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Old 01-31-2004, 03:32 PM   #1
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Rear End Separation Questions...

I've got a 1977 31' soveriegn with a full rear bath. So far I've put a frame kit on(because of a cracked frame), pulled of the elephant ears, ripped out the toilet, ripped out the water heater, and taken out the most of the belly alluminum in the rear. I've also purchased new axles, shocks, and tires to prevent this from happening again. my question is why is there plywood sandwiched between the frame and the body. The plywood isn't sandwiched between the two anywhere else that i can tell except in the very back. I havn't ripped out the floor, the sink or the bathtub either. how much will i have to take out to replace the sheet of plywood? any help would be greatly appreciated.
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Old 01-31-2004, 03:58 PM   #2
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MDew you are going to have to give us a lot more information I think.
What did you mean by sandwich?
The floor as you surely know is plywood. So has someone forced a plywood shim between the frame(c-channel) and the plywood floor?

If your trailer has the "elephant ears" that I am familliar with then a case of rear-end separation may have already been addressed.
What did you see in there when you removed the "elephant ears"?

Tail sag or tail droop is NOT the same ailment as rear end separation. Although one may contribute to the other.

I suppose you have already read the thread Saggy Bottom elsewhere on these forums??http://www.airforums.com/forum...t=saggy+bottom

I must figure you removed the toilet and WaterHeater to repair rot, right?
I see no need of their removal for frame stiffening or rear-end separation work.

Have you removed the black and grey water tanks and their frame?
Yes I think you will have to remove the tub for a complete floor replacement but are you sure that all the floor is rotted wall to wall.


As an owner of a similar model I am interested in following all circumstanses like your's. I hope you will keep us all well informed as you go along on this. Are you doing this repair yourself or hiring it out?
Would like blow by blow on the axle replacement as to who did it, costs and results.
Also on the frame kit. Where did you buy it and was it simple to install and costs if you are willing.

Help will find its way to you if you search here and other forums.
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Old 01-31-2004, 04:32 PM   #3
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ryan.

The shell is attached to the floor and then that assembly is lifted and placed on top of the frame that is in a "jig."

At that point, the two are fastened together.

Frame cracking at the axles is very common, "WHEN" total disregard is made towards any running gear balance.

Contrary to opinion, adding the frame beef up kit does not stop any rear end separation, nor does it stop any frame cracking at the axles.

What the frame does allow is the frame can be abused even more so, before it fails again.

We have repaired several trailers where the frame, axle mounting plate AND the beef up kit were "ALL" cracked in half.

The loud and clear message is that the running gear must be kept in reasonable balance, or, frame failure will occur, regardless what it is made of, or how it may be beefed up.

Some owners are resorting to making a completely new frame with heavier materials. That's great. However, the fact still remains that balancing is an absolute "MUST." If disregarded, frame failure will, at some point, occur.

GAURANTEED.

Adding the elephant ears to the rear quarter panels, is without a doubt, the very poorest method, bar none, of repairing rear end separation. It's an excuse to send someone down the road, as a happy camper. But, that type of repair will not allow the proper refastening, AND, certainly does not allow the installation of additional fastening.

Andy
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Old 01-31-2004, 07:09 PM   #4
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If you look at my photo's you will see how I did mine. and it is how Airstream does there's.... If you go to Jackson Center this will be how it is done..
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Old 01-31-2004, 07:26 PM   #5
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ok. the only reason i put on the frame kit is because the frame was cracked. i put it on simply because i didn't like the fact that i had a crack in my frame. The reason that i'm ripping out the toilet, water heater, etc. is because it says in my airstream owners manual that nearly all of the bathroom is one piece of plywood. when i say sandwich i mean that the frame is on the bottom which then has a bolt that goes through the plywood, which then goes through the body. the floor is definately rotted where the bolts go through the plywood and into the body. which, by my understanding, means that entire section of plywood should be replaced. I don't want to EVER do this again. i havn't used my airstream in 6 months because i want to get this taken care of all at once. My main question is why do the bolts that connect the frame and body even pass through the plywood?? Couldn't I put some highdensity plastic in there or something to act as a spacer??? this would elimate the possiblity of plywood rot as a cause of rear end seperation correct??
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Old 01-31-2004, 07:38 PM   #6
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jpairstream....aren't those pics taken after the repair was done??? My plywood is so rotted that you can flick it with your finger and knock off a huge chunk. it looks like you did a great job with your repair though. i hope i can do it half as good as you.
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Old 01-31-2004, 07:42 PM   #7
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Brian,

I think we can see the source of your confusion now.

The Airstream construction is moncoque - like an airplane. And the floor is an integral part of the construction. Instead of being supported by the frame, the body (including the floor) IS the frame - all that metal underneath really only supports the running gear and tanks, and also unifies the floor structure. The frame itself is bolted to the floor, in many different places.

So, when repairing rot in the rear end you have to restore that structural continuity - which means the new flooring sections have to tie together, fit in the U channel around the perimeter, and bolts have to run up through the floor and on up through the U channel.

There are dozens of posts on this, unfortunately not in one convenient location. Do a search on "rear end sag", "rear end droop", "floor rot", "tail droop", and "replacing the floor" and you should find most, if not all the experience others have had.

You are not alone.

Mark
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Old 02-01-2004, 01:07 AM   #8
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Question

QUOTE]Originally posted by JPAIRSTREAM
If you look at my photo's you will see how I did mine. and it is how Airstream does there's.... If you go to Jackson Center this will be how it is done.. [/QUOTE]


JPAIRSTREAM
I looked at your photos.
http://www.airstreamphotos.com/photo...er=944&thumb=1
Thanks for putting them there. I would have missed them if not for this thread I'm afraid.
I wish you would go back and put a write-up with each one.

Did you do your repair or did Jax'Ctr. do it?
You say it was done by the factory method. But service bulletin #146 shows a 3x3 inch hole cut. And your pictures as well as the drawing you posted at your photos and a year ago at "Soggy Bottom" thread http://www.airforums.com/forum...m&pagenumber=2
show elephant ears cut out. Other than the cutout the method may be the same, not sure.

I hope Inland Andy will give a description of his method as well, since he says the "elephant ear" method is practically useless.

Your plywood looks new. If so did how far back under inside skin did you replace it? If so that must be a whole nuther story.

Where did you get the short curved U-channell pieces? Looks like aluminum ??
The heavy metal (angle?) across the trunk door opening, is that a replacement piece or a custom fix? What exactly is it's purpose?

Why did you bend over the bolts?
Are the two ribs (studs) at the rear the only thing that breaks loose and causes the separation. Looks like the lower ends of these ribs would be ripped and buggered up too bad to accept the short angle brackets that you attached to them. I would think I will want to run the angle about 4-5 inches up the rib.

Are the original rib ends just riveted into the channel with a couple of rivets on each side of channel?
Seems like the skin would also prevent the separation from dropping. Unless rivets tore the skin. That would be a tell-tale sign that I have never seen reported. Is there a line of rivets running up the ribs back there?


Lots of questions I know(probably more to come) , but such an important issue.
Hope this makes sense
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Old 02-01-2004, 05:06 AM   #9
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jaco,
I will let JP fill in his details, but this is what I know He has one picture on there that shows the bad plywood. Some of the repairs were done using the 3" plates others using the elephant ears, not sure why the difference I think it is related to model year(s)? What you have is the body, both inner and outer panels are riveted to the curved channel, the channel is bolted to thru the plywood into the steel of the frame. The failure occurs at this connection. Apparently the bolts shear, rust, break, or something allowing water to enter at the joint causing the plywood to rot futher weakening the connection, if it is not repaired very early on in the game the rot can get bad enough that the floor is gone, the frame is rusted and the channel will rust thru. As far as the ribs are concerned I think the bulk of the damage occurs to them by corrosion and impact from the lower floor and frame banging around (this is just my theory and totally unsupported) Think about how far back the bathroom is from the axle, and how much everything weighs, especially if your holding tanks are full. Kind of like the fat kid on the seesaw, I have rearend seperation on mine, it is going to have to be fixed. I plan to pull the whole bath because I have a couple of other things I want to do at that time too. I will post pictures when I get to it, but it is a ways off.

Aaron
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Old 02-01-2004, 10:28 AM   #10
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ok.. exactly what are elephant ears. i thought they were the external pieces of aluminum that are on both sides of the valve access door on the rear of the trailer. also, my u-channel piece on the left side of the trailer is broken in half exactly where the one of the bolts went through. anyone else ever have this happen?? how do i fix/replace it? keep the questions/sugestions coming!!!
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Old 02-01-2004, 11:07 AM   #11
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Yes I did these repairs myself.

I also had the frame supports installed but I did not do these.

I am not sure what balancing will do for this type of damage. The bottom line was there was to much weight in this area. this is what has caused the damage. I am just hoping it will not come back after doing this work including the supports on the frame. My frame was bent but not cracked. It was bent allowing for the downward force on the rear end area. (Keep in mind Airstream did at one time balance there assemblies and in the time period that my 72 was built they had been. So why did it still happen to mine if they had been balanced.)

Quote:
Your plywood looks new. If so did how far back under inside skin did you replace it? If so that must be a whole nuther story.
18" back was replaced So it was not terrible to do. Was not to bad shower is notched. RS was not bad at all.

Quote:
Why did you bend over the bolts?
So they would not back off.

Quote:
Are the original rib ends just riveted into the channel with a couple of rivets on each side of channel?
They are the rivets along the bottom channel had been torn loose.

I did add notes to my pictures..
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Old 02-01-2004, 02:45 PM   #12
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Ok, I'll bite....I'm reading all this and I am concerned. I bought a brand new 25' Safari C and I too have a rear bath.

What should I be doing now and down the road to make sure that I don't have similar problems? What can I balance besides the tires?

Now I will say that I have noticed that most of the folks that posted on this thread have older units. Were most of these issues worked out in the 90s?

Eric
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Old 02-01-2004, 04:09 PM   #13
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Okay here is the basic physics of it, think of the fat kid on the see saw... the longer the seesaw the harder he is going to come down. Eric, your momentum lever (I think that is the correct term) is a lot shorter than the ones on the 31' ers that have the majority of the problems. I am not even going to attempt to get into all the fancy calculations involved, but the longer the distance from the wheels to the weight the more impact involved. This is where Inland Andy's wheel balancing comes in, the vibrations of an unbalanced running gear is going to be magnified the further out from the running gear you go. I don't think the factory has ever completely balanced the running gear on any unit. Trailer wheels are notorious for not being balanced as well as being difficult to balance. I purchased a set of wheels and tires for a small utility trailer, we could not get the one wheel to balance, we pulled the tire and rotated it on the rim, it still would not balance without excessive weight. We finally ran the rim with out the tire on the balancer and it was welded off center. It was returned for different rim. I would wager that less than 1% of any RV dealers even bother to check or balance the wheels much less the running gear on any RV they sell.

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Old 02-01-2004, 04:27 PM   #14
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Eric,

We were referring to those 70's rear bath coaches where the problem seems so often to arise. They were not originally designed to take the weight of the grey water tank.

Your coach has been engineered to take the load, and the fresh, grey and black tanks are placed close to the axle, to keep the weight from causing the moment arm problems Aaron described.

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