Roof Cupola

cembich3 · Post by **cembich3** » Sun Sep 23, 2007 4:59 pm

I need some help please! I have e 10 sided house and I want to build a Roof Cupola. What would the angle of my cuts be?

Thanks!;)

dusty · Post by **dusty** » Sun Sep 23, 2007 5:03 pm

I don't have the answer (yet) but I do know that anyone making this calculation needs one more bit of info.

What is the pitch of the roof?

alaskanexile · Post by **alaskanexile** » Sun Sep 23, 2007 5:06 pm

Believe it would be 18 deg to each cut. BUT, am not as confident on this as I would like to be so wait for someone else to verify.
Roger

alaskanexile · Post by **alaskanexile** » Sun Sep 23, 2007 5:09 pm

Roof angle will determine the bottom angle of each piece. Side angles can be determied by segmenting the 360 deg of the compass. Roger

dusty · Post by **dusty** » Sun Sep 23, 2007 5:21 pm

If you have Power Tool Woodworking For Everyone - check out the table on page 37 (Miter Gauge and Table Tilt Settings for Compund Angles). It doesn't have numbers for a ten sided structure but it shows many others.

Also, check out this site: http://www.wwch.org/TechData/CompMiterBevAng.htm

fjimp · Post by **fjimp** » Sun Sep 23, 2007 6:43 pm

My suggestion is not a direct answer to the question yet could prove helpful. While visiting Denver recently I found my GPS had led me to a Rocker Store, which must have been an accident.

While browsing through all of the goodies I found a great little book. Handyman in My Pocket by Richard A. Young and Thomas J. Glover. It is priced at $12.95 and is also available at the Rockler.com website. The contents include more facts and measurements than most of us will ever use. Sequoia Publishing of Littleton Colorado published this tiny jewell. It was originally copyrighted in 2001 and is currently in it's 14 edition. Jim

Ed in Tampa · Post by **Ed in Tampa** » Sun Sep 23, 2007 9:26 pm

The answer is 18 degrees. You divide the number of sides or joints into 360 degrees that gives you 36 and since both boards are beveled you divide 36 by 2 and the answer is 18 degrees.

Or you can go to the site Dusty referenced and look in the chart and find the answer to be 18 degrees.

Either way it is 18 degrees. Roger get the "ata boy" for coming up with the correct answer first.
Ed

reible · Post by **reible** » Sun Sep 23, 2007 11:31 pm

Maybe you do maybe you don't.

If you are talking about the upright structure, a 10 sided box then you have the right answer.

If you want to make the roof then sorry to be the one with the bad news but you do not have the right answer yet. Unless you make a flat roof.... my guess is you will have some sort of slope to deal with and then you have a compound cut and the answer you have will not work.

If this is the case then I'll let you guys work on this for a while and if you can't figure it out I'll be back..... you will have to provide a slope to work with however.

Ed

dusty · Post by **dusty** » Mon Sep 24, 2007 4:12 am

Ed is correct. See post #2.

reible · Post by **reible** » Mon Sep 24, 2007 5:06 am

Hey Dusty I see you're up late too!

I just did a little math and now have a chart with number of sides (3 to 20) and slopes from flat to 90 deg and the corresponding tilt and miter angles.

I then tried to find some place to check it against... after searching about I finally went to the PTWFE (4th edition) and sure enough on page 37 they have a chart. They provide from 3 to 8 sides so I could check a few spots to make sure I didn't mess up...... and I don't think I did. To bad I didn't look at this first I could have made my table look just like it... I have the miter and tilt swapped, I stated with tilt, they started with miter.

Anyway I now have an Excel spreadsheet with the information. Not sure how I'm going to present that here.... I'll have to think about that. Of course if we are not talking a roof then I guess I don't have to worry about it.

Ed

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