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Old 07-31-2004, 11:01 PM   #1
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Final Floor Replacement Technique

Weight calculations on this are off as I discovered after a discussion with others. Please page down as the idea has improved and the weight calculations are correct further down.

I have read almost every thread that states anything about floor replacement and am happy that this community of people help each other as much as they do.There are a lot of threads that have plenty of information, and I am only placing this thread up because of it being a new idea. I would really appreciate eveyone giving me their thoughts here.
I for one have learned a lot for Malconium’s thread “Body and banana wrap on floor replacement technique.” http://www.airforums.com/forums/showthread.php?t=11818&highlight=technique This technique inspired some ideas of my own.
I have found what appears to be the very beginning of the well known Frame Separation on my 1975 Sovereign. Since nobody wants to have to do this type job the first time, the idea of ever having to do it again keeps you up at night trying to figure a way to do the ultimate job.

I have taken Malconium’s drawing and did a few modifications. I have done a little research on the differences between Aluminium and Marine Plywood which is what is currently in my AS. The thickness is ¾”

The idea is still up in the air so I thought I would ask everyone that will comment on it to let me know any thoughts either pro or con.

Of course the interior flooring must be removed, the cut-outs completed, and the piece cut to the correct size. Frame members that are in need of replacement are replaced and so forth. Normal floor replacement techniques are used up to this point. Then we can go on to my idea.

The Idea

The idea is to start with an aluminium sheet 48 X 96 at ¼” thickness and after it is cut to the correct size and all cut-outs are made the sheet is slid into place. Since it is aluminium and the main frame is steel an insulation tape like butyl tape must be used to separate the aluminium sheet from the steel frame members.

Once it is in place aluminium bar stock of the same grade is used. These are 3” wide by ½” and length is determined by where the piece is to be installed. The only long pieces of this stock are the 2 approximate 96” pieces used at the joining edge and the rear edge of the floor, and the other 4 pieces are fit into place as dictated by the floor itself. These pieces are knocked or pressed into place making certain not to distort the body in any way as they must lay in as the original floor did, and then once they are in place they are welded to the ¼” aluminium sheet from inside the trailer. The 2 inner pieces of stock must lay directly over the main frame of the trailer, and the bolt holes should be predrilled and countersunk in each.

Next, the wood sub floor panels at ½” thickness(Marine Plywood or at minimum an AC exterior plywood should be used) are placed in the openings and epoxy bonded to the aluminium. Weight should be used to assure an overall bond (100 lbs per panel should be adequate) Elevator bolts will also be installed to assist in maintaining the bond.

Once this step is complete you are ready to install the aluminium sub supports. These pieces are 6” wide and ½” to ¾” thick. The weight difference is .0123697 lbs per sq inch. I have figured my weight using a piece of ¾” here. These pieces will not be welded. They are only attached by the floor bolts and the bolts to the C-channel (using predrilled pieces would probably be desirable here) Once they have been installed finish by installing the rest of the bolts necessary to hold the floor to the frame, and then complete installing the elevator bolts through the wood sub floor and aluminium sub floor.

Lastly, just prior to placing the belly pan back on it might be a good idea to spray an undercoat on the entire sub floor to kind of seal it from any oxidation.

I have attached the photo that I modified which probably will go a long way toward explaining this technique.

I am seriously considering this and IMHO it may eliminate ever having to replace the floor again.

The tensile strength of aluminium is far greater than marine plywood, and some grades can even compare to mild steel. Aluminium has the advantage of never rotting, thus one would never have to do a section of flooring because the toilet has rotted the floor out, and of course this may totally eliminate the need to ever worry about frame separation again.

Now I would appreciate it if any member would pipe up and tell me any negatives they can think of, and as well I would appreciate hearing any encouraging ideas too. I will probably bump this thread up for a time to get all the imput that I can and for this I apologize.

Your time in assisting me is greatly appreciated here………………..
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Old 08-01-2004, 07:35 AM   #2
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$$ and weight. Aluminum is very expensive when you start buying sheets and bars. Check your weight calculations, a 4x8 sheet of 1/4" 6061 weighs 113 lbs. 8 sheets for the underlay is going to weigh 900 lbs, plus nearly 2/3 of the weight of the wood floor, plus the aluminum used for spacing.

Why not eliminate the plywood completely? Put the aluminum sheet on top of the spacers you are using in the side track and above the frame rails, no well to fill with wood. 1/8" with stiffeners would be more than thick enough and lighter. It still won't be cheap.

John
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Old 08-01-2004, 01:38 PM   #3
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Yes you are correct on the weight of a sheet. I did make a mistake there I was looking at a 1/8" weight and mistakingly figured it that way figuring 57 lbs per sheet.
This does change things a bit, And I do like that idea a bit better also. That is one great thing that these forums provide.

Okay, so if we go with 1/8" of 6061 we will have 57 pounds. Placing the spacers of solid bar on the bottom at the needed space of 5/8" to make a 3/4" space around the edges and on top of the frame will add 8.82 pounds per sq ft. of material used. This should also work well for the aluminium sub suppot as pictured above(6" piece)

I will re-calculate and do an update on the above drawing. Let me ask you, how many stiffiners do you think we will need to stiffin the 1/8" sheet so it will be stiff and sturdy? Also what size should the stiffiners be, I am thinking just off the top of my head of aluminium tube for the stiffiners, Will that work?

Thanks for helping...........................
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Old 08-01-2004, 01:41 PM   #4
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Also is 6061 the best choice here?
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Old 08-01-2004, 01:57 PM   #5
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Talking Fwiw

Airstream tried a composite floor in the Argosies way back when. IIRC there are a couple of owners on the board that have the aluminum composite floor. Seems that one of the issues was a dipping between the stiffiners. Apparently not a structural issue but a cosmetic and apparently an issue when it came time to put down new floor covering. But that was around 30 years ago and technology may have improved the available materials to the point where it is an idea that could be revisited.

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Old 08-01-2004, 02:32 PM   #6
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Quote:
Originally Posted by wahoonc
Airstream tried a composite floor in the Argosies way back when. IIRC there are a couple of owners on the board that have the aluminum composite floor. Seems that one of the issues was a dipping between the stiffiners. Apparently not a structural issue but a cosmetic and apparently an issue when it came time to put down new floor covering. But that was around 30 years ago and technology may have improved the available materials to the point where it is an idea that could be revisited.

Aaron
Seems that one of the issues was a dipping between the stiffiners.
This would be my concern also. Do you happen to know how far the space was between the stifiners?
The problem seems like it can be eliminated by just not allowing much room for the space to sag. Say if stiffiners were spaced at no more than 6" An aluminium tube Heavy Wall with an OD of 5/8" X 2" welded on both sides to the sheet seems like it would be very stiff.
What would be the best aluminium to use for this project?
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Old 08-01-2004, 03:15 PM   #7
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OK - New Modifications

The stiffiners would all be welded on both sides to the aluminium sheet. The solid stock is also welded to the sheet, but only on the inner side. I had to go to 3/4" X 3/4 " with a wall of .125 for these.

This will reduce the weight considerably. I will try to figure its total and relate the comparason to this and Marine Plywood.

If anyone else has ideas please pipe up.................................
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Old 08-01-2004, 03:15 PM   #8
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The floor used was thinner sheet and foam composite, understandable that it would not last over time.

Cheap easy stiffeners are 1x1x1/8" angle, lay them so the open part is flat against the floor. Best way would be a 'X' but then you have to cut a bunch of 45 degree angles where they meet. Easiest would be to just run a couple parallel in each cavity.

You don't really need the sub support and the curves are going to be killers to machine, I would dump that part.

John
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Old 08-01-2004, 04:31 PM   #9
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I agree with removing the sub support. However I think tube would give greater support than then angle because the weight is working against a common point by using angle in that manner.

I have the new modifications in the drawing below and also a table of weight

1 - Aluminum sheet 48 X 96 X .125 = 56.45 lbs
2 – Solid Stock 96” X 3” X .625 = 35.28 lbs
4 – Solid Stock 42” X 3” X .625 = 30.87 lbs
12 – Tube .75 X .75 with .125 wall = 15.75 lbs
Welding weight = 5 lbs approximate
Total Weight = 143.35 lbs
Marine Plywood = 75 lbs
This method weighs 68.35 lbs more than using marine plywood
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Old 08-01-2004, 07:57 PM   #10
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we havent researched it yet but our bubble will need ,needs ?, a floor. my thoughts have been that pontoon boats switched to aluminum decking about 10 years ago, right after i bought mine with a marine plywood deck. has anyone looked at the construction used in the marine application and its longevity?? if it's been discussed please point us in the right direction.
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Old 08-02-2004, 02:14 AM   #11
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I have not looked into marine constructio techniques very much. I do have a boat, but it is made of fiberglass and all I have ever had to do is the occasional mend to places that roadstones have damaged.
My AS has 3/4" marine plywood in the rear and most likely throughout. I would assume that AS used marine plywood since it was one of the highest quality items for this application. My wanting to change to this aluminum floor is only to prevent ever having to replace the rear floor again in my lifetime.
If you come up with any details please post them as they can be helpful.
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Old 08-02-2004, 08:16 AM   #12
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our thoughts exactly John G . if the application of marine aluminum decking is feasible then when i'm in my 100s i can still use my airstream ! were off to louisville this week for the nsra car show but when we return its off to the tracker boat factory in missouri, we'll let everyone know what we learn. my goal is a long life aluminum sub floor with a floating cork floor.
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Old 08-02-2004, 04:23 PM   #13
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Quote:
Originally Posted by roger n cindy
our thoughts exactly John G . if the application of marine aluminum decking is feasible then when i'm in my 100s i can still use my airstream ! were off to louisville this week for the nsra car show but when we return its off to the tracker boat factory in missouri, we'll let everyone know what we learn. my goal is a long life aluminum sub floor with a floating cork floor.
roger n cindy
I would be very interested in what you find out. I think the aluminum floor would be the way to go when a person has to do a replacement since it is not too much heavier than using the marine plywood, less than 75 pounds, and I don't think an additional 75 pounds should pose any problem even in the rear of the trailer. I would not expect that the AS engineers designed it at the bear minimum, but one never knows since some units have experienced Frame Sag in the rear and this would say that there was a flaw in the engineering.



Anyway I will need a lot more feedback on this design before I jump into it as this is going to cost a bit more than repairing with marine plywood. However, comparatively the cost seems small when you look at spending 1200 on an awning..................
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Old 08-02-2004, 04:48 PM   #14
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I'm no engineer...

John, I just revealed and replaced a section of my ply floor and was satisfied that 5/8" plywood over the exististing stanchions gives a pretty darn solid floor that has held up remarkably well after 35 years. I over-cut out the small section near the door (18" x 4'), (it probably could have been treated with 'rot doc' and filled). I was pleasantly surprised to find the floor under the gaucho to be very sound. I used the self tapping (high RPM) screws from Home depot to screw to the metal stanchion flange. I triple coated the plywood with S1 sealer and am confident I will get another 35 years out the floor.

I can totally understand your wanting to never have to do it again and therefore 'suck it up, spend the bucks and do it right the first time' but IMHO A/S did do a pretty good job the first time around, and 5/8" ply properly treated makes and excellent sub-floor.

Also I wanted to use it this season!!! and I have several other projects on the trailer to get to. We took it out last week and are planning to go for two weeks, leaving this weekend.

Good luck!

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