If you are a practitioner in the RV industry, you must know something about the sandwich body structure. If you are a RV enthusiast, you must be wondering how such a thin and light body can take on the functions of heat preservation, sound insulation and support? How many philosophies do you not understand contained in the structure of this inch?
What is a “sandwich”
Sandwiches, a common food in Western countries, are usually made of two slices of bread with a few slices of ham, cheese and various seasonings. The body structure of a RV is usually composed of three materials: “external plate + interlayer material + internal plate”, so it is called a sandwich body structure. The sandwich body structure is generally used for the side walls and roof of the RV. The purpose is to support the wall, heat preservation, sound insulation, and protect the interior of the RV from external interference. Because it undertakes so many functions, and the RV pursues the ultimate lightweight, it is difficult for a single material to meet many requirements, so the sandwich body structure came into being.
The sandwich body structure sounds simple, but in reality it is much more complicated. First of all, as a body structure, there must be a skeleton, and the lightweight wooden structure has become the first choice. It can also be said that the wooden frame is the basis of the sandwich body. The second is the external material, which generally uses high-strength, light-weight fiberglass or aluminum-plastic panels. Then there is the interlayer in the middle, which bears the functions of heat preservation and sound insulation, so polystyrene foam boards are generally used for filling. Finally, these materials are bonded with an adhesive.
Different “cooking” techniques
At present, imported RVs and domestic RVs in the domestic market generally adopt a sandwich body structure, but what is the difference? Let’s start with the European RV that I am most familiar with. The sandwich body of the European RV is usually made in one piece. Large plates are hoisted by machines, and small materials are placed manually by laser positioning. The adhesive is evenly spread by the machine, and the whole production process is completed by only 2 workers except the machine.
In terms of material selection, there are many differences in the polystyrene foam board filled in the middle. The common white polystyrene foam board is used as the basic material. With the improvement of density, hardness and other data, there are higher levels of pink, blue and black. As for the surface material, most European RVs only use FRP materials on the roof, which can make the RV more durable and can also cope with extreme weather such as hail. The body is made of aluminum-plastic material, which makes the caravan easier to take care of, especially when there are minor scratches, it can be repaired like new with simple polishing and waxing.
Such a car body structure also brings other problems. Because European RVs emphasize lightness too much, the walls are not resistant to collisions. A minor accident will cause the RV to be repaired in the factory. Especially according to the thinking mode of the Germans, if there is a problem with the wall of the RV, the entire wall must be replaced, otherwise the sealing and load-bearing requirements will not be met. However, there are basically no conditions to do so in China at present. More reference is made to the maintenance experience in other regions, and only the damaged parts are cut and replaced.
American RVs focus more on handicrafts and emphasize handmade. Therefore, sandwich body materials are often pieced together bit by bit by people, glued by hand, and bound by hand. Manual work can be meticulous, but manual work also increases the chances of making mistakes. As far as the outermost material is concerned, American RVs like to use FRP as the external material of the body, which also makes American RVs more calm in the face of severe weather such as hail, and can even easily deal with small stones that bounced while driving. Moreover, FRP is the same as the aluminum-plastic material of European RVs, which can achieve minor scratches, polishing, waxing and restoration.