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05-01-2016, 08:33 PM
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#1
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1 Rivet Member
1974 31' Sovereign
Cranbrook
, British Columbia
Join Date: Apr 2016
Posts: 7
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Can I use another product instead of interior skin?
Hello, new here. I recently acquired a 1974 Sovereign. It needed a full gutting. I am down to open frame, all vents, belly bands, wheel wells, gray and black water tanks out. All windows that open need new gaskets, the whole shebang. I was prepared for this, no worries. Frame is in decent shape, no separation in rear end, a little rot, will be re-enforcing with some new steel. I am planning on using lightweight t and g pine on the interior walls that are not covered up by cabinets, bed, appliances etc. I am planning on using the old interior skin for the areas that will be covered. I have saved the skin. For structural purposes do I have to use the skin everywhere? My idea was to used the wood panels with are 1/4 inch thick, then using a piece of painted steel bands that wrap around the interior and rivet them right through into the ribs for more strength. The top panel I will replace lightweight painted steel as well. Just want to know if this is feasible as I am trying to keep the weight down and don't want to put the inner skin back on behind the wood t and g. Thanks! Looking forward to the rebuild!
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05-01-2016, 10:53 PM
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#2
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Maniacal Engineer
1971 25' Tradewind
Lopez Island
, Washington
Join Date: Jan 2010
Posts: 1,244
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The interior skin is cosmetic, not structural as can be seen by the small number of pop rivets holding it in place. You can do whatever you like.
I'd make some test sandwiches of your wood & steel strips and see what sort of a result you get w/ pop rivets. You might also consider painting aluminum strips to get the same effect; there can be quite a bit of condensation in Airstreams and that steel may develop some rust after a while. Keep in mind, too, that Airstreams flex quite a bit, particularly vintage units; this will cause problems w/ your panels, just as it causes rivets to loosen in the interior w/ the original interior skins.
You will only be able to use the wood over the center part of the trailer; the ends of course have 3 dimensional curves.
- Bart
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05-02-2016, 12:14 AM
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#3
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Rivet Master
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton
, Arkansas
Join Date: Mar 2013
Posts: 5,868
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Can I use another product instead of interior skin?
In the scheme of things the Aluminum inner skin does not weigh that much, and it can provide attachment points for tour T&G anywhere... Kind of a plus sometimes.
As Barts stated above, the inner skins don't add any appreciable structure to the trailer, but a lot of folks here will disagree.
I put my 1/4" ply right over the aluminum, it allowed me to fasten it down anywhere I wanted.
Superat stultitia.
__________________
The fact that I am opinionated does not presuppose that I am wrong......
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05-02-2016, 11:52 PM
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#4
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Maniacal Engineer
1971 25' Tradewind
Lopez Island
, Washington
Join Date: Jan 2010
Posts: 1,244
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Quote:
Originally Posted by J. Morgan
I put my 1/4" ply right over the aluminum, it allowed me to fasten it down anywhere I wanted.
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Yup. We had one section where a previous owner had painted one wall; we covered that wall w/ 1/4" birch plywood and fastened it down w/ stainless finish washers and screws.
- Bart
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05-03-2016, 12:10 AM
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#5
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1 Rivet Member
1974 31' Sovereign
Cranbrook
, British Columbia
Join Date: Apr 2016
Posts: 7
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Thanks guys, this helps a lot! I very well could use aluminum strips for the bands and paint them. I was thinking of using olympic rivets to fasten these for solid support. I noticed when taking the inner skin out that many of the rivets were not even in the ribs, yay... So as for it being structural, I would agree that it would not give it much support. As for condensation, I have been working on some ideas for that...! Thanks again.
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05-03-2016, 07:15 AM
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#6
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Rivet Master
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton
, Arkansas
Join Date: Mar 2013
Posts: 5,868
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In my practical use in just about every kind of weather we get some condensation on the bathroom walls when we shower, but that is about it.
(Of course there is condensation on the windows at times)
Superat stultitia.
__________________
The fact that I am opinionated does not presuppose that I am wrong......
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05-03-2016, 11:19 AM
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#7
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Rivet Master
Airstream Dealer
Corona
, California
Join Date: Feb 2002
Posts: 16,497
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Quote:
Originally Posted by barts
The interior skin is cosmetic, not structural as can be seen by the small number of pop rivets holding it in place. You can do whatever you like.
I'd make some test sandwiches of your wood & steel strips and see what sort of a result you get w/ pop rivets. You might also consider painting aluminum strips to get the same effect; there can be quite a bit of condensation in Airstreams and that steel may develop some rust after a while. Keep in mind, too, that Airstreams flex quite a bit, particularly vintage units; this will cause problems w/ your panels, just as it causes rivets to loosen in the interior w/ the original interior skins.
You will only be able to use the wood over the center part of the trailer; the ends of course have 3 dimensional curves.
- Bart
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Bart.
I disagree.
The principle method of construction, is monocoque.
The shell is load bearing and must remain that way, so that the shell does not droop. The inner shell is just as important as the outer shell. The is especially true for the older trailers, that used .032 thick metal. Later years are using .040 thick metal, which makes the shell a little stronger.
If the inner sheet metal is not used, the backend of the shell, the longer the worse, will sag.
That was determined many years ago by the Insurance Division of Airstream.
If someone wants to rewall the interior, that's great. BUT, apply the new walls over the interior sheet metal.
If not, the shell strength will be compromised leading to eventual sag and outside wrinkles.
Andy
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05-03-2016, 01:02 PM
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#8
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3 Rivet Member
1979 31' Excella 500
Florida
, Florida
Join Date: Jul 2014
Posts: 119
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I agree with Andy,
The interior panels contribute to the overall structure, remove the curb side upper panel and the door wont close the same. Id put the Panels back on and cover it with wood where you want.
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05-03-2016, 01:57 PM
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#9
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3 Rivet Member
1948 16' Wee Wind
1964 26' Overlander
2007 19' Bambi
crossville
, Tennessee
Join Date: Jun 2006
Posts: 190
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I have 2 here that came in with interior skin off . 1 still had skin other cashed in to offset cost of new :-) both sagged over axles and major job to get back up where they belong . I AGREE WITH ANDY !!!!!!!!!
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05-03-2016, 01:57 PM
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#10
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2 Rivet Member
1975 31' Sovereign
West Liberty
, Kentucky
Join Date: Jun 2012
Posts: 93
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In an AS of that vintage the inner skin is metal with a covering on it. The skin acts as a ground when wiring 12 volt DC. This is handy when installing light fixtures, etc.
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05-03-2016, 05:40 PM
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#11
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:SPACE A" S/O 11 Air19745
2006 34' Classic S/O
Fort Worth
, Texas
Join Date: Feb 2007
Posts: 1,766
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Andy is right. Just look at non interior skinned aluminum trailers like Avion and SilverStreak, they will crack the outer skin near the upper front corners of the main entry doors. Airstream and Streamlines do not because of the added strength of the interior aluminum skin.
guskmg
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05-03-2016, 07:02 PM
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#12
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Rivet Master
1956 22' Flying Cloud
Durango
, Colorado
Join Date: Sep 2002
Location: 1975 25' Tradewind
Posts: 3,491
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I too absolutely agree with Andy - the interior skin provides great strength to the trailer - take off the interior skin and walk/jump around in your trailer and you will see how much the frame flexes - put the skin back in and see how stiff the frame becomes -
__________________
1956 Flying Cloud
Founder :
Four Corners Unit
Albuquerque National Balloon Fiesta
Rally
Vintage Trailer Academy - Formerly the original
restoration rally
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05-03-2016, 11:48 PM
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#13
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Maniacal Engineer
1971 25' Tradewind
Lopez Island
, Washington
Join Date: Jan 2010
Posts: 1,244
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In our '71, there are rivets fairly frequently in some areas... and none at all on other. These rivets are 1/8 aluminum pop rivets.
The exterior of the trailer forms a monocoque structure; the panels are riveted together and to the ribs - like an 1930's airplane in some ways. The frame of the trailer distributes the point loads from the axles through the floor into the c-channel and ribs, and thus the exterior skin.
The interior skin is not fastened often enough to prevent it from buckling and the rivets from breaking; when the trailer is driven over rough roads the interior pop rivets will shear over time as the trailer flexes. This is a common malady in Airstreams and happens because, while the interior skin might be stiff in some directions, it is not strong and it is not fastened in a structural manner to the ribs.
Note how close the rivets are spaced on the exterior of the Airstream; now examine the interior.
- Bart
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05-04-2016, 06:57 AM
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#14
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Rivet Master
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton
, Arkansas
Join Date: Mar 2013
Posts: 5,868
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Here is my opinion based on what a lot of folks will say does not exist, common sense.
Like Barts stated above, there are not enough attachment points, nor are the attachment points strong enough on the thin and relatively narrow interior skins for them to add a lot of structure to the entire trailer. I think they add perhaps between 5% and 10% to cabin strength.
But as I stated above, this is my opinion, but a thought out one.
That said, I did put my skins back in my trailer because it made sense for me to do so.
Superat stultitia.
__________________
The fact that I am opinionated does not presuppose that I am wrong......
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05-04-2016, 07:17 AM
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#15
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3 Rivet Member
2013 25' FB International
Liberty Corner
, New Jersey
Join Date: Mar 2014
Posts: 209
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Again, this is another situation that any serious manufacturer of a structure like an AS would have an engineering model. That model would show the stress distribution from which questions like this could be answered. Short of that, we are guessing or looking at similar past examples or something else like blame the tires.
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05-04-2016, 07:41 AM
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#16
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Rivet Master
1970 23' Safari
2005 30' Classic
1986 31' Sovereign
Lorain
, Ohio
Join Date: Dec 2005
Posts: 1,645
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As Andy literally "wrote the book" on Airstream damage and assessments, I think I'm gonna side with him on this discussion!
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05-04-2016, 10:32 AM
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#17
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Rivet Master
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton
, Arkansas
Join Date: Mar 2013
Posts: 5,868
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Quote:
Originally Posted by TheCabin
Again, this is another situation that any serious manufacturer of a structure like an AS would have an engineering model. That model would show the stress distribution from which questions like this could be answered. Short of that, we are guessing or looking at similar past examples or something else like blame the tires.
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There MIGHT have been an engineered model for the 70s trailers and maybe not.
Byum was not an engineer, however there might have been more engineering in the Beatrice era.
Even if there was significant engineering efforts in this era, I don't know of anything that says that the interior panels had to contribute more than five or ten percent to overall structure.
Superat stultitia.
__________________
The fact that I am opinionated does not presuppose that I am wrong......
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05-04-2016, 11:42 PM
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#18
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3 Rivet Member
1948 16' Wee Wind
1964 26' Overlander
2007 19' Bambi
crossville
, Tennessee
Join Date: Jun 2006
Posts: 190
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the reason the interior rivets pop out / shear from time to time is because they are under stress ! the stress is caused by the interior skin acquiring and supporting load!
that alone tells me that yes the interior skin helps support load . also 40 years of putting them back together has taught me a little.
as I said earlier I've seen the result of removal .
I don't think any engineer has looked at this construction since the big 1 and for the most part the construction hasn't changed . the exception to that are the ccd's without belly pans ( jc has a kit to reinforce the frames after they buckle )
take the skin out , do whatever you want it's your trailer ?
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05-05-2016, 01:17 PM
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#19
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3 Rivet Member
2013 25' FB International
Liberty Corner
, New Jersey
Join Date: Mar 2014
Posts: 209
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Are the internal rivets softer now than used years ago?
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05-05-2016, 03:15 PM
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#20
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Rivet Master
Airstream Dealer
Corona
, California
Join Date: Feb 2002
Posts: 16,497
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Quote:
Originally Posted by TheCabin
Are the internal rivets softer now than used years ago?
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Softer ? No.
Color difference. Yes
Old color. Ivory
New color. White or silver
Andy
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