Wood grain orientation in a built-up spar

[cmyr]

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

[Orval Fairbairn[_2_]]

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.

[Brian Whatcott]

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

[cmyr]

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.

[jerry wass]

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

[Brian Whatcott]

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

[Brian Whatcott]

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%3Dnaca-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

[Morgans[_7_]]

"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&Ntx=mode%20matchall&Ntt=NACA-TR-35>
--
Jim in NC

[Brian Whatcott]

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&Ntx=mode%20matchall&Ntt=NACA-TR-35>
>

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

BrianW

[Ron Webb]

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

[Ron Webb]

Seems like the grain in any wood structure should be the same direction it
was in the tree.
Why would the gods do it wrong?

In a wood bow, they use "quarter sawn" blanks. This ends up with the grain
oriented as above. along the length.





"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

[Bob]

On Jun 28, 2:18*pm, "Ron Webb" > wrote:

>
> 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..
-------------------------------------------------------------------------------------

Dear Ron,

It doesn't matter WHAT glue they used, it would still be stronger than
the softwoods we normally use.

This is kinda like the Horsepower Myth, where everyone goes around
citing HORSEPOWER when they should be thinking in terms of torque and
thrust.

So your epoxy is stronger than your wood. Big deal; so's casein, hide
glue, Plastic Resin and even Elmer's vinyl resin. The point here is
that we don't pick our adhesive for it's STRENGTH but for some other
characteristic.

-R.S.Hoover

[jerry wass]

Ron Webb wrote:
> Seems like the grain in any wood structure should be the same direction it
> was in the tree.
> Why would the gods do it wrong?
>
> In a wood bow, they use "quarter sawn" blanks. This ends up with the grain
> oriented as above. along the length.
>
>
>
>
>
> "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
>
>
Ron, read the next to last line--He believes, as do I, that the top &
bottom caps should have their grain parallel to the CHORD , with
the sides of the box extend the full ht of the spar, thus bonding to
every layer of the top & bottom caps--in this case the caps are not true
caps, but are the top & bottom members of the beam---of course the top &
bottom members have the grain running the LENGTH of the spar also..Jerry

This would be a FLAT sawn board rather than a qtr sawn-edge grain- board
which would probably have to be laminated itself to oppose warpage which
you cannot escape in flat sawn wood otherwise.

[Stealth Pilot[_2_]]

On Fri, 26 Jun 2009 00:08:28 GMT, Jerry Wass >
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
>
>
>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

get the nasa web site up http://naca.larc.nasa.gov and search on the
document id number and you will go straight to it.
Stealth Pilot