68 Overlander Restoration/Mod

[Aluminati]

Hey All. I am about knee deep in my restoration/modification project.

Today, I have taken off the streetside interior panel.
I dont understand what I see.

First...I thought that when I saw the main ribs of the inside that the full end would be sitting in the c chanel...it is not. It looks to be cut to a 45 degree angle and the only side that is in the chanel so to speak is the on facing the exterior skin.

Second...I removed the furnace and it looks like one of the ribs were cut to install the furnace.

It also looks like the cross bars do not connect to the main ribs.
The windows dont seem to be attatched to the main ribs either...I could not tell because I did not go that far up the wall.

The C Chanel does not connect
The "insulation" is taped in place

What gives?


With all this said...where does the structure come from.
It seems solid, but when I took the panel off...I can wiggle the main ribs a bit.

Is this normal?

[Aerowood]

Yep, thats how they are made. Mine frame to "C" channel WAS that way at first, they are tied together now. I,m still working on the stringer to frame attachments

[Aluminati]

So where does the strength come form? Is the All Clad aluminum structural aluminum?

[Aluminati]

Originally Posted by Aerowood

Yep, thats how they are made. Mine frame to "C" channel WAS that way at first, they are tied together now. I,m still working on the stringer to frame attachments

Is that the original aluminum beam you have anchored?

[overlander63]

Basically, all the parts work together as a unit that is strong, but will flex with movement and expansion and contraction from heat and cold. If you make it too stiff, you will do more harm than good.

[TomW]

Originally Posted by Aluminati

So where does the strength come form? ...

Terry made a good post.

If you want more detail, Google keywords "unibody", "monocoque", and "semi-monocoque". An Airstream utilizes "semi-monocoque" construction.

Tom

[byamcaravanner]

The strength comes from the skins. The ribs are only there to hold the two skins in relation to each other. You do not want to create a point load at the ribs because that will transfer a point load to the skin. The system relies on the loads being spread over a large area. Point loads will cause rivet pops and tearing of the skins.

Just focus on repairing what is broken. The system has been proven by a half century trailers. Damage is normally caused by inadequate maintenance... as Inland Andy has pointed out many times.

Happy to see you are into the "fun" part!

[Aerowood]

Originally Posted by Aluminati

Is that the original aluminum beam you have anchored?

Yes that is the original frame that is now tied to the "C" channel. The channel was attached with pop rivets on the flanges of the frame but all the original rivets had failed some time in the past. Attaching the stringers to the frames will not cause the shell to become any stiffer or cause any point loads. There are more point loads now in the structure at the first and last rivet in each stringer then there will be with the stringers attached to the frame. The shell and frame work will still have the ability to flex plus giving the AS a more true semi-monocoque structure. The Airstream construction as from the factory is more of a reinforced shell then a true semi-monocoque structure.

[Aluminati]

Originally Posted by Aerowood

Yes that is the original frame that is now tied to the "C" channel. The channel was attached with pop rivets on the flanges of the frame but all the original rivets had failed some time in the past. Attaching the stringers to the frames will not cause the shell to become any stiffer or cause any point loads. There are more point loads now in the structure at the first and last rivet in each stringer then there will be with the stringers attached to the frame. The shell and frame work will still have the ability to flex plus giving the AS a more true semi-monocoque structure. The Airstream construction as from the factory is more of a reinforced shell then a true semi-monocoque structure.

Stringers Point Loads O.K...please slow down...This is all new terminology for me. What by gum is a stringer and a point load. Looking at it from the outside...it looks like the window is riveted to the rib...at least I thought...is this correct. I searched for simi-monocoque but did not find anything...I will search again. Sorry for sounding like a dimwit but I am only familiar with beams, crossmembers. I have built a few residential walls, so it just threw me off when I pull the panel back and saw what I saw.

[Aluminati]

...and I cant believe that they "taped" the isulation in place...

So if ai am understanding you correctly...the outter skin is where alot of the strength comes from. If that is true then wow...my hat's off to the guys who built this thing and that it has lasted so long.

[Aluminati]

Originally Posted by Aerowood

Yep, thats how they are made. Mine frame to "C" channel WAS that way at first, they are tied together now. I,m still working on the stringer to frame attachments

Your floor looks great...what did you treat it with?

[Aluminati]

Originally Posted by TomW

Terry made a good post.

If you want more detail, Google keywords "unibody", "monocoque", and "semi-monocoque". An Airstream utilizes "semi-monocoque" construction.

Tom

Sorry...My brain popped a bad rivet...you said Google the keywords. Me getting is bass ackwards just searched thoes words at this site.

[Aluminati]

Can water come through a hole where a rivet used to be...on the side of the trailer. I remember seeing some water track marks from a location on the side of the trailer. There is a rivet missing.

[overlander63]

Originally Posted by Aluminati

Stringers Point Loads O.K...please slow down...This is all new terminology for me. What by gum is a stringer and a point load. Looking at it from the outside...it looks like the window is riveted to the rib...at least I thought...is this correct. I searched for simi-monocoque but did not find anything...I will search again. Sorry for sounding like a dimwit but I am only familiar with beams, crossmembers. I have built a few residential walls, so it just threw me off when I pull the panel back and saw what I saw.

Stringers are analogous to crossmembers, they extend out to the bow (another term) and support them through the floor. Bows are the vertical crossmembers that start at the floor, and go up to the center. And yes, the insulation is taped in place, otherwise it would fall down the inverted curve to the ceiling.

[Aluminati]

Originally Posted by overlander63

Stringers are analogous to crossmembers, they extend out to the bow (another term) and support them through the floor. Bows are the vertical crossmembers that start at the floor, and go up to the center. And yes, the insulation is taped in place, otherwise it would fall down the inverted curve to the ceiling.

So the ribs that I am seeing are what is called formers ( forming the basic shape of the AS)...in Semimonocoque terms? and the crossmembers that are horizontal are stringers?

[Safari Tim]

Shameless plug.

We talked about Airstream construction a long time ago on theVAP.

[overlander63]

Originally Posted by Aluminati

So the ribs that I am seeing are what is called formers ( forming the basic shape of the AS)...in Semimonocoque terms? and the crossmembers that are horizontal are stringers?

Yes.

[Aerowood]

Originally Posted by Aluminati

Your floor looks great...what did you treat it with?

I had several partial cans of poly that I mixed all together. semi gloss ,satin, gloss, indoor, outdoor. some tinted maple, you name it , it all went into a large can and I squeegeed it on,three coats worth. After everything is done I will most likely put some epoxy down that I have.

[Aerowood]

Originally Posted by Aluminati

Can water come through a hole where a rivet used to be...on the side of the trailer. I remember seeing some water track marks from a location on the side of the trailer. There is a rivet missing.

Yes

[byamcaravanner]

Originally Posted by Aerowood

Attaching the stringers to the frames will not cause the shell to become any stiffer or cause any point loads.

True... but bearing the rib on the "C" channel/floor will. There is a reason they stop the ribs above the floor.