Does anyone have thoughts on "squaring the plane" with elevator servos inside the stabs?

How do I setup the elevators on my EF, the servos are inside so I don't have access to the servo screws to lay the straight edge across. I thought my setup was good the way I did it but then after reading the above I checked it and sure enough the two elevators were spot on at full up, a tad off at neutral, and way off at full down! I just finished both wings using the above method and it worked great.

Originally Posted by djmoose

Does anyone have thoughts on "squaring the plane" with elevator servos inside the stabs?

Exactly! Sorry, did not see your post before I sent mine.

Originally Posted by Supreme6

Exactly! Sorry, did not see your post before I sent mine.

No prob man!!

I have a write up from a few years ago describing how to do it, but it is a few years old and was much easier on the aileron than the stab. I will try and find it and post it tomorrow. I am out on business tonight.

Originally Posted by djmoose

Does anyone have thoughts on "squaring the plane" with elevator servos inside the stabs?

This process is more tedious and requires the usage of the servo protractors I posted to measure the degrees of rotatation.

Step 1 & 2 are done with the plane turned off. It is mechanical alignment only

Step 1 Make sure servo horn from hinge line is same distance - What is important is the distance of the control arm pivot point from the hinge line. This determines the lever arm length which will determine how far the servo arm rotates for a given amount of surface throw. Here is a picture of how one person measured it:

https://www.flyinggiants.com/forums/s...3&postcount=55

Once they are the same distance from the hinge line you know that each servo will move the same amount of degrees for a given amount of movement in the surface. This is your first step in getting the geometry right.

Step 2 Match Servo Rotation - Using the servo protractor to make sure that each servo moves the same number of degrees when you deflect the surface up and when you deflect it down. The way I have done this is to hook up my linkages without the servo powered, and use one of the protractors so that when I move the surface with my hand up 1.5" and down 1.5" the servo arm moves the same number of degrees in both directions. You change it by adjusting the length of the linkage. This is done for both stabs. If the number of degrees of rotation from nuetral to up and from nuetral to down are the same for both stabs then you know they are mechanically they are the same and are at the same point in their rotation. For a 1.5" deflection in the surface if one stab servo moves +-30 degrees and the other stab moves +-32 degrees then your control horns are not exactly the same. They may be offset slightly from the hinge line or one may be slightly taller. The taller control horn would cause more servo rotation.

Step 3 Electronically match servos - From this point on you do not want to adjust any of the linkages just do it electronically. With the stabs I like to do this with them on the plane standing about 10 feet behind the plane and have somebody hold the tail up so I can visually look at the center of the stab (on a tapered stab you can see both the top and bottom). I set the centers with the subtrim so they are at nuetral and match each other. I do the same for up elevator just with the tail held lower and setting the endpoint. Down elevator hold the tail high and set the other endpoint. The human eye is incredibly accurate at detecting when things are not in alignment.


Once this is done, they are matched at the endpoints and will match throughout the range of travel if you did step 1 and 2. If you skip step one and 2 and just do 3, they will match at the center and endpoints but you may get binding or mismatched travel throughout the range of travel.

Wrek, I was asking about squaring up the stabs with the servo mounted inside.

So you're saying there is no "squaring" secret for inside-mounted stab servos.

Also, there is no easy way to use a protractor on a servo that is mounted inside the stab. (which was the reason for my question)

I was able to square mine up by removing the stabs and sliding them on the tube. Then I taped the elevators at neutral and adjusted the linkages until both arms were at 90 degrees (as close as I could tell with my eyes). Then I made sure I could look through both servo arms from the side and the holes all lined up. I believe this does the same thing just not as precise as using a straight edge. When I taped mine the two arms were way off until I adjusted my linkages.

Another member sent me a pic of deflection meters that he made. I know they don't show you how many degrees the servo itself is moving but if the linkages are the same on both you should be able to set the throws accurately with it. Correct me if I am wrong.

Originally Posted by djmoose

Wrek, I was asking about squaring up the stabs with the servo mounted inside.

So you're saying there is no "squaring" secret for inside-mounted stab servos.

Also, there is no easy way to use a protractor on a servo that is mounted inside the stab. (which was the reason for my question)

I was thinking you could printout the protractors and cut them in such a way that they could slide down into stab on the servo, but now that I think about it probably not.

The only other way would be to try and use a sheet of paper, hold it next to the arm and mark its position at neutral and both ends and measure them to see if the arm moves the same amount each direction. This would be like using the protractor method. (EDITED Look at the post below for another method that may work better. I have not tried it but the straight edge between the two arms parallel to the tube may be best way to do it)

In the stab servos are more difficult and the protractor method is harder than the square method, so you have the worst of both worlds.

Just keep at it, you can get it figured out. The main thing is getting the geometry right.

If you just can't get the geometry right, and have a JR or spektrum radio with the balance feature you can use that to match them electronically at 5 points rather than 3. If you have a Futaba you can use a point mix to match them with a multi-point mix. I have a Futaba and have done this on a push pull rudder, when I just couldn't get them correct. I believe the rudder horn was glued in slightly offset.

Originally Posted by Supreme6

I was able to square mine up by removing the stabs and sliding them on the tube. Then I taped the elevators at neutral and adjusted the linkages until both arms were at 90 degrees (as close as I could tell with my eyes). Then I made sure I could look through both servo arms from the side and the holes all lined up. I believe this does the same thing just not as precise as using a straight edge. When I taped mine the two arms were way off until I adjusted my linkages.

Another member sent me a pic of deflection meters that he made. I know they don't show you how many degrees the servo itself is moving but if the linkages are the same on both you should be able to set the throws accurately with it. Correct me if I am wrong.

Putting them on the tube and eyeballing the arm to make sure they are in alignment should work pretty good. You could even run a straight edge from arm to arm touching the outside edge of the arms and see if the straight edge is parallel to the stab tube. If the arms are not in alignment the the straight edge would be skewed compared to the tube. (This may actually work better than what I was describing above using a piece of paper to measure the movement)

I have found there is enough play or variance in using deflection meters that the old eyeball is better at matching one to the other if you stand behind the plane about 10ft. (as described above) I use a throw meter to set one stab to the throws I want, then just use my eye to match the other one.

Just keep at it sometimes you have to be creative to figure it out, but knowing what you want the outcome to be is half the battle.

Let me know how it works out.

Wreck, thanks for all your help. I know it is a pain to type out step by step directions for the new guys. I have everything dialed in now and it looks great!

Originally Posted by Supreme6

Wreck, thanks for all your help. I know it is a pain to type out step by step directions for the new guys. I have everything dialed in now and it looks great!

Glad to hear it. Just spread the knowledge, I have had lots of people spend lots of time with me teaching me this stuff. Before long you will be the setup Guru at your club.

Great info
thanks guys

I used a H9 angle pro to match my elevators and ailerons. It takes some work to ensure you don't get false readings from either zeroing out the neutral or setting throws, since the meter weighs down the surface. I do everything mechanically first, then do minor adjustments in the radio menus. For some reason I can never get a 100% satisfaction from what I do and usually do it 2 or 3 times to be happy.

Great idea for a blog by the way rritchey!

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