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Tripp · 02-11-2004, 01:58 PM

Uwe,

Regarding the stiffness, on later models (except some 70's) I would agree that they are stiff enough, but on the 50's models with the extra thin aluminum sheet and frame materials, I think a little more stiffness would be advantageous.

I'm not thinking a lot stiffer, just 15-25% or so. My main concern is the attachment of the u channel to the floor and the skin. I have to add a black tank (mine was a park model) and I am relocating the original heavy pressurized water tank to a under the floor plastic tank. I would like to stiffen the floor to protect the integrity of the trailer after these modifications.

Still, i would like all the suggestions I can get! I might miss something.

Tripp

markdoane · 02-11-2004, 02:37 PM

Tedd,

I really have to think through your analysis.
I look at the trailer as a composite structure. A very light, but longitudinally stiff body sitting on top of a relatively flexible frame.

As the frame, with all its appendages like tankage, batteries, and refrigerators bouces down the road it wants to flex up and down.

The body tries to resist this flexing because it doesn't want to end up with crinkles in its roof. The place where this fails is where the body and frame come together at the very rear where the stress is most extreme.

I think this is why, if any water gets in to weaken the joint between the body and frame, it fails and we end up with the dreaded rear end sag.

I think the body is much more rigid than the frame, and if the frame and floor were stiffer it would put less stress on the rear joint.

Agree? Disagree?

till · 02-11-2004, 04:10 PM

Mark,

I agree with what you are saying. That is why later in production the frame was altered. The addition on angle brackets and a cross member under the shell (at the rear section of the frame) to increase the attachment area. This cross member helps to spread the load out over a greater area.

What your saying about the wood rotting out and weakening the whole rear section is very true. Once you have the floor start to go (it is part of the structure) you start having a domino affect with the rear sag as part of the visual signs of a problem. Also the vibration presented by running gear out of wack adds to this problem.

markdoane · 02-11-2004, 04:19 PM

Quote:

Originally posted by till
Mark,

Once you have the floor start to go (it is part of the structure) you start having a domino affect with the rear sag as part of the visual signs of a problem.

Boy, isn't that a fact. I didn't have any rear end separation or outwardly visible sign of a problem. I was just trying to get my blacktank back in operation. Once I looked up under the bellyskin and saw about two inches of wood rot, I knew I was in trouble. The more you look, the more problems you discover.

My advice to any new owners of vintage trailers:

DON'T LOOK!

59toaster · 02-11-2004, 06:21 PM

Here is about 100 pictures of a floor being replaced.

http://www.airstreamphotos.com/photo...500&ppuser=155

If that link doesn't work goto www.airstreamphotos.com and look up "williamhenshall" He's on page 58 of the users listing.

It should all come clear between the pictures and digrams (great as usual) and seeing how it's built as you take it appart.

Step on is remove everything over the area you want to replace. Then pull the walls up the the floor seam where you plan to work too. Get the elevator bolts loose and you can get the bad section out.

59toaster · 02-11-2004, 06:22 PM

Ohhh yeah!
try to remove that as intact as possible to use as a templete.

74Argosy24MH · 02-11-2004, 07:15 PM

I wonder if turning the floor panels won't concentrate the movement in certain areas. Right now the floor can flex every few feet and spread it fairly evenly across the body and frame. If it can only move every 8 feet it seems like there would be a lot more energy to dissipate at those joints.

John

59toaster · 02-11-2004, 07:29 PM

Quote:

Originally posted by 74Argosy24MH
I wonder if turning the floor panels won't concentrate the movement in certain areas. Right now the floor can flex every few feet and spread it fairly evenly across the body and frame. If it can only move every 8 feet it seems like there would be a lot more energy to dissipate at those joints.

John

Shouldn't be a problem. The new ones are single sheets of partical I understand. I think it was Pashka that made that discovery when he put down his Cork floor.

74Argosy24MH · 02-11-2004, 07:34 PM

A single sheet would be the ideal, all areas would recieve the same stress. It's just what would happen when the stress that is spread across 5 or 6 joints is concentrated in 2 or 3?

John

markdoane · 02-11-2004, 08:12 PM

John,
I understand what you're saying. I think the answer is to bolt it down everwhere it crosses a crossmember, not just at the end-to-end joints. I got some good information on joints from the APA (American Panel Assoc) web site, on concrete form building.
Thanks for your suggestion.

till · 02-12-2004, 06:16 AM

At lest on my '67 floor, there is a 4" wide piece the is used to back the joint in the ply wood that appers to be glued and screwed in place. It is the full length of the joint. This will strengthen the joint .

markdoane · 02-12-2004, 06:24 AM

Tedd,
All the joints in my trailer were directly over crossmembers, and there are no joints at all in the fore and aft direction, so I'm really interested in how the joint in your unit was made. Was this joint you're talking about a side-to-side or a fore-aft joint?
Thanks for your help!

gerbermania · 02-12-2004, 10:20 AM

My 1969 also originally had/has the 4" wide 1/4" plywood, glued and screwed beneath the subfloor panel edges.

I was surprised to find this, and I'm continually impressed by overall AIRSTREAM quality. It certainly does help to have the extra width for the subfloor panels edges to bind to, since the main frame channels only have ~1-3/4" wide flanges.

While I had the bellypan off, epoxying/replacing portions of subfloor, I added some "Simpson Strong Tie" strap ties between the panels to make the subfloor act even more as a continuous diaphram, as it is ideally intended. This distributes the stresses more evenly.

Christopher

till · 02-12-2004, 11:34 AM

Mark,

The joint is side to side. You can see the seams on the floor as you walk from one end to the other of the trailler. I will get a photo of it tonight and post it or e-mail it to you. I'm thinking that since there is 8 years differance in our trialers, there are going to be some big differences. I'm upgrading my frame to a 1975 style with the steel cross member. There was an attempt made at some point to bolt in a cross member, but it failed.
I hate to take out all my floor since I can see where things went and where the tile and carpet were. I have photographed just about every square inch of the floor and walls to use as a refferance.

markdoane · 02-12-2004, 11:56 AM

When you say you are going to put in steel crossmembers like the '75, are you referring to just the one at the very rear? I thought all frames had crossmembers.

My crossmembers are 24" OC, so it matches the plywood joints very well.

Enjoyed your earlier post about the angle iron clips on the rear to anchor the frame to the body. I think I will do the same, but maybe go frame-to-frame across the back, or as far as it will go before the curvature becomes a problem.

till · 02-12-2004, 05:55 PM

Mark,

You are correct, just the one across the back. The rest start at 48" from the back of the shell and are on 24" centers from there forward. From what I can tell and have been told, the rearmost cross member didn't start till around '75.
You have the right idea about the angle. I will trim my angle to match the body curve. Got to love those curves.

Sorry, I ran out of day light to get the picture. I will try tomorrow, if not Saturday for sure.

till · 02-12-2004, 06:02 PM

let me see if this works....it ain't pretty.

markdoane · 02-12-2004, 06:38 PM

My '59 has a crossmember 22.5" forward of the rearmost xmember, don't see it on your drawing.
I think maybe this has something to do with the tanks. My blackwater tank sits above the floor. Do you have a blackwater below the floor, in the space where mine has the crossmember?

till · 02-12-2004, 06:57 PM

Yep! A black water tank goes in the space between the dashed line and the first cross member. There is a whole thread on this in the plumbing section of interior restoraton forum. I will give you a link here in a little bit. You can see what I'm up against in there. tcwilliams has been a huge help to me on that subject.

gerbermania · 02-12-2004, 09:09 PM

Here is a link to another forum thread where I posted some progress graphics. It shows both a rendering of the frame section and underfloor tank in question, as well as a diagram. I didn't want to waste server space by posting them again.

Also, note the foreground, where a section of the 4" wide plywood is shown spanning a crossmember at the plywood panel joint.

http://www.airforums.com/forum...&threadid=8560

enjoy,

christopher