The "Sagulator" is cool, but...

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.
TIA
dave
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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.
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Alex
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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.
YMMV
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I agree; I'm not gonna worry about the sag since the shelves will be supported in dados and secured to the back as well.
dave
j.duprie wrote:

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