"Caveat Empty Headed." wrote in message
...
I've located a source of spruce in British Columbia that appears to be
very
good. http://www.timberwright.ca/aircraft.html
anyone dealt with them?

This is for Spars, BTW.

The spruce they supply is uncertified, air -dried and unfinished, but
exceeds the criteria for certification.
They can't certify it as they don't have the equipment,but it is for a
homebuilt. The only thing I'm concerned about is the air dried part of
this. I can get it kiln dried near me, though. Anyone know if this is good
practice? Anything I should be looking out for here?
BTW, their price is half of what ACS is looking for the same dimensions.

"certified aircraft spruce" is rather a misleading term anyway. Who
"certified" it? The FAA certainly didn't, they are not in that business and
do not certify wood.

There is a set of guidelines for selecting wood that meets the quality
standards for aircraft use that was published back in the thirties. I have
it around somewhere but it is the middle of the night and I don't want to go
looking for it. I believe it is ANC18 or some such. You can obtain a copy
from the EAA library. They will photocopy it and send it to you for a very
reasonable copy charge.

Any "certification" of aircraft wood is done by whoever selected the pieces
and he is "certifying" that they met those standards. They cover things
like grain lines per inch and degree of slope of the grain as well as
moisture content. The flaw in wood that is hardest to see is probably a
compression failure. This happens when the log or board was bumped or
shocked sufficiently to overload a line of cells in the wood causing them to
rupture. There is not necessarily a visible dimensional change. They
usually show up as a shiny line one or two cells wide after the wood is
planed. The piece of wood containing that line of ruptured cells will fail
WAY easier than the undamaged wood and will likely break in what we call a
"brash" break. It will just break along that line with no splintering and
will break very suddenly.

I once had an undiscovered compression failure in a wood spar on a
Taylorcraft I was flying. I did a steep turn and the airplane suddenly
rolled out of the turn. The rear spar broke completely off right at the
rear spar fitting where it connected to the fuselage. I looked out the
window at that wing and the trailing edge was up about a foot and flapping!
The only thing keeping the wing on the airplane was the two wing struts and
the forward wing spar connection. If it had been a cantilever wing with a
single spar I would have watched one wing go fluttering away! There was no
visible damage on the outside of the wing at both an extensive annual
inspection and an extensive preflight inspection. No wrinkles in the
fabric. No curves or kinks in the trailing edge. The actual physical
deformation was only a few thousandths of an inch. The wing broke at less
than two G's.

The recent AD on Champion aircraft is an inspection for compression failures
in the wing spar caused by minor damage near the wing tip. That was what
caused the compression failure on the Taylorcraft that was responsible for
my having to have the seat cushion surgically removed from my rear end! It
gets you attention when a wing spar breaks suddenly.

I so have a few samples of spruce spar stock with compression failures in
them that have been cut out of otherwise good material. I will probably
have them around my hangar during the 2005 rec.aviation flyin at
Pinckneyville on May 20, 21, and 22. If anyone is coming to the flyin, drop
Mary an email at so she can plan for the groceries for the
meals.

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )