Flying on the Cheap - Wood

On Thu, 10 Aug 2006 12:49:22 -0400, "Peter Dohm"
wrote:


"David Melby Cavalier" wrote in message
roups.com...

wrote:
To All:



Since Veeduber's original post, I have taken a long glance at the lumber in
both of the local big boxes, as well as a couple of the local independents,
and I have concluded that the method is reasonable and a good compromise.
Arguments in favor include:
1) the high cost of shipping for small quantities,
2) the ability to buy a little at a time
(think empenage kit, wing kit, etc.),
3) laminating can be used to defeat any remaining tendency of wood to warp
or bow over time,
4) laminated wood better resists splitting, and
5) the relative amount of expertise (a/k/a experience) required to evaluate
small (thin) peices is less than that required for large (thick) peices.

There is no question that more work, including a lot of clamping, is
required to splice and laminate. But the old timers all swear by it and I
have NEVER heard or read anything in opposition from an experienced source!

That does not mean that I either will or will not use wood as the base
material for a composite, only that I kow it to be a sound engineering
material.

Peter


cellulose is a macro molecule assembled from sugar.
apart from some grain characteristics that are species related the
main arbiter for wood strength is its density. since most of the wood
you see in commercial sales areas is all at 12 to 15% moisture content
the density of the wood is a reasonable guide as to its strength.
compression, tension and izod tests are actually what you need but the
visual inspection of wood to exclude defects (from the actual length
of the cut piece as veedubber suggests) has served builders well for
all of aviation.

the only other piece of information needed for laminating is an
understanding of whether the lignin binding the cellulose together is
a thermoset plastic or a thermosoftening plastic.
thermosoftening lignins allow for woods that can be steamed and shaped
very easily. thermosetting lignin makes for a wood that should only be
used in straight pieces.

my own wood is sourced via a relative on the other side of the country
from the stocks of a chap who makes bee hive boxes for the apiary
industry. Talk to people and ask around because you can find some
amazing wood sources. One chap I know stumbled on 3 pieces of 50 year
old spruce, that were absolutely straight grained for over 30 ft, out
of a deceased estate. he now has enough for two aeroplanes.

if you look around and weigh woods you will find an amazing array of
suitable woods. I'm writing from Australia but in my local Bunnings (
a clone of your home depot) I can get Alaskan Yellow Cedar that ranges
from useless heavily knotted pieces to pieces with close straight
grain for over 6ft. I can find Australian "Oak" in densities from just
heavier than Spruce to nearly 65lb per cubic ft. I can occasionally
source Oregon Pine (Douglas Fir) that is usually suitable.
Mainly though I use Queensland Hoop Pine in the manner that Veedubber
suggests.

One of the keys to getting a supply of good wood is to be prepared to
buy it when it becomes available. It is a natural product and supply
is variable. There are lots of people out to obtain good woods.

I think my aircraft will have about 8 species of wood in it by the
time I'm finished. I'm using it because Wood structures are
permanently repairable.

Stealth Pilot