters to plane properly we must reduce the stand of the hip. For more on this please see the dropping hip rafters page.
We can now go ahead and with the saw set at 90 degrees cut the birds mouth. The level part of this cut needs to be accurate but I always over cut the backside of the birds mouth (an inch or even two) to allow it to fit the outside corner better
Next is to layout and make the tail cuts with your saw set at a 45 degree angle, as with the top cut one will have to be made from the top and the other from the bottom.
You should also make a level cut high enough that it will not hang below the fascia line.
Tips on Cutting Hip Rafters
Use 17 inches on the body of the framing square and the roof pitch on the tongue.
If the building is out of square all four hips will be different.
You must reduce the stand or the jack rafters will be off.