Announcement

**N96337** · 01-20-2006, 10:50

Re: prefered tubing size for replacement lower longerons

Jason,
Take a cut out of one and you'll know right away.... .049 sounds a bit thick to me. The J-3 that I did a couple years ago was 3/4x .035, and my Bellanca was 7/8x .035, if I remember correct. The weight difference between .035 and .049 is only .0995 pounds per foot, so even if you replaced 12 feet on each side, you'd only be gaining 1.194 pounds per side in weight, and you'd be adding a bunch of strength....
John H.

**Ragwing nut** · 01-20-2006, 14:08

Re: prefered tubing size for replacement lower longerons

It is almost all .035 in the tail.

Mike

**jgerard** · 01-27-2006, 23:33

Re: prefered tubing size for replacement lower longerons

Sounds like .035 is what I need. AC Spruce seems to have good prices on the .500" .625" and .750" 4130 tube. I have been trying to work out a simple jig to make dam sure everything stays in-place as I start cutting. Anyone have a picture they could share of what they use? My idea is to run a 1"x2" square steel tube down both sides of the fuse from the landing gear area on the inside about 6" from the lower longerons and vertical side tubes and then out the sides at about the halfway point to the tail-post. Then using an adjustable bracket I can clamp all the side tubes and tail post to the 1"x2" square steel and lock the fuse together creating a temporary false lower longerons and belly cross/diag tubes. I know it's overkill, and I could probably do it the oldfasion way by removing and replacing one tube at a time. I would rather 1.) remove the complete belly section from the factory splice aft 2.) lay in the new left and right lower longerons and tac weld them to the side vertical/diag tubes 3.) cut-fit-tac weld all cross and diagonal tubes 4.) replace lower 1/2 of tail-post 5.) finish weld joints. I have all the info regarding all the major dimensions so I can check my work as I go. Since I need to replace all the belly tubes aft of the splice I did not want to lay the left longeron in tack it back to the rotten cross tubes lay the right longeron in and tack it to the same rotten cross tubes, then start cutting the tac welds to replace those rotten cross/diag tubes. If I can keep the fuse together in a simple jig I could have a much cleaner and faster repair. My idea of a partial jig would be more like how you would build a fuse from scratch by building the sides first and then joining them together in a jig. This will be MY first major tube replacement project.

Jason
N43643

PS - Mike you said it's almost all .035 in the tail. What isn't .035?

**N96337** · 01-28-2006, 12:00

Re: prefered tubing size for replacement lower longerons

Jason,
Here's the setup I've used before, and I'm really happy with it. I have 2 tables, 4x8, and they bolt together in the middle, then screw to the floor. This makes a really nice, solid surface to start on. Then I lay a couple 2x10's lengthwise, and screw them to the table, then pickup the fore and aft gear attach fittings with 2 peices of square tubing, bolted through the gear mount holes and screwed to the 2x10s. You can also come forward and pickup the lower engine mount lugs at the bottom of the fuselage if you want. Then I set the fuselage in it and get everything as level as possible in all ways with a digital level. The reason I do that is that I can continually reference level and vertical as I work back with the replacement tubing and keep it all looking nice and strong (I also check my reference points a few times every day, to make sure things aren't moving around on me). I stand a tube, vertical from the table, welded to braces to keep it that way and screwed to the table. At that point, I decide if I'm going to weld lugs to pickup the rudder attach fittings or whether I'm replacing the whole tailpost (what I usually do.. splicing is about as much work, and I'd just as soon have a nice new piece of steel there), and adjust it accordingly. This seems to keep things nice and square and sure makes it easier to do the welding, as I'm not on the ground, and can stand and get things at least tacked up pretty well without any trouble, and even welded completely in most spots. The tables are also really nice when doing fabric work, for laying out fabric to make nice straight cuts, etc.
As you can see in these pictures, I cut this Cub at the factory splices and replaced everything from their back. It was bent and twisted so badly that there was no way to get accurate measurements, so we worked from a blueprint.
John H.

Attached Files

**jgerard** · 01-28-2006, 12:36

Re: prefered tubing size for replacement lower longerons

That is kinda what I was planning on doing with the exception of using the floor instead of a table. I have the fuse upside down right now and level. I am working on an attachment that bolts to the spar attachpoints and then to the floor. I was going to do the same thing at the tail but use the rear stab attach tube as an attach point. I know my floor is not perfectly level, but my plumb line is.

Jason
N43643

**N96337** · 01-28-2006, 13:18

Re: prefered tubing size for replacement lower longerons

You might also check with Columbia Airmotive in Troutdale, OR for tubing. That's where I got the full length pieces for my Bellanca when I was living in Bellingham/Ferndale area.
John H.

**jgerard** · 01-29-2006, 00:32

Re: prefered tubing size for replacement lower longerons

Here are a few pics of what I have so far. Need to finalize my tail attach part and mount the front cross tube to the board. I have taken all my measurements from the thrust line as per factory drawing. When I start putting it back togeather I will stretch a second center line closer to the new tubes. By the way waxed round rib stitching cord is awesome for running reference lines!

http://gallery.taylorcraft.org/main.php?g2_view=core.ShowItem&g2_itemId=3959

http://gallery.taylorcraft.org/main.php?g2_view=core.ShowItem&g2_itemId=3962

http://gallery.taylorcraft.org/main.php?g2_view=core.ShowItem&g2_itemId=3965

http://gallery.taylorcraft.org/main.php?g2_view=core.ShowItem&g2_itemId=3968

Jason
N43643