Wood grain orientation in a built-up spar

In my effort to learn/remember/practice correct building
procedures,I monitor several wood aircraft design sights. In the
emerauders group,much discussion about using a wingspar that was built
and purchased by another builder. The Emeraud spar consists of 2
laminated built ip beams,w ply intercoastals, and boxed front and rear
w/ply. The spar in question was made with vertical grain wood, and
laminated with the grain perpendicular relative to the wing chord, I
believe the spar caps and laminations should have grain approx.
parallel to the wing chord. If anyone has a definitive answer that may
even prevent an accident go yo yahoo groups,emerauders

In article
,
cmyr wrote:

In my effort to learn/remember/practice correct building
procedures,I monitor several wood aircraft design sights. In the
emerauders group,much discussion about using a wingspar that was built
and purchased by another builder. The Emeraud spar consists of 2
laminated built ip beams,w ply intercoastals, and boxed front and rear
w/ply. The spar in question was made with vertical grain wood, and
laminated with the grain perpendicular relative to the wing chord, I
believe the spar caps and laminations should have grain approx.
parallel to the wing chord. If anyone has a definitive answer that may
even prevent an accident go yo yahoo groups,emerauders

The important item here is the orientation of the wood grains in the
spar caps. They MUST be parallel in the spanwise direction. The spar
webs are there primarily to absorb shear loads, where 45 degree plywood
would be optimum. I really don't think that the orientation of the spar
webs is critical, because their shear stress is far less than their
strength.

SEE:
__________________________________________________ _
__________________________________________________ _ Spar cap
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX X
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX X Web
__________________________________________________ _
__________________________________________________ _ Spar Cap

--
Remove _'s from email address to talk to me.

cmyr wrote:
In my effort to learn/remember/practice correct building
procedures,I monitor several wood aircraft design sights. In the
emerauders group,much discussion about using a wingspar that was built
and purchased by another builder. The Emeraud spar consists of 2
laminated built ip beams,w ply intercoastals, and boxed front and rear
w/ply. The spar in question was made with vertical grain wood, and
laminated with the grain perpendicular relative to the wing chord, I
believe the spar caps and laminations should have grain approx.
parallel to the wing chord. If anyone has a definitive answer that may
even prevent an accident go yo yahoo groups,emerauders

If you are referring to the laminated caps of a box beam on top and
bottom: I have seen this discussion at various stages of heat, several
times before.
The usual conclusion is that if the tree trunk is oriented along the
axis that runs from wingtip to wing tip, it's not terribly important
whether a cross section of the box beam shows vertical grain in the caps
or horizontal. the horizontal grain orientastion is slightly prefered if
I recall. I understand that even well seasoned timber can show some
progressive straightening of curved grain in the cross section, so
having any curve the same in adjacent lamina might be an idea.

Not strictly relevant: an aluminum spar designer decided to add aluminum
strips progressively in the WEB plane near top and bottom rather than on
the top and bottom faces of the I beam he used, for the sake of
convenience, at the cost of some loss of strength in bending.
This was a light single for homebuilding from a couple folks at
Loughborough Tech Aero Dept. as I recall.

Brian W

On Jun 25, 1:22�pm, Brian Whatcott wrote:
cmyr wrote:
� � �In my effort to learn/remember/practice correct building
procedures,I monitor several wood aircraft design sights. In the
emerauders group,much discussion about using a wingspar that was built
and purchased by another builder. The Emeraud spar consists of 2
laminated built ip beams,w ply intercoastals, and boxed front and rear
w/ply. The spar in question was made with vertical grain wood, and
laminated with the grain �perpendicular relative to the wing chord, I
believe the spar caps and laminations should have grain approx.
parallel to the wing chord. If anyone has a definitive answer that may
even prevent an accident go yo yahoo groups,emerauders

If you are referring to the laminated caps of a box beam on top and
bottom: I have seen this discussion at various stages of heat, several
times before.
The usual conclusion is that if the tree trunk is oriented along the
axis that runs from wingtip to wing tip, it's not terribly important
whether a cross section of the box beam shows vertical grain in the caps
or horizontal. the horizontal grain orientastion is slightly prefered if
I recall. I understand that even well seasoned timber can show some
progressive straightening of curved grain in the cross section, so
having any curve the same in adjacent lamina might be an idea.

Not strictly relevant: an aluminum spar designer decided to add aluminum
strips progressively in the WEB plane near top and bottom rather than on
the top and bottom faces of the I beam he used, for the sake of
convenience, at the cost of some loss of strength in bending.
� This was a light single for homebuilding from a couple folks at
Loughborough Tech Aero Dept. as I recall.

Brian W

As I recall , the horizontal grain orientation is preferred because
the adhesive has access to every layer of the wood in the 2 sparcaps
when joined to the front/rear ply webs. With vertical oriented caps,
only the front/rear wood layers would carry all the loads to the ply
webs when assembled.

cmyr wrote:
In my effort to learn/remember/practice correct building
procedures,I monitor several wood aircraft design sights. In the
emerauders group,much discussion about using a wingspar that was built
and purchased by another builder. The Emeraud spar consists of 2
laminated built ip beams,w ply intercoastals, and boxed front and rear
w/ply. The spar in question was made with vertical grain wood, and
laminated with the grain perpendicular relative to the wing chord, I
believe the spar caps and laminations should have grain approx.
parallel to the wing chord. If anyone has a definitive answer that may
even prevent an accident go yo yahoo groups,emerauders


You might look at what some of the old timers did--NACA server
http://naca.larc.nasa.gov/search.jsp?No=10&Ne=26&N=17+45+269&Ns=HarvestDate| 1&as=false


strength of one-piece solid, build-up and laminated wood airplane wing beams

Author(s): Nelson, John H
Abstract: The purpose of this report is to summarize the results of all
wood airplane wing beams tested to date in the Bureau of Standards
Laboratory in order that the various kinds of wood and methods of
construction may be compared. ...
NASA Center: NASA (non Center Specific)
Publication Year: 1920=========================(=Lookie here ---1920!!!)
Added to NTRS: 2006-11-06
Accession Number: 93R20355; Document ID: 19930091065; Report Number:
NACA-TR-35



If you are interested--I can give you a blow by blow of how to get
there--or you can write the help desk--as I did.. Jerry

cmyr wrote:

As I recall , the horizontal grain orientation is preferred because
the adhesive has access to every layer of the wood in the 2 sparcaps
when joined to the front/rear ply webs. With vertical oriented caps,
only the front/rear wood layers would carry all the loads to the ply
webs when assembled.


Though this seems like a sensible choice, I thought I would look in CAM
18 (repair procedures) which is now all but 50 years old, an FAA
publication long out of print, except through the EAA. It has useful
guidance on the repair of wood spars. It makes the point that glued
scarf joints should run parallel to the general direction of the grain
(sec 18.30-2(b)(2) page 6.

If that rule were applied to the web/cap interface, it seems to advocate
a vertical grain in the cap.
Diagrams of preferred joints also seem to show grain as diagonal in caps
and solid spars..... It advocates face grain in the ply webs of box
spars running in the long direction of the spar.

Brian W

Jerry Wass wrote:

[cmyr]
... The spar in question was made with vertical grain wood, and
laminated with the grain perpendicular relative to the wing chord

[Jerry]
You might look at what some of the old timers did--NACA server
http://naca.larc.nasa.gov/search.jsp?No=10&Ne=26&N=17+45+269&Ns=HarvestDate| 1&as=false



[NACA]
strength of one-piece solid, build-up and laminated wood airplane wing
beams

Author(s): Nelson, John H
Abstract: The purpose of this report is to summarize the results of all
wood airplane wing beams tested to date in the Bureau of Standards
Laboratory in order that the various kinds of wood and methods of
construction may be compared. ...
NASA Center: NASA (non Center Specific)
Publication Year: 1920=========================(=Lookie here ---1920!!!)
Added to NTRS: 2006-11-06
Accession Number: 93R20355; Document ID: 19930091065; Report Number:
NACA-TR-35



If you are interested--I can give you a blow by blow of how to get
there--or you can write the help desk--as I did.. Jerry

This is how I viewed it:

http://naca.larc.nasa.gov/search.jsp?R=961129&id=1&as=false&or=true&qs=Ntt%3 Dnaca-tr-35%26Ntk%3Dall%26Ntx%3Dmode%2Bmatchall%26Ns%3DHarv estDate%257c1%26N%3D286

Despite the angle brackets I placed round the long URL above, it is
almost certain to break when I mail it. Thanks to TINYurl, this is the
short form:
http://tinyurl.com/l4aaxp
Click "View PDF file" (half way down the page with the abstract of
NACA-TR-35 for the online version.)

Notice in the comparison of alternate woods and alternate lamination and
build up methods, the solid I beam is shown with a curved largely
vertical grain orientation in cross section. (Think that was page 357?)

Regards


Brian W

"Brian Whatcott" wrote

Despite the angle brackets I placed round the long URL above, it is almost
certain to break when I mail it. Thanks to TINYurl, this is the short
form:
http://tinyurl.com/l4aaxp
Click "View PDF file" (half way down the page with the abstract of
NACA-TR-35 for the online version.)

Notice in the comparison of alternate woods and alternate lamination and
build up methods, the solid I beam is shown with a curved largely vertical
grain orientation in cross section. (Think that was page 357?)
I got a radiator article when that link was tried. How about this one:

http://naca.larc.nasa.gov/search.jsp?Ns=HarvestDate|1&N=17+45+269&Ntk=all&Nt x=mode%20matchall&Ntt=NACA-TR-35
--
Jim in NC

Morgans wrote:


"Brian Whatcott" wrote

Despite the angle brackets I placed round the long URL above, it is
almost certain to break when I mail it. Thanks to TINYurl, this is the
short form:
http://tinyurl.com/l4aaxp
Click "View PDF file" (half way down the page with the abstract of
NACA-TR-35 for the online version.)

Notice in the comparison of alternate woods and alternate lamination
and build up methods, the solid I beam is shown with a curved largely
vertical grain orientation in cross section. (Think that was page 357?)
I got a radiator article when that link was tried. How about this one:

http://naca.larc.nasa.gov/search.jsp?Ns=HarvestDate|1&N=17+45+269&Ntk=all&Nt x=mode%20matchall&Ntt=NACA-TR-35


Darn it - you're right! But your URL gets me there....

BrianW

Careful here. That paper was published in 1920!

OK, wood hasn't changed much, but what adhesive are they using? I didn't see
that mentioned.
I'm under the impression that modern epoxy (like West Systems) is stronger
than the parent wood .
That would make a laminated beam a much better idea than this study seems to
show..

Anybody know anything about this?




"cmyr" wrote in message
...
In my effort to learn/remember/practice correct building
procedures,I monitor several wood aircraft design sights. In the
emerauders group,much discussion about using a wingspar that was built
and purchased by another builder. The Emeraud spar consists of 2
laminated built ip beams,w ply intercoastals, and boxed front and rear
w/ply. The spar in question was made with vertical grain wood, and
laminated with the grain perpendicular relative to the wing chord, I
believe the spar caps and laminations should have grain approx.
parallel to the wing chord. If anyone has a definitive answer that may
even prevent an accident go yo yahoo groups,emerauders