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Trail Wagons Inc./Chinook RV has switched from fiberglass to all-composite shells and floors for its Class C motorhomes, according to Composites World magazine.
The Yakima, Wash.-based company had used one-piece molded fiberglass shells consisting of gel coat, ceramic shield and a single polyester skin laminate with plywood-stiffening panels since 1971. But last year, it switched to a lightweight sandwich construction featuring a vinyl ester resin composite recommended by Eastman Chemical Co. of Kingsport, Tenn., Composites World reports.
The composite shells are stable from well below freezing to 110 degrees to prevent blistering and cracking.
“After just one year of using the new shells, the results have been astounding, none of the new RVs have shown a single stress crack,” said Jeff Gaskell, Chinook’s fiberglass division manager.
The composite shells are used for Chinook’s 21- and 24-foot models and are gel-coated and include 0.5-inch-thick closed-cell PVC structural foam from DIAB Inc. of Desoto, Tex.
For Chinook’s 25- and 27-foot models, Gaskell needed to reduce floor weight to avoid exceeding the chassis’ gross vehicle weight rating (GVWR). So, instead of using laminated 1.5-inch plywood with polyester resin/glass-laminated bottoms, he switched to a new floor design featuring sandwich construction, Composites World reports.
Skins of quadraxial glass fabric from Vectorply of Phenix City, Ala., are layered in a flat mold on both sides of DIAB balsa core that come pre-cut to size. Then, 16 gallons of Eastman’s vinyl ester resin are used to infuse an entire vacuum-bagged 25-foot floor, optimizing the glass-to-resin ratio, eliminating waste from overspray and resulting in 15% resin savings.
The floor is ready for demolding after only two hours and reduces styrene emissions nearly 100%.
“The process has reduced the floor weight by 35% and increased compression, tensile and sheer strength by 300%, enabling us to expand motorhome size,” Gaskell told the magazine.
Gaskell now plans to vacuum-infuse shells as well and is experimenting with using light resin transfer molding to replace open molding for smaller parts, such as storage compartment doors, running boards and shower components.