whit3rd on Fri, 22 May 2020 11:53:51 -0700 (PDT)
typed in rec.crafts.metalworking the following:
On Thursday, May 21, 2020 at 9:31:09 AM UTC-7, pyotr filipivich wrote:
"Jim Wilkins" on Wed, 20 May 2020 20:55:16
-0400 typed in rec.crafts.metalworking the following:

https://www.woodbin.com/calcs/sagulator/

Neat. Now to find out what the shelves I have are made of, so I
can retro calc their deflection.

{I have some Ikea Billy book cases. The wider shelves have sagged
visibly over the last fifteen years, but I can't just flip the shelves
so that they flatten.

I think you'll find the sagulator only tells Young's modulus sag for flakeboard, it
ignores the long-term moisture induced bowing that you see. That
depends entirely on the glue used (so it's unpredictable). Even the
cheapest white woods are better shelving.

Yep. OTOH, It came in a box, I could put it together without
power tools ... "it worked".
And that is the basic question: how much time and effort is it
worth to DIY, vs buy one in an box vs buy one already made?
--
pyotr filipivich
"With Age comes Wisdom. Although far too often, Age travels alone."