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malconium 06-03-2004 06:24 PM

Body and banana wrap on floor replacement technique.
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In the process of restoring our recently purchased 1973 31' Sovereign I have discovered that I will need to replace at least some of the floor. Depending on the condition of the frame, etc. I may not want to remove the banana wrap to get to the u-channel bolts that hold down the body. I would also prefer to avoid a full body off effort. In thinking about what approaches I could take for floor repair I came up with a technique that I think might work. Please refer to the attached drawing for details. Here are steps I would anticipate taking in the process:

1.) Mark new floor panels with locations of cut outs and holes in the floor. I would consider running the sheets of plywood for the curved ends cross-wise as in the original but I think I will run the other panels length-wise. For one thing this makes it a lot easier to lay down a new sheet of plywood on the floor and transfer opening locations to it.

2.) Remove the old floor. I like the technique listed somewhere here in the forums about cutting the floor between the supports and cutting out the fasteners with a saws-all. Leave spacer blocks under the u-channel as necessary to keep the body lifted above the frame.

3.) Cut rim strips (see drawing) out of your intended floor plywood about 3" wide for the sides. For the curved ends cut the rim strips out of a full sheet of plywood (to fit the curve) and save the remaining pieces for later.

4.) Set the rim strips in location and mark where the side to side frame rails cross them. Make sure that joints in the rim strips all occur over frame cross members.

5.) Cut splice strips about 5" or 6" wide. For the curved ends you probably can use the triangular corner pieces - don't use the big middle piece since you will need it later. Remember the splice strips will be used in short pieces between the frame cross-members. Use a router or table saw to thin out the splice strip along the outer edge to clear the thickness of the frame side member where it will be sandwiched between the rim strip and the splice strip.

6.) Attach the splice strips to the rim strips with glue and screws (make sure to keep the screws out of the area where the assembly will slip over the side frame members. Of course use a strong and water proof glue.

7.) Insert the rim strip and splice strip assembly in place along the out edges of the trailer. Remove the support blocks as necessary gain clearance in a given area. Drill new holes through the rim strip and splice strip from above (in the location of the holes in the u-channel). Bolt all the way through both the rim and splice strips. Note that the bottom of the bolt is easily accessible without removing the banana wrap. I might consider using captive nuts on the bottom of the splice strip - the kind that bites into the wood. I will also use either stainless steel or maybe galvanized bolts.

8.) Cut and fit the main floor panels into the space between the rim strips. Attach them to the splice strips with glue and screws. I am thinking about using self-drilling/tapping stainless steel screws to attach the main floor panels to the floor framing.

Some additional thoughts about this approach:

1.) The extra weight will amount to about 1/2 a sheet of plywood. That does not seem like too much.

2.) In general I have thought that the length-wise edges of the plywood do not need a lot of support. The splice strips do provide support but they are there mostly to help transfer side ways forces on the body and frame to the plywood diaphragm of the floor.

3.) The splice strip will add some additional stiffness around the curves where this is no metal frame member.

4.) My thought lately is to use treated plywood for the floor. I found out recently that there is a new type of plywood treatment available that avoids the perceived toxic issues associated with the older green stuff. The treatment I think is called ACQ. In my area (Portland, Oregon) I can get 3/4" CDX sheets for $49.99 per sheet. CCX plug and touch sanded goes for $61.39 per sheet. This type of plywood is certified for use underground such as in wood foundation systems.

I would appreciate any feedback on this proposed technique before I get too far along with implementing it. I do have further thoughts on the merits of this approach too if anyone would like to discuss them.



markdoane 06-03-2004 08:14 PM

(wonderful name, I have a brother named Malcolm)

1. Great idea, I don't see why it wouldn 't work.
2. I would seal all the edges if you can.
3. For the rim and splice, what type of plywood are you going to use? If you can get B-B plugged it might be worth the cost. B-B plugged is used by boat builders for engine boxes and bulkheads. All the interior voids are filled.

Very creative approach! Let us know how it works out.

jaco 06-03-2004 11:32 PM

It is a very interesting hypothesis.

Looks as if it would work if you have enough cleared area to work in (interior bulkheads and furniture and bath fixtures out of the way).
The integrity of the splice is important of course but should be a bit forgiving due to the support of the crossmembers, outriggers, and main rails. The screws will have to act as clamps for the glue as you know as I see no way to apply clamps. Or are you planning to combine the two strips before placing them into rim?

I think I would line the splice with a strip of rosin paper or tyvek, or tar paper (roofing felt) before I laid the floor onto it. Might eliminate squeaking and should seal against ants.

Additional things to consider might include:

How to place the bolts from above... remove the inner wall or just pull it back and up to make room for a wrench? Or cut holes into it? This might be the biggest challenge.

The space between the upper (verticle) banana wrap and the main frame rail.
Again you will be working under there with glue? and tightening the bolts/nuts.

Also if there are any plumbing pipes or heat ducts beneath floor you may have headaches working around those.

Nicely presented, I wish you the best of luck and look forward to all your reports.

Ken J 06-04-2004 05:43 PM


Are you placing the rim strip around the entire trailer or do you just have one area that is rotted? If you are replacing the rotted area, is it fairly minor - ie 3 in or so from the wall? I think I understand what you are doing, but want to make sure I understand what your doing.


uwe 06-04-2004 06:10 PM

What exactly are you doing?
Where is the damaged area?
Once you have interior access, it is not necessary to d a full body-off-frame to replace flooring panels, due to the inherent flexibility of Airstream trailers. i am hoping you don't make yourself more work than necessary.
If you get the channel loose, you can usually sneak pre-cut plywood sheets in place with a little finesse. It worked for me when I replaced the entire bathroom floor.
Best of Luck!

Sneakinup 06-04-2004 06:19 PM

Been there, done that. Works like a charm. :D

My design

The whole story

Ken J 06-04-2004 06:48 PM

Is the reason for the double floor to give you more surface to bolt the rear to? Instead of one line of bolts in the C channel, you now have another row of bolts through the treated wood and thus better hold down for the rear?


Sneakinup 06-04-2004 06:53 PM

I used the double row of bolts to bond the two floor sections together.

This method (in my opinion) won't work on all flooring situations. In my case, only the last 4-6 inches of the trailer floor was rotted away. The lower piece of wood, or support, has to be cut and notched around the bw tank, pipes, etc. Different years have different setups. For my Overlander, and the extent of my floor rot, this method works.

Ken J 06-04-2004 07:02 PM

Thats what I figured, from what you and Malcom are saying - you all had rot that was limited to 3 inchs or so - then the repair makes sense to me.

Ken J.

malconium 06-04-2004 07:37 PM

Some answers to questions...
First of all let me thank everyone that has commented so far and appolgize for the double drawing with the post. I will get that right one of these days...

Here are some answers to questions I have received so-far:


What type of plywood? I am leaning in favor of CDX or CCX treated. I am guessing that any voids would be pretty small and would not severly impact the support capabilities. Any larger ones should be obvious when I cut my strips.


I do indeed have everything out of the trailer. It came with a lot of the stuff removed and I am almost done taking everything else out. So now is a good time to replace the floor since I am not likely to want to do it once I get everything back together. I am indending to combine the two strips together before installation. I am also planning to glue the main floor to the splice strip so I would not want to add felt first. Generally I thought I would either remove the lower interior panels or at least loosen them enough to roll them up a bit. I do not know how easily the stuff would flex up so I am reserving judgement on this one. You are right I will have to watch out for any pipes or ducts. Worst case I might have to leave out the splice piece in some locations.

Ken J

This propossed technique was intended to work for all the way up to a full floor replacement with the rim strip all the way around the trailer. I already know that I am going to have to replace plywood at the back end and most of the way down the curb side. I am having a debate with myself about whether or not I should just go ahead and replace all the plywood instead of just what needs fixing now. I am not likely to want to have everything out of the trailer again so it might be now or never. I am wrestling with the cost of treated plywood. I can get CDX treated for about $50/sheet and CCX (plugged and sanded) for about $68/sheet. To do the whole floor on my 31' using this technique would take pretty much all of 8 sheets which adds up quick. If I took a more conventional approach I could make it work with 7 sheets - still a bit steep just for the sub-floor. I was not trying to fix a floor where just the last 3 inches was gone like Sneakinup appears to have been doing.


The emphasis with this technique is not entirely the body on part. I understand that I could sneak sheets under the body (in fact I would be sneaking the rim strips under). Part of the idea here is to avoid having to drop the banana wrap to get to the bottom of the fastners that hold the body on - especially for re-installation of the floor. This technique allows me to tighten all fastners from above (unless something under the floor is really in the way).


My approach does not add the extra metal channel that you added but I like your idea for the back part where there isn't any frame support around the edges. As a matter of fact the frame cross-member across the back of my unit looks a bit rusted out and could probably stand some extra help (unless I end up replacing that part all together).

Some general comments:

I think my proposed technique is in some sense motivated by laziness (the father of invention - necessity being the mother?). I don't really want to remove and re-install anything more than necessary. If it turns out that I have to remove the banana wrap for other reasons then I suppose the technique begins to lose its appeal somewhat - partly because of the extra sheet of plywood. I am going to be working on my rig tomorrow to finish assessing just how much of the floor I am going to want to replace and whether or not I need to remove the banana wrap. If I do end up using this approach I will try to document with photos that I can post later. If not then my apologies for stiring up the pot. Never the less this technique might still be of use to someone else even if it does not end up being what I use myself.


Ken J 06-04-2004 09:12 PM

You have not stirred up the pot in my opinion - I always really enjoy talking about new ideas.

I went back and looked again at your idea - I now see what you are doing - bolting the sub floor, then screw/glue the subfloor to the main floor (sorry it takes me a while sometimes). Yeah, that would work - since todays glues are really strong. Hmmm - really makes me think.

I think I would use a good quality AC plywood - perhaps soaked with epoxy - althought not to sure how good the epoxy would do once you start drilling in bolt holes - perhaps AC above and treated below. CDX is mostly glue and is very heavy. I would also make the rim strip and splice strip as wide as possible so as to get a good grip to the main floor - certainly would not want that joint to fail.

And cost - ahh, its only paper - nothing is too much for our prized trailers! :) :)

Please keep us posted


malconium 06-06-2004 01:12 AM

Progress report and more questions?
I spent a long day today working on the trailer with a main focus to be to determine how much floor to replace and to better determine the feasibility or desirability of my propposed approach for flooring repair. I made some rather startling discoveries and I wonder if some of this is normal or if perhaps a PO made some changes - maybe even replacing some of the floor panels at some point in the past.

1.) Regarding the curb side where I have floor rot in places between the entry door and the back bedroom: I think I already may have mentioned in this thread that the side wall there was bowed out as much as an inch. What I found was that the u-channel was only being held in place by screws into the wood floor! These screws were about 1" long and were not very well attached to rotted wood in much of that area. It is no wonder at all that the wall could move out from the floor like it did! Is this type of attachement normal for the sides?

2.) I had expected to see bolts through the floor to the frame at least at the side bows down to the outriggers but there are none anywhere except around the back corners where there seem to be quite a few. Again is this normal?

3.) I expected to see a frame rail of some sort between the outriggers along the sides. For some reason I had thought that the back curved sections were the only places that did not have some sort of side rail. There is a perimeter rail along the back edge that is essentially the same as any of the cross members that go side to side between the main frame rails. Since I saw no sign of side rails I can only suppose that there never were any along the sides. This definitely makes me want to do something to re-enforce the connections along the sides. Depending on how much other stuff I decide to do to the frame or floor I may want to weld some rails along there. If I do decide to do that I might want to add enough metal along the top to perform the function that I had envisioned for my splice rails in the original drawing. By the way I did discover that my u-channel does also have a c-channel below it that the edge of the wood is supposed to slide into. I suppose that this helps with the strength issue but is does depend an awful lot on the integrity of the wood. Does anyone have any thoughts on the sufficiency of this type of attachment?

4.) I discovered that there are places near the middle of the floor where the floor has 3/4" plywood shims between it and the frame crossmembers below. I would not have thought this to have been original procedure so I am guessing that someone was correcting for some sag in the middle. That does not make me feel very good about the integrity of the cross members. The few that I have looked at so far do not seem to have any major rust so I do not really know what this is all about. Has anyone else seen this type of thing? If I need to replace any of these cross members where can I find stamped metal with holes in it like what is there now?

5.) Some of the floor panels are held down by self-drilling and taping screws while some places have the elevetor bolts that I thought was more typical of the factory installation. Did the factory use a mix of methods or is this some work from a PO?

6.) I am beginning to lean in favor of a full floor replacement along with some frame repair. This may or may not mean I will have to do a body off session depending on the amount of repair needed. I did notice that the frame cross-members did not seem to be all that securly held in place. Are they even welded or are they just wedged into place?

Well enough rambling for now. It is time to get to bed and dream about a possible out of body experience.


BobbyW 06-06-2004 09:24 AM

Yep. They used screws when you would think bolts would only be used. I used bolts only during my replacement. Took longer but will hold better.

I found no thru frame and shell bolting at all.

The shimming in the center is common during assembly. Mine was 3/8" and 5/8"

markdoane 06-06-2004 10:54 AM

Here are some answers, but these are all based on my 1959 model. I expect that your later model may be different.
1. The U-channel was bolted through the floor at each outrigger. There were lots of little 1" pan head sheet metal screws also, for the areas between outriggers. There was nothing under the floor to bolt through in those areas.
2. The frame bows were riveted to the floor channel, and the channel was bolted (at outriggers) and screwed (between outriggers).
3. There are no frame rails between the outriggers. Heck, in my 1959, there isn't even the channel that protects the edge of the plywood. That's a later innovation. Again, my model is a 1959 and a lot older than yours.
4. There were no shims anywhere under the floor. The crossmembers in 1959 were solid steel without the 'slots' common in the later models. I think I would just use solid 14 ga. steel, and add a few passage holes if required for wiring or plumbing.
5. I didn't run into any self-tapping screws. Just about 100 elevator bolts.
6. Crossmembers should definitely be welded. They were only welded on the inside, so welds may not be obvious from the outside of the channel.

Good luck and keep us informed.

The Farm 06-06-2004 11:43 AM

My husband is up in the shed pulling up all the rotten flooring (back end) on our '64 Trail Wind...we are keeping a log of hours...why I don't know. I am running up to talk to him and get him to read the stuff Malconium wrote. It looks like ours has rot only in back. Like many people who have bought things thinking it was a quick-clean job and off we go? We are totally renovating. Taking the bathroom out was fun. Taking the closet out to get the bathroom out was fun. Taking the folding door sldie out to get the closet out to get the bathroom out was fun. Now we have gutted the sewer pipes/stacks, gutted the plumbing. trying to get the water heater out...(how did they get that sucker in?). And every day I ask myself...are we having fun yet?
We are 1st time Airstream owners, okay we are 1st time travel trailer owners. Have we gotten ourselves into something of a nightmare?
What is the common belief on refinshing the cabinets? Looks like our had a 'pickled' finish. White wash? Anyone have a finish like that? Can we strip them and re-'pickle'? They are fairly gross. Tried Tung Oil but it doesn't do anything for the used look. We are aiming for as close to the original look as possible.

Ken J 06-06-2004 01:14 PM

The floor should not have self tapping screws - my guess is those are from a previous repair.


malconium 06-06-2004 03:20 PM

Water heater removal...
I just took out my water heater yesterday. Your unit is older than mine so it could be different but here is what I found. The whole water heater is held in place by screws that go all the way around the outside flange of the water heater. This includes along the bottom edge of the flange which was in my case behind the rub-rail trim strip just below the water heater. I had to drill out enough rivits on the rail to be able to flex it down a bit so I could get to those screws. I also found that I had to not only disconnect the gas line but I had to pull it all the way out the bottom of the water heater enclosure since it would have prevented sliding the heater out. Once the water lines were disconnected, the gas line pulled out and the screws all removed I was able to slide the water heater out (toward the outside of the trailer). It was a snug fit so I had to wiggle it back and forth a bit before it made it all the way. Also I had to run a putty knife around the edges to break loose the various types of sealer that had been used under and around the flange.

I know what you mean about your restoration project growing. I at least started with a trailer that had a lot of the interior already removed. I am not entirely sure now whether that was better or worse. I have had to guess at how some of the things used to be. A very big help was to get a copy of the 1973 shop manual. It clued me in quite a bit as to where to look for things and what to expect. Fortunately I do not feel any strong compulstion to build the trailer back to its original state but like the idea of customizing it to suit us.

I think the fun part will come into play later when you get to brag that you did it all yourself - at least that is what I am hoping for.


malconium 06-06-2004 03:26 PM

Some more questions...
So if shimming was common the fact that I have some may not mean that the cross members need to be replaced? How do I decide what to replace (other than for obviouse rust deterioration?

If I do replace any of the cross members would it be OK to torch weld them rather than electric welding? I currently have access to a torch but not an arc welder. Would they have to be completely welded or is tack welding enough? The couple that I have looked at so far do not seem to be all that well attached.

Is the c-channel at the edge of the plywood a separate piece or is it part of the u-channel above?



malconium 06-06-2004 03:31 PM

Would self drilling/taping screws be OK?
Any thoughts about the viability of the self-drilling and taping screws for holding the new flooring down once I get around to installing it? I could at least install them all from above. With the elevator bolts I would have to do some of the work from above and some from below and this, of course, assumes that I have adequate access from below too.

markdoane 06-06-2004 04:33 PM

There waas a pretty thorough discussion here:

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