Replies

1. 
   dkellernc | Sep 13, 2008 02:28am | #1

   I think what you're after is stiffness (so the shelves won't sag).  Assuming that the shelves will just be flat planks (instead of a more complicated construction like a torsion box), that's going to be a factor of the wood species, and whether the wood is clear and free from knots.

   Believe it or not, Southern Yellow Pine is some of the more stiff material around (and is pretty cheap at the big box stores).  But it has to be clear - knots will weaken it considerably.  If you want hardwood, I'd choose maple.  Still pretty cheap, and pretty stiff.

2. 
   AlanWS | Sep 13, 2008 03:29am | #2

   The way to make a shelf stiffer of any material is to put a deeper edge on the front, and to support the back of the shelf. The thicker the material the stiffer the shelf, and you get much of the advantage of a very stiff shelf, with little of the weight, by making the front edge deep.

   You can get even more of the stiffness with less of the weight by building a torsion box, but that is unlikely to be worth the bother.

   
   

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   Edited 9/12/2008 8:31 pm by AlanWS

3. 
   SteveSchoene | Sep 13, 2008 05:43am | #3

   Here is a very good guide for selecting materials for shelves. 

   http://www.woodbin.com/calcs/sagulator.htm 

   I think you will find a 25" span makes it fairly easy.