Sunrader interior wall structure

[snail powered]

Sunraders are rather different in structure versus many of the Toy Homes. Although they are of course not the only fiberglass Toyhomes around. The exterior skin of the vertical walls on the Sunrader is self supporting without the use of wood or metal framing under the skin. One factor to remember, the exterior walls of the Sunrader are not flat, there are many changes of contour in the surface.

The interior wall paneling is attached to the skin in only a very few locations. In most locations the furring strips behind the wall paneling is attached to the paneling itself rather than to the fiberglass shell. At the base of the wall panels in areas where it touches the flooring there are furring strips screwed to the floor and the paneling is stapled to those strips. Some areas the furring is pulled against the exterior fiberglass shell with screws from vent and hatch panels coming in from the outside. In the later models of Sunraders with rear dinettes the two support cleats for the seats are adhered to the exterior wall.

The trim ring clamps around the metal windows provides much stability of the wall panels as does securing the walls to the lower cabinets.

The styrafoam insulation is adhered to the back of the wall panels in the areas between the furring strips. In my 1980 Sunrader the foam insulation is 5/8" thick as are the particle board furring strips.

The upper cabinets are primarily supported by the ceiling panels. The lower, back edge of the upper cabinets is screwed into a 3/4" wide x 5/8 thick" furring strip that is attached to the back of the paneling but it is not adhered to the exterior wall. All the load of the back edge of the upper cabinets is transferred into the wall paneling. Putting a lot of weight in those upper cabinets is not a good idea. You are relying on a dozen or so screws to hold those cabinets up. The screws that go into the ceiling are only getting a grip into a 3/16" piece of plywood. You can see in this photo that the furring strip is not secured to the wall, only to the panel. The photo is taken at the location of the vent for the stove.

As the outer walls were already self supporting this method of interior wall panels with furring strips and insulation attached to them allowed the manufacture of the Sunrader to be cost effective. They could assemble most of the interior outside of the motorhome. Attaching the furring strips to the back of the wall paneling meant that only one thickness of furring strip was needed, 3/4". This method of construction worked best as the shell of the Sunrader is not flat due to the contouring along the upper and lower half of the shell's join line and the curvature of the shell at the join between the roof. In addition there is the curve under at the lower edge, at the rear corners, around the coach door and the angled slope of the walls which enabled it to be easily pulled from the mold. All those variations in surface depth would have meant creating a large number of custom sized pieces of furring. So instead they essentially floated the interior wall panels inside of the exterior shell. The upper cabinets helped push the top edge of the wall panels back against the exterior shell.

If one is going to remodel the interior of a Sunrader it is useful to know that you can quickly remove the old interior walls and cabinets and have essentially a clean slate to work with. The only prep work to be done is removing the sprayed on contact cement that stuck the carpeting to some of the walls and ceiling areas.

But do not tear out the ceiling panels if they are intact. That ceiling is a structural insulated panel system, a SIP, and it is very strong because of how it was put together at the factory. Replace the peeling or stained wall paper but leave the rest of it intact.

[jhjeff]

Thank you for this information. I'm looking at a 21 ft Sunrader remodel project where the entire rear interior has been removed, walls are completely stripped down to fiberglass and floor down to wood. Not sure if ceiling SIPS are intact or not, there was some water damage at rear roof vent, but still looks like there might be wood present, so perhaps panels have not been removed.

In looking at rebuilding in the rear do you have any thoughts on installing a lightweight but strong interior frame? Would it be worth the extra weight for the support? Not looking to overbuild/overload the vehicle as I'm aware of them already being heavy. 

If ceiling panels have been removed would putting SIPS back in be the best way to go, or is there a better way if starting from scratch? 

Have looked at some insulation options for walls (blue board panels, reflective air filled panels, spray foam), any feedback/thoughts? 

Thanks,

Jeff 

 

 

 

[86rader]

I have mentioned before what I did to the sidewalls of the cabover area of a sunrader. i glassed wood firing strips horizontally to th exterior wall, then fastened T&G cedar paneling. Cheap, easy, light and a big improvement looks wise. I don't see why this wouldn't work back aft.