longeron replacement

[cruiser]

When replacing longerons is it best to cut out the original down to the open end of the other tubes in the cluster or leave some of the original as a "saddle" for the new tube? Also is it permisable to drill a hole in the new tube so oil can enter all of the tubes in the cluster? Any advice? Jim

[T.J.]

delete

[Steve Pierce]

I cut the old tube out to the cluster and then carefully grind the rest so that the new tube fits nice and snug. I use a self closing blind rivet with PRC on it to seal the hole after oiling. Air Tractor drills holes at all clusters 1/4" and then pumps hot linseed oil into a fitting at the firewall, rotates it and drains out what is left after it cools. They have a bung welded in the tubing and insert an allen head plug. Of coarse their tubing is signifcantly thicker especially up front. I would be interested to know how others do it.

[cruiser]

Appreciate the replies, I have the air grinder and have removed all of the old longeron down to the existing other tubes. Am working on the old weld. I thought a hole in the new longeron adjacent to the open end of the old tubes in the cluster would be an efficient way to oil the whole thing internally but can do each tube individually. Thanks. Jim

[Steve Pierce]

I thought a hole in the new longeron adjacent to the open end of the old tubes in the cluster would be an efficient way to oil the whole thing internally

Jim, That is what Air Tractor does. I probably wasn't clear in my description. Doing that allows them to oil the entire fuselage in one shot.

[bearsnack]

When a longeron has been oiled in the past, doesn't it make for difficult repairs in the future to the tube? I am thinking that the oil will heat up and flow into the weld causing contamination.
i have oiled some tubes myself, but never had to repair these.Anyone run into this?
Joe

[cubpilot2]

Just finishing replacing entire lower longerons on the A model project I have. They were factory oiled in every tube and used the small rivets to plug the holes.
The old oil had congealed in the lower ends to form a paste and was a mess. I'm set up to rotate the fuselage while working on it so once the longeron was removed, (one at a time) it was rotated at a 45 deg angle and then the lower sections of the tubing clusters were heated and the congealed oil ran out. The tubes were then cleaned as well as possible and the longeron was reinstalled with the fuselage "upside down". That way any oil remaining would run the other way. Seamed to work out OK.
Think reheating the tubing helped to "revive" the old oil and respread it during the process. Will be heating the entire fuselage when completed to relieve any stress from welding etc. which will help all the more.

[Steve Pierce]

When welding in new lower longerons I leave a roset open as I weld the other clusters. Keeps the pressure from building up and blowing out the weld.