… Cabin Rails — Fostering Adventure

Cabin Protection Rails

Something we Planned right from the beginning

If one looks at the original concept rendering that I created, the cabin protection rails are clearly visible. We’ve always known that sturdy protection rails would be needed, especially where we will be using the truck a good deal of the time. Our neck of the woods quite literally has an abundance of trees, and trees can be very hard on roof mounted equipment. Especially glass solar panels. And despite ones best efforts, it’s not always possible to judge the height of branches when they are starting to get close to the height of the truck.

Obstacles Created By the Build

Even though the information that we supplied to the builder clearly detailed the roof rails that we would add ourselves at a later date, the builder ignored it and placed mounts on the edge of the roof in locations that were in conflict with where we wanted to place the rail mounts. Because of this, we had to modify the way we were going to build the rails, and configure the mount placement so that they would not only miss the solar panels mounts, but also look symmetrical. Fortunately, we did manage to accomplish this.

This is the base layout design drawing we used to figure out the foot spacing.

Materials and Design

We wanted to maintain a consistent look with all that had been created so far. So unlike most expedition trucks that have round tube roof rails, we elected to build ours out of square tubing instead. We felt it would blend in with the body lines of the camper much better, and it would match the lift platform on the back of the truck.

Version 1, with brown coloured feet.

Version 2, with body coloured feet.

One of the considerations we had to decide on was what colour to make the rails, and more importantly, what colour to make the feet that attach to the camper box. Most roof rails are an accent colour, and the feet match the colour of the rails. This makes them really stand out on the box, something that really didn’t appeal to us. We knew the rails themselves would be the same brown colour as the rest of the metalwork on the truck. But did we go with body coloured feet, or rail coloured feet? To help us make the decision on the foot colour, we turned once again to the Photoshop, and created images of both versions of the rails with the different feet colours.

We were pretty sure which one we liked best, but just to be sure, we sent out the two images to a number of trusted friends, to get their feedback. Of the eight people that responded, seven liked the body coloured feet, and one preferred the brown feet. So the verdict was almost unanimous. Most chose the version we ourselves liked the best.

Method of Construction

Unlike most roof rail construction, which is an all welded design, we chose a different approach. Our design is one made of assembled components that are bolted together. The advantage of this is that it makes painting the feet a different colour than the rails much easier. But more than that, the modular design offers a superior end product. There’s no distortion of the rail because of the welding, the parts can be made to a higher precision tolerance, and if any rail or part is damaged because of an impact strike, it can be easily removed and repaired or remanufactured.

Our design allowed for larger feet than typical, and this has the benefit of a larger glue surface, so added strength. Although some truck builders use mechanical fasteners to attach the feet to the box, we have used a urethane glue product for the main adhesion. We did use two small wood screws on each foot, but these were simply to provide a finite location point that wouldn’t allow the foot to creep out of place while the glue was curing, and the screws were also used to pull the foot down onto the surface to create a uniform gap between the underside of the foot, and the fibreglass edge angle that holds the box panels together. Small pads located under the foot provided the gap spacing so every foot was the same, and the foot itself was glued square and parallel to the edge of the box.

Rail Design

Large gaps like these are a real liability.

A concern we had when looking at roof rails on other trucks was the gap that often existed between the various rail segments. These gaps could allow branches that are sliding along the rail to drop in between them and get caught. The subsequent damage that might occur as the truck continues to move could be of some consequence, and might even rip the rail completely off the truck. Of course if the gaps were very small, then the branches that might get caught would also be small, and may not be a problem. But we didn’t want to take that chance.

Our insert design still allows each section 1/4” for rail expansion due to thermal variation.

So in our design we incorporated inserts that spanned the joints between the rail sections. These inserts serve several functions. First, they do indeed prevent anything from getting caught between the rail sections. But more than that, they increase the strength of the rail system because any force exerted on one section is distributed across a larger area. The open ended design of our rails, which facilitates the use of the inserts, also allows the rails themselves to be used as a continuous wire chase for electrical lines, camera cables or whatever. It gives a us a fully enclosed raceway that stretches the full length of the camper box. So adding future electronics or accessories is quite easy.

The Build Progression

Step 1: The Feet

The painted foot ready for install. Vinyl tubing was used to mask the studs from the paint, and also provided a method of hanging the feet during the painting process.

As with most things, we have to build from the bottom up. And in this case, that’s the feet.

For the best geometry when it comes to attaching the feet to the cabin, an angle was best. This way it has three dimensional shape for maximum strength and rigidity, and creates two glue planes by which to secure it to the cabin’s edge angle.

Unfortunately there isn’t any angle available that has the right leg dimensions for us, and a material thickness of 1/4”. To make things more difficult, all of the “off the shelf” angles that are 1/4” thick have an inside radius which conflicts with the sharper corner of the fibreglass angle. We therefore had to create it.

This was done by taking a piece of square tubing with 4” sides and ripping it on a table saw to create two lengths of angle from the one length of tubing. The advantage of this is that the inside corner of the aluminum tubing had no radius whatsoever. After the tube was ripped, it was then cross cut to create the individual feet. Drilling, shaping and fastener installation came next.

Drilling the holes for the threaded studs.

The corners were all radiused on a belt sander.

The outside faces were also sanded on the belt sander.

The outside sharp edges were radiused on a router.

Then finally sanded to remove the router marks.

The threaded studs were installed with a press.

22 feet all ready for powder coating.

Step 2: The Riser Blocks

Unlike most welded rail installations where the standoff legs are made of the same tubing as the rails, our design uses solid material riser blocks which facilitates the use of mechanical fasteners. From an aesthetics perspective, we feel they add something positive to the overall look as well.

Although the riser block is not a terribly complicated component, it nonetheless had a number of steps to complete it.

Made from solid 1” x 1-1/2” aluminum bar stock, it would get powder coated the trucks brown accent colour.

The bar stock was cut to length on a mitre saw.

Sawn ends were cleaned up on the belt sander.

The dressed blocks ready for layout.

All laid out and ready for drilling.

5/16" pilot holes were drilled with a special bit.

The two outside holes are counterbored to 7/8".

The centre hole is tapped to receive the 3/8" bolt that secures the rail.

The blocks are all machined except for the corner radius.

To make the routing of the corners easier, and safer, they were held together as a solid bar with readi-rod.

As a solid bar, the process of routing was quite quick.

Each block had the corners dressed on the belt sander to remote the router marks.

Riser blocks all finished and ready for powder coating.

Totally done and ready for installation.

Step 3: The Horizontal Rails

A continuous barrier of protection for the glass solar panels.

Our material of choice for the rails themselves was 2” square x 3/16” wall aluminum tubing. It’s the same material we used on the lift platform for the motorcycle, only not quite as thick a wall dimension.

Aside from it matching the look of the rear lift assembly, we felt from an aesthetic perspective, the square shape of the tubing blended in better with the angular lines of our truck. After all, there’s very little in the way of round shapes on our truck.

We chose the 3/16” wall for resistance to impacts, and although thicker than most other truck rails, using aluminum kept the weight down to the acceptable level of 1.6 pounds per lineal foot. As a comparison, 2” round stainless steel ornamental tubing with a .080” wall thickness weighs 1.7 pounds per foot.

The other advantage of using square tubing over round tubing is the superior resistance to denting from impacts on the top outer edge where most strikes will occur. Unlike a round tube, the 90˚ corners of the tube provides a point that is extremely hard to dent, especially by anything organic.

The length of the various rail sections was largely dictated by the obstacles we had to contend with on the outer edge of the camper box. Since we wanted the joints between the rails to fall within six inches of a mounting foot, and the rails had to be a maximum of eight feet long so as to fit in the powder coating oven, we ended up with four different lengths to span the distance.

Since all of our creations happen at our home, which is located in a residential community, none of the metal suppliers would ship the tubing to us on their large delivery trucks. So we had to go and get it. So using our trusty Land Rover, we headed over to the opposite side of the greater Vancouver area to collect the 20’ long material.

Once back home, the fabrication process began again in earnest. The horizontal rails were the easiest to create because they were essentially just cut to length and then drilled to provide the anchor points.

The exception to this were the two rear sections of rail that had to be closed off, and a unique mounting foot welded on to interface with the rear tire rack and motorcycle lift assembly. After all is said and done, the rear rail sections were actually a structural anchoring mechanism for the rear lift. Their placement distributed the rearward forces exerted by the lift, to the horizontal fibreglass angles glued onto the length of the box. Those angles would be virtually impossible to tear off the box. So they provided the perfect anchor for the entire rear lift and spare tire assembly.

The end cap was welded on at the same angle as that of the lift side plate.

Dressing down the weld.

The finished end cap after filing and sanding.

Layout of the anchor mount. The bottom line designates the offset to the lift roof.

Machining the radius on the edges with a router.

The completed anchor point with a hole for wires when needed.

The bolting point on the rear assembly roof.

The other operation needed on two of the horizontal rails was to create the cutouts to clear the two solar mounts that protrude into the space occupied by the rail. Although there are various ways of machining these cutouts, because there were only two of them, we did them by hand with a drill and jig saw. Clean up was done with a file.

After layout, a hole had to be drilled to accept the jig saw blade.

The first side cut was made with a zip disk on an angle grinder.

Cutting out the material was simply a matter of following the line.

The cutout before clean up with the file.

The finished cutout after filing.

Step 4: The Vertical Rails

The two front vertical rails are where the most work was centred. They had to interface with the top horizontal rails, as well as the front cross rail that joins the two sides together, and which adds the superior strength to our design.

What created the most work on these rails were the two 90˚elbows. Unlike round tubing or pipe, where weld on elbows are readily available for purchase, no such elbows exist for our choice of square tubing with the edge profile and material thickness that we are using. So we had to create the curved appearance that would compliment our design. This in itself was a very time consuming process, but the end result was well worth the effort.

The corner elbow starts with a simple mitre joint.

Holes were drilled to provide the wire access points.

To create the outer radius of the elbow we had to use a cross section of pipe that we cut to create the two outer curves.

The quadrant of pipe was laid on the mitre joint and the inside shape scribed.

To make tracing the pipe quadrant easier, the mitre weld was dressed off with the router and a flat end bit.

With the shape traced, the process of removing the outer part of the mitre joint could begin.

First we cut across the tube with a zip disk on the angle grinder.

Then a hole is drilled to accept the jig saw blade.

The finished cut.

Checking to see if any more material needed removal to accept the curved piece.

Once we were happy with the fit, chamfers were ground on all the bits so we'd get good weld penetration.

A very important step before welding the corner radius in place was to file smooth the inside of the joint. This way the sharp edge won't cut any wire pulled through.

The pipe quadrant tack welded in place.

Welding complete. Not the prettiest of welds, but in this case it doesn't have to be.

Once the fabrication was complete, the process of dressing down all the welds and giving the corner its final appearance began. The first step starts with the router and a flat ended carbide bit.

Using the router we machined off the welds.

Using a file and sand paper with a flat backing board the outside of the corner radius was finished.

The sides of the elbow was dressed off next with the router.

After a bit of filing, and work with the sand paper, the face was finished.

Before carrying on, the access port for wiring was finished.

The centre area between the holes was removed with the jig saw.

With the bow tie shape removed, the opening was cleaned up with a file.

Then the final machining with the router and a 1/4" radius bit was done. This radius matches the edge of the tubing.

Finally, we used a sanding emery mesh to complete the elbow edges.

The finished inside face of the corner elbow with all the holes completed.

The final step for the vertical rail fabrication was to attached the tube standoff that secures the bottom of the rail to the apron under the camper box.

End plates with matching holes were machined and welded to the front cross rail.

Countersunk holes were machined in because of how close to the solar panels the plate would be.

Like the corners, the welds were dressed off with the router.

Filing and sanding completes the cross rail ends.

To complete the cabin rails we next had to manufacture the inserts and cover plates for the wire chase openings. Nothing too difficult, just fussy work.

The inserts were made from 2"x2"x1/4" angle. But it had to be cut down to fit snuggly inside the tubing who's I.D. was 1-5/8" square.

The angles were drilled to match the holes in the rails, and threaded inserts were pressed into them.

Countersunk screws were used to better ensure that no slop would be present when the inserts were installed.

The wire chase cover plates were made from aluminum plate and constructed to fit perfectly in the oval hole in the side of the rail.

The two parts of the cover plate were clamped together and then welded together at the bottom of the countersunk hole.

The finished weld is invisible when the screw is installed.

The inside plate fits snuggly inside the tube's oval hole, and returns the strength to the tubing where the large oval hole was cut out.

The cover plate is held in place with a toggle plate that grips the inside of the tubing when bolted up tight.

A custom shaped cover plate for a custom shaped hole.

The plate bolted firmly in place with the countersunk stainless steel screw.

Step 5: Preparing the rails for paint

Raw mill finish on the left, abraded finish on the right.

Before sending the parts out to be painted, the surface of the aluminum must be prepared. The raw aluminum mill finish does not allow the powder coating to adhere very well. So the surface must be abraded to create a key for the coating to lock into.

The small parts like the feet, riser blocks and cover plates were sent for sandblasting. But the tubing had to be treated differently. Sandblasting is an aggressive process, especially when done by an industrial sandblaster. The forces exerted on the material can have an effect on the structure of the metal, and things like long lengths of aluminum tubing can be easily warped. We certainly didn’t want that for our nice straight rails.

The rails were set on a level surface, clamped together and abraded with a dual action sander.

The radius corners were touched with a vibrating sander.

The sanded rails ready to go to the powder coater.

Bringing the painted rails back from the powder coater.

Step 6: Rail Installation

The actual installation was an involved procedure, mostly because we wanted to do it right.

The first step was to accurately lay out the position of the feet. This was necessary because we had to sand away the paint in order to create a proper bed for the Sika urethane primer and glue.

To aid in the sanding procedure, a plywood template was made that wrapped over the edge of cabin and could be taped in place. The vibrating sander we used on the edges of the aluminum tubing could now be used to sand away the layers of paint.

All of the foot placement sanding had to be done while standing on a ladder.

We got lucky with the weather and had two and a half days of sun and 18˚C temperatures to do the sanding and get the gluing done.

All of the foot locations were sanded first, and then we came back after and did the masking.

We tried to get down to the fibreglass in all spots, but the solar panels overhung some of the locations, and made sanding difficult.

The vertical locations had to be done with care as all sides were visible. Sanding outside the lines was not an option.

Because the glue would ooze out from under the foot, everything had to be well masked.

The sanding took quite a bit of time. All twenty two spots needed to be well done in order to have not only the glue adhere well, but the primer as well. Unfortunately the overhanging solar panels meant that some sanding had to be done without the aid of a machine.

All of the feet had to be carefully masked so no primer or glue could get on the finished surfaces. The glue has an etching property to it.

All of the feet had to first be placed in position and then the screw holes transferred onto the fibreglass for drilling.

Each foot was screwed in place prior to gluing to ensure everything was perfectly lined up.

The primer is quite runny, so extra care had to be taken to prevent and excess from running down the wall. We made little catch pockets below each foot with the masking tape to be on the safe side.

Each foot location and foot had to be primed in turn so the primer on both surfaces would be ready at the same time.

It only took about fifteen minutes for the primer to cure, and then we had about three hours to get the glueing completed after that.

The process of applying the glue from a caulking gun went quickly, but the cleanup afterward took longer. We wanted to be sure that lots of glue was initially applied so it would ooze out all around the foot. We didn’t want any air bubbles under the plate, or voids at the edge that would need caulking afterwards to fill the missed spots.

The glue was applied to the foot underside in parallel stripes. This would then allow the glue to ooze into the gap between the stripes, and push the air out the two sides of the foot.

We did one side of the truck on one day, and the second side on the following day. By the time we got to the end of the glueing and cleanup on each side, it was late in the day.

The truck was turned around at the end of the first day so the finished feet were now visible from the street side.

The next morning we peeled off all the masking on the side that was finished, before starting the work on the other side.

A shot of the installed foot in the early morning sun.

After the foot was finished, the riser blocks were all installed. Two of the blocks had to be re-cut to better fit a slightly twisted box angle. So touched up with black paint.

The two feet for the front cross rail were different. They slightly cantilevered off the edge so the rail could sit forward of the solar panel mounts.

This shows the offset needed by the cross rail to miss the solar panel mounts.

The last thing to do before the job was totally finished was to paint the plugs that would close off the holes for the railing bolts. We only had black ones, but wanted them to match the colour of the rail powder coating. Fortunately the powder manufacturer also makes matching rattle can spray paint. All we had to do was spray the plugs with a plastic adhesion promoter, and then we could apply the colour coat.

The hole plugs are an off the shelf product, but we only had black available.

Because the plugs are so light, we had to use double sided tape to secure the plugs to a piece of plywood so the spray of the paint didn't blow them over..

The plugs have a very low profile, and a textured finish.

The front cross rail not only ties the two sides together, but provides a high level of protection for the solar panels.

You can see the solar panel mounts just behind the cross rail.

Just enough clearance for the rails so they are flush with the outside of the cabin.

This is the special rear foot where it attaches to the rear lift and tire assembly. It's a structural component.

The angled rear of the side rail. An emergency beacon will be placed behind the rail in the open space.

A rail joint showing the insert, and the rail mounting screw hole plug on the left.

The rails sit just above the solar panels.

The wire access point can be seen here, covered by that special cover plate we made.