Hip angle formula

[Aussie John]

heres a q for the maths gurus.

for any given roof of pitch "roof_ang" what is the formula for calculating the angle of an element placed oblique the fall line of the roof ("obj_ang")

eg at the hip - "obj_ang" would be 45. (if roof pitches are equal)

thanks

[Rod Jurich]

Aussie wrote:
/....
for any given roof of pitch "roof_ang" what is the formula for calculating the angle of an element placed oblique the fall line of the roof ("obj_ang")

eg at the hip - "obj_ang" would be 45. (if roof pitches are equal)

I'm no guru, John, but is this what you want?
If so the maths is in the part here.

[Aussie John]

Rod wrote:
I'm no guru, John, but is this what you want?
If so the maths is in the part here.

Rod- Ill have a closer look at your library part. What i am hoping to do is be able to place a capping as a roof accessory and by varying the 2d angle in plan get an automatic correction the the inclined angle.

[Anonymous]

Aussie wrote:
heres a q for the maths gurus.

for any given roof of pitch "roof_ang" what is the formula for calculating the angle of an element placed oblique the fall line of the roof ("obj_ang")

eg at the hip - "obj_ang" would be 45. (if roof pitches are equal)

thanks

I don't know if it helps but I find it much quicker to cut a section through and measure the angle rather than getting into maths. Let the computer do the maths - that's what it's for!

If you need the formula for scripting an object for instance then I'm sorry - this advice is useless!

[Aussie John]

I think I have worked it out.
angle of hip =ATN(tan(AC_pitch)*cos(angleofobject))
for a normal hip angleofobject is 45
and AC_pitch is the angle of roof to which the accessory is applied

[gpowless]

In terms of carpentry, the hip slope is always (pitch)/18 when the main pitch is expressed in (pitch)/12.

[Anonymous]

gpowless wrote:
In terms of carpentry, the hip slope is always (pitch)/18 when the main pitch is expressed in (pitch)/12.

Thats not correct, its 17 not 18. For example, a 4"/12" roof pitch has a 4"/17" hip/valley pitch.

But here is a good cheater calculator. http://www.ls.net/~windyhill/Calcs/hipbackangle3.htm

Jim