Elevator Binding

[FlyinFish N928M]

The bushing should just fit in-between the tabs on the elevator. You will have to file down one or both sides of the stab weldments, possibly in different amounts to get the correct tolerances. Nope, nothing NASA precise about it. You might want to clamp and weight down the stab down to a flat table or door to achieve straight and level. You can pull a fish line or heavy thread from end to end to find straight. then attempt to fit in the elevator as it should while paying attention to where the material should come out. Make this adjustment by finding the best average location across all 4 elevator tabs. This will be a slow process, but you will arrive in the end with a well fitted horizontal tail. During the manufacturing process welding typically deforms materials from stock dimensions.

[Oregonfox]

Thanks for the response. Yesterday I emailed KF and am waiting for a reply. In my first email to KF last week they suggested I check the straightness of the elevator and HS spars. We straightened the elevator spar and it helped a bit. The most obvious issue at the moment is watching the tabs move ever so slightly inward with only a bit of tightening of the bolt/nut even though there has been no shortening of the bushing length. All of the weldment/bronze bushing combinations are filed to be clear of the tabs. By your reply, I feel that I have done the proper things so far and not done damage.

It might be a manufacturing problem that you may consider bringing up with KF……If things are grossly out of alignment, video and photo document your issues and send them to John and Brandon at KF and let them formerly address before going to far any one direction.

[Pushboy]

Hi Oregonfox,

I had this exact same issue just a couple weeks ago. Free movement when the fasteners are not torqued, but at 25 there was restriction of movement - especially at the extremes of rotation.

The factory gave me the same advice about horizontal and elevator spar alignment. They also told me that the "free movement" should be the elevator wanting to fall down on its own. (More on that in a bit.) I did try the string down the center of the weldments and tabs but found that eyeing it was the best way to get close. As mentioned here before, I went with what seemed like the best average "close" colinear. Like you that was better but wasn't enough. Further advice from the factory was to focus on the actual range of the elevator - approx 40degrees up and 20 degrees down. Restricted movement above or below that - is out of range and thus not really worth the work. Lastly, they suggested to carefully remove powder coat on the weldments and/or tabs to get free movement. This did take quite a bit of time. Initially I had the horizontal/elevator mounted in the fuse for this -- however I found it far less time consuming to work these two parts off the fuse until I had something more workable. Also, it allowed me to turn the entire assembly upside down to assess "free movement" in the other direction. I carefully and meticulously watched and marked every hinge point during rotation to see where things were binding. With a small jeweler file and razor blade I removed powder coat in these areas. I did have to remove more powder coat than I initially wanted to or felt comfortable with -- however there is now a very small visible gap between the tab and the weldment... and more importantly free range/movement.

So a few thoughts for you to consider,

There is possibly more powder coat on each surface than anticipated/expected.
Also -- if I recall correctly the recommended range of torque for AN-3 is 20-25"lbs. The idea behind this attach point is that the bearing rotates within bronze sleeve and the bolt hold fast in one position on the tab. Possibly you could attempt your assembly with a torque of 20"lbs and see what the rotation restriction is with the bolts holding fast. If you have less or no restriction at 20 - then you can individually increase the torque to 25 at each hinge point and assess/correct the binding any offending points before moving on to the next one -- not all hinge points may be binding.

I hope that helps.

Incidentally I find if kinda funny that in the builder's tips section of the manual, it mentions not chasing every 1/64 or 128th of an inch or something to that effect cuz you will drive yourself crazy... -- yet the first chapter has you doing exactly that... I feel your pain -- I asked myself a couple times during that ordeal -- what am I doing here? Am I crazy? What have I gotten myself into?

Dave.

[jiott]

Don't worry, it's not all like this. The only other area you may get frustrated is getting free rotation on the brake/rudder pedal assembly; oh, and maybe the delrin block for the control stick assembly. In all these areas it is usually the powder coating causing the problems.

[Oregonfox]

A big thank you to everyone who replied to my questions regarding the Elevator/Stabilizer hinge issues. Yesterday, after a few weeks of experimenting, head scratching, emails to the factory, and research we met with success! Things most helpful steps were 1) bending the elevator spar in two different directions, 2) filing down the stabilizer weldments to fit between the elevator tabs, 3) sanding and polishing the steel bushings down to a fine shine and 4) using motorcycle oil (what we had on hand) to temporarily lightly lube the weldments.

The advice Pushboy gave regarding the factory recommendation to focus on the elevator range of 40 degrees up and 20 degrees down was the most helpful. That made a lot of sense since the range of motion in the elevator when installed will not need to go further.

I am new to forums and this is my first post. Thank you all for your patience and also your kind and thoughtful answers.

The first attatched photo is one of the simple platform we built to hold the elevator/Stab off the table while I put the ribs on next. I saw this on Swiftfox’s videos and would like to thank him for this good idea! The stuffed fox is a gift from my husband, given to me when the fuselage arrived. Her name is, “Kit.”

[Pushboy]

Hey Oregonfox—

Great to hear things worked out!

I know exactly how you feel. When I was in the midst of that, I was describing everything to a hangar neighbour who has built a few planes. He said “you should count that as a success.” I responded… “ not really, I still don’t have it working right…”

His answer was— “the real success was you got over your own fear of looking silly and asked the factory.”

Having never built a plane before… this rang pretty true.

Dave.


Sent from my iPhone using Tapatalk

[Oregonfox]

Yes, helping my husband build his RV-7 I learned he was not shy about using all the resources - forums, factory, internet, uTube…. Aviation is so much different than when I was flying 30 years ago. There are so many more excellent resources available to any level of pilot!