Date   

Re: Preliminary analysis of aerodynamics of sparrow strainers (or not)

Jay Scheevel
 

Hi Michael,

 

Thanks for the additional comments, data and history on the evolution of the LS-1 etc.

 

As far as what you are requesting, I am using 28% chord as the hinge point on the LS1 elevator. I am attaching the Javafoil coordinates for the LS1 (BL 15 on the Q2), also the multifoil for the same airfoil with the sparrow strainer as the second foil in the file, and my version of the LS1, with the redesign limited to only the bottom profile of the current LS1 elevator.

 

I am using 1 million as Reynolds number for my models.

 

BTW, I made use of the multifoil capability of Javafoil (XFOIL repackaged in a Java shell, by Martin Hepperle) to do my full aircraft modeling of the Q2xx summarized in the following:

http://n8wq.scheevel.com/documents/All_Text_and_figures_Part1.pdf

http://n8wq.scheevel.com/documents/All_Text_and_figures_Part2.pdf

http://n8wq.scheevel.com/documents/All_Text_and_figures_Part3.pdf

 

Cheers,

Jay

 

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Michael Dunning
Sent: Friday, March 4, 2022 6:05 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Preliminary analysis of aerodynamics of sparrow strainers (or not)

 

Jay,

In typical engineer fashion, I don't get the chance to do this at my day job and got my references confused. Appreciate the patience while I double-checked everything....

The NLF development papers are what mention the hinge moment concern. This is the airfoil Somers tweaked for the Lancair 360. You'll notice the Abstract points squarely at correcting the shortcomings in the GAW-turned-LS series of airfoils:
 
 

Totally agree that a new canard using the R1145MS is the "correct" solution. As Mike Dwyer rightly pointed out, that's not really practical for most of us with built hardware. Personally, at that point I'd rather just start a new design with known design allowables rather than guess at the QAC numbers (Waddelow).  However, I will concede that if you have the fuselage shells the wing and canard are largely segregable.

Can you send me the Reynolds numbers, stock LS coordinates, and hinge location you're using as a baseline? XFOIL will calculate the hinge moments for speculative comparison (i.e. relative, not absolute design values).

Footnote: Selig worked with Somers on the NLF development (1995) and later had Ashok as a grad student (1998+), thus I view the AS504X and later airfoils as the current "gold standard" for EAB airfoil comparisons. The AS504X airfoils have the advantage of published (if primitive) wind tunnel test results as compared to the non-existent ones for the NLF(1)-0115.
--
-MD
#2827 (still thinking about planning on visualizing how to finish building)


Re: Preliminary analysis of aerodynamics of sparrow strainers (or not)

Michael Dunning
 

Jay,

In typical engineer fashion, I don't get the chance to do this at my day job and got my references confused. Appreciate the patience while I double-checked everything....

The NLF development papers are what mention the hinge moment concern. This is the airfoil Somers tweaked for the Lancair 360. You'll notice the Abstract points squarely at correcting the shortcomings in the GAW-turned-LS series of airfoils:
 
 

Totally agree that a new canard using the R1145MS is the "correct" solution. As Mike Dwyer rightly pointed out, that's not really practical for most of us with built hardware. Personally, at that point I'd rather just start a new design with known design allowables rather than guess at the QAC numbers (Waddelow).  However, I will concede that if you have the fuselage shells the wing and canard are largely segregable.

Can you send me the Reynolds numbers, stock LS coordinates, and hinge location you're using as a baseline? XFOIL will calculate the hinge moments for speculative comparison (i.e. relative, not absolute design values).

Footnote: Selig worked with Somers on the NLF development (1995) and later had Ashok as a grad student (1998+), thus I view the AS504X and later airfoils as the current "gold standard" for EAB airfoil comparisons. The AS504X airfoils have the advantage of published (if primitive) wind tunnel test results as compared to the non-existent ones for the NLF(1)-0115.
--
-MD
#2827 (still thinking about planning on visualizing how to finish building)


Re: Preliminary analysis of aerodynamics of sparrow strainers (or not)

Jay Scheevel
 

Thanks David for your long note and discussion points. Much appreciated. I will absorb them and continue my analysis.

 

Michael Dunning, feel free to chime in anytime. I watched that video that you linked on the Wasabi flight testing the Raptor. Seems like Elliot has become wiser and more methodical in recent years. Nice to see their approach and discussions. It is a good watch for anyone looking to do a first flight, regardless of the type.

 

On their way out to GA, the Wasabi guys stopped in Borger TX. I landed there about 3 minutes before Charlie and Rob Johnson landed in the Tri-Pacer a few years ago on our way back from FOD in Enid. I have never seen so many bugs on my flight surfaces. Almost could not see the white paint! It was a good test of the LS1 contamination resistance! Charlie’s plane had by then turned into a spray-plane, in an attempt to subdue the bug population using a fine mist of Phillips XC…That made for an eventful ride home for those guys, but eventually worked out fine for Charlie.

 

Cheers,
Jay

 

_._,_._,_


Re: Preliminary analysis of aerodynamics of sparrow strainers (or not)

David J. Gall
 

Jay,

 

Nice analysis. I’m heartened to see that someone else has independently concluded what I’ve been saying for years: the Roncz R1145MS airfoil is a better choice than the LS-1. The Roncz airfoil also solves other issues such as eliminating sparrow strainers. I think Rutan broke off his involvement with QAC over this very issue.

 

I note that you’ve asserted that the elevator floating angle of the Roncz airfoil would require mounting the canard more nose down by one degree. I believe this is incorrect. The elevator floating angle you found is not intended to be achieved at “high speed cruise” as compared to your first illustration on the LS-1; rather, the elevator floating angle is intended to give a *low* speed cruise so that in the unlikely event of a total mechanical disconnection of the elevator from both the trim system and the control stick the airplane could still be flown to a destination or diversion airport (long-range cruise) yet that trimmed speed would also be slow enough that a semblance of a “high speed landing” without elevator control could be survived on arrival, using only throttle for climb/descent. See Rutan’s CP59; also see the fate of George Mead’s Piper “Pugmobile.”

 

So I would recommend mounting the Roncz canard at the same angle of incidence as the LS-1, not a reduced angle of incidence. In flight, the “down” trim spring should be able to hold the needed nose-down elevator bias to achieve hands-off trim at high speed cruise, and the “up” trim spring should be able to hold the needed nose-up elevator bias for slow flight (but not stall).

 

Besides having significantly lower drag than both the GU and LS-1 airfoils, the Roncz drag is lower still compared to the LS-1 airfoil because of not needing sparrow strainers and also because of not having that crazy negative lift zone in the spanwise lift distribution that is caused by the LS-1’s sparrow strainers.

 

Another benefit of the Roncz airfoil is that it is almost as thick as the GU airfoil (20.5% vs. 21% for the GU). Structurally that makes it almost a direct replacement for the GU canard, not needing the tubular carbon spar but able to be built using glass and a slightly modified GU canard layup schedule (think: Waddelow canard). For a Q1 Quickie or for a Q2 (max. gross weight 1000 lbs.) it could be a direct replacement; for a Q200 the added engine weight (MGW 1100 lbs.) would require additional structure. Of course, with some of these planes currently operating at 1300 lbs., all bets are on a structural redesign using carbon.

 

Finally, Mike’s point about the lower angle of incidence on the canard is actually countered by the elevator deflection stop limits; one would run out of elevator deflection before achieving stall if the canard incidence were set too nose-down. However, it would be prudent to check the maximum CL and the AOA at which that occurs when selecting the canard installation incidence angle. It might be necessary to shorten the canard chord slightly if the new airfoil is a significantly better performer than the one it replaces, in order to prevent a main wing stall. (Trimming the chord is preferable to trimming the span because the resulting surface has a higher aspect ratio that gives it a steeper slope of the lift curve, so it achieves CLmax at a lower AOA than a lower aspect ratio surface would.)

 

Keep up the good work,

 

 

David J. Gall



 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Mike Dwyer
Sent: Sunday, February 27, 2022 4:15 PM
To: main@q-list.groups.io
Subject: Re: [Q-List] Preliminary analysis of aerodynamics of sparrow strainers (or not)

 

With a lower angle of attack on the canard, wouldn't that reduce the margin of having the canard stall prior to the main wing?

I'd still like to see a better sparrow strainer design.  Move it into the airstream and make it operate in a "not stalled" condition so it could be smaller...

Mike Dwyer Q200

Great work Jay!

 

Q200 Website: http://goo.gl/V8IrJF

 

 

On Sun, Feb 27, 2022 at 6:37 PM Jay Scheevel <jay@...> wrote:

Let me preface this with the statement that the current design of sparrow strainers works. You should not deviate from that design. The following is purely theoretical at this point and is not flight proven.

 

Here are my observations so far.

At 2 degress AOA, which is about where the Q2 is at high speed cruise, the standard LS! Airfoil produces a Cl of 0.461 and Cd of 0.0191 as shown below

In order to reverse the effect of the elevator deflecting upward in flight, sparrow strainers are installed. As a result, the span that contains the sparrow strainers ends up with an overall NEGATIVE lift coefficient, Cl of -0.333 and almost double the drag of the clean LS1: a Cd of 0.0317  (shown below). The extreme pressure field of the sparrow strainer, because of its high angle relative to the streamlines, actually kills the lift of the LS1 airfoil over the length of span that is occupied by the sparrow strainer. The result is a negative lift coefficient over that portion of the span. So roughly 1/8 of the total canard span (the portion of the span with the sparrow strainer installed)  is actually providing negative lift at an AOA of 2 degrees, and is creating lots more drag than it would if there was no sparrow strainer present.

 

The catch 22 is that we know the sparrow strainer is necessary for the LS1 profile, as we can demonstrate as follows:

 

If the sparrow strainer is omitted and no stick force is applied (hands off), the elevator portion of the canard will tend to reflex up in flight. But, how much would it reflex up? 

 

Well, it looks like it would reflex up 20 degrees before the pressure field is in equilibrium on top and bottom of the elevator. This would result in the overall “hands off” configuration having a negative Cl = -0.420 over the entire span occupied by the elevator. This would result in a severe “tuck”.

 

If the elevator portion of the LS1 is redesigned so as to not deflect up or down in flight and to be in trail throughout most of the AOA range, then the a result is shown below. This design should acheive a “hands off” Cl of 0.434 (slightly less than the bare LS1 of 0.461) and a Cd is 0.0198, very slightly higher than the bare LS1. No stick force or sparrow strainer would be required for this elevator profile if it performs as modeled, so the draggy and negative lift portion of the span would not be nescessary.

 

But what about a different airfoil, such as the the  Roncz 1145MS airfoil? R1145MS would result in the same Cl as the modified-elevator LS airfoil, but at a lower Cd of 0.01393. As shown below.

However, the Ronz airfoil, if fitted with an articulated elevator in the Q2 configuration, would tend to see the elevator deflect downward before achieving aerodynamic balance with no springs, stick force or sparrow strainer applied. Equilibrium would be achieved with the elevator deflected downward approximately 2 degrees as shown below. This deflection results in a higher Cl and would require that the overall airfoil be installed 1 degree nose down to the LS1 to perform aerodynamically similar to the LS1 equipped Q2. Doing so, would  yield a Cl of 0.458 and Cd of 0.01372 at an AOA of 2 degrees.

 

So we would mount the Roncz airfoil 1 degree lower angle. If we were to do this on a Q2, then the Cl would be similar to the LS1 airfoil, but the drag would be about 30% lower than the LS1: Cd 0.014 at and AOA of 2 degrees.

 

Note that none of these models include the effect of a turbulent stall bubble on the trailing edge of the elevator, so the numbers would be slightly different on a flying aircraft.

 

In summary, we see that the Roncz 1145MS airfoil would probably have been a better choice than the LS1 for a Q2, but it may not have been available at the time the decision of QAC was to go with the LS1. We can also see that the sparrow strainer solves the problem of preventing the LS1 elevator floating up in flight, but at a great drag cost and a reduction in overall canard lift over the span to which the sparrow strainer is applied (roughly 1/8 of the total span of the canard) with the 11.5” sparrow strainer, higher if using the 17.5’ sparrow strainer).

 

As shown above, it is possible to design a more benign elevator shape for the existing LS1 canard that will solve the problem of the elevator floating up in flight without the need for a sparrow strainer, but this solution is not as efficient with respect to drag as would be use of an entirely new airfoil as was done by John Roncz for the Long EZ.

 

This is my analysis so far. I will continue to work on this as time permits.

 

Cheers,

Jay


Re: Sparrow strainer stall conundrum

Ben Wilson
 

Hi Jay/David/Vern:

As I said before: the sparrow strainer conundrum is pure gold.

For retired aero/structural engineer types it is great fun.

Ben

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Frankenbird Vern
Sent: Wednesday, March 2, 2022 11:34 AM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

It's not in the weeds for me, Jay  

 

We could be looking at a balancing act.


From: main@Q-List.groups.io <main@Q-List.groups.io> on behalf of Jay Scheevel <jay@...>
Sent: Wednesday, March 2, 2022 11:51 AM
To: main@Q-List.groups.io <main@Q-List.groups.io>
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Hi David,

 

Glad to hear you have your ears on the Q-list again. My redesigned LS1 elevator behaves nicely in the simple modeling software that I use (meaning it will remain in neutral trail at a minimum cruise speed and still produce necessary lift for a control free emergency).

 

Had a question for you: Since  I have designed it to have essentially no delta-pressure top and bottom, will this make it more prone to flutter?  Should I shoot for positive balanced pressure top and bottom in order to stabilize it?

 

You can answer me offline if this is getting too far in the weeds for the rest of the group.

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of David J. Gall
Sent: Wednesday, March 2, 2022 10:34 AM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Just playing catch up on the last two weeks of frantic Q-LIST activity….

OMG, Michael, the “Mad Rocket Scientist” (Drew) is a nice enough guy but he’s wrong fully ninety percent of the time when it comes to his discussions of aircraft stability and control. Even the animated graphic you point to is wrong.

<Rocket Scientist> != <Aeronautical Engineer>

 

Caveat Emptor.

 

 

David J. Gall

 

PS: When encountering any prototype aircraft bearing the moniker “Raptor,” run away! Run away!! LOL

 

 

 

Deregistered Aircraft 1 of 1

Aircraft Description

Serial Number

H-5157-001

Certificate Issue Date

06/26/1996

Manufacturer Name

AURIGEMA ANDREW N

Mode S Code (base 8 / oct)

53275133

Model

DRAGON FLY MARK II

Mode S Code (base 16 / hex)

AD7A5B

Year Manufacturer

2001

Cancel Date

01/30/2009

Reason For Cancellation

Cancelled

Export To

None

Type Registration

Individual

 

 

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Michael Dunning
Sent: Wednesday, February 23, 2022 1:57 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Anthony, I believe what you are talking about is an elevator slot, similar to a slotted flap? Jay's proposed elevator design is plain-flap style, unlike the R1145MS which does make use of an elevator slot for improved performance (see animation about halfway down this page).
--
-MD
#2827 (still thinking about planning on visualizing how to finish building)


Re: Sparrow strainer stall conundrum

Michael Dunning
 

HAHA! Thanks, David. Browsing QDF I kept wondering if it was "that" Raptor... *snort*
I avoided that "experiment" with a 20 foot pole up until watching Seguin's YT report...

Since Jay is getting serious, I need to go dig up my papers from Ashok on the subject. Either way, I don't have MSES to analyze multi-element airfoils. Was quite surprised to see it supported in Jay's recent work with JavaFoil.

--
-MD
#2827 (still thinking about planning on visualizing how to finish building)


Re: Sparrow strainer stall conundrum

Jay Scheevel
 

Great hints, David. Thanks.

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of David J. Gall
Sent: Wednesday, March 2, 2022 12:05 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Hi Jay,

 

I’m glad you asked; I was concerned about the aft shape of your airfoil approaching the trailing edge. It appears that the last ~15% of your shape is convex. That’s a big no-no aft of a hinge line. What you want in this area is a straight-flat or, better, slightly concave shape on both top and bottom. John Roncz made his Long-EZ elevator straight-flat on the lower surface (partly for ease of manufacturing – smart guy!) and made the upper surface straight-flat almost all the way to the trailing edge followed by just a slight concave “reflex” at the very end to establish the needed aerodynamics for the appropriate elevator floating angle.

Also, don’t put a radius on the extreme trailing edge, either. Hold the sanding block vertical and establish two sharp ~88° angles to make a “squared off” trailing edge that will shed the top and bottom boundary layers cleanly at the sharp corners.

 

Pay close attention to the handwritten notes in the image below.

 

 

David J. Gall

 

 

 

 

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Jay Scheevel
Sent: Wednesday, March 2, 2022 9:52 AM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Hi David,

 

Glad to hear you have your ears on the Q-list again. My redesigned LS1 elevator behaves nicely in the simple modeling software that I use (meaning it will remain in neutral trail at a minimum cruise speed and still produce necessary lift for a control free emergency).

 

Had a question for you: Since  I have designed it to have essentially no delta-pressure top and bottom, will this make it more prone to flutter?  Should I shoot for positive balanced pressure top and bottom in order to stabilize it?

 

You can answer me offline if this is getting too far in the weeds for the rest of the group.

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of David J. Gall
Sent: Wednesday, March 2, 2022 10:34 AM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Just playing catch up on the last two weeks of frantic Q-LIST activity….

OMG, Michael, the “Mad Rocket Scientist” (Drew) is a nice enough guy but he’s wrong fully ninety percent of the time when it comes to his discussions of aircraft stability and control. Even the animated graphic you point to is wrong.

<Rocket Scientist> != <Aeronautical Engineer>

 

Caveat Emptor.

 

 

David J. Gall

 

PS: When encountering any prototype aircraft bearing the moniker “Raptor,” run away! Run away!! LOL

 

 

 

Deregistered Aircraft 1 of 1

Aircraft Description

Serial Number

H-5157-001

Certificate Issue Date

06/26/1996

Manufacturer Name

AURIGEMA ANDREW N

Mode S Code (base 8 / oct)

53275133

Model

DRAGON FLY MARK II

Mode S Code (base 16 / hex)

AD7A5B

Year Manufacturer

2001

Cancel Date

01/30/2009

Reason For Cancellation

Cancelled

Export To

None

Type Registration

Individual

 

 

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Michael Dunning
Sent: Wednesday, February 23, 2022 1:57 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Anthony, I believe what you are talking about is an elevator slot, similar to a slotted flap? Jay's proposed elevator design is plain-flap style, unlike the R1145MS which does make use of an elevator slot for improved performance (see animation about halfway down this page).
--
-MD
#2827 (still thinking about planning on visualizing how to finish building)


Re: Sparrow strainer stall conundrum

David J. Gall
 

Hi Jay,

 

I’m glad you asked; I was concerned about the aft shape of your airfoil approaching the trailing edge. It appears that the last ~15% of your shape is convex. That’s a big no-no aft of a hinge line. What you want in this area is a straight-flat or, better, slightly concave shape on both top and bottom. John Roncz made his Long-EZ elevator straight-flat on the lower surface (partly for ease of manufacturing – smart guy!) and made the upper surface straight-flat almost all the way to the trailing edge followed by just a slight concave “reflex” at the very end to establish the needed aerodynamics for the appropriate elevator floating angle.

Also, don’t put a radius on the extreme trailing edge, either. Hold the sanding block vertical and establish two sharp ~88° angles to make a “squared off” trailing edge that will shed the top and bottom boundary layers cleanly at the sharp corners.

 

Pay close attention to the handwritten notes in the image below.

 

 

David J. Gall

 

 

 

 

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Jay Scheevel
Sent: Wednesday, March 2, 2022 9:52 AM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Hi David,

 

Glad to hear you have your ears on the Q-list again. My redesigned LS1 elevator behaves nicely in the simple modeling software that I use (meaning it will remain in neutral trail at a minimum cruise speed and still produce necessary lift for a control free emergency).

 

Had a question for you: Since  I have designed it to have essentially no delta-pressure top and bottom, will this make it more prone to flutter?  Should I shoot for positive balanced pressure top and bottom in order to stabilize it?

 

You can answer me offline if this is getting too far in the weeds for the rest of the group.

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of David J. Gall
Sent: Wednesday, March 2, 2022 10:34 AM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Just playing catch up on the last two weeks of frantic Q-LIST activity….

OMG, Michael, the “Mad Rocket Scientist” (Drew) is a nice enough guy but he’s wrong fully ninety percent of the time when it comes to his discussions of aircraft stability and control. Even the animated graphic you point to is wrong.

<Rocket Scientist> != <Aeronautical Engineer>

 

Caveat Emptor.

 

 

David J. Gall

 

PS: When encountering any prototype aircraft bearing the moniker “Raptor,” run away! Run away!! LOL

 

 

 

Deregistered Aircraft 1 of 1

Aircraft Description

Serial Number

H-5157-001

Certificate Issue Date

06/26/1996

Manufacturer Name

AURIGEMA ANDREW N

Mode S Code (base 8 / oct)

53275133

Model

DRAGON FLY MARK II

Mode S Code (base 16 / hex)

AD7A5B

Year Manufacturer

2001

Cancel Date

01/30/2009

Reason For Cancellation

Cancelled

Export To

None

Type Registration

Individual

 

 

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Michael Dunning
Sent: Wednesday, February 23, 2022 1:57 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Anthony, I believe what you are talking about is an elevator slot, similar to a slotted flap? Jay's proposed elevator design is plain-flap style, unlike the R1145MS which does make use of an elevator slot for improved performance (see animation about halfway down this page).
--
-MD
#2827 (still thinking about planning on visualizing how to finish building)


Re: Sparrow strainer stall conundrum

Frankenbird Vern
 

It's not in the weeds for me, Jay  

We could be looking at a balancing act.


From: main@Q-List.groups.io <main@Q-List.groups.io> on behalf of Jay Scheevel <jay@...>
Sent: Wednesday, March 2, 2022 11:51 AM
To: main@Q-List.groups.io <main@Q-List.groups.io>
Subject: Re: [Q-List] Sparrow strainer stall conundrum
 

Hi David,

 

Glad to hear you have your ears on the Q-list again. My redesigned LS1 elevator behaves nicely in the simple modeling software that I use (meaning it will remain in neutral trail at a minimum cruise speed and still produce necessary lift for a control free emergency).

 

Had a question for you: Since  I have designed it to have essentially no delta-pressure top and bottom, will this make it more prone to flutter?  Should I shoot for positive balanced pressure top and bottom in order to stabilize it?

 

You can answer me offline if this is getting too far in the weeds for the rest of the group.

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of David J. Gall
Sent: Wednesday, March 2, 2022 10:34 AM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Just playing catch up on the last two weeks of frantic Q-LIST activity….

OMG, Michael, the “Mad Rocket Scientist” (Drew) is a nice enough guy but he’s wrong fully ninety percent of the time when it comes to his discussions of aircraft stability and control. Even the animated graphic you point to is wrong.

<Rocket Scientist> != <Aeronautical Engineer>

 

Caveat Emptor.

 

 

David J. Gall

 

PS: When encountering any prototype aircraft bearing the moniker “Raptor,” run away! Run away!! LOL

 

 

 

Deregistered Aircraft 1 of 1

Aircraft Description

Serial Number

H-5157-001

Certificate Issue Date

06/26/1996

Manufacturer Name

AURIGEMA ANDREW N

Mode S Code (base 8 / oct)

53275133

Model

DRAGON FLY MARK II

Mode S Code (base 16 / hex)

AD7A5B

Year Manufacturer

2001

Cancel Date

01/30/2009

Reason For Cancellation

Cancelled

Export To

None

Type Registration

Individual

 

 

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Michael Dunning
Sent: Wednesday, February 23, 2022 1:57 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Anthony, I believe what you are talking about is an elevator slot, similar to a slotted flap? Jay's proposed elevator design is plain-flap style, unlike the R1145MS which does make use of an elevator slot for improved performance (see animation about halfway down this page).
--
-MD
#2827 (still thinking about planning on visualizing how to finish building)


Re: Sparrow strainer stall conundrum

David J. Gall
 

Brian,

 

Can you make a copy or scan of those instructions for the archives? The LS(1) canard plans that I have show different dimensions.

 

Thank you,

 

 

David J. Gall

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Brian Larick
Sent: Friday, February 25, 2022 6:30 PM
To: main@q-list.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

With the talk of location and size.  I have early ls-1 instructions including sparrow strainer dimensions of 17 inch size and the 24” from inboard edge of elevator location these are in an envelope post marked Oct 3 1983.  Rounded the sizes since I already forgot the fractions.

Brian



On Feb 24, 2022, at 09:54, Hot Wings via groups.io <bd5er@...> wrote:

Gurney flaps have been mentioned here before when this 'problem' came up.  Has anyone actually tried them?


Re: Sparrow strainer stall conundrum

Jay Scheevel
 

Hi David,

 

Glad to hear you have your ears on the Q-list again. My redesigned LS1 elevator behaves nicely in the simple modeling software that I use (meaning it will remain in neutral trail at a minimum cruise speed and still produce necessary lift for a control free emergency).

 

Had a question for you: Since  I have designed it to have essentially no delta-pressure top and bottom, will this make it more prone to flutter?  Should I shoot for positive balanced pressure top and bottom in order to stabilize it?

 

You can answer me offline if this is getting too far in the weeds for the rest of the group.

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of David J. Gall
Sent: Wednesday, March 2, 2022 10:34 AM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Just playing catch up on the last two weeks of frantic Q-LIST activity….

OMG, Michael, the “Mad Rocket Scientist” (Drew) is a nice enough guy but he’s wrong fully ninety percent of the time when it comes to his discussions of aircraft stability and control. Even the animated graphic you point to is wrong.

<Rocket Scientist> != <Aeronautical Engineer>

 

Caveat Emptor.

 

 

David J. Gall

 

PS: When encountering any prototype aircraft bearing the moniker “Raptor,” run away! Run away!! LOL

 

 

 

Deregistered Aircraft 1 of 1

Aircraft Description

Serial Number

H-5157-001

Certificate Issue Date

06/26/1996

Manufacturer Name

AURIGEMA ANDREW N

Mode S Code (base 8 / oct)

53275133

Model

DRAGON FLY MARK II

Mode S Code (base 16 / hex)

AD7A5B

Year Manufacturer

2001

Cancel Date

01/30/2009

Reason For Cancellation

Cancelled

Export To

None

Type Registration

Individual

 

 

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Michael Dunning
Sent: Wednesday, February 23, 2022 1:57 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Anthony, I believe what you are talking about is an elevator slot, similar to a slotted flap? Jay's proposed elevator design is plain-flap style, unlike the R1145MS which does make use of an elevator slot for improved performance (see animation about halfway down this page).
--
-MD
#2827 (still thinking about planning on visualizing how to finish building)


Re: Sparrow strainer stall conundrum

David J. Gall
 

Just playing catch up on the last two weeks of frantic Q-LIST activity….

OMG, Michael, the “Mad Rocket Scientist” (Drew) is a nice enough guy but he’s wrong fully ninety percent of the time when it comes to his discussions of aircraft stability and control. Even the animated graphic you point to is wrong.

<Rocket Scientist> != <Aeronautical Engineer>

 

Caveat Emptor.

 

 

David J. Gall

 

PS: When encountering any prototype aircraft bearing the moniker “Raptor,” run away! Run away!! LOL

 

 

Deregistered Aircraft 1 of 1

Aircraft Description

Serial Number

H-5157-001

Certificate Issue Date

06/26/1996

Manufacturer Name

AURIGEMA ANDREW N

Mode S Code (base 8 / oct)

53275133

Model

DRAGON FLY MARK II

Mode S Code (base 16 / hex)

AD7A5B

Year Manufacturer

2001

Cancel Date

01/30/2009

Reason For Cancellation

Cancelled

Export To

None

Type Registration

Individual

 

 

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Michael Dunning
Sent: Wednesday, February 23, 2022 1:57 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Sparrow strainer stall conundrum

 

Anthony, I believe what you are talking about is an elevator slot, similar to a slotted flap? Jay's proposed elevator design is plain-flap style, unlike the R1145MS which does make use of an elevator slot for improved performance (see animation about halfway down this page).
--
-MD
#2827 (still thinking about planning on visualizing how to finish building)


Re: Turn radius

Jay Scheevel
 

Hi Jon,

 

Don’t intend to put myself in a position where I would need to use such a beast…in my Q, anyway, I will stick with 4000’ AGL minimum radius turns, but I’m game if you want… and there is something I could benefit from.

 

I see you are now more specific about where you are flying, in your sign off.

 

Cheers,

Jay

 

From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Jon Finley
Sent: Tuesday, March 1, 2022 12:59 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Turn radius

 

When your ready Jay, let's talk about minimum radius canyon turns. 😉

Jon Finley
Flying an RV-4 - Truth or Consequences, NM


Re: Turn radius

Jon Finley
 

When your ready Jay, let's talk about minimum radius canyon turns. 😉

Jon Finley
Flying an RV-4 - Truth or Consequences, NM


Re: Preliminary analysis of aerodynamics of sparrow strainers (or not)

Mike Dwyer
 

Thanks for the explanation Jay.  I'm pulling like 20 lbs of back pressure just prior to stall, but at the stall the force drops to zero.  That made me think that the canard is stalling.  Your explaination makes sense!  
Fly Safe,
Mike Dwyer Q200

On Sun, Feb 27, 2022, 8:26 PM Jay Scheevel <jay@...> wrote:
Hi Mike,

Here’s the deal on wing mounting angles. Unlike the current dogma about the canard stalling first, the canard in the Q configuration never really achieves a full stall. The full stall angle is something like 13-14 degrees  AOA for the LS1 at the wing root. What happens before it gets to this angle is that the main wing “overpowers” the canard wrt pitch moment and forces the angle of attack lower. This is the pitch bunk oscillation.

This is why the pitch buck is a sort of nodding action instead of something more violent. 

Why is this the case? In intermediate angles of attack the angle versus lift curve is linear, so the ratio of lift contribution between canard and MW is constant for a given elevator deflection over a range of AOA’s. At higher angles of attack and higher elevator deflection, the slope of the lift curve for the canard decreases progressively while the MW lift curve remains linear. The Q is set up so that the MW is still in the linear portion of the lift curve when the canard enters the reduced slope portion (at about 8-9 degrees). At this angle the canard is still not close to stall.  Because the MW is picking up lift vs angle at a higher rate, the MW starts to win the pitch moment battle and it forces a lower angle of attack on the entire plane.  This is the pitch buck. Nothing is fully stalled.  If the canard were fully stalled, it would feel like a true stall and like it wants to depart into a spin.

I mounted my MW at a lower angle relative to the canard so my canard gets closer to stall and is more like 10-11 degrees at pitch buck. My pitch buck is more “exciting”, but this is NOT because the MW is closer to stall, but because the canard is closer to stall.  

So the design of the relative angle of the canard in the tandem wing configuration is intended to match the lift ratios in a way to make sure the canard reaches the non-linear portion of the lift curve first.

Accelerated stalls are another animal and are to be avoided in the Q.

Cheers,
Jay


On Feb 27, 2022, at 5:15 PM, Mike Dwyer <q200pilot@...> wrote:


With a lower angle of attack on the canard, wouldn't that reduce the margin of having the canard stall prior to the main wing?
I'd still like to see a better sparrow strainer design.  Move it into the airstream and make it operate in a "not stalled" condition so it could be smaller...
Mike Dwyer Q200
Great work Jay!

Q200 Website: http://goo.gl/V8IrJF


On Sun, Feb 27, 2022 at 6:37 PM Jay Scheevel <jay@...> wrote:

Let me preface this with the statement that the current design of sparrow strainers works. You should not deviate from that design. The following is purely theoretical at this point and is not flight proven.

 

Here are my observations so far.

At 2 degress AOA, which is about where the Q2 is at high speed cruise, the standard LS! Airfoil produces a Cl of 0.461 and Cd of 0.0191 as shown below

In order to reverse the effect of the elevator deflecting upward in flight, sparrow strainers are installed. As a result, the span that contains the sparrow strainers ends up with an overall NEGATIVE lift coefficient, Cl of -0.333 and almost double the drag of the clean LS1: a Cd of 0.0317  (shown below). The extreme pressure field of the sparrow strainer, because of its high angle relative to the streamlines, actually kills the lift of the LS1 airfoil over the length of span that is occupied by the sparrow strainer. The result is a negative lift coefficient over that portion of the span. So roughly 1/8 of the total canard span (the portion of the span with the sparrow strainer installed)  is actually providing negative lift at an AOA of 2 degrees, and is creating lots more drag than it would if there was no sparrow strainer present.

 

The catch 22 is that we know the sparrow strainer is necessary for the LS1 profile, as we can demonstrate as follows:

 

If the sparrow strainer is omitted and no stick force is applied (hands off), the elevator portion of the canard will tend to reflex up in flight. But, how much would it reflex up? 

 

Well, it looks like it would reflex up 20 degrees before the pressure field is in equilibrium on top and bottom of the elevator. This would result in the overall “hands off” configuration having a negative Cl = -0.420 over the entire span occupied by the elevator. This would result in a severe “tuck”.

 

If the elevator portion of the LS1 is redesigned so as to not deflect up or down in flight and to be in trail throughout most of the AOA range, then the a result is shown below. This design should acheive a “hands off” Cl of 0.434 (slightly less than the bare LS1 of 0.461) and a Cd is 0.0198, very slightly higher than the bare LS1. No stick force or sparrow strainer would be required for this elevator profile if it performs as modeled, so the draggy and negative lift portion of the span would not be nescessary.

 

But what about a different airfoil, such as the the  Roncz 1145MS airfoil? R1145MS would result in the same Cl as the modified-elevator LS airfoil, but at a lower Cd of 0.01393. As shown below.

However, the Ronz airfoil, if fitted with an articulated elevator in the Q2 configuration, would tend to see the elevator deflect downward before achieving aerodynamic balance with no springs, stick force or sparrow strainer applied. Equilibrium would be achieved with the elevator deflected downward approximately 2 degrees as shown below. This deflection results in a higher Cl and would require that the overall airfoil be installed 1 degree nose down to the LS1 to perform aerodynamically similar to the LS1 equipped Q2. Doing so, would  yield a Cl of 0.458 and Cd of 0.01372 at an AOA of 2 degrees.

 

So we would mount the Roncz airfoil 1 degree lower angle. If we were to do this on a Q2, then the Cl would be similar to the LS1 airfoil, but the drag would be about 30% lower than the LS1: Cd 0.014 at and AOA of 2 degrees.

 

Note that none of these models include the effect of a turbulent stall bubble on the trailing edge of the elevator, so the numbers would be slightly different on a flying aircraft.

 

In summary, we see that the Roncz 1145MS airfoil would probably have been a better choice than the LS1 for a Q2, but it may not have been available at the time the decision of QAC was to go with the LS1. We can also see that the sparrow strainer solves the problem of preventing the LS1 elevator floating up in flight, but at a great drag cost and a reduction in overall canard lift over the span to which the sparrow strainer is applied (roughly 1/8 of the total span of the canard) with the 11.5” sparrow strainer, higher if using the 17.5’ sparrow strainer).

 

As shown above, it is possible to design a more benign elevator shape for the existing LS1 canard that will solve the problem of the elevator floating up in flight without the need for a sparrow strainer, but this solution is not as efficient with respect to drag as would be use of an entirely new airfoil as was done by John Roncz for the Long EZ.

 

This is my analysis so far. I will continue to work on this as time permits.

 

Cheers,

Jay


Re: Flight report

Jay Scheevel
 

Looks like a beautiful morning there Charlie.

Cheers,
Jay 


On Feb 28, 2022, at 2:33 AM, One Sky Dog via groups.io <Oneskydog@...> wrote:

 Nice Kevin,

Not my Dragonfly but I got my first camping air show in the log book this year!


Inline image
It’s warming up nicely,
Charlie





On Sunday, February 27, 2022, 5:57 PM, Kevin Boddicker <trumanst@...> wrote:

Well. After all of my pissing and moaning for weeks now, I finally got my first flight of the year (in my Q) completed.
Nice day, compared to what we have been experiencing, light and variable winds, clear skies, 33°F on the ramp.
I had not flown my Q since early October. Followed by my condition inspection completed in November.

With that said I decided after run up, I would make a couple of fast taxi’s to see WOT and evaluate the power, smoothness of the engine, carb heat at WOT.
All was good. TO on 29 was smooth. Climb at 110MPH indicated yielded about 1000’ FPM climb.
Left the pattern, just flew around and enjoyed the recreation side of homebuilding!
1.4 hours later I was on the ground with a re-usable plane.

On base to final, a Piper Arrow decided that I needed some excitement, and said “Im going to get out of your way and depart.
I said “don’t” but then said I would go around. He said “you have plenty of room” as I was turning on final, and he was just getting a roll started. Went around in a right pattern, so I would not overfly him. Made a big circle and re-entered DW. Landing was acceptable.
No broken or missing parts.

The experience beats the hell out of whining about not flying!

As Jay said earlier, Get um dun. That too beats the hell out of building!




Kevin Boddicker
TriQ 200 N7868B    571hrs
Luana, IA.









Re: Flight report

One Sky Dog
 

Nice Kevin,

Not my Dragonfly but I got my first camping air show in the log book this year!


Inline image
It’s warming up nicely,
Charlie





On Sunday, February 27, 2022, 5:57 PM, Kevin Boddicker <trumanst@...> wrote:

Well. After all of my pissing and moaning for weeks now, I finally got my first flight of the year (in my Q) completed.
Nice day, compared to what we have been experiencing, light and variable winds, clear skies, 33°F on the ramp.
I had not flown my Q since early October. Followed by my condition inspection completed in November.

With that said I decided after run up, I would make a couple of fast taxi’s to see WOT and evaluate the power, smoothness of the engine, carb heat at WOT.
All was good. TO on 29 was smooth. Climb at 110MPH indicated yielded about 1000’ FPM climb.
Left the pattern, just flew around and enjoyed the recreation side of homebuilding!
1.4 hours later I was on the ground with a re-usable plane.

On base to final, a Piper Arrow decided that I needed some excitement, and said “Im going to get out of your way and depart.
I said “don’t” but then said I would go around. He said “you have plenty of room” as I was turning on final, and he was just getting a roll started. Went around in a right pattern, so I would not overfly him. Made a big circle and re-entered DW. Landing was acceptable.
No broken or missing parts.

The experience beats the hell out of whining about not flying!

As Jay said earlier, Get um dun. That too beats the hell out of building!




Kevin Boddicker
TriQ 200 N7868B    571hrs
Luana, IA.









Re: Flight report

Bruce Crain
 

Atta boy Kevie!!  Glad you could get er out and about!
Bruce


---------- Original Message ----------
From: "Kevin  Boddicker" <trumanst@...>
To: Q List <Q-List@groups.io>
Subject: [Q-List] Flight report
Date: Sun, 27 Feb 2022 18:57:14 -0600

Well. After all of my pissing and moaning for weeks now, I finally got my first flight of the year (in my Q) completed.
Nice day, compared to what we have been experiencing, light and variable winds, clear skies, 33°F on the ramp.
I had not flown my Q since early October. Followed by my condition inspection completed in November.

With that said I decided after run up, I would make a couple of fast taxi’s to see WOT and evaluate the power, smoothness of the engine, carb heat at WOT.
All was good. TO on 29 was smooth. Climb at 110MPH indicated yielded about 1000’ FPM climb.
Left the pattern, just flew around and enjoyed the recreation side of homebuilding!
1.4 hours later I was on the ground with a re-usable plane.

On base to final, a Piper Arrow decided that I needed some excitement, and said “Im going to get out of your way and depart.
I said “don’t” but then said I would go around. He said “you have plenty of room” as I was turning on final, and he was just getting a roll started. Went around in a right pattern, so I would not overfly him. Made a big circle and re-entered DW. Landing was acceptable.
No broken or missing parts.

The experience beats the hell out of whining about not flying!

As Jay said earlier, Get um dun. That too beats the hell out of building!




Kevin Boddicker
TriQ 200 N7868B    571hrs
Luana, IA.






Re: Flight report

Jay Scheevel
 

I like that Kevin…”no broken or missing parts” Glad you got your first in before the en of February.

Cheers,
Jay 


On Feb 27, 2022, at 6:08 PM, Frankenbird Vern <smeshno1@...> wrote:


 It is good news you didn't get stuck by an Arrow!! How the hell does he know "you have enough room?"  Maybe he'd say the same thing if you were in the Concorde.  Probably waits at a corner until a Semi is 20 feet away at 60mph and then pulls in front of the truck.      

From: main@Q-List.groups.io <main@Q-List.groups.io> on behalf of Kevin Boddicker <trumanst@...>
Sent: Sunday, February 27, 2022 6:57 PM
To: Q List <Q-List@groups.io>
Subject: [Q-List] Flight report
 
Well. After all of my pissing and moaning for weeks now, I finally got my first flight of the year (in my Q) completed.
Nice day, compared to what we have been experiencing, light and variable winds, clear skies, 33°F on the ramp.
I had not flown my Q since early October. Followed by my condition inspection completed in November.

With that said I decided after run up, I would make a couple of fast taxi’s to see WOT and evaluate the power, smoothness of the engine, carb heat at WOT.
All was good. TO on 29 was smooth. Climb at 110MPH indicated yielded about 1000’ FPM climb.
Left the pattern, just flew around and enjoyed the recreation side of homebuilding!
1.4 hours later I was on the ground with a re-usable plane.

On base to final, a Piper Arrow decided that I needed some excitement, and said “Im going to get out of your way and depart.
I said “don’t” but then said I would go around. He said “you have plenty of room” as I was turning on final, and he was just getting a roll started. Went around in a right pattern, so I would not overfly him. Made a big circle and re-entered DW. Landing was acceptable.
No broken or missing parts.

The experience beats the hell out of whining about not flying!

As Jay said earlier, Get um dun. That too beats the hell out of building!




Kevin Boddicker
TriQ 200 N7868B    571hrs
Luana, IA.









Re: Preliminary analysis of aerodynamics of sparrow strainers (or not)

Jay Scheevel
 

Hi Mike,

Here’s the deal on wing mounting angles. Unlike the current dogma about the canard stalling first, the canard in the Q configuration never really achieves a full stall. The full stall angle is something like 13-14 degrees  AOA for the LS1 at the wing root. What happens before it gets to this angle is that the main wing “overpowers” the canard wrt pitch moment and forces the angle of attack lower. This is the pitch bunk oscillation.

This is why the pitch buck is a sort of nodding action instead of something more violent. 

Why is this the case? In intermediate angles of attack the angle versus lift curve is linear, so the ratio of lift contribution between canard and MW is constant for a given elevator deflection over a range of AOA’s. At higher angles of attack and higher elevator deflection, the slope of the lift curve for the canard decreases progressively while the MW lift curve remains linear. The Q is set up so that the MW is still in the linear portion of the lift curve when the canard enters the reduced slope portion (at about 8-9 degrees). At this angle the canard is still not close to stall.  Because the MW is picking up lift vs angle at a higher rate, the MW starts to win the pitch moment battle and it forces a lower angle of attack on the entire plane.  This is the pitch buck. Nothing is fully stalled.  If the canard were fully stalled, it would feel like a true stall and like it wants to depart into a spin.

I mounted my MW at a lower angle relative to the canard so my canard gets closer to stall and is more like 10-11 degrees at pitch buck. My pitch buck is more “exciting”, but this is NOT because the MW is closer to stall, but because the canard is closer to stall.  

So the design of the relative angle of the canard in the tandem wing configuration is intended to match the lift ratios in a way to make sure the canard reaches the non-linear portion of the lift curve first.

Accelerated stalls are another animal and are to be avoided in the Q.

Cheers,
Jay


On Feb 27, 2022, at 5:15 PM, Mike Dwyer <q200pilot@...> wrote:


With a lower angle of attack on the canard, wouldn't that reduce the margin of having the canard stall prior to the main wing?
I'd still like to see a better sparrow strainer design.  Move it into the airstream and make it operate in a "not stalled" condition so it could be smaller...
Mike Dwyer Q200
Great work Jay!

Q200 Website: http://goo.gl/V8IrJF


On Sun, Feb 27, 2022 at 6:37 PM Jay Scheevel <jay@...> wrote:

Let me preface this with the statement that the current design of sparrow strainers works. You should not deviate from that design. The following is purely theoretical at this point and is not flight proven.

 

Here are my observations so far.

At 2 degress AOA, which is about where the Q2 is at high speed cruise, the standard LS! Airfoil produces a Cl of 0.461 and Cd of 0.0191 as shown below

In order to reverse the effect of the elevator deflecting upward in flight, sparrow strainers are installed. As a result, the span that contains the sparrow strainers ends up with an overall NEGATIVE lift coefficient, Cl of -0.333 and almost double the drag of the clean LS1: a Cd of 0.0317  (shown below). The extreme pressure field of the sparrow strainer, because of its high angle relative to the streamlines, actually kills the lift of the LS1 airfoil over the length of span that is occupied by the sparrow strainer. The result is a negative lift coefficient over that portion of the span. So roughly 1/8 of the total canard span (the portion of the span with the sparrow strainer installed)  is actually providing negative lift at an AOA of 2 degrees, and is creating lots more drag than it would if there was no sparrow strainer present.

 

The catch 22 is that we know the sparrow strainer is necessary for the LS1 profile, as we can demonstrate as follows:

 

If the sparrow strainer is omitted and no stick force is applied (hands off), the elevator portion of the canard will tend to reflex up in flight. But, how much would it reflex up? 

 

Well, it looks like it would reflex up 20 degrees before the pressure field is in equilibrium on top and bottom of the elevator. This would result in the overall “hands off” configuration having a negative Cl = -0.420 over the entire span occupied by the elevator. This would result in a severe “tuck”.

 

If the elevator portion of the LS1 is redesigned so as to not deflect up or down in flight and to be in trail throughout most of the AOA range, then the a result is shown below. This design should acheive a “hands off” Cl of 0.434 (slightly less than the bare LS1 of 0.461) and a Cd is 0.0198, very slightly higher than the bare LS1. No stick force or sparrow strainer would be required for this elevator profile if it performs as modeled, so the draggy and negative lift portion of the span would not be nescessary.

 

But what about a different airfoil, such as the the  Roncz 1145MS airfoil? R1145MS would result in the same Cl as the modified-elevator LS airfoil, but at a lower Cd of 0.01393. As shown below.

However, the Ronz airfoil, if fitted with an articulated elevator in the Q2 configuration, would tend to see the elevator deflect downward before achieving aerodynamic balance with no springs, stick force or sparrow strainer applied. Equilibrium would be achieved with the elevator deflected downward approximately 2 degrees as shown below. This deflection results in a higher Cl and would require that the overall airfoil be installed 1 degree nose down to the LS1 to perform aerodynamically similar to the LS1 equipped Q2. Doing so, would  yield a Cl of 0.458 and Cd of 0.01372 at an AOA of 2 degrees.

 

So we would mount the Roncz airfoil 1 degree lower angle. If we were to do this on a Q2, then the Cl would be similar to the LS1 airfoil, but the drag would be about 30% lower than the LS1: Cd 0.014 at and AOA of 2 degrees.

 

Note that none of these models include the effect of a turbulent stall bubble on the trailing edge of the elevator, so the numbers would be slightly different on a flying aircraft.

 

In summary, we see that the Roncz 1145MS airfoil would probably have been a better choice than the LS1 for a Q2, but it may not have been available at the time the decision of QAC was to go with the LS1. We can also see that the sparrow strainer solves the problem of preventing the LS1 elevator floating up in flight, but at a great drag cost and a reduction in overall canard lift over the span to which the sparrow strainer is applied (roughly 1/8 of the total span of the canard) with the 11.5” sparrow strainer, higher if using the 17.5’ sparrow strainer).

 

As shown above, it is possible to design a more benign elevator shape for the existing LS1 canard that will solve the problem of the elevator floating up in flight without the need for a sparrow strainer, but this solution is not as efficient with respect to drag as would be use of an entirely new airfoil as was done by John Roncz for the Long EZ.

 

This is my analysis so far. I will continue to work on this as time permits.

 

Cheers,

Jay

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