Monday, 3 June 2013

Unemployment... Not as Relaxing as One Might Expect

Blogging has been a bit scant lately, but that is due to change as I am now employed full time in the services of His Majesty Jim. Working on Jim in the evenings and weekends outside of the 9-5 of a full-time job, was tiring and fairly unproductive. It's difficult to get stuck into a job when you only get a couple of hours at a time to work on it, and so when I handed in my notice at work, I immediately lost motivation to work on Jim. I found it hard to summon any enthusiasm, knowing that working every free minute of my time would only gain me the equivalent of a few days full-time work. Consequently, not much has been achieved on Jim in the last 4 or 5 months, except for during the last few days.

It's been over a week since I became unemployed, and not one morning has started with a special brew or a trip to the betting shop. In fact, I have been starting work earlier and finishing later than I did previously, such is the burden of being supported by a generous but growingly impatient spouse.

The first job I started,was to finish populating the roof rack. Some time ago I finished installing the last three of the BLD 100w solar panels. I now have 800w of solar panels, wired through a morningstar MPPT regulator into a 540ah 24v Rolls Surrette battery bank. The batteries are on their last legs and so at the moment, the solar is simply preventing the self discharge from flattening the bank.

Roof rack of Jim the overland motorhome, unfinished with solar panels fitted

Having finished fitting the solar panels, I was left with a significant portion of the roof which remained to be covered. Having spent many mornings waking up in a hot tent with the ground sheet stuck to my sweaty face, and feeling like a dehydrated elephant had been urinating in my mouth, I have always been keen to try to keep the internal temperature down as much as possible in hot climates. One of of the ways I have planned to do this is to use a tropical roof the shade Jim's aluminium roof. To ensure that the tropical roof works as effectively as possible in keeping the internal temperature down, I have always planned to cover the full surface of Jim's roof, with the exception of the hatches which are needed to ventilate the inside and provide light.

To keep the weight and cost down, I am using a 12mm plywood product to provide a deck in the eight remaining sections of the roof rack. The product that I am using is called Buffalo Board, and is one of a number of similar brands of film faced birch plywood used for tough flooring in trucks, trailers, buses and trains. The upward facing surface of the sheet consists of a tough, waterproof phenolic film, textured to give the board some grip, and the back of the board is provided with a smooth film to retain the waterproof integrity.

As with everything on Jim, the roof rack in not perfectly square or true, and so the decking project started by making templates of the various shaped sections which needed filling. As I have done since I built the washroom, I glued strips of hardboard together to make a template, which I then transferred to the board, and cut out.

12mm Buffalo Board, with cut outs for lashing points

The depth of the roofrack is approximately 40mm and so if I had just dropped the 12mm boards into the frame, the steel angle sections would be very proud. This would make storing large items on the decking awkward, and would pose something of a trip hazard. Not wanting to end my travels as an entry in the Darwin Awards, I asked Brownchurch to weld suitable mounting rails to the rack to allow the boards to sit flush within the frame.

20mm box section rails welded to roof rack frame on which the decking boards sit

Unfortunately the welds securing the 20mm box section to the rack, prevented the close fitting boards from sitting flush in each frame, and so I had to bevel the back side of each board to allow them to clear the welds. The corners were also removed for the same reason.

12mm Buffalo Board, bevelled to clear roof rack welds

The area of space needing decking should have fitted fine within two sheets of 8x4; however no amount of cutsheet tetris would allow me to arrange all eight pieces. The large piece at the front of the box left a long thin piece which wasn't wide enough to accommodate any of the other sizable pieces, and so after cutting seven of the pieces, I was left with a large offcut, that was too narrow to get the final piece out of. To save having to buy a third sheet, largely unneeded, I cut the sheet in half and routed a rebate onto an edge of one half, and a reciprocal rebate onto the same edge of the other half. This allowed me to get a reasonably strong joint, and produce a single sheet large enough to get the final piece out of. The joint was glued using unthickened epoxy resin and clamped by putting wight on a piece of steel rested along the joint.

Rebate joint used to join two pieces of birch plywood

To allow the decking to be used for storage, I needed something to attach ropes or straps to, to prevent anything stored on the roof from decorating the windscreen of following vehicles. This scenario seems funny when you hear storeys of unlocked roof boxes scattering underwear down the motorway, but the reality would probably have a less amusing ending . Ebay provided me with 28 recessed sprung tiedown points which I then fitted to each board. Each tiedown required an awkward shape to be cut from the board to allow it sit flush; the cut-out comes pretty close to the edges of the flange and the bolt holes, and so overcutting the hole by more than a few millimetres would leave a visible cut, or nothing to bolt the tiedown to. If I'd known at the start how long it would take to cut 28 of these shapes out with a jigsaw, I would have made a template for the router.

Cut out for lashing point in 12mm Buffalo Board decking

galvanized lashing point bought in bulk from Ebay

The edges then needed to be sealed, to prevent water getting into the plywood Buffalo Board core and delaminating it over time, and so I painted the exposed edges with some floor paint I had left over from tidying up the steel floor inside Jim. With each board cut, sealed, and fitted with tiedowns, I then fitted each board in the appropriate space. The boards were dropped into position, and predrilled holes around the perimeter of each board were used to mark the drill position for the corresponding 5mm holes in the steel box section. The boards were then removed, and the steel exposed by the drilling was painted with zinc rich primer to prevent the damaged galvanising from starting to rust. The boards were finally returned to their place, and riveted in place with 4.8mm large headed rivets

recessed lashing point fitted to Buffalo Board decking on the roof rack

the tropical roof populated with solar panels and buffalo board decking

The roof rack solar panels and decking looking towards the cab

12mm plywood is plenty strong enough with the spans required on Jim's roof rack; on all but one piece there was no noticeable deflection when I walked across the piece. However on the piece above the bathroom skylight, their is a large cutout to allow the hatch to be opened, which considerably weakens the board. Putting any weight near the cutout made it bend considerably, and it certainly would have snapped if anything larger than a squirrel had put their full weight on it. To stiffen the board up, I screwed offcuts of the 24mm plywood that I used to build the washroom door, to the two edges of the most weakened areas of the board. One of the stiffening pieces is visible in the photo above with two rubber stops fitted to restrict the opening of the hatch.

On the same sheet, eight M8 T-nuts were fitted around the cutout, on which a board can be bolted to cover the roof hatch. Two of the four skylights in Jim's roof do not open more than a crack, just enough to ventilate the interior when driving; these skylights, designed for use in coaches, have been covered by two bars on the roofrack which are too close together to allow anyone to smash the glass and gain entry to Jim. The other two skylights open fully, and so fitting bars above these would have made them rather useless. To prevent anyone from smashing the acrylic in these hatches, and entering Jim through the back door (so to speak), I intend to fit covers to these during shipping, when Jim is at his most vulnerable. These M8 T-nuts will be used in combination with security screws, to bolt hatch covers over the skylights. It's not the pinnacle of security solutions, but it might stop a skint dock-hand from trying his luck.

Lewmar Ocean Hatch fitted to Jim the overland motorhome

With all jobs on the roof now complete, I can now continue to work on the interior, knowing that I will not be continuously climbing over any fine cabinetry to gain access to the roof  .


  1. Nice work! That roof looks pretty hardcore now.

  2. Thanks Stephen! Adding all the boards has actually stiffened the rack up quite considerably. 40mm angle is pretty lightweight in the context of the 2.5m width and althought there is still a fair bit of bounce as you walk across it, it is much better than when it was naked.

  3. Wow Nick, just scanning through... your attention to detail and the quality of your documentation is excellent.
    How effective is the air gap in providing insulation for the interior? Was it worth it?

  4. Hi Adam, thanks for the comment! It never really gets hot enough in the UK for the tropical roof to give much benefit. I'll be in a better position to answer your question in about 4 months when I should be near Guatemala