WOODWORKING QUIZ for 4 June 04

[Ralph Jones]

Good Evening Friends,
What is the length of the sides for a 12 sided structure with an inscribed diameter of 12'?

Respectfully,

[Bob Willson]

12 divided by 12 = 1

[Pete J]

Hey Ralph

Good question. My answer is 2 7/8 but I am not telling you in which measurement system. Did you know the answer or just asking?

Regards from the sunny country

[Tonz]

3.2154 feet. (or approx 3' 2 9/16")

[Ralph Jones]

Good Evening Friends,
Tonz was the closest to the correct answer as according to my square manual the inscribed diameter of 12' for a 12 sided structure is 3' 2 5/32".

The actual figure in the decimal column is .154 which is a little less than 5/32 so it is OK to round it off to 5/32".

Thank you for your support and I hope at least one person learned something.

Respectfully,

[Bob Willson]

the correct answer as according to my square manual

Thank you for your support and I hope at least one person learned something.

Well, what I learned is that it is a lot easier if you have a book with all the answers in it.

[Ralph Jones]

Good Evening Bob,
I have the book that has the formulas in it but I still have to figure out the answer myself. I am more fortunate than a few as I have had this manual since I was thirteen when I started serving my apprenticeship under my grandfather and he made me to memorize most of the book.

Thank you for your support.

Respectfully,

[Tonz]

This really is basic trigonometry and Ralph I'm afraid your maths is a little flawed.

Dia = 12' therefore Rad = 6'
12 Segments. 360/12 = 30 deg. Divide by 2 to get right angle triangle = 15 deg.

Internal angles for any right angle triangle = 180 deg.
Therefore missing angle = 180 - 90 - 15 = 75 deg

Half length X = 6 / Tan 75 deg = 1.6077'
X 2 for full length = 3.2154'

This equals 3' and 0.2154' which equals 3' and 2.585"
(So the decimal is 0.585" not 0.154" as Ralph states)

0.585" is approx 9/16 as stated previously....

or if you want to get really accurate (and a little pedantic ).
9/16 = .5625"
19/32 = .5938"
37/64 = .5781"
75/128 = .5859"

[Bob Willson]

It looks like Ralph may be the one who has learned something today.