Promaster RV Design and Construction
The Design Starting Point
The starting point for my design was the classic "rear bath" design that's been used in Winnebago Travatos and in Hymer Carrados for some time. This design is very open on the inside and still has ample storage.
I wanted to have a kitchen with microwave, cooktop, sink, refrigerator and drawers I wanted the living area to feel really airy and yet be easy to convert to eating or sleeping. I liked the idea that sleeping could be flexible as either twin beds or could be made up as a single king size bed.
I wanted the overhead storage to be ample for all kinds of gear and I wanted drawers under the bed for clothes. It was also important to have a wardrobe for hanging clothes since I planned to travel in the van for business.
Finally, the rear bath seemed ideal for a workable size shower with a sink and toilet.
Detailed Design in Sketchup
Rather than just starting to build cabinets, I like to start with rough designs in Sketchup and then refine those designs based on actual dimensions taken from the van. By doing detailed drawings I can make sure things will fit where I want them without having to rebuild or modify finished cabinets.
Once the drawings have been finalized, I then use the drawings to make cutting plans for the materials. This makes construction much faster and more accurate since the cabinets have already been built on paper. It is important in this step to make sure that actual dimensions of the materials are used. Nowadays, it's common for plywood and other materials to be dimentioned in millimeters rather than inches. The difference between 3/4" and say, 20mm is small but it makes a lot of difference when doing things like drawer slides that require a precise width in order to work correctly.
Trial Fit In Virtual Van
In previous van builds, I've found it helpful to actually see what the design looks like inside a virtual van. I was able to find a fairly accurate Promaster drawing in the Sketchup Library and modify it enough to be accurate for my test purposes.
Once all cabinets and parts have been placed in my drawing, I group them together and transfer them into the virtual van.
Once all the cabinets, tanks, water heater and other parts are installed in the virtual van, I usually do a virtual walk-through to see if things look like I want them to. This is also the time to determine if headroom, isle widths and door sizes are going to work as designed.
From this point I usually proceed to the construction phase.
It's not my purpose to detail the construction process in this post. Rather, I'll just give some overview steps and mention various materials I use when building vans.
The first step for me is putting in the electrical and any plumbing or other stuff that needs to run through the walls and ceiling. After that, the insulation goes in. I use 1/2" polyiso insulation under the 3/4" tongue and groove flooring OSB. On the ceiling I use foil faced polyiso in 1.5" and 2" thickness and on the walls I use 2" polyiso board. In any voids where the foam can't be fit, I infill with standard fiberglass insulation.
Next the floor is installed and after that, the ceiling. On this van I used 1/4" melamine panels on the ceiling which makes the ceiling both attractive and durable. For the wall panels, I use 1/8" underlayment plywood covered with marine vinyl. The same marine vinyl can wap columns and other exposed body areas to give a finished look. The marine vinyl is durable and easy to clean. LED ceiling lights are installed next.
Then I cut the openings for the windows. The holes are cut through the installed insulation too. The clamp rings for the windows serve to hold the wall panels in place along with several screws hidden behind the cabinets. I also installed the power roof vent at this point.
Next the cabinets are installed and fastened to the flooring. Flooring is fastened down at various points through the van floor so fastening the cabinets to the floor makes a very rigid installation. All cabinets are also fastened to the van structure using both sheet metal screws and rivet-nuts.
With cabinets installed, I move to all the utilities like fresh and grey water tanks, hot water heater, water pump etc. Finally all electrical is finished up and any other required finish work is performed. Overall construction of this van took about one month working part time.
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