How do I...

[Bruce Volden]

I seen it on NYW a while back and should have written it down

SWMBO is wanting (a promised) book cabinet, floor to ceiling--8' X 5.5"wide X 12" in depth.


I can't figure out how "short" I need to make it so it will stand up and not scar the ceiling. Once it is standing I will have to put in on a base and then attach the crown moulding. HELP is needed by you pro's.


Please---no cut and assemble in place jokes

Bruce

[Jason Beam]

You want the hypotenuse .. 96" tall, 12" wide ... tilting it front-to-back is likely your shortest hyp (unless you really meant 5.5 INCHES like it says... i'm assuming you intended 5.5 feet, though).

Square of 12 + square of 96 = hypotenuse squared - the square root is the hypotenuse.

so - 144 + 9216 = 9360

The sqrt of 9360 is 96.747...

This is all fine and dandy but you've got a fixed hypotenuse and need to find one of the other components of that triangle ... so...

Lemme see if I can do this ...

if the hyp is 96 (let's say 95.5 just to give you half an inch of space under the ceiling), then you square it and subtract 144 (the square of your known depth) - this should leave you the square of the height...

So 95.5^2 = 9120.25

Minus 12^2 (144) = 8976.25

Square root of that is: 94.7430736.

So if you make it 94 3/4" tall, you should have just shy of half an inch of clearance.


I don't know if that's all right ... but it made sense in my head.

[Bruce Volden]

Well I certainly appreciate you catching my error as you are correct.
Width IS 5.5'--not inches (sure would go faster tho').

I knew somebody out here could help. BTW I'm not a total dullard, what with 6 years of high school and all

Once again, I thank you Jason.

Bruce

[Jason Beam]

No, thank you! I would have just cut my first side out and went into the room and tilted it ... shortened it ... tilted it ... shortened it ... until i got to the right height. Thanks to you, I actually thunked it through for once! (Don't mean it's right, tho!)

[Bruce Volden]

Well, I WILL let you know if it's wrong!!

Bruce

[John Schreiber]

Just to confirm Jason's math, I drew a 95 1/2" by 12" rectangle in SketchUp. Drew an arc to show the tilting of the rectangle. Then measured where that arc hit the other vertical line. I got 94.7469".
Tilted Rectangle.jpg

The same as Jason's within 3 thou.

There's more than one way to skin a cat, and I always like to do it two ways just to be sure.

[Bill Keehn]

Put it on a base? It can't be more than 3/4" thick.

If you want to think outside the box you could just build it to 96 inches and put a 2" radius on the top back edge.

However, if you were to scar the ceiling why would you care? Wouldn't it be hidden by the book case? This is a built-in right? You are putting crown around it.