(Corrie) wrote in message . com...
Thanks, Ryan. Veeduber is indeed generous with his wisdom. Fly5k has
been rather terribly OT of late, but I suspect there are gems in the
archives.

What you say makes a good deal of sense as well. I'd hesitate to
substitute fir for spruce in spars or longerons, as fir is reputed to
be stiffer. The expected amount of 'give' of the beam is likely to
have been designed into the structure. But for other parts, I suppose
it doesn't matter all that much. It struck me as odd, though, that
the Evans VP front spar bulkhead (carries the instrument panel, and
your legs stick through a big opening in the middle) calls for Douglas
Fir for the spar and strut carry-through, spruce for the vertical
members, and pine for a transverse member. I've asked on the vp group
on yahoo, but haven't gotten a definitive answer.

Spent a little while at the local Huge Orange Store tonight looking at
lumber. Lotsa knots and center cuts from little trees. :-(



Ryan Young wrote in message ...
Generally, the wood itself will be stamped or marked on one or both ends
with SOME ID, which may be a little cryptic. "Western Woods" is one common
ID here in Californis, which can be about a half dozen different species.
Luckily, they all have pretty similar mechanical properties.

For a key to wood ID, try "Wood Structure and Identification", Core, Cote,
and Day. Or "What Wood Is That - A Manual of Wood Identification.

Bring a 10X loupe, and a razor knife.

BUT IT JUST DOESN'T MATTER. Read what Veeduber has to say about wood
selection in this group and in the FLY5K yahoo group. Wood selection for
QUALITY is more important than SPECIES. If the grain is OK, the wood will
probably be OK.

Sitka Spruce has lower mechanical properties than just about any commonly
available softwood used for structures - worse than Western Hemlock, Douglas
Fire, etc. But it's lighter than they are, and it's strength/weight ratio
is very high, which is why it's often called for in aircraft work.

You can build a plane just as strong with other woods, it will just weigh a
wee bit more.

The EAA has a book available on aircraft woodwork, but I don't know if
it has some of the same stuff on selecting and grading wood that is in
an old publication of theirs that I bought 20 years ago. The selection
process and the moisture content of the lumber is pretty critical. I
chose to use Spruce in my Jungster II because I could obtain stock
that was graded for aircraft and the quantity of wood in an aircraft
is so little that the price difference was not as important as the
peace of mind. Also Spruce is much easier to work with than Douglas
Fir for instance. There are other wood as good or better than spruce,
but they are scarce, such as Port Orford Cedar. Most of the wood
expense on my project was in the plywood and the metal wing struts
cost almost as much as all the other material.

Ed Sullivan