On Jul 7, 2:01 pm, (Doug Miller) wrote:
In article .com, RicodJour wrote:



On Jul 7, 12:10 pm, (Doug Miller) wrote:
In article .com, RicodJour
wrote:

On Jul 7, 11:05 am, (Doug Miller) wrote:
In article , "Eigenvector"
wrote:
I was kind of wondering why the wood wouldn't swell around the nail,
making
it all but impossible to extract.

Because the wood swelling will make the holes *larger*, not smaller.

Why wouldn't the wood swell in all directions?

It does -- but it does not swell *uniformly* in all directions, because wood
does not have a uniform structure. Its fibers are long and narrow, with the
long axis parallel to the trunk of the tree. The extent of tangential
dimensional change (parallel to the growth rings) in response to changing
moisture content is, as a general rule, approximately double the extent of
radial dimensional change (perpendicular to the growth rings), and either one
is several orders of magnitude greater than the axial dimensional change
(parallel to the trunk of the tree).

To put it in somewhat simpler terms: when a piece of wood absorbs moisture,
it
gets wider. It also gets thicker, but proportionately by only about half as
much as it increases in width. The length hardly changes at all.

There's no need to put it more simply - I'm more than passably
familiar with wood properties. It sounds like what you're saying -
correct me if I'm wrong - is that the wood fibers around the nail are
somehow different than the wood fibers not next to the nail.

Quite the contrary. I'm saying that they're all the same.

The wood
fibers run in the same direction, and the hole is drilled in the same
direction as well. How can the wood fibers react differently?

They don't.

Suppose for the sake of illustration that the width of the board increases by
ten percent when it's saturated with water; suppose further that we have a
1/4" diameter hole drilled in the middle of a board that's 2.25" wide (1" on
each side of the hole).

The board swells to a total width of 2.25 + 10% = 2.475".
The wood to the left of the hole started out 1" wide, and swells 10% to 1.1".
So does the wood to the right of the hole. Total 2.2" left and right. Leaves
0.275" for the hole, no?

It's *exactly* the same principle as heating a piece of metal to enlarge a
hole for making a friction fit: metal expands when heated, and wood expands
when it gets wet. Holes in metal get larger when heated, and holes in wood get
larger when wet. The only difference is that since wood does not expand at the
same rate in the x and y axes, due to its non-uniform structure, circular
holes in wood become elliptical when they expand, instead of remaining
circular as do holes in metal.

I'll argue my point with a very simple test that you can do for
yourself. Drill a hole the exact size of a nail in a piece of wood,
drilling along the grain. Soak the wood overnight. You don't have to
boil it. Try to insert the nail the next morning. The wood will have
expanded, and the hole will have gotten smaller, not larger. The hole
may not be perfectly round, but the net area of the hole will be
smaller. I've done this. Try it, you'll see.

Simple practical tests outweigh theoretical ruminations. Ask Richard
Feynman...well, he's dead, but he'd agree with me.

R