In this installment of my series documenting my DIY overland trailer build, I’ll share how I clad the trailer with an aluminum skin, painted it, and weatherproofed it. At the end of this phase, had a basic working trailer, an enclosed box on wheels that could be towed behind my Jeep.
Why Aluminum Cladding
I opted to use aluminum for the trailer’s skin, mostly because I wanted to reduce the trailer’s overall weight. Aluminum is quite a bit lighter and more corrosion-resistant than mild steel, and the majority of camper trailers and RVs on the market use aluminum cladding.
For the sides of the trailer, I used a 14 gauge aluminum sheet (0.0641 inches; 1.63 mm), which seemed sturdy enough for supporting the weight of cargo. For the sides and front, I used 18 gauge aluminum sheeting (0.0403 inches; 1.02 mm). For the top, I used a 14 gauge diamond plate aluminum sheet, so that friction from the diamond plate pattern would help hold cargo in place on the roof of the trailer.
Before we go any future, in case you prefer video over print, here is a video that covers this step of the build:
Painting the Frame
Before I attached the aluminum cladding to the trailer, I painted the frame. There are many options for painting mild steel. After a lot of research, I decided to go with Rustoleum self-etching automotive primer as the first coat and a basic Rustoleum gloss protective paint for the top coats.
There are more durable paints on the market for use with metal, but the convenience of Rustoleum was appealing. As I use the trailer and need to repaint it, finding Rustoleum products is really easy, as they are carried at most hardware stores.
I opted to use rattle cans instead of roll-on paint because I had so many inside corners to paint on the trailer frame. It seemed more effective and less messy to use spray paint.
My painting setup wasn’t ideal. I rolled the trailer onto my driveway and painted it in the open air. The main challenge was that there was often a breeze blowing outside, so it was hard to control the spray. The paint job looks okay, but far from professional.
It would have been better to paint it inside my garage, but I didn’t want to deal with venting the fumes and taping plastic around the paint area to protect things we store in the garage. I wore a respirator and nitrile gloves when painting. I should have worn a long sleeve shirt or painters jacket, as the paint often got on my forearms.
All that said, the paint job looks okay and I can touch up easily as the trailer gets roughed up on the trail.
Attaching the Cladding (aka The Skin)
I dithered for quite a while on how to affix the trailer’s cladding to the frame. There are a number of ways to do so, including using self-tapping screws, rivets, and industrial strength adhesives, and super strong tapes (another kind of adhesive).
After doing quite a bit of research – and overcoming some initial skepticism – I opted for using a tape to attach the skin. Namely, I used 1-inch wide 3M VHB Tape (4991), a double-sided foam tape made from high-performance acrylic adhesives. A 36-yard roll was just enough to finish my trailer.
If you are hearing about these tapes for the first time, you may be asking the same question I had: can a tape really be trusted to hold together a trailer moving at 70 miles an hour down the road? The short answer is yes.
VHB tape is used for a variety of industrial applications, including holding glass and siding on skyscrapers. It’s also very common nowadays in commercially built RVs. In fact, after learning how sturdy they were, my primary concern was that I would accidentally affix the skin incorrectly and not be able to remove it easily to correct the placement.
One of the major benefits of using foam tape was that it would keep my steel frame and aluminum skin physically separated, which would help prevent galvanic corrosion. Galvanic corrosion is a type of corrosion that occurs when two different metals are in contact with each other in the presence of an electrolyte. The reason for this is that the two metals form a battery, with one metal acting as the anode and the other metal acting as the cathode.
Galvanic corrosion can be a major problem for structures that are made of multiple metals, such as bridges and ships — and overland trailers. Separating the metals with paint and adhesive tape prevents electrical current from flowing between them. While painting the two metals will help prevent this type of corrosion, VHB tape provided a much greater degree of protection.
Another advantage of using VHB tape is that the tape helps weather seal the cargo box. I’ve also heard that the tape is quieter and more reliable, as screws and rivets may rattle loose. As you can tell, I’m a fan.
The tape is double-sided, so you can apply it to one surface first, then remove the protective film and connect the other. I put the tape on overland trailer frame and pressed it down with a skateboard wheel attached to a skateboard truck. Later, I bought a real rubber roller intended for this purpose, which I used for applying the tape. The tape needs to be pressed down with a roller to fully wet it out.
After the tape was in place and pressed down, I removed film from one edge of the frame, and then attached the cladding panel very carfully. Once it was attached at one angle, I progressively remove the protective film and press the panel against the tape, moving from one side to the other. In this way, I attached the floor panel first, then the side panels, then the front panel.
The only place I ran into some trouble with was the front panel, where I accidentally touched the panel to the tape before I was ready to seat it. Before I knew it, the panel was partially sticking to the tape and in the wrong position. All I could do at that point was to pull the panel off – I still had leverage since only one spot was stuck. Then I had to peel the tape from the frame and replace it.
For the floor panel, gravity helped press it down on the tape and I placed some heavy crates around the surface to weight it down further. For the side and front panels, this wasn’t possible, so I used clamps (C clamps and spring clamps) to pinch the panel to the frame.
Rubberizing the Cargo Box Interior
I initially thought about leaving the aluminum on the inside of the trailer bare, with not paint covering it. But ask I worked with the aluminum and it got scratches on it, I decided that a rubberized paint would help protect it and prevent cargo from sliding around.
My first thought was to use Rhino Liner, which is a popopular rubberizing paint used for pickup truck beds. But I had no luck finding it sold at a retailer in San Diego and didn’t want to wait for an online order to arrive. So I ended up using another Rustoleum Truck Bed Coating, another rubberized paint. While I suspect this paint isn’t as thick and durable as Rhino Liner, it has so far worked pretty well, though I’ve needed to touch it up in places.
Before painting the interior, I added two peices of aluminum angle to help secure the side panels on the trailer. This was needed because I added the aluminum panels on the inside of the frame, which meant that the bottom of the panels was sitting on the floor panel, but not connected in any way.
I taped the aluminum angle strips to the floor on one side and the side panels on the other. The need to do this is one reason why, if I were to do the project over, I would figure out how to attach the side panels to the outside of the frame and then the fenders outside of that (see my last post on adding the fenders for a more indepth discussion).
To apply the rubberized Rustoleum paint, I cleaned the aluminum skin with mineral spirits and taped off the trailer frame members before painting (the truck bed paint is black and the frame paint gray). It took about four or five cans of the Rustoleum to coat the floor and sides of the trailer. I wore a respirator and nitrile gloves while panting.
Roof and Trim
I waited until I’d painted the inside of the cargo box before attaching the roof, as having the top open made panting easier. Attaching the diamond plate sheet for the roof was relatively easy, but did require cutting the sheet to size using a skill saw and a Diablo Steel Demon blade. I used the VHB tape for the roof, just as I had for the other cladding panels.
After attaching the roof, cut out aluminum trim for the corners of the box for protection and to help seal out water from rain and snow. For the trim, I used 1 x 1 aluminum angle from my local metal store. The trim had to have sections cut out to accomodate the roof-track towers and other features, such as door hinges.
I attached the trim with Sikaflex 221, a multipurpose polyurathane sealant and anhesive popular in the RV industry. The Sikaflex worked well to hold the trim to the trailer and also provided another layer of weather sealing.
After gluing all of the trim on the trailer, I masked the damonplate on top and other unpainted areas. Then I painted the trim with the same Rustoleum primer and paint I’d used on the trailer frame and the outside of the panels.
Once the trime paint dried, I remove the masking and the basic trailer box was essentially done. There were a number of other steps ahead to finish, but it felt good to have trailer that could be driven behind a vehicle and hold cargo.
To drive it on the road legally, I still needed to get it registered with the state. And to do that, I had to install lights and electrical connections to my Jeep. That will be the focus of the next installment of my DIY overland trailer build series.