George:
I never saw your reply below, to my comments until I did a google search on
the thread. For some reason, my ISP dropped some of the posts from that
thread - maybe from other threads for all I know. I've pasted in my last
comments and your reply to them below and will insert my current comments
within.
George said...
> > You are incorrect. The fibers will expand and contract when the
moisture
> > gets to them, and at the same rate, less compression set. You may slow
> the
> > arrival with occlusive finishes, but wood loves water and will find a
way
.
>> This does not make sense George.
> It does to wood technologists. RH correlates directly to moisture
content.
Yes it does and that simple corelation makes sense to everyone, not just to
wood technologists. The reason I say it makes not sense is that your
statement above does not take into consideration the constraint placed on
the tenon by the mortise. I completely ignores the mechanical principle at
work in this joint.
>> Wood fibers that are constrained can only
>> absorb water to the point that they equal the force placed on them by the
>> joint. At that point they effectively reach their saturation level.
Wood
>> does not continue to obsorb moisture until it reaches the point that its
>> moisture content is equal to the surrounding air, it absorbs it to a
>> maximum
>> it can hold and that maximum is limited by the cell's ability to contain
>> that moisture. Constrain those cells and they are capable of holding
less
>> moisture.
> Incorrect again. The fibers adsorb moisture at the molecular level,
binding
> to the cellulose. There is a lot of air left inside any board, indeed,
> inside the cells themselves, which spaces are shrunken by the inexorable
> gathering of moisture, though they do compression set - they don't return
to
> full expansion - which condition exacerbates the one caused by shrinkage
of
> the fibers themselves once the wood begins to seek EMC with lower RH.
No - very correct. Whether the fibers absorb moisture at the molecular
level (not true), or at any other level, they can only absorb as much as
they are allowed to hold by the mechanical constraintes placed on them. A
tight joint will not absorb as much moisture as a plank laid out in the same
high RH environment. What you say above about absorbing moisture and
releasing it above is otherwise true, but it does not address the mechanical
constraint. Nor does the article.
> Wonderful, well-documented stuff here
> http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm to read.
> Start with chapters 2 and 3.
Yes - excellent documentation, and thanks for the link. But... it does not
really point out anything that has not been already accepted and understood
throughout this conversation, and it does not deal at all with the exception
I am talking about which is a mechanically constrained joint.
--
-Mike-
[email protected]
"Mike Marlow" <[email protected]> wrote in message
news:[email protected]...
> George:
>
> I never saw your reply below, to my comments until I did a google search
on
> the thread. For some reason, my ISP dropped some of the posts from that
> thread - maybe from other threads for all I know. I've pasted in my last
> comments and your reply to them below and will insert my current comments
> within.
> No - very correct. Whether the fibers absorb moisture at the molecular
> level (not true), or at any other level, they can only absorb as much as
> they are allowed to hold by the mechanical constraintes placed on them. A
> tight joint will not absorb as much moisture as a plank laid out in the
same
> high RH environment. What you say above about absorbing moisture and
> releasing it above is otherwise true, but it does not address the
mechanical
> constraint. Nor does the article.
>
Sorry, but until water is no longer influence-bonded to the cellulose (read
FSP), and until you squeeze all the air out by collapsing the cells and
tracheids completely, you are incorrect. Since both are not possible...
draw your own conclusions.
> > Wonderful, well-documented stuff here
>
> > http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm to
read.
> > Start with chapters 2 and 3.
>
> Yes - excellent documentation, and thanks for the link. But... it does
not
> really point out anything that has not been already accepted and
understood
> throughout this conversation, and it does not deal at all with the
exception
> I am talking about which is a mechanically constrained joint.
>
"Mike Marlow" <[email protected]> wrote in message
news:[email protected]...
>
> "George" <george@least> wrote in message
> news:[email protected]...
> >
> > "Mike Marlow" <[email protected]> wrote in message
> > news:[email protected]...
> > > George:
> > >
> > > I never saw your reply below, to my comments until I did a google
search
> > on
> > > the thread. For some reason, my ISP dropped some of the posts from
that
> > > thread - maybe from other threads for all I know. I've pasted in my
> last
> > > comments and your reply to them below and will insert my current
> comments
> > > within.
> > > No - very correct. Whether the fibers absorb moisture at the
molecular
> > > level (not true), or at any other level, they can only absorb as much
as
> > > they are allowed to hold by the mechanical constraintes placed on
them.
> A
> > > tight joint will not absorb as much moisture as a plank laid out in
the
> > same
> > > high RH environment. What you say above about absorbing moisture and
> > > releasing it above is otherwise true, but it does not address the
> > mechanical
> > > constraint. Nor does the article.
> > >
> >
> > Sorry, but until water is no longer influence-bonded to the cellulose
> (read
> > FSP), and until you squeeze all the air out by collapsing the cells and
> > tracheids completely, you are incorrect. Since both are not possible...
> > draw your own conclusions.
> >
>
> Sorry George, but again, your response does not speak to the point in
> question. Mechanical constraint poses different influences on a piece of
> wood than does the absence of it.
>
>
Mike, you need to think. You cannot compress a tenon into a mortise so
tight as to remove all the air from the tenon. Period, end of sentence.
Since there is available air space, water, an incompressible, will expand
the cellulose to compress the air spaces.
This is so basic, I don't understand what you might be thinking.
"Mike Marlow" <[email protected]> wrote in message
news:[email protected]...
>
> "George" <george@least> wrote in message
> news:[email protected]...
> >
> > Mike, you need to think. You cannot compress a tenon into a mortise so
> > tight as to remove all the air from the tenon. Period, end of sentence.
>
> That's correct. I never implied it could be done.
>
> > Since there is available air space, water, an incompressible, will
expand
> > the cellulose to compress the air spaces.
>
> To some point, but we're talking about humidity here George, not water
under
> pressure.
>
Mike, you're starting to change your tune now, so I assume you've finally
caught on to the fact that moisture changes within a M/T joint, and can
cause compression sets to the fiber which will become gaps later as the
joint dries. The joy of the joint, as mentioned way back, is that it holds
mechanically even when loose in the load direction, when pinned to keep the
shoulders registered against the face of the mortised piece, it even
survives the other five load directions when glueless.
As to your latest - once again your knowledge base is too narrow. Man has
been pouring water onto wooden wedges to break blocks from quarry walls for
thousands of years.
"Doug Miller" <[email protected]> wrote in message
news:[email protected]...
> In article <[email protected]>, "George" <george@least>
wrote:
>
> >As to your latest - once again your knowledge base is too narrow. Man
has
> >been pouring water onto wooden wedges to break blocks from quarry walls
for
> >thousands of years.
>
> Pouring water directly onto a piece of wood is a bit different from
exposing
> it to atmospheric humidity, don't you suppose?
>
Only if I didn't understand wood. I heartily recommend the study of the
material whose name is in the title of this group to you.
The incompressible fluid replaces the air, then the adsorption at the
molecular level produces the rest of the hydraulic force to split. This is
what happens to wood with humidity cycling. It adsorbs moisture, bonding at
the molecular level. Whether or not there was expansion of the fibers
themselves was the original bone of contention.
If you're in the temperate zone you can get some extra oomph by waiting for
nighttime and the freeze....
"Doug Miller" <[email protected]> wrote in message
news:[email protected]...
> By making no distinction between the two cases, you appear to be
suggesting
> that the magnitude of the force exerted is the same when a small amount of
> moisture is absorbed from the atmosphere, as when a large amount of
moisture
> is absorbed from immersion in liquid.
>
That was your idea. Mine was that the principle of wood adsorbing moiture
and exerting force was well-known
Sorry that your were ignorant of it.
> If this is the case, I heartily recommend to you the study of logic; if
this
> is not the case, I heartily recommend to you the study of the English
> language, in particular William Zinsser's book "On Writing Well" in which
he
> makes the point that the purpose of writing is not to be understood, but
to
> make it impossible to be misunderstood.
>
Nah, after grade three, the reader is supposed to know what's on the page
and what's in their imagination.
"George" <george@least> wrote in message
news:[email protected]...
>
> "Mike Marlow" <[email protected]> wrote in message
> news:[email protected]...
> >
> > "George" <george@least> wrote in message
> > news:[email protected]...
> > >
> > > "Mike Marlow" <[email protected]> wrote in message
> > > news:[email protected]...
> > > > George:
> > > >
> > > > I never saw your reply below, to my comments until I did a google
> search
> > > on
> > > > the thread. For some reason, my ISP dropped some of the posts from
> that
> > > > thread - maybe from other threads for all I know. I've pasted in my
> > last
> > > > comments and your reply to them below and will insert my current
> > comments
> > > > within.
> > > > No - very correct. Whether the fibers absorb moisture at the
> molecular
> > > > level (not true), or at any other level, they can only absorb as
much
> as
> > > > they are allowed to hold by the mechanical constraintes placed on
> them.
> > A
> > > > tight joint will not absorb as much moisture as a plank laid out in
> the
> > > same
> > > > high RH environment. What you say above about absorbing moisture
and
> > > > releasing it above is otherwise true, but it does not address the
> > > mechanical
> > > > constraint. Nor does the article.
> > > >
> > >
> > > Sorry, but until water is no longer influence-bonded to the cellulose
> > (read
> > > FSP), and until you squeeze all the air out by collapsing the cells
and
> > > tracheids completely, you are incorrect. Since both are not
possible...
> > > draw your own conclusions.
> > >
> >
> > Sorry George, but again, your response does not speak to the point in
> > question. Mechanical constraint poses different influences on a piece
of
> > wood than does the absence of it.
> >
> >
> Mike, you need to think. You cannot compress a tenon into a mortise so
> tight as to remove all the air from the tenon. Period, end of sentence.
> Since there is available air space, water, an incompressible, will expand
> the cellulose to compress the air spaces.
>
> This is so basic, I don't understand what you might be thinking.
>
>
Going back to my original point - I stated that while yes, the tenon will
swell some with higher humidity, so will the mortise, and the mechanical
constriction placed on this joint will serve to limit the expansion from
changes in humidity. This is not to say that the joint members will not
take on the moisture, but that they will not take it on in the same manner
as a plank laying unencumbered in the same environment. My point was in
response to the number of posts which proclaim "explosions" of MT joints.
This simply does not happen on a regular basis and there is more to wood and
its reaction to its environment than simple moisture levels.
--
-Mike-
[email protected]
"George" <george@least> wrote in message
news:[email protected]...
>
> Mike, you need to think. You cannot compress a tenon into a mortise so
> tight as to remove all the air from the tenon. Period, end of sentence.
That's correct. I never implied it could be done.
> Since there is available air space, water, an incompressible, will expand
> the cellulose to compress the air spaces.
To some point, but we're talking about humidity here George, not water under
pressure.
--
-Mike-
[email protected]
In article <[email protected]>, "George" <george@least> wrote:
>As to your latest - once again your knowledge base is too narrow. Man has
>been pouring water onto wooden wedges to break blocks from quarry walls for
>thousands of years.
Pouring water directly onto a piece of wood is a bit different from exposing
it to atmospheric humidity, don't you suppose?
--
Regards,
Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?
In article <[email protected]>, "George" <george@least> wrote:
>Nah, after grade three, the reader is supposed to know what's on the page
>and what's in their imagination.
That explains why so much of what you say makes so little sense.
--
Regards,
Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?
"George" <george@least> wrote in message
news:[email protected]...
>
> "Mike Marlow" <[email protected]> wrote in message
> news:[email protected]...
> > George:
> >
> > I never saw your reply below, to my comments until I did a google search
> on
> > the thread. For some reason, my ISP dropped some of the posts from that
> > thread - maybe from other threads for all I know. I've pasted in my
last
> > comments and your reply to them below and will insert my current
comments
> > within.
> > No - very correct. Whether the fibers absorb moisture at the molecular
> > level (not true), or at any other level, they can only absorb as much as
> > they are allowed to hold by the mechanical constraintes placed on them.
A
> > tight joint will not absorb as much moisture as a plank laid out in the
> same
> > high RH environment. What you say above about absorbing moisture and
> > releasing it above is otherwise true, but it does not address the
> mechanical
> > constraint. Nor does the article.
> >
>
> Sorry, but until water is no longer influence-bonded to the cellulose
(read
> FSP), and until you squeeze all the air out by collapsing the cells and
> tracheids completely, you are incorrect. Since both are not possible...
> draw your own conclusions.
>
Sorry George, but again, your response does not speak to the point in
question. Mechanical constraint poses different influences on a piece of
wood than does the absence of it.
--
-Mike-
[email protected]
"Mike Marlow" theorized incorrectly:
> >> Wood fibers that are constrained can only
> >> absorb water to the point that they equal the force placed on them by the
> >> joint. At that point they effectively reach their saturation level.
Mike-
think about it like this- wood compresses. if it is compressed very
much, it crushes. once crushed, it will not return to it's original
size. water causes wood to expand. the force exerted by the water is
very high (remember hydraulics?). given enough water and a tight enough
joint, the expansion force of the water exceeds the crush limit of the
wood. remove the water and you have a loose joint.
items that will have to endure repeated wet/dry cycles need to be held
together without relying on constrained jointery.
In article <[email protected]>,
[email protected] (Doug Miller) wrote:
> In article <[email protected]>, "George" <george@least> wrote:
>
> >As to your latest - once again your knowledge base is too narrow. Man has
> >been pouring water onto wooden wedges to break blocks from quarry walls for
> >thousands of years.
>
> Pouring water directly onto a piece of wood is a bit different from exposing
> it to atmospheric humidity, don't you suppose?
of course. and the force required to put a little compression set on a
tennon is a bit different than the force required to split a slab of
granite off of a quarry face, don't you suppose?
"bridger" <[email protected]> wrote in message
news:[email protected]...
>
> "Mike Marlow" theorized incorrectly:
>
> > >> Wood fibers that are constrained can only
> > >> absorb water to the point that they equal the force placed on them by
the
> > >> joint. At that point they effectively reach their saturation level.
>
>
> Mike-
> think about it like this- wood compresses. if it is compressed very
> much, it crushes. once crushed, it will not return to it's original
> size. water causes wood to expand. the force exerted by the water is
> very high (remember hydraulics?). given enough water and a tight enough
> joint, the expansion force of the water exceeds the crush limit of the
> wood. remove the water and you have a loose joint.
>
> items that will have to endure repeated wet/dry cycles need to be held
> together without relying on constrained jointery.
I realize I'm speaking a bit of heracy here, but think about the large
number of MT joints we are surrounded by on a daily basis. How many of
those do we find loosened by humidity? By racking, as in a chair that gets
rocked in, sure, but by simple humidity? We just don't find that to be a
huge problem. While I agree that wood compresses and crushes, it takes
significant pressure to do this. My point is that the mechanical
constraints caused by the joint itself make normal humidity cycles unable to
consistently cause this type of pressure. We're not talking about putting
the joint under water here, we're talking about what furniture is exposed to
every day. I have personally brought furniture home from the Orient where
humidity levels are monsterous, and some of that came back to the States, to
Utah where humidity is near zero. No problems. That same stuff then made
it across the country to NY where humidity does vary considerably throughout
the year. Still tight as the day I bought it. Don't misunderstand what I'm
trying to say here - I'm not arguing that tight jointery alone is
suffiecient for long term survival of the joint, such that glue would not be
necessary. I started this thought in response to the posts about humidity
causing MT joints to explode.
--
-Mike-
[email protected]
"bridger" <[email protected]> wrote in message
news:[email protected]...
>
> "Mike Marlow" theorized incorrectly:
>
> > >> Wood fibers that are constrained can only
> > >> absorb water to the point that they equal the force placed on them by
the
> > >> joint. At that point they effectively reach their saturation level.
>
>
> Mike-
> think about it like this- wood compresses. if it is compressed very
> much, it crushes. once crushed, it will not return to it's original
> size. water causes wood to expand. the force exerted by the water is
> very high (remember hydraulics?). given enough water and a tight enough
> joint, the expansion force of the water exceeds the crush limit of the
> wood. remove the water and you have a loose joint.
>
> items that will have to endure repeated wet/dry cycles need to be held
> together without relying on constrained jointery.
You are assuming that expansion of the wood in the mortice will crush the
tenon locally..It would seem to me it might deform a little but basically
this would be within the "elastic limit" of the wood. Bare in mind wood is a
very complex material regarding it's engineering properties and has a
different moduli depending which grain direction you are considering ..
Getting back to the crushing situation again from my standpoint and even
considering the preceeding and even realizing that wood is not a homogenious
material iof it cannot move in one axis I would at least some movement in
another unconstrained axis.resulting in a reduction of pressure [stress].
Again considering the "hydraulic" aspects the pressure in the joint is
pretty much the same as atmospheric and always will be regardless of how
well the finishes seal the wood . mjh
In article <[email protected]>, "George" <george@least> wrote:
>
>"Doug Miller" <[email protected]> wrote in message
>news:[email protected]...
>> In article <[email protected]>, "George" <george@least>
>wrote:
>>
>> >As to your latest - once again your knowledge base is too narrow. Man
>has
>> >been pouring water onto wooden wedges to break blocks from quarry walls
>for
>> >thousands of years.
>>
>> Pouring water directly onto a piece of wood is a bit different from
>exposing
>> it to atmospheric humidity, don't you suppose?
>>
>
>Only if I didn't understand wood. I heartily recommend the study of the
>material whose name is in the title of this group to you.
>
>The incompressible fluid replaces the air, then the adsorption at the
>molecular level produces the rest of the hydraulic force to split. This is
>what happens to wood with humidity cycling. It adsorbs moisture, bonding at
>the molecular level. Whether or not there was expansion of the fibers
>themselves was the original bone of contention.
By making no distinction between the two cases, you appear to be suggesting
that the magnitude of the force exerted is the same when a small amount of
moisture is absorbed from the atmosphere, as when a large amount of moisture
is absorbed from immersion in liquid.
If this is the case, I heartily recommend to you the study of logic; if this
is not the case, I heartily recommend to you the study of the English
language, in particular William Zinsser's book "On Writing Well" in which he
makes the point that the purpose of writing is not to be understood, but to
make it impossible to be misunderstood.
--
Regards,
Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?