wood species question

"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