Replies

1. 
   kingwoodworks | Oct 04, 2006 11:43pm | #1

   One option is to double up on the ply - 2 layers of 3/4" edged by the 1.5" birch might work.  43" is a long span.  I once used an 3/4" x 1.5" solid wood upright centered vertically on a long span and just notched @ each shelf.  Effectively cuts the span in half and still leaves it relatively open. 

   Bob

2. 
   bigfootnampa | Oct 04, 2006 11:57pm | #2

   For heavy books your design is just a bit wimpy for that span.  There are lots of options to beef them up a little.   Stair tread material would be adequate.  You could add a piece of steel tubing below the front of the shelf (behind the shelf facing).  You could use a heavier facing... say 1 1/2 inch X 2 inch (rabbeted for the shelf).  You might add a center brace to the shelf bottoms.  If you can get it you could use 1 inch BB ply I think that would do it too.  I have liked using 6/4 lumber (usually poplar) for such things and then they do not need a facing.

1. 
   quietude | Oct 05, 2006 01:13am | #3

   What do you think of 1 inch baltic birch with 1.5X1.5 birch edging?
   I was planning to tongue and groove it together.
   luke

1. 
   jserena | Oct 05, 2006 01:34am | #4

   While plywood does sag, you did not mention whether the rear and side edges would allow support cleats; I have had success up to 48" x 12" using support cleats, a 3/4 x 1 1/2" solid lumber rabbeted front edge attache with glue & biscuits or dowels; and have even added vertcal plywood ribs horizontally under the center of the shelf when weight requires. I would be sure to use good joinery and a good pva glue.

1. 
   quietude | Oct 05, 2006 01:44am | #5

   I apologize for the lack of details. The intention is to have full length cleats on 3 sides. The Baltic birch would be 1 inch thick with a tongue and groove 1.5inch x1.5inch birch strip along the front. I plan to do my best with the joinery. The shelf is 43 inches wide by 10 inches deep. The load would be just shy of 120 lbs max I believe. (Normal lbs per foot is 20 to 25. Because these are substantial books I am going with 35 lbs/foot)
   luke

   Edited 10/4/2006 6:45 pm ET by quietude

1. 
   BobMc | Oct 05, 2006 08:43am | #9

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

   Per your description, you have plenty of strength.  The URL above gives sag based on the shelf being supported on the ends.  You will greatly increase its load-bearing ability by cleating the rear of the shelf, and the 1.5" hardwood leading edge also adds a lot of strength.

    

2. 
   Ricks503 | Oct 05, 2006 08:12pm | #10

   I was about to post that link as well.

    

   Also a few notes/rules of thumb to stregthen a shelf:

   Make it deeper

   make the span shorter

   Adding a hardwood strip to the edge can increase strength 2-3x

   doubling the thickness can increase strength 4x

   You can add a hardwood strip at the read as well as the front, with it being 2x the thickness of the shelf 

    

   " There'll be no living with her now" - Captain Jack Sparrow

2. 
   bigfootnampa | Oct 05, 2006 02:10am | #6

   I think that will do fine.  Those should hold up plenty of books.

1. 
   quietude | Oct 05, 2006 02:49am | #7

   Thanks for your help.
   luke

3. 
   gb93433 | Oct 05, 2006 07:19am | #8

   One thing I have done on long shelves like yours is to glue a board on the front edge. I usually glue a piece of hardwood which is 3/4" X 1.5" and then have a center support on the back of the cabinet.