Spruce

"plasticguy"
:


OK, let's say i go to the nearest supplier who has (allegedly) got
some Sitka of the correct quality. Let's say he has some boards about
12 foot long and about 6 inches square.
OK, I think I can manage a ring count and gradient as well as seeing
if my spars will come out quarter sawn. after that, i'm lost. I think
I can probably spot a fracture on a raw board and moisture isn't
realyan isue since i know someone who can kinln dry it for me, but
aside formall this, what am I really looking for?

Theres an old AC on the subject. Also look thru AC43.
Another place to look is for "LADDER GRADE" wood.
Older fire department ladders were wood and had very similar
requirements as airplane spars. Asking for ladder grade wood
is easier to do than to ask for airplane spar stock. Now that you
have more places to look, go find what you need. Take a plane and put
a few strokes
on the end of what you might need, look it over. You should be able
to find what you need. NOW DON"T TAKE MY HEAD OFF, I didn't say
to substitute ladder grade for AC43 wood. I just said that the specs
are so close
that asking for ladder grade wood gets you a bunch more places to
check out and doesn't get people afraid of liability...... Scott.


Yeah, I have the AC all right. What i need is a bit more pratical advice.
One of the other guys in my group got some very god spruce form this
dealer. the dealer himself seems to know what it is i'm looking for and is
going to let me see a good selection of logs. Local dealers are a problem
for me, actually (I'm not in the US) Local spruce is crap, forthe most part
and this is genuine sitka from Canada, but it isn't desgnated "aircraft
Spruce" so it's up to me to eyeball it when I'm buying it and make a god
cal on the day so's I don't waste my time and money. The plane idea's a
good one though!

First, find the center of the tree :-)

Looking at the butt-end of the 6x6, note the curvature of the annular
rings. You want to rotate the six-by until the curves are up, the
'cup' is down.

if the log was quarter-sawn the center of the log will be straight
down, relative to the center of curvature. It probably won't be but
the following will still work.

Because a log is a cylinder you can't avoid some curvature in the
annular rings across the width of a spar but you'd like to have them
symmetrical; without any slope from one edge to the other, which is why
you use quarter-sawing. This is because you want the stresses of
flight to be uniformly distributed around the center of the spar. If
their is any slope to the annular rings the center is displaced toward
the down-hill side of the slope. and some portions of the spar's
cross-section end up seeing higher stresses than other portions.

The amount of curvature across a 6x6 will give you some idea of the
diameter of the log. Since you want the flattest possible curvature
you want wood from near the outside of a log about four feet in
diameter. By measuring the center height of an annular ring as well as
its chord (ie, width of the timber) you can work out the diameter at
that particular section of the tree. For 10 rings to the inch , for a
six inch timber, a center height of about a quarter of an inch sez the
tree was about four foot across at that point. Which is good. Closer
you get to the core, the more pin-knots & pitch pockets you'll
encounter. What you'd like to get is wood from the mature growth of
the tree, after it's attained enough height so that it stops throwing
out branches.

So long as the ring count is uniform, anything from 8 per inch on up
will pass inspection but critical builders will often spec a minimum of
10 or 12 rings per inch. Anything more than 16 or so, the weight goes
up faster than the strength, which is why that old-growth Doug fir,
with counts up to 32/in looks better on paper than in use -- the stuff
runs about 40 pounds a cubic foot (!)

If all that checks out, take a look at the run-out of the grain. You
can do this on either surface, once you know how it was sawn. MilSpec
calls for a minimum of 1 in 15, meaning you pick out a grain and follow
it for 15 inches. If it moves more than an inch laterally in that
distance, you look for another stick.

The truth is, minimum grain run-out is determined by the part in the
airplane, in that you'd like to have the grain not run out for the
length of the part. For example, with a 16' spar having a depth of six
inches you'd like to have a run-out of 1-in-32, which would be the
ideal. One in fifteen is a little more than twice that and practice
has shown that's good enough.

In reality, working with wood taken from near the base of the tree (ie,
where the 'cylinder' is fairly uniform), with Sitka spruce it's not
uncommon to see grain having a run-out of one inch in fifteen FEET.
(You really gotta love wood like that :-)

Is it twisted? (If so, you don't want it.) To discover twist, you
need to examine both side of the piece, looking at the position of the
grain relative to the edge and comparing one side against the other.
If the grain is twisted, the run-out on one edge will be different from
the other. That's okay for bridge timbers but when you slice the balk
into spars, they'll tend to turn into pig-tails. Trees exposed to the
wind often have unusual grain patterns -- curves, spirals and so on.
Not the sort of thing you want in an airplane (or a mast).

Compression fractures are easy to spot in freshly sawn lumber (ie, when
you have both sides of the log available for inspection) but difficult
to detect after the lumber has cured. To get it to show up you need to
plane the surface. It's kind of hard to describe what a compression
failure looks like but it gives itself away as an anomolous feature,
usually linear and regular, that cuts across the grain. On close
inspection the annular rings may appear to have been offset by some
small amount and the cellular structure of the wood across the off-set
portion will be compressed. You'll need about a 3x loupe to see this
clearly but the usual inspection doesn't need to go that far since the
other evidence tells you what you need to know.

An honest sawyer won't sell you wood having a compression fracture...
unless you work for Home Depot or whatever. (Then they'll sell you
ANYTHING :-)

Truth is, it's not as hard as it sounds. But it remains a subjective
analysis in which experience plays a crucial role. Fortunately, the
odds are overwhelmingly in your favor.

This has probably been about as clear as mud. Kinda hard to describe
something you learned by actually handling the wood.

-R.S.Hoover

PS -- The liteature takes a stab at explaining 'quarter-sawn' but it's
pretty clear most authors have never stood there and watched it happen
:-)

egroups.com:

First, find the center of the tree :-)

Looking at the butt-end of the 6x6, note the curvature of the annular
rings. You want to rotate the six-by until the curves are up, the
'cup' is down.

if the log was quarter-sawn the center of the log will be straight
down, relative to the center of curvature. It probably won't be but
the following will still work.

Because a log is a cylinder you can't avoid some curvature in the
annular rings across the width of a spar but you'd like to have them
symmetrical; without any slope from one edge to the other, which is why
you use quarter-sawing. This is because you want the stresses of
flight to be uniformly distributed around the center of the spar. If
their is any slope to the annular rings the center is displaced toward
the down-hill side of the slope. and some portions of the spar's
cross-section end up seeing higher stresses than other portions.

The amount of curvature across a 6x6 will give you some idea of the
diameter of the log. Since you want the flattest possible curvature
you want wood from near the outside of a log about four feet in
diameter. By measuring the center height of an annular ring as well as
its chord (ie, width of the timber) you can work out the diameter at
that particular section of the tree. For 10 rings to the inch , for a
six inch timber, a center height of about a quarter of an inch sez the
tree was about four foot across at that point. Which is good. Closer
you get to the core, the more pin-knots & pitch pockets you'll
encounter. What you'd like to get is wood from the mature growth of
the tree, after it's attained enough height so that it stops throwing
out branches.

So long as the ring count is uniform, anything from 8 per inch on up
will pass inspection but critical builders will often spec a minimum of
10 or 12 rings per inch. Anything more than 16 or so, the weight goes
up faster than the strength, which is why that old-growth Doug fir,
with counts up to 32/in looks better on paper than in use -- the stuff
runs about 40 pounds a cubic foot (!)

If all that checks out, take a look at the run-out of the grain. You
can do this on either surface, once you know how it was sawn. MilSpec
calls for a minimum of 1 in 15, meaning you pick out a grain and follow
it for 15 inches. If it moves more than an inch laterally in that
distance, you look for another stick.

The truth is, minimum grain run-out is determined by the part in the
airplane, in that you'd like to have the grain not run out for the
length of the part. For example, with a 16' spar having a depth of six
inches you'd like to have a run-out of 1-in-32, which would be the
ideal. One in fifteen is a little more than twice that and practice
has shown that's good enough.

In reality, working with wood taken from near the base of the tree (ie,
where the 'cylinder' is fairly uniform), with Sitka spruce it's not
uncommon to see grain having a run-out of one inch in fifteen FEET.
(You really gotta love wood like that :-)

Is it twisted? (If so, you don't want it.) To discover twist, you
need to examine both side of the piece, looking at the position of the
grain relative to the edge and comparing one side against the other.
If the grain is twisted, the run-out on one edge will be different from
the other. That's okay for bridge timbers but when you slice the balk
into spars, they'll tend to turn into pig-tails. Trees exposed to the
wind often have unusual grain patterns -- curves, spirals and so on.
Not the sort of thing you want in an airplane (or a mast).

Compression fractures are easy to spot in freshly sawn lumber (ie, when
you have both sides of the log available for inspection) but difficult
to detect after the lumber has cured. To get it to show up you need to
plane the surface. It's kind of hard to describe what a compression
failure looks like but it gives itself away as an anomolous feature,
usually linear and regular, that cuts across the grain. On close
inspection the annular rings may appear to have been offset by some
small amount and the cellular structure of the wood across the off-set
portion will be compressed. You'll need about a 3x loupe to see this
clearly but the usual inspection doesn't need to go that far since the
other evidence tells you what you need to know.

An honest sawyer won't sell you wood having a compression fracture...
unless you work for Home Depot or whatever. (Then they'll sell you
ANYTHING :-)

Truth is, it's not as hard as it sounds. But it remains a subjective
analysis in which experience plays a crucial role. Fortunately, the
odds are overwhelmingly in your favor.

This has probably been about as clear as mud. Kinda hard to describe
something you learned by actually handling the wood.

No, actually, that's exactly what i needed. A step by step appraoch to
actually examining a log. All those 1940's reprints of government flyers
bout it have only confused the hell out of me.

-R.S.Hoover

PS -- The liteature takes a stab at explaining 'quarter-sawn' but it's
pretty clear most authors have never stood there and watched it happen
:-)

Actually, that's the one part i understand well!

Thanks a million of that. Might be an idea if you wrote that down and sent
it to the EAA to put in some future edition of one of their books.

Caveat Empty Headed wrote:

"plasticguy"
:


OK, let's say i go to the nearest supplier who has (allegedly) got
some Sitka of the correct quality. Let's say he has some boards about
12 foot long and about 6 inches square.
OK, I think I can manage a ring count and gradient as well as seeing
if my spars will come out quarter sawn. after that, i'm lost. I think
I can probably spot a fracture on a raw board and moisture isn't
realyan isue since i know someone who can kinln dry it for me, but
aside formall this, what am I really looking for?

Theres an old AC on the subject. Also look thru AC43.
Another place to look is for "LADDER GRADE" wood.
Older fire department ladders were wood and had very similar
requirements as airplane spars. Asking for ladder grade wood
is easier to do than to ask for airplane spar stock. Now that you
have more places to look, go find what you need. Take a plane and put
a few strokes
on the end of what you might need, look it over. You should be able
to find what you need. NOW DON"T TAKE MY HEAD OFF, I didn't say
to substitute ladder grade for AC43 wood. I just said that the specs
are so close
that asking for ladder grade wood gets you a bunch more places to
check out and doesn't get people afraid of liability...... Scott.

Yeah, I have the AC all right. What i need is a bit more pratical advice.
One of the other guys in my group got some very god spruce form this
dealer. the dealer himself seems to know what it is i'm looking for and is
going to let me see a good selection of logs. Local dealers are a problem
for me, actually (I'm not in the US) Local spruce is crap, forthe most part
and this is genuine sitka from Canada, but it isn't desgnated "aircraft
Spruce" so it's up to me to eyeball it when I'm buying it and make a god
cal on the day so's I don't waste my time and money. The plane idea's a
good one though!


Get with your local EAA chapter, they should have a few people who can
show you around.

Dan, U.S. Air Force, retired

"Dan, U.S. Air Force, retired"
sednews:KC_ae.32825$d43.8168@lakeread03:

Caveat Empty Headed wrote:

"plasticguy"
:


OK, let's say i go to the nearest supplier who has (allegedly) got
some Sitka of the correct quality. Let's say he has some boards
about 12 foot long and about 6 inches square.
OK, I think I can manage a ring count and gradient as well as seeing
if my spars will come out quarter sawn. after that, i'm lost. I
think I can probably spot a fracture on a raw board and moisture
isn't realyan isue since i know someone who can kinln dry it for me,
but aside formall this, what am I really looking for?

Theres an old AC on the subject. Also look thru AC43.
Another place to look is for "LADDER GRADE" wood.
Older fire department ladders were wood and had very similar
requirements as airplane spars. Asking for ladder grade wood
is easier to do than to ask for airplane spar stock. Now that you
have more places to look, go find what you need. Take a plane and
put a few strokes
on the end of what you might need, look it over. You should be able
to find what you need. NOW DON"T TAKE MY HEAD OFF, I didn't say
to substitute ladder grade for AC43 wood. I just said that the specs
are so close
that asking for ladder grade wood gets you a bunch more places to
check out and doesn't get people afraid of liability...... Scott.

Yeah, I have the AC all right. What i need is a bit more pratical
advice. One of the other guys in my group got some very god spruce
form this dealer. the dealer himself seems to know what it is i'm
looking for and is going to let me see a good selection of logs.
Local dealers are a problem for me, actually (I'm not in the US)
Local spruce is crap, forthe most part and this is genuine sitka from
Canada, but it isn't desgnated "aircraft Spruce" so it's up to me to
eyeball it when I'm buying it and make a god cal on the day so's I
don't waste my time and money. The plane idea's a good one though!


Get with your local EAA chapter, they should have a few people who can
show you around.


Yeah, I found one guy in my local group that seems to know what he's
talking about. He's connected me with a lumber yard (not exactly down the
road, but WTH)
BTW, ther is no local chapter where i live! Most of the guys are building
very different types of machines than my old tube and rag, too.

On 21 Apr 2005 23:52:07 GMT, "Caveat Empty Headed." wrote:

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?

One of our Fly Baby list folks visited them last summer, and was very pleased.
You should be able to access his posting at:

http://groups.yahoo.com/group/flybabylist/message/4034

Ron Wanttaja

Ron Wanttaja
:

On 21 Apr 2005 23:52:07 GMT, "Caveat Empty Headed." wrote:

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?

One of our Fly Baby list folks visited them last summer, and was very
pleased. You should be able to access his posting at:

http://groups.yahoo.com/group/flybabylist/message/4034

Ron Wanttaja



Excellent. Thanks Ron. Exactly what i needed to know.

Ron Wanttaja wrote:
On 21 Apr 2005 23:52:07 GMT, "Caveat Empty Headed." wrote:


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?


One of our Fly Baby list folks visited them last summer, and was very pleased.
You should be able to access his posting at:

http://groups.yahoo.com/group/flybabylist/message/4034

Ron Wanttaja

One LEETLE thing !! Order your boards the approximate width of their
final use size---i.e. final size + 1/2 " or so for final STRAIGHTENING
AND TRIMMING. I had some beautiful edge grain Doug Fir Kiln Dried, that
had aged in storage for some time nice and flat and straight.. --
I ripped a 1X6 down the middle and had two pieces with about a 1" bow
toward the middle, you could see it opening up as you sawed it--14 Ft.
long. This board had a slight change in the # of growth rings across
the board...must have set up a stress due to the difference in density
across---was probably a small--(relatively} tree.

to get my 4-1/2" spars out of a 5-1/2" board, I sawed about 3/16" off
each side --checked for straightness, let it set a day or two & repeated
the process till I got down to planing & checking after each run
through the planer..

DON'T TAKE IT ALL OFF ONE SIDE AT ONCE !!---Jerry

If your going to go through this much trouble (just a choice of words),
you might want to consider ordering your lumber rough sawn. Although I
used Doug Fir, I ordered my materials rough sawn and was able to mill
twice as many of the smaller parts from a 1" rough sawn board than 3/4"
planed material. It really keeps the cost down. On the down side, you
will have to invest in a cheap planer.
Lou