Perhaps a lot more safe than you imagine.
Bending strength is proportional to the square of the thickness.
Deflection is proportional to the cube of the thickness.
Why not just consider it to be the same as "regular" wood at least in the
strong direction? That would be a lot more accurate.
I made a cheapo TV entertainment center, with pine ply. Only want to see
how it holds up thru the years. Also, it would serve me a better idea to
what I really want out of it when I make the next one, with RED OAK. I
have a Sharp 27". The plywood (that the TV is sitting on) is measured as
What I did was use biscuits on the sides (probably three each 2 sides).
The back was straight glued to the back. The front has a 1"x1" (pine).
The real reason I use 1"x1" in the front was to cover the front of the
plywood (those layer lines), but also see if it will support the TV as
well. You are asking the exact same thing on what I did. I made that
thing about 5 years ago and upon reading your remarks, I took a good look
at my thing now, it has NOT sag a bit!
Regarding how I did with the 1"x1" (it is actually 1-5/16", so it may be
a 1-1/2" x 1-1/2"?), I cut 1/2" off (top view), leaving 7/8" for the
front, and 1/2" off (back view), leaving 5/8" for the bottom support (but
really it's the "whole" "L" piece that supports the front). I hope you
understand my English.
The pine plywood was from Home Depot. The next red oak ply will be from
Alpine Plywood. But I might end up getting the red oak ply from HD if the
Alpine Ply is *way* overpriced. The ply will only serve as shelfing, the
rest (largely viewable) will be solid red oak (raised panels).
(Sorry to run on) I am also thinking about using 1/2" ply for the sides
and back only to help with the weight. But a WW professor at my UWM said
it will be same thing, either (with 1/2" or 3/4" ply) both will end up
heavy! He suggests to stick with 3/4", but I don't know yet.
My comment about you plan using dadoes, I would refrain from do that
because it could lead to breakage when moving it around? But thats me
being a "biscuit guy" (even I do use dadoes rarely).
So, to answer your question, YES, it will support it fine!
In fact, I am planning to make the new one this summer (which is why I
was asking about raised panels issues :P ), I am looking to do 36"x24",
to play it "safe" in case I get a 32" TV. I don't want a larger tube TV.
I was also thinking about "what if" I get a HDTV (or whatever is out
there today), it will have to have something different (they are so wide,
You can try the "sagulator" - a calculator for determining wood
deflection. For your dimensions (36x22), red oak sagged .04". They
didn't have oak plywood. Maybe someone can tell us how oak plywood
compares to solid oak strength-wise.
Here's the URL for the calculator:
Well, here's all you would ever want to know... :)
It shows that basically there's only about a 10-20% difference for same
species as compared to ply--somewhat less than I'd have thought. I
skimmed the (somewhat lengthy) report and if I got the gist right, it
concluded for there testing the difference was within the statistical
uncertainty. (Longitudinal to face sheet comparison)
I also found to my surprise that my impression that the laminating had a
significant effect on the transverse bending moment was also mostly in
error--there's an effect, but it's not nearly as large as I had
expected. I suppose my perceptions were flawed owing to the fact that a
4x8 sheet is only half the width in the transverse direction so the
impression apparent strength in that direction is amplified
Duane, from an engineering point of view if you take a xsection of a piece
of plywood and assume the center ply to be the neutral axis [ the axis about
which the plywood bends ] and then consider the plywood sheet as a simple
beam then each of the plies running the same direction as the center ply
will contribute to the bending strength.per the "engineers simple beam
The cross plies will contribute little to the bending strength directly, but
indirectley they separate by varing degrees the contributing plies from
the neutral axis there by acting as webs and allowing the contributing plies
to act as caps . So in my view even though the separation is small some
additional bending strengthis should be added.......mjh
I just wanted to take a moment to thank ALL of you who provided such
good information and opinions on my project. Your advice was very
I modified my cabinet design to include a 3/8" dado for the TV shelf
rather than the 1/4" I had originally intended. I've also added a
vertical cross-section of plywood beneath the rear edge of the shelf.
I further added a vertical shelf support that subdivides the formerly
open large area into two equally sized compartments. The vertical
support should transfer most of the sag to the cabinet floor, and I'll
also add an additional member under the shelf to transfer that load
directly to the floor.
The cabinet went together better than I expected, and I'm down to a few
niggling oops-shouldn't-have-done-that-so-I-hafta-fix-it items, then I
can trim it out and prepare for finish. Inevtiably, I suppose, it's
tending to twist a bit at the top, but I suspect that once it's in
place that won't be as prevalent a problem (I hope). Suggestions for
that welcome, too :)
Thanks again, all.
intrepid firstname.lastname@example.org wrote:
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