Try pulling a string tight between nails at each end of your beams and follow
that with a finger. You will soon discover if there are dips in your beams
hidden by your level.
2 by stock on it's flat face is rarely straight, even on edge they crown,
sometimes substantially.
I don't have any experience with the electronic levels but you might test the
range of accuracy.
Place playing cards under one end until it begins beeping then count how many
you can insert before it again stops. Then you will know the margin of possible
measuring error.
Hope this helps.
----- Original Message -----
From: Dan Rossi
To: Blind Handyman List
Sent: Tuesday, October 20, 2009 10:09 AM
Subject: [BlindHandyMan] Non-euclidian geometry.
I need to call in NASA to investigate my basement. Apparently, my
basement is a very special place where Euclidian geometry goes right out
the window.
I have two parallel beams that are nice and level. The level beeps
continuously as I move it along the beams. I lay a 2X4 across the two
beams and that 2X4 shows level. So, if the two beams are level, and they
are level to each other, then a 2X4 placed across them at any point will
be level.
Here is where it gets interesting. At one end, the 2X4 is level and all
is happy. At the far end, if I level the 2X4 it is well above the one
beam. And I don't mean like a quarter of an inch, I mean like an inch and
a quarter or a bit more.
This is actually impossible. But that is why my basement must be
declared a non-euclidian zone.
I think it has to do with the fact that even if the level is off a tiny
bit, like 0.1 of a degree, over 15 feet, that is actually 5/16 of an inch.
Do that three times and you get nearly an inch. Plus the middle beam that
I was trying to level wasn't fully supported yet, so is bending and
flexing, and so was the 2X4 I was using. Add all that up and you get a
lot of error creep.
I need an 8 foot level, but not sure I can get that one passed SWMBO. I
might try using my saw guide on edge which should be pretty stiff.
--
Blue skies.
Dan Rossi
Carnegie Mellon University.
E-Mail: [email protected]
Tel: (412) 268-9081
[Non-text portions of this message have been removed]
