The Restoration of N2120E

[Richard Murray]

How can you glue to a stringer and meet the STC? I am sewing an envelope and the seam will follow the stringer. I will glue to the lower longerons with the top envelope and a final a piece covering the bottom. I split the top piece just in front of the fin, sewed a piece on either side to cover the fin, and am planning to glue to the fin so I have structure under each glued seam.

[MikeB]

Factory fabric when the Champs were first built was wrapped around the top stringer. Having said that, Poly-Fiber for one says the fabric must be wrapped around a structual member (tube) but I don't know if that really trumps original design (for lack of a better term).

I've used envelopes on most of the Champs I've covered with another piece on the bottom but you'll still have a seam somewhere usually up the top of the cabin. Don Eide used the blanket method with a sewn seam over the top stringer which is covered with a tape and it hardly shows. My first Champ cover job used a complete envelope for the fuselage with a sewn in bottom. There were four sewn seam: one on each side of the bottom and one on each side along the upper stringers. I had my doubts about keeping them all straight but they came out pretty well.

Mike

[Nathan K. Hammond]

Factory trumps STC. Since Aeronca glued and/or stitched to the stringers, I can glue to the stringers with modern covering systems.

At least that's how I read it.

nkh

[Richard Murray]

Did not know that Nathan. Please help me understand this because the PolyFiber manual specifically prohibits gluing to stringers. I can understand if you use the factory adhesive or an approved substitute you could follow the factory procedure and if that was to glue to a stringer then you could too. However if the STC specifically prohibits a glued seam on a stringer then would you not be failing to comply with the STC and ultimately in violation of the FARs?

Richard

[Nathan K. Hammond]

Richard, I missed your last post, sorry.

The manual comes off straight forward so the unknowing wont have safety of flight issues. But if you call and talk with Jon or Brian at PolyFiber, they will tell you if a manufacture covered an airplane different to how the manual states; it is acceptable to follow the manufactures guide lines while using the PolyFiber STC. An Aeronca fuselage is a perfect example of this. Another would be some Piper aircraft no having tapes applied to stringers.

When I started teaching the SportAir Fabric classes, Jon pointed out this example, and later I called Brian to ask the same question. He pointed to page 1 of the manual, last sentence of Basic rule #5: "if in doubt refer to the original aircraft maintenance manual."

Now that's still vague, especially when put in context with the rest of #5, but it does set a precedence.
Best thing to do is call the PolyFiber tech line and see if they can point you to solid evidence for your IA.

nkh

[MikeB]

I think "Dip" Davis said the same thing to me regarding Superflite. I believe his exact words were that you could cover a Champ (fuselage) using three different pieces of material but as I said I've only used the envelope method for the fuselages. Works OK but you'll have a seam somewhere.
Mike

[Nathan K. Hammond]

Sorry for the crappy photos, I can't remember my good camera and end up using my phone.

The "D" window frames are shot.







nkh

[Nathan K. Hammond]

I picked up a couple cheap engine stands from Harbor Freight to use as a fuselage rotator. There is a slight problem though; the axel is on a 10* incline and they're too short for my liking. An easy fix would have been to cut and reweld, but didn't have a welder at the time. So here is my fix.







And then some cheap angle from lowes to finish the tail.





nkh

[joea]

Looking better!

[MikeB]

Nathan,
Glad to see you're back working on it. Keep posting pictures....we always learn something. How is the fuselage tubing...rust wise??

80 degrees in Texas today and my plane is snowed in at home . I looked at a 'in progress' L16A today. Looks like it's going to be a nice one when it's finished. Also, looked at a Champ a few weeks ago that's being restored. If they do as nice job on the Champ as they did on a Chief they rebuilt it's going to be a beauty when it's done. Great to see folks are restoring these old timers (the airplanes not the guys working on them).

Mike

[Dennis]

I used a constant velocity joint on the engine stand attached to the front fuselage. At the rear, I used my three legged aircraft engine stand with two small pillar blocks mounted horizontally on top with a shaft and a flat plate bolted to the tail mount on the fuselage. This way the fuselage is never in a bind and it will rotate freely about 300 degrees.

Dennis

[Richard Murray]

Nathan,

Thanks for the insight. I'd much rather use three pieces vs trying to get an envelope to fit. I will double check with PolyFiber and my IA to be sure everyone is onboard.

At the IA/Maintenance Seminar I attended this week the Lear Chemical Spokesman touted that AFC-50 was suitable to substitute for linseed oil in the tubes. We're still talking about that.

Richard

[Nathan K. Hammond]

For the most part, the fuselage is straight and clean, but there are some areas of concern. They had drain grommets in the belly, but they were placed incorrectly allowing water to pool near the tail.







There is also evidence of two previous repairs not mentioned in the logs. A lower longeron has a 12" section replaced, and both lower longerons and tail post have been replaced.





Here's what the mud-daubers left in the spar carry through's. An electric drill with a piece of welding rod chucked up helped clean out that mess.



I also had to pickup some stringer stock from ACSpruce. It was cheaper to drive down than have them crate and ship it north.




nkh

[joea]

Nathan,

You need to get that airframe to a sand-blast facility and get it cleaned up so you can really visually inspect the tubing.

For those who have never done this, get the paint knocked off then take a automatic center punch and start a punching. You can immediately tell the difference between "good metal" and rusty stuff...

Joe A

[Richard Murray]

Nathan,
Looks like you're back at it full time.

Joe,
Thanks for the advice. I have some repairs to make and the automatic center punch will let me chech the rest of the tubes while I have the fabric off.

Richard