Longeron to tail post cut?
- Thread starter General
- Start date
piper has a good print of it, and where they designed the tubes to go. heres a start. https://www.supercubproject.com/drawings/pdfs/A3290654.pdf
Last edited:
Longeron is notched then heat formed at rear most to provide a nice rounded transition into the tailpost. Whenever welding back there, add weld or move the diagonal tube to touch the lower longeron, some originals the tailpost will crack. There is also a liner inserted into the longeron, but some folks splice in a thicker tube for the last bay instead. Theory on that is corrosion when it does get in there wont have a nice tight area to spread between the two tubes slipped over each other. Piper drawing as referenced above lines it all out pretty well.
Steve Pierce
BENEFACTOR
Graham, TX
Please post a DETAILED picture of tail post junction
I'm not lazy, and have spent a lot of time trying to see a clear diagram or picture of the exact position of the tail post welds to longerons, specifically, the joining and position or the diagonals that join above the lower longerons. Some pix show this area, but old glue, fabric shreds and...
www.supercub.org
I’ve been taking photos throughout the process of repairing it. Everything that existed from before was a deviation from plans or completely rotted so was not a great reference for me. The drawings post above are a huge help as it has dimensions included. I’ve see a lot of finished and painted tails, but not much of those in process.
Attachments
Very helpful for me, thanks!
but not much of those in process=be interesting to see a bigger picture of what your doing??? if you search x or box tail brace a few more pictures might come up.
I'm in the hangar today, will upload some photos and a narrative. The TLDR version is I broke a longeron subsequent to corrosion weakening the tail section and I am splicing in replacement tubing and tailpost, doing fabric repair, etc. to avoid a larger initiative around full longeron replacement and fuselage recover that I had planned to do in ~2026'ish.
skywagon8a
MEMBER
SE Mass MA6
General,
Take note of the differences between your drawing in post #1, drawing 20642 https://www.supercubproject.com/drawings/pdfs/A3290654.pdf and the pictures Steve links in post #4. Particularly the pictures in Steve's link's post #11. Your drawing in #1 above is the way it should be. All tubes which make up a cluster are supposed to have their centerlines intersect at the center of the cluster for structural purposes. Look at Steve's picture with the broken tail post. The tubes are not positioned correctly which allowed the loads to generate bending moments. Bingo...broken tubing. The diagonal tube is not correctly located.
Take note of the differences between your drawing in post #1, drawing 20642 https://www.supercubproject.com/drawings/pdfs/A3290654.pdf and the pictures Steve links in post #4. Particularly the pictures in Steve's link's post #11. Your drawing in #1 above is the way it should be. All tubes which make up a cluster are supposed to have their centerlines intersect at the center of the cluster for structural purposes. Look at Steve's picture with the broken tail post. The tubes are not positioned correctly which allowed the loads to generate bending moments. Bingo...broken tubing. The diagonal tube is not correctly located.
Yeah, I've been tracking. The cluster will be welded properly per the first drawing. I was in a webcast where Steve covered the tail post cluster and what happens when they are not connected. My drawing ( post 1) is from the plans from 1940. There were changes made in 1944 that violated some best practices and plans that helped contribute to the corrosion and breaks, cracks, etc. Lots of fun figuring this out and fixing it correctly.
skywagon8a
MEMBER
SE Mass MA6
Compare these two pictures with your drawing in post #1. Neither picture is correct. The upper one is obviously worse. Your repair is better, but still not correct. That break is caused by tailwheel loads, particularly if there is a shimmy issue. I suggest you place a piece of heavy walled tube 4 or 5" up inside the tail post To reinforce that cluster. This for the same purpose which Piper places a liner tube in the two longerons. That corner of the fuselage is weak.
You can’t see it in the photo of course, but there is a sleeve in the tail post that goes from the base of the cluster to the cluster above the splice. Same for the longerons - from the cluster and past the splice per AC 83.13.Compare these two pictures with your drawing in post #1. Neither picture is correct. The upper one is obviously worse. Your repair is better, but still not correct. That break is caused by tailwheel loads, particularly if there is a shimmy issue. I suggest you place a piece of heavy walled tube 4 or 5" up inside the tail post To reinforce that cluster. This for the same purpose which Piper places a liner tube in the two longerons. That corner of the fuselage is weak.
It’s a trade off on this repair. I’m planning to recover/restomod the frame in a few years and will be replacing the lower longerons and make several other changes before paining the frame. My shop and hangar are not finished yet for that effort.
skywagon8a
MEMBER
SE Mass MA6
What is the condition of the rest of the longerons? That's a big job. Unless there are serious issues, what you're doing now should be sufficient.
Supercubrancher
PATRON
NE
So, is the drawing in post #1 correct? The brace tubes are welded to the longerons not the tail post ?
