Question about small tubes on fuselage structure

[Luked 71]

Here's a dumb question. What are the little tubes welded into the fuselage at some of the tubing clusters? I'm guessing they have something to do with the factory jig. Here is a picture:

The reason I ask is because I'm going to cut out one of the tubes next to one. I'll probably cut out the small tube also, and I want to make sure it's not important for anything.

 

Thanks,

Luke D.

[FredStork 454]

Factory jig is a good guess. They are clearly not used, or needed, later...

[FredStork 454]

But Luke, more concerning is the holes drilled in the tubes - both for rust and strength.... I would replace all pierced tubes...

[Luked 71]

Thanks for the reply Fred. I figured that was it.

Good thoughts on the holes. The original builder thought it was a good idea to pop rivet quite a few things to the tubing. It was built in 1988. The holes had rivets in them until I drilled them out. I inspected the insides of some of the damaged tubes that I replaced where they had rivet holes. They had no rust inside. My plan is to weld all the holes shut. I will be welding mounting tabs for anything that I need to attach to the fuse structure. 

I don't think any moisture got inside the tubes. What do you think? Replacing some of the tubes with holes would require cutting apart significant parts of the fuselage.

[Fly-n-Low 181]

 

But Luke, more concerning is the holes drilled in the tubes - both for rust and strength.... I would replace all pierced tubes...

I was thinking the same.

[akflyer 1427]

Some of those were meant for bolting on baggage pods etc.  Remember that at one time they sold spray bars etc for crop dusting with these.  They are more than likely not needed for anything you would be doing with it.  Most jig points I have seen on planes are the wing, engine and gear mounts then you fill in the blanks with tubing. 

I have seen tons of holes drilled in the tubing on cubs etc for various mounts because they didn't want to use welded on tabs as that would require cutting fabric etc.  Adel clamps can be used in most places that people have drilled holes in the tubing.

 

 

[Luked 71]

Okay. Thanks guys. I won't worry about them. I just always wondered about them.

[dholly 718]

If you ever intend on adding floats, I'd advise you leave them in place. They make adding a removable rear float bracket easy, no need to cut away and patch fabric for welding. Secure bracket to plane with bolt thru the vertical tube, then another u-bolt around the fuse tubing. I've attached some pics to give you the idea.

[Luked 71]

Now you tell me...   They actually would have been hard to save because of the repair I was making. I'll have to decide if I want to go to the effort to replace them.

Thanks Doug