Hi all,

I am planning a couple of bookshelves to be made from a 1/2 inch plywood,
35x11 inches in size; some shelves will be fixed in 1/4 inch deep dadoes in
the sides of the bookcase and others will be "floating", supported by pins
inserted in 1/2 inch deep holes. The shelves will only be supported on the
sides; not along the length. Should I worry about the sag of the plywood?
What's a good length of the shelf that can sustain a load full of books
without additional lengthwise support?
Thanks!
Vlad

Yes - you might sag, especially with books. Consider doing both of the
following:

Upsize your shelf to 3/4 plywood - quite a bit stiffer

Trim the front with a piece of oak about 3/4" wide by 1" or 1-1/4" high.
You can route or roll the edges for appearance. It will give you a little
more edge stiffness.



"Vlad" wrote in message
ble.rogers.com...
Hi all,

I am planning a couple of bookshelves to be made from a 1/2 inch plywood,
35x11 inches in size; some shelves will be fixed in 1/4 inch deep dadoes
in
the sides of the bookcase and others will be "floating", supported by pins
inserted in 1/2 inch deep holes. The shelves will only be supported on the
sides; not along the length. Should I worry about the sag of the plywood?
What's a good length of the shelf that can sustain a load full of books
without additional lengthwise support?
Thanks!
Vlad

I would strongly second RonB's comments. A 36" wide shelf that's only 1/2"
thick is bound to sag, especially if not supported along the length. Upgrade
to 3/4" plywood at the very least. Wouldn't be surprised to see even the
3/4" sag if you don't use the oak/hardwood trim piece at the front edge of
the shelf.

If you have access to it, Andy Rae's "The Complete Illustrated Guide to
Furniture & Cabinet Construction" has lots of useful info relevant to what
you're asking about.

"Vlad" wrote in message
ble.rogers.com...
Hi all,

I am planning a couple of bookshelves to be made from a 1/2 inch plywood,
35x11 inches in size; some shelves will be fixed in 1/4 inch deep dadoes
in
the sides of the bookcase and others will be "floating", supported by pins
inserted in 1/2 inch deep holes. The shelves will only be supported on the
sides; not along the length. Should I worry about the sag of the plywood?
What's a good length of the shelf that can sustain a load full of books
without additional lengthwise support?
Thanks!
Vlad

In article . rogers.com,
Vlad wrote:
Hi all,

I am planning a couple of bookshelves to be made from a 1/2 inch plywood,
35x11 inches in size; some shelves will be fixed in 1/4 inch deep dadoes in
the sides of the bookcase and others will be "floating", supported by pins
inserted in 1/2 inch deep holes. The shelves will only be supported on the
sides; not along the length. Should I worry about the sag of the plywood?
What's a good length of the shelf that can sustain a load full of books
without additional lengthwise support?
Thanks!
Vlad



1/2" plywood will sag to much for a 35" wide shelf full of books.
Unless you use 3/4" ply or add some kind of bracing or stiffener, you
probably should keep the length around 12" or so for 1/2" plywood.



--

Larry Wasserman Baltimore, Maryland

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


"Vlad" wrote in message
ble.rogers.com...
: Hi all,
:
: I am planning a couple of bookshelves to be made from a 1/2 inch plywood,
: 35x11 inches in size; some shelves will be fixed in 1/4 inch deep dadoes in
: the sides of the bookcase and others will be "floating", supported by pins
: inserted in 1/2 inch deep holes. The shelves will only be supported on the
: sides; not along the length. Should I worry about the sag of the plywood?
: What's a good length of the shelf that can sustain a load full of books
: without additional lengthwise support?
: Thanks!
: Vlad
:
:

How about an inch wide strip of 3/4 ply supporting the shelves lengthwise
both at the front and at the back of the shelf?
Would this help?
Vlad



"Bob Gramza" wrote in message
om...
http://www.woodbin.com/calcs/sagulator.htm


"Vlad" wrote in message
ble.rogers.com...
: Hi all,
:
: I am planning a couple of bookshelves to be made from a 1/2 inch
plywood,
: 35x11 inches in size; some shelves will be fixed in 1/4 inch deep dadoes
in
: the sides of the bookcase and others will be "floating", supported by
pins
: inserted in 1/2 inch deep holes. The shelves will only be supported on
the
: sides; not along the length. Should I worry about the sag of the
plywood?
: What's a good length of the shelf that can sustain a load full of books
: without additional lengthwise support?
: Thanks!
: Vlad
:
:

"Vlad" wrote in message
ble.rogers.com...


Hi all,

sides; not along the length. Should I worry about the sag of the plywood?

yes. 35" span with books and half-inch ply will most likely sag

What's a good length of the shelf that can sustain a load full of books
without additional lengthwise support?

Depends on the books. How many copies of Lehninger's Principles of
Biochemistry are on them?

I rarely go over 32" with 3/4" plywood. Dunno for 1/2".
(Even 32" and 3/4" will sag some, about 1/32nd to 1/16")

On Thu, 09 Sep 2004 15:24:55 GMT, "Vlad" wrote:

Hi all,

I am planning a couple of bookshelves to be made from a 1/2 inch plywood,
35x11 inches in size; some shelves will be fixed in 1/4 inch deep dadoes in
the sides of the bookcase and others will be "floating", supported by pins
inserted in 1/2 inch deep holes. The shelves will only be supported on the
sides; not along the length. Should I worry about the sag of the plywood?
What's a good length of the shelf that can sustain a load full of books
without additional lengthwise support?
Thanks!
Vlad



A 35" span will require 3/4" ply, plus a 1.5" lip on the front to
prevent sagging. Rabbet the lip and secure with carpenter's glue and
biscuits or finishing nails. If you want super-strong shelves, put a
lip on the back as well as the front. Half inch ply is just not
practical for heavy loads.

On Thu, 09 Sep 2004 15:24:55 GMT, "Vlad" wrote:

Hi all,

I am planning a couple of bookshelves to be made from a 1/2 inch plywood,
35x11 inches in size; some shelves will be fixed in 1/4 inch deep dadoes in
the sides of the bookcase and others will be "floating", supported by pins
inserted in 1/2 inch deep holes. The shelves will only be supported on the
sides; not along the length. Should I worry about the sag of the plywood?
What's a good length of the shelf that can sustain a load full of books
without additional lengthwise support?
Thanks!
Vlad

Your shelf will sag about 0.30 inch over a 35" length. Anything over
..09" would be noticeable, according to the Sagulator:

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

You'll do well to follow the many suggestions to upgrade the shelf
thickness and add stiffener(s).


http://mywebpages.comcast.net/wgoffe...oodworking.htm