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Old January 9th 06, 01:38 AM posted to rec.woodworking
Murray Peterson
 
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Default Best wood for long shelves

I am building a 6 foot long shelf that is going to be supported at the ends
(no option of support in the middle). The shelf needs to support about 50-
70 pounds of weight (stereo equipment), so the "sag" (or deflection) in the
center is going to be a problem. I plan on building the shelf as a hollow
box, and using steel angle iron on the inside as a stiffener.

Just out of curiosity -- what commonly available wood product is best for
resisting deflection under a continuous load (i.e. shelving)? The easily
available ones at my local lumber store a laminated pine, mdf, playwood
and particle board, I am assuming that the laminated pine would be best,
since all the grain is running longitudinally. Is my assumption correct?

--
Murray Peterson

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Old January 9th 06, 02:02 AM posted to rec.woodworking
stoutman
 
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Default Best wood for long shelves

"Murray Peterson" wrote in message
...
I am building a 6 foot long shelf that is going to be supported at the ends
(no option of support in the middle). The shelf needs to support about
50-
70 pounds of weight (stereo equipment), so the "sag" (or deflection) in
the
center is going to be a problem. I plan on building the shelf as a hollow
box, and using steel angle iron on the inside as a stiffener.

Just out of curiosity -- what commonly available wood product is best for
resisting deflection under a continuous load (i.e. shelving)? The easily
available ones at my local lumber store a laminated pine, mdf, playwood
and particle board, I am assuming that the laminated pine would be best,
since all the grain is running longitudinally. Is my assumption correct?

--
Murray Peterson


Check out the sagulator shelf deflection calculator. Might be useful.
http://www.woodbin.com/calcs/sagulator.htm

--
Stoutman
http://home.triad.rr.com/brianmeliss...ing_frames.htm
(Featuring a NEW look)


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Old January 9th 06, 02:03 AM posted to rec.woodworking
Joe Barta
 
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Default Best wood for long shelves

Murray Peterson wrote:

I am building a 6 foot long shelf that is going to be supported at
the ends (no option of support in the middle). The shelf needs to
support about 50- 70 pounds of weight (stereo equipment), so the
"sag" (or deflection) in the center is going to be a problem. I
plan on building the shelf as a hollow box, and using steel angle
iron on the inside as a stiffener.

Just out of curiosity -- what commonly available wood product is
best for resisting deflection under a continuous load (i.e.
shelving)? The easily available ones at my local lumber store
a laminated pine, mdf, playwood and particle board, I am
assuming that the laminated pine would be best, since all the
grain is running longitudinally. Is my assumption correct?


You could make the shelves a torsion box. Think hollow core door.
Lightweight and very strong. 1/4" ply top and bottom, hardwood edging
and pine innards. No steel needed.

Joe Barta
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Old January 9th 06, 02:08 AM posted to rec.woodworking
todd
 
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Default Best wood for long shelves

"Murray Peterson" wrote in message
...
I am building a 6 foot long shelf that is going to be supported at the

ends
(no option of support in the middle). The shelf needs to support about

50-
70 pounds of weight (stereo equipment), so the "sag" (or deflection) in

the
center is going to be a problem. I plan on building the shelf as a hollow
box, and using steel angle iron on the inside as a stiffener.

Just out of curiosity -- what commonly available wood product is best for
resisting deflection under a continuous load (i.e. shelving)? The easily
available ones at my local lumber store a laminated pine, mdf, playwood
and particle board, I am assuming that the laminated pine would be best,
since all the grain is running longitudinally. Is my assumption correct?

--
Murray Peterson


For the sheet goods, on average, plywood would be the best, then particle
board, then MDF for initial sag.

I'm a bit unclear on how you're going to build the shelf as a hollow box.
If you're going to go to that much trouble, and then include a steel angle,
I'd suggest just doubling up on the wood for the shelf. Two of the 3/4"
glued-up pine boards would deflect only about 3/32 at the middle under a
distributed 70 pound load (assuming a shelf depth of 12").

You can get an estimate of sag using the Sagulator at
http://www.woodworkersweb.com/sagulator.htm.

todd


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Old January 9th 06, 02:10 AM posted to rec.woodworking
Lew Hodgett
 
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Default Best wood for long shelves

Murray Peterson wrote:
I am building a 6 foot long shelf that is going to be supported at the ends
(no option of support in the middle). The shelf needs to support about 50-
70 pounds of weight (stereo equipment), so the "sag" (or deflection) in the
center is going to be a problem. I plan on building the shelf as a hollow
box, and using steel angle iron on the inside as a stiffener.

Just out of curiosity -- what commonly available wood product is best for
resisting deflection under a continuous load (i.e. shelving)? The easily
available ones at my local lumber store a laminated pine, mdf, playwood
and particle board, I am assuming that the laminated pine would be best,
since all the grain is running longitudinally. Is my assumption correct?



If you are interested, can tell you how to build this shelf using foam,
knitted fiber glass and epoxy along with the basic wooden shelf that is
say 3/4" thick.

It would probably support at leat 200 lbs, weigh maybe 10 lbs max.

Contact me off list if interested.

Lew


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Old January 9th 06, 02:30 AM posted to rec.woodworking
Murray Peterson
 
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Default Best wood for long shelves

"todd" wrote in
:

For the sheet goods, on average, plywood would be the best, then
particle board, then MDF for initial sag.

I'm a bit unclear on how you're going to build the shelf as a hollow
box. If you're going to go to that much trouble, and then include a
steel angle, I'd suggest just doubling up on the wood for the shelf.
Two of the 3/4" glued-up pine boards would deflect only about 3/32 at
the middle under a distributed 70 pound load (assuming a shelf depth
of 12").

You can get an estimate of sag using the Sagulator at
http://www.woodworkersweb.com/sagulator.htm.


Are the sagulator numbers good for long-term loading, or just initial
deflection? My experience with purchased bookshelves has been poor --
shelves that progressively sag more as the years go by.

BTW, the loading is not distributed -- almost all of the weight is pretty
close to centered.

--
Murray Peterson

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Old January 9th 06, 02:33 AM posted to rec.woodworking
Murray Peterson
 
Posts: n/a
Default Best wood for long shelves

Joe Barta wrote in news:[email protected]
207.115.17.102:

You could make the shelves a torsion box. Think hollow core door.
Lightweight and very strong. 1/4" ply top and bottom, hardwood edging
and pine innards. No steel needed.


That's pretty much what I had in mind, but with some 1/2 inch steel angle-
iron screwed to the inside of the front and back edges for increased
stiffness. Sounds like my design may be overkill for the application.

--
Murray Peterson

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Old January 9th 06, 02:47 AM posted to rec.woodworking
stoutman
 
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Default Best wood for long shelves

"Murray Peterson" wrote in message
...
"todd" wrote in
:

For the sheet goods, on average, plywood would be the best, then
particle board, then MDF for initial sag.

I'm a bit unclear on how you're going to build the shelf as a hollow
box. If you're going to go to that much trouble, and then include a
steel angle, I'd suggest just doubling up on the wood for the shelf.
Two of the 3/4" glued-up pine boards would deflect only about 3/32 at
the middle under a distributed 70 pound load (assuming a shelf depth
of 12").

You can get an estimate of sag using the Sagulator at
http://www.woodworkersweb.com/sagulator.htm.


Are the sagulator numbers good for long-term loading, or just initial
deflection? My experience with purchased bookshelves has been poor --
shelves that progressively sag more as the years go by.

BTW, the loading is not distributed -- almost all of the weight is pretty
close to centered.

--
Murray Peterson


From the sagulator: "The Sagulator computes initial sag only. As an
engineering rule of thumb, wood beams/shelves will sag an additional 50%
over time beyond the initial deflection induced by the load."

--
Stoutman
http://home.triad.rr.com/brianmeliss...ing_frames.htm
(Featuring a NEW look)


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Old January 9th 06, 03:08 AM posted to rec.woodworking
Joe Barta
 
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Default Best wood for long shelves

Murray Peterson wrote:

Joe Barta wrote in
news:[email protected] 207.115.17.102:

You could make the shelves a torsion box. Think hollow core door.
Lightweight and very strong. 1/4" ply top and bottom, hardwood
edging and pine innards. No steel needed.


That's pretty much what I had in mind, but with some 1/2 inch
steel angle- iron screwed to the inside of the front and back
edges for increased stiffness. Sounds like my design may be
overkill for the application.


Over 6 feet, 1/2" steel angle ain't gonna do squat. You'd get far more
bang for your buck increasing the thickness of the torsion box.
  #10   Report Post  
Old January 9th 06, 03:16 AM posted to rec.woodworking
Joe Barta
 
Posts: n/a
Default Best wood for long shelves

Murray Peterson wrote:

"todd" wrote in
:

For the sheet goods, on average, plywood would be the best, then
particle board, then MDF for initial sag.

I'm a bit unclear on how you're going to build the shelf as a
hollow box. If you're going to go to that much trouble, and then
include a steel angle, I'd suggest just doubling up on the wood
for the shelf. Two of the 3/4" glued-up pine boards would deflect
only about 3/32 at the middle under a distributed 70 pound load
(assuming a shelf depth of 12").

You can get an estimate of sag using the Sagulator at
http://www.woodworkersweb.com/sagulator.htm.


Are the sagulator numbers good for long-term loading, or just
initial deflection? My experience with purchased bookshelves has
been poor -- shelves that progressively sag more as the years go
by.

BTW, the loading is not distributed -- almost all of the weight is
pretty close to centered.


I'm no engineer... more of a shoot from the hip from experience type.
I think a torsion box with 1/4" glued on ply top and bottom with a
total thickness of 1-3/4" should be strong enough for even the
heaviest stereo equipment.

I think the "sagulator" is just a guide and it has no use in
calculating the strength of engineered assemblies... which is what a
torsion box would be.

Joe Barta


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