Tail Post

[15A]

Fixing a friends Champ. His tail post just above the tail spring doesn't look too good where it meets the lower longerons. It measures 1" OD. Anyone know the wall thickness? I'm replacing from the bottom to just below the 1st rudder hinge.

[joea]

Blueprint will give this information.

If you do not have one of that area (and you really should doing repairs like this) you might either get ahold of Brian Matz on this forum or go here: http://www.aeronca.com/dwgs/

Glad to see more people giving this area on the Aeronca's a good, in-depth inspection. The tailpost and longerons in the tail on our old airplanes need to be in good shape as they carry a lot of loads in flight, and are subject to rust. If you are not sure of them, replace them IMHO.

[Nathan K. Hammond]

.035

nkh

[15A]

Thanks!

I've been seaching the fuselage ass'y print, but tough to read.
.035 wall seems to be too thin to me. I might step it up a bit. Replacing maybe 6" and then a splice cap over it. I may slide a tube inside it with plug welds before I cap it. If I do, I need to keep both tubes the same thickness.

Joe

[Nathan K. Hammond]

I would stick with the original tubing, internally sleave it, and rosett weld it like you talked about. When you start beefing up the tubing size, it can induce stress on other area's not ment for load.

nkh

[15A]

Very good point! Thinking that this area is always a problem being so close to the grass and morning dew, I could stretch its life span. But it makes sense. Kind of like fixing a chain. If you replace the link with a stronger one, it'll just break somewhere else.

[Mikek]

.035

nkh

Aeronca.com

Basic Frame drawing shows:

Up to 3/4 in generally .035
up to 1 in .058 to .065 wall.

Drawing large takes time to load but then --------

Mike K

[David Johnson]

Nate is correct. Tailpost on Champ is 1" X .035. Citabria and Decathlon go to .049 but not a 7AC. David J.

[jerrymjr]

7-581-1 is 0.035 wall for 7AC through 7HC
7-1255-1 is .049 wall for 7ECA through 7KCAB
7-1411-1 is .049 wall for 8KCAB
7-1477-1 is .049 wall for 8GCBC

All of them are 4130, even the 7AC.

Off-field usage is the only enemy of the wall thickness, not airloads. Seen the Scout tail post take a beating on rough fields where the operator was spinning a 180 on the ground quickly several times per hour (read: glider tow). After many years that is.

So, normal people will be fine with stock wall thickness.

[15A]

Thanks Jerry

Good info!

[joea]

Jerry,

A question. If an airplane is used for aerobatics and more stress than normal is placed on the tail, then I assume that the load is placed on the longerons and not the tailpost?

In other words, the tailpost takes the stress on the ground and I assume the longerons in the air?

Thx,

Joe

[jerrymjr]

It really depends on the condidtion. As I recall, the tail post itself had large margins of safety (its been a while though). However, the rudder hinge bushing are attached to only the tail post. So, directional control loads are more serious when concerned about the attachment of the Rudder. I am suspecting (and I was not on the planet when they figured this out) that the wall thickness was for more localized 'beef' where the bushings are welded.
Otherwise the load distribution from the FAR's would put the post in bending and with a 1 inch diameter, you have a lot of inertia.

Edit: So, really the Tail is loaded in the air too. Longerons are, of course, more important though. Just think about it in a way of where the loads are applied. Either across the surface in some sort of aerodynamic distribution, or when someone prangs the tail wheel off the pavement.

[joea]

Thanks!