re assemble wing and strut 52 170B

[rollcloud]

George and Bruce,
I am re attaching my port wing. I have new hardware. Cannot find any reference to torque specification for these bolts. I can use a general reference but are there documents on the site that call out these torque values? and how do I search for them?

[Bruce Fenstermacher]

I've not looked but the only reference I could think to look in for guidance other than using general torque specs, would be the Cessna Service Manual, 100 series, '62 and prior. You can find that manual online here: http://mrwebman.com/aviation/cessna/manuals second from top - 150, 152, 172, 175, 180, 182 & 185 Pre 1963 Service Manual

[n2582d]

This is something you should be doing under the supervision of your A&P. C-172 manual calls for min. torque of 300 in./lbs. (fig. 4-1 1977 manual) which is next to nothing. Bolts are loaded in shear so shouldn't take a lot of torque. Pre '63 manual says to use the torque chart. (Paragraph 4-5, pg. 4-3).

[rollcloud]

Bruce
Tried to follow link. Returned object not found error

[Bruce Fenstermacher]

Bruce
Tried to follow link. Returned object not found error

Fixed, couldn't go right to the download link. You will have to click it once there.

The 172 manual Gary referenced will also be at this page somewhere.

Gary, I hadn't thought about the bolts in shear thus not needing the standard torque for the job at hand. Some times you have to have the job in sight to remember all the aspects.

[blueldr]

I don't believe the torque for the wing attach bolts in the eccentric bushings is of great importance since the bolts are only required to preclude rotation of the eccentric bushings. I would think enough torque to preclude rotation of the bushings would be sufficient.

[rollcloud]

The wing is on port side. Eccentric bushing turned so the thick side is up. Does anyone have a reference for the starting position of the eccentric bushings? I review some the of the posts but no one referenced a starting postion. My port wing was repaired many years ago. I have not idea if it was jigged during the repair. The new repair was done by Williams and it was placed in a jig. I know this wing is correct. The old eccentric position is probably not right. That is why I am trying to determine the starting position.

[Bruce Fenstermacher]

I believe we discussed this way back and I don't recall we found a reference for whether you should position the thick side in towards the cabin or the opposite. Either way the incidence in the wind would be neutral. Having the thick side up or down is on extreme or the other and not where you want to start.

In effect changing the eccentric sweeps the wing a minute amount. So what ever you do, do the same to the other so the wings are sweep symmetrically.

BTW you probably don't have the aileron and flap cables hooked up, But if you did like say your aircraft was flying and you just decided to adjust the rigging, you would want to loosen the cables first and then tighten them to tolerance again after your done because moving the eccentrics and thus sweeping the wing(s) tightens or loosens the cables.

[T. C. Downey]

BTW you probably don't have the aileron and flap cables hooked up, But if you did like say your aircraft was flying and you just decided to adjust the rigging, you would want to loosen the cables first and then tighten them to tolerance again after your done because moving the eccentrics and thus sweeping the wing(s) tightens or loosens the cables.

Turning the eccentrics does not sweep the wing. they only raise or lower rear spar, (3/16th inches) and will not effect the cable tension.
The 48 has no eccentric bushings and is adjusted by the rear upper end of the "Y" type strut.

[c170b53]

RC, rigging for me, is like cooking; a little here,a tweak there, see what you have, try to make it better in the end. I would try to be symmetrical at the start (check RH wing) and go from there. Ensure you loosen off the attach bolt and turn both bushings on the same wing at the same time, a little at a time, obviously in the same direction to avoid them binding up in the bores when you make your adjustments. As Tom mentioned the adjustment is rather small, as are the results, so don't sweat the small stuff, I'd hold off calling Joe Patroni in.
I'm sure you've checked that your ailerons have equal droop and your flaps are rigged symmetrically so you don't end up chasing your tail.
And I think Bruce's concept of sweep is up and down, not swept like a USAF fighter although I'd love to have a 170 swept wing 100kt. fighter just so I could say so.... ah maybe first a large scale model.....

[GAHorn]

One other thing... just because you alter/change one wing's eccentric bushings...does NOT mean you must to the opposite wing an identical amount. (I'm sure Bruce was just waking up or something when he wrote that.) The reason one adjusts one wing or the other is to cause the airplane to fly hands-off level. This means the two wings may NOT be the same at all.

[hilltop170]

If I remember correctly Del Lehmann adjusted mine both neutral and outboard after he re-jigged them. It's now an A model that flies hands-off in smooth air.

[Bruce Fenstermacher]

I meant exactly what I said. With the eccentric adjusted neutral inboard the wing is swept forward as far as it can go. The wing might be perpendicular to the center line of the fuselage at this point, I don't know. Adjusting the eccentric up or down pulls the rear wing spar towards the fuselage and since you are not adjusting the front spar, the wing must swept backwards relative to its position with the eccentric adjusted neutral inboard. Does not matter if you adjust up or down, the wing sweeps back. It will be swept back the farthest with the eccentric adjusted outboard neutral.

Of course Cessna designed this system to adjust the trailing edge of the wing thus changing it's angle of attack in relationship to the other wing. But the sweeping action also occurs.

You should also be able to see how moving the eccentrics also can relax or stretch the aileron and flap control cables.

Eccentric relationship.jpg

I also believe, that when you are splitting hairs, the best course of adjustment is to adjust one wing eccentric up and the other down an equal amount as when necessary. This course keeps the angle of attack of both wings the same in relation to the horizontal stabilizer. Unless of course you were trying to change that relationship to gain an extra knot of speed.

[T. C. Downey]

I see your point, but it has very negligible effect on cable tension. This is a good theory, but really doesn't matter in real life.

[c170b53]

Good observation Bruce, but I'm not sure the results would change much from one lateral extreme to the other. Then again maybe some experimentation is in order!