Guys, I use a website called Blocklayer to get allot of my calculators, used it this time to make a twelve sided roof and I must have interpreted something incorrectly.

My settings on the tablesaw were 78.4 on the miter and 23.2 on the bevel which I took to mean from 90 that was 66.8. This did not give me the results I wanted at all instead of a roof from 12 pieces which when joined should produce a lift of 3 23/32" and a spread of 9.? not sure exactly what it was. I was able to get 7 sections to glue together well but produced a roof that was only 5 1/2" across and 6" high. I'm attaching the printout from the website where did I go wrong????

Hey Pat, link us to that calculator if you would. Thanks!

https://www.blocklayer.com/pyramid-calculatoreng.aspx

I think the mistake is in the angle of the blade. The 23.2° is the total angle at the point of the piece. I think the table saw blade angle should have been 20°. The phi angle is defined as the internal angle. My thinking is that you set the internal angle to be 40° so the blade should be set to 20°.

 

I failed algebra in school so take what I'm saying with a very large grain of salt.

Lew, with the way I cut them the angle would need to be drastically less than the 23.2 because the gap was way too open when I had all twelve sections in place.

 

According to Sketchup, the angle is 75° (15°)

 

Edited October 13, 20196 yr by lew

Whenever you make a circle and are using degrees to complete that circle, the degrees have to add up to 360.

Lew is correct, it's 15 degrees, as 15 degrees x 24 sides, is 360 degrees.

I'm dumb. What's the angle for the bottom and sides of each triangle? 

Won’t the narrow sides also have to be angled for a tight fit?

The sides of each roof piece have to be cut at 15 degrees.

15 would be the miter cut, what is the bevel cut?  Is 23.2 correct?

1 hour ago, Cal said:

15 would be the miter cut, what is the bevel cut?  Is 23.2 correct?

Yeah, Cal. My question was a bit confusing. The bevel cut I meant. Thanks. Would it be the same for the bottoms, too?

1 hour ago, Gene Howe said:

Yeah, Cal. My question was a bit confusing. The bevel cut I meant. Thanks. Would it be the same for the bottoms, too?

 

Bottom angle

On my mitre boxes...there IS a setting labelled "12"....as in the angle needed for a 12 sided box...

Muchas gracias, Lew.

 Ok @Pat Meeuwissen, because inquiring mines want to know, Wha'cha building? 

7 hours ago, DuckSoup said:

 Ok @Pat Meeuwissen, because inquiring mines want to know, Wha'cha building? 

Just a silly birdhouse, an exercise in how to do things. Already have the twelve sided body glued up and planned clean.  

10 minutes ago, Pat Meeuwissen said:

Just a silly birdhouse, an exercise in how to do things. Already have the twelve sided body glued up and planned clean.  

How'd the roof cuts go Pat? As planned?

Lew and I are doing a redesign behind the curtain. As soon as we work it out I'll post the results.