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Sabrina Re: pitching the H-stab
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victorbravo(at)sbcglobal.
Guest

Posted: Mon Feb 11, 2008 10:45 am Post subject: Sabrina Re: pitching the H-stab

Sabrina, this would be an important question to ask directly to Zenair, 

specifically to Chris Heintz personally. I have no doubt he would be 

willing to answer your question. Changing the angle that the tail is 

mounted on the airplane is a big change. It's not something you can do 

just because someone else has done it or thinks it will work. It has a 

huge effect on the safety and stability of the airplane.



Sabrina wrote:

 	  Quote: 	
		   



 "Overall, moving the stabilizer has been a big success. I plan to add another degree in prop pitch from 10 to 11 degrees at the tip and see what that does. Top speed right now is around 120 mph. We started with 85 at wide open throttle. Climb speed now at 90 mph is 500 fpm - also an improvement since moving the horiz. stabilizer and re-pitching the prop. Oil Temps have come down significantly with several changes to the cowl and prop pitch.  Scott Laughlin www.cooknwithgas.com"



 Assuming a pitch up 1 degree mis-configuration to a 1 degree down,  total 2 degree change could easily result in a 10% increase in speed.   Scott has demonstrated results.  As far as the person at Air Venture, it should not be too hard to figure out who he is, how many people live near Oshkosh and have built 2 601s.   Thank you Sir, if you are reading this.





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=163510#163510

amyvega2005(at)earthlink.
Guest

Posted: Mon Feb 11, 2008 11:57 am Post subject: Sabrina Re: pitching the H-stab

all said, thats the fun of experimental! Thou art the builder!



Juan



--

victorbravo(at)sbcglobal.
Guest

Posted: Mon Feb 11, 2008 1:27 pm Post subject: Sabrina Re: pitching the H-stab

Sabrina wrote:

 	  Quote: 	
		   Cessna has proven than tail down force on slow aircraft is an acceptable design.  

Congratulations on your excellent grasp of airplane design... we're all 
	


genuinely blown away. Here's the "rest of the story" about the tail 

angle issue for you to consider:



 Just about all of the (non-canard) airplanes flying in the world today 

have downforce on the tail. Looking at the highly cambered airfoils that 

Zenith airplanes use, it is just about guaranteed that there is a large 

pitching (twisting)  moment on the airfoil, meaning that a significant 

amount of downforce is needed in the back to balance it.



As any airplane designer will tell you, at any "normal" CG the wing and 

tail have to be at some angle to each other for the airplane to be 

stable. This angle I believe is called "decalage" and has nothing to do 

with the fuselage at all. It is the relationship between wing and 

stabilizer. Once that decalage angle is determined you can just put the 

fuselage in between them at whatever angle gives the lowest cruise drag.



HOWEVER, once an airplane has been built, when you need to adjust the 

angle of the tail for some reason, it will change BOTH the decalage AND 

the angle of the wing/fuselage (incidence). So if you just change the 

tail angle and nothing else, you can be improving the wing/tail 

relationship on one hand, and screwing up the fuselage angle worse on 

the other hand.



So, when professional designers have to adjust the decalage angle, they 

usually make the adjustment at BOTH the wing angle of incidence and the 

tail angle... to keep the fuselage flying straight after they changed 

the relationship between the wing and tail.



Bill Berle

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Mon Feb 11, 2008 2:03 pm Post subject: Re: Sabrina Re: pitching the H-stab

Pitch trim in my Kitfox is via an actuator that moves the entire horizontal 

stab. Full deflection on the leading edge is several inches up and down.

Obviously it is NOT a 601, however what it tells me is that the minor

changes you are talking about will probably not dramatically affect the

planes handling to the point of dangerous. But if you overdo it you may

have to use heavier than normal stick force if you go the wrong way with

your change and can't compensate with trim.



There's always variation from airplane to airplane, minor changes to

the horiz. stab incidence to adjust the trim is a perfectly reasonable

thing to do. Just go a little at a time and you'll be ok.



Regards,

Jeff

craig(at)craigandjean.com
Guest

Posted: Mon Feb 11, 2008 2:17 pm Post subject: Sabrina Re: pitching the H-stab

Isn't that the way a Mooney does it?



-- Craig



--

victorbravo(at)sbcglobal.
Guest

Posted: Mon Feb 11, 2008 3:14 pm Post subject: Sabrina Re: pitching the H-stab

I was talking about geometric decalage, which is easier to deal with and 

more appropriate when talking about cruise stability. Airplanes very 

rarely fly at the wing's zero-lift angle, and if they do... it ain't for 

long 



It appears that this all started with someone wanting to deviate from 

Chris' designed decalage angle, because someone was unhappy with the 

elevator authority or the force required for liftoff and flare. So my 

point was that if you want to deviate from that decalage angle you 

should know whether it was really wrong in the first place, and then 

whether changing it could cause some unwanted side effect. For example, 

if the leading edge of the stabilizer were lowered, there is some 

possibility that the "restorative force" applied by stabilizer in spin 

recovery could be weakened, in other words the airplane would tend to 

not lower the nose as much as otherwise. That's the kind of thing that 

needs a real aero engineer to look into.



Bill



Sabrina wrote:

 	  Quote: 	
		   



 You assume the change was made after the rear spar was set.  This is a long design process that involves a little bit of math.  It is inherent in creating an E-LSA as opposed to an amateur built aircraft.  I am sure Chris can help you maintain his desinged decalage and supply you with the proper dimension (distance from main longeron to top rear spar) for the Riblett GA 35-A-415 airfoil (601 wing) depending upon the angle of incident you choose for the horizontal stab.    You guys are almost as tough as my professors!   Ouch.   Where you referring to the aerodynamic decalage or the geometric decalage?    In building an E-LSA, I had to get it right the first time because once certified, it takes an IA to make a major alteration to an E-LSA, and this would be a major alteration. Again, what is right for my craft might not be right for yours.  Do you have a 3" spacer and metal prop?  Do you have 90 extra pounds spread across the airframe compared to the AMD?  Etc...   Relax, an!

  d enjoy the process...





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=163557#163557

john.marzulli(at)gmail.co
Guest

Posted: Mon Feb 11, 2008 3:42 pm Post subject: Sabrina Re: pitching the H-stab

..and Cub Crafter's PA-18.



DO NOT ARCHIVE



On Feb 11, 2008 2:14 PM, Craig Payne <craig(at)craigandjean.com (craig(at)craigandjean.com)> wrote:

[quote] --> Zenith-List message posted by: "Craig Payne" <craig(at)craigandjean.com (craig(at)craigandjean.com)>



Isn't that the way a Mooney does it?



-- Craig

 



--

Jeyoung65(at)aol.com
Guest

Posted: Mon Feb 11, 2008 3:52 pm Post subject: Sabrina Re: pitching the H-stab

Also used to fly faster that mach 1

  

  In a message dated 2/11/2008 6:43:10 P.M. Eastern Standard Time,  john.marzulli(at)gmail.com writes:

 [quote]...and    Cub Crafter's PA-18.



DO NOT ARCHIVE



   On Feb 11, 2008 2:14 PM, Craig Payne <craig(at)craigandjean.com (craig(at)craigandjean.com)> wrote:

   [quote]-->      Zenith-List message posted by: "Craig Payne" <craig(at)craigandjean.com (craig(at)craigandjean.com)>



Isn't      that the way a Mooney does it?



--  Craig

          

     

--

amyvega2005(at)earthlink.
Guest

Posted: Mon Feb 11, 2008 4:02 pm Post subject: Sabrina Re: pitching the H-stab

Berle,

give the young lady a brake(aero pun intended)! Telling her a "real engineeer" needs to look at this issue is a bit hubris for the fact that she redesigned an engine, built the plane and flew it.   If she did the math, give her the respect she deserves. we may not al agree to mess with the angles , I think some of us forget the kit is just a kit, and you are the manufacturer,  did you forget the word"experimental" in your vernacular?



You go girl!



Juan



--

barcusc(at)comcast.net
Guest

Posted: Mon Feb 11, 2008 4:21 pm Post subject: Sabrina Re: pitching the H-stab

Chris Heinz is a "real engineer" and I would trust his opinion or I would 

not have bought the 601 XL in the first place. I have had the pleasure of 

discussing concerns with him more than once and he always gave a thoughtful 

and clear response. I am convinced Chris does not take questions or concerns 

lightly, if the change or adjustment you are asking about is anywhere near a 

grey area I am sure he would immediately inform you of the danger involved.



Clyde Barcus

601 XL



 ----- 

From: "Bill Berle" <victorbravo(at)sbcglobal.net>

To: <zenith-list(at)matronics.com>

Sent: Monday, February 11, 2008 5:10 PM

Subject: Re: Sabrina Re: pitching the H-stab

 	  Quote: 	
		   



 I was talking about geometric decalage, which is easier to deal with and 

 more appropriate when talking about cruise stability. Airplanes very 

 rarely fly at the wing's zero-lift angle, and if they do... it ain't for 

 long 



 It appears that this all started with someone wanting to deviate from 

 Chris' designed decalage angle, because someone was unhappy with the 

 elevator authority or the force required for liftoff and flare. So my 

 point was that if you want to deviate from that decalage angle you should 

 know whether it was really wrong in the first place, and then whether 

 changing it could cause some unwanted side effect. For example, if the 

 leading edge of the stabilizer were lowered, there is some possibility 

 that the "restorative force" applied by stabilizer in spin recovery could 

 be weakened, in other words the airplane would tend to not lower the nose 

 as much as otherwise. That's the kind of thing that needs a real aero 

 engineer to look into.



 Bill



 Sabrina wrote:

> 

>

> You assume the change was made after the rear spar was set.  This is a 

> long design process that involves a little bit of math.  It is inherent 

> in creating an E-LSA as opposed to an amateur built aircraft.  I am sure 

> Chris can help you maintain his desinged decalage and supply you with the 

> proper dimension (distance from main longeron to top rear spar) for the 

> Riblett GA 35-A-415 airfoil (601 wing) depending upon the angle of 

> incident you choose for the horizontal stab.    You guys are almost as 

> tough as my professors!   Ouch.   Where you referring to the aerodynamic 

> decalage or the geometric decalage?    In building an E-LSA, I had to get 

> it right the first time because once certified, it takes an IA to make a 

> major alteration to an E-LSA, and this would be a major alteration. 

> Again, what is right for my craft might not be right for yours.  Do you 

> have a 3" spacer and metal prop?  Do you have 90 extra pounds spread 

> across the airframe compared to the AMD?  Etc...   Relax, !

 an!

>  d enjoy the process...

>

>

> Read this topic online here:

>

> http://forums.matronics.com/viewtopic.php?p=163557#163557

>

>

planecrazydld(at)Yahoo.co
Guest

Posted: Mon Feb 11, 2008 4:25 pm Post subject: Sabrina Re: pitching the H-stab

some of the mooneys pitch (and yaw as well i think) the entire rear tip of the fuselage supporting the entire empennage.



Craig Payne <craig(at)craigandjean.com> wrote:[quote] --> Zenith-List message posted by: "Craig Payne" 



Isn't that the way a Mooney does it?



-- Craig



--

tigerrick(at)mindspring.c
Guest

Posted: Mon Feb 11, 2008 9:01 pm Post subject: Sabrina Re: pitching the H-stab

Hear, hear, Juan!



Right on the money, compadre!



No aircraft designer, no matter how talented, can possibly anticipate the variety of subtle CG shifts in every single flying example that is built under the amateur category.  Sure, there's an acceptable CG range, but I doubt any two 601s will leave the hangar with identical weights or CGs.



The proof of the pudding is the flight test, period.  This is where you really find out if the slow speed characteristics of the aiplane are acceptable, or not.  Since the 601 wants to fly at a comparatively low airspeed (about 45 mph in my case), it's important that there's enough control authority available to take full advantage of it.



After all, it's not the designer's job to fine tune each and every airframe to perfection - it's ours.  And to fly an out of trim, or out of rig airplane "because the plans said so" is missing the point entirely.  The designer provides the broad brush strokes.  WE fill in the details.



Sabrina, you GO girl!!



Rick Lindstrom, Contributing Editor

KITPLANES Magazine

N42KP

--

jlatimer1(at)cox.net
Guest

Posted: Tue Feb 12, 2008 9:38 am Post subject: Sabrina Re: pitching the H-stab

Super Cubs do it this way also.

Jerry 



--

NYTerminat(at)aol.com
Guest

Posted: Mon Feb 18, 2008 10:32 pm Post subject: Sabrina Re: pitching the H-stab

Hi all,

  

 With all the talk of pitching the horizontal  stabilizer lately I have a quick question. I am doing my conditional inspection  on my 701 and decided to replace the front horizontal stabilizer brackets to the  .063 material. There were no cracks in my old ones but I figured I might as well  bite the bullet now while the weather is keeping me from flying anyway. I have  always felt that I was flying in a nose high attitude while at cruise and that I  do not see the higher MPH that others see. I purchased a digital level and have  discovered that my horizontal stabilizer was about a half of a degree low in the  front (approx 3 mm). I plan on raising it one degree so that I will be a half of  a degree higher in the front based on the A-E line. I am wondering if this is a  good idea as I believe this will get me flying in a better attitude at cruise  and pick up some speed. Any thoughts?

  

 Bob Spudis

 N701Zx/ CH-701/ 912S/  140hrs

  

  

  

  

  

 In a message dated 2/11/2008 2:20:58 P.M. Eastern Standard Time,  chicago2paris(at)msn.com writes:

  	  Quote: 	
		  -->    Zenith-List message posted by: "Sabrina"    <chicago2paris(at)msn.com>



Zenith Aircraft indicated it was a "good    idea."  I can't imagine that they would say so without calling up Chris    in France.  So too, the math seems to work out, but more importantly,    people have done it and proved it. (Bryan, Scott and several others.)  I    personally would not go to 3 degrees.   The AMDs appear to be about    1 degree down, but they will not confirm that.   The problem may be    that some actually have the stab pitched slightly up, and that is in fact more    dangerous than pitching it slightly down with a nose heavy    aircraft.   Cessna has proven than tail down force on slow aircraft    is an acceptable design.  W&B on a 601 is critical.   One    must always start with an accurate weight and balance sheet (in other words,    don't use bathroom scales.)





Read this topic online    here:



http://forums.matronics.com/viewtopic.php?p=163526#163526

	


 

  



Delicious ideas to please the pickiest eaters. Watch the video on AOL Living.

  [quote][b]

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Tue Feb 19, 2008 12:29 am Post subject: Sabrina Re: pitching the H-stab

The stabilizer has little to do with the cruise flight attitude of the fuselage, it mainly has to do with the trim condition of the airplane. If you can trim out the elevator forces in cruise without excessive trim tab deflection, re-pitching the stabilizer won't help you. I re-pitched my stabilizer because I couldn't trim out the stick forces, not because the attitude of the airplane was wrong. I had to hold back pressure on the stick all the time to keep the plane from diving. 

The cruise flight attitude of the fuselage is controlled mainly by the angle of incidence of the main wing. Increasing the angle of incidence of the main wing will bring the nose of the fuselage down, but then you will also have to pitch the stabilizer up to get it back into trim.

On Feb 19, 2008, at 1:26 AM, NYTerminat(at)aol.com (NYTerminat(at)aol.com) wrote:

 	  Quote: 	
		       

   Hi all,

  

 With all the talk of pitching the horizontal stabilizer lately I have a quick question. I am doing my conditional inspection on my 701 and decided to replace the front horizontal stabilizer brackets to the .063 material. There were no cracks in my old ones but I figured I might as well bite the bullet now while the weather is keeping me from flying anyway. I have always felt that I was flying in a nose high attitude while at cruise and that I do not see the higher MPH that others see. I purchased a digital level and have discovered that my horizontal stabilizer was about a half of a degree low in the front (approx 3 mm). I plan on raising it one degree so that I will be a half of a degree higher in the front based on the A-E line. I am wondering if this is a good idea as I believe this will get me flying in a better attitude at cruise and pick up some speed. Any thoughts?

  

 Bob Spudis

 N701Zx/ CH-701/ 912S/ 140hrs

  

  

	






 -- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.



 



 [quote][b]

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

n801bh(at)netzero.com
Guest

Posted: Tue Feb 19, 2008 5:12 am Post subject: Sabrina Re: pitching the H-stab

Hi Bob. I built my 801 as close to the specs as I could and measured my wing and horizontal stabilizer incidence multiple times. I am very confident I have my plane right and it to flys nose up. If I set it up in level  cruise flight and add just a little bit of flaps the nose drops a couple of degrees and it picks up about 4 mph. I don't know if I want to try to change the tail setting cause mine is all painted and it will be major surgery to switch. 

  

Ben Haas

N801BH

www.haaspowerair.com 

do not archive



    

  Hi all,

  

 With all the talk of pitching the horizontal stabilizer lately I have a quick question. I am doing my conditional inspection on my 701 and decided to replace the front horizontal stabilizer brackets to the .063 material. There were no cracks in my old ones but I figured I might as well bite the bullet now while the weather is keeping me from flying anyway. I have always felt that I was flying in a nose high attitude while at cruise and that I do not see the higher MPH that others see. I purchased a digital level and have discovered that my horizontal stabilizer was about a half of a degree low in the front (approx 3 mm). I plan on raising it one degree so that I will be a half of a degree higher in the front based on the A-E line. I am wondering if this is a good idea as I believe this will get me flying in a better attitude at cruise and pick up some speed. Any thoughts?

  

 Bob Spudis

 N701Zx/ CH-701/ 912S/ 140hrs

  

  

  

  

  

 In a message dated 2/11/2008 2:20:58 P.M. Eastern Standard Time, chicago2paris(at)msn.com writes:

  	  Quote: 	
		  --> Zenith-List message posted by: "Sabrina" <chicago2paris(at)msn.com>



Zenith Aircraft indicated it was a "good idea."  I can't imagine that they would say so without calling up Chris in France.  So too, the math seems to work out, but more importantly, people have done it and proved it. (Bryan, Scott and several others.)  I personally would not go to 3 degrees.   The AMDs appear to be about 1 degree down, but they will not confirm that.   The problem may be that some actually have the stab pitched slightly up, and that is in fact more dangerous than pitching it slightly down with a nose heavy aircraft.   Cessna has proven than tail down force on slow aircraft is an acceptable design.  W&B on a 601 is critical.   One must always start with an accurate weight and balance sheet (in other words, don't use bathroom scales.)





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=163526#163526

	


 

  



   Delicious ideas to please the pickiest eaters. Watch the video on AOL Living.

 	  Quote: 	
		  



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_____________________________________________________________

Click here for legal help with your social security disability!

   [quote][b]

daveaustin2(at)primus.ca
Guest

Posted: Tue Feb 19, 2008 6:25 am Post subject: Sabrina Re: pitching the H-stab

Bob,

 I'd be interested to know where your trim tab is  positioned when at cruise with what I would describe as your "usual" loading of  the aircraft?  (conditions you fly under most of the time).  It should  be at a neutral position.  If not, then adjust the hor. stab angle to give  that condition.  (Does mean you have to land without moving the elevator  trim a few times).  That produces least drag for that flying  condition.  I slotted the rear attachments to give me the adjustment, then  replaced them with unslotted.

 Following from that, the trim tab needs to be large  enough to be able to trim properly for approach and landing.

 Dave Austin  601HDS - 912, Spitfire Mk  VIII

    [quote][b]

NYTerminat(at)aol.com
Guest

Posted: Tue Feb 19, 2008 7:32 am Post subject: Sabrina Re: pitching the H-stab

Ben, Mine reacts the same way. I didn't want to mess up my paint job either  but I am using an artist brush to repaint the rivets, primed them last night,  will see today how it comes out. Every once in a while I will hit a sweet spot  and the nose will be a little lower in cruise and the plane will do about 6-7mph  faster, I can usually find the spot if I bump the nose down in cruise but not  all the time. The plane will fly hands off with the elevator trim in neutral but  I know it can do better. 

  

 Bob

  

  

  

  

 In a message dated 2/19/2008 8:14:04 A.M. Eastern Standard Time,  n801bh(at)netzero.com writes:

  	  Quote: 	
		     

Hi Bob. I built my 801 as close to the specs as I could and measured my    wing and horizontal stabilizer incidence multiple times. I am very confident I    have my plane right and it to flys nose up. If I set it up in level     cruise flight and add just a little bit of flaps the nose drops a couple of    degrees and it picks up about 4 mph. I don't know if I want to try to change    the tail setting cause mine is all painted and it will be major surgery to    switch.   

    

Ben Haas

N801BH

www.haaspowerair.com   

do not archive

	


 

  



Delicious ideas to please the pickiest eaters. Watch the video on AOL Living.

  [quote][b]

NYTerminat(at)aol.com
Guest

Posted: Tue Feb 19, 2008 7:45 am Post subject: Sabrina Re: pitching the H-stab

Dave,

 My trim is centered in cruise. I usually fly alone, not much change with a  passenger. My CG is slightly aft but well within range. I like the idea of a  slotted bracket to try different settings. If this setting that I am choosing  doesn't work, I may try the slotted bracket to adjust the rear of the  stabilizer. How much of a difference does one degree or 6 mm make? I know that  the 601 and 701 are different but they would probably react similar.

  

 Bob

  

  

  

  

  

 In a message dated 2/19/2008 9:26:55 A.M. Eastern Standard Time,  daveaustin2(at)primus.ca writes:

  	  Quote: 	
		     Bob,

   I'd be interested to know where your trim tab is    positioned when at cruise with what I would describe as your "usual" loading    of the aircraft?  (conditions you fly under most of the time).  It    should be at a neutral position.  If not, then adjust the hor. stab angle    to give that condition.  (Does mean you have to land without moving the    elevator trim a few times).  That produces least drag for that flying    condition.  I slotted the rear attachments to give me the adjustment,    then replaced them with unslotted.

   Following from that, the trim tab needs to be    large enough to be able to trim properly for approach and  landing.

   Dave Austin  601HDS - 912, Spitfire Mk    VIII

	


 

  



Delicious ideas to please the pickiest eaters. Watch the video on AOL Living.

  [quote][b]

daveaustin2(at)primus.ca
Guest

Posted: Tue Feb 19, 2008 8:21 am Post subject: Sabrina Re: pitching the H-stab

Bob,

 The slot was about 1/4 inch long before I got it  the way I wanted.  Be sure to leave good edge clearance to the  slot!

 Re other notes, I haven't been able to figure out  how you can put the nose down without losing height, since the wing incidence  would change from level flight.  If the flaps or ailerons are adjusted for  greatest speed, I understand that, but then wouldn't you want to adjust the hor.  stab for trim neutral?

 Dave Austin  601HDS - 912, Spitfire Mk  VIII

    [quote][b]

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