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SB 00067 Complete, Some Notes

Tacco

Well Known Member
1. I completed the mod solo with no problems. Just took time.
2. Be sure to tape the fuselage in the vicinity of the stabilator leading edge to avoid scratches.
3. I used two adjustable sawhorses and some closed cell flexible packing foam pieces to support the stabilator and to shim the stabilator to precisely align the mounting brackets and bearings.
4. A couple of sacrificial AN4 bolts with the threads removed and shaped into a bullet are helpful when reinstalling and to temporally mount the stabilator for balancing.
5. Remove the trim motor tray and apparatus. I just let mine hang on the cable off to the side. You might be able to work around it if left attached to the bulkhead, but why suffer the aggravation.
6. Upon initial removal, note the position of the PITA (MIL SPEC term) washers you used in original assembly. These are the glued washers, thick and thin, used to space the stabilator and ensure no end play. They will fall off! Fortunately, I also wrote a note in the plans as to which ones I used and where.
7. I didn’t weigh the kit before assembly. Should have in order to “ballpark” the amount of weight I’d eventually remove from the counterbalance weights. Account for the long bolts.
8. Balance the stabilator, it’s just not that hard and lets you precisely determine the amount of weight to remove from the weights. Follow the KIA. FOLLOW THE KIA.
9. Don’t forget to reinstall the trim tray and REST the actuator arm on the bolt per the KIA. It won't work if the arm is connected. The weight of the arm is not insignificant – 3 oz by my measurements.
10. I drilled three 3/8 holes in the lead counterbalance weight to achieve the reduction indicated by the procedure in the KIA. I drilled out the existing/unused bolt hole and one above and below that area. On the last one, I was carefully weighing the shavings until I achieved the desired reduction. The third hole did not extend all the way through before I got there.
11. One head scratcher. Checking the final balance, I found the stabilator to hold position as long as the trim arm rod end was perfectly positioned on top of the retaining bolt. Slightly off that position the stabilator would slowly settle forward or aft. In other words, the rod end would “push” the stabilator if off center. I reposition the rod end with the trim motor to confirm the stabilator balanced in any position as long as it was top dead center on the bolt.
12. Lastly, go slow and gentle when positioning the stabilator when reinstalling. Seemed easier than when I did it originally. Didn’t knock of any washers!
13. For those who think installing the mod with the stabilator attached in order to avoid the hassle and PITA washers, think again. It would take at least three trips into “the hole” and you’d need a helper to remove/reinstall the counterweight bar from the stabilator spar. For the really adventurous among you who might think you can perform the entire mod (fitting the braces and reducing the weights) from inside the tail cone, seek counseling. At the very least, file a flight plan so your loved ones know where to find you. :D
 
Nice PIREP Tacco! This will be helpful when we do 3 ships here. From your note number 12, it appears you did not do SL00068 to install the shims and not have to fight the washers? Any particular reason why not?
 
Nice PIREP Tacco! This will be helpful when we do 3 ships here. From your note number 12, it appears you did not do SL00068 to install the shims and not have to fight the washers? Any particular reason why not?

Hi Tony. I considered it. Given the number of times I'm going to remove the stabilator, it seemed like a lot of reconstruction for the convenience. So, I decided not to do it.

That said, there is one reason it might be a good thing to do. It's just my unexpert opinion but here goes. Using the current design (PITA washers), you are never going to get a flush installation, bearing to bracket. There will always be a gap of at least half the thickness of a 416L washer. When you torque down the AN4 pivot bolt, it's going to pinch the bracket. Just a seat-of-the-pants opinion, but that pre-load might lead to a crack later down the road. I'm assuming the new design results in a flush installation.

This area will get careful inspection during my condition inspections for that reason.
 
Tony, did you aim for neutral balance? I found that spec in the 12is KIA but not for the classic.
 
I did mine today and Steve’s write up is spot on. I did a few things slightly different.

#3 my saw horses were not adjustable so I lifted the nose of the plane and it lowered the tail to the height of my saw horses. Same result.

#4 I used the old “short” counter weight bolts, AN3, easy in and out for temporary testing.

The weight of the kit minus the parts you remove, short AN3 bolts, nuts, washers, and rivet shafts was 66 grams.

I ordered the stabilizer hinge spacer kit but did not use it. I read that it solved the tedious spacer installation process. Instead I removed the stabilator the night before and re-glued the spacers in place using long set JB Weld. First clean the area with scotch bright, scuff the washers with 220 sandpaper, and clean the area with acetone, then glue, the washers will never move again.

I first weighed the servo pushrod by laying the clevis on a scale after the stabilator was removed. I added that weight plus the bolt, nut and washers, it was 87 grams. I created an 87 gram dummy weight using buck shot in a container and taped that in the same plane as the clevis hole. Next I hung the stabilator with counterweight from the ceiling using the hinge bolts. I used a fish scale to pull on the end of the counterweight to give an estimate of the amount I would need to remove. This technique worked well, I had to do an 8 gram adjustment on final install in the plane.

My weights were stock size, never trimmed, 2015 kit, painted tail surfaces. I removed ½” from the front of all 4 weights a total of 270 grams, the balance is perfect.
 
This is all helpful information, still haven't decided on shim kit install (all parts on order) by the time I get my parts you guys will have it all figured out for me , keep them coming.

Stan
 
I started today and found that when I disconnected the cables from the stab that is was in a really heavy nose down condition. I have a 2010 old model that obviously was never balanced, however I always noticed previously that when pre flighting the stab would stay in any position I put it and moved freely. I never noticed any in flight issues at all, so I'm wondering what benefit will be realized by balancing? I can understand removing an equal amount of weight to accommodate the kit but other than that I don't see the benefit, just wondering why they do it now and not back then.
 
Mine was not balanced when it was built. It was nose heavy when I removed the cables. It is balanced now per the latest KIA. I can’t tell the difference in flight characteristics or control feedback. It has to improve the aerodynamics now that the trim isn’t needed to overcome the out of balance.
One thing I do notice is getting in the plane the control stick moves forward naturally. Once the pushrod is connected the stabilator is tail heavy. I don’t quite understand that since it was in balance with the pushrod laying in place just not connected.
 
Maybe Scott or Greg could comment on what the benefits of balancing are? Does balancing reduce the flutter margin compared to a nose heavy stabilator with more mass. Why now with current kits and not the earlier ones. I don’t have an issue with balancing but would just like to understand the reason.
 
I did mine today, I removed 7.8 oz for a perfect balance...I'm interested to see if there's any notice able difference in flight, especially auto pilot altitude control, I always had a bit of oscillation.
 
Another data point (for whatever it's worth), I had to remove 28 grams at a point half way between the middle clamp bolt and the unused bolt hole at the end of the weights.

Measured downforce of the trim actuator arm = 88.6 grams.

Wing rack with a 2x10 clamped to the top and sticking out about 28" worked great to suspend the stabilator for balancing.
 
Flew today and noticed that my auto pilot holds altitude much better than with an unbalanced stabilizer. I was happily surprised. Didn't notice any difference when hand flying.
 
Any one crawled in the tail cone instead of removing the stabilator? Thinking I might try that approach. Give my kid a job to do, so I don’t have to break my back. Just curious if anyone has done this way. Thanks
 
Any one crawled in the tail cone instead of removing the stabilator? Thinking I might try that approach. Give my kid a job to do, so I don’t have to break my back. Just curious if anyone has done this way. Thanks

Michael
There have been quite a few posts from people who did crawl in the tail cone (or got someone else to) in this longer thread.

https://vansairforce.net/community/showthread.php?t=213575

Hope this helps.
John
 
Any one crawled in the tail cone instead of removing the stabilator? Thinking I might try that approach. Give my kid a job to do, so I don’t have to break my back. Just curious if anyone has done this way. Thanks

I did it. The two bolts holding the counterweight tube aren’t easy to remove, but with the correct combination of smaller tools, it is doable. (We did not remove the stabilator.) It’s not terrible, just be sure to use boards to support your weight in the empennage, and something appropriate under the tail to hold it up. I would not do this alone.
 

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Any one crawled in the tail cone instead of removing the stabilator? Thinking I might try that approach. Give my kid a job to do, so I don’t have to break my back. Just curious if anyone has done this way. Thanks

If you mean perform all of the work inside the tail cone without removing the counterbalance arm, I’ve not seen any posts regarding performing it using this method. Drilling the counterbalance arm inside the tail cone would be problematic for me. Like Tim posted, I’ve helped another builder do his by removing just the arm.
 
I did it. The two bolts holding the counterweight tube aren’t easy to remove, but with the correct combination of smaller tools, it is doable. (We did not remove the stabilator.) It’s not terrible, just be sure to use boards to support your weight in the empennage, and something appropriate under the tail to hold it up. I would not do this alone.

Ok great. I just plan on using the boards from last years SB 00053 crawl back and remove the counterweight and River the HS -01234’s on on the table outside and reinstall it. Thank you for the pics too.
 
Balancing it might be a PITA as the stabilator control cables need to be removed so there is no outside influence on the balance. I'd question how much work you are really saving. It's not terribly hard to pull the stab off IMO.

That being said, usually stuff like this arrives at the same amount of work, just with effort put into different tasks. I pulled my stab and also changed/loctited the bearings and had a great opportunity to inspect a lot of things that are normally not easy to see. Cheers!
 
The control stick because of its off center pivot loads the control to down elevator. With the cables connected you won’t be able to neutral balance the stabilator. The cables can be removed from the rear outside then go inside to remove the counter balance. You will need several in / out attempts to get the balance correct. In my opinion if you are at the point of removing the tail covers and cables you are only 15 minutes from having the whole assembly off the plane, especially if you have a helper.
 
The control stick because of its off center pivot loads the control to down elevator. With the cables connected you won’t be able to neutral balance the stabilator. The cables can be removed from the rear outside then go inside to remove the counter balance. You will need several in / out attempts to get the balance correct. In my opinion if you are at the point of removing the tail covers and cables you are only 15 minutes from having the whole assembly off the plane, especially if you have a helper.

I was planning on doing mine from inside but after reading a few reviews decided to do it from outside. I removed the assembly by myself and had a helper to balance and reinstall. The balancing was done by hanging it, not on the plane which was quick and easy.
 
It is not necessary to reinstall the stabilator to check its balance.
Instead, hang the stabilator with cord attached to the pivot bolts.
The calculated weight to remove was 448 grams. But the stabilator was
balanced after removing only 400g of lead. The total length of lead removed was 74mm.
The horizontal cord in the picture is holding the AST trim tab up.
The aft end of the AST PUSHROD is resting on bolt per plans page 11iS/U-11.
I will suspend the forward end of the AST PUSHROD with cord for more accurate balancing.
 

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The aft end of the AST PUSHROD is resting on bolt per plans page 11iS/U-11.
I will suspend the forward end of the AST PUSHROD with cord for more accurate balancing.

I suspended mine from the pivots off the plane for balancing also. I used a postal gram scale to weigh the end of the AST pushrod,then used tire weights of the same weight taped to the AST horn to simulate the AST pushrod.
 
So I'm still not understanding why balance is so critical. Any response from the Mothership That I might have missed??
 
Is it necessary?

It’s a LSA which thus closely conforms and is not just EAB.
Q1: can owner decide it’s not necessary? Van’s did not call it optional.
Q2: if yes then is necessary to go back to phase one?
 
Completed this SB this weekend. I DID NOT remove the stabilator since I am in annual inspection concurrently and already had the bulkhead cover removed. Instead I opted to remove the two bolts that secure the counterweight balance arm at the stabilator then shimmy into the tail section, twist and pull the counterweight/arm loose, perform service bulletin then shimmy in again to reinstall the counterweight.

Of course I had assistance of someone at the spar to insert the bolts while I was still in tail and able to twist arm as needed to align the bolt holes. Much easier, in my opinion, than complete removal of the stabilator.
 
sounds great....unless you're pushin 80, creaky and overweight. Basically, me no shimmy no more:)

I did not say I wasn't stiff and sore today....

60 years on 6'2" and 205# doesn't make the shimmy easy, but I didn't want to do all the work involved in removing and replacing the stabilator. I admit that at one point laying on my belly, reaching up to twist so my helper could find the bolt hole alignment I was wondering if the EMS would attempt to pull me out feet first and over the fuel tank or just opt to cut the -12 in half just behind the bulkhead.
 
Has anyone weighed the counter balance weight? I'm curious if it would be easier, while inside, to unbolt the weight first and then remove the arm. Do the work outside then reassemble in the reverse order. After it's reassembled, then drill through the extra hole in the lead weight to balance the stabilator.

Like some others I"m nearing 80 and have a volunteer RV12 builder to help with the inside work. I hope to start sometime during the 2nd week in August.
 
Not that heavy. Definitely easier to just grab it with the weight still attached.
 
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