Baltic Birch is a hardwood ply from Russia in the first place.
If it is true and only Birch it is tough.

It all depends on what you put on it. I built 40+ book cases for this
house and limited shelf length. Only on one shelf - that of paperbacks
those are longer like you say - It is build out of 3/4" pine and is 46".
It has been loaded with paperbacks and small books for 6 years. Not a
bend. All of the others are 30" or less. We have just about 4000
books so books are our things. Kinda depends on what is put in them!

We use 30" shelves for DVD's and Tapes. More than ample.

Martin


On 12/4/2010 2:45 PM, J. Clarke wrote:
In .185.250,
says...

My son wants a no-frame bookcase 14" x 39.5" x 52.75" from either 5/8" 11
ply Baltic Birch Plywood or 3/4" 13 ply Baltic Birch Plywood. Will 5/8"
really hold up? I have my doubts.

Run the sagulator on ithttp://www.woodbin.com/calcs/sagulator.htm.

You'll find that the shelves need some reinforcement--if they are
attached to the back that should do it, if they're removable they need a
reinforcing strip--you can play with the dimensions in the sagulator.

Note that the sagulator doesn't list birch ply, just fir--use those
numbers and you'll have good margins.