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Trim tab slaving?

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a.s.elliott(at)cox.net
Guest

Posted: Tue Feb 22, 2011 7:13 am Post subject: Trim tab slaving?

Gang:

 

On my 601XL, the elevator trim tab is not effective enough to trim out all control forces on a full-flap final when the CG is in the front half of the allowed range.  Although the remaining elevator forces are light, I would like to be able to trim them away.  The trim tab is inset on one side of the elevator, and takes the entire width, minus about 20 mm on each end.  Servo is RAC

 

One option would be to add another trim tab to the other side of the elevator.  But to do that I would need some way to slave the two sides together.  Does anyone have an idea about how to do that electronically without very high cost, or perhaps some way already exists and I haven't found it?  (The elevator design doesn't allow for a simple mechanical connection.)

 

Another option, of course, would to be to increase the size of the trim tab, either making it full width (probably not too effective - delta area <10%), or extending it aft 20-25 mm (probably would work, but ugly), or both.  I might go that way, but thought I'd ask about the saving first.

 

Thanks,

Andy

 

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

Andy Elliott

N601GE/Z601XL/TD/Corvair

298 hrs since 11/08

 

  [quote][b]

n801bh(at)netzero.com
Guest

Posted: Tue Feb 22, 2011 7:41 am Post subject: Trim tab slaving?

I vote for extending it aft.. Syncronizing two servos are problematic for sure,

do not archive

Ben Haas

N801BH

www.haaspowerair.com



--------

dave.saylor.aircrafters(a
Guest

Posted: Tue Feb 22, 2011 7:46 am Post subject: Trim tab slaving?

My RV has tabs on both elevators, each cable-driven by a single servo.

 I think it would be needlessly complicated to get two servos married

together at all times.  If you didn't do that, you'd have to have some

scheme to make sure they were at least able to be manually

coordinated.



I'd recommend extending the existing tab.  You might not need as much

as you think.  We regularly just tape a tab on temporarily until we

figure out what size to use.



Dave Saylor

AirCrafters

140 Aviation Way

Watsonville, CA 95076

831-722-9141 Shop

831-750-0284 Cell



On Tue, Feb 22, 2011 at 7:09 AM, Dr. Andrew Elliott <a.s.elliott(at)cox.net> wrote:

 	  Quote: 	
		   Gang:



 On my 601XL, the elevator trim tab is not effective enough to trim out all

 control forces on a full-flap final when the CG is in the front half of the

 allowed range.Â  Although the remaining elevator forces are light, I would

 like to be able to trim them away.Â  The trim tab is inset on one side of the

 elevator, and takes the entire width, minus about 20 mm on each end.Â  Servo

 is RAC



 One option would be to add another trim tab to the other side of the

 elevator.Â  But to do that I would need some way to slave the two sides

 together.Â  Does anyone have an idea about how to do that electronically

 without very high cost, or perhaps some way already exists and I haven't

 found it?Â  (The elevator design doesn't allow for a simple mechanical

 connection.)



 Another option, of course, would to be to increase the size of the trim tab,

 either making it full width (probably not too effective - delta area <10%),

 or extending it aft 20-25 mm (probably would work, but ugly), or both.Â  I

 might go that way, but thought I'd ask about the saving first.



 Thanks,



 Andy



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



 Andy Elliott



 N601GE/Z601XL/TD/Corvair



 298 hrs since 11/08

mrspudandcompany(at)veriz
Guest

Posted: Tue Feb 22, 2011 8:14 am Post subject: Trim tab slaving?

[quote]On my 601XL, the elevator trim tab is not effective enough to trim out all control forces on a full-flap final when the CG is in the front half of the allowed range.  Although the remaining elevator forces are light, I would like to be able to trim them away.   Andy, Can your existing trim tab be adjusted to go slitely farther than it now goes. I.e., can the actuator be adjusted to give a little more downward deflection to the tab.  Since you are on the edge of being in trim this might be a solution without any further mods. Roger [b]

raymondj(at)frontiernet.n
Guest

Posted: Tue Feb 22, 2011 8:29 am Post subject: Trim tab slaving?

Would VGs on the trim tab offer any benefit?  Still might be ugly but 

quick to try.



Raymond Julian

Kettle River, MN



On 02/22/2011 09:09 AM,  Dr. Andrew Elliott wrote:

 	  Quote: 	
		   Gang:



 On my 601XL, the elevator trim tab is not effective enough to trim out

 all control forces on a full-flap final when the CG is in the front half

 of the allowed range. Although the remaining elevator forces are light,

 I would like to be able to trim them away. The trim tab is inset on one

 side of the elevator, and takes the entire width, minus about 20 mm on

 each end. Servo is RAC



 One option would be to add another trim tab to the other side of the

 elevator. But to do that I would need some way to slave the two sides

 together. Does anyone have an idea about how to do that electronically

 without very high cost, or perhaps some way already exists and I haven't

 found it? (The elevator design doesn't allow for a simple mechanical

 connection.)



 Another option, of course, would to be to increase the size of the trim

 tab, either making it full width (probably not too effective - delta

 area <10%), or extending it aft 20-25 mm (probably would work, but

 ugly), or both. I might go that way, but thought I'd ask about the

 saving first.



 Thanks,



 Andy



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



 Andy Elliott



 N601GE/Z601XL/TD/Corvair



 298 hrs since 11/08



 *

 *

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Tue Feb 22, 2011 8:32 am Post subject: Trim tab slaving?

Take a look at the wickerbill, otherwise known in the U.S. as the Gurney flap.



Rick Girard



On Tue, Feb 22, 2011 at 9:09 AM, Dr. Andrew Elliott <a.s.elliott(at)cox.net (a.s.elliott(at)cox.net)> wrote:

  	  Quote: 	
		  

Gang: 

 

On my 601XL, the elevator trim tab is not effective enough to trim out all control forces on a full-flap final when the CG is in the front half of the allowed range.  Although the remaining elevator forces are light, I would like to be able to trim them away.  The trim tab is inset on one side of the elevator, and takes the entire width, minus about 20 mm on each end.  Servo is RAC 

 

One option would be to add another trim tab to the other side of the elevator.  But to do that I would need some way to slave the two sides together.  Does anyone have an idea about how to do that electronically without very high cost, or perhaps some way already exists and I haven't found it?  (The elevator design doesn't allow for a simple mechanical connection.) 

 

Another option, of course, would to be to increase the size of the trim tab, either making it full width (probably not too effective - delta area <10%), or extending it aft 20-25 mm (probably would work, but ugly), or both.  I might go that way, but thought I'd ask about the saving first. 

 

Thanks,

 Andy

 

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

Andy Elliott

N601GE/Z601XL/TD/Corvair 

298 hrs since 11/08

 

   	  Quote: 	
		  



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-- 

Zulu Delta

Mk IIIC

Thanks, Homer GBYM

It isn't necessary to have relatives in Kansas City in order to be unhappy.

   - Groucho Marx



 

  [quote][b]

_________________
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BobsV35B(at)aol.com
Guest

Posted: Tue Feb 22, 2011 8:35 am Post subject: Trim tab slaving?

Good Morning Andy,

  

 Have you thought about adding a small angle on the top and bottom of your  trim tab?

  

 Some control surfaces experience seperation at the trailing edges. One  trick that has been used was to add a small angle to the trim tab or,  occasionally, the whole surface to increase effectiveness. Supposedly, if   the air is separating at that point, the angles create very little additional  drag and do a good job of increasing affectivity. That was how Morane-Saulnier  solved the problem on their Paris Jet 760.

  

 Happy Skies,

  

 Old Bob

  

  In a message dated 2/22/2011 10:15:39 A.M. Central Standard Time,  mrspudandcompany(at)verizon.net writes:

  	  Quote: 	
		        

  	  Quote: 	
		  On my 601XL, the elevator trim tab is not effective enough to trim out all control forces on a full-flap final when the CG is in the front half of the allowed range.  Although the remaining elevator forces are light, I would like to be able to trim them away.   Andy, Can your existing trim tab be adjusted to go slitely farther than it now goes. I.e., can the actuator be adjusted to give a little more downward deflection to the tab.  Since you are on the edge of being in trim this might be a solution without any further mods. Roger 



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  [quote][b]

glastar(at)gmx.net
Guest

Posted: Tue Feb 22, 2011 8:38 am Post subject: Trim tab slaving?

Andy,



there might be another way, on the Glastar a similar issue exists 

especially for TD's. Two ways did help, first one was having a tape over 

the hinge line between HS and Elevator, this did increase effectiveness 

(not sure the 601 is using hinges?) Then another was to add some vortex 

generator in front of the tab (lower side) increasing effectiveness of 

the tab as well.



Werner



On 22.02.2011 16:09,  Dr. Andrew Elliott wrote:

 	  Quote: 	
		   Gang:



 On my 601XL, the elevator trim tab is not effective enough to trim out

 all control forces on a full-flap final when the CG is in the front half

andrew.d.zachar(at)gmail.
Guest

Posted: Tue Feb 22, 2011 9:13 am Post subject: Trim tab slaving?

A T-strip would most effectively increase the hinge moment of the tab, thus increasing it's effectiveness.



Be careful though, messing with hinge-moments on a surface so far away from the elevator hinge line can quickly get you into trouble flutter-style if you don't have some flutter analysis to back it up.

 



(Also, a t-strip on the tab would also increase the hinge moments on the elevator resulting in higher longitudinal pitch forces.)

I'd stick with increased tab travel or second tab on the other elevator.

 

On Tue, Feb 22, 2011 at 11:23 AM, rayj <raymondj(at)frontiernet.net (raymondj(at)frontiernet.net)> wrote:

 	  Quote: 	
		   --> AeroElectric-List message posted by: rayj <raymondj(at)frontiernet.net (raymondj(at)frontiernet.net)>

 

 Would VGs on the trim tab offer any benefit?  Still might be ugly but quick to try.

 

 Raymond Julian

 Kettle River, MN

 

 On 02/22/2011 09:09 AM,  Dr. Andrew Elliott wrote:

  	  Quote: 	
		   Gang:

 

 On my 601XL, the elevator trim tab is not effective enough to trim out

 all control forces on a full-flap final when the CG is in the front half

 of the allowed range. Although the remaining elevator forces are light,



 I would like to be able to trim them away. The trim tab is inset on one

 side of the elevator, and takes the entire width, minus about 20 mm on

 each end. Servo is RAC

 

 One option would be to add another trim tab to the other side of the

 elevator. But to do that I would need some way to slave the two sides

 together. Does anyone have an idea about how to do that electronically

 without very high cost, or perhaps some way already exists and I haven't

 found it? (The elevator design doesn't allow for a simple mechanical

 connection.)

 

 Another option, of course, would to be to increase the size of the trim

 tab, either making it full width (probably not too effective - delta

 area <10%), or extending it aft 20-25 mm (probably would work, but

 ugly), or both. I might go that way, but thought I'd ask about the

 saving first.

 

 Thanks,

 

 Andy

 

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

 

 Andy Elliott

 

 N601GE/Z601XL/TD/Corvair

 

 298 hrs since 11/08

 



 *

 

 

 *

 	


 

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 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

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-- 

Andrew Zachar

andrew.d.zachar(at)gmail.com (andrew.d.zachar(at)gmail.com)

 

  [quote][b]

40950(at)rv10.net
Guest

Posted: Tue Feb 22, 2011 7:20 pm Post subject: Trim tab slaving?

Dr Elliot,

Adjust / extend the throw or extend the trim tab chord with a temporary tab, which ever is more convenient, and measure the effect. We used to use simple hanging scales like those to weight small fish to measure stick forces at repeatable flight conditions. Baseline the forces at the desired landing configuration, weight, and CG location first. Make the tab mods and analyze the results. If there is no noticeable change then there may be some flow separation on the underside of the elevator as others have suggested that has contributed to the problem. Elevator seals and/or vortex generators at or forward of the elevator hinge line area might help.  I would not entertain the complexity of synchronizing trim motors. Too hard.

Once you find what works the best, be sure and test the rest of the trim envelope at various speeds and CG/wt conditions to ensure flying qualities overall are still ok.  Then construct a permanent change and verify via a retest of the same conditions. Then publish findings to all.

Tom



Sent from my iPad



On Feb 22, 2011, at 9:09 AM, " Dr. Andrew Elliott" <a.s.elliott(at)cox.net (a.s.elliott(at)cox.net)> wrote:



[quote]

Gang:

 

On my 601XL, the elevator trim tab is not effective enough to trim out all control forces on a full-flap final when the CG is in the front half of the allowed range.  Although the remaining elevator forces are light, I would like to be able to trim them away.  The trim tab is inset on one side of the elevator, and takes the entire width, minus about 20 mm on each end.  Servo is RAC

 

One option would be to add another trim tab to the other side of the elevator.  But to do that I would need some way to slave the two sides together.  Does anyone have an idea about how to do that electronically without very high cost, or perhaps some way already exists and I haven't found it?  (The elevator design doesn't allow for a simple mechanical connection.)

 

Another option, of course, would to be to increase the size of the trim tab, either making it full width (probably not too effective - delta area <10%), or extending it aft 20-25 mm (probably would work, but ugly), or both.  I might go that way, but thought I'd ask about the saving first.

 

Thanks,

Andy

 

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

Andy Elliott

N601GE/Z601XL/TD/Corvair

298 hrs since 11/08

 

   	  Quote: 	
		  



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[b]

40950(at)rv10.net
Guest

Posted: Tue Feb 22, 2011 7:39 pm Post subject: Trim tab slaving?

Dr Elliot,

Adjust / extend the throw or extend the trim tab chord with a temporary tab, which ever is more convenient, and measure the effect. We used to use simple hanging scales like those to weight small fish to measure stick forces at repeatable flight conditions. Baseline the forces at the desired landing configuration, weight, and CG location first. Make the tab mods and analyze the results. If there is no noticeable change then there may be some flow separation on the underside of the elevator as others have suggested that has contributed to the problem. Elevator seals and/or vortex generators at or forward of the elevator hinge line area might help.  I would not entertain the complexity of synchronizing trim motors. Too hard.

Once you find what works the best, be sure and test the rest of the trim envelope at various speeds and CG/wt conditions to ensure flying qualities overall are still ok.  Then construct a permanent change and verify via a retest of the same conditions. Then publish findings to all.

Tom



On Feb 22, 2011, at 9:09 AM, " Dr. Andrew Elliott" <a.s.elliott(at)cox.net (a.s.elliott(at)cox.net)> wrote:



[quote]

Gang:

 

On my 601XL, the elevator trim tab is not effective enough to trim out all control forces on a full-flap final when the CG is in the front half of the allowed range.  Although the remaining elevator forces are light, I would like to be able to trim them away.  The trim tab is inset on one side of the elevator, and takes the entire width, minus about 20 mm on each end.  Servo is RAC

 

One option would be to add another trim tab to the other side of the elevator.  But to do that I would need some way to slave the two sides together.  Does anyone have an idea about how to do that electronically without very high cost, or perhaps some way already exists and I haven't found it?  (The elevator design doesn't allow for a simple mechanical connection.)

 

Another option, of course, would to be to increase the size of the trim tab, either making it full width (probably not too effective - delta area <10%), or extending it aft 20-25 mm (probably would work, but ugly), or both.  I might go that way, but thought I'd ask about the saving first.

 

Thanks,

Andy

 

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

Andy Elliott

N601GE/Z601XL/TD/Corvair

298 hrs since 11/08

 

   	  Quote: 	
		  



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[b]

bakerocb

Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

Posted: Wed Feb 23, 2011 4:27 am Post subject: Trim tab slaving?

2/23/2011



Hello Andy, Is it possible to reduce the length of the lever arm between the 

pushrod end and the trim tab surface thereby gaining increased movement of 

the trim tab arc for each longitudinal movement of the pushrod?



'OC' Baker Says: "The best investment we can make is the time and effort to 

gather and understand knowledge."



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



Time: 07:13:04 AM PST US

From: " Dr. Andrew Elliott" <a.s.elliott(at)cox.net>

Subject: Trim tab slaving?



Gang:

On my 601XL, the elevator trim tab is not effective enough to trim out all

control forces on a full-flap final when the CG is in the front half of the

allowed range.  Although the remaining elevator forces are light, I would

like to be able to trim them away.  The trim tab is inset on one side of the

elevator, and takes the entire width, minus about 20 mm on each end.  Servo

is RAC

One option would be to add another trim tab to the other side of the

elevator.  But to do that I would need some way to slave the two sides

together.  Does anyone have an idea about how to do that electronically

without very high cost, or perhaps some way already exists and I haven't

found it?  (The elevator design doesn't allow for a simple mechanical

connection.)

Another option, of course, would to be to increase the size of the trim tab,

either making it full width (probably not too effective - delta area <10%),

or extending it aft 20-25 mm (probably would work, but ugly), or both.  I

might go that way, but thought I'd ask about the saving first.

Thanks,



Andy

aerobubba(at)earthlink.ne
Guest

Posted: Wed Feb 23, 2011 11:41 am Post subject: Trim tab slaving?

Hi Andy-



For what it's worth, I'd suggest there are a couple questions to answer prior to modifying your plane.  You may have already run these issues to ground, and if so please disregard the first portion of this note.  The first question is, is this trait common to the design?  If it is not a common issue, I would suggest verifying your ASI operation / calibration and CG calculations prior to making any changes.   



The other observation is to be aware of the effect of increased up trim authority on go around performance.  There is the possibility that using increased nose up pitch trim for a low power or power off gliding situation could lead to unexpectedly (startlingly?) high pitch up tendencies when go around power is applied. 



YMMV-



 	  Quote: 	
		  Time: 07:13:04 AM PST US

From: " Dr. Andrew Elliott" <a.s.elliott(at)cox.net>

Subject: Trim tab slaving?



Gang:

On my 601XL, the elevator trim tab is not effective enough to trim out all

control forces on a full-flap final when the CG is in the front half of the

allowed range.  Although the remaining elevator forces are light, I would

like to be able to trim them away.  The trim tab is inset on one side of the

elevator, and takes the entire width, minus about 20 mm on each end.  Servo

is RAC

One option would be to add another trim tab to the other side of the

elevator.  But to do that I would need some way to slave the two sides

together.  Does anyone have an idea about how to do that electronically

without very high cost, or perhaps some way already exists and I haven't

found it?  (The elevator design doesn't allow for a simple mechanical

connection.)

Another option, of course, would to be to increase the size of the trim tab,

either making it full width (probably not too effective - delta area <10%),

or extending it aft 20-25 mm (probably would work, but ugly), or both.  I

might go that way, but thought I'd ask about the saving first.

Thanks,



Andy

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



Andy Elliott



N601GE/Z601XL/TD/Corvair



298 hrs since 11/08


	




Glen Matejcek

email(at)jaredyates.com
Guest

Posted: Wed Feb 23, 2011 7:14 pm Post subject: Trim tab slaving?

Some airplanes also benefit from a little ballast in the baggage compartment.  Yours might be a candidate for 25 pounds of kitty litter, which can also come in handy if you really need to pee.

 On Wed, Feb 23, 2011 at 2:37 PM, Glen Matejcek <aerobubba(at)earthlink.net (aerobubba(at)earthlink.net)> wrote:

[quote] --> AeroElectric-List message posted by: Glen Matejcek <aerobubba(at)earthlink.net (aerobubba(at)earthlink.net)>

 Hi Andy-

 For what it's worth, I'd suggest there are a couple questions to answer prior to modifying your plane.  You may have already run these issues to ground, and if so please disregard the first portion of this note.  The first question is, is this trait common to the design?  If it is not a common issue, I would suggest verifying your ASI operation / calibration and CG calculations prior to making any changes.

 The other observation is to be aware of the effect of increased up trim authority on go around performance.  There is the possibility that using increased nose up pitch trim for a low power or power off gliding situation could lead to unexpectedly (startlingly?) high pitch up tendencies when go around power is applied.

 YMMV-

 >Time: 07:13:04 AM PST US

 >From: " Dr. Andrew Elliott" <a.s.elliott(at)cox.net (a.s.elliott(at)cox.net)>

 >Subject: Trim tab slaving?

 >

 >Gang:

 >

 >

 >On my 601XL, the elevator trim tab is not effective enough to trim out all

 >control forces on a full-flap final when the CG is in the front half of the

 >allowed range.  Although the remaining elevator forces are light, I would

 >like to be able to trim them away.  The trim tab is inset on one side of the

 >elevator, and takes the entire width, minus about 20 mm on each end.  Servo

 >is RAC

 >

 >

 >One option would be to add another trim tab to the other side of the

 >elevator.  But to do that I would need some way to slave the two sides

 >together.  Does anyone have an idea about how to do that electronically

 >without very high cost, or perhaps some way already exists and I haven't

 >found it?  (The elevator design doesn't allow for a simple mechanical

 >connection.)

 >

 >

 >Another option, of course, would to be to increase the size of the trim tab,

 >either making it full width (probably not too effective - delta area <10%),

 >or extending it aft 20-25 mm (probably would work, but ugly), or both.  I

 >might go that way, but thought I'd ask about the saving first.

 >

 >

 >Thanks,

 >

 >Andy

 >

 >

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

 >

 >Andy Elliott

 >

 >N601GE/Z601XL/TD/Corvair

 >

 >298 hrs since 11/08

 >

 >

 Glen Matejcek

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