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Still fighting---

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frank-margie(at)worldnet.
Guest

Posted: Sat Jun 24, 2006 8:01 pm Post subject: Still fighting---

Ref. the discussion on roll problems/rigging/etc.,  jerb wrote:

  

 Subject: Re: still fighting



--> Kolb-List message  posted by: jerb <ulflyer(at)verizon.net (ulflyer(at)verizon.net)>



Many  different things can contribute to the flight characteristics 

your  experiencing.  Sounds like a rigging problem.  In order to  

determine the likely cause it will be necessary to properly level the  

aircraft in the proper attitude to take correct meaningful  

measurements.  This becomes a process of elimination.  Refer to  the 

  

 ---------------------

 John/all,

     Sounds like the offset universal  works, once you have eliminated rigging problems as a cause---jerb's list would  be a good guide.

  

     There is another possibility  that hasn't ever been mentioned in discussions on roll problems in Kolbs.   And this may not apply to pushers, or planes with flaps.  But it's worth  thinking about.  I had the same problem on a non-Kolb (Flightstar), which  is a tractor design, and mine does not have flaps.  It does have full-span  ailerons.   We checked everything we could think of, or  anybody we asked could think of.  Engine offset helped, but only a  little. Reducing the droop in the ailerons helped some, but didn't come  close to fixing the problem.  I don't know where I got the idea, but I had  a friend run the plane up while I stood behind it (actually under the  boom, about 2 feet behind the aileron trailing edge).  I held a piece of  cardboard (maybe a foot square) in the propwash---you could feel the difference  between right and left sides, there was a LOT more push on the cardboard on the  left side.  Evidently the descending prop blade pushes more air even when  on the ground.  And it evidently was pushing upward harder on the left  aileron, causing a roll to the left.  This was true even when we adjusted  all the droop out of the ailerons---and they're supposed to be set at 3  degrees.

  

     We put a trim tab on the right  aileron, with the outboard edge even with the tip of the prop arc (this is way  inboard of the usual location for aileron tabs).  Tab is about 12" wide,  2-1/2" deep, and only bent down about 15-20 degrees.  Result was hands off  flying (as far as roll was concerned, we also put a tab on the rudder to fix a  small yaw tendency).

  

     How could this be true on a  pusher?  Especially with your descending blade on the right?  I don't  know, but----your prop is pretty close to the TE of your flaps---could the  descending blade build up pressure above the flap, pushing it down  slightly?  Could the ascending blade be stronger on a Kolb, maybe resulting  in a slight upward push on the left flap (or aileron)?  Is there enough  play in the flap linkage to allow movement?  How close is the prop arc to  the inboard end of the aileron?  I don't know how to check  for thrust differential on a pusher---the propwash isn't separated by  the windscreen like it is on mine, and the cardboard trick obviously won't work.  Wonder what smoke would show about the airflow around the prop?  Just food  for thought.  Having been there, I know what you're going  thru.

  

 Good luck.

  

 Frank Clyma    

 Orange Park, FL

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ulflyer(at)verizon.net
Guest

Posted: Sat Jun 24, 2006 9:18 pm Post subject: Still fighting---

Frank, A Kolb if it has been built straight or any properly design aircraft for that matter, shouldn't need any major trim tabs, you may have masked the symptom but you never determined or corrected the root cause.

 Some thing major is in play with this guys airplane based upon his comments.

 jerb 



 At 11:00 PM 6/24/2006, you wrote:

  	  Quote: 	
		  Ref. the discussion on roll problems/rigging/etc., jerb wrote:

  

 --> Kolb-List message posted by: jerb <ulflyer(at)verizon.net (ulflyer(at)verizon.net)>

 

 Many different things can contribute to the flight characteristics 

 your experiencing.  Sounds like a rigging problem.  In order to 

 determine the likely cause it will be necessary to properly level the 

 aircraft in the proper attitude to take correct meaningful 

 measurements.  This becomes a process of elimination.  Refer to the 

  

 ---------------------

 John/all,

     Sounds like the offset universal works, once you have eliminated rigging problems as a cause---jerb's list would be a good guide.

  

     There is another possibility that hasn't ever been mentioned in discussions on roll problems in Kolbs.  And this may not apply to pushers, or planes with flaps.  But it's worth thinking about.  I had the same problem on a non-Kolb (Flightstar), which is a tractor design, and mine does not have flaps.  It does have full-span ailerons.   We checked everything we could think of, or anybody we asked could think of.  Engine offset helped, but only a little. Reducing the droop in the ailerons helped some, but didn't come close to fixing the problem.  I don't know where I got the idea, but I had a friend run the plane up while I stood behind it (actually under the boom, about 2 feet behind the aileron trailing edge).  I held a piece of cardboard (maybe a foot square) in the propwash---you could feel the difference between right and left sides, there was a LOT more push on the cardboard on the left side.  Evidently the descending prop blade pushes more air even when on the ground.  And it evidently was pushing upward harder on the left aileron, causing a roll to the left.  This was true even when we adjusted all the droop out of the ailerons---and they're supposed to be set at 3 degrees.

  

     We put a trim tab on the right aileron, with the outboard edge even with the tip of the prop arc (this is way inboard of the usual location for aileron tabs).  Tab is about 12" wide, 2-1/2" deep, and only bent down about 15-20 degrees.  Result was hands off flying (as far as roll was concerned, we also put a tab on the rudder to fix a small yaw tendency).

  

     How could this be true on a pusher?  Especially with your descending blade on the right?  I don't know, but----your prop is pretty close to the TE of your flaps---could the descending blade build up pressure above the flap, pushing it down slightly?  Could the ascending blade be stronger on a Kolb, maybe resulting in a slight upward push on the left flap (or aileron)?  Is there enough play in the flap linkage to allow movement?  How close is the prop arc to the inboard end of the aileron?  I don't know how to check for thrust differential on a pusher---the propwash isn't separated by the windscreen like it is on mine, and the cardboard trick obviously won't work. Wonder what smoke would show about the airflow around the prop?  Just food for thought.  Having been there, I know what you're going thru.

  

 Good luck.

  

 Frank Clyma    

 Orange Park, FL

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Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Sun Jun 25, 2006 3:34 am Post subject: Still fighting---

The prop does create a bias as you describe. Note the sides of the 

fuselage just ahead of the prop, the gnats are plastered on the right 

fuselage side, and the underside of the left flap, but not on the left 

side of the fuselage, or the underside of the right flap.



Richard Pike

MKIII N420P (420ldPoops)



frank & margie wrote:

 	  Quote: 	
		   Ref. the discussion on roll problems/rigging/etc., jerb wrote:

  

 Subject: Re: still fighting



 

 <mailto:ulflyer(at)verizon.net>>



 Many different things can contribute to the flight characteristics

 your experiencing.  Sounds like a rigging problem.  In order to

 determine the likely cause it will be necessary to properly level the

 aircraft in the proper attitude to take correct meaningful

 measurements.  This becomes a process of elimination.  Refer to the

  

 ---------------------

 John/all,

     <snip>

 ---your prop is pretty close to the TE of your flaps---could the 

 descending blade build up pressure above the flap, pushing it down 

 slightly?  Could the ascending blade be stronger on a Kolb, maybe 

 resulting in a slight upward push on the left flap (or aileron)?  Is 

 there enough play in the flap linkage to allow movement?  How close is 

 the prop arc to the inboard end of the aileron?  I don't know how to 

 check for thrust differential on a pusher---the propwash isn't 

 separated by the windscreen like it is on mine, and the cardboard 

 trick obviously won't work. Wonder what smoke would show about the 

 airflow around the prop?  Just food for thought.  Having been there, I 

 know what you're going thru.

  

 Good luck.

  

 Frank Clyma   

 Orange Park, FL

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_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Jun 25, 2006 5:37 am Post subject: Still fighting---

How could this be true on a pusher?  Especially with your 

descending blade on the right?

Frank Clyma

Orange Park, FL



Decending blade may not be on the right, depending on what type engine 

is powering the airplane and whether it is turning through a gear box 

or belt drive.  Rotax 2 strokes rotate opposite direction 4 strokes.



john h

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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

ulflyer(at)verizon.net
Guest

Posted: Sun Jun 25, 2006 6:39 am Post subject: Still fighting---

Richard,

That's because there are a bunch more right wings gnats than there 

are left wings.

  jerb



At 06:28 AM 6/25/2006, you wrote:

 	  Quote: 	
		  



The prop does create a bias as you describe. Note the sides of the 

fuselage just ahead of the prop, the gnats are plastered on the 

right fuselage side, and the underside of the left flap, but not on 

the left side of the fuselage, or the underside of the right flap.



Richard Pike

MKIII N420P (420ldPoops)



frank & margie wrote:

>Ref. the discussion on roll problems/rigging/etc., jerb wrote:

>

>Subject: Re: still fighting

>

>

><mailto:ulflyer(at)verizon.net>>

>

>Many different things can contribute to the flight characteristics

>your experiencing.  Sounds like a rigging problem.  In order to

>determine the likely cause it will be necessary to properly level the

>aircraft in the proper attitude to take correct meaningful

>measurements.  This becomes a process of elimination.  Refer to the

>

>---------------------

>John/all,

>     <snip>

>---your prop is pretty close to the TE of your flaps---could the 

>descending blade build up pressure above the flap, pushing it down 

>slightly?  Could the ascending blade be stronger on a Kolb, maybe 

>resulting in a slight upward push on the left flap (or 

>aileron)?  Is there enough play in the flap linkage to allow 

>movement?  How close is the prop arc to the inboard end of the 

>aileron?  I don't know how to check for thrust differential on a 

>pusher---the propwash isn't separated by the windscreen like it is 

>on mine, and the cardboard trick obviously won't work. Wonder what 

>smoke would show about the airflow around the prop?  Just food for 

>thought.  Having been there, I know what you're going thru.

>

>Good luck.

>

>Frank Clyma

>Orange Park, FL

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frank-margie(at)worldnet.
Guest

Posted: Sun Jun 25, 2006 9:33 am Post subject: Still fighting---

jerb wrote:

  

 Frank, A Kolb if it has been built straight or any properly design  

aircraft for that matter, shouldn't need any major trim tabs, you may  

have masked the symptom but you never determined or corrected the root  cause.

Some thing major is in play with this guys airplane based upon his  comments.

jerb

 -----------------------

 jer,

  

     I think you're right on both  counts.  The common use of an offset bushing, however, does indicate  something related especially to Kolbs.  It may be mostly weight offset to  one side when flown solo, as John H points out.  Mine may be related to the  distance from the prop to the windscreen, and the way the windscreen splits the  propwash.  Or I may have something else going on that we never found.   As John also said, we never stop learning.  And to some extent, every plane  is just slightly different---even 2 supposedly identical Mark 3's are probably  just a little different.

  

     jer, would you contact me  off-list?  I have a totally non-Kolb item I'd like to get your input  on.

  

 Frank Clyma

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The BaronVonEvil

Joined: 23 Jun 2006
Posts: 76
Location: Walla Walla, WA.

Posted: Mon Jun 26, 2006 6:05 pm Post subject: Re: Still fighting---

Hi All,



On an Item of note regarding "Still Fighting". I have a Firestar II that I bought used a few years ago. It flew quite well and without trim. About two vears ago I decided to recover the fuselage due to some wear and tear of the fabric and primer failure issues. I thought about repriming the fuselage cage with epoxy primer as had the original builder. However I decided to have the cage powder coated for the better durability it offers.



After completion I flew my Firestar only to find out that now I had a right wing heavy issue and needed lots of trim. I didnt change anything on the wings or struts.  I bought the English Ujoints and corrected the problem by changing the incidence of the left wing. ( It took three washers in the joint).



Apparently during the powdercoat  process of heating up the cage to make the material flow, the heat (400+ degrees) allowed the cage to relax enough here and there to change the incidence between the wing panels.



So if you are thinking of powdercoating your cage, it is highly advisable that you do so at the start of construction. Otherwise you may end up retrimming your plane as I had to.  



Thanks for the Great Kolb Forum



The Baron

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