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Old 06-04-2004, 08:37 PM   #1
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1973 31' Sovereign
Portland , Oregon
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Question Plastic inner skin on 1973 Sovereign?

Boy am I puzzled!?

I have been dismanteling my 1973 31' Sovereign with an eye on floor repair or replacement. I had a few minutes to kill before supper so I started to loosen the lower inner skin on the curb side so I could get to the channel at the base of the wall. To my surprise this panel looks for all the world like it is plastic and not aluminum! Besides not sounding like metal when I tap it it is white on the back side. I also noticed that the way the side panels overlap each other from top to bottom of the trailer does not conform to what I saw in my copied 1973 service manual. The manual indicates that the second sheet up should be behind the edge of the bottom sheet. I thought when I saw that in my manual that this would be a good way to keep any water in the wall from leaking through the horizontal wall seams. My wall panels are consistently not the way the manual shows them.

What gives here anyway? Is this normal for a 1973 31' Sorvereign International? The wall panels look like they have been there for at least 31 years so it is hard to imagine that someone re-did the walls since the trailer was made. And what about all the hupla that I have read in the forums about the inner skin being an important structural element? This panel did not seem to be held on with all that many rivets and I doubt that if it is 31 year old plastic that it has anywhere near the tensil strength of aluminum.



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Old 06-05-2004, 04:23 AM   #2
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First I do know that the Service Manuals are not gospel.
Changes are sometimes made in production after printing, and sometimes I think laziness or time constraints entered in and older proofs could have been used to illustrate instead of using up-to-date drawings perhaps.
On the whole though most of my findings have been that the manual is more right than wrong.

I do not think plastic was ever used as the stock wall except in the bathrooms where ABS plastic is evident in some places.

Is it possible that what you found is FRP (fiberglass reinforced panel)?
Sort of a peblegrained sheeting that you see in many rest rooms and commercial kitchens? If so it is undoubedly a refurb by a previous owner. Not that FRP is necessarily a bad idea. Lightweight, tough as nails, cleanable, etc.
However I don't recall if rivets would work well without tearing out due to shifting during travel...Seems like rosettes are used with FRP but I am not sure.
Here is a good link regards to FRP:

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Old 06-05-2004, 11:17 AM   #3
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LOST , Hawaii
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How thick is the panel? I doubt if you will commonly find any .032 plastic.

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Old 06-05-2004, 11:22 AM   #4
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1973 31' Sovereign
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It could be FRP

I will be taking a closer look at the paneling today. I know about FRP and it could be some form of FRP. It does appear to have a texture that is molded in. I am going to have to check and see if this stuff is used everywhere or just in some places. This particular piece would have been mostly behind the wardrobe and kitchen counter but some of it is in the back bedroom. It also is a fairly long piece - definitely more than 8' long. Interestingly enough the curb side of the trailer where this panel is does seem to have some problems with the attachment to the frame. The body appears to be bowed out as much as 1" along the area between the entry door and the back side window. There is also some floor rot along this same line. I am hoping that I will not find a lot of rusted frame down below. Working on that area is going to be a main focus today.

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Old 06-05-2004, 11:26 AM   #5
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1973 31' Sovereign
Portland , Oregon
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Not sure how thick...

I will have to measure it today when I take a closer look at it. When I was unriviting it I was thinking it was an aluminum panel with the vinyl skin on it. It did not impress me as being a lot thicker than what I was expecting the aluminum and vinyl to be.

I am going to working most of today on the trailer so I will post more information this evening on my findings.

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Old 06-06-2004, 12:26 AM   #6
Rivet Master
1973 31' Sovereign
Portland , Oregon
Join Date: May 2004
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Unhappy It was a false alarm after all...

I took a closer look at the paneling and found out that it was indeed aluminum. I think that what threw me off was that the back side of the paneling is white. I was expecting it to be shiny aluminum. The only thing I can think of is that the white back side had something to do the process of putting on the textured surface on the other side.

Does anyone have any information about this? Is white on the back side normal?

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Old 06-06-2004, 05:34 AM   #7
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1975 31' Sovereign
1980 31' Excella II
Sprung Leak , North Carolina
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Yes it is

I have a 75 and the interior panels have the paint on the backside. It is called a wash coat and usually appears on all painted metals.

Wash coat:
a primer, typically provided on the back side of painted metal products to help protect the underlying metal from wear and corrosion.
NRCA Roofing & Waterproofing Manual, Fifth Edition


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