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Old February 11th 20, 07:46 PM posted to rec.woodworking
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Default Wide shelving advice needed

On 2/11/2020 8:39 AM, Scott Lurndal wrote:
whit3rd writes:
On Monday, February 10, 2020 at 3:21:15 PM UTC-8, Ivan Vegvary wrote:
Tearing out sagging shelves in a 10ft. by 6ft. pantry. Would jike to put 18" deep shelves on the back wall. These would not be "cabinet" quality construction.
So, rip 18" wide plywood? Particle board? Bisquit join solid lumber?


Solid is the strongest, and you have the option to put a pretty wood on the leading edge.
Knotty softwood is the inexpensive way to go (vinyl surface
can be applied so the occasional leaky can won't hurt the wood). Biscuits are good.

Plywood
is weaker than solid wood (half the grain runs the wrong way).


Scratching head...



Which actually makes it stronger.



Stronger and dimensionally stable. Much, much, much less likely to
split along the grain.

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Old February 11th 20, 08:21 PM posted to rec.woodworking
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Default Wide shelving advice needed

On Tuesday, February 11, 2020 at 6:39:07 AM UTC-8, Scott Lurndal wrote:
whit3rd writes:


Plywood
is weaker than solid wood (half the grain runs the wrong way).


Which actually makes it stronger.


Tougher, resistant to splitting, yes. Stronger in the shelf-sag sense, no.
Sagulator gets this right.

Shelves need compressive strength in the top surface, and tensile strength
in the bottom surface (knots on top are less troublesome than on bottom, for instance).
Plywood has, on bottom surface, a very thin veneer of good high-tensile strength wood,
backed by a thicker layer with the grain running the wrong way.
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Old February 11th 20, 08:41 PM posted to rec.woodworking
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Default Wide shelving advice needed

On Tue, 11 Feb 2020 12:46:38 -0600, Leon [email protected]
wrote:

On 2/11/2020 8:39 AM, Scott Lurndal wrote:
whit3rd writes:
On Monday, February 10, 2020 at 3:21:15 PM UTC-8, Ivan Vegvary wrote:
Tearing out sagging shelves in a 10ft. by 6ft. pantry. Would jike to put 18" deep shelves on the back wall. These would not be "cabinet" quality construction.
So, rip 18" wide plywood? Particle board? Bisquit join solid lumber?

Solid is the strongest, and you have the option to put a pretty wood on the leading edge.
Knotty softwood is the inexpensive way to go (vinyl surface
can be applied so the occasional leaky can won't hurt the wood). Biscuits are good.

Plywood
is weaker than solid wood (half the grain runs the wrong way).


Scratching head...



Which actually makes it stronger.



Stronger and dimensionally stable. Much, much, much less likely to
split along the grain


Or "cup". I like Baltic plywood - higher ply count - and hardwood
(generally birch) all the way through. More expensive too.

I really like my bifold door shelves. They are a box structure - VERY
stiff. Light weight too. Most of mine are Luan/mahogany faced but
hardboard faced works just as well - they have a cardboard honeycomb
in them to help make them even more rigid.
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Old February 11th 20, 09:14 PM posted to rec.woodworking
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Default Wide shelving advice needed

On Tue, 11 Feb 2020 14:41:14 -0500, Clare Snyder
wrote:

On Tue, 11 Feb 2020 12:46:38 -0600, Leon [email protected]
wrote:

On 2/11/2020 8:39 AM, Scott Lurndal wrote:
whit3rd writes:
On Monday, February 10, 2020 at 3:21:15 PM UTC-8, Ivan Vegvary wrote:
Tearing out sagging shelves in a 10ft. by 6ft. pantry. Would jike to put 18" deep shelves on the back wall. These would not be "cabinet" quality construction.
So, rip 18" wide plywood? Particle board? Bisquit join solid lumber?

Solid is the strongest, and you have the option to put a pretty wood on the leading edge.
Knotty softwood is the inexpensive way to go (vinyl surface
can be applied so the occasional leaky can won't hurt the wood). Biscuits are good.

Plywood
is weaker than solid wood (half the grain runs the wrong way).


Scratching head...



Which actually makes it stronger.



Stronger and dimensionally stable. Much, much, much less likely to
split along the grain


Or "cup". I like Baltic plywood - higher ply count - and hardwood
(generally birch) all the way through. More expensive too.

I really like my bifold door shelves. They are a box structure - VERY
stiff. Light weight too. Most of mine are Luan/mahogany faced but
hardboard faced works just as well - they have a cardboard honeycomb
in them to help make them even more rigid.


Finding a ten foot long door might be a bit pricy though.
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Old February 11th 20, 10:41 PM posted to rec.woodworking
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Posts: 11,470
Default Wide shelving advice needed

On 2/11/2020 1:21 PM, whit3rd wrote:
On Tuesday, February 11, 2020 at 6:39:07 AM UTC-8, Scott Lurndal wrote:
whit3rd writes:


Plywood
is weaker than solid wood (half the grain runs the wrong way).


Which actually makes it stronger.


Tougher, resistant to splitting, yes. Stronger in the shelf-sag sense, no.
Sagulator gets this right.

Shelves need compressive strength in the top surface, and tensile strength
in the bottom surface (knots on top are less troublesome than on bottom, for instance).
Plywood has, on bottom surface, a very thin veneer of good high-tensile strength wood,
backed by a thicker layer with the grain running the wrong way.


Followed by grain running "in the right direction". In fact there is
more "in the right direction" plies then the wrong. If that means anything.

FWIW, with out proper support solid wood will sag also. Solid wood is
OK for short spans.



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Old February 12th 20, 12:45 AM posted to rec.woodworking
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Posts: 891
Default Wide shelving advice needed

On 2/11/2020 3:41 PM, Leon wrote:
On 2/11/2020 1:21 PM, whit3rd wrote:
On Tuesday, February 11, 2020 at 6:39:07 AM UTC-8, Scott Lurndal wrote:
whit3rd writes:


* Plywood
is weaker than solid wood (half the grain runs the wrong way).

Which actually makes it stronger.


Tougher, resistant to splitting, yes.** Stronger in the shelf-sag
sense, no.
Sagulator gets this right.

Shelves need compressive strength in the top surface, and tensile
strength
in the bottom surface (knots on top are less troublesome than on
bottom, for instance).
Plywood has, on bottom surface, a very thin veneer of good
high-tensile strength wood,
* backed by a thicker layer with the grain running the wrong way.


Followed by grain running "in the right direction".* In fact there is
more "in the right direction" plies then the wrong.* If that means
anything.

....

Only that it's somewhat more rigid in the direction of the longitudinal
plies than the other...but it's still less than solid wood longitudinal
of the same species.

From US FPL Handbook Chap 12 on mechanical properties a summary table
shows Doug fir modulus of elasticity as 1.98x10^6 lb/insq whereas
plywood is 1.01-1.24 or only about half. Since difference in deflection
of two pieces of same size and species is only the effect of the
different E as the geometrical factor is the same, the computed sag is
directly proportional to the inverse of the E. IOW, the sag for those
two is almost 2X for ply vis a vis solid of same dimension.

https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_12.pdf

Sagulator gave 0.11" for "Plywood, fir" and while Doug fir wasn't one of
the firs it gives specifically, they all were less (altho not by factor
of 2 which does seem somewhat excessive by common experience). It
doesn't have any other plywood to compare against.


--
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Old February 12th 20, 03:00 AM posted to rec.woodworking
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Posts: 14,199
Default Wide shelving advice needed

On Tuesday, February 11, 2020 at 6:46:01 PM UTC-5, dpb wrote:
On 2/11/2020 3:41 PM, Leon wrote:
On 2/11/2020 1:21 PM, whit3rd wrote:
On Tuesday, February 11, 2020 at 6:39:07 AM UTC-8, Scott Lurndal wrote:
whit3rd writes:

* Plywood
is weaker than solid wood (half the grain runs the wrong way).

Which actually makes it stronger.

Tougher, resistant to splitting, yes.** Stronger in the shelf-sag
sense, no.
Sagulator gets this right.

Shelves need compressive strength in the top surface, and tensile
strength
in the bottom surface (knots on top are less troublesome than on
bottom, for instance).
Plywood has, on bottom surface, a very thin veneer of good
high-tensile strength wood,
* backed by a thicker layer with the grain running the wrong way.


Followed by grain running "in the right direction".* In fact there is
more "in the right direction" plies then the wrong.* If that means
anything.

...

Only that it's somewhat more rigid in the direction of the longitudinal
plies than the other...but it's still less than solid wood longitudinal
of the same species.

From US FPL Handbook Chap 12 on mechanical properties a summary table
shows Doug fir modulus of elasticity as 1.98x10^6 lb/insq whereas
plywood is 1.01-1.24 or only about half. Since difference in deflection
of two pieces of same size and species is only the effect of the
different E as the geometrical factor is the same, the computed sag is
directly proportional to the inverse of the E. IOW, the sag for those
two is almost 2X for ply vis a vis solid of same dimension.

https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_12.pdf

Sagulator gave 0.11" for "Plywood, fir" and while Doug fir wasn't one of
the firs it gives specifically, they all were less (altho not by factor
of 2 which does seem somewhat excessive by common experience). It
doesn't have any other plywood to compare against.



And just about any kind of edging on just about any kind of wood makes
all those specs moot. ;-)






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Old February 12th 20, 03:24 AM posted to rec.woodworking
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Posts: 891
Default Wide shelving advice needed

On 2/11/2020 8:00 PM, DerbyDad03 wrote:
On Tuesday, February 11, 2020 at 6:46:01 PM UTC-5, dpb wrote:
On 2/11/2020 3:41 PM, Leon wrote:
On 2/11/2020 1:21 PM, whit3rd wrote:
On Tuesday, February 11, 2020 at 6:39:07 AM UTC-8, Scott Lurndal wrote:
whit3rd writes:

* Plywood
is weaker than solid wood (half the grain runs the wrong way).

Which actually makes it stronger.

Tougher, resistant to splitting, yes.** Stronger in the shelf-sag
sense, no.
Sagulator gets this right.

Shelves need compressive strength in the top surface, and tensile
strength
in the bottom surface (knots on top are less troublesome than on
bottom, for instance).
Plywood has, on bottom surface, a very thin veneer of good
high-tensile strength wood,
* backed by a thicker layer with the grain running the wrong way.


Followed by grain running "in the right direction".* In fact there is
more "in the right direction" plies then the wrong.* If that means
anything.

...

Only that it's somewhat more rigid in the direction of the longitudinal
plies than the other...but it's still less than solid wood longitudinal
of the same species.

From US FPL Handbook Chap 12 on mechanical properties a summary table
shows Doug fir modulus of elasticity as 1.98x10^6 lb/insq whereas
plywood is 1.01-1.24 or only about half. Since difference in deflection
of two pieces of same size and species is only the effect of the
different E as the geometrical factor is the same, the computed sag is
directly proportional to the inverse of the E. IOW, the sag for those
two is almost 2X for ply vis a vis solid of same dimension.

https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_12.pdf

Sagulator gave 0.11" for "Plywood, fir" and while Doug fir wasn't one of
the firs it gives specifically, they all were less (altho not by factor
of 2 which does seem somewhat excessive by common experience). It
doesn't have any other plywood to compare against.

And just about any kind of edging on just about any kind of wood makes
all those specs moot. ;-)


No, it does not.

All it does is change the geometry somewhat but the effect is also
easily calculated. sagulator has the option to add the edging.

What you can't see in it, unfortunately, is just what data it is using
for the materials properties. I don't recall whether it has the ability
to input the desired properties manually or not.

--
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Old February 12th 20, 03:31 AM posted to rec.woodworking
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Posts: 1,948
Default Wide shelving advice needed

On Tuesday, February 11, 2020 at 1:42:01 PM UTC-8, Leon wrote:
On 2/11/2020 1:21 PM, whit3rd wrote:
On Tuesday, February 11, 2020 at 6:39:07 AM UTC-8, Scott Lurndal wrote:
whit3rd writes:


Plywood
is weaker than solid wood (half the grain runs the wrong way).


Shelves need compressive strength in the top surface, and tensile strength
in the bottom surface (knots on top are less troublesome than on bottom, for instance).
Plywood has, on bottom surface, a very thin veneer of good high-tensile strength wood,
backed by a thicker layer with the grain running the wrong way.


Followed by grain running "in the right direction".


But that inner layer isn't on top (in compression) nor on bottom (in tension)
and its strength is largely wasted. That's why you can often get away with
strong/weak/strong sandwich construction (doors and aircraft panels).

It's also why a bow can be made of a broader stave, and get more power, but
if made of a thicker stave, it snaps in two. Enough stress to cause a bow, applies
very high tensile and compressive strain according to distance from the neutral centerline...
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Old February 12th 20, 04:10 AM posted to rec.woodworking
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Posts: 3,129
Default Wide shelving advice needed

On Tue, 11 Feb 2020 14:14:19 -0600, Markem
wrote:

On Tue, 11 Feb 2020 14:41:14 -0500, Clare Snyder
wrote:

On Tue, 11 Feb 2020 12:46:38 -0600, Leon [email protected]
wrote:

On 2/11/2020 8:39 AM, Scott Lurndal wrote:
whit3rd writes:
On Monday, February 10, 2020 at 3:21:15 PM UTC-8, Ivan Vegvary wrote:
Tearing out sagging shelves in a 10ft. by 6ft. pantry. Would jike to put 18" deep shelves on the back wall. These would not be "cabinet" quality construction.
So, rip 18" wide plywood? Particle board? Bisquit join solid lumber?

Solid is the strongest, and you have the option to put a pretty wood on the leading edge.
Knotty softwood is the inexpensive way to go (vinyl surface
can be applied so the occasional leaky can won't hurt the wood). Biscuits are good.

Plywood
is weaker than solid wood (half the grain runs the wrong way).

Scratching head...



Which actually makes it stronger.



Stronger and dimensionally stable. Much, much, much less likely to
split along the grain


Or "cup". I like Baltic plywood - higher ply count - and hardwood
(generally birch) all the way through. More expensive too.

I really like my bifold door shelves. They are a box structure - VERY
stiff. Light weight too. Most of mine are Luan/mahogany faced but
hardboard faced works just as well - they have a cardboard honeycomb
in them to help make them even more rigid.


Finding a ten foot long door might be a bit pricy though


Make 1 out of 2 short ones - not easy but doable


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