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Forum topic by xvimbi posted 02-12-2016 05:10 AM 630 views 0 times favorited 21 replies Add to Favorites Watch
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xvimbi

4 posts in 303 days


02-12-2016 05:10 AM

Hi,

Long-time lurker, first-time poster here.

I need opinions on the feasibility of the following bookcase project: I am planning on creating a bookcase with a back and a side panel. Just one side panel. The shelves would be joined to the back and the side with dados. The back and side would be made from 3/4” plywood, the shelf boards would be made from 1” thick bamboo stair treads. Shelf board dimensions would be 11”x34”. That whole assembly would then be mounted intto a corner of a wall with the side panel and the back of the bookcase screwed through the drywall into studs.

My question is, would the shelves be stable in the long run? I am planning on putting regular things on them, books & stuff. I am concerned that stabilizing the boards only at the back and one side might not be enough, but I also can’t imagine these 1” boards sagging or going anywhere. They are very heavy and quite solid. Of course, I could attach vertical dividers between two shelf boards to stiffen the assembly, perhaps at the 20” mark, but I am trying to avoid that.

Hope that description is clear.

Any opinions?

Many thanks in advance!


21 replies so far

View bbasiaga's profile

bbasiaga

759 posts in 1463 days


#1 posted 02-12-2016 01:47 PM

Hm, at 1” thick I don’t think your shelves will sag ( you can go to sagulator on the internet to find out), but they might deflect (angle down while staying in plane) towards that outside corner.

I suppose you could try it, and if It got too bad you could put a small upright between each shelf right at the outside edge. It would also then act as a book end to prevent you from pushing stuff off the open end.

-Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View ThomasChippendale's profile

ThomasChippendale

244 posts in 400 days


#2 posted 02-12-2016 02:08 PM

There are selection tables on materials VS spans for bookshelves better than this one :

http://www.diyadvice.com/diy/built-ins/materials-and-hardware/sagless-spans/

I have built my bookshelves using 3/4 maple plywood that are not tied to the back but only at the ends. The 24 inches shelves stay dead straight but I have two that are 44 inches long and 6 inches wide and they sag if I fill them with books.

-- PJ

View Cooler's profile

Cooler

277 posts in 311 days


#3 posted 02-12-2016 02:20 PM

If I understand this correctly you are supporting one end and the back of each shelf.

If you are loading it with books I would be concerned.

How about a thing black dowel in the unsupported end? It will nearly disappear visually and it will offer substantial support in the corner.

Or an even thinner steel rod painted black.

-- This post is a hand-crafted natural product. Slight variations in spelling and grammar should not be viewed as flaws or defects, but rather as an integral characteristic of the creative process.

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xvimbi

4 posts in 303 days


#4 posted 02-12-2016 02:33 PM

Thanks so much so far.

I am familiar with Sagulator and similar, but my situation isn’t really covered properly.

And indeed, I am not so much concerned about sag as I am concerned about weight placed on the unsupported shelf corners potentially causing high torque in the dados, eventually damaging the entire assembly.

I’d like to avoid having to obstruct the unsupported corners unless necessary for stability reasons. I guess I will simply try it out and see how it goes. It will probably be necessary to keep an eye on it long-term, which would be somewhat of a nuisance.

I just want to get a sense for whether potential failure would be gradual or sudden. It won’t be fun to see these boards come crashing down…

View bbasiaga's profile

bbasiaga

759 posts in 1463 days


#5 posted 02-12-2016 02:42 PM

Can you work your length out so that the end of the shelf corresponds to a stud? You could then maybe pocket hole a long screw in the underside of the shelf, through the back, and into the stud. That would help support the dado. You could also glue a 3/4” thick support under each shelf to support the shelf at the dado, making failure there less likely. The shelf may still deflect at the outside corner under load though.

Just thinking out loud…

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View Tony1212's profile

Tony1212

111 posts in 1202 days


#6 posted 02-12-2016 03:22 PM

This is just begging for a Matthias Wandel hydraulic jack and bathroom scale type experiment. (I’ve been watching those videos lately – quite interesting)

Here's an example.

Just make a single shelf version of what you are planning to make and put the jack on the outside corner. That will give you all the info you need. Be sure to post back because I’m very curious to see how it turns out.

-- Tony, SW Chicago Suburbs

View jbay's profile

jbay

820 posts in 367 days


#7 posted 02-12-2016 03:48 PM

Looks strong enough to me.
Obviously won’t hold the girl, but as long as you don’t overload it I think it would be fine.
An idea to clip the corners so the sharp square corner is not present.

-- My “MO” involves Judging others, playing God, acting as LJs law enforcement, and never admitting any of my ideas could possibly be wrong or anyone else's idea could possibly be correct -- (A1Jim)

View xvimbi's profile

xvimbi

4 posts in 303 days


#8 posted 02-12-2016 03:49 PM



Can you work your length out so that the end of the shelf corresponds to a stud? You could then maybe pocket hole a long screw in the underside of the shelf, through the back, and into the stud. That would help support the dado. You could also glue a 3/4” thick support under each shelf to support the shelf at the dado, making failure there less likely. The shelf may still deflect at the outside corner under load though.

Just thinking out loud…
- bbasiaga


Good suggestions. Yes, the outside edge is close to a stud. Also, using a dado that doesn’t span the entire width of the board (like tongue and groove) might give the shelf some additional support indeed

View jbay's profile

jbay

820 posts in 367 days


#9 posted 02-12-2016 03:52 PM

Good suggestions. Yes, the outside edge is close to a stud. Also, using a dado that doesn t span the entire width of the board (like tongue and groove) might give the shelf some additional support indeed

- xvimbi

Full length dado glued and screwed is all you need. The shelf won’t pull out of it.
I would make the dado about 3/16” deep so that you have more meat to screw through.

-- My “MO” involves Judging others, playing God, acting as LJs law enforcement, and never admitting any of my ideas could possibly be wrong or anyone else's idea could possibly be correct -- (A1Jim)

View MNgary's profile

MNgary

296 posts in 1885 days


#10 posted 02-12-2016 04:02 PM

I would try using 9-1/2 inch deep floating shelves. To float: a) drill 3/8 inch hole 5 – 6 inches deep into back edge of shelves every 12 inches, b) cut off a 1 inch slice from back of shelf, c) cut 3/8 inch deep dado for the shelves to fit in into back plywood panel, d) glue and screw slice into dado, e) drill through back panel ising holes from a) as pattern, f) insert dowels extending from outside of back panel and long enough to almost reach bottom of shelf hole and glue assembly. I.e., glue entire length of dowels and back edge of shelf.

-- I dream of the world where a duck can cross the road and no one asks why.

View jbay's profile

jbay

820 posts in 367 days


#11 posted 02-12-2016 04:29 PM

I’ve floated a few shelves in my time. Notice the shelves on each side of the TV. Pretty much the same thing you are doing.
The shelves aren’t going to give way at the back or side. Any sagging will be from the stability of the 1” shelf.

If I were worried about it I would inset a 6 or 8” L Bracket into the back and into the bottom of the shelf, then cover it with veneer or a plug made from the bamboo.

-- My “MO” involves Judging others, playing God, acting as LJs law enforcement, and never admitting any of my ideas could possibly be wrong or anyone else's idea could possibly be correct -- (A1Jim)

View pintodeluxe's profile

pintodeluxe

4859 posts in 2281 days


#12 posted 02-12-2016 04:39 PM

No way I would trust a shallow dado to carry the load. Most floating shelf designs have some hidden structure that makes it possible.

Here’s an idea… Run a natural piece of bamboo vertically through the shelves as additional support. It only works with certain styles, but it would give you the open shelves you are after.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View jbay's profile

jbay

820 posts in 367 days


#13 posted 02-12-2016 04:54 PM

No way I would trust a shallow dado to carry the load. Most floating shelf designs have some hidden structure that makes it possible.

Here s an idea… Run a natural piece of bamboo vertically through the shelves as additional support. It only works with certain styles, but it would give you the open shelves you are after.

- pintodeluxe

Why? What is going to break?
You only talking 3 ft of shelf. No way it would “snap off” the edge of the dado.

Edit: I just did a small mach up of a shelf that has an 1/8” dado. I weigh 185 lbs.
Shelf was solid as far as the dado goes. (Glue still wet as well.)

-- My “MO” involves Judging others, playing God, acting as LJs law enforcement, and never admitting any of my ideas could possibly be wrong or anyone else's idea could possibly be correct -- (A1Jim)

View MrFid's profile

MrFid

805 posts in 1372 days


#14 posted 02-12-2016 04:57 PM

I like jbay’s suggestion of a hidden support. You could even cut a recess in the back (non-show side) of the back piece, with a mortise through the back that would allow a piece of angled steel (or whatever) in the alignment shown in his diagram, but you wouldn’t need the veneer or plug suggested, as it would be behind the show face of the back. Not sure if you have the metalworking capacity to bend a piece of metal to that shape, but maybe you can find something that will suit your purposes. I’d say his (jbay’s) was the best idea so far.

EDIT: Awesome work, jbay, by the way. Beautiful.

-- Bailey F - Eastern Mass.

View jbay's profile

jbay

820 posts in 367 days


#15 posted 02-12-2016 05:13 PM



I like jbay s suggestion of a hidden support. You could even cut a recess in the back (non-show side) of the back piece, with a mortise through the back that would allow a piece of angled steel (or whatever) in the alignment shown in his diagram, but you wouldn t need the veneer or plug suggested, as it would be behind the show face of the back. Not sure if you have the metalworking capacity to bend a piece of metal to that shape, but maybe you can find something that will suit your purposes. I d say his (jbay s) was the best idea so far.

EDIT: Awesome work, jbay, by the way. Beautiful.

- MrFid

Thanks MrFid,

The bracket is actually set in from the back. Sketchup, in xray view, it’s hard to tell. My suggestion for the plug or veneer would be for the bottom of the shelf.

-- My “MO” involves Judging others, playing God, acting as LJs law enforcement, and never admitting any of my ideas could possibly be wrong or anyone else's idea could possibly be correct -- (A1Jim)

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