bosun 17th June 2007, 07:13 PM Hello all
Hoping someone can help with me with some advice on the best shelf span for a large inbuilt bookcase . I've googled the forum and had a read of the posts on sag calculations and other ideas etc but still looking.
I'm building a fitted bookcase 2700 high and 3600 long from 280x19 laminated Tassie Oak boards with ply backing and fixed to the wall. Looking at 4 bays of 900 long shelves but not sure if 900 will be too long for sag etc.
ozwinner 17th June 2007, 07:17 PM http://www.woodworkersweb.com/sagulator.htm
Al :)
DJ’s Timber 17th June 2007, 07:18 PM Have a peek here (http://www.woodbin.com/calcs/sagulator.htm), all you have to do is enter the info and it does the rest for you
brian mcmillan 17th June 2007, 07:19 PM i think 900mm should be fine
Just George 17th June 2007, 07:23 PM If you use thicker than 4mm ply backing and screw through this into the
shelves, your sag will be less. Alterntively, you could try bracing each
shelf with a thin strip of the same timber (30x19, for example) as bracing
at the front of each shelf. Try rounding the bottom or the shelf and the
top of each strip to make it obvious they are seperate pieces, this could
be done with a 3mm round over bit or just lightly sanded.
Justin 17th June 2007, 08:10 PM G'day Bosun,
I'm not sure what you mean by laminated boards - do you mean veneered, or have you actually got boards that are produced by gluing up (laminating) multiple thinner pieces ? The reason why I ask is that I understand laminated stock to be more rigid than a single piece of solid, or particleboard or MDF.
If it's particle or MDF, 900mm without any additional bracing or lipping might be a tad long. I made this bookshelf a few years back out of veneered parcticleboard :
http://www.woodworkforums.ubeaut.com.au/showthread.php?t=5942&highlight=finally+finished
Even with solid lipping glued to the front, the 900mm wide section sagged a bit at the back (unlipped) edge, mind you I had a heap of books on those shelves.
So I reckon it depends upon your materials and the type of load you're going to put on the shelves. Myself, I've made a mental note since then to stay away from 900mm spans using P/B, unless something extra is used by way of bracing.
Hope this helps.
Cheers,
Justin.
joe greiner 18th June 2007, 01:19 AM MDF or particle board is crap for shelving. Books are heavy. Long-term creep makes it worse. Solid lips help a little, but should be placed on both edges. Plywood with applied top veneer should be OK for 900mm span, but grain on both the top veneer and the bottom ply should run in the direction of span. Edge banding at the front would be mostly for appearance.
Joe
Chris Parks 18th June 2007, 02:37 AM My shelves are nearly 2 metres long holding massive weight. I used 40mm pine, and supported the back edge with the back panel.
whitewood 18th June 2007, 09:44 AM Bosun
I built 2 shelves above the bench and cook top in my kitchen. I attached 15x15 mm pine to the walls on three sides as the support . The shelves are 30cm deep. I used 32mm Paulownia to span a length of 1.3 metres. My wife promptly filled almost the entire length of one shelf with her cook books. Severals years later there was no saging at all. If Paulownia can span 1.3 metres then Tassi oak should handle your project easily.
bosun 22nd June 2007, 07:48 PM Many thanks to all for the info, advice etc, particularly the real-life examples. I've decided to go with 600 for more stability - all but two rows of shelves can now be adjustable with pin-type shelf supports and I also want the fronts to look "lean and trim" IE without stiffeners along the front.
ps - for Justin : the boards are sold as "laminated" and are made from 95x19 boards glued edge-to-edge to give a 285x19 board. A good way to get nice wide boards. Can also get the same in pine.
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