wood species question

"Gordon Arnaut" wrote

One of the biggest dangers in using wood as a structural material is
compression failures that are almost invisible to the naked eye. A piece
of
wood that has been severely stressed (such as sitting under some big heavy
boxes on the UPS truck) may look perfectly good, but its fibers may be
have
completely lost their strength.
???????????????????????????????????/

You HAVE to be totally kidding. Unless that wood was sitting under a 10,000
lbs box on the UPS truck, it WILL NOT get compressive failure like that.

Most compressive fractures take place when the tree is felled, and lands
across a swag, or on another log.

You had a pretty good writing going, but you lost all credibility, with that
last line of crap.

Also, rupture is not the only mode of failure that is important. You have
to know if the part you are replacing is in tension, compression, bending,
or what. There are different values for each mode.
--
Jim in NC

Do you have some sort of personality disorder?

If you disagree with something I said, then address it in civil terms as I
have done when I disagreed with the other poster's point. There is no
excusable reason to launch into a personal attack and what I wrote "crap."

I would address your objections, but I don't argue with people who don't
adhere to basic civility.

You are obviously an odiferous idiot and as such I will ignore your stupid
outburst.

Gordon Arnaut.




"Morgans" wrote in message
...

"Gordon Arnaut" wrote

One of the biggest dangers in using wood as a structural material is
compression failures that are almost invisible to the naked eye. A piece
of
wood that has been severely stressed (such as sitting under some big
heavy
boxes on the UPS truck) may look perfectly good, but its fibers may be
have
completely lost their strength.
???????????????????????????????????/

You HAVE to be totally kidding. Unless that wood was sitting under a
10,000
lbs box on the UPS truck, it WILL NOT get compressive failure like that.

Most compressive fractures take place when the tree is felled, and lands
across a swag, or on another log.

You had a pretty good writing going, but you lost all credibility, with
that
last line of crap.

Also, rupture is not the only mode of failure that is important. You have
to know if the part you are replacing is in tension, compression, bending,
or what. There are different values for each mode.
--
Jim in NC

"Gordon Arnaut" wrote

If you disagree with something I said, then address it in civil terms as I
have done when I disagreed with the other poster's point. There is no
excusable reason to launch into a personal attack and what I wrote "crap."


I am normally a _very_ civil person, but I go off the deep end when someone
makes a post retorting to have a command of subject matter, then displays an
utter *lack* of grasp on the subject. People who know no better might
believe you, and commit a design change/substitution that kills them. this
is big stuff, with life ending possibilities.

In order to have a compression fracture to take place, the wood has to be
compressed past the ultimate failure of the species, in compression, or if
it were bent, in rupture on the side of the board that is in the "low" side
of the bend. How much force would be required would then depend on the
specifics of the size of the stock. I would dare to say, that the loads
required would be HUGE; it would be enough to crush the floor, and
suspension, and blow the tires of a UPS truck, if it were say, a spar, of
unremarkable size. That is not going to happen from having a box, or boxes,
or even a V-8 engine sitting on it. How ridiculous!

If you purport to write as an expert, dispensing advise, you must be
prepared to take your lumps when you blow it.

You blew it.

Oh, by the way, pot, kettle, black. You seemed to do a pretty good job of
not addressing me in a civil manner.

I do not have a personality disorder, nor am I odiferous, nor am I an idiot.
I was, however, bold enough to call you bluff on a subject you should not be
writing about, if you are so far off base from knowing the basic causes of
this kind of failure in wood.

It seriously makes me wonder how far off base you are on the rest of the
figures and concepts you wrote about. I might suggest that other readers
also view the previous posts made by you with a *very* large grain of salt.

Civil enough? If not, tough. Live with it.
--
Jim in NC

Morgans wrote:

In order to have a compression fracture to take place, the wood has to be
compressed past the ultimate failure of the species, in compression, or if
it were bent, in rupture on the side of the board that is in the "low" side
of the bend. How much force would be required would then depend on the
specifics of the size of the stock. I would dare to say, that the loads
required would be HUGE; it would be enough to crush the floor, and
suspension, and blow the tires of a UPS truck, if it were say, a spar, of
unremarkable size. That is not going to happen from having a box, or boxes,
or even a V-8 engine sitting on it. How ridiculous!


Hey, Jim, I'm not trying to be odiferous (whatever that may be), I'd
just really like to know.

Does it make a difference that they UPS truck will bring the wood in
strips that are much smaller than a forest log? That is, will it stand
more of possibility from damage in the cut and cured state?

Another factor...an object doesn't have to weigh 10,000lbs to apply
10,000psi of force. If the wood ends up supporting another object by an
edge or a corner (or even a point), and the truck hits a bump, 10,000psi
might not be so extreme. A somewhat strained example: someone traps a
coat hanger between the sitka bundle and a V-8 engine place on top.

My sister-in-law got a new hardwood floor installed (I sweated a lot
putting that one in), and started to set little round indentations in
it. She was livid, blaming it on husband and children, started to call
Home Depot and give them what-for. Luckily, I stopped her in time and
pointed out her spiked high-heels. Lot of pressure there from a
one-hundred and ????? pound woman.

I guess that's all just to say, "Don't trust the UPS man." I used to
work a dock. I've seen the forklifts used to help a load 'fit' in the
truck.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

"Ernest Christley" wrote

Hey, Jim, I'm not trying to be odiferous (whatever that may be), I'd
just really like to know.

Thanks for that. I think that *might* be something like stinking, g and I
haven't been close enough to smell you!

I'll attempt to shed some light on your (and others) concerns. I don't
pretend to know everything about wood, but I have studied the forrest
products book, (good stuff) and others on wood AC, and have been around wood
(carpenter, cabinet maker, jack of all trades) all my life.

Does it make a difference that they UPS truck will bring the wood in
strips that are much smaller than a forest log?

Sure, the smaller the piece, and the longer, the less abuse it can stand.

Still, the most common way (by a million percent) of compressive fractures
occur while the wood is in the shape of a log.

That is, will it stand more of possibility from damage in the cut and
cured state?

Actually, wood is stronger in it's dry state. Much stronger. Milled, yes,
it will be weaker than a log, but only because it is not as large.

Another factor...an object doesn't have to weigh 10,000lbs to apply
10,000psi of force.

True, you can generate more than the rated force without the rated weight.
or force. The good old principle of the lever at work, (and mechanical
advantage) is our main concern.

If the wood ends up supporting another object by an edge or a corner (or
even a point), and the truck hits a bump,
10,000psi might not be so extreme.

Humm, this might be possible, but there are other things to consider to make
this a problem.

First, remember, we are talking (P)ounds per (S)quare (I)nch. Most of the
stuff we are going to order are much larger than a square (cross sectional)
inch, thus it will take much more force to be of concern. Lots of
calculations - moments of inertia, leverage, compression, buckling loads,
bending- all much more ugly than I want to go into here. Lets go for broad
concepts, and rough figures.

If the board were supported by a corner, on what is the corner resting on.
A shelf? Shelf gets crusted, if the board is of any size. Remember UPS has
a maximum weight, as I recall, about eighty some pounds. It will be
necessary to have many of these boxes to add up to enough to hurt anything,
except little sticks.

A point, say a rock under the plank? Part of the weight dents the floor or
crushes the rock, (UPS drivers are not in the habit of hauling around a
truck full of gravel) and part of the point load puts a big dent in the
board. This is still not a compressive failure. A compressive failure is a
_line_ of ruptured cells, and hard to see; not what is happening here. It
would make that one point as weak as say, a knot. Easy to detect, so
although the board may be damaged, it is easy to see. Report the damage,
get a new plank, or work (cut it out) to eliminate the damage. That is done
all of the time, to eliminate less that acceptable parts (defects) in the
lumber.

A extreme weight like an engine would not be resting on a sharp point, like
a flange sitting on the plank. It would be on a pallet, thus spreading the
load. Also, UPS does not ship engines; that would be some type of motor
freight.

Another point to consider is that in order to reach the point of rupture,
the board is going to bend a HUGE amount before _any_ damage is done.

A somewhat strained example: someone traps a coat hanger between the
sitka bundle and a V-8 engine placed on top.

Not likely, but once again, the damage would be a dent, not a compressive
failure; at least not anything but a highly localized event. Easy to spot,
so mill it out, or reject it.


My sister-in-law got a new hardwood floor installed (I sweated a lot
putting that one in), and started to set little round indentations in it.
She was livid, blaming it on husband and children, started to call Home
Depot and give them what-
for. Luckily, I stopped her in time and pointed out her spiked
high-heels. Lot of pressure there from a one-hundred and ????? pound woman.

Wow, want to talk extreem pressure, huh? g Yep, high heels are hell on
wood floors. It is easy for a petite woman to put well over 1,000 pounds
per square inch on a floor. Still easy to see; take action to remove or
eliminate the problem... (on the floor, not the woman g)

I guess that's all just to say, "Don't trust the UPS man." I used to
work a dock. I've seen the forklifts used to help a load 'fit' in the
truck.

All easy to see problems. It would be more likely to have the compressive
fracture we are concerned about happen by taking a 1 inch by 8 inch board
supported by raised fulcrums say, 4 feet across, then use the board as a
ramp for the forklift to drive across. (like a bridge) That would be
unusual treatment for even a loading dock, and I believe you would agree.

Wood is a wonderful material. It is flexible, but strong. It can take a
surprising amount of abuse, and spring back, with no damage. After the big
Japanese earthquake, (what, 15 years ago?) the Japanese sent teams of
engineers to further study our wood frame house building practices, because
their mostly steel residential construction methods did not flex, but
buckle.

That (in house construction) is a case of much lower grade lumber. (than
aircraft lumber) You should see what lumber wholesalers are passing off for
#2 grade lumber, nowadays. Also, houses are nailed together, not fastened
with epoxy and scarf joints, like in aircraft practices.

In conclusion, don't worry about airplane lumber getting damaged by UPS.
Large stuff would have to have the whole truck run over it. Smaller stuff
will bend, long before the driver realizes that his loading is a problem,
and if it is firmly bundled, the whole bundle will share the load.

If you are building a wood aircraft, you should be trained in recognizing
defects, eliminating them, and safely orienting, joining and using wood.
Your life is on the line, and you better know what you are doing. There are
many things to worry about, (including substituting species) but damage from
the UPS man delivering your wood should be about 273rd on your list. g
--
Jim in NC

I'm posting this for the normal people in this group who might thing that
this "Morgans" clown actually has some kind of valid point.

His remarks make quite clear that he doesn't know the first thing about
structures. Yet he comes out with guns blazing and hurling unprovoked
insults. What a clown.

For example, take his comment about modulus of rupture not being relevant to
stress in compression or tension.

This is complete gibberish that shows he doesn't understand even the basics.
Modulus of rupture is a measure of a material's strength in bending.

Bending loads on a piece of wood (or other material) typically produce
stress in both compression and tension at the same time.

Take a wood yardstick and hold it by the ends; now try to bend it into a U
shape. The wood fibers on the inside of the curve will be in compression,
while those on the outside will be in tension, simultaneously.

If you apply enough bending moment you can break the stick. But what if you
bend it as far as you can without breaking it and then let it go? Have you
done any damage?

It's quite possible tthat you have damaged the wood fibers that were in
compression (the top of the stick). Almost certainly you will not have
damaged the bottom of the stick, which was under tension.

The reason is that wood is about two to three times stronger in tension than
in compression. So while you didn't break the stick, you might have caused
compression failure on the side of the stick that was on the inside of the
curve. This damage would be most acute on the top surface of the stick and
would be progressivly less until the neutral axis (middle) of the stick.

If you made a saw cut right across the point of bending, you would probably
see -- under a magnifying glass -- wood fibers that have failed in
compression.

If you have ever broken small pieces of wood in half with your hands you
would have experienced this first hand. If you take that yardstick and bend
it until it starts to break, what happens? It does not just snap at once.

The outside part that is under tension will begin to splinter long before it
lets go. Then in order to break it, you instinctively bend it back in the
opposite direction and what happens? It makes a clean break on the top
surface -- the surface that was under compression -- while the bottom
surface continues to splinter.

This shows you just how much stronger the wood is in tension than in
compression. So even bending the stick and letting go befoer it breaks could
have caused compression failure on the top surface. The next time you bend
that stick in the opposite direction, there will be no strength in the top
part -- it will just let go.

That's exactly how sticks of wood can get damaged in transit. All it takes
is bending the stick enough to cause compression on the inside of the bend.
And you would never know by merely looking at it.

Idiot's comments about needing 10,000 pounds on top of the wood simply
illustrate to everyone what a loudmouth know-nothing he is.

All it takes is enough force to bend the plank more than you would normally
do. This does not have to be a lot of force. We are talking about small
planks less than an inch thick. You could easily cause compression failure
on small sticks of wood like this just by bending it forcefully with your
bare hands.

Is that the kind of massive pressure idiot is talking about?

The fact is that this type of damage can and does happen in shipment. It is
quite easy as my explanation should make clear. All that needs to happen is
for the board to be bent awkwardkly -- and this does not take a whole lot of
weight. A couple of humdred pounds acting on the end of a plank could be
enough to do it.

As to his other objection about modulus of rupture not being "enough" of a
measure to determine wood substitution, this is simply not true. This is the
most important measure of strength. Fbu (sometimes referred as jut Fu) is
the ultimate stress before failure in bending.

There are also measurements for stiffness, elasticity, strength in
compression and tension both paralell and perpendicular to the grain and a
few more. But the undisputed fact is that for structural members, Fbu is the
most important measurement.

If the substitute wood passes muster in this measurement, then it will pass
in all the others -- since these strength properties all tend to vary
proportionately across species. For example if pine is 15 percent weaker in
bending than spruce, it is also weaker by a similar amount in the other
strength measures.

In closing, I really have to register my utmost contempt at this pathetic
clown for the way in which he is conducting his attacks. He obviously knows
nothing, yet he has the brass to call into question factual material I have
presented which is 100 percent valid.

I challenge this complete moron to point out one mistake in the methodology
or math I have presented. I will bet dollars to donuts that he won't even
attempt it -- he wouldn't know where to start.


Regards to All (Except to Moron in NC)

Gordon Arnaut.




"Morgans" wrote in message
...

"Gordon Arnaut" wrote

If you disagree with something I said, then address it in civil terms as
I
have done when I disagreed with the other poster's point. There is no
excusable reason to launch into a personal attack and what I wrote
"crap."


I am normally a _very_ civil person, but I go off the deep end when
someone
makes a post retorting to have a command of subject matter, then displays
an
utter *lack* of grasp on the subject. People who know no better might
believe you, and commit a design change/substitution that kills them.
this
is big stuff, with life ending possibilities.

In order to have a compression fracture to take place, the wood has to be
compressed past the ultimate failure of the species, in compression, or if
it were bent, in rupture on the side of the board that is in the "low"
side
of the bend. How much force would be required would then depend on the
specifics of the size of the stock. I would dare to say, that the loads
required would be HUGE; it would be enough to crush the floor, and
suspension, and blow the tires of a UPS truck, if it were say, a spar, of
unremarkable size. That is not going to happen from having a box, or
boxes,
or even a V-8 engine sitting on it. How ridiculous!

If you purport to write as an expert, dispensing advise, you must be
prepared to take your lumps when you blow it.

You blew it.

Oh, by the way, pot, kettle, black. You seemed to do a pretty good job of
not addressing me in a civil manner.

I do not have a personality disorder, nor am I odiferous, nor am I an
idiot.
I was, however, bold enough to call you bluff on a subject you should not
be
writing about, if you are so far off base from knowing the basic causes of
this kind of failure in wood.

It seriously makes me wonder how far off base you are on the rest of the
figures and concepts you wrote about. I might suggest that other readers
also view the previous posts made by you with a *very* large grain of
salt.

Civil enough? If not, tough. Live with it.
--
Jim in NC

"Gordon Arnaut" wrote

I'm posting this for the normal people in this group who might thing that
this "Morgans" clown actually has some kind of valid point.

OK, I tried nice, but you don't want to play, so first of all, a general,
FYT.

His remarks make quite clear that he doesn't know the first thing about
structures. Yet he comes out with guns blazing and hurling unprovoked
insults. What a clown.

For example, take his comment about modulus of rupture not being relevant
to stress in compression or tension.

In contex, if you please. Site the usage, please. I can't defend something
I don't see.

This is complete gibberish that shows he doesn't understand even the
basics. Modulus of rupture is a measure of a material's strength in
bending.

Close. That is when it FAILS.

Bending loads on a piece of wood (or other material) typically produce
stress in both compression and tension at the same time.

Oh really? Why that's all new news to this clown. Wow, thanks.

Take a wood yardstick and hold it by the ends; now try to bend it into a U
shape. The wood fibers on the inside of the curve will be in compression,
while those on the outside will be in tension, simultaneously.

If you apply enough bending moment you can break the stick. But what if
you bend it as far as you can without breaking it and then let it go? Have
you done any damage?

Depends.

Please tell us how you can tell. Give us all a REAL example. Use something
more than modulus of rupture, or buy a vowel.

It's quite possible tthat you have damaged the wood fibers that were in
compression (the top of the stick). Almost certainly you will not have
damaged the bottom of the stick, which was under tension.

Really? How do you know? There are ways to know, or don't you know how to
figure that part?

So while you didn't break the stick, you might have caused compression
failure on the side of the stick that was on the inside of the curve. This
damage would be most acute on the top surface of the stick and would be
progressivly less until the neutral axis (middle) of the stick.

If you made a saw cut right across the point of bending, you would
probably see -- under a magnifying glass -- wood fibers that have failed
in compression.

Don't need a magnifying glass, if you know what to look for.

Idiot's comments about needing 10,000 pounds on top of the wood simply
illustrate to everyone what a loudmouth know-nothing he is.

I was talking about a bending force, or can't you read?

All it takes is enough force to bend the plank more than you would
normally do.

Oh, please tell. How about that. How about a number a bit more specific
than "more than you would normally do." How much is normal? Those numbers
are in there.

This does not have to be a lot of force.

Once again, something more specific, please, professor? No? Oh well. You
obviously show a lot more book knowledge than real application.

You had damn well better understand how all of the figures for each species
apply to how the specific stick will be used. You know nothing that anyone
here should use to build an airplane.

You said something back there about modulus of rupture being the most
important. Yes it is important, but far from _all_ that is important.

How about modulus of elasticity? Some woods will not bend much, until they
suddenly rupture. Might want to know that, right? Some woods are very poor
in tension, and splinter at the drop of a hat. Might want to know about
that, too.

YOU CAN NOT PICK AND CHOOSE WHAT FIGURES YOU WANT TO LOOK AT. YOU MUST USE
THEM ALL, AND UNDERSTAND HOW TO USE THEM ALL.

To say otherwise is to create a death trap, and irresponsible to try to
convince others, that you don't need to consider the loads that will be
placed on each individual part.

Most people do not have the skills and understanding to consider all of the
factors involved. It is VERY clear, at least you do not.

YOU are one more fine example of newsgroups "gods" spouting off, and giving
misinformation that could be deadly.

Ever read the government's forrest products book? It's old, but still the
best of its type. Try it. That is only a start.

By the way, so everyone out there in newsgroup land can best judge how you
are qualified to pass on all of your useful information, how about posting
all of your qualifications? Education, degrees, how many wood airframes you
have analyzed, how many you have built and flown? Any or all of those
things.

Please. Please. Use the Doctor's motto. First do no harm.

You have some un-doing to do.

Don't bother responding to me. You are off my radar; my blood pressure
can't stand it.

Please, group. Learn more from someone who knows more than him (or me)
before taking this one's advise.

Jerk. I hate being like this.
--
Jim in NC

How long have you two been married?

Don't DO that at this hour of the morning. I HATE iced tea coming out my
nose.

{;-)

Jim




"Lou" wrote in message
oups.com...
How long have you two been married?

"Lou" wrote
How long have you two been married?

Ouch! g
--
Jim in NC