Optimum spacing between shelf supports

What's the best distance to have between the two brackets of a shelf? It's going to hold books, and I don't want it to bow in the middle (or anywhere else).
Is it better to have the brackets at 1/3 and 2/3 distance along the shelf, or 1/4 and 3/4 distance? Or is the optimum figure somewhere in between?
Daniele
--
Apple Juice Ltd
Chapter Arts Centre
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D.M. Procida wrote:

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Steve R

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On Mon, 28 Jul 2003 09:43:47 UTC, @apple-juice.co.uk (D.M. Procida) wrote:

If it's evenly loaded, surely the brackets (if only 2) should be at 0.25 and 0.75 of the length...
--
Bob Eager
rde at tavi.co.uk
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I'd go for three, the outer ones about 150mm in from the ends. Books can weigh rather a lot.
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*I never drink anything stronger than gin before breakfast *

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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It's also worth considering a construction for the shelf that is stronger than just a plank rested between brackets. You can "beef up" a shelf considerably by screwing and glueing a batten along the under side of the shelf. For many bookcases it's standard to support the back edge of the shelf using a batten screwed to the back of the bookcase. If that isn't possible in this case then simply screwing a batten along the length of the shelf at half the width can dramatically increase the load-bearing ability of the shelf.
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which would be called `A Live Celebrity Gets Eaten by a Shark'."
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Yes. You used to get a one piece 'bracket' that ran the length of the shelf which was fixed to the wall by screws concealed behind the shelf, and the shelf was simply tapped into it. I've got these here in this room - loaded with books and no sagging - and looks very good too. But I've not seen them recently, although I can't say I've looked.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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Depends on what the shelf's made of. MDF is very bendy unless its really thick. Needs a bracket at least every 3 feet. I usually just guess the number of backets depending on the material/weight/length. You want each bracket to support an equal amount of shelf so for 2 brackets space them at 1/4 and 3/4. For 4, at 1/8, 3/8, 5/8, 7/8.
cheers Bax
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Not much of an engineer. The spaces are then 'equal' 3rds, with two of them unsupported at one end...
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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