Today's Message Index:
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1. 05:07 AM - 3 Piece Wing Question (GrantZ)
2. 05:51 AM - Re: 3 Piece Wing Question (Jack Phillips)
3. 08:00 AM - Re: 3 Piece Wing Question (AircamperN11MS)
4. 11:39 AM - Re: 3 Piece Wing Question (Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC])
5. 12:14 PM - Re: 3 Piece Wing Question (Steven Dortch)
6. 12:25 PM - Re: 3 Piece Wing Question (Ken Bickers)
7. 12:29 PM - Re: 3 Piece Wing Question (Boatright, Jeffrey)
8. 01:19 PM - Re: 3 Piece Wing Question (Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC])
9. 01:33 PM - Re: 3 Piece Wing Question (Jack Phillips)
10. 01:42 PM - Re: 3 Piece Wing Question (Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC])
11. 01:51 PM - Re: progress on Scout (taildrags)
12. 07:27 PM - Re: Re: progress on Scout (Gary Boothe)
13. 07:57 PM - Re: 3 Piece Wing Question (Clif Dawson)
14. 08:56 PM - Re: 3 Piece Wing Question (taildrags)
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Subject: | 3 Piece Wing Question |
Tail feathers completed. Basic fuselage frame-up completed. 15 ribs done.
Learning to TIG weld all over again!
Starting wing construction. 3 piece plans state that the center section and outer
panel spar ends butt together with "0 clearance at assembly. How does one
cut the spar ends accurately enough to achieve this and not introduce any dihedral
or anhedral when assembled (i.e. flat panel from tip to tip)? Can shims
be used at final assembly to get proper alignment?
Does the lack of any fitting holding the upper edges of the spars together bother
anyone but me? Lots of these craft are flying with 3 piece wings built to
the plans but it just to seems odd to me that the only thing keeping the spars
butted together is lift force and any preload provided by the lift strut. What
am I missing here?
Grant Ziebell
Savannah, TN
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=422879#422879
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Subject: | 3 Piece Wing Question |
Grant,
Don't worry about it. The spars need to butt together to carry the
considerable compressive load between the main spars and the
centersection spar.
Since the lift struts attach at the center of the wing panels, virtually
all of the lift load is carried by the lift struts. However, since they
attach at about a 30=C2=B0 angle, if each lift strut is carrying 500 lbs
of lift (vertical component) the tensile load carried by the lift strut
on each side is 1000 lbs down the line of the strut, which means the
lift strut is pulling the wing horizontally (towards the centersection)
with a tensile force of 866 lbs. This is the compressive force between
the wing spars and the centersection spars.
By letting the spars butt together, the whole cross-sectional area of
the spar is available to help carry this load. If you are using
=C2=BE=9D spars 4-3/4=9D tall, the area is 3.56 sq inches,
so the compressive stress is 866/3.56 or 243 psi, which spruce can
easily carry. If you put a bolted fitting there to carry this load, you
are now reducing the area to carry it to the width of the spar x the
diameter of the bolt. Assuming you use a 5/16=9D bolt, this area
is .23 sq inches, and the compressive stress induced in the wood is now
866/.23 or 3,694 psi, which is getting pretty close to the limit for
spruce (spruce can carry 4200 psi compressive stress parallel to the
grain, according to the tables found in
http://www.recreationalflying.com/tutorials/scratchbuilder/wood_strength_
values.html .
As for adding dihedral, unless you are wanting significant dihedral, you
can just flex the wing enough to add up to a degree or two. I have
about =C2=BD degree of dihedral per side on mine =93 just enough
to avoid the illusion of drooping wings (if such an illusion actually
exists) that some say a perfectly straight wing causes.
Besides, having just one attach bolt per spar makes it MUCH easier to
attach and remove the wing panels, rather than having to line up four
bolts simultaneously. With just one bolt per spar, the wingtip can
actually be left on the ground and the spars attached, before lifting
the wing and attaching the lift struts.
As has often been said before on this site: =9CBuild it to the
plans=9D.
Good Luck!
Jack Phillips
NX899JP
Smith Mountain Lake, Virginia
-----Original Message-----
From: owner-pietenpol-list-server@matronics.com
[mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of GrantZ
Sent: Tuesday, May 06, 2014 8:07 AM
Subject: Pietenpol-List: 3 Piece Wing Question
Tail feathers completed. Basic fuselage frame-up completed. 15 ribs
done.
Learning to TIG weld all over again!
Starting wing construction. 3 piece plans state that the center section
and outer panel spar ends butt together with "0 clearance at
assembly=C3=A2=82=AC=C5=93. How does one cut the spar ends
accurately enough to achieve this and not introduce any dihedral or
anhedral when assembled (i.e. flat panel from tip to tip)? Can shims
be used at final assembly to get proper alignment?
Does the lack of any fitting holding the upper edges of the spars
together bother anyone but me? Lots of these craft are flying with 3
piece wings built to the plans but it just to seems odd to me that the
only thing keeping the spars butted together is lift force and any
preload provided by the lift strut. What am I missing here?
Grant Ziebell
Savannah, TN
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=422879#422879
Message 3
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Subject: | Re: 3 Piece Wing Question |
Fantastic answer to his question. The only thing I can add is that (as far as
I know) that there has NEVER been an in flight structural failure of a Pietenpol.
Just build it to the plans and feel very safe in it during all phases of
flight.
Happy landings,
--------
Scott Liefeld
Flying N11MS since March 1972
Steel Tube
C-85-12
Wire Wheels
Brodhead in 1996
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=422887#422887
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Subject: | 3 Piece Wing Question |
Grant,
My center section spars and L & R wing panel spar ends do not butt up again
st each other. I respect Jack Phillips mechanical load analysis as he is
a professional mechanical/aerotype
engineer but when I made up my center section spar ends I intentionally cut
a small angle inward at the top on each of them so I could pivot the outer
wing panels upward just a little
because I wanted dihedral. I would doubt that very few Pietenpols with 3
-piece wings have really good and full contact between the CC butt spar end
s and the outer wing panel spar
ends so I assume (after flying mine for the past 16 years) that the metal f
ittings and bolts which join the CC and wing panels together is sufficient
to take the loads given that I know for
a fact my spar ends are not flush against each other.
Mike C.
Ohio
Message 5
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Subject: | Re: 3 Piece Wing Question |
Mike your plane must be unairworthy. Please box it up and ship it to me and
I will deal with disposal. ;+}
Blue Skies,
Steve D
Message 6
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Subject: | Re: 3 Piece Wing Question |
I fear the repercussions when the Top Curmudgeon and associated Council of
Curmudgeons get wind of MC's deviation from the plans. The masses will
certainly be disconcerted.
On Tue, May 6, 2014 at 1:13 PM, Steven Dortch <steven.d.dortch@gmail.com>wrote:
>
> Mike your plane must be unairworthy. Please box it up and ship it to me
> and I will deal with disposal. ;+}
>
> Blue Skies,
> Steve D
>
>
> *
>
>
> *
>
>
Message 7
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Subject: | Re: 3 Piece Wing Question |
I=92ll do you one better. My spar ends are at least an inch apart from one
another. I=92m out of town and so cannot send photos, but my spars have met
al straps that extend several inches down the length of the spars, with bol
ts through the spars and straps. At the spar ends, the straps extend about
an inch and go from a rectangle to a triangle. The tips of the triangles ov
erlap and a bolt runs through that overlap. Sort of like this:
=97=97=97=97 =97=97=97=97
Center \ / Wing =97>
Section / \
=97=97=97=97 =97=97=97=97
Don=92t know if it=92s safe, but the plane has been flying that way since 1
978.
--
Jeffrey H. Boatright, PhD, FARVO
Professor of Ophthalmology
Emory University School of Medicine
From: <Cuy>, "LLC]" <michael.d.cuy@nasa.gov<mailto:michael.d.cuy@nasa.gov>>
>" <pietenpol-list@matronics.com<mailto:pietenpol-list@matronics.com>>
etenpol-list@matronics.com<mailto:pietenpol-list@matronics.com>>
Subject: RE: Pietenpol-List: 3 Piece Wing Question
Grant,
My center section spars and L & R wing panel spar ends do not butt up again
st each other. I respect Jack Phillips mechanical load analysis as he is
a professional mechanical/aerotype
engineer but when I made up my center section spar ends I intentionally cut
a small angle inward at the top on each of them so I could pivot the outer
wing panels upward just a little
because I wanted dihedral. I would doubt that very few Pietenpols with 3
-piece wings have really good and full contact between the CC butt spar end
s and the outer wing panel spar
ends so I assume (after flying mine for the past 16 years) that the metal f
ittings and bolts which join the CC and wing panels together is sufficient
to take the loads given that I know for
a fact my spar ends are not flush against each other.
Mike C.
Ohio
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Message 8
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Subject: | 3 Piece Wing Question |
I know of Piet spars (one on a flying Scout) that have notches dug into the
m in order for the wing strut attach 'straddle' fitting to go low
enough so the bottom of the fitting fit thru the fabric of the lower wing e
nough to bolt on the four lift struts........I've seen others that have
Piet spars with a cut in them for various other reasons as well.
Now this 1" gap Jeff Boatright.....I'm jealous. My gap is only about a =BC
" between butt spar ends and wing panel spar ends. And yours has been
flying since 1978? Nice!
Mike C.
Ohio
Message 9
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Subject: | 3 Piece Wing Question |
You and Jeff Boatright have apparently cheated death every time you have
flown!
Obviously, the strap type fittings spread the loads sufficiently through
the
wood of the spar to lower the stress to safe levels. The numbers I ran
this
morning assumed that the top fitting would just be a bolt through the
spar,
which would be marginal at best.
My point to Grant was that if built to the plans, the spar is as strong
with
just one bolt securing it as it needs to be, and no extra concerns are
necessary to add a slight amount of dihedral or washout ' just do it
with
the lift struts.
Jack Phillips
NX899JP
Smith Mountain Lake, Virginia
_____
From: owner-pietenpol-list-server@matronics.com
[mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Cuy,
Michael
D. (GRC-RXD0)[Vantage Partners, LLC]
Sent: Tuesday, May 06, 2014 4:19 PM
Subject: RE: Pietenpol-List: 3 Piece Wing Question
I know of Piet spars (one on a flying Scout) that have notches dug into
them
in order for the wing strut attach =91straddle=92 fitting to go low
enough so the bottom of the fitting fit thru the fabric of the lower
wing
enough to bolt on the four lift struts=85=85..I=92ve seen others that
have
Piet spars with a cut in them for various other reasons as well.
Now this 1=94 gap Jeff Boatright=85..I=92m jealous. My gap is only
about a =BC=94
between butt spar ends and wing panel spar ends. And yours has been
flying since 1978? Nice!
Mike C.
Ohio
Message 10
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Subject: | 3 Piece Wing Question |
You and Jeff Boatright have apparently cheated death every time you have fl
own!
That is such a true statement, at least for me, Jack and it has nothing to
do with my wing spars.....just my nature as a pilot sometimes!
Looks like I picked a bad week to stop amphetamines.
McCrosky: 'Johnny, how bout some coffee?'
Johnny: 'no thanks.'
Rapunzel, the Tower, the Tower!!!
[cid:image001.jpg@01CF694A.2A9EA490]
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Subject: | Re: progress on Scout |
So I got over to the hangar for just a few minutes today and pulled the airplane
out into the sun. Tied down the tail, turned on the fuel, and pulled the engine
through four blades. Made the mags hot and then propped it off with gusto.
It fired on about the 4th arm, which isn't bad considering the carb has just
been overhauled and fuel had to make its way into all the passageways and ports.
Warmed it up and then hesitatingly applied throttle to see if it was going
to gag and cough without pulling carb heat. It did not. Power ran up, ran
down, and idle is smooth. I shut it down and will play with it some more this
weekend, but it appears to be ready to put the cowling back on and resume taxi
testing. If all goes well, I should get some air under the wings on Saturday.
Oh, yeah, and a quick check of the new main seal confirmed that it's bone dry,
so hopefully no more oil mist after the oil gets good and hot and thin. I'll
find out after I can fly it for at least a few circuits of the field.
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=422922#422922
Message 12
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Subject: | Re: progress on Scout |
Well done, Oscar!
Gary Boothe
NX308MB
-----Original Message-----
From: owner-pietenpol-list-server@matronics.com
[mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of taildrags
Sent: Tuesday, May 06, 2014 1:52 PM
Subject: Pietenpol-List: Re: progress on Scout
--> <taildrags@hotmail.com>
So I got over to the hangar for just a few minutes today and pulled the
airplane out into the sun. Tied down the tail, turned on the fuel, and
pulled the engine through four blades. Made the mags hot and then propped
it off with gusto. It fired on about the 4th arm, which isn't bad
considering the carb has just been overhauled and fuel had to make its way
into all the passageways and ports. Warmed it up and then hesitatingly
applied throttle to see if it was going to gag and cough without pulling
carb heat. It did not. Power ran up, ran down, and idle is smooth. I shut
it down and will play with it some more this weekend, but it appears to be
ready to put the cowling back on and resume taxi testing. If all goes well,
I should get some air under the wings on Saturday.
Oh, yeah, and a quick check of the new main seal confirmed that it's bone
dry, so hopefully no more oil mist after the oil gets good and hot and thin.
I'll find out after I can fly it for at least a few circuits of the field.
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=422922#422922
Message 13
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Subject: | Re: 3 Piece Wing Question |
Lady to tigermoth pilot. "Is this old plane safe to fly?"
Pilot replies, " Lady, how do you think this plane
got to be so old?"
Clif
Worry gives a small thing a big shadow.
Swedish proverb
All great truths begin as blasphemies.
George Bernard Shaw
----- Original Message -----
From: Cuy, Michael D. (GRC-RXD0)[Vantage Partners,
You and Jeff Boatright have apparently cheated death every time you
have flown!
That is such a true statement, at least for me, Jack and it has
nothing to do with my wing spars...just my nature as a pilot sometimes!
Message 14
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Subject: | Re: 3 Piece Wing Question |
Wow. Wow! I felt my legs start to quiver and turn to jelly as I read about the
spar ends having to butt with zero clearance at the centersection spars. That
is, until I read Mikee's comforting post! And Jeff's! Whew... and I was just
about to take the chainsaw to poor old Scout for being of questionable integrity.
I just re-hung the wings recently, and if memory serves, there is a generous
gap between the main spar and centersection spar butts. Very similar to
what Jeff describes for his setup. So... reading Jack's stress analysis, the
wing spar attach bolts on my wings carry all of the loads in single shear, because
there is no continuous path between inner and outer spars through the wood.
I'll have to analyze what those stresses might be, although I just replaced
all the wing and strut attach bolts/nuts and those particular ones showed
no distress and certainly didn't have any shear deformation on them.
As far as dihedral, just a few days ago I sighted down the trailing edge of my
wing, from wingtip to wingtip, for the very reason that the dihedral distinctly
transitions down one wing, to perfectly flat at the centersection flop, and
back up as it goes out to the opposite tip. I thought it looked a little curious
at the time, almost like where a bird's wings join its body. I have stretched
a cord between the wingtips once upon a time and in the middle, the cord
stood 3" above the centersection. Scout may not have the most dihedral of any
Air Camper out there, but it does have more than many.
I'm thinking we need to have one of the artists among us create a special decal
or patch that can only be worn by "cheaters of death" like us. We need a catchy
motto, too, like "I Made The Cut/My Spars Don't Butt". I'll leave the graphics
up to your imagination.
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=422939#422939
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