Terry,
I don't want to get too involved with an explanation 'cause your head will really hurt.
If you find the commom rafter (scale the desired pitch and draw the rafter/s to the ridge) I don't want to get into calcs unless you want to. If you place 2 commom rafters to the ridge, the 3rd common rafter placed from the end of ridge to wall plate shows the end of the hip ridge. Do this for both end walls and you have the ridge length.
Ridge length is = Total building length minus building width. This works regardless of the roof pitch.
For model construction the hip rafters are better figured by measuring after your commons and ridge are positioned. By the time I tell you the pitch: to 17 calcs, you can have the 4 hip rafters cut and installed.
All the jack rafters should be measured and cut the same. Just keep in mind that your rafter centerlines O.C. need to carry for the jacks.
I hope I didn't really confuse you now.
