I am planning some built-in bookcases in a location where load-bearing is an issue. They will consist of three or four cases containing a half-dozen fixed shelves. They will be painted.
Although I would normally consider MDF for this, I’m leaning toward birch plywood because it’s lighter in weight. Now I’m trying to figure out whether to fill the space with four bookcases made of 1/2-inch ply (shorter spans–thus the extra case) or a three-case unit made of 3/4-inch ply with longer spans. Anyone have any tips on how best to calculate which would weigh less?
Norman
Replies
It would seem to me that solid wood will be your best bet, being the lightest choice for a given thickness. That said, the weight of the books on those shelves will be a far more significant factor, rendering the weight of the shelves themselves immaterial. If you have support problems with the shelves themselves, you might want to rethink this.
Mike Hennessy
Pittsburgh, PA
Mike, you're right, of course, that the materials of the bookcase itself will be minor compared to the weight of the books. I should really make sure the scale of the shelves fully loaded is appropriate for that space.Thanks for getting me refocused on the real issue. Sometimes I get so lost in the design of a thing that I forget about the obvious!Norman
Norman:
You can go to http://www.woodbin.com/calcs/sagulator.htm and they have a free applet that calculates the amount of sag in bookcase shelves based on wood type, thicknesses, length of shelves and weight to be supported. It also does the calculation for MDF and plywood.
Jim
Norman,
There is an article in the June issue of W-Worker Journ-l about using Torsion Boxes as shelves. Interesting. They look very strong. Building a box is a lot more work than cutting a shelf from a sheet of plywood but depending on circumstances it may be worthwhile.
Good luck, GeorgeYou don't stop laughing because you grow old. You grow old because you stop laughing. - Michael Pritchard<!----><!----><!---->
<!----><!---->
Want light? Look for some spruce. Just a thought. When my students design anything they want to be able to carry, we almost always end up using spuce. Sitka, I think.
This forum post is now archived. Commenting has been disabled