Roof light angles

[comcu]

Hi I was hoping someone could help me.

 

I have a old photocopy of a table finding the angel for a roof light. the table that tells me if the pich of the rafter is 25°, the angle under the hip and the dihedral angle = ....

Eg

Pitch = 25° Angle Under Hip = 18.15 Dihedral Angle = 145.25

Pitch = 20° Angle Under Hip = 14.4 Dihedral Angle = 152

Pitch = 40° Angle Under Hip = 30.7 Dihedral Angle = 125.9

 

Based on this I drew up an basic 3d drawing for the end of roof light. It seems to work. The only angle that it doesn’t give is the cut required on the hip to the rafter connection. From my 3d drawing I can tell the cut needs to be 42°

 

What I would like to be able to do is type the table out in word and add another column to my table that gives me this dimensions for each of the different Pitch Scenarios. I could go and draw them all but this one drawing took me ages as its been a while since i’ve drawn 3d.

I was hoping this is a simple calculation that someone could help me with or point me in the right direction?

 

i have attached a few pictures to to help clarify. You will notice the 3d drawing shows the angle between the hip and the rafter as 42° when dimensioned but 45° when dimensioned in plan.

 

Thanks for any help and taking the time to read

 

cheers.

[SEANT]

Here's a calculator (Excel).

HipRoof.zip

[comcu]

Seant,

 

That is absolutely fantastic!

 

Thank you very much!

[SEANT]

You are welcome. I'm glad it helped.