I'm building a small wall unit with narrow shelves that will
be attached to the back panel as well as the sides. I doubt
that the "Sagulator"
(http://www.woodbin.com/calcs/sagulator.htm ) takes that into
account. Is there another resource on the web or a way to
figure how much additional support is provided by attaching
a shelf to the rear wall? My shelves are going to be quite
shallow; about 5 1/2". In other words, I'd like to
calculate the "sag" for a shelf that is support on 3 edges.
Intuitive, non-engineer answer: Too many other variables to be able to
answer the question. Some pertinent factors: stiffness of the back,
stiffness of the sides, other shelves (which will tend to stiffen the
sides, making them less able to twist to accommodate a sag of one edge
of the shelf in question). Probably lots of etc's I'm not thinking of.
Make the obvious change in the return address to reply by email.
In general, if a shelf is suported on 3 sides (and I'm working with stock of
any real thickness - say 3/4" or more), I tend not to worry about shelf sag
unless the shelf is really wide.
I have some pine bookcases I built about 30 years ago - they're a full foot
deep, supported on 3 sides (grooves in the plywood back and wood sides),
3/4" stock. they've held my dad's engineering library since they were made
(big, heavy books), and there is a *slight* sag in the middle. Barely
noticable unless you actually sight along the edge.
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