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Elevator trim setting

 
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billderou(at)yahoo.com
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PostPosted: Fri Dec 22, 2006 11:28 am    Post subject: Elevator trim setting Reply with quote

I went through this issue with Vans couple of months ago hoping for a plans revision or service bulletin but those folks seem to be busy in other areas - but I believe it to be important and want to share my findings.

I setup my elevator tabs per the instructions with both left and right 35 degrees below trail position when the servo is at the full up position. It is possible to meet this spec by making adjustments at the servo end of the cable.

During my first cross country I happened to look back at the tail and saw it was twisted. The elevator counter weight was above the horizontal stablizer on one side and below on the other. This bothered me more than a little as the forces would need to be high to cause this twist. I had not noticed this during my test flights because I now had luggage in the back and needed more down trim. After a lot of measurements I determined that the problem was I followed the instructions. If you begin with both elevator trim surfaces down at exactly 35 degrees the port side will never rise to trail position do to the cam action of the two actuators. Yet, the starboard will rise .75 inch above trail causing the twist.

At a minimum effort, all flying RV-10s should check for this condition. The fix is easy.

Highly recommend that you set the trim as follows:
1. Run the trim servo to full nose up.
2. Set the starboard trim tab trailing edge to 3 inches below elevator trailing edge.
3. Run the starboard trim tab to trail.
4. Set the port trim tab to trail.

Using these settings you will be able to trim out all pitch forces during final with the CG forward.

Bill DeRouchey
billderou(at)yahoo.com (billderou(at)yahoo.com)
N939SB, flying straight






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JHearnsberger



Joined: 22 Dec 2009
Posts: 31
Location: Springhill, LA

PostPosted: Mon Mar 28, 2011 7:39 pm    Post subject: Re: Elevator trim setting Reply with quote

I would like to know others opinions on this topic. I might be willing to set mine up this way.

Here's where I am at now, going by the plans. I set both trim tabs to 35 degrees down and when I bring them up to trail position, the right side is higher than the left side.

Please help me set my trim tabs up correctly.

Thanks,

Jake


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dmaib@me.com



Joined: 25 Apr 2006
Posts: 454
Location: New Smyrna Beach, Florida

PostPosted: Tue Mar 29, 2011 2:41 am    Post subject: Re: Elevator trim setting Reply with quote

I set mine up as Bill DeRouchey suggests in the post above yours. Mine works fine, with no problems after 350 hours of flying. I believe you may have more nose up trim authority this way. Others have set theirs up this way, and others have done it per the plans. You get to choose. Smile

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Lew Gallagher



Joined: 04 Jan 2008
Posts: 402
Location: Greenville , SC

PostPosted: Tue Mar 29, 2011 3:55 am    Post subject: Re: Elevator trim setting Reply with quote

Here is Bill's revised post, works great for us.
Later, - Lew


Date: Tue, 12 Feb 2008 10:55:08 -0800
From: billderou(at)yahoo.com
Subject: RE: RV10-List: alternate elevator trim settings or twisted tail
To: rv10-list(at)matronics.com

John-
Talking about nose up/down and elevator trim up/down could be causing the confusion since they move opposite to one another. Its also important to recognize when the positioning is created by the servo end travel or the trim trailing edge.
Another problem causing confusion is communicating in degrees. I do not believe that when Van says "-35 degrees" that this setting can be accurately repeated for X hundred aircraft, nor do I believe that Vans two factory RV-10's are set to -35 degrees. All of my settings and conclusions were drawn from doing the Trig and cutting out accurate triangles. This is also why I specified a vertical 3" of measurement to eliminate the errors.
So - lets take another run at it:
1. Run the trim servo to its end point where the right (starboard) elevator trim tab is full down. Full down is determined by the servo stopping and not the trim tab jamming.
2. Set the trim tab trailing edge to 3" vertically below and normal to the elevator trailing edge.
3. Get someone else to run the trim servo switch and have them slowly raise the right elevator trim tab until it exactly aligns with the elevator trailing edge. This is not the end of the servo run - it is determined by the trailing edges matching.
4. Set the left (port) elevator trim tab trailing edge to align with the elevator trailing edge.
Its very simple and much easier than working with the -35 degree spec for each surface.
I did communicate and was supported by Vans engineering on this subject. However, I believe the priority of the RV-12 got in the way of following this issue to its conclusion.
Bill


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coop85(at)verizon.net
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PostPosted: Tue Mar 29, 2011 5:54 am    Post subject: Elevator trim setting Reply with quote

Jake,
This is normal. I don't remember the exact details but I believe they are in the instructions. The system is designed so they both go down (giving you plenty of up elevator trim) but only one sides moves up using different throw geometry. I think the trick was to have one side faired to neutral when the other side is up.

I suspect someone with more recent experience can provide more specifics.

Marcus

do not archive
On Mar 28, 2011, at 11:39 PM, JHearnsberger wrote:

Quote:


I would like to know others opinions on this topic. I might be willing to set mine up this way.

Here's where I am at now, going by the plans. I set both trim tabs to 35 degrees down and when I bring them up to trail position, the right side is higher than the left side.

Please help me set my trim tabs up correctly.

Thanks,

Jake




Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=335375#335375












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Tim Olson



Joined: 25 Jan 2007
Posts: 2869

PostPosted: Tue Mar 29, 2011 6:22 am    Post subject: Elevator trim setting Reply with quote

I also used Bill's info and took some photos and did
a write-up here:
http://www.myrv10.com/N104CD/maintenance/20080622/index.html

In short, you want to get it so that both are neutral at the
same time, and you never have a situation where one is up and
the other is down. If you can do that, you're probably doing
just fine.

Tim

On 3/29/2011 6:55 AM, Lew Gallagher wrote:
Quote:


Here is Bill's revised post, works great for us.
Later, - Lew


Date: Tue, 12 Feb 2008 10:55:08 -0800
From: billderou(at)yahoo.com
Subject: RE: alternate elevator trim settings or twisted tail
To: rv10-list(at)matronics.com

John-
Talking about nose up/down and elevator trim up/down could be causing the confusion since they move opposite to one another. Its also important to recognize when the positioning is created by the servo end travel or the trim trailing edge.
Another problem causing confusion is communicating in degrees. I do not believe that when Van says "-35 degrees" that this setting can be accurately repeated for X hundred aircraft, nor do I believe that Vans two factory RV-10's are set to -35 degrees. All of my settings and conclusions were drawn from doing the Trig and cutting out accurate triangles. This is also why I specified a vertical 3" of measurement to eliminate the errors.
So - lets take another run at it:
1. Run the trim servo to its end point where the right (starboard) elevator trim tab is full down. Full down is determined by the servo stopping and not the trim tab jamming.
2. Set the trim tab trailing edge to 3" vertically below and normal to the elevator trailing edge.
3. Get someone else to run the trim servo switch and have them slowly raise the right elevator trim tab until it exactly aligns with the elevator trailing edge. This is not the end of the servo run - it is determined by the trailing edges matching.
4. Set the left (port) elevator trim tab trailing edge to align with the elevator trailing edge.
Its very simple and much easier than working with the -35 degree spec for each surface.
I did communicate and was supported by Vans engineering on this subject. However, I believe the priority of the RV-12 got in the way of following this issue to its conclusion.
Bill

--------
non-pilot
crazy about building
NOW OFICIALLY BUILDER #40549
Fly off completed !


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jcumins(at)jcis.net
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PostPosted: Tue Mar 29, 2011 11:41 am    Post subject: Elevator trim setting Reply with quote

I followed the write up on Tim's web site and it worked out perfect in trail
from neutral thru full up elevator the neutral and one tab on the down
elevator. Tim has a great how to write up on his site I would highly
recommend this to anyone.

--


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JHearnsberger



Joined: 22 Dec 2009
Posts: 31
Location: Springhill, LA

PostPosted: Wed Mar 30, 2011 5:24 pm    Post subject: Re: Elevator trim setting Reply with quote

Wow. That was easy. Thanks.

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Jake Hearnsberger
RV-10 Wings
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