Oak.

This is coolbert:

"Built in an era when a wooden ship had an expected
service life of ten to fifteen years, Constitution
was now thirty-one years old."

From the wiki entry for the USS Constitution, some interesting items regarding the various repairs/refurbishments/restorations - - past, present, and future.

Wood from certain specific species - - once found in abundance, now scarce. NOT only hard to find, but hard to find in the right sizes, age, and shapes!

And, those materials used during previous repairs/refurbishments/restorations as replacements - - but NOT of the original material - - found to be lacking.

1. Southern live oak being the preferred wood as used in the construction of the Constitution, a material at the time easily obtainable:

"Primary materials used in her construction were
white pine, longleaf pine, white oak, and, most
importantly, southern live oak, which was cut and
milled at Gascoigne Bluff in St. Simons, Georgia . .
. In total, 60 acres (24 ha) of trees were needed
for her construction [USS Constitution]"

2. Southern live oak, at the time of the 1925 restoration being hard to find, at least in the sizes and quantities needed:

"Materials were difficult to find, especially the
live oak needed . . . [there was found] uncovered a
long-forgotten stash of live oak . . . at Naval Air
Station Pensacola, Florida that had been cut sometime
in the 1850s"

3. And during the 1970 repairs/refurbishments/restoration, those materials initially thought to be an adequate substitute for the original, rather found to be lacking, replaced without further ado:

"large quantities of red oak were removed and
replaced. The red oak had been added in the 1950s as
an experiment to see if it would be of better
quality than the live oak, but it had mostly rotted
away by 1970."

[live oak works well, other types of oak do not! The shipwrights of yore knew what they were doing! Live oak si, red oak no!]

4. Repairs/refurbishments/restoration work on the USS Constitution requiring an abundance of top quality white oak, the U.S. Navy creating [1976] a forest preserve exclusively for the cultivation and harvesting of this species [white oak]:

"Commander Martin dedicated [1976] a tract of land
located at the Naval Surface Warfare Center in
Indiana as 'Constitution Grove.' The 25,000 acres
(100 km2) now supply the majority of the white oak
required for repair work"

5. The repairs/refurbishments/restoration work of 1992 again requiring live oak wood in quantities not normally obtainable. Various concerns to the rescue:

"The most difficult task, as during her 1920s
restoration, was the procurement of timber in the
quantity and sizes needed. The city of Charleston,
South Carolina donated live oak trees that had been
felled by Hurricane Hugo in 1989, and the
International Paper Company donated live oak from
its own property"

6. Current repairs/refurbishments/restoration work underway, as we speak, perhaps already reaching completion, a restoration to the original with regard to the support beams and decking, previous replacements found to be inadequate [?]:

"Also in October 2007, she entered a period of repair
expected to last until September 2010. During this
time the entire spar deck will be stripped down to
the support beams and the current Douglas fir
decking will be restored to the original white oak
and yellow pine."

It can be said that the USS Constitution possesses a certain "sacredness"?

And who too from that era of over two hundred years ago would have ever imagined that in the year 2010 the Constitution would still be afloat, a commissioned warship of the U.S. Navy, manned by active duty sailors? I doubt few, if anyone!

coolbert.