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Rudder Trim Tab

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kerrjohna(at)comcast.net
Guest

Posted: Mon Aug 25, 2008 10:58 am Post subject: Rudder Trim Tab

Michel, from personal experience with a rudder trim tab that is set for hands/feet of in a cruise condition exhibits no need for "other foot" correction in descent.  I am not sure how to explain the phenomon but maybe it has to do with or the absence of swirling currents off the propeller.

  

 John

  

 [quote]-------------- Original message -------------- 

From: Michel Verheughe <michel(at)online.no> 



 	  Quote: 	
		   > From: Tom Jones [nahsikhs(at)elltel.net] 

 > Michel, a trim tab on a flaperon has been used by Kitfox builders to correct 

 for 

 > a "heavy wing". 

 

 Thanks Tom. I know that it has been used before because I remember talking about 

 it on this forum for maybe three years ago. But since I didn't get much response 

 this time, I was wondering if the current school of thoughts had changed without 

 me knowing it. Sometimes I fall asleep in the classroom!  

 

 The thing is, why do I, and a few others, experience a 'heavy wing' when 

 everything seems to be spick and span and well aligned? Well, there can be a 

 last thing: A slight warp in the flaperon itself. But while it is easy to 

  > m easure the wash-out of the wing, it is more difficult to measure a warp in the 
	


 	  Quote: 	
		   flaperon, less to correct it other than with a tab. 

 

 Cheers, 

 Michel Verheughe 

 Norway 

 Kitfox 3 - Jabiru 2200 ... flying as a PAX 

 

 

  	  Quote: 	
		  

 

 avigator?Kitfox-List

 on

 

	
[b]

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Mon Aug 25, 2008 1:49 pm Post subject: Rudder Trim Tab

If you think a bit about the need for right rudder, which is to  

compensate for the left-turning tendency under precession and torque  

reaction, and then think about there being no torque, and no  

precession during slow flight, I think you'll see there is no need  

for the "other foot" correction. Of course, I'm talking about a  

clockwise-turning (as seen from the pilots' point of view) engine.



Lynn Matteson

Kitfox IV Speedster

Jabiru 2200, 562 hrs and holding for repairs

Status: "Condition grounded, but determined to try."  (Pink  

Floyd..."Learning to Fly")

do not archive





On Aug 25, 2008, at 2:57 PM, kerrjohna(at)comcast.net wrote:



 	  Quote: 	
		   Michel, from personal experience with a rudder trim tab that is set  

 for hands/feet of in a cruise condition exhibits no need for "other  

 foot" correction in descent.  I am not sure how to explain the  

 phenomon but maybe it has to do with or the absence of swirling  

 currents off the propeller.



 John



 -------------- Original message --------------

 From: Michel Verheughe <michel(at)online.no>



 > > From: Tom Jones [nahsikhs(at)elltel.net]

 > > Michel, a trim tab on a flaperon has been used by Kitfox  

 builders to correct

 > for

 > > a "heavy wing".

 >

 > Thanks Tom. I know that it has been used before because I  

 remember talking about

 > it on this forum for maybe three years ago. But since I didn't  

 get much response

 > this time, I was wondering if the current school of thoughts had  

 changed without

 > me knowing it. Sometimes I fall asleep in the classroom! 

 >

 > The thing is, why do I, and a few others, experience a 'heavy  

 wing' when

 > everything seems to be spick and span and well aligned? Well,  

 there can be a

 > last thing: A slight warp in the flaperon itself. But while it is  

 easy to

 > m easure the wash-out of the wing, it is more difficult to  

 measure a warp in the

 > flaperon, less to correct it other than with a tab.

 >

 > Cheers,

 > Michel Verheughe

 > Norway

 > Kitfox 3 - Jabiru 2200 ... flying as a PAX

 >

 >

 >

 >

 > avigator?Kitfox-List

 > on

 www.matronics.com/Navigator?Kitfox-List _- 

 www.matronics.com/contribution _- 

 ============================================================

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Wed Aug 27, 2008 10:38 am Post subject: Rudder Trim Tab

Lynn and John, I am not sure I understand that about the rudder trim tab. If it corrects for the prop under WOT, then it must induce yaw in the other direction at idle, rigth? Did I miss something?



Anyway, I think I'll do like Gary; I'll use a balsa wedge under the left flaperon.



Cheers,

Michel Verheughe

Norway

Kitfox 3 - Jabiru 2200 ... flying as PAX

<pre><b><font size  color="#000000" face="courier new,courier">

_________________
Kitfox 3 - Jabiru 2200

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Wed Aug 27, 2008 11:14 am Post subject: Rudder Trim Tab

It always corrects in the same direction regardless of throttle  

position...that is, fast engine speed or idle. If you stick your hand  

out the window of your car (are the docs letting you drive a car, by  

the way? I was kept from driving for about 3 weeks, as I recall after  

a 5-way bypass surgery in year 2000), it won't make any difference  

how fast you go, the hand will always deflect up, if you hold it  

slightly up, (or down, if you hold it down) no matter how fast you  

go....except at really slow speeds, where the wind against it won't  

make it change.



Think of a sail...NOW I'm talkin' your language....I'm no sailor, but  

it seems if the sail is set to blow you in one direction in a strong  

wind, and the wind dies down, you don't really change direction, do  

you? That may not be a good example. Ok, try this....your rudder is  

straight ahead (or behind, actually), and you stick something on one  

side of it which catches the air. This  will make it push the rudder  

to the other side *slightly*....this is all you are doing with a  

rudder, or any other "trim tab." That little tab that is attached to  

the rudder, elevator, flap, or aileron, is taking the place of you  

exerting a slight pressure on the control of that flight surface (the  

rudder, elevator, flap, or aileron) and lets you remove your foot or  

hand from that control. The more effort you had to exert to keep the  

plane flying straight, level or yawed correctly, the larger the tab  

surface needs to be, or it needs to be bent into the airstream more  

to correct for larger errors in flight direction.



And don't forget....the attached tab, bent into the airstream will  

only correct for one speed, or limited range of speeds...like say  

75-85 knots,or 50-60 knots...and above or below that it corrects too  

much, or not  enough. That's the beauty of having an in-cockpit  

adjustable trim tab...you can go a little faster or slower, and  

compensate for any misalignment of flight direction with the trim tab.



And when I say "bent into the airstream" I mean maybe 5-10 degrees in  

a trailing direction...the tail end of the tab will stick out into  

the airstream, not the front of the tab. Look around your airport,  

Michel, and you'll see lots of examples of trim tabs, some ground  

adjustable some cockpit-controlled...some with mechanical linkages,  

some with electrical servos.



Lynn Matteson

Kitfox IV Speedster

Jabiru 2200, 562 hrs and holding for repairs

Status: "Condition grounded, but determined to try."  (Pink  

Floyd..."Learning to Fly")



On Aug 27, 2008, at 2:37 PM, Michel Verheughe wrote:



 	  Quote: 	
		   Lynn and John, I am not sure I understand that about the rudder  

 trim tab. If it corrects for the prop under WOT, then it must  

 induce yaw in the other direction at idle, rigth? Did I miss  

 something?



 Anyway, I think I'll do like Gary; I'll use a balsa wedge under the  

 left flaperon.



 Cheers,

 Michel Verheughe

 Norway

 Kitfox 3 - Jabiru 2200 ... flying as PAX

 <pre><b><font size  color="#000000" face="courier new,courier">



 List">http://www.matronics.com/Navigator?Kitfox-List</a>

 forums.matronics.com</a>

 www.matronics.com/contribution</a>



 </b></font></pre>

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

57_kid

Joined: 27 Aug 2006
Posts: 50

Posted: Wed Aug 27, 2008 11:58 am Post subject: Rudder Trim Tab

Michael 

while you are just flying along when you apply just a bit of rudder does the

heavy wing go away or do you still have to correct with the ailerons? just

curious because my model 5 had the same problem and no matter what I did it

would not straighten out UNTIL I installed the rudder trim tab, once that

was adjusted for the yaw correction everything was fine .. 

just another opinion

Steve



--

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Wed Aug 27, 2008 12:21 pm Post subject: Rudder Trim Tab

 	  Quote: 	
		   From: steve eccles [eccles(at)Chartermi.net] 

 while you are just flying along when you apply just a bit of rudder does the

 heavy wing go away or do you still have to correct with the ailerons?


	


Well Steve, when I fly level at cruise speed, I only need a very slight pressure on the right pedal to keep the ball in the middle. When I fly like that, yes, the right wing is heavy and I have to correct with the flaperons. Now, I haven't tried with the ball on one or the other side.

My problem for the moment is that I can't go to the airfield to work on the plane because I don't have a driving license. But I will maybe try the rudder tab in time. See my next email to Lynn.



Cheers,

Michel Verheughe

Norway

Kitfox 3 - Jabiru 2200 ... flying as a PAX

<pre><b><font size  color="#000000" face="courier new,courier">

_________________
Kitfox 3 - Jabiru 2200

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Wed Aug 27, 2008 12:42 pm Post subject: Rudder Trim Tab

 	  Quote: 	
		   From: Lynn Matteson [lynnmatt(at)jps.net] 

 It always corrects in the same direction regardless of throttle  

 position...that is, fast engine speed or idle.


	


Well Lynn, I don't remember too much from my theory books but I think a propeller induce four things and I remember three of them. First, the torque that induces a roll. Then the prop in a climb that has a higher angle of incidence on the down blade than the up. That also induces roll. Last, the prop wash that spiral around the fuselage and hit the vertical stab on one side or the other. This induces yaw.



Now, if I have a tab on the rudder and I fly twice as fast, the pressure on the rudder will be four time as great but so will be the pressure on the tab; thus they even out. Okay.



But say you fly at 90 MPH at full throttle then you pull the throttle to idle and push the nose down to keep the same speed. The pressure on the rudder and tab will be the same because the speed is the same, but the side pressure on the vertical stab will be less because the prop is spinning much slower. Hence the effect of the tab in correcting the induced yaw will be different. ... or is it not?



I have lost my driving license for at least one year. I may ask to have it back in one year time if I can prove that I didn't had a new incident during that time. The difference between us is that you had a heart attack. I had a heart attack followed by a cardiac arrest of five minutes. When you loose consciousness because of e.g. epileptic seizure or cardiac arrest or anything that makes you unconscious, you cannot drive a car or even a motorcycle during a certain time. In Norway, the minimum is one year.



The reason I got an implanted cardiac defibrillator is that there is now a chance that I go into cardiac arrest again. Thousands of people die like that every year. They simply fall death in the street of in their sleep. I was fortunate that it started by a mild heart attack and I was already in the ambulance when my heart stopped beating, or actually went into ventricular fibrillation.



Cheers,

Michel Verheughe

Norway

Kitfox 3 - Jabiru 2200 ... flying as PAX

<pre><b><font size  color="#000000" face="courier new,courier">

_________________
Kitfox 3 - Jabiru 2200

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Thu Aug 28, 2008 8:24 am Post subject: Rudder Trim Tab

The other is "precession"...that is what makes a taildragger turn to  

the left (speaking of a clockwise-rotating engine, pilots view) when  

the tail of the plane is raised. Precession occurs when a rotating  

body is subjected to a force applied on its axis, and it always makes  

the axis want to change direction...that's simpler than the  

dictionary explanation, and (I think) is good enough for airplane  

use. The prop is the rotating body, and the axis is the engine and  

airplane that it is fastened to. If you lift the tail of the plane  

when the prop is spinning, the axis (the airplane) tends to go to the  

left (same CW-turning example) unless some rudder correction is  

applied. Remember when you had to use left pedal with that Rotax 2- 

stroke counterclockwise-rotating engine? That's the opposite- 

direction example.

I'm not sure of the pressures that you cite, I just know that the tab  

corrects for having to keep a bit of rudder on one side or the other,  

during sustained level (cruise) flight, and this is the bulk of the  

flying that I do, and when it comes time to land, I land, and I don't  

find that I have to do a lot or think a lot about what I do...I just  

do it.

Lynn Matteson

Kitfox IV Speedster

Jabiru 2200, 562 hrs and holding for repairs

Status: "Condition grounded, but determined to try."  (Pink  

Floyd..."Learning to Fly")

On Aug 27, 2008, at 4:42 PM, Michel Verheughe wrote:

 	  Quote: 	
		  > From: Lynn Matteson [lynnmatt(at)jps.net]

> It always corrects in the same direction regardless of throttle

> position...that is, fast engine speed or idle.

 Well Lynn, I don't remember too much from my theory books but I  

 think a propeller induce four things and I remember three of them.  

 First, the torque that induces a roll. Then the prop in a climb  

 that has a higher angle of incidence on the down blade than the up.  

 That also induces roll. Last, the prop wash that spiral around the  

 fuselage and hit the vertical stab on one side or the other. This  

 induces yaw.

 Now, if I have a tab on the rudder and I fly twice as fast, the  

 pressure on the rudder will be four time as great but so will be  

 the pressure on the tab; thus they even out. Okay.

 But say you fly at 90 MPH at full throttle then you pull the  

 throttle to idle and push the nose down to keep the same speed. The  

 pressure on the rudder and tab will be the same because the speed  

 is the same, but the side pressure on the vertical stab will be  

 less because the prop is spinning much slower. Hence the effect of  

 the tab in correcting the induced yaw will be different. ... or is  

 it not?

 I have lost my driving license for at least one year. I may ask to  

 have it back in one year time if I can prove that I didn't had a  

 new incident during that time. The difference between us is that  

 you had a heart attack. I had a heart attack followed by a cardiac  

 arrest of five minutes. When you loose consciousness because of  

 e.g. epileptic seizure or cardiac arrest or anything that makes you  

 unconscious, you cannot drive a car or even a motorcycle during a  

 certain time. In Norway, the minimum is one year.

 The reason I got an implanted cardiac defibrillator is that there  

 is now a chance that I go into cardiac arrest again. Thousands of  

 people die like that every year. They simply fall death in the  

 street of in their sleep. I was fortunate that it started by a mild  

 heart attack and I was already in the ambulance when my heart  

 stopped beating, or actually went into ventricular fibrillation.

 Cheers,

 Michel Verheughe

 Norway

 Kitfox 3 - Jabiru 2200 ... flying as PAX

 <pre><b><font size  color="#000000" face="courier new,courier">

 List">http://www.matronics.com/Navigator?Kitfox-List</a>

 forums.matronics.com</a>

 www.matronics.com/contribution</a>

 </b></font></pre>

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Thu Aug 28, 2008 9:33 am Post subject: Rudder Trim Tab

 	  Quote: 	
		   From: Lynn Matteson [lynnmatt(at)jps.net]

 The other is "precession"...


	


.. okay, precession, Lynn. But this morning, before the two brain neurones I have left shortcutted, it came back to me: helical propwash!

Isn't that, that makes the plane yaw and require rudder under take off? The propwash goes around the fuselage and press on the vertical stab.



.. well, I'll go and play with my plane, trying different tabs ... when I get my driving license back!



Cheers,

Michel Verheughe

Norway

Kitfox 3 - Jabiru 2200 ... flying as PAX

<pre><b><font size  color="#000000" face="courier new,courier">

_________________
Kitfox 3 - Jabiru 2200

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Thu Aug 28, 2008 10:57 am Post subject: Rudder Trim Tab

It's precession that causes the left swerve when the tail is raised,  

and I guess the "spiraling slipstream" as Wolfgang Langewiesche calls  

it, accounts for some left-turning as well. He negates "torque" as  

much of a factor, and blames it on the spiraling slipstream from the  

prop. This is going on constantly, it would appear, while precession  

occurs only when the longitudinal axis of the plane is raised or  

lowered from the resting position...as in a takeoff roll, or when  

suddenly raising or lowering the nose. It is precession that you feel  

when you spin a roller skate wheel between your fingers, then try to  

tilt the axle one way or the other....or using a spinning bicycle  

wheel to demonstrate the same thing.

Lynn Matteson

Kitfox IV Speedster

Jabiru 2200, 562 hrs and holding for repairs

Status: "Condition grounded, but determined to try."  (Pink  

Floyd..."Learning to Fly")

do not archive

On Aug 28, 2008, at 1:29 PM, Michel Verheughe wrote:

 	  Quote: 	
		  > From: Lynn Matteson [lynnmatt(at)jps.net]

> The other is "precession"...

 ... okay, precession, Lynn. But this morning, before the two brain  

 neurones I have left shortcutted, it came back to me: helical  

 propwash!

 Isn't that, that makes the plane yaw and require rudder under take  

 off? The propwash goes around the fuselage and press on the  

 vertical stab.

 ... well, I'll go and play with my plane, trying different tabs ...  

 when I get my driving license back!

 Cheers,

 Michel Verheughe

 Norway

 Kitfox 3 - Jabiru 2200 ... flying as PAX

 <pre><b><font size  color="#000000" face="courier new,courier">

 List">http://www.matronics.com/Navigator?Kitfox-List</a>

 forums.matronics.com</a>

 www.matronics.com/contribution</a>

 </b></font></pre>

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Thu Aug 28, 2008 12:03 pm Post subject: Rudder Trim Tab

 	  Quote: 	
		   From: Lynn Matteson [lynnmatt(at)jps.net]

 spiraling slipstream from the  

 prop. This is going on constantly, it would appear, while precession  

 occurs only when the longitudinal axis of the plane is raised or  

 lowered from the resting position...as in a takeoff roll


	


Okay, Lynn. But "this is going on constantly" means it is going on at any attitude but it surely must change as the RPM change, right? The same for the precession then.

If the propeller is reponsible for a force, that force must change with the RPM, in my opinion. So, I understand that a rudder trim tab would be self-adjusting to different air speed but I don't see how it would work for different RPM.

When I fly and decide to climb fast at WOT, I automatically press more on the right pedal. How could a tab compensate for that?



Cheers,

Michel Verheughe

Norway

Kitfox 2 - Jabiru 2200 ... flying as PAX

<pre><b><font size  color="#000000" face="courier new,courier">

_________________
Kitfox 3 - Jabiru 2200

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Thu Aug 28, 2008 3:55 pm Post subject: Rudder Trim Tab

The tab...unless it is adjustable from the cockpit...won't compensate  

for any in-flight abnormalities (read: changes of speed or throttle  

setting) besides the one speed that it is set for. Let me give you an  

example of what I encountered, and what I did to take care of it:  My  

plane wanted to drift to the left, so I installed a tab on the  

rudder, with the deflection of the tab going to the left. When the  

air hits the left-bent tab, it pushes it to the right, and this in  

turn pushes the rudder to the right. When the rudder goes *slightly*  

right due to this tab-induced deflection, the plane goes slightly  

right and compensates for the here-to-fore normal left turning  

tendency. Because my tab was a ground-adjustable tab, I had to fly at  

x-speed, sense the turning of the plane, land and adjust the tab, fly  

again at x-speed and see if I did any good, or if I'd have to land  

and adjust it again. I did this a couple of times, and finally got  

it, but it was only good for that one x-speed, give or take a few  

miles per hour. That's why it is best to have a cockpit adjustable  

tab, so that at whatever speed you choose to fly, you can control any  

tendency that the plane has *at that speed*. If you change speed, you  

will have to change the trim tab setting as well....within reason.

When you say "a rudder trim tab would be self-adjusting to different  

air speed", I don't think we're talking about the same type of trim  

tab. The tab that I use, pictured, is fixed, and the only self- 

adjusting that it does is if the plane goes slower, the tab is less  

effective, so I'm guessing that's what you mean?

Lynn Matteson

Kitfox IV Speedster

Jabiru 2200, 562 hrs and holding for repairs

Status: "Condition grounded, but determined to try."  (Pink  

Floyd..."Learning to Fly")

On Aug 28, 2008, at 4:03 PM, Michel Verheughe wrote:

 	  Quote: 	
		  > From: Lynn Matteson [lynnmatt(at)jps.net]

> spiraling slipstream from the

> prop. This is going on constantly, it would appear, while precession

> occurs only when the longitudinal axis of the plane is raised or

> lowered from the resting position...as in a takeoff roll

 Okay, Lynn. But "this is going on constantly" means it is going on  

 at any attitude but it surely must change as the RPM change, right?  

 The same for the precession then.

 If the propeller is reponsible for a force, that force must change  

 with the RPM, in my opinion. So, I understand that a rudder trim  

 tab would be self-adjusting to different air speed but I don't see  

 how it would work for different RPM.

 When I fly and decide to climb fast at WOT, I automatically press  

 more on the right pedal. How could a tab compensate for that?

 Cheers,

 Michel Verheughe

 Norway

 Kitfox 2 - Jabiru 2200 ... flying as PAX

 <pre><b><font size  color="#000000" face="courier new,courier">

 List">http://www.matronics.com/Navigator?Kitfox-List</a>

 forums.matronics.com</a>

 www.matronics.com/contribution</a>

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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

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