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Sorry, another RFI about mk4

12 posts in this topic

Posted (edited)

I have his longitudal stringer that slip fits inside a stand-off, and it appears to be bare. Is this normal? Appears to be for every slip fit junction

D4616F18-0D50-4A3D-B220-8609391E7008.jpeg

Edited by Matthewtanner

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Posted

Push pull tube for the elevator maybe.

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Posted

hahaha...i should have known that, i guess it just caught my eye funny when i took the seat out and never really investigated...man, i must have been too close to the problem to solve it. Huge thanks for pointing out obvious stuff.

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Posted

Agree that is the elevator push/pull tube running thru the fuselage, however, NO that does not look "normal". The factory build manual calls for installation of a nylon or plastic bushing in the support standoffs to prevent metal on metal wear with the P/P tube and eliminate control system sloppiness. If your plane is missing the bushings, it is a safety issue that needs to be rectified prior to flying. No amount of grease will be an acceptable replacement for the lack of bushings.

Without checking the build manual I can't recall whether my Avid or KF builds required the elevator P/P tube be installed from front to back before installing FWF and covering. Unfortunately I think it might be the Avid. If so, it's going be a bit of a P.I.T.A. Don't think it will come out the horizontal stab opening but you might still be able to get it out to the rear through a small hole in the fabric. If the front of your P/P tube has an adjustable Heim rod end, you will have drill the rivet heads off to slip it thru the standoff bushing.

Pics show the 'high-tech' bushing material supplied with my Avid+ kit.

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CIMG5574.JPG

CIMG5575.JPG

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Posted

The problem with going out the back on an Avid is the push pull rod has a gradual bend at the front end.  Hard to pull that through the bearing points going out the back, and I would guess even harder going back in that way.  JImChuk

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Posted

Jim, I wasn't sure if that was the case with all of Avid and KF models. Seem to recall being able to do it with one of my builds but then my memory isn't what it used to be. Perhaps the best option would be to slit the bushing, force it apart to slip over the P/P tube then carefully press and glue new bushings in with the P/P tube in place. Might still need to cut and patch belly fabric to gain access.

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Posted

Kitfox might come out the back, I'm not sure.  It's a straight 1" aluminum tube though.  Like you said though, the rivets would get in the way unless they were drilled out.  JImChuk

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Posted

Well, hopefully the bushings are actually there and it won't be necessary. When I zoomed the pic however it looked to me like the P/P tube was off center in the standoff, indicating no (or badly worn) bushing. Might just be some photo distortion though. I did also see what looked like some galling on the tube so it all definitely warrants a closer look IMHO.

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Posted

His push pull tube guides look just like my Model C's guides. I believe the factory used pieces of polyethylene plastic for bushings and a soldering iron to melt the ends to keep the bushing from sliding out. My Model C is also missing some of the bushings. I was thinking about cutting chunks of shampoo bottle and slipping it in with the push pull tube in place.

My Bandit has the larger diameter guides like what dholly shows in his pictures. I didn't realize the bushings were made out of threaded PVC pipe though.

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Posted

Went out and checked. No bushings. So...now i’m Wondering if it’s not time to scrap the project and rebuild it like I want to. Considering there are already quite a few things that are “weird”....it doesn’t have the motor or wings I want...and it’s probably not even a mk4. Feeling pretty duped

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Posted (edited)

A split bushing can easily be made and installed using the method Doug showed with his one piece bushing.  This need not be a deal breaker just some of a build's little challenges along the way.  Take a deep breath, you only need to solve one issue at a time.  It is worrying to find these kinds of issues and you will probably do well to have another builder help you go thru the plane to see what other problems are lurking.

where are you located?  Maybe some one is close by and could have a look at it with you.

Edited by wypaul
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Posted

Oh man the community has been super good to me already, and i've had people from this forum and others come out to look at it, seems like each time we discover another "weird" thing. Im wondering if i could make a thin pvc bushing to slip in there with some proseal to hold it in along with flaring the ends. The questions is how do you get in there to work on it? I'm located in hazel, ky.

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