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longeron replacement

B

bryan albert

Registered User
I am rebuilding A PA-12 I just got the fuselage back from the sandblaster the lower longerons have been spliced a few times and they are pitted in a few places. I have decided to replace Both longerons. Is there any pitfalls to avoid when I cut the old ones out. Do i need to make some sort of jig to hold the frame so it does not move when longeron are removed. I was going to do one at a time and take lots of measurements before i cut is that the best way?. If anybody has any pointers pictures that would be greatly appreciated thanks for the help.
 
Just cause it is together now, does not mean it is correct:evil:

I would get a set of plans and do actual distances from plans, and build a jig as needed.
 
aktango58 said:
Just cause it is together now, does not mean it is correct:evil:

I would get a set of plans and do actual distances from plans,....
Click to expand...

don't do that!... the plans and the plane are not the same! ain't no 2 pa-12's that are the same!! (and don't even get a Blue print near a Maule..)

no jig needed, yes do one at a time... the only critical measurement is the stabilizer travel in relation to level flight/firewall.... and try to make bottom longerons strait. keep tail post & jack screw vertical too

i just use a cutoff wheel and cut out tube between clusters, then cut the piece in cluster open and grind/remove it from the inside of longeron pice left till I get to the cluster...

weld the inside corners FIRST to help keep from bending longerons as weld cools and contracts... you might also put blocks of wood to other tubes help hold longerons nice shape...
 
bryan albert said:
I am rebuilding A PA-12 I just got the fuselage back from the sandblaster the lower longerons have been spliced a few times and they are pitted in a few places. I have decided to replace Both longerons. Is there any pitfalls to avoid when I cut the old ones out. Do i need to make some sort of jig to hold the frame so it does not move when longeron are removed. I was going to do one at a time and take lots of measurements before i cut is that the best way?. If anybody has any pointers pictures that would be greatly appreciated thanks for the help.
Click to expand...

Now is the time to evaluate what you have.

A new fuselage from univair will save you tons of hours and make your plane very desirable if you decide to sell it.

Tim
 
Tim the money man. Needs more time in his life. Rebuild it. Just takes time.
 
Clyde Smith at one of his seminars showed a neat tool for drilling the old tube off the cluster. Looked pretty neat. Has a bearing that fits inside the tube and chucks in a hand drill. Looked through my stuff and i cant find who made them. Anyone know? It was a counterbore something like this with a bearing pilot.http://drillsandcutters.com/counterbores_aircraft_14_shank.aspxWith the outside diameter the same as the tube.http://www.supercub.org/forum/showt...can-I-buy-a-tube-drill-bit&highlight=longeronhttp://search.skygeek.com/?vwcatalog=stylespilotshop&keywords=piloted+spotface+tools&x=37&y=12
 
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What about using an expandable reamer? Cut the tube on ether side of the cluster and use the reamer to remove the tube from the inside - out. If the tube is pitted and thin it wouldn't take that much time to remove. I haven't done it but seems like an ok way to me.
Marty57
 
It is a "spot facer" with a pilot.

Sorry, the pics are scans of copies...

John Scott
 

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Jay (Javron) fastened my 12 fuselage to a level table made of I beams and cut off the tail. He replaced it with a short section from Univair. Went nuts attempting to get everything square and straight.

P8020109.JPG

For cutting the longerons from clusters,you can use a hole saw of the same size as the longeron and use another section of tubing that just fits inside the holesaw and longeron as a guide (5/8" for Cub longerons). They are cheaper and easier to find than spot facers. Work slow.

Wayne

PS Tim, I would have been lots of money ahead buying a new fuselage, not to mention time.
 

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you are making this way more complicated than needed....(AND doing the same grinding then TOO!!(after you wasted the time trying to cut center out))
just cause someone can make a fancier & more expensive mouse trap, doesn't mean you need it... especially if it takes longer to do the job....

as shown in longwinglover's pics... cut longer on so it looks like pic #2.
then grind from inside till it looks like pic #3... DONE!!
and it WILL take less time...

and I can't imaginge how slow a holesaw would be and how quick they would dull or chip teeth....

it "might" take you 5 minutes a cluster to do it my way.....
 
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When I did mine I built a simple jig out of metal studs with the fuselage upside down. Using metal studs you can clamp the fuselage down and they are perfectly straight. Pull a string through the center of fuselage and measure off of it to see how straight your fuselage is. Another trick is to prebend the new longerons to set in place before welding them. This takes the stress off of them so that when heat is applied welding they don't bend at the stations near as bad. Looks much nicer when finished. It's not to bad job at all. I would replace one at a time also.

Steve
 
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