|
Sam Hoskins
The Sparrow Strainers are draggy and slow our planes down. There must be an alternative. Every time a speed specialist looks at the the sparrow strainers they go "WTF"?
So, let's start at the beginning. Why are there in the first place?
As I understand it, they are an aerodynamic trim designed to counteract the high pressure on the bottom of the canard elevator. Air wants to push the TE of the elevator up, causing the plane to dive, so the sparrow strainers help by pushing it back down.
Is this logic correct?
So, what would be a drag-free alternative? Well, I suppose one could increase the spring tension already used for the control stick. Why didn't QAC do something like that? Maybe it would increase the stick forces. Just guessing but when they first flew flew the new LS-1 airfoil, they probably found they needed an extraordinary amount of nose up trim. Followed by going with the cheapest fix - add sparrow strainers.
Another issue with using internal trim, is you are applying a constant torque to the joint there the elevator bellcrank slips into the elevator torque tube. Maybe it's not a big deal, bit it's there.
This is all supposition. Is anyone privy to the real story?
So, all of you aerodynamic tinkerers, what could be a viable way to eliminate the sparrow strainers?
Thanks for reading.
Sam
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|
|
Patrick Panzera
We went into great detail and debate over this a decade ago (or more!) on the Dragonfly list. and about the only thing that came of it is, 1) there are people who have flown w/o them- by adding more spring pressure by way of a static spring or a pitch trim device and 2) the only thing that the aerodynamic sparrow strainer has over a mechanical device is that as speed changes, so does the aerodynamic forces and they seem to stay in balance that way.
The torque tube issue was resolved for a flutter condition by welding a partial rib to the tube and inserting a plywood rib inside the very end of the elevator and bolting the two ribs together.
On Wed, Sep 18, 2013 at 2:14 PM, Sam Hoskins <sam.hoskins@...> wrote:
The Sparrow Strainers are draggy and slow our planes down. There must be an alternative. Every time a speed specialist looks at the the sparrow strainers they go "WTF"?
So, let's start at the beginning. Why are there in the first place?
As I understand it, they are an aerodynamic trim designed to counteract the high pressure on the bottom of the canard elevator. Air wants to push the TE of the elevator up, causing the plane to dive, so the sparrow strainers help by pushing it back down.
Is this logic correct?
So, what would be a drag-free alternative? Well, I suppose one could increase the spring tension already used for the control stick. Why didn't QAC do something like that? Maybe it would increase the stick forces. Just guessing but when they first flew flew the new LS-1 airfoil, they probably found they needed an extraordinary amount of nose up trim. Followed by going with the cheapest fix - add sparrow strainers.
Another issue with using internal trim, is you are applying a constant torque to the joint there the elevator bellcrank slips into the elevator torque tube. Maybe it's not a big deal, bit it's there.
This is all supposition. Is anyone privy to the real story?
So, all of you aerodynamic tinkerers, what could be a viable way to eliminate the sparrow strainers?
Thanks for reading.
Sam
|
|
|
Fisher Paul A. <fisherpaula@...>
Sam,
Your analysis is correct as I recall. Didn’t Gene used to race the QAC Q-200 without sparrow strainers? I thought he removed them for exactly the reason you
stated – they are draggy.
I would expect higher stick forces without the strainers. I have no clue if it would induce a flutter situation. As long as the controls are balanced, I would
assume not. But it is certainly something that would have to be flight tested.
Having to constantly hold back pressure would indeed put additional strain on the elevator attach mechanisms (including the torque tube to the inside of the elevator).
I would think you would want to verify each connection would handle the additional strain because without the strainers that pressure would be constant plus any additional loads as you hit turbulence, etc.
As long as you are asking aerodynamic questions, is the LS-1 airfoil still the best option? I thought John Roncz came up with a new airfoil for the LongEZ canard
to address the same issues the LS-1 was trying to address. Of course for all I know, they are the same airfoil!! ;-) I suppose it depends on how much “design” work you want to do and how fast you want to get back into the air!
- Paul
toggle quoted messageShow quoted text
From: Q-LIST@... [mailto:Q-LIST@...]
On Behalf Of Sam Hoskins
Sent: Wednesday, September 18, 2013 4:15 PM
To: Quickie List
Subject: [Q-LIST] Need a Sparrow Strainer alternative
The Sparrow Strainers are draggy and slow our planes down. There must be an alternative. Every time a speed specialist looks at the the sparrow strainers they go "WTF"?
So, let's start at the beginning. Why are there in the first place?
As I understand it, they are an aerodynamic trim designed to counteract the high pressure on the bottom of the canard elevator. Air wants to push the TE of the elevator up, causing the plane to dive, so the sparrow strainers help by pushing
it back down.
So, what would be a drag-free alternative? Well, I suppose one could increase the spring tension already used for the control stick. Why didn't QAC do something like that? Maybe it would increase the stick forces. Just guessing but
when they first flew flew the new LS-1 airfoil, they probably found they needed an extraordinary amount of nose up trim. Followed by going with the cheapest fix - add sparrow strainers.
Another issue with using internal trim, is you are applying a constant torque to the joint there the elevator bellcrank slips into the elevator torque tube. Maybe it's not a big deal, bit it's there.
This is all supposition. Is anyone privy to the real story?
So, all of you aerodynamic tinkerers, what could be a viable way to eliminate the sparrow strainers?
|
|
|
All I know is that if one comes off in
flight, you are flipped negative G's nose down with a violent roll
to the near inverted. Don't ask me how I know.
toggle quoted messageShow quoted text
On 9/18/2013 5:14 PM, Sam Hoskins wrote:
The Sparrow Strainers are draggy and slow our
planes down. There must be an alternative. Every time a
speed specialist looks at the the sparrow strainers they
go "WTF"?
So, let's start at the beginning. Why are there in
the first place?
As I understand it, they are an aerodynamic trim
designed to counteract the high pressure on the bottom
of the canard elevator. Air wants to push the TE of the
elevator up, causing the plane to dive, so the sparrow
strainers help by pushing it back down.
Is this logic correct?
So, what would be a drag-free alternative? Well, I
suppose one could increase the spring tension already
used for the control stick. Why didn't QAC
do something like that? Maybe it would increase the
stick forces. Just guessing but when they first flew
flew the new LS-1 airfoil, they probably found they
needed an extraordinary amount of nose up trim.
Followed by going with the cheapest fix - add sparrow
strainers.
Another issue with using internal trim, is you are
applying a constant torque to the joint there the
elevator bellcrank slips into the elevator torque tube.
Maybe it's not a big deal, bit it's there.
This is all supposition. Is anyone privy to the real
story?
So, all of you aerodynamic
tinkerers, what could be a viable way to eliminate the
sparrow strainers?
Thanks for reading.
Sam
|
|
|
Bruce Crain
|
|
|
Jason Nemake <fg13fg@...>
Guys,
Are the elevator control surfaces statically balanced on the LS airfoil, like they are on the GU airfoil? If so, then I would guess that if you unbalanced the control surface and started increasing the cg of the control surface aft, to try and cancel the lifting effect caused by the LS cuspt then heavy springs or sparrow strainers might not be needed. One could possibly go as far as weighting the trailing edge. The result would be a drooped elevator on the ground until reaching flying speeds, and a positive effect on the stick at low speeds. Maybe even a combination of springs and aft weight. There of coarse would be G effects to this idea. Some things to ponder..
Jason Nemake
From: "jcrain2@..."
To: Q-LIST@...
Sent: Wednesday, September 18, 2013 8:55 PM
Subject: Re: [Q-LIST] Need a Sparrow Strainer alternative
Sammy,
Didn't Tom Moore and Bob Malecek have an adjustable flat piece of aluminum or stainless in place of the upside down airfoil? I think it had a slight up kicker at the back though. Call them to see what their ideas were. It might be a bit less drag perhaps X 2.
Bruce ---------- Original Message ---------- From: Sam Hoskins To: Quickie List Subject: [Q-LIST] Need a Sparrow Strainer alternative Date: Wed, 18 Sep 2013 16:14:44 -0500
The Sparrow Strainers are draggy and slow our planes down. �There must be an alternative. �Every time a speed specialist looks at the the sparrow strainers they go "WTF"?
So, let's start at the beginning. �Why are there in the first place?
As I understand it, they are an aerodynamic trim designed to counteract the high pressure on the bottom of the canard elevator. �Air wants to push the TE of the elevator up, causing the plane to dive, so the sparrow strainers help by pushing it back down.
Is this logic correct?
So, what would be a drag-free alternative? �Well, I suppose one could increase the spring tension already used for the control stick. �Why didn't QAC do something like that? �Maybe it would increase the stick forces. �Just guessing but when they first flew flew the new �LS-1 airfoil, they probably found they needed an extraordinary amount of nose up trim. �Followed by going with the cheapest fix - add sparrow strainers.
Another issue with using internal trim, is you are applying a constant torque to the joint there the elevator bellcrank slips into the elevator torque tube. �Maybe it's not a big deal, bit it's there.
This is all supposition. �Is anyone privy to the real story?
So, all of you aerodynamic tinkerers, what could be a viable way to eliminate the sparrow strainers?
Thanks for reading.
Sam
____________________________________________________________30-second trick for a flat belly
This daily 30-second trick BOOSTS your body's #1 fat-burning hormone
TheFatBurningHormone.com
|
|
|
Patrick Panzera
Adding weight aft of the center of rotation is a sure recipe for flutter. Even at low speeds, a little bump could start it.
Look how stable a car's antenna is under normal conditions.
Now imaging a weight at the tip... or note what happens to it when weight is added from ice.
On Thu, Sep 19, 2013 at 8:15 AM, Jason Nemake <fg13fg@...> wrote:
Guys,
Are the elevator control surfaces statically balanced on the LS airfoil, like they are on the GU airfoil? If so, then I would guess that if you unbalanced the control surface and started increasing the cg of the control surface aft, to try and cancel the lifting effect caused by the LS cuspt then heavy springs or sparrow strainers might not be needed. One could possibly go as far as weighting the trailing edge. The result would be a drooped elevator on the ground until reaching flying speeds, and a positive effect on the stick at low speeds. Maybe even a combination of springs and aft weight. There of coarse would be G effects to this idea. Some things to ponder..
Jason Nemake
Sammy,
Didn't Tom Moore and Bob Malecek have an adjustable flat piece of aluminum or stainless in place of the upside down airfoil? I think it had a slight up kicker at the back though. Call them to see what their ideas were. It might be a bit less drag perhaps X 2.
Bruce ---------- Original Message ---------- From: Sam Hoskins < sam.hoskins@...> To: Quickie List < Q-LIST@...> Subject: [Q-LIST] Need a Sparrow Strainer alternative Date: Wed, 18 Sep 2013 16:14:44 -0500
The Sparrow Strainers are draggy and slow our planes down. �There must be an alternative. �Every time a speed specialist looks at the the sparrow strainers they go "WTF"?
So, let's start at the beginning. �Why are there in the first place?
As I understand it, they are an aerodynamic trim designed to counteract the high pressure on the bottom of the canard elevator. �Air wants to push the TE of the elevator up, causing the plane to dive, so the sparrow strainers help by pushing it back down.
Is this logic correct?
So, what would be a drag-free alternative? �Well, I suppose one could increase the spring tension already used for the control stick. �Why didn't QAC do something like that? �Maybe it would increase the stick forces. �Just guessing but when they first flew flew the new �LS-1 airfoil, they probably found they needed an extraordinary amount of nose up trim. �Followed by going with the cheapest fix - add sparrow strainers.
Another issue with using internal trim, is you are applying a constant torque to the joint there the elevator bellcrank slips into the elevator torque tube. �Maybe it's not a big deal, bit it's there.
This is all supposition. �Is anyone privy to the real story?
So, all of you aerodynamic tinkerers, what could be a viable way to eliminate the sparrow strainers?
Thanks for reading.
Sam
____________________________________________________________30-second trick for a flat belly
This daily 30-second trick BOOSTS your body's #1 fat-burning hormone
TheFatBurningHormone.com
|
|
|
Patrick Panzera
BTW, when I was the Dragonfly newsletter editor, Terry O'Neill submitted an excellent article on how he did away with his sparrow strainers by installing anti-servo tabs that are also used as an aerodynamic pitch trim system. He also talks about balancing the elevators to avoid flutter.
I just uploaded the entire issue.
And if I uploaded it properly, it should download to a printable PDF.
Pat
On Thu, Sep 19, 2013 at 9:10 AM, Patrick Panzera <editor@...> wrote:
Adding weight aft of the center of rotation is a sure recipe for flutter. Even at low speeds, a little bump could start it.
Look how stable a car's antenna is under normal conditions.
Now imaging a weight at the tip... or note what happens to it when weight is added from ice.
|
|
|
But wait - doesn't an anti-servo tab and a sparrow strainer do the same thing? Namely, produce an aerodynamic down force on the elevator. Remember that the sparrow strainers are constructed with an airfoil. Airfoils have very little parasitic drag compaired to other shapes. Why would you think that a servo tab as less parasitic drag than a sparrow strainer? Spoken by a novice - let the experts come in on this :-). Jim Patrick Panzera wrote:
BTW, when I was the Dragonfly newsletter editor, Terry O'Neill submitted
an excellent article on how he did away with his sparrow strainers by
installing anti-servo tabs that are also used as an aerodynamic pitch
trim system. He also talks about balancing the elevators to avoid flutter.
I just uploaded the entire issue.
http://issuu.com/contact.magazine/docs/dragonfly_newsletter_97
And if I uploaded it properly, it should download to a printable PDF.
Pat
On Thu, Sep 19, 2013 at 9:10 AM, Patrick Panzera
<editor@... <mailto:editor@...>> wrote:
Adding weight aft of the center of rotation is a sure recipe for
flutter.
Even at low speeds, a little bump could start it.
Look how stable a car's antenna is under normal conditions.
Now imaging a weight at the tip... or note what happens to it when
weight is added from ice.
On Thu, Sep 19, 2013 at 8:15 AM, Jason Nemake <fg13fg@...
<mailto:fg13fg@...>> wrote:
__
Guys,
Are the elevator control surfaces statically balanced on the LS
airfoil, like they are on the GU airfoil? If so, then I would
guess that if you unbalanced the control surface and started
increasing the cg of the control surface aft, to try and cancel
the lifting effect caused by the LS cuspt then heavy springs or
sparrow strainers might not be needed. One could possibly go as
far as weighting the trailing edge. The result would be a
drooped elevator on the ground until reaching flying speeds, and
a positive effect on the stick at low speeds. Maybe even a
combination of springs and aft weight. There of coarse would be
G effects to this idea. Some things to ponder..
Jason Nemake
*From:* "jcrain2@... <mailto:jcrain2@...>"
<jcrain2@... <mailto:jcrain2@...>>
*To:* Q-LIST@... <mailto:Q-LIST@...>
*Sent:* Wednesday, September 18, 2013 8:55 PM
*Subject:* Re: [Q-LIST] Need a Sparrow Strainer alternative
__
Sammy,
Didn't Tom Moore and Bob Malecek have an adjustable flat piece
of aluminum or stainless in place of the upside down airfoil? I
think it had a slight up kicker at the back though. Call them
to see what their ideas were. It might be a bit less drag
perhaps X 2.
Bruce ____---------- Original Message ----------__From: Sam
Hoskins <sam.hoskins@...
<mailto:sam.hoskins@...>>__To: Quickie List
<Q-LIST@...
<mailto:Q-LIST@...>>__Subject: [Q-LIST] Need a
Sparrow Strainer alternative__Date: Wed, 18 Sep 2013 16:14:44
-0500____
The Sparrow Strainers are draggy and slow our planes down.
�There must be an alternative. �Every time a speed specialist
looks at the the sparrow strainers they go "WTF"?
So, let's start at the beginning. �Why are there in the first place?
As I understand it, they are an aerodynamic trim designed to
counteract the high pressure on the bottom of the canard
elevator. �Air wants to push the TE of the elevator up, causing
the plane to dive, so the sparrow strainers help by pushing it
back down.
Is this logic correct?
So, what would be a drag-free alternative? �Well, I suppose one
could increase the spring tension already used for the control
stick. �Why didn't QAC do something like that? �Maybe it would
increase the stick forces. �Just guessing but when they first
flew flew the new �LS-1 airfoil, they probably found they needed
an extraordinary amount of nose up trim. �Followed by going with
the cheapest fix - add sparrow strainers.
Another issue with using internal trim, is you are applying a
constant torque to the joint there the elevator bellcrank slips
into the elevator torque tube. �Maybe it's not a big deal, bit
it's there.
This is all supposition. �Is anyone privy to the real story?
So, all of you aerodynamic tinkerers, what could be a viable way
to eliminate the sparrow strainers?
Thanks for reading.
Sam
__________________________________________________________________*30-second
trick for a flat belly*
This daily 30-second trick BOOSTS your body's #1 fat-burning hormone
<http://thirdpartyoffers.juno.com/TGL3132/523a75e01b0875df585dst01vuc>TheFatBurningHormone.com
<http://thirdpartyoffers.juno.com/TGL3132/523a75e01b0875df585dst01vuc>
____
No virus found in this message.
Checked by AVG - www.avg.com <http://www.avg.com>
Version: 2013.0.3408 / Virus Database: 3222/6678 - Release Date: 09/18/13
-- Porcine Associates LLC 244 O'Connor St. Menlo Park, CA 94025 USA +1(650)326-2669 fax +1(650)326-1071 [Non-text portions of this message have been removed]
|
|
|
Patrick Panzera
Because when done properly it is in fact marginally cleaner.
I'm just offering alternates.
It's also impossible to get knocked off by someone's unsuspecting shin. :)
And nearly impossible to come off in flight.
On Thu, Sep 19, 2013 at 9:40 AM, Jim Ham <jimham@...> wrote:
But wait - doesn't an anti-servo tab and a sparrow strainer do the same
thing? Namely, produce an aerodynamic down force on the elevator.
Remember that the sparrow strainers are constructed with an airfoil.
Airfoils have very little parasitic drag compaired to other shapes. Why
would you think that a servo tab as less parasitic drag than a sparrow
strainer?
Spoken by a novice - let the experts come in on this :-).
Jim
Patrick Panzera wrote:
>
>
> BTW, when I was the Dragonfly newsletter editor, Terry O'Neill submitted
> an excellent article on how he did away with his sparrow strainers by
> installing anti-servo tabs that are also used as an aerodynamic pitch
> trim system. He also talks about balancing the elevators to avoid flutter.
>
> I just uploaded the entire issue.
>
> http://issuu.com/contact.magazine/docs/dragonfly_newsletter_97
>
> And if I uploaded it properly, it should download to a printable PDF.
>
> Pat
>
>
> On Thu, Sep 19, 2013 at 9:10 AM, Patrick Panzera
> < editor@... editor@...>> wrote:
>
> Adding weight aft of the center of rotation is a sure recipe for
> flutter.
> Even at low speeds, a little bump could start it.
>
> Look how stable a car's antenna is under normal conditions.
> Now imaging a weight at the tip... or note what happens to it when
> weight is added from ice.
>
>
> On Thu, Sep 19, 2013 at 8:15 AM, Jason Nemake < fg13fg@...
> fg13fg@...>> wrote:
>
> __
>
> Guys,
> Are the elevator control surfaces statically balanced on the LS
> airfoil, like they are on the GU airfoil? If so, then I would
> guess that if you unbalanced the control surface and started
> increasing the cg of the control surface aft, to try and cancel
> the lifting effect caused by the LS cuspt then heavy springs or
> sparrow strainers might not be needed. One could possibly go as
> far as weighting the trailing edge. The result would be a
> drooped elevator on the ground until reaching flying speeds, and
> a positive effect on the stick at low speeds. Maybe even a
> combination of springs and aft weight. There of coarse would be
> G effects to this idea. Some things to ponder..
> Jason Nemake
>
> *From:* " jcrain2@... jcrain2@...>"
> < jcrain2@... jcrain2@...>>
> *To:* Q-LIST@... Q-LIST@...>
> *Sent:* Wednesday, September 18, 2013 8:55 PM
> *Subject:* Re: [Q-LIST] Need a Sparrow Strainer alternative
> __
> Sammy,
> Didn't Tom Moore and Bob Malecek have an adjustable flat piece
> of aluminum or stainless in place of the upside down airfoil? I
> think it had a slight up kicker at the back though. Call them
> to see what their ideas were. It might be a bit less drag
> perhaps X 2.
> Bruce ____---------- Original Message ----------__From: Sam
> Hoskins < sam.hoskins@...
> sam.hoskins@...>>__To: Quickie List
> < Q-LIST@...
> Q-LIST@...>>__Subject: [Q-LIST] Need a
> Sparrow Strainer alternative__Date: Wed, 18 Sep 2013 16:14:44
> -0500____
> The Sparrow Strainers are draggy and slow our planes down.
> �There must be an alternative. �Every time a speed specialist
> looks at the the sparrow strainers they go "WTF"?
> So, let's start at the beginning. �Why are there in the first place?
> As I understand it, they are an aerodynamic trim designed to
> counteract the high pressure on the bottom of the canard
> elevator. �Air wants to push the TE of the elevator up, causing
> the plane to dive, so the sparrow strainers help by pushing it
> back down.
> Is this logic correct?
> So, what would be a drag-free alternative? �Well, I suppose one
> could increase the spring tension already used for the control
> stick. �Why didn't QAC do something like that? �Maybe it would
> increase the stick forces. �Just guessing but when they first
> flew flew the new �LS-1 airfoil, they probably found they needed
> an extraordinary amount of nose up trim. �Followed by going with
> the cheapest fix - add sparrow strainers.
> Another issue with using internal trim, is you are applying a
> constant torque to the joint there the elevator bellcrank slips
> into the elevator torque tube. �Maybe it's not a big deal, bit
> it's there.
> This is all supposition. �Is anyone privy to the real story?
> So, all of you aerodynamic tinkerers, what could be a viable way
> to eliminate the sparrow strainers?
> Thanks for reading.
> Sam
> __________________________________________________________*30-second
> trick for a flat belly*
> This daily 30-second trick BOOSTS your body's #1 fat-burning hormone
> < http://thirdpartyoffers.juno.com/TGL3132/523a75e01b0875df585dst01vuc>TheFatBurningHormone.com
> < http://thirdpartyoffers.juno.com/TGL3132/523a75e01b0875df585dst01vuc>
> ____
>
>
>
>
>
>
>
> No virus found in this message.
> Checked by AVG - www.avg.com < http://www.avg.com>
> Version: 2013.0.3408 / Virus Database: 3222/6678 - Release Date: 09/18/13
>
--
Porcine Associates LLC
244 O'Connor St.
Menlo Park, CA 94025
USA
+1(650)326-2669 fax +1(650)326-1071
|
|
|
Patrick Panzera
Another thought that was fully discussed on the DF list a long time back, was to simply reflex the entire span of the trailing edge of the elevator. What was inconclusive was if it would net less drag than the sparrow strainer.
On Thu, Sep 19, 2013 at 9:45 AM, Patrick Panzera <editor@...> wrote:
Because when done properly it is in fact marginally cleaner.
I'm just offering alternates.
It's also impossible to get knocked off by someone's unsuspecting shin. :)
And nearly impossible to come off in flight.
|
|
|
I just thought of another plus for the sparrow strainer. It is placed below and behind the trailing edge of the elevator. This does two things: It puts it in relatively undisturbed air and it increased the lever arm on the elevator. Greater lever arm means lower down force needed and lower induced drag for the same torque on the elevator. But wait - doesn't an anti-servo tab and a sparrow strainer do the same thing? Namely, produce an aerodynamic down force on the elevator. Remember that the sparrow strainers are constructed with an airfoil. Airfoils have very little parasitic drag compaired to other shapes. Why would you think that a servo tab as less parasitic drag than a sparrow strainer?
Spoken by a novice - let the experts come in on this :-). Jim Patrick Panzera wrote:
BTW, when I was the Dragonfly newsletter editor, Terry O'Neill submitted
an excellent article on how he did away with his sparrow strainers by
installing anti-servo tabs that are also used as an aerodynamic pitch
trim system. He also talks about balancing the elevators to avoid flutter.
I just uploaded the entire issue.
http://issuu.com/contact.magazine/docs/dragonfly_newsletter_97
And if I uploaded it properly, it should download to a printable PDF.
Pat
On Thu, Sep 19, 2013 at 9:10 AM, Patrick Panzera
<editor@... <mailto:editor@...>> wrote:
Adding weight aft of the center of rotation is a sure recipe for
flutter.
Even at low speeds, a little bump could start it.
Look how stable a car's antenna is under normal conditions.
Now imaging a weight at the tip... or note what happens to it when
weight is added from ice.
On Thu, Sep 19, 2013 at 8:15 AM, Jason Nemake <fg13fg@...
<mailto:fg13fg@...>> wrote:
__
Guys,
Are the elevator control surfaces statically balanced on the LS
airfoil, like they are on the GU airfoil? If so, then I would
guess that if you unbalanced the control surface and started
increasing the cg of the control surface aft, to try and cancel
the lifting effect caused by the LS cuspt then heavy springs or
sparrow strainers might not be needed. One could possibly go as
far as weighting the trailing edge. The result would be a
drooped elevator on the ground until reaching flying speeds, and
a positive effect on the stick at low speeds. Maybe even a
combination of springs and aft weight. There of coarse would be
G effects to this idea. Some things to ponder..
Jason Nemake
*From:* "jcrain2@... <mailto:jcrain2@...>"
<jcrain2@... <mailto:jcrain2@...>>
*To:* Q-LIST@... <mailto:Q-LIST@...>
*Sent:* Wednesday, September 18, 2013 8:55 PM
*Subject:* Re: [Q-LIST] Need a Sparrow Strainer alternative
__
Sammy,
Didn't Tom Moore and Bob Malecek have an adjustable flat piece
of aluminum or stainless in place of the upside down airfoil? I
think it had a slight up kicker at the back though. Call them
to see what their ideas were. It might be a bit less drag
perhaps X 2.
Bruce ____---------- Original Message ----------__From: Sam
Hoskins <sam.hoskins@...
<mailto:sam.hoskins@...>>__To: Quickie List
<Q-LIST@...
<mailto:Q-LIST@...>>__Subject: [Q-LIST] Need a
Sparrow Strainer alternative__Date: Wed, 18 Sep 2013 16:14:44
-0500____
The Sparrow Strainers are draggy and slow our planes down.
There must be an alternative. Every time a speed specialist
looks at the the sparrow strainers they go "WTF"?
So, let's start at the beginning. Why are there in the first place?
As I understand it, they are an aerodynamic trim designed to
counteract the high pressure on the bottom of the canard
elevator. Air wants to push the TE of the elevator up, causing
the plane to dive, so the sparrow strainers help by pushing it
back down.
Is this logic correct?
So, what would be a drag-free alternative? Well, I suppose one
could increase the spring tension already used for the control
stick. Why didn't QAC do something like that? Maybe it would
increase the stick forces. Just guessing but when they first
flew flew the new LS-1 airfoil, they probably found they needed
an extraordinary amount of nose up trim. Followed by going with
the cheapest fix - add sparrow strainers.
Another issue with using internal trim, is you are applying a
constant torque to the joint there the elevator bellcrank slips
into the elevator torque tube. Maybe it's not a big deal, bit
it's there.
This is all supposition. Is anyone privy to the real story?
So, all of you aerodynamic tinkerers, what could be a viable way
to eliminate the sparrow strainers?
Thanks for reading.
Sam
__________________________________________________________________*30-second
trick for a flat belly*
This daily 30-second trick BOOSTS your body's #1 fat-burning hormone
<http://thirdpartyoffers.juno.com/TGL3132/523a75e01b0875df585dst01vuc>TheFatBurningHormone.com
<http://thirdpartyoffers.juno.com/TGL3132/523a75e01b0875df585dst01vuc>
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-- Porcine Associates LLC 244 O'Connor St. Menlo Park, CA 94025 USA +1(650)326-2669 fax +1(650)326-1071
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rick_nordgarden
Do a web search on "Gurney flap". Dan Gurney put the first one on Bobby Unser's Eagle Indy car in 1971; it's now widely used on aircraft, especially helicopter tail surfaces. It's a length of (usually) aluminum angle at the trailing edge of an airfoil that alters the airflow in ways that increase the pressure on the Gurney-equipped side of the surface and decrease it on the other side with little or no increase in drag; i.e., it improves the L/D while also increasing lift or downforce.
I'm going to try Gurney flaps as a substitute for sparrow strainers once I get my Dragonfly flying. I'll remove one strainer and replace it with, say, two feet of Gurney; if high-speed runway testing goes okay I'll try a flight. I'll change the span of the Gurney flap until its effect matches that of the sparrow strainer, then put an identical one on the other side. Careful before/after testing *may* reveal a speed improvement, but I'll settle for no loss -- the robustness of a Gurney alone would make it worth using.
The keys to making Gurney flaps work efficiently are to keep them within the boundary layer -- they seem never to be more than about three-eighths of an inch tall -- and not to mount them so that they form a ledge on the opposite side of the trailing edge since this destroys the smooth flow out from under. It also might help, and might even prove essential, to put fences on the ends -- on racing cars they're always configured that way, while the aircraft applications all seem to be full-span, possibly obviating the need for end-fences. Full-span Gurneys would seem to be too much for this application, though only flight-testing will tell. Worth a try, I think.
Rick Nordgarden
Council Bluffs IA
Dragonfly Mk. II-H, installing systems...
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Patrick Panzera
This is what I was talking about when I said we discussed "reflexing" the trailing edge. ...just not as drastic.
On Thu, Sep 19, 2013 at 10:59 AM, rick_nordgarden <grnordgarden@...> wrote:
Do a web search on "Gurney flap". Dan Gurney put the first one on Bobby Unser's Eagle Indy car in 1971; it's now widely used on aircraft, especially helicopter tail surfaces. It's a length of (usually) aluminum angle at the trailing edge of an airfoil that alters the airflow in ways that increase the pressure on the Gurney-equipped side of the surface and decrease it on the other side with little or no increase in drag; i.e., it improves the L/D while also increasing lift or downforce.
I'm going to try Gurney flaps as a substitute for sparrow strainers once I get my Dragonfly flying. I'll remove one strainer and replace it with, say, two feet of Gurney; if high-speed runway testing goes okay I'll try a flight. I'll change the span of the Gurney flap until its effect matches that of the sparrow strainer, then put an identical one on the other side. Careful before/after testing *may* reveal a speed improvement, but I'll settle for no loss -- the robustness of a Gurney alone would make it worth using.
The keys to making Gurney flaps work efficiently are to keep them within the boundary layer -- they seem never to be more than about three-eighths of an inch tall -- and not to mount them so that they form a ledge on the opposite side of the trailing edge since this destroys the smooth flow out from under. It also might help, and might even prove essential, to put fences on the ends -- on racing cars they're always configured that way, while the aircraft applications all seem to be full-span, possibly obviating the need for end-fences. Full-span Gurneys would seem to be too much for this application, though only flight-testing will tell. Worth a try, I think.
Rick Nordgarden
Council Bluffs IA
Dragonfly Mk. II-H, installing systems...
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YEARS ago I had one sparrow strainer depart depart in level flight at 160mph and the stick was literally pulled out of my hand. It caused a severe nose down attitude. I talked to Gene S about this as he took the strainers off for a race. He said flying with no strainers made for a very difficult flight and did not think it resulted in a big difference in top speed. Greg Z 89RZ
toggle quoted messageShow quoted text
-----Original Message-----
From: rick_nordgarden
To: Q-LIST
Sent: Thu, Sep 19, 2013 1:08 pm
Subject: [Q-LIST] Re: Need a Sparrow Strainer alternative
Do a web search on "Gurney flap". Dan Gurney put the first one on Bobby Unser's
Eagle Indy car in 1971; it's now widely used on aircraft, especially helicopter
tail surfaces. It's a length of (usually) aluminum angle at the trailing edge
of an airfoil that alters the airflow in ways that increase the pressure on the
Gurney-equipped side of the surface and decrease it on the other side with
little or no increase in drag; i.e., it improves the L/D while also increasing
lift or downforce.
I'm going to try Gurney flaps as a substitute for sparrow strainers once I get
my Dragonfly flying. I'll remove one strainer and replace it with, say, two
feet of Gurney; if high-speed runway testing goes okay I'll try a flight. I'll
change the span of the Gurney flap until its effect matches that of the sparrow
strainer, then put an identical one on the other side. Careful before/after
testing *may* reveal a speed improvement, but I'll settle for no loss -- the
robustness of a Gurney alone would make it worth using.
The keys to making Gurney flaps work efficiently are to keep them within the
boundary layer -- they seem never to be more than about three-eighths of an inch
tall -- and not to mount them so that they form a ledge on the opposite side of
the trailing edge since this destroys the smooth flow out from under. It also
might help, and might even prove essential, to put fences on the ends -- on
racing cars they're always configured that way, while the aircraft applications
all seem to be full-span, possibly obviating the need for end-fences. Full-span
Gurneys would seem to be too much for this application, though only
flight-testing will tell. Worth a try, I think.
Rick Nordgarden
Council Bluffs IA
Dragonfly Mk. II-H, installing systems...
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Hi, Unbalancing a control surface as you suggest is an extremely bad idea; it is making flutter more likely. I am sure the designers looked at other possibilities before settling on the sparrow strainers. Changes to control systems are very experimental; do it at your own risk.
toggle quoted messageShow quoted text
----- Original Message -----
Sent: 9/19/2013 8:35:29 AM
Subject: Re: [Q-LIST] Need a Sparrow Strainer alternative
Guys,
Are the elevator control surfaces statically balanced on the LS airfoil, like they are on the GU airfoil? If so, then I would guess that if you unbalanced the control surface and started increasing the cg of the control surface aft, to try and cancel the lifting effect caused by the LS cuspt then heavy springs or sparrow strainers might not be needed. One could possibly go as far as weighting the trailing edge. The result would be a drooped elevator on the ground until reaching flying speeds, and a positive effect on the stick at low speeds. Maybe even a combination of springs and aft weight. There of coarse would be G effects to this idea. Some things to ponder..
Jason Nemake
From: "jcrain2@..."
To: Q-LIST@...
Sent: Wednesday, September 18, 2013 8:55 PM
Subject: Re: [Q-LIST] Need a Sparrow Strainer alternative
Sammy,
Didn't Tom Moore and Bob Malecek have an adjustable flat piece of aluminum or stainless in place of the upside down airfoil? I think it had a slight up kicker at the back though. Call them to see what their ideas were. It might be a bit less drag perhaps X 2.
Bruce ---------- Original Message ---------- From: Sam Hoskins To: Quickie List Subject: [Q-LIST] Need a Sparrow Strainer alternative Date: Wed, 18 Sep 2013 16:14:44 -0500
The Sparrow Strainers are draggy and slow our planes down. There must be an alternative. Every time a speed specialist looks at the the sparrow strainers they go "WTF"?
So, let's start at the beginning. Why are there in the first place?
As I understand it, they are an aerodynamic trim designed to counteract the high pressure on the bottom of the canard elevator. Air wants to push the TE of the elevator up, causing the plane to dive, so the sparrow strainers help by pushing it back down.
Is this logic correct?
So, what would be a drag-free alternative? Well, I suppose one could increase the spring tension already used for the control stick. Why didn't QAC do something like that? Maybe it would increase the stick forces. Just guessing but when they first flew flew the new LS-1 airfoil, they probably found they needed an extraordinary amount of nose up trim. Followed by going with the cheapest fix - add sparrow strainers.
Another issue with using internal trim, is you are applying a constant torque to the joint there the elevator bellcrank slips into the elevator torque tube. Maybe it's not a big deal, bit it's there.
This is all supposition. Is anyone privy to the real story?
So, all of you aerodynamic tinkerers, what could be a viable way to eliminate the sparrow strainers?
Thanks for reading.
Sam
____________________________________________________________30-second trick for a flat belly
This daily 30-second trick BOOSTS your body's #1 fat-burning hormone
TheFatBurningHormone.com
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Wait. . . I just looked up "gurney flap" in wikepedia. . .wouldn't a "gurney flap" push the trailing edge of the elevator UP and the nose DOWN? That seems to be the opposite of what the sparrow strainer is trying to accomplish. Just FYI.
The TE of the LS1 elevator is curved down. . . the sparrow strainer causes a DOWN force on the TE to reduce AFT stick forces. Perhaps you would need to install "Gurney Spoilers" but that might cause even more problems. :-)
Also not sure how you "increase lift or downforce." What does that even mean?
Dan Yager
QBA Editor
www.quickheads.com
On 2013-09-19 13:59, rick_nordgarden wrote:
Do a web search on "Gurney flap". Dan Gurney put the first one on Bobby Unser's Eagle Indy car in 1971; it's now widely used on aircraft, especially helicopter tail surfaces. It's a length of (usually) aluminum angle at the trailing edge of an airfoil that alters the airflow in ways that increase the pressure on the Gurney-equipped side of the surface and decrease it on the other side with little or no increase in drag; i.e., it improves the L/D while also increasing lift or downforce.
Rick Nordgarden
Council Bluffs IA
Dragonfly Mk. II-H, installing systems...
|
|
|
rick_nordgarden
--- In Q-LIST@..., dan@... wrote:
Wait. . . I just looked up "gurney flap" in wikepedia. . .wouldn't a
"gurney flap" push the trailing edge of the elevator UP and the nose
DOWN? That seems to be the opposite of what the sparrow strainer is
trying to accomplish. Just FYI.
The TE of the LS1 elevator is curved
down. . . the sparrow strainer causes a DOWN force on the TE to reduce
AFT stick forces. Perhaps you would need to install "Gurney Spoilers"
but that might cause even more problems. :-)
Also not sure how you
"increase lift or downforce." What does that even mean?
Dan Yager
QBA
Editor
www.quickheads.com [1]
I wrote "lift or downforce" because which one the flap produces depends on whether it's placed on the upper or lower surface of the trailing ege: upper-surface placement promotes downforce which would make the Gurney a functional equivalent of the sparrow-strainer. I expect to do some experimenting to find the optimum Gurney span to duplicate the trim effect of the original winglet but high-speed runway tests should indicate whether the trim force is in the ballpark and a flight may be attempted. As for the sudden change in trim force when a sparrow strainer departs, that's exactly the reason to use a Gurney flap instead: it's just a little lip glued onto the elevator, sturdy and difficult to dislodge. Could be made from carbon-fiber BID and glued on with a structural adhesive such as Hysol, adding less weight behind the elevator's hinge line than a winglet. As I said, well worth trying... Rick Nordgarden
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One Sky Dog
Jim,
Sparrow strainers are also proportional to the speed so the right correction is applied at all air speeds automatically.
Regards,
Charlie Johnson
toggle quoted messageShow quoted text
On Sep 19, 2013, at 10:55 AM, Jim Ham <jimham@...> wrote: I just thought of another plus for the sparrow strainer. It is placed
below and behind the trailing edge of the elevator. This does two
things: It puts it in relatively undisturbed air and it increased the
lever arm on the elevator. Greater lever arm means lower down force
needed and lower induced drag for the same torque on the elevator.
But wait - doesn't an anti-servo tab and a sparrow strainer do the same thing? Namely, produce an aerodynamic down force on the elevator. Remember that the sparrow strainers are constructed with an airfoil. Airfoils have very little parasitic drag compaired to other shapes. Why would you think that a servo tab as less parasitic drag than a sparrow strainer?
Spoken by a novice - let the experts come in on this :-). Jim
Patrick Panzera wrote:
BTW, when I was the Dragonfly newsletter editor, Terry O'Neill submitted
an excellent article on how he did away with his sparrow strainers by
installing anti-servo tabs that are also used as an aerodynamic pitch
trim system. He also talks about balancing the elevators to avoid flutter.
I just uploaded the entire issue.
http://issuu.com/contact.magazine/docs/dragonfly_newsletter_97
And if I uploaded it properly, it should download to a printable PDF.
Pat
On Thu, Sep 19, 2013 at 9:10 AM, Patrick Panzera
<editor@... <mailto:editor@...>> wrote:
Adding weight aft of the center of rotation is a sure recipe for
flutter.
Even at low speeds, a little bump could start it.
Look how stable a car's antenna is under normal conditions.
Now imaging a weight at the tip... or note what happens to it when
weight is added from ice.
On Thu, Sep 19, 2013 at 8:15 AM, Jason Nemake <fg13fg@...
<mailto:fg13fg@...>> wrote:
__
Guys,
Are the elevator control surfaces statically balanced on the LS
airfoil, like they are on the GU airfoil? If so, then I would
guess that if you unbalanced the control surface and started
increasing the cg of the control surface aft, to try and cancel
the lifting effect caused by the LS cuspt then heavy springs or
sparrow strainers might not be needed. One could possibly go as
far as weighting the trailing edge. The result would be a
drooped elevator on the ground until reaching flying speeds, and
a positive effect on the stick at low speeds. Maybe even a
combination of springs and aft weight. There of coarse would be
G effects to this idea. Some things to ponder..
Jason Nemake
*From:* "jcrain2@... <mailto:jcrain2@...>"
<jcrain2@... <mailto:jcrain2@...>>
*To:* Q-LIST@... <mailto:Q-LIST@...>
*Sent:* Wednesday, September 18, 2013 8:55 PM
*Subject:* Re: [Q-LIST] Need a Sparrow Strainer alternative
__
Sammy,
Didn't Tom Moore and Bob Malecek have an adjustable flat piece
of aluminum or stainless in place of the upside down airfoil? I
think it had a slight up kicker at the back though. Call them
to see what their ideas were. It might be a bit less drag
perhaps X 2.
Bruce ____---------- Original Message ----------__From: Sam
Hoskins <sam.hoskins@...
<mailto:sam.hoskins@...>>__To: Quickie List
<Q-LIST@...
<mailto:Q-LIST@...>>__Subject: [Q-LIST] Need a
Sparrow Strainer alternative__Date: Wed, 18 Sep 2013 16:14:44
-0500____
The Sparrow Strainers are draggy and slow our planes down.
�There must be an alternative. �Every time a speed specialist
looks at the the sparrow strainers they go "WTF"?
So, let's start at the beginning. �Why are there in the first place?
As I understand it, they are an aerodynamic trim designed to
counteract the high pressure on the bottom of the canard
elevator. �Air wants to push the TE of the elevator up, causing
the plane to dive, so the sparrow strainers help by pushing it
back down.
Is this logic correct?
So, what would be a drag-free alternative? �Well, I suppose one
could increase the spring tension already used for the control
stick. �Why didn't QAC do something like that? �Maybe it would
increase the stick forces. �Just guessing but when they first
flew flew the new �LS-1 airfoil, they probably found they needed
an extraordinary amount of nose up trim. �Followed by going with
the cheapest fix - add sparrow strainers.
Another issue with using internal trim, is you are applying a
constant torque to the joint there the elevator bellcrank slips
into the elevator torque tube. �Maybe it's not a big deal, bit
it's there.
This is all supposition. �Is anyone privy to the real story?
So, all of you aerodynamic tinkerers, what could be a viable way
to eliminate the sparrow strainers?
Thanks for reading.
Sam
__________________________________________________________________*30-second
trick for a flat belly*
This daily 30-second trick BOOSTS your body's #1 fat-burning hormone
<http://thirdpartyoffers.juno.com/TGL3132/523a75e01b0875df585dst01vuc>TheFatBurningHormone.com
<http://thirdpartyoffers.juno.com/TGL3132/523a75e01b0875df585dst01vuc>
____
No virus found in this message.
Checked by AVG - www.avg.com <http://www.avg.com>
Version: 2013.0.3408 / Virus Database: 3222/6678 - Release Date: 09/18/13
--
Porcine Associates LLC
244 O'Connor St.
Menlo Park, CA 94025
USA
+1(650)326-2669 fax +1(650)326-1071
------------------------------------
Quickie Builders Association WEB site
http://www.quickiebuilders.org
Yahoo! Groups Links
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Bruce Crain
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