Aluminum Stringers

[chrisg]

I'm using aluminum stringers from aircraft spruce and I have a few questions:

At the rear of the fuselage the wooden stringers terminate by tucking behind the vertical tube (by the jack screw). The wood stringers are "notched" to make them fit better. What do people do with the aluminum stringers? I'm reluctant to notch them and have them rubbing against the tube like the wooden ones. I was thinking about using some 3/8" channel to make a little stringer bracket that would be welded to the tube (see photo...although, I would probably turn the channel around so it was on the backside of the stringer).

Any other tips or tricks with the aluminum stringers?

[Lownslow]

Mine have the original aluminum stringers. They are not notched, and they tuck in behind the vertical tube. Seems like this set-up was fine to me so I left it that way.

Lou S.

[chrisg]

When I try to tuck mine behind the tube, it puts a lot of pressure on the tube (deflecting the tube slightly) and the stringer twists some. I don't know how the dimensions of my stringers compare to your stock aluminum stringers - maybe bigger, or something.

[Lownslow]

Forgive my previous error. I was going off of memory and slipped up. The length of mine extend only to the rear of the vertical tube in length and they are notched out at end. They seem fine that way to me. There is some tension that pretty much holds it in place, but not distorted. Hope this helps.

Lou

[JohnW]

I don't mean to sound blunt, but you are using the "wrong stringers". What you want is the stringer blank Univair sells as their p/n 1231-157. One hundred fifty seven inches long and each for $21.87. This is the extrusion that Piper used, and it works perfectly not only with the installation problem you are detailing, but the original wooden stringer clips bend perfectly around the lower flanges of this stringer like they were MADE for it (du-uhhh), making it a perfect replacement for the wooden ones as well as renewing original [whacked up] aluminum ones. In fact, Piper did NOT change the "stringer holder on-ers" when they went away from the wooden stringer. Getting the right stuff will fix this problem in the most satisfactory manner. Ya live, ya learn (happens to the best of us...don't ask me how I know this to be true).

Some times it COSTS YOU when you try to save a few pennies.

[chrisg]

JohnW,
I don't mind blunt, as long as I get the information I'm after! This whole project is an exercise in information retrieval.

I wasn't trying to save money with these stringers, I just didn't know about the Univair stringers. Luckily the Aircraft Spruce stringers were very inexpensive, so I'm only out about about $15....that is a pretty cheap lesson!

Thanks!

[chrisg]

Does anyone happen to have a picture of the Univair stringers they can post here?

[Steve Pierce]

I just fitted up a set on a PA22/20 yesterday. I used the 1232-162 stringers from Univair. They are .890" tall and .380" wide. The original wood stringers we took out o our Tri-Pacer measured about 7/8" by about 3/8". The 1231 stringers John posted about are .508" tall and probably easier to work with. I did the same thing Piper did on the Super Cub and drilled the web and cut it out to form it behind the tube. The Clipper has a 3/8" channel welded at the back to hold the stringer like the Pacer and Tri-Pacer have at the front. If you buy the material from Univair get 3 sections of the 1232-162, have them cut two in half and one at 82" and 80". That will cut down on shipping long stuff and fit one Tri-Pacer will little waste. I'm thinking about bending these more like Piper did where they don't touch the inside of the tube.

Stringers

PA16
Center Belly Stringer 109"
Top Center 66.5"
Top Left 63.5"
Top Rt. 63.5"
Bottom Left 57.5"
Bottom Rt. 83.5"


PA22
Top Rt. 71"
Top Left 72"
Bottom Rt. 25" & 57"
Bottom Left 75"
Belly 76" x2
3 sections of 1232-162 will do one airplane.

1232-120 is 120" long
1232-162 is 162" long

[chrisg]

these are great photos...thanks!!

[JimCNY]

Can a broken wood stringer be replaced without removing the fabric?