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victorbravo(at)sbcglobal.
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 Posted: Mon Mar 21, 2016 9:55 am Post subject: Elevator/Stabilizer hinge ass'y |
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Are there any Kolb people on this list who are qualified mechanical or aero-structure engineers? I want to ask a question about the tail attachment mechanism.
Before I even mention the question, I want to assure everyone that I AM COMPLETELY AWARE that there are X thousand Kolbs flying around safely with this stabilizer attachment. I understand that there have not been many (or perhaps any) failures of this mechanism. What I am asking about is the theoretical "correctness" of the design, and whether any other "old-school" airplane people think that this system is a little wonky.
It took a few moments to finally understand how the mechanism works, and after looking at everything several times it was clear that there is no direct structural attachment between the main spar tube of the stabilizer to the fuselage tube (tailboom). The primary structural load path between the root end of the main stabilizer spar tube and the fuselage is transmitted through the elevator hinge... and this hinge isn't even the aircraft style extruded hinge.
So if the air loads try to lift up or push down on the root end of the stabilizer, it puts all that load through the hinge, into the elevator pivot, and then finally into the steel ring at the back of the fuselage.
But that's not even the biggest issue in my head. The larger issue is that (according to plan) the flat hinge is riveted to the tubes along one thin "point of contact" line tangent to the tube. So the root stabilizer load is all acting on a hinge, which itself is cantilevered off of one tangent point on the tube.
Now I'm not a degreed engineer, and I'm not a mathematician. So I called a friend of mine who is a retired aerospace structural engineer, with 50+ years of experience. I showed him the plans and explained my concern, and I was informed that my concerns about this system were valid. My Kolb will be built with a more stable attachment.
My question for any real, degreed, qualified, aircraft-experience engineers is... has anyone looked at the stabilizer root attachment load path and had these same concerns?
ONCE AGAIN, this is not an attack on Mr. Kolb or his design, and it is not intended to cause any panic or concern at this point. What I want to know is why this load path - through two tangent mounted hinge halves, into a movable elevator, and then into the fuselage - is good enough, and why it was not appropriate to install an attachment bracket onto the fuselage at the rear stabilizer spar.
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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| Posted: Mon Mar 21, 2016 1:40 pm Post subject: Elevator/Stabilizer hinge ass'y |
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The rear attachment of the horizontal stabilizer is NOT through the hinge. It is through the rear folding weldments that also act as the inner hinge. When it is set up correctly the hinge line is on the same center as the swivel bolt in the weldment, however there is some allowance for misalignment. In that case the weldment in the elevator spar (forward tube of the elevator), can slide on the bolt in the swivel weldment.I've seen folding mechanisms on the Kit Fox and repaired the mechanism on the Highlander and in my HO Homer's is the most clever. All you have to do to fold the HS on a Kolb is to take out a single bolt that attaches the lower wires to the rudder post. I'm not sure how you would make it any simpler.
Rick Girard
On Mon, Mar 21, 2016 at 12:55 PM, Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)> wrote:
| Quote: | --> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>
Are there any Kolb people on this list who are qualified mechanical or aero-structure engineers? I want to ask a question about the tail attachment mechanism.
Before I even mention the question, I want to assure everyone that I AM COMPLETELY AWARE that there are X thousand Kolbs flying around safely with this stabilizer attachment. I understand that there have not been many (or perhaps any) failures of this mechanism. What I am asking about is the theoretical "correctness" of the design, and whether any other "old-school" airplane people think that this system is a little wonky.
It took a few moments to finally understand how the mechanism works, and after looking at everything several times it was clear that there is no direct structural attachment between the main spar tube of the stabilizer to the fuselage tube (tailboom). The primary structural load path between the root end of the main stabilizer spar tube and the fuselage is transmitted through the elevator hinge... and this hinge isn't even the aircraft style extruded hinge.
So if the air loads try to lift up or push down on the root end of the stabilizer, it puts all that load through the hinge, into the elevator pivot, and then finally into the steel ring at the back of the fuselage.
But that's not even the biggest issue in my head. The larger issue is that (according to plan) the flat hinge is riveted to the tubes along one thin "point of contact" line tangent to the tube. So the root stabilizer load is all acting on a hinge, which itself is cantilevered off of one tangent point on the tube.
Now I'm not a degreed engineer, and I'm not a mathematician. So I called a friend of mine who is a retired aerospace structural engineer, with 50+ years of experience. I showed him the plans and explained my concern, and I was informed that my concerns about this system were valid. My Kolb will be built with a more stable attachment.
My question for any real, degreed, qualified, aircraft-experience engineers is... has anyone looked at the stabilizer root attachment load path and had these same concerns?
ONCE AGAIN, this is not an attack on Mr. Kolb or his design, and it is not intended to cause any panic or concern at this point. What I want to know is why this load path - through two tangent mounted hinge halves, into a movable elevator, and then into the fuselage - is good enough, and why it was not appropriate to install an attachment bracket onto the fuselage at the rear stabilizer spar.
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
===========
br> fts!)
r> > w.buildersbooks.com" rel="noreferrer" target="_blank">www.buildersbooks.com
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Eugene Zimmerman
Joined: 10 Jan 2006
Posts: 392
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zeprep251(at)aol.com
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| Posted: Mon Mar 21, 2016 2:28 pm Post subject: Elevator/Stabilizer hinge ass'y |
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Have to realize Bill,we are talking sub sonic here.A Kolb may not be what you’re looking for if you don’t care what it weighs.A TBM may be down your ally.I hear they’re pretty stout .Good luck finding a kit. | Quote: | On Mar 21, 2016, at 6:13 PM, Eugene Zimmerman <etzimm(at)gmail.com (etzimm(at)gmail.com)> wrote:
| Quote: | So I called a friend of mine who is a retired aerospace structural engineer, with 50+ years of experience.
|
LOL
The cognitive acuity of anyone with 50+ years of experience should probably be suspect.
Trust me, I have 50+ years of experience. 
|
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victorbravo(at)sbcglobal.
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| Posted: Mon Mar 21, 2016 2:30 pm Post subject: Elevator/Stabilizer hinge ass'y |
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I hope I'm wrong, but my review of the plans indicated that there is no traditional DIRECT structural connection between the rear spar tube and the fuselage tube. All the load paths have to take a serpentine route and go rearward through the elevator hinges first, and only then into the U-joint and pivot bolt in the steel ring. If you removed the elevator hinges (from either the elevator or the stabilizer), or if you took the pin out of the hinges, you could move the stabilizer up and down freely while the elevator remained bolted to the fuselage.
Even WITH all the hinges in place, all up and down movement of the stabilizer is transmitted through the rivets that hold the hinge onto the tubes, and there is no significant stiffness or bracing against this movement. Essentially you could move the root end of the stabilizer up and down by hand and this movement would bend the (un-supported section of) the hinge material. This would attempt to pry the rivets out of the tube and/or bend the thin metal back and forth.
Also, because of this design the forward stabilizer attach bolt must be a loose fit, and the stabilizer has to be able to slide back and forth a little.
The only thing that is gained by this unusual structural load path is that 4 ounces of weight for a pair of fittings (at the rear stabilizer spar) is saved. Can any one explain to me why this was a good bargain?
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
--------------------------------------------
On Mon, 3/21/16, Richard Girard <aslsa.rng(at)gmail.com> wrote:
Subject: Re: Elevator/Stabilizer hinge ass'y
To: "kolb-list(at)matronics.com" <kolb-list(at)matronics.com>
Date: Monday, March 21, 2016, 2:40 PM
The rear attachment
of the horizontal stabilizer is NOT through the hinge. It is
through the rear folding weldments that also act as the
inner hinge. When it is set up correctly the hinge line is
on the same center as the swivel bolt in the weldment,
however there is some allowance for misalignment. In that
case the weldment in the elevator spar (forward tube of the
elevator), can slide on the bolt in the swivel
weldment.I've seen folding mechanisms on the Kit
Fox and repaired the mechanism on the Highlander and in my
HO Homer's is the most clever. All you have to do to
fold the HS on a Kolb is to take out a single bolt that
attaches the lower wires to the rudder post. I'm not
sure how you would make it any simpler.
Rick Girard
On Mon, Mar 21, 2016
at 12:55 PM, Bill Berle <victorbravo(at)sbcglobal.net>
wrote:
Bill Berle <victorbravo(at)sbcglobal.net>
Are there any Kolb people on this list who are qualified
mechanical or aero-structure engineers? I want to ask a
question about the tail attachment mechanism.
Before I even mention the question, I want to assure
everyone that I AM COMPLETELY AWARE that there are X
thousand Kolbs flying around safely with this stabilizer
attachment. I understand that there have not been many (or
perhaps any) failures of this mechanism. What I am asking
about is the theoretical "correctness" of the
design, and whether any other "old-school"
airplane people think that this system is a little wonky.
It took a few moments to finally understand how the
mechanism works, and after looking at everything several
times it was clear that there is no direct structural
attachment between the main spar tube of the stabilizer to
the fuselage tube (tailboom). The primary structural load
path between the root end of the main stabilizer spar tube
and the fuselage is transmitted through the elevator
hinge... and this hinge isn't even the aircraft style
extruded hinge.
So if the air loads try to lift up or push down on the root
end of the stabilizer, it puts all that load through the
hinge, into the elevator pivot, and then finally into the
steel ring at the back of the fuselage.
But that's not even the biggest issue in my head. The
larger issue is that (according to plan) the flat hinge is
riveted to the tubes along one thin "point of
contact" line tangent to the tube. So the root
stabilizer load is all acting on a hinge, which itself is
cantilevered off of one tangent point on the tube.
Now I'm not a degreed engineer, and I'm not a
mathematician. So I called a friend of mine who is a retired
aerospace structural engineer, with 50+ years of experience.
I showed him the plans and explained my concern, and I was
informed that my concerns about this system were valid. My
Kolb will be built with a more stable attachment.
My question for any real, degreed, qualified,
aircraft-experience engineers is... has anyone looked at the
stabilizer root attachment load path and had these same
concerns?
ONCE AGAIN, this is not an attack on Mr. Kolb or his design,
and it is not intended to cause any panic or concern at this
point. What I want to know is why this load path - through
two tangent mounted hinge halves, into a movable elevator,
and then into the fuselage - is good enough, and why it was
not appropriate to install an attachment bracket onto the
fuselage at the rear stabilizer spar.
Bill Berle
www.ezflaphandle.com
- safety & performance upgrade for light aircraft
www.grantstar.net
- winning proposals for non-profit and for-profit
entities
===========
br>
fts!)
r>
>
w.buildersbooks.com" rel="noreferrer"
target="_blank">www.buildersbooks.com
rel="noreferrer"
target="_blank">http://www.matronics.com/contribution
-Matt Dralle, List Admin.
===========
-List" rel="noreferrer"
target="_blank">http://www.matronics.com/Navigator?Kolb-List
===========
FORUMS -
eferrer"
target="_blank">http://forums.matronics.com
===========
b Site -
-Matt Dralle, List Admin.
rel="noreferrer"
target="_blank">http://www.matronics.com/contribution
===========
--
“Blessed
are the cracked, for they shall let in the light.” Groucho
Marx
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kolb-List |
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victorbravo(at)sbcglobal.
Guest
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| Posted: Mon Mar 21, 2016 2:31 pm Post subject: Elevator/Stabilizer hinge ass'y |
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Understood, but in this case the person in question is sharp as a tack. It's MY cognitive acuity that is suspect !
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
--------------------------------------------
On Mon, 3/21/16, Eugene Zimmerman <etzimm(at)gmail.com> wrote:
Subject: Re: Elevator/Stabilizer hinge ass'y
To: "Kolb list" <kolb-list(at)matronics.com>
Date: Monday, March 21, 2016, 3:13 PM
On Mar 21,
2016, at 1:55 PM, Bill Berle <victorbravo(at)sbcglobal.net>
wrote:
So I called a friend of mine who is a
retired aerospace structural engineer, with 50+ years of
experience.
LOL
The cognitive acuity of anyone with
50+ years of experience should probably be
suspect.Trust me, I have
50+ years of experience.
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kolb-List |
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rowedenny
Joined: 09 Mar 2008
Posts: 338
Location: Western PA
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| Posted: Tue Mar 22, 2016 9:03 am Post subject: Elevator/Stabilizer hinge ass'y |
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|
Somebody notify John Hauck, as Miss Pfer has around 4000 hours on her airframe and has taken an eighty horse and two 100 horse Rotax 912 engines well toward their TBO! The horizontal stabilizer must be ready to fall off at any second.
Maybe I can get a good deal on her since her demise must be imminent. 😉
Bill, just build the dang Firestar to plans and fly it. It won't fall apart.
Dennis "Skid" Rowe
Mk-3 Rotax 690, with a stock Kolb empennage.😱
| Quote: | On Mar 21, 2016, at 6:29 PM, Bill Berle <victorbravo(at)sbcglobal.net> wrote:
I hope I'm wrong, but my review of the plans indicated that there is no traditional DIRECT structural connection between the rear spar tube and the fuselage tube. All the load paths have to take a serpentine route and go rearward through the elevator hinges first, and only then into the U-joint and pivot bolt in the steel ring. If you removed the elevator hinges (from either the elevator or the stabilizer), or if you took the pin out of the hinges, you could move the stabilizer up and down freely while the elevator remained bolted to the fuselage.
Even WITH all the hinges in place, all up and down movement of the stabilizer is transmitted through the rivets that hold the hinge onto the tubes, and there is no significant stiffness or bracing against this movement. Essentially you could move the root end of the stabilizer up and down by hand and this movement would bend the (un-supported section of) the hinge material. This would attempt to pry the rivets out of the tube and/or bend the thin metal back and forth.
Also, because of this design the forward stabilizer attach bolt must be a loose fit, and the stabilizer has to be able to slide back and forth a little.
The only thing that is gained by this unusual structural load path is that 4 ounces of weight for a pair of fittings (at the rear stabilizer spar) is saved. Can any one explain to me why this was a good bargain?
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
--------------------------------------------
On Mon, 3/21/16, Richard Girard <aslsa.rng(at)gmail.com> wrote:
Subject: Re: Elevator/Stabilizer hinge ass'y
To: "kolb-list(at)matronics.com" <kolb-list(at)matronics.com>
Date: Monday, March 21, 2016, 2:40 PM
The rear attachment
of the horizontal stabilizer is NOT through the hinge. It is
through the rear folding weldments that also act as the
inner hinge. When it is set up correctly the hinge line is
on the same center as the swivel bolt in the weldment,
however there is some allowance for misalignment. In that
case the weldment in the elevator spar (forward tube of the
elevator), can slide on the bolt in the swivel
weldment.I've seen folding mechanisms on the Kit
Fox and repaired the mechanism on the Highlander and in my
HO Homer's is the most clever. All you have to do to
fold the HS on a Kolb is to take out a single bolt that
attaches the lower wires to the rudder post. I'm not
sure how you would make it any simpler.
Rick Girard
On Mon, Mar 21, 2016
at 12:55 PM, Bill Berle <victorbravo(at)sbcglobal.net>
wrote:
Bill Berle <victorbravo(at)sbcglobal.net>
Are there any Kolb people on this list who are qualified
mechanical or aero-structure engineers? I want to ask a
question about the tail attachment mechanism.
Before I even mention the question, I want to assure
everyone that I AM COMPLETELY AWARE that there are X
thousand Kolbs flying around safely with this stabilizer
attachment. I understand that there have not been many (or
perhaps any) failures of this mechanism. What I am asking
about is the theoretical "correctness" of the
design, and whether any other "old-school"
airplane people think that this system is a little wonky.
It took a few moments to finally understand how the
mechanism works, and after looking at everything several
times it was clear that there is no direct structural
attachment between the main spar tube of the stabilizer to
the fuselage tube (tailboom). The primary structural load
path between the root end of the main stabilizer spar tube
and the fuselage is transmitted through the elevator
hinge... and this hinge isn't even the aircraft style
extruded hinge.
So if the air loads try to lift up or push down on the root
end of the stabilizer, it puts all that load through the
hinge, into the elevator pivot, and then finally into the
steel ring at the back of the fuselage.
But that's not even the biggest issue in my head. The
larger issue is that (according to plan) the flat hinge is
riveted to the tubes along one thin "point of
contact" line tangent to the tube. So the root
stabilizer load is all acting on a hinge, which itself is
cantilevered off of one tangent point on the tube.
Now I'm not a degreed engineer, and I'm not a
mathematician. So I called a friend of mine who is a retired
aerospace structural engineer, with 50+ years of experience.
I showed him the plans and explained my concern, and I was
informed that my concerns about this system were valid. My
Kolb will be built with a more stable attachment.
My question for any real, degreed, qualified,
aircraft-experience engineers is... has anyone looked at the
stabilizer root attachment load path and had these same
concerns?
ONCE AGAIN, this is not an attack on Mr. Kolb or his design,
and it is not intended to cause any panic or concern at this
point. What I want to know is why this load path - through
two tangent mounted hinge halves, into a movable elevator,
and then into the fuselage - is good enough, and why it was
not appropriate to install an attachment bracket onto the
fuselage at the rear stabilizer spar.
Bill Berle
www.ezflaphandle.com
- safety & performance upgrade for light aircraft
www.grantstar.net
- winning proposals for non-profit and for-profit
entities
===========
br>
fts!)
r>
>
w.buildersbooks.com" rel="noreferrer"
target="_blank">www.buildersbooks.com
rel="noreferrer"
target="_blank">http://www.matronics.com/contribution
-Matt Dralle, List Admin.
===========
-List" rel="noreferrer"
target="_blank">http://www.matronics.com/Navigator?Kolb-List
===========
FORUMS -
eferrer"
target="_blank">http://forums.matronics.com
===========
b Site -
-Matt Dralle, List Admin.
rel="noreferrer"
target="_blank">http://www.matronics.com/contribution
===========
--
“Blessed
are the cracked, for they shall let in the light.” Groucho
Marx
|
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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victorbravo(at)sbcglobal.
Guest
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| Posted: Tue Mar 22, 2016 9:43 am Post subject: Elevator/Stabilizer hinge ass'y |
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I wish I could have placed a bet in Las Vegas as to how quickly some of the people would jump in and say that these airplanes have X number of hours and Y number of landings without failure. I would have been able to buy another Kolb 
With all due respect to everyone, I KNOW that these airplanes are not falling out of the sky.
Now, also with all due respect, can someone with engineering knowledge tell me, ON A TECHNICAL ENGINEERING level, how it could EVER be considered as good design practice to essentially cantilever a piano hinge off of a thin wall round tube, with one line of rivets at the tangent contact point, and with flight loads often perpendicular to that axis, where that cantilever loaded hinge is not only connecting two pieces of primary aircraft structure but also attaching a primary control surface ?
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
--------------------------------------------
On Tue, 3/22/16, Dennis Rowe <rowedenny(at)windstream.net> wrote:
Subject: Re: Elevator/Stabilizer hinge ass'y
To: kolb-list(at)matronics.com
Date: Tuesday, March 22, 2016, 9:59 AM
Dennis Rowe <rowedenny(at)windstream.net>
Somebody notify John Hauck, as Miss Pfer has around 4000
hours on her airframe and has taken an eighty horse and two
100 horse Rotax 912 engines well toward their TBO! The
horizontal stabilizer must be ready to fall off at any
second.
Maybe I can get a good deal on her since her demise must be
imminent. 😉
Bill, just build the dang Firestar to plans and fly it. It
won't fall apart.
Dennis "Skid" Rowe
Mk-3 Rotax 690, with a stock Kolb empennage.😱
> On Mar 21, 2016, at 6:29 PM, Bill Berle <victorbravo(at)sbcglobal.net>
wrote:
>
>
>
> I hope I'm wrong, but my review of the plans indicated
that there is no traditional DIRECT structural connection
between the rear spar tube and the fuselage tube. All the
load paths have to take a serpentine route and go rearward
through the elevator hinges first, and only then into the
U-joint and pivot bolt in the steel ring. If you removed the
elevator hinges (from either the elevator or the
stabilizer), or if you took the pin out of the hinges, you
could move the stabilizer up and down freely while the
elevator remained bolted to the fuselage.
>
> Even WITH all the hinges in place, all up and down
movement of the stabilizer is transmitted through the rivets
that hold the hinge onto the tubes, and there is no
significant stiffness or bracing against this movement.
Essentially you could move the root end of the stabilizer up
and down by hand and this movement would bend the
(un-supported section of) the hinge material. This would
attempt to pry the rivets out of the tube and/or bend the
thin metal back and forth.
>
> Also, because of this design the forward stabilizer
attach bolt must be a loose fit, and the stabilizer has to
be able to slide back and forth a little.
>
> The only thing that is gained by this unusual
structural load path is that 4 ounces of weight for a pair
of fittings (at the rear stabilizer spar) is saved. Can any
one explain to me why this was a good bargain?
>
> Bill Berle
> www.ezflaphandle.com - safety & performance
upgrade for light aircraft
> www.grantstar.net
- winning proposals for non-profit and
for-profit entities
>
> --------------------------------------------
> On Mon, 3/21/16, Richard Girard <aslsa.rng(at)gmail.com>
wrote:
>
> Subject: Re: Elevator/Stabilizer hinge
ass'y
> To: "kolb-list(at)matronics.com"
<kolb-list(at)matronics.com>
> Date: Monday, March 21, 2016, 2:40 PM
>
> The rear attachment
> of the horizontal stabilizer is NOT through the hinge.
It is
> through the rear folding weldments that also act as
the
> inner hinge. When it is set up correctly the hinge line
is
> on the same center as the swivel bolt in the weldment,
> however there is some allowance for misalignment. In
that
> case the weldment in the elevator spar (forward tube of
the
> elevator), can slide on the bolt in the swivel
> weldment.I've seen folding mechanisms on the Kit
> Fox and repaired the mechanism on the Highlander and in
my
> HO Homer's is the most clever. All you have to do to
> fold the HS on a Kolb is to take out a single bolt
that
> attaches the lower wires to the rudder post. I'm not
> sure how you would make it any simpler.
> Rick Girard
> On Mon, Mar 21, 2016
> at 12:55 PM, Bill Berle <victorbravo(at)sbcglobal.net>
> wrote:
>
> Bill Berle <victorbravo(at)sbcglobal.net>
>
>
>
> Are there any Kolb people on this list who are
qualified
> mechanical or aero-structure engineers? I want to ask
a
> question about the tail attachment mechanism.
>
>
>
> Before I even mention the question, I want to assure
> everyone that I AM COMPLETELY AWARE that there are X
> thousand Kolbs flying around safely with this
stabilizer
> attachment. I understand that there have not been many
(or
> perhaps any) failures of this mechanism. What I am
asking
> about is the theoretical "correctness" of the
> design, and whether any other "old-school"
> airplane people think that this system is a little
wonky.
>
>
>
> It took a few moments to finally understand how the
> mechanism works, and after looking at everything
several
> times it was clear that there is no direct structural
> attachment between the main spar tube of the stabilizer
to
> the fuselage tube (tailboom). The primary structural
load
> path between the root end of the main stabilizer spar
tube
> and the fuselage is transmitted through the elevator
> hinge... and this hinge isn't even the aircraft style
> extruded hinge.
>
>
>
> So if the air loads try to lift up or push down on the
root
> end of the stabilizer, it puts all that load through
the
> hinge, into the elevator pivot, and then finally into
the
> steel ring at the back of the fuselage.
>
>
>
> But that's not even the biggest issue in my head. The
> larger issue is that (according to plan) the flat hinge
is
> riveted to the tubes along one thin "point of
> contact" line tangent to the tube. So the root
> stabilizer load is all acting on a hinge, which itself
is
> cantilevered off of one tangent point on the
tube.
>
>
>
> Now I'm not a degreed engineer, and I'm not a
> mathematician. So I called a friend of mine who is a
retired
> aerospace structural engineer, with 50+ years of
experience.
> I showed him the plans and explained my concern, and I
was
> informed that my concerns about this system were valid.
My
> Kolb will be built with a more stable attachment.
>
>
>
> My question for any real, degreed, qualified,
> aircraft-experience engineers is... has anyone looked
at the
> stabilizer root attachment load path and had these
same
> concerns?
>
>
>
> ONCE AGAIN, this is not an attack on Mr. Kolb or his
design,
> and it is not intended to cause any panic or concern at
this
> point. What I want to know is why this load path -
through
> two tangent mounted hinge halves, into a movable
elevator,
> and then into the fuselage - is good enough, and why it
was
> not appropriate to install an attachment bracket onto
the
> fuselage at the rear stabilizer spar.
>
>
>
>
>
> Bill Berle
>
> www.ezflaphandle.com
> - safety & performance upgrade for light aircraft
>
> www.grantstar.net
> - winning proposals for
non-profit and for-profit
> entities
>
>
>
>
>
> ===========
>
> br>
> fts!)
>
> r>
>>
> w.buildersbooks.com" rel="noreferrer"
> target="_blank">www.buildersbooks.com
>
> rel="noreferrer"
> target="_blank">http://www.matronics.com/contribution
>
> -Matt
Dralle, List Admin.
>
> ===========
>
> -List" rel="noreferrer"
> target="_blank">http://www.matronics.com/Navigator?Kolb-List
>
> ===========
>
> FORUMS -
>
> eferrer"
> target="_blank">http://forums.matronics.com
>
> ===========
>
> b Site -
>
> -Matt
Dralle, List Admin.
>
> rel="noreferrer"
> target="_blank">http://www.matronics.com/contribution
>
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>
>
>
>
>
>
>
>
>
>
> --
> “Blessed
> are the cracked, for they shall let in the
light.” Groucho
> Marx
>
>
>
>
>
>
Lists This Month --
Some AWESOME FREE Gifts!)
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ceengland7(at)gmail.com
Guest
|
| Posted: Tue Mar 22, 2016 10:51 am Post subject: Elevator/Stabilizer hinge ass'y |
|
|
Any way to post a pic of the assembly, or the construction drawing, for
those of us who don't have that model to inspect? Not the entire set of
plans, of course; just the area in question.
On 3/22/2016 12:39 PM, Bill Berle wrote:
| Quote: |
I wish I could have placed a bet in Las Vegas as to how quickly some of the people would jump in and say that these airplanes have X number of hours and Y number of landings without failure. I would have been able to buy another Kolb
With all due respect to everyone, I KNOW that these airplanes are not falling out of the sky.
Now, also with all due respect, can someone with engineering knowledge tell me, ON A TECHNICAL ENGINEERING level, how it could EVER be considered as good design practice to essentially cantilever a piano hinge off of a thin wall round tube, with one line of rivets at the tangent contact point, and with flight loads often perpendicular to that axis, where that cantilever loaded hinge is not only connecting two pieces of primary aircraft structure but also attaching a primary control surface ?
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
--------------------------------------------
On Tue, 3/22/16, Dennis Rowe <rowedenny(at)windstream.net> wrote:
Subject: Re: Elevator/Stabilizer hinge ass'y
To: kolb-list(at)matronics.com
Date: Tuesday, March 22, 2016, 9:59 AM
Dennis Rowe <rowedenny(at)windstream.net>
Somebody notify John Hauck, as Miss Pfer has around 4000
hours on her airframe and has taken an eighty horse and two
100 horse Rotax 912 engines well toward their TBO! The
horizontal stabilizer must be ready to fall off at any
second.
Maybe I can get a good deal on her since her demise must be
imminent. 😉
Bill, just build the dang Firestar to plans and fly it. It
won't fall apart.
Dennis "Skid" Rowe
Mk-3 Rotax 690, with a stock Kolb empennage.😱
> On Mar 21, 2016, at 6:29 PM, Bill Berle <victorbravo(at)sbcglobal.net>
wrote:
>
>
>
> I hope I'm wrong, but my review of the plans indicated
that there is no traditional DIRECT structural connection
between the rear spar tube and the fuselage tube. All the
load paths have to take a serpentine route and go rearward
through the elevator hinges first, and only then into the
U-joint and pivot bolt in the steel ring. If you removed the
elevator hinges (from either the elevator or the
stabilizer), or if you took the pin out of the hinges, you
could move the stabilizer up and down freely while the
elevator remained bolted to the fuselage.
>
> Even WITH all the hinges in place, all up and down
movement of the stabilizer is transmitted through the rivets
that hold the hinge onto the tubes, and there is no
significant stiffness or bracing against this movement.
Essentially you could move the root end of the stabilizer up
and down by hand and this movement would bend the
(un-supported section of) the hinge material. This would
attempt to pry the rivets out of the tube and/or bend the
thin metal back and forth.
>
> Also, because of this design the forward stabilizer
attach bolt must be a loose fit, and the stabilizer has to
be able to slide back and forth a little.
>
> The only thing that is gained by this unusual
structural load path is that 4 ounces of weight for a pair
of fittings (at the rear stabilizer spar) is saved. Can any
one explain to me why this was a good bargain?
>
> Bill Berle
> www.ezflaphandle.com - safety & performance
upgrade for light aircraft
> www.grantstar.net
- winning proposals for non-profit and
for-profit entities
>
> --------------------------------------------
> On Mon, 3/21/16, Richard Girard <aslsa.rng(at)gmail.com>
wrote:
>
> Subject: Re: Elevator/Stabilizer hinge
ass'y
> To: "kolb-list(at)matronics.com"
<kolb-list(at)matronics.com>
> Date: Monday, March 21, 2016, 2:40 PM
>
> The rear attachment
> of the horizontal stabilizer is NOT through the hinge.
It is
> through the rear folding weldments that also act as
the
> inner hinge. When it is set up correctly the hinge line
is
> on the same center as the swivel bolt in the weldment,
> however there is some allowance for misalignment. In
that
> case the weldment in the elevator spar (forward tube of
the
> elevator), can slide on the bolt in the swivel
> weldment.I've seen folding mechanisms on the Kit
> Fox and repaired the mechanism on the Highlander and in
my
> HO Homer's is the most clever. All you have to do to
> fold the HS on a Kolb is to take out a single bolt
that
> attaches the lower wires to the rudder post. I'm not
> sure how you would make it any simpler.
> Rick Girard
> On Mon, Mar 21, 2016
> at 12:55 PM, Bill Berle <victorbravo(at)sbcglobal.net>
> wrote:
>
> Bill Berle <victorbravo(at)sbcglobal.net>
>
>
>
> Are there any Kolb people on this list who are
qualified
> mechanical or aero-structure engineers? I want to ask
a
> question about the tail attachment mechanism.
>
>
>
> Before I even mention the question, I want to assure
> everyone that I AM COMPLETELY AWARE that there are X
> thousand Kolbs flying around safely with this
stabilizer
> attachment. I understand that there have not been many
(or
> perhaps any) failures of this mechanism. What I am
asking
> about is the theoretical "correctness" of the
> design, and whether any other "old-school"
> airplane people think that this system is a little
wonky.
>
>
>
> It took a few moments to finally understand how the
> mechanism works, and after looking at everything
several
> times it was clear that there is no direct structural
> attachment between the main spar tube of the stabilizer
to
> the fuselage tube (tailboom). The primary structural
load
> path between the root end of the main stabilizer spar
tube
> and the fuselage is transmitted through the elevator
> hinge... and this hinge isn't even the aircraft style
> extruded hinge.
>
>
>
> So if the air loads try to lift up or push down on the
root
> end of the stabilizer, it puts all that load through
the
> hinge, into the elevator pivot, and then finally into
the
> steel ring at the back of the fuselage.
>
>
>
> But that's not even the biggest issue in my head. The
> larger issue is that (according to plan) the flat hinge
is
> riveted to the tubes along one thin "point of
> contact" line tangent to the tube. So the root
> stabilizer load is all acting on a hinge, which itself
is
> cantilevered off of one tangent point on the
tube.
>
>
>
> Now I'm not a degreed engineer, and I'm not a
> mathematician. So I called a friend of mine who is a
retired
> aerospace structural engineer, with 50+ years of
experience.
> I showed him the plans and explained my concern, and I
was
> informed that my concerns about this system were valid.
My
> Kolb will be built with a more stable attachment.
>
>
>
> My question for any real, degreed, qualified,
> aircraft-experience engineers is... has anyone looked
at the
> stabilizer root attachment load path and had these
same
> concerns?
>
>
>
> ONCE AGAIN, this is not an attack on Mr. Kolb or his
design,
> and it is not intended to cause any panic or concern at
this
> point. What I want to know is why this load path -
through
> two tangent mounted hinge halves, into a movable
elevator,
> and then into the fuselage - is good enough, and why it
was
> not appropriate to install an attachment bracket onto
the
> fuselage at the rear stabilizer spar.
>
>
>
>
>
> Bill Berle
>
|
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stuart(at)harnerfarm.net
Guest
|
| Posted: Tue Mar 22, 2016 11:31 am Post subject: Elevator/Stabilizer hinge ass'y |
|
|
Bill,
I am not an engineer but I did stay in a Holiday Inn last night. No, not really, but I do have a fundamental understanding of load transmission through a structure.
First a question, and please don't be offended. Have you had an opportunity to observe the structure of the Kolb tail while it was being folded and then again when it is bolted into place? I asked this because I found a couple of things in the plans of the Firefly that I did not understand until I was able to actually see it live. Simply put, I had trouble visualizing it from just the plans.
One thing that I think is missing from this discussion is the loads carried by the brace wires. I would posit that most of the forces from the tail that are transmitted to the boom tube are carried by the braces. These, when properly tensioned are actually pre-loaded slightly. This puts the tubes in compression which makes the whole thing quite strong. It also transfers the loads from the horizontals to the steel post of the verticals which in turn is transferred to the boom tube via the steel ring which is bolted and/or riveted to the tube.
Of course some loads are transferred through the hinge points and the front hinge must be able to slide slightly as the elevator moves through its arc of travel. Could this be made stronger? Of course, but not without sacrificing something else such as weight or foldability. It is actually a very clever design and I suspect that the majority of loads that move through the rear hinge come from the elevator and not the stabilizer.
I would also bet that the loads carried through the hinges is far below the shear and tension limits of properly installed rivets.
I am actually more "freaked out" by the fact that everything in the tail depends on that one little 3/16" bolt (Firefly) that holds the lower braces in place. Really, the threads on that bolt are all there is between you and falling out of the sky. To combat this irrationality I swap out the bolt fairly often and the nuts even more often. If it really bothered me, I would stay on the ground.
Perhaps you could send a copy of your plans to Barnaby Wainfan and ask for his analysis. I hear he is a really nice guy. From reading his articles over the years I am sure he could provide the answers you seek.
As Uncle Red used to say: "Remember, if women don't find you handsome, they should at least find you handy"
Stuart
--
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rmurrill(at)cox.net
Guest
|
| Posted: Tue Mar 22, 2016 11:33 am Post subject: Elevator/Stabilizer hinge ass'y |
|
|
I suffer from the same 50 year malady you mentioned earlier, but would
suggest you propose to your aero/ structures engineer
friend a couple of alternate details. I would agree that the structural
configuration is non standard, with the appearance of some odd geometric
coupling, but it has clearly worked well for many years and tens of
thousands of hours fleet time regardless of the Las Vegas odd makers.
The main point is the loads are very small compared to the strength of the
hardware...arguably by more than an order of magnitude.
Flying downloads on the horizontal tail are probably in the
50 lb maybe 100 lb at the most to provide flyable static pitch and speed
stability. Low aspect ratio and taper puts the center of pressure fairly
close to the wire bracing attachments, probably forward and inboard, so most
of these downloads are taken out as tension in those wires and compression
in the vertical stabilizer tube. Smaller loads are reacted at the root
bolts and across the hinges. One would not attempt to design the structure
for full elevator deflection at
Vne, so reasonably one would only ever see relatively modest changes in the
aero down loads throughout the flight spectrum. A fairly extreme case that
would develop very high pitch rates and require elevator correction would be
full power to idle or the reverse. That would produce about 300 lb of force
at maybe 2 ft
above the cg and would require a change in tail download of about
40 lb assuming the moment arm is about 15 ft. So that’s 20 lb per side.
Each of the hinge rivets assuming they are 1/8th inch is good for 120 lbs
single shear. The load is shared by lots of rivets. The bolts are I
believe 5/16 which are good for 5,500 lb single shear even if only grade 5.
I would argue that the hinges, dozens of rivets and large diameter pivoting
bolts appear
to be overdesigned for the basic small aero loads of this aircraft. Fatigue
loads from the prop wash swirl could be an issue,
but apparently not from fleet experience.
Ultimate static strength is most likely dictated by the aluminum tubing
substructure, not by the rivets, hinges, or support bolts....
I recommend not trying to improve the design!
Bob
--
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Jim Baker
Joined: 30 Mar 2006
Posts: 181
Location: Sayre, PA
|
| Posted: Tue Mar 22, 2016 12:09 pm Post subject: Elevator/Stabilizer hinge ass'y |
|
|
Now the onus is on you. Post one single incident of horizontal stab/elevator failure. Just one.
On the other hand, they are experimental and you, the builder, are the experimenter. Press on. Could care less.
Jim Baker
405 426 5377
--
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lcottrell
Joined: 29 May 2006
Posts: 1494
Location: Jordan Valley, Or
|
| Posted: Tue Mar 22, 2016 12:13 pm Post subject: Elevator/Stabilizer hinge ass'y |
|
|
Berle wrote:"I wish I could have placed a bet in Las Vegas as to how quickly some of thepeople would jump in and say that these airplanes have X number of hours andY number of landings without failure. I would have been able to buy anotherKolb "
Not to put too fine a point on the discussion, but the reason that you heard the phrase that you knew would be coming, is that we too have seen this all before as well. I have at least one friend that always had to improve every thing that he bought, simply because that was his disease. That's ok, what ever spins your prop. If reinventing the wheel is your thing, give er hell.
I have had VG's for years, as have quite a few of the guys. I have had 4130 longer gear legs for at least a couple of years, so have quite a few of the guy's. Yep, it helps the plane perform better. I have also crashed at least three times and the worst that I got besides humility was a sprained left middle finger. So I personally am a fan of the way that Homer designed the plane. It fits my mission perfectly.
If the one that you bought does not fit the mission as you see it, by all means tweak it any way that makes you happy.
I have also seen several guys on the list that were convinced that a bit of this and a bit of that would make the plane perform just fine with one of the other types of engines. I don't think any of them are still flying them because it turned a perfectly fine plane into something that flew like a C150, and was about as much fun to fly as watching grass grow. Again, you are a big boy, and apparently you have a better idea, by all mean have at it. I know one guy that just had to have a 1/2 VW on his plane. We on the list went through about 2 years of trying and eventually he gave up, sold the plane and never flew again.
So you see, we too have seen some of this before. Now I personally don't want to hurt your feelings, but the little smiley face in your message didn't quite take all the sting out of your last post. We will see if I can do a bit better, or at least as good. No body here cares if you can improve your plane. It is your and yours alone, tweak it any way you like. If it is a real improvement we might want to do the same, just try to not tell me how stupid I am because mine does just exactly what I want and need.
Larry
On Tue, Mar 22, 2016 at 1:33 PM, Bob <rmurrill(at)cox.net (rmurrill(at)cox.net)> wrote:
[quote]--> Kolb-List message posted by: "Bob" <rmurrill(at)cox.net (rmurrill(at)cox.net)>
I suffer from the same 50 year malady you mentioned earlier, but would
suggest you propose to your aero/ structures engineer
friend a couple of alternate details. I would agree that the structural
configuration is non standard, with the appearance of some odd geometric
coupling, but it has clearly worked well for many years and tens of
thousands of hours fleet time regardless of the Las Vegas odd makers.
The main point is the loads are very small compared to the strength of the
hardware...arguably by more than an order of magnitude.
Flying downloads on the horizontal tail are probably in the
50 lb maybe 100 lb at the most to provide flyable static pitch and speed
stability. Low aspect ratio and taper puts the center of pressure fairly
close to the wire bracing attachments, probably forward and inboard, so most
of these downloads are taken out as tension in those wires and compression
in the vertical stabilizer tube. Smaller loads are reacted at the root
bolts and across the hinges. One would not attempt to design the structure
for full elevator deflection at
Vne, so reasonably one would only ever see relatively modest changes in the
aero down loads throughout the flight spectrum. A fairly extreme case that
would develop very high pitch rates and require elevator correction would be
full power to idle or the reverse. That would produce about 300 lb of force
at maybe 2 ft
above the cg and would require a change in tail download of about
40 lb assuming the moment arm is about 15 ft. So that’s 20 lb per side.
Each of the hinge rivets assuming they are 1/8th inch is good for 120 lbs
single shear. The load is shared by lots of rivets. The bolts are I
believe 5/16 which are good for 5,500 lb single shear even if only grade 5.
I would argue that the hinges, dozens of rivets and large diameter pivoting
bolts appear
to be overdesigned for the basic small aero loads of this aircraft. Fatigue
loads from the prop wash swirl could be an issue,
but apparently not from fleet experience.
Ultimate static strength is most likely dictated by the aluminum tubing
substructure, not by the rivets, hinges, or support bolts....
I recommend not trying to improve the design!
Bob
--
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neilsenrm(at)gmail.com
Guest
|
| Posted: Tue Mar 22, 2016 12:19 pm Post subject: Elevator/Stabilizer hinge ass'y |
|
|
Bill
It might be helpful to look at a completed airplane. You may not be visualizing correctly the drawings you are looking at. The design works and it can be folded.
Years ago we had a guy that felt he had to fix everything on the Kolb MKIII that he was building. He made a valiant effort in completing the plane. He must have spent 3-4 thousand extra hours working on all the changes. Luckily he never completed the airplane. He was a great guy and is still alive because he didn't ever fly that plane.
My advice is build the plane exactly by the plans. There are a few really good changes that a few people have tried to tell you about but???
If you absolutely must make all the changes you are talking about get real good insurance for your love ones and DO NOT call it a Kolb. Don't even mention it started as a Kolb kit. Also please quit talking about all the issues you think are wrong, somebody might think you know what you are talking about and hurt themselves too. Sorry the proof is in the massive hours in the fleet.
Did anyone ever tell you about one of the Kolb employees that took a plane up and intentionally tried to tear the plane apart. He finally with considerable effort ripped the wings off, he threw out a chute and later fixed the point of failure. Our planes are well designed and tested.
Even with all that evidence I will still say my advice is worth what you paid for it.
Rick Neilsen
Redrive VW Powered
On Tue, Mar 22, 2016 at 1:39 PM, Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)> wrote:
| Quote: | --> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>
I wish I could have placed a bet in Las Vegas as to how quickly some of the people would jump in and say that these airplanes have X number of hours and Y number of landings without failure. I would have been able to buy another Kolb
With all due respect to everyone, I KNOW that these airplanes are not falling out of the sky.
Now, also with all due respect, can someone with engineering knowledge tell me, ON A TECHNICAL ENGINEERING level, how it could EVER be considered as good design practice to essentially cantilever a piano hinge off of a thin wall round tube, with one line of rivets at the tangent contact point, and with flight loads often perpendicular to that axis, where that cantilever loaded hinge is not only connecting two pieces of primary aircraft structure but also attaching a primary control surface ?
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
--------------------------------------------
On Tue, 3/22/16, Dennis Rowe <rowedenny(at)windstream.net (rowedenny(at)windstream.net)> wrote:
Subject: Re: Elevator/Stabilizer hinge ass'y
To: kolb-list(at)matronics.com (kolb-list(at)matronics.com)
Date: Tuesday, March 22, 2016, 9:59 AM
--> Kolb-List message posted by:
Dennis Rowe <rowedenny(at)windstream.net (rowedenny(at)windstream.net)>
Somebody notify John Hauck, as Miss Pfer has around 4000
hours on her airframe and has taken an eighty horse and two
100 horse Rotax 912 engines well toward their TBO! The
horizontal stabilizer must be ready to fall off at any
second.
Maybe I can get a good deal on her since her demise must be
imminent. 😉
Bill, just build the dang Firestar to plans and fly it. It
won't fall apart.
Dennis "Skid" Rowe
Mk-3 Rotax 690, with a stock Kolb empennage.😱
> On Mar 21, 2016, at 6:29 PM, Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>
wrote:
>
> --> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>
>
> I hope I'm wrong, but my review of the plans indicated
that there is no traditional DIRECT structural connection
between the rear spar tube and the fuselage tube. All the
load paths have to take a serpentine route and go rearward
through the elevator hinges first, and only then into the
U-joint and pivot bolt in the steel ring. If you removed the
elevator hinges (from either the elevator or the
stabilizer), or if you took the pin out of the hinges, you
could move the stabilizer up and down freely while the
elevator remained bolted to the fuselage.
>
> Even WITH all the hinges in place, all up and down
movement of the stabilizer is transmitted through the rivets
that hold the hinge onto the tubes, and there is no
significant stiffness or bracing against this movement.
Essentially you could move the root end of the stabilizer up
and down by hand and this movement would bend the
(un-supported section of) the hinge material. This would
attempt to pry the rivets out of the tube and/or bend the
thin metal back and forth.
>
> Also, because of this design the forward stabilizer
attach bolt must be a loose fit, and the stabilizer has to
be able to slide back and forth a little.
>
> The only thing that is gained by this unusual
structural load path is that 4 ounces of weight for a pair
of fittings (at the rear stabilizer spar) is saved. Can any
one explain to me why this was a good bargain?
>
> Bill Berle
> www.ezflaphandle.com - safety & performance
upgrade for light aircraft
> www.grantstar.net
- winning proposals for non-profit and
for-profit entities
>
> --------------------------------------------
> On Mon, 3/21/16, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)>
wrote:
>
> Subject: Re: Elevator/Stabilizer hinge
ass'y
> To: "kolb-list(at)matronics.com (kolb-list(at)matronics.com)"
<kolb-list(at)matronics.com (kolb-list(at)matronics.com)>
> Date: Monday, March 21, 2016, 2:40 PM
>
> The rear attachment
> of the horizontal stabilizer is NOT through the hinge.
It is
> through the rear folding weldments that also act as
the
> inner hinge. When it is set up correctly the hinge line
is
> on the same center as the swivel bolt in the weldment,
> however there is some allowance for misalignment. In
that
> case the weldment in the elevator spar (forward tube of
the
> elevator), can slide on the bolt in the swivel
> weldment.I've seen folding mechanisms on the Kit
> Fox and repaired the mechanism on the Highlander and in
my
> HO Homer's is the most clever. All you have to do to
> fold the HS on a Kolb is to take out a single bolt
that
> attaches the lower wires to the rudder post. I'm not
> sure how you would make it any simpler.
> Rick Girard
> On Mon, Mar 21, 2016
> at 12:55 PM, Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>
> wrote:
> --> Kolb-List message posted by:
> Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>
>
>
>
> Are there any Kolb people on this list who are
qualified
> mechanical or aero-structure engineers? I want to ask
a
> question about the tail attachment mechanism.
>
>
>
> Before I even mention the question, I want to assure
> everyone that I AM COMPLETELY AWARE that there are X
> thousand Kolbs flying around safely with this
stabilizer
> attachment. I understand that there have not been many
(or
> perhaps any) failures of this mechanism. What I am
asking
> about is the theoretical "correctness" of the
> design, and whether any other "old-school"
> airplane people think that this system is a little
wonky.
>
>
>
> It took a few moments to finally understand how the
> mechanism works, and after looking at everything
several
> times it was clear that there is no direct structural
> attachment between the main spar tube of the stabilizer
to
> the fuselage tube (tailboom). The primary structural
load
> path between the root end of the main stabilizer spar
tube
> and the fuselage is transmitted through the elevator
> hinge... and this hinge isn't even the aircraft style
> extruded hinge.
>
>
>
> So if the air loads try to lift up or push down on the
root
> end of the stabilizer, it puts all that load through
the
> hinge, into the elevator pivot, and then finally into
the
> steel ring at the back of the fuselage.
>
>
>
> But that's not even the biggest issue in my head. The
> larger issue is that (according to plan) the flat hinge
is
> riveted to the tubes along one thin "point of
> contact" line tangent to the tube. So the root
> stabilizer load is all acting on a hinge, which itself
is
> cantilevered off of one tangent point on the
tube.
>
>
>
> Now I'm not a degreed engineer, and I'm not a
> mathematician. So I called a friend of mine who is a
retired
> aerospace structural engineer, with 50+ years of
experience.
> I showed him the plans and explained my concern, and I
was
> informed that my concerns about this system were valid.
My
> Kolb will be built with a more stable attachment.
>
>
>
> My question for any real, degreed, qualified,
> aircraft-experience engineers is... has anyone looked
at the
> stabilizer root attachment load path and had these
same
> concerns?
>
>
>
> ONCE AGAIN, this is not an attack on Mr. Kolb or his
design,
> and it is not intended to cause any panic or concern at
this
> point. What I want to know is why this load path -
through
> two tangent mounted hinge halves, into a movable
elevator,
> and then into the fuselage - is good enough, and why it
was
> not appropriate to install an attachment bracket onto
the
> fuselage at the rear stabilizer spar.
>
>
>
>
>
> Bill Berle
>
> www.ezflaphandle.com
> - safety & performance upgrade for light aircraft
>
> www.grantstar.net
> - winning proposals for
non-profit and for-profit
> entities
>
>
>
>
>
> ===========
>
> br>
> fts!)
>
> r>
>>
> w.buildersbooks.com" rel="noreferrer"
> target="_blank">www.buildersbooks.com
>
> rel="noreferrer"
> target="_blank">http://www.matronics.com/contribution
>
> -Matt
Dralle, List Admin.
>
> ===========
>
> -List" rel="noreferrer"
> target="_blank">http://www.matronics.com/Navigator?Kolb-List
>
> ===========
>
> FORUMS -
>
> eferrer"
> target="_blank">http://forums.matronics.com
>
> ===========
>
> b Site -
>
> -Matt
Dralle, List Admin.
>
> rel="noreferrer"
> target="_blank">http://www.matronics.com/contribution
>
> ===========
>
>
>
>
>
>
>
>
>
>
> --
> “Blessed
> are the cracked, for they shall let in the
light.” Groucho
> Marx
>
>
>
>
>
>
Lists This Month --
Some AWESOME FREE Gifts!)
Raiser. Click on
more about
Gifts provided
www.buildersbooks.com
-Matt
Dralle, List Admin.
Forum -
- MATRONICS WEB FORUMS -
List Contribution Web Site -
-Matt
Dralle, List Admin.
===========
br> fts!)
r> > w.buildersbooks.com" rel="noreferrer" target="_blank">www.buildersbooks.com
rel="noreferrer" target="_blank">http://www.matronics.com/contribution
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===========
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eferrer" target="_blank">http://forums.matronics.com
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victorbravo(at)sbcglobal.
Guest
|
| Posted: Tue Mar 22, 2016 12:40 pm Post subject: Elevator/Stabilizer hinge ass'y |
|
|
Thank you all for the replies. I appreciate the opportunity to discuss this, without people thinking that I am trashing the aircraft, or insulting Mr. Kolb's legacy.
Yes I had considered that some part of the tail loads are carried by the brace wires, this is why I referred to the questionable part as the stabilizer "root loads" instead of the whole stabilizer. Of course, just like a strut braced wing there is a large "inward" (compression) load on the tube, but since the elevator is tapered there is still a large portion of the force generated that is vertical at the root end.
Those rivets holding the hinge may well be capable of 120 pounds in shear, or perhaps even in tension. I have no quarrel whatsoever with the strength of the rivets on such a light and slow aircraft. And yes there are a lot of them.
But the angular ORIENTATION of the hinges, and the fact that the hinges are somewhat "cantilevered" as I have called it, puts a "peel" load on those fasteners, like a crow bar trying to peel and pop the heads off the rivets at an angle. That is probably the worst case for those rivets. The failure mode would be that the loads are rocking the rivets slowly back and forth, loosening them.
Also, the hinges themselves are not designed for the loads to be hanging out 3/8 or 1/2 inch from their attachment, like a diving board.
One person replied that I may not be understanding the mechanism, and how it folds, and that the front attachment moves a little. I have taken a little time to study the plans and try to understand this. I believe that I understand it (whether I agree with the design or not). If the rear stabilizer attachment is in fact located on exactly the same axis as the elevator hinge, then the front of the stabilizer should not need to move fore and aft at all with elevator deflection. Elevator deflection could create fore-aft (or up-down) movement ONLY if there IS some amount of offset between the hinge axis and the rear stabilizer mounting. If the two axes are concentric, there could not be any linear motion by definition.
I believe that the only reason the front stabilizer attachment has to be able to slide a little is because in reality for the average builder it is very difficult to locate the hinges at precisely the center of the welded elevator horn/ pivot mechanism. Without any jig or fixture to guarantee the exact location of the hinge pin in open space, it is etoo asy for the hinge pin to be a little bit fore-aft or up-down... while the holes are drilled and the rivets are installed.
So I am guessing that to make it easier for the builder, and to prevent binding and cracking of the parts, the front attachment was left a little loose and the rear attachment was eliminated.
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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|
|
victorbravo(at)sbcglobal.
Guest
|
| Posted: Tue Mar 22, 2016 1:14 pm Post subject: Elevator/Stabilizer hinge ass'y |
|
|
Wow. Please forgive me if anyone thought that I was being too aggressive or questioning. Holy Mackerel, I was discussing innovation, experimentation, and individuality in light aircraft construction.
Apparently there is no room for improvement in the design, and there were no compromises made in manufacturing the kits. Thankfully, none of this reliance on status quo was in force back when Mr. Kolb was experimenting with a new way to build and improve on his personal aircraft designs.
My sincerest apology for the unintended effect of there being a "Sting" in any of my comments. Absolutely unintentional.
| Quote: | From this point I will try to constrain my questions and comments within direct relevance to the existing design, or what has been done (or modified) already.
|
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
--------------------------------------------
On Tue, 3/22/16, Rick Neilsen <neilsenrm(at)gmail.com> wrote:
Subject: Re: Elevator/Stabilizer hinge ass'y
To: "kolb-list(at)matronics.com" <kolb-list(at)matronics.com>
Date: Tuesday, March 22, 2016, 1:19 PM
Bill
It might be helpful to look at a
completed airplane. You may not be visualizing correctly the
drawings you are looking at. The design works and it can be
folded.
Years ago we had a guy that felt he
had to fix everything on the Kolb MKIII that he was
building. He made a valiant effort in completing the plane.
He must have spent 3-4 thousand extra hours working on all
the changes. Luckily he never completed the airplane. He was
a great guy and is still alive because he didn't ever
fly that plane.
My advice is build the plane
exactly by the plans. There are a few really good changes
that a few people have tried to tell you about
but???
If you absolutely must make all the
changes you are talking about get real good insurance for
your love ones and DO NOT call it a Kolb. Don't even
mention it started as a Kolb kit. Also please quit talking
about all the issues you think are wrong, somebody might
think you know what you are talking about and hurt
themselves too. Sorry the proof is in the massive hours in
the fleet.
Did anyone ever tell you about one
of the Kolb employees that took a plane up and intentionally
tried to tear the plane apart. He finally with considerable
effort ripped the wings off, he threw out a chute and later
fixed the point of failure. Our planes are well designed and
tested.
Even with all that evidence I will
still say my advice is worth what you paid for it.
Rick NeilsenRedrive VW Powered
On Tue, Mar 22, 2016
at 1:39 PM, Bill Berle <victorbravo(at)sbcglobal.net>
wrote:
Bill Berle <victorbravo(at)sbcglobal.net>
I wish I could have placed a bet in Las Vegas as to
how quickly some of the people would jump in and say that
these airplanes have X number of hours and Y number of
landings without failure. I would have been able to buy
another Kolb
With all due respect to everyone, I KNOW that these
airplanes are not falling out of the sky.
Now, also with all due respect, can someone with engineering
knowledge tell me, ON A TECHNICAL ENGINEERING level, how it
could EVER be considered as good design practice to
essentially cantilever a piano hinge off of a thin wall
round tube, with one line of rivets at the tangent contact
point, and with flight loads often perpendicular to that
axis, where that cantilever loaded hinge is not only
connecting two pieces of primary aircraft structure but also
attaching a primary control surface ?
Bill Berle
www.ezflaphandle.com
- safety & performance upgrade for light aircraft
www.grantstar.net
- winning proposals for non-profit and for-profit
entities
--------------------------------------------
On Tue, 3/22/16, Dennis
Rowe <rowedenny(at)windstream.net>
wrote:
Subject: Re: Elevator/Stabilizer hinge
ass'y
To: kolb-list(at)matronics.com
Date: Tuesday, March 22, 2016, 9:59 AM
Dennis Rowe <rowedenny(at)windstream.net>
Somebody notify John Hauck, as Miss Pfer has around 4000
hours on her airframe and has taken an eighty horse and
two
100 horse Rotax 912 engines well toward their TBO! The
horizontal stabilizer must be ready to fall off at any
second.
Maybe I can get a good deal on her since her demise must
be
imminent. 😉
Bill, just build the dang Firestar to plans and fly it.
It
won't fall apart.
Dennis "Skid" Rowe
Mk-3 Rotax 690, with a stock Kolb empennage.😱
> On Mar 21, 2016, at 6:29 PM, Bill Berle <victorbravo(at)sbcglobal.net>
wrote:
>
>
>
> I hope I'm wrong, but my review of the plans
indicated
that there is no traditional DIRECT structural connection
between the rear spar tube and the fuselage tube. All the
load paths have to take a serpentine route and go
rearward
through the elevator hinges first, and only then into the
U-joint and pivot bolt in the steel ring. If you removed
the
elevator hinges (from either the elevator or the
stabilizer), or if you took the pin out of the hinges,
you
could move the stabilizer up and down freely while the
elevator remained bolted to the fuselage.
>
> Even WITH all the hinges in place, all up and down
movement of the stabilizer is transmitted through the
rivets
that hold the hinge onto the tubes, and there is no
significant stiffness or bracing against this movement.
Essentially you could move the root end of the stabilizer
up
and down by hand and this movement would bend the
(un-supported section of) the hinge material. This would
attempt to pry the rivets out of the tube and/or bend the
thin metal back and forth.
>
> Also, because of this design the forward stabilizer
attach bolt must be a loose fit, and the stabilizer has
to
be able to slide back and forth a little.
>
> The only thing that is gained by this unusual
structural load path is that 4 ounces of weight for a
pair
of fittings (at the rear stabilizer spar) is saved. Can
any
one explain to me why this was a good bargain?
>
> Bill Berle
> www.ezflaphandle.com
- safety & performance
upgrade for light aircraft
> www.grantstar.net
- winning proposals for non-profit and
for-profit entities
>
> --------------------------------------------
> On Mon, 3/21/16, Richard Girard <aslsa.rng(at)gmail.com>
wrote:
>
> Subject: Re: Elevator/Stabilizer hinge
ass'y
> To: "kolb-list(at)matronics.com"
<kolb-list(at)matronics.com>
> Date: Monday, March 21, 2016, 2:40 PM
>
> The rear attachment
> of the horizontal stabilizer is NOT through the
hinge.
It is
> through the rear folding weldments that also act as
the
> inner hinge. When it is set up correctly the hinge
line
is
> on the same center as the swivel bolt in the
weldment,
> however there is some allowance for misalignment. In
that
> case the weldment in the elevator spar (forward tube
of
the
> elevator), can slide on the bolt in the swivel
> weldment.I've seen folding mechanisms on the Kit
> Fox and repaired the mechanism on the Highlander and
in
my
> HO Homer's is the most clever. All you have to do
to
> fold the HS on a Kolb is to take out a single bolt
that
> attaches the lower wires to the rudder post. I'm
not
> sure how you would make it any simpler.
> Rick Girard
> On Mon, Mar 21, 2016
> at 12:55 PM, Bill Berle <victorbravo(at)sbcglobal.net>
> wrote:
>
> Bill Berle <victorbravo(at)sbcglobal.net>
>
>
>
> Are there any Kolb people on this list who are
qualified
> mechanical or aero-structure engineers? I want to
ask
a
> question about the tail attachment mechanism.
>
>
>
> Before I even mention the question, I want to assure
> everyone that I AM COMPLETELY AWARE that there are X
> thousand Kolbs flying around safely with this
stabilizer
> attachment. I understand that there have not been
many
(or
> perhaps any) failures of this mechanism. What I am
asking
> about is the theoretical "correctness" of
the
> design, and whether any other "old-school"
> airplane people think that this system is a little
wonky.
>
>
>
> It took a few moments to finally understand how the
> mechanism works, and after looking at everything
several
> times it was clear that there is no direct
structural
> attachment between the main spar tube of the
stabilizer
to
> the fuselage tube (tailboom). The primary structural
load
> path between the root end of the main stabilizer
spar
tube
> and the fuselage is transmitted through the elevator
> hinge... and this hinge isn't even the aircraft
style
> extruded hinge.
>
>
>
> So if the air loads try to lift up or push down on
the
root
> end of the stabilizer, it puts all that load through
the
> hinge, into the elevator pivot, and then finally
into
the
> steel ring at the back of the fuselage.
>
>
>
> But that's not even the biggest issue in my head.
The
> larger issue is that (according to plan) the flat
hinge
is
> riveted to the tubes along one thin "point of
> contact" line tangent to the tube. So the root
> stabilizer load is all acting on a hinge, which
itself
is
> cantilevered off of one tangent point on the
tube.
>
>
>
> Now I'm not a degreed engineer, and I'm not
a
> mathematician. So I called a friend of mine who is a
retired
> aerospace structural engineer, with 50+ years of
experience.
> I showed him the plans and explained my concern, and
I
was
> informed that my concerns about this system were
valid.
My
> Kolb will be built with a more stable attachment.
>
>
>
> My question for any real, degreed, qualified,
> aircraft-experience engineers is... has anyone
looked
at the
> stabilizer root attachment load path and had these
same
> concerns?
>
>
>
> ONCE AGAIN, this is not an attack on Mr. Kolb or his
design,
> and it is not intended to cause any panic or concern
at
this
> point. What I want to know is why this load path -
through
> two tangent mounted hinge halves, into a movable
elevator,
> and then into the fuselage - is good enough, and why
it
was
> not appropriate to install an attachment bracket
onto
the
> fuselage at the rear stabilizer spar.
>
>
>
>
>
> Bill Berle
>
> www.ezflaphandle.com
> - safety & performance upgrade for light
aircraft
>
> www.grantstar.net
> - winning proposals for
non-profit and for-profit
> entities
>
>
>
>
>
> ===========
>
> br>
> fts!)
>
> r>
>>
> w.buildersbooks.com"
rel="noreferrer"
> target="_blank">www.buildersbooks.com
>
> rel="noreferrer"
> target="_blank">http://www.matronics.com/contribution
>
> -Matt
Dralle, List Admin.
>
> ===========
>
> -List" rel="noreferrer"
> target="_blank">http://www.matronics.com/Navigator?Kolb-List
>
> ===========
>
> FORUMS -
>
> eferrer"
> target="_blank">http://forums.matronics.com
>
> ===========
>
> b Site -
>
> -Matt
Dralle, List Admin.
>
> rel="noreferrer"
> target="_blank">http://www.matronics.com/contribution
>
> ===========
>
>
>
>
>
>
>
>
>
>
> --
> “Blessed
> are the cracked, for they shall let in the
light.” Groucho
> Marx
>
>
>
>
>
>
Lists This Month --
Some AWESOME FREE Gifts!)
Raiser. Click on
more about
Gifts provided
www.buildersbooks.com
-Matt
Dralle, List Admin.
Forum -
- MATRONICS WEB FORUMS
-
List Contribution Web
Site -
-Matt
Dralle, List Admin.
===========
br>
fts!)
r>
>
w.buildersbooks.com" rel="noreferrer"
target="_blank">www.buildersbooks.com
rel="noreferrer"
target="_blank">http://www.matronics.com/contribution
-Matt Dralle, List Admin.
===========
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target="_blank">http://www.matronics.com/Navigator?Kolb-List
===========
FORUMS -
eferrer"
target="_blank">http://forums.matronics.com
===========
b Site -
-Matt Dralle, List Admin.
rel="noreferrer"
target="_blank">http://www.matronics.com/contribution
===========
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|
|
|
| Back to top |
|
|
undoctor(at)rcn.com
Guest
|
| Posted: Tue Mar 22, 2016 2:09 pm Post subject: Elevator/Stabilizer hinge ass'y |
|
|
Bill,
If you search through the archives or Google Kolb Aircraft history, you may find a photo of Homer sitting on his Kolb Flyer dated 1956. That's about 60 years ago and 30 years before ultralights existed as a classification of aircraft. It was powered by 4 chain saw engines.
Prior to that photo, Homer, the farm boy who wanted to fly, experimented with aircraft he built that was pulled by a boat on the Schuylkill River. One day a young lad was sitting on the bank of the river and witnessed a wing fold and Homer took a bath.
There were two results of that incident: first, Homer stopped using hardware store eye bolts, and second, the young lad got an education in aeronautical engineering and later went to work for Homer. He is the man who was testing G's, folded a wing and threw out the hand held 'chute in order to live.
Also, as has been mentioned, Kolbs have been proven over many years and tens of thousands of hours. I believe the problem lies in that, whether or not you realize it, you come across as having the opinion that before you came on the scene there was never anyone who could think things through as thoroughly and analytically as you.
Trust me when I tell you that that's a huge error.
Enjoy your building time, Bill. As you should have already noticed there's a lot of experience and helpful people on the list. Be careful not to abuse their kindness.
Dave Kulp
Bethlehem, PA
ex: Chicken Hawk
ex: Ultrastar
ex: FireFly
Sent from my Verizon Wireless 4G LTE smartphone
-------- Original message --------
From: Bill Berle
Date:03/22/2016 5:10 PM (GMT-05:00)
To: kolb-list(at)matronics.com
Subject: Re: Kolb-List: Elevator/Stabilizer hinge ass'y
--> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net>
Wow. Please forgive me if anyone thought that I was being too aggressive or questioning. Holy Mackerel, I was discussing innovation, experimentation, and individuality in light aircraft construction.
Apparently there is no room for improvement in the design, and there were no compromises made in manufacturing the kits. Thankfully, none of this reliance on status quo was in force back when Mr. Kolb was experimenting with a new way to build and improve on his personal aircraft designs.
My sincerest apology for the unintended effect of there being a "Sting" in any of my comments. Absolutely unintentional.
| Quote: | From this point I will try to constrain my questions and comments within direct relevance to the existing design, or what has been done (or modified) already.
|
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
--------------------------------------------
On Tue, 3/22/16, Rick Neilsen <neilsenrm(at)gmail.com> wrote:
Subject: Re: Kolb-List: Elevator/Stabilizer hinge ass'y
To: "kolb-list(at)matronics.com" <kolb-list(at)matronics.com>
Date: Tuesday, March 22, 2016, 1:19 PM
Bill
It might be helpful to look at a
completed airplane. You may not be visualizing correctly the
drawings you are looking at. The design works and it can be
folded.
Years ago we had a guy that felt he
had to fix everything on the Kolb MKIII that he was
building. He made a valiant effort in completing the plane.
He must have spent 3-4 thousand extra hours working on all
the changes. Luckily he never completed the airplane. He was
a great guy and is still alive because he didn't ever
fly that plane.
My advice is build the plane
exactly by the plans. There are a few really good changes
that a few people have tried to tell you about
but???
If you absolutely must make all the
changes you are talking about get real good insurance for
your love ones and DO NOT call it a Kolb. Don't even
mention it started as a Kolb kit. Also please quit talking
about all the issues you think are wrong, somebody might
think you know what you are talking about and hurt
themselves too. Sorry the proof is in the massive hours in
the fleet.
Did anyone ever tell you about one
of the Kolb employees that took a plane up and intentionally
tried to tear the plane apart. He finally with considerable
effort ripped the wings off, he threw out a chute and later
fixed the point of failure. Our planes are well designed and
tested.
Even with all that evidence I will
still say my advice is worth what you paid for it.
Rick NeilsenRedrive VW Powered
On Tue, Mar 22, 2016
at 1:39 PM, Bill Berle <victorbravo(at)sbcglobal.net>
wrote:
--> Kolb-List message posted by:
Bill Berle <victorbravo(at)sbcglobal.net>
I wish I could have placed a bet in Las Vegas as to
how quickly some of the people would jump in and say that
these airplanes have X number of hours and Y number of
landings without failure. I would have been able to buy
another Kolb
With all due respect to everyone, I KNOW that these
airplanes are not falling out of the sky.
Now, also with all due respect, can someone with engineering
knowledge tell me, ON A TECHNICAL ENGINEERING level, how it
could EVER be considered as good design practice to
essentially cantilever a piano hinge off of a thin wall
round tube, with one line of rivets at the tangent contact
point, and with flight loads often perpendicular to that
axis, where that cantilever loaded hinge is not only
connecting two pieces of primary aircraft structure but also
attaching a primary control surface ?
Bill Berle
www.ezflaphandle.com
- safety & performance upgrade for light aircraft
www.grantstar.net
- winning proposals for non-profit and for-profit
entities
--------------------------------------------
On Tue, 3/22/16, Dennis
Rowe <rowedenny(at)windstream.net>
wrote:
Subject: Re: Kolb-List: Elevator/Stabilizer hinge
ass'y
To: kolb-list(at)matronics.com
Date: Tuesday, March 22, 2016, 9:59 AM
--> Kolb-List message posted by:
Dennis Rowe <rowedenny(at)windstream.net>
Somebody notify John Hauck, as Miss Pfer has around 4000
hours on her airframe and has taken an eighty horse and
two
100 horse Rotax 912 engines well toward their TBO! The
horizontal stabilizer must be ready to fall off at any
second.
Maybe I can get a good deal on her since her demise must
be
imminent. 😉
Bill, just build the dang Firestar to plans and fly it.
It
won't fall apart.
Dennis "Skid" Rowe
Mk-3 Rotax 690, with a stock Kolb empennage.😱
> On Mar 21, 2016, at 6:29 PM, Bill Berle <victorbravo(at)sbcglobal.net>
wrote:
>
> --> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net>
>
> I hope I'm wrong, but my review of the plans
indicated
that there is no traditional DIRECT structural connection
between the rear spar tube and the fuselage tube. All the
load paths have to take a serpentine route and go
rearward
through the elevator hinges first, and only then into the
U-joint and pivot bolt in the steel ring. If you removed
the
elevator hinges (from either the elevator or the
stabilizer), or if you took the pin out of the hinges,
you
could move the stabilizer up and down freely while the
elevator remained bolted to the fuselage.
>
> Even WITH all the hinges in place, all up and down
movement of the stabilizer is transmitted through the
rivets
that hold the hinge onto the tubes, and there is no
significant stiffness or bracing against this movement.
Essentially you could move the root end of the stabilizer
up
and down by hand and this movement would bend the
(un-supported section of) the hinge material. This would
attempt to pry the rivets out of the tube and/or bend the
thin metal back and forth.
>
> Also, because of this design the forward stabilizer
attach bolt must be a loose fit, and the stabilizer has
to
be able to slide back and forth a little.
>
> The only thing that is gained by this unusual
structural load path is that 4 ounces of weight for a
pair
of fittings (at the rear stabilizer spar) is saved. Can
any
one explain to me why this was a good bargain?
>
> Bill Berle
> www.ezflaphandle.com
- safety & performance
upgrade for light aircraft
> www.grantstar.net
- winning proposals for non-profit and
for-profit entities
>
> --------------------------------------------
> On Mon, 3/21/16, Richard Girard <aslsa.rng(at)gmail.com>
wrote:
>
> Subject: Re: Kolb-List: Elevator/Stabilizer hinge
ass'y
> To: "kolb-list(at)matronics.com"
<kolb-list(at)matronics.com>
> Date: Monday, March 21, 2016, 2:40 PM
>
> The rear attachment
> of the horizontal stabilizer is NOT through the
hinge.
It is
> through the rear folding weldments that also act as
the
> inner hinge. When it is set up correctly the hinge
line
is
> on the same center as the swivel bolt in the
weldment,
> however there is some allowance for misalignment. In
that
> case the weldment in the elevator spar (forward tube
of
the
> elevator), can slide on the bolt in the swivel
> weldment.I've seen folding mechanisms on the Kit
> Fox and repaired the mechanism on the Highlander and
in
my
> HO Homer's is the most clever. All you have to do
to
> fold the HS on a Kolb is to take out a single bolt
that
> attaches the lower wires to the rudder post. I'm
not
> sure how you would make it any simpler.
> Rick Girard
> On Mon, Mar 21, 2016
> at 12:55 PM, Bill Berle <victorbravo(at)sbcglobal.net>
> wrote:
> --> Kolb-List message posted by:
> Bill Berle <victorbravo(at)sbcglobal.net>
>
>
>
> Are there any Kolb people on this list who are
qualified
> mechanical or aero-structure engineers? I want to
ask
a
> question about the tail attachment mechanism.
>
>
>
> Before I even mention the question, I want to assure
> everyone that I AM COMPLETELY AWARE that there are X
> thousand Kolbs flying around safely with this
stabilizer
> attachment. I understand that there have not been
many
(or
> perhaps any) failures of this mechanism. What I am
asking
> about is the theoretical "correctness" of
the
> design, and whether any other "old-school"
> airplane people think that this system is a little
wonky.
>
>
>
> It took a few moments to finally understand how the
> mechanism works, and after looking at everything
several
> times it was clear that there is no direct
structural
> attachment between the main spar tube of the
stabilizer
to
> the fuselage tube (tailboom). The primary structural
load
> path between the root end of the main stabilizer
spar
tube
> and the fuselage is transmitted through the elevator
> hinge... and this hinge isn't even the aircraft
style
> extruded hinge.
>
>
>
> So if the air loads try to lift up or push down on
the
root
> end of the stabilizer, it puts all that load through
the
> hinge, into the elevator pivot, and then finally
into
the
> steel ring at the back of the fuselage.
>
>
>
> But that's not even the biggest issue in my head.
The
> larger issue is that (according to plan) the flat
hinge
is
> riveted to the tubes along one thin "point of
> contact" line tangent to the tube. So the root
> stabilizer load is all acting on a hinge, which
itself
is
> cantilevered off of one tangent point on the
tube.
>
>
>
> Now I'm not a degreed engineer, and I'm not
a
> mathematician. So I called a friend of mine who is a
retired
> aerospace structural engineer, with 50+ years of
experience.
> I showed him the plans and explained my concern, and
I
was
> informed that my concerns about this system were
valid.
My
> Kolb will be built with a more stable attachment.
>
>
>
> My question for any real, degreed, qualified,
> aircraft-experience engineers is... has anyone
looked
at the
> stabilizer root attachment load path and had these
same
> concerns?
>
>
>
> ONCE AGAIN, this is not an attack on Mr. Kolb or his
design,
> and it is not intended to cause any panic or concern
at
this
> point. What I want to know is why this load path -
through
> two tangent mounted hinge halves, into a movable
elevator,
> and then into the fuselage - is good enough, and why
it
was
> not appropriate to install an attachment bracket
onto
the
> fuselage at the rear stabilizer spar.
>
>
>
>
>
> Bill Berle
>
> www.ezflaphandle.com
> - safety & performance upgrade for light
aircraft
>
> www.grantstar.net
> - winning proposals for
non-profit and for-profit
> entities
>
>
>
>
>
> ===========
>
> br>
> fts!)
>
> r>
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>
>
>
>
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victorbravo(at)sbcglobal.
Guest
|
| Posted: Tue Mar 22, 2016 2:33 pm Post subject: Elevator/Stabilizer hinge ass'y |
|
|
Thank you Dave,
There was and is no intention of coming across like nobody else had thought this through. Quite the contrary; if I remember correctly, my first post on the subject that started all this turmoil was actually asking about whether other people had questioned this before I came along, and what the reasons were for designing that mechanism in a counter-intuitive manner. I was more surprised than anyone to find that I appeared to be the first person who asked about it.
Bill
On Tue, 3/22/16, undoctor <undoctor(at)rcn.com> wrote:
I believe the problem lies in that, whether or not you realize it, you come across as having the opinion that before you
came on the scene there was never anyone who could think things through as thoroughly and analytically as
you. Trust me when I tell you that that's a huge error.
Dave Kulp Bethlehem, PA
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victorbravo(at)sbcglobal.
Guest
|
| Posted: Tue Mar 22, 2016 3:03 pm Post subject: Elevator/Stabilizer hinge ass'y |
|
|
On Tue, 3/22/16, Larry Cottrell <lcottrell1020(at)gmail.com> wrote:
I have also seen several guys on the list that were convinced that a bit of this and a bit of that would
make the plane perform just fine with one of the other types of engines.
Again, you are a big boy, and apparently you have a better idea, by all mean have at it.
Nobody here cares if you can improve your plane.
just try to not tell me how stupid I am because mine does just exactly what I want and need.
Larry
--------------------------------------------
This aircraft will be flying over a densely populated area. I believe the vast majority of Kolbs are not being flown over populated areas... am I right about this? The majority of people who have flown with 2 stroke engines over time have had emergency landings due to inflight failures. Even the people who have figured out how to reliably operate the 2 strokes recommend against it when I say that I'm based out of a big city municipal airport. So my discussion about alternate engines was based on this reality. Believe me, it would be quick, cheap and easy to just bolt a 503 on the FireStar like it was designed for.
I'd be absolutely thankful if you would be able to recommend a truly reliable engine for this aircraft (for safe flying over a densely populated area) that is as affordable as a used 503 2 stroke. I already know where to look for engines that are not affordable.
I do NOT "have a better idea", I just have a different priority requirement than most of the Kolb operators do. I need something that is more reliable than the Rotax 2 strokes.
Did me or anyone else tell you that you were stupid, at any time, inferred or expressed?
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
|
| Posted: Tue Mar 22, 2016 3:32 pm Post subject: Elevator/Stabilizer hinge ass'y |
|
|
Bill B/Kolbers:
I'll tell you if there was a cheap, reliable, alternate four stroke power plant for a Kolb aircraft, it would be flying on a lot of Kolbs and other makes of ULs and home builts.
Sometimes one must pay for what he wants. I have. Haven't had an engine out in well over 3,000 hours. Did have a couple engine outs caused by bad fuel, but that was pilot error and had nothing to do with engine reliability.
Some of us have tried to share with you a little of our experience, but it seems you don't want to hear what we have to say.
By now you should recognize there is no elevator hinge problem. If you want to change yours when you get around to getting your hands dirty and actually building a Kolb, have at it.
john h
mkIII
Fort Campbell, Kentucky
--
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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