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Old Nov 04, 2012, 07:43 AM
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United States, CA, Hidden Valley Lake
Joined Aug 2002
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How much trim is to much?

When you put a new plane in the air and get it trimmed out,
how much trim do you allow before you go in and mechanically
change the linkage?
Keeping in mind that changing it will require re-trimming the next flight.

I put a WM Mach II in the air yesterday and have about 20 clicks of aileron trim.
Trying to decide if it's worth adjusting to try to get closer to -0-.

Thanks for your opinions,
KW_Counter
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Old Nov 04, 2012, 08:49 AM
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1320fastback's Avatar
USA, CA, Oceanside
Joined Jul 2008
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I always try to mechanically trim mine after flying for first time.

You want the servo to be centered when in trim so you have equal throw in each direction.
If you have 20 clicks one way then the servo is now held off center and you that much less total throw in the same direction.

I am happy if I can get it to less than 5 clicks.
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Old Nov 04, 2012, 09:41 AM
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United States, NY, Eldred
Joined Jun 2012
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I agree with 1320 FASTBACK, you always want as little trim as possible. Most manuals I've ever read even say the same thing, which is to adjust after the first flight. Also, that is pretty much the purpose of the maiden. Take the plane up, trim it out. Make sure it flies well. Bring it down and make any needed adjustments and check for and looseness, play etc.
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Old Nov 04, 2012, 04:38 PM
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tacx's Avatar
United States, MI, Macomb
Joined Apr 2009
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The problem with to much trim is that you are changing your servos center position. If you go to far you can over extend your servos travel when you are flying.

One to five clicks OK. Any more than that and you should readjust mechanically to get your trim indicator back to zero.
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Old Nov 05, 2012, 01:40 AM
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Quote:
Originally Posted by tacx View Post
The problem with to much trim is that you are changing your servos center position. If you go to far you can over extend your servos travel when you are flying.
.
Not true. Your AFR/ATF function will limit the travel of your servo, regardless of where your trim is.

Don't lose sleep worrying about whether you should mechanically adjust your pushrods or not. Some do. Enjoy the perks of a computer radio. Other than adding more expo in one direction or running out of trim (which would then make it obvious that you should worry about it), as long as you like the way it flies - don't worry about it.

Kurt
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Old Nov 05, 2012, 04:11 AM
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Denver, CO
Joined Dec 2005
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If you have to much trim, its often a sign that something is wrong. I take a look at it on the ground to see where the control surface is. If its hanging out in the wind, something is probably not built straight, or thrust line is wrong, or CG is off, or could be many other things.
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Old Nov 06, 2012, 07:46 AM
EIEIEIO Classic is dway ta go!
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Northeast Pa. .Heyna or No?
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Take the time to figure out what is causing the 20 clicks of travel.
* Did you have the surfaces flush with the wing panel with the radio trims set at zero?
If so then there is a problem with the wing...more than likely.
* Is it an ARF or a stick-built kit ?
You want to mechanically correct the 20 clicks of trim as some others have stated. The pushrod to servo arm geometry is now off plus the servos now have limited travel in one direction because of all of the trim.
Take a measurement of where the surfaces are at now in relation to the wing panel and then reset your trims to zero. Screw or unscrew the linkage or clevis to set the control surface back to where it was on the 20 click setting.
Now go fly the plane as the servos and linkage are now set properly.
Next is to look at the wing and find out where it is warped and if it can be fixed or maybe the lateral balance is way off and needs to be centered, etc... Have a veteran builder/flyer at the field look at it and they usually can spot the problem visually if it is warped or out of alignment. You are not going to get as much out of the plane flying around with the ailerons out that much.
Don't get into the habit of "just flying the plane" after you trim it. Always come back either at the field or at home and make the mechanical adjustments to the control surfaces so the servos&linkage are back to normal. Plus if it takes too much trim(like now), find out what is causing the problem and try and repair it.
When you move into faster and larger planes this plays a big part.
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Old Nov 06, 2012, 10:48 AM
EIEIEIO Classic is dway ta go!
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HA !
Just found out the OP is shining us on.
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Old Nov 07, 2012, 08:29 AM
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United States, CA, Hidden Valley Lake
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No, I am not shining anyone on.
I had a good idea what must be done but wanted to get input
from others on how they handle these situations.
Though I am not a beginner there are many out there who know much more than I do.
I like to learn from these people.

Yes, I also asked this question @ RC Universe.
There were those there that think only Beginners may use the Beginners forum.
And others that think a certain protocol, theirs, must be followed.

That post deteriorated into a shouting match with a threat from the moderator to shut it down.
I do hope there is more maturity here.

Thanks to all of you with helpful responses.

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Old Nov 07, 2012, 10:58 PM
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Quote:
Originally Posted by kbozarth View Post
Not true. Your AFR/ATF function will limit the travel of your servo, regardless of where your trim is.

Don't lose sleep worrying about whether you should mechanically adjust your pushrods or not. Some do. Enjoy the perks of a computer radio. Other than adding more expo in one direction or running out of trim (which would then make it obvious that you should worry about it), as long as you like the way it flies - don't worry about it.

Kurt
-1 Not really the way to set up am airplane.
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Old Nov 09, 2012, 02:28 AM
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Quote:
Originally Posted by Fokker DII View Post
-1 Not really the way to set up am airplane.
Please explain the benefits, assuming the plane few just fine when it landed? And please, don't add more "If statements".

And flying "just fine" means he had plenty of roll authority, didn't run out of trim, and still had equal roll rates (even though he had a prop spinning up front) and wasn't looking to "establish good habits."

Just the facts, ma'am.

Kurt
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