Math Behind Rafter Angles

Because pitch is a right triangle and degree is a segment of a circle.

Take a circle with both vertical and horizontal axes and a radius of 12. For pitch, follow the horizontal axis out to 12, go up square 6, and connect that point to the center. You will see that the hypotenuse crosses the arc at 26 deg. If you go up 5 it crosses at 22.5.

 

Thanks kiteman, I think that helped me visualize it. Here's what I drew based on my understanding of what you said, makes sense.

 

You drew it better than I explained it so I'm going to edit my response.

 

Helps to visualize them. Thanks again kiteman.

 

:thumbsup: IMHO that's a key fundamental visualization-understanding. Roofs stairs and beyond :thumbsup:

See that every time when reaching for/using the "Big 12" (Swanson speed square).

 

Because even a 5000/12 is not quite 90 degrees

 

Because 12/12 is tangent of angle With opposite side 12 and horizontal side 12. 6/12 is tangent of angle with opposite side 6 and horizontal side 12. First ting that will ask God when I will be dead is why I didn't have money to go study electrical engineering. Can not believe where I finish and what I do. Btw how in world OP will compete against me in roof framing or stairs framing?

 

You didn't mention degrees once.

 

Illiterates were cutting roofs and building stairs for generations.

 

Yeah really......just cut it, nail it.....collecting the check is the hard part

 

Two different systems of measuring Angles, one based on Cartesian coordinates(a 12 x 12 grid of squares) the other based on polar coordinates with the Unit circle divided by 360(degrees)...

Or Speed square vs Protractor.....

Next lifetime, don't sleep through elementary school.:whistling

For the advanced students, If I was from Mars, tell me which of my hands is the "right" one without using 'Right'....?

2. Why do clocks go "clockwise"?

 

Two different systems of measuring Angles, one based on Cartesian coordinates(a 12 x 12 grid of squares) the other based on polar coordinates with the Unit circle divided by 360(degrees)...

Or Speed square vs Protractor.....

Next lifetime, don't sleep through elementary school.:whistling

:laughing: The 12x12 method is just a different way to represent an angle, through trig-geometric relationships that define an angle. Just without the soh cah toa, *****' dance.

 

No, he asked why a 6/12 isn't half the degrees of a 12/12

 

12/12 or 6/12 just lets you build it without doing any math calculations at all.

 

220, 230 whatever it takes.

 

220, [STRIKE]230[/STRIKE] whatever it takes.

220, 221 ... what ever it takes. Favorite movie line :thumbsup:


Talking hips, maybe 22, 23 or something in between

 

I give them $150 if I make a sale from their referral.

How about jack's hips?

 

https://www.youtube.com/watch?v=iX3kxAA2L4Q

 

there are numbers and scales on a rafter square????
i thought it was just used to square a corner...


you guys know I am kidding ..right?.......guys..........guys?