Horizontal Stab Questions

[kitfoxrk]

When adjusting the horizontal stab, how critical is the 7/16" +/- 1/16" clearance between the stab and fuselage at the upper limit of travel. All of the posts I have seen have been about not being able to get that much clearance. I have the opposite problem. With the actuator arm fully extended, I get about 1" clearance. Is this a problem? And if so, is there a remedy?


My second question is on the attachment of the H-stab strut to the H-stab. Where the rod end attaches to the H-stab, the manual calls for a spacer - part#11501.000. Can anyone tell me the dimensions of this spacer and the material it is made of. I have not been able to locate them in my parts.


Thanks in advance for any help


Bob

[Frontier Fox]

Hey Bob
I can’t help you with your first question, haven’t gotten that far yet.

On the second question the spacers you are having trouble finding, part number 11501 is 1/4 inch long and appears to be the same material as the elevator bearings. I think it is referred to as a stand off.

Best of luck.

[jrevens]

Bob,

I’m sure they’re made of 4130 chrome moly steel tubing, probably reemed to the proper ID. You could order them from Kitfox... I’m sure they can’t be very expensive.

[aviator79]

Just a dummy check: You set that distance by rotating the trim motor shaft while the rod end is attached to the stab so that you screw the rod end in or out. You're at the max safe extension of the rod end, and still have 1" spacing? It does seem odd. You might email Kitfox with some pictures to make sure you're not missing something obvious. For that matter, you could post them here too so the experts can chime in.

[jiott]

Adjusting that clearance moves the whole range up or down; the range doesn't change. I was able to get pretty close to the clearance specified in the manual; however when I started flying it I found that I couldn't get near enough nose-up trim with full flaps deployed. So I adjusted that clearance to a larger value to move the range down so that when I ask for maximum nose-up trim the HS front tube is at the very bottom of the slots in the tail access panels. This is much better with full flaps but still requires some elevator back pressure on a full flaps landing approach. There is still plenty of nose-down trim for any situation.

[efwd]

Thanks Jim. Very helpful.

[Frontier Fox]

As long as we are talking about the Horizontal Stabilizer I have a few questions.

First has to do with the slider blocks. The instructions say to push the slider blocks in “snug”. How snug? If I raise the HS up by hand should it stay in that position or what? Is there some kind of lubricant applied on final assembly? I think it is about right but I want to be sure.

Second question has to do with the HS brace adjustment. I measured as instructed and need to shorted the left brace. It is 3/16” off. However the rod end is bottomed out on the threads and I can not shorted the total length. Also the right strut when I attach it, the rod end is also bottomed out. The only path that I see is to cut off about 1/8” from the left side threads so that the rod end does not bottom out.

Third question has to do with the trim actuator. On the upper end rod end there is a bushing part #10001.116 The bolt part #91036.000 will not go through the bushing. I assume the bushing will need to be reamed but there is no mention of doing this.
Hoping the elevator install goes well. At this point I just don’t see how six bolts are going to line up and have an elevator that moves as it should.

Thanks for your help

[Esser]

Hey Joe. You want those blocks quite snug. The idea is for the trim motor to move it, but you don’t want any side to side play.

I’m going back a ways but I think I reamed my trim actuator.

For the 3/16, I would just thread them down as far as you can and make sure they match. The elevator only bolts to the stab so it doesn’t matter if that’s out slightly, your elevator will still bolt on fine. You will still have a level stab due to the trim motor. It will just sit 3/16 higher which is quite minor in that location.

Someone else may have a different opinion but that’s what I would do.

[kmach]

The slider blocks will also wear, so make them snug, not binding , but as snug as you can .

You use LPS 1 on almost everything that needs lube, I use it on the post that the blocks slide on.

Lube the blocks and post before you decide that it is too tight.

[jiott]

Joe, the HS needs to be level with the wings and not forced into a dihedral with the struts. This will help with good flying trim hands-off. If you need to shorten the thread on one side I would do it as long as you still have at least the minimum required thread engagement.

[Frontier Fox]

I gave the HS problem a little more thought and decided to work the instructions in reverse. That is adjusting the right strut first, measuring and then checking the left side. The HS and vertical are now perpendicular within a knats hair. I will have to trim about an 1/8 “ off of the left side strut threaded end so that it slips into place without forcing it.
I also rigged the actuator today and tested it. It works just fine. No binding at all, so it’s good to go.
Tomorrow I will fit the left strut and put the elevator on.

Thank you all for your help