I’m framing up a tres ceiling in the stairwell of the burned out rental house job and I was waaaaay too stoned to pay much attention to the maths in high school trig class. It was more fun to throw some bizarre question at Mr. Offenbacker at the start of class and watch him immerse himself in equations on the blackboards ’till the bell rang… both hands chalkin’ up a storm and a floor mop for an eraser heh heh.
So after scribbling circles and lines and triangles and chords on a piece of paper wondering if selling loose joints on the school parking lot was time well spent, 30 seconds on Google yielded http://stardazed.com/octagons.html
Once you know the width of the octagon, the length of each side is
L = 0.4142 W where L is the length of the side.Laying out the octagon. An easy usual way is to first layout an accurate square the same width as the desired octagon, then make marks 0.2929W and 0.7071W in from one side (the side of the octagon takes up 0.4142 of the width of the square, leaving 0.2929W on each side; 0.7071 is 0.2929 + 0.4142)…
As long as I can multiply 66 inches x .2929 with a carpenter’s pencil on a piece of 2×6 I’m okay eh? But then I get 19.3314 inches and I seem to have lost my decimal to inches chart… Lessee 1 divided by 2 is .500, divided by 2 is .250, divided by 2 is .125, divided by 2 is .0625, so .250 and .0625 is .3125
19 5/16ths. Close enough, baby – we’re framin’.
Wow, too early to comprehend, ya lost me in the decimals…..
I’d have just chalked out (on the floor) 2 squares on top of each other, opposite of each other, measure the angle pieces, and use your “speed-square” to find correct angle to cut…besides a round tres ceiling would’ve been waaaay cooler looking!!!!
Hey, good luck….sounds like yer movin’ along.
Those online calculators and such sure are handy. Without ‘em, I’m more of a “cardboard template” kinda guy, heh heh heh…..
.2929 Charlie – I’m going to burn that number into my brain like 3.1414 and the Pythagorean theorum. That and simple ratios
( 1 is to 4 as 2 is to X… 1/4 = 2/X… cross multiply and divide… X = 8 )
covers all the stuff we’ll ever run into.
Nice square trick – bisecting a square both ways gives you the corner points for the square to draw on top of the first one… wa lah! there’s the octagon!
.2929 is easier – I won’t have to clear a spot on the floor….
Lol I was homeschooled and always figured I would learn stuff if and when I needed it. Seems to be working so far
Things like this always seem a lot easier to learn when its actually relevant.
Good on ya, as someone who doesnt pay rent, doesnt buy food and spends my days working on the worlds ills its nice to know there are other people out there thinking along the same lines.
Stumbled across you while looking for info on human powered washing machines. I’ve loved reading through your blog. I’ve got no rent, 7 chickens (just starting out) I cut my light bill in half and I’m working on a rainwater system and composting toilet. It makes me happy to see that there are more people than just little ole me who are working hard to undercut the system that is killing us. I’m looking forward to the day I cut my ties to my deskjob. Thanks for being an inspiration.