Jim Gets a New Hat

I decided a while back that Jim needed a roofrack for several reasons, including the provision of:

• a ‘tropical roof’ to shade the surface of the roof
• a suitable frame on which to mount solar panels
• a suitable frame on which to mount an awning
• a platform to store lightweight equipment, and
• protection to the truck’s roof edges from overhanging branches

The tropical roof idea is something I stole when reading Rob Gray's motorhome build diaries, although it is not a new idea. The idea has been used for years on buildings in hot countries, and was used by landrover (called a "safari roof") on their series 1 station waggons in 1956. It is essentially a second roof suspended a short distance above the main roof, keeping the main roof in permanent shade, and helping to keep the interior cool. Rob made his roof in the latest incarnation of his truck by gluing battens to the roof and fixing the covering to these. This would probably have worked fine on Jim, but the roof sheet is not particularly heavy gauge, and at the time of making the decision I was not 100% confident in the ability of the glue to prevent the panels from flying off in high winds. As an alternative I decided that a roof rack arrangement, attached to the structural steel frame of the roof, was a good alternative.

The roof of Jim is made up of several sheets of aluminium riveted together, with strips of aluminium overlapping each of the seams. When I bought Jim, his roof leaked badly, and I spent a long time chasing leaks and sealing the large number of rivets and seams along the roof. As a result I was keen not add more holes to the roof, and so I set about planning a roof rack that would be fixed using brackets bolted through the sides of the truck into the steel frame.

The easiest way to get a large solar array on the roof of Jim, whilst providing an effective tropical roof, would have been to use several large (250-300w) panels, neatly filling the available space. The cost to power output ratio of solar panels also improves considerably with bigger panels and so this would also have been the cheapest option. Below is a picture of Emil's excellent Man Kat motorhome for an example of what I would like to have achieved, perhaps with a few less panels.

Sadly, this option was not possible, and so as is usually the case, I had to opt for a more complicated and more expensive solution.
The roof on Jim is already home to two fully opening roof hatches, two coach style partially-opening roof hatches, and two air vents which extract air from the bathroom and kitchen areas. Whilst these obstructions don't take up much of the available real estate, they do prevent a straightforward solar panel layout, and certainly do not allow the use of multiple large solar panels. If there was a set of common solar panels sizes which manufacturers used for each output of solar panel, it would have been fairly simple for me to optimise the layout to the get maximum solar output, with the minimum number of panels, and the minimum wasted space. Unfortunately every manufactures makes different shaped panels, and so the job of designing the roof layout was further complicated.

A PV importer local to me in East London, imports a range of Chinese solar panels, and on going through their products, I found a 100w panel which tessellated neatly in the available space on the roof of Jim. I had already decided that I didn't need more than 800w of solar panels, but with the 100 panels available I would have been able to fit 1,100w if I'd wanted. As is often the case with smaller output panels, the nominal voltage of the panel is 12v, this is to make it useful for charging batteries in small installations. Had I only wanted a single panel, I would not have been able to charge my 24v battery bank with this panel, but with 8, I am able to wire them in series to increase the voltage. As it happens I will be wiring them in two parallel banks, with a nominal voltage of 48v, which the MPPT regulator I am using is more than able to cope with; this high voltage means that I can use smaller cables, achieve lower voltage drops, and always ensure that the regulator is receiving a high enough voltage to charge the batteries effectively .

To prove that the layout was possible, and to make it easier to build the roof rack, my wonderful assistant used sketchup to produce a drawing of the proposed layout.

In recent years, China has invested huge sums of money in PV manufacturing, and whilst in many cases I would avoid cheap Chinese imports for such an important purchase, I couldn't ignore them in this instance. The panels come with same 25 year guarantee as the established brands, and whilst it is possible to dispute the specifications, there is no reason why the products should not be capable of meeting them. The Chinese government often tries to stimulate certain markets with subsidies and low-interest loans, and as a result of this, for a while, Chinese companies were able to sell their solar panels at roughly half what brands such as Sharp and Panasonic charge. Since I bought the panels I will be fitting to Jim, many established brands have reduced their prices somewhat to compete, but at the time I couldn't afford to ignore the Chinese options, and bought eight 100w PV panels from BLD Solar, a fairly young company based in Zhejiang province. The BLD factory is ISO:9001 certified, and the company will produce approximately 150MW of panels this year.

With the solar panels purchased, and the layout finalised, the only thing left to buy before the rack could be manufactured was an awning. Many truck based motorhomes fit small awnings to the side of the body, making the installation easy and allowing the use of caravan style awnings which are only designed to be mounted up to 2.5m off the ground.

I was keen top avoid fitting an awning as on the above unicat vehicle, as I didn't like the idea of having something sticking out of the side of the truck, and also because I wanted the awning to cover the side door so that the awning would shelter the door in the rain. In the past I have had Jim's anual test conducted as a Large Goods Vehicle rather than a motorhome and so have had to endure a test with VOSA each year. Knowing how indescribably pernickety they can be (they once failed me on using the wrong kind of bolts - hex instead of dome head - to hold the side skirts on), I didn't fancy my chances with a big box sticking 20cm out of the side of the truck. I therefore wanted an awning which could be mounted on the roofrack, approximately 3.5m off the ground, and would cover the full length of the truck. I ended up buying a 5m long, 3.5m deep awning from the Awning Company, a popular manufacturer of awnings for race trucks, horse boxes, and emergency services vehicles. They manufacture awnings for vehicles far longer, and far taller than Jim, and so I didn't have worry about modifying a flimsy caravan awning to be mounted so high up.

With all the equipment to be mounted on it purchased, I was ready to manufacture the roof rack, but before it was manufactured and fitted, I was keen to banish roof leaks, as far as possible, from reoccurring on Jim. Once the roof rack was fitted, and the solar panels and decking pieces installed on it, access to the Jim's main roof would be completely restricted, and so I set about doing everything I could to reduce the chances of me waking up in bed in entirely the wrong kind of wet patch. Many motorhome owners will attest to how irritating and damaging roof leaks can be, it is surprisingly common . Often the leak is only noticed after it has rotted through the ceiling lining, soaked the insulation, and run down the backs of all the cabinets. On Jim, the inside of the box body is lined in seam sealed sheets of steel and aluminium, and so the leaks had previously manifested themselves as streams of water pissing out of the small gap between the wall sheets and the floor, meaning that all of the steel structure had been exposed to water, and all of the insulation in the walls was soaked . It seems that almost all types of motorhome roofs leak for one reason or another, some worse than others, and I guess I should be pleased that I did not have a perished EDPM roof to replace, or a torn fibreglass sheet to repair.


When I had had enough of the leaks in Jim's roof a few years back, I dabbed Sikaflex 221 over the heads of every rivet on Jim's roof, and scraped away and replaced the sealant along every seam. Thankfully this cured most of the leaks, and I was glad not to have had to drill out several hundred rivets and reseal the overlapping strips of aluminium on each seam. Below is a picture of some of the rivets and perished sealant prior to the initial re-sealing.

This approach was pretty successful, but any sealant will perish faster when exposed to wind, rain and UV from the sun, and so I was not confident that this fix would last for the lifetime of my ownership of Jim. To Bolster this sealing effort, I wanted to cover the whole roof in a coat of sealing paint, to protect the seams and rivets and add an extra layer of waterproofing. In America where huge RVs are common, there seems to be a fair choice of roof paints designed for use on aluminium (or aluminum if you want to use the antiquated 1807 spelling) or rubber roofs. In the UK however, we do not have these products, and the my choices were fairly limited. By far the most common type of flat (leaky) roof in the UK is the mineral felt roof, and so most available roof sealing paints are thick, black, bitumen based products which work well of asphalt roofs. I was not confident that these would adhere well to Jim's aluminium roof, and didn't want a sticky black mess, which would perish in the same way as all hydrocarbon based roof products. Consequently I looked at the available alternatives, which all seemed to be white, acrylic based paints, most of which are described as elastomeric, which just appears to mean that they are flexible enough, not to crack with small movements along seams.

The general consensus in the building trade is that Acrypol is a good product. It is described as an acrylic resin dispersed in a solvent, and has fibres mixed into the paint which are supposed to help to produce a tough, seamless surface. Following the advice, and based on the recommended coverage, I bought three 5kg tins of the stuff.  Using any normal paint, I would not have needed more than two or three litres to cover Jim's roof in a couple of coats, and so I struggled to comprehend how I would manage to dump more than five times this amount onto the roof. My disbelief was answered when I started to use the stuff, it really is the thickest paint imaginable. The best way I can described it, is as having the consistency of cold custard, mixed with the sweepings from a barbers floor; it goes on extremely thick, and it really isn't hard to meet the recommended coverage rate.

The finished appearance of acrypol is pretty diabolical. I know the appearance of a motorhome's roof is not important, but I would serious advise against using it on low vehicles of which the roof can be seen by pedestrians. It does not dry smooth and so it quickly begins to look dirty as rain water leaves deposits stuck to the surface. It also does not dry hard, and so I would also not recommend it on vehicles where you wish to walk around on the roof; walking around on the roof leaves imprints and bits of dirt stuck to the surface, which further ruin the appearance. Despite the poor appearance I am pretty happy with the product, it is pretty difficult to imagine how water could permeate the thick, flexible coating covering the roof surface, although time will tell I suppose.

With this completed I turned my attention to the two roof hatches which came fitted to Jim, the last remaining major source of leaks on Jim's roof.

Clearly the primary concern with the hatches originally fitted to Jim, was their security. They were fitted to allow the crew to escape in case of a rollover, but it is obvious that the designers at Trumac were concerned about them being used as an entry point. To prevent any would be thieves from getting a purchase on them with a crowbar, they were designed so that the hatch was flush with the surface of the roof, as can be seen above, with a minimal gap into which anything could be inserted (so to speak). On a normal hatch fitted to a boat or motorhome, the frame of the hatch will form an upstand from the roof, and the hatch will sit over the frame, forming a weatherproof seal; as Jim's hatches had no such upstand, any water on the roof ran into the gap between the frame and the hatch. This was clearly unavoidable given the desire to have no protrusions on the roof, and so to prevent the water flowing mercilessly into Jim's interior, the original coach builders included a channel around the inside of the frame, into which the water would flow. To drain this channel, hoses channelled water from two small fittings per hatch, down hoses through the interior of the truck, and out through the floor. The design actually worked pretty well, and in heavy rain a visible torrent of water could be seen coming out of the hose under the truck. The designs major failure though, was the size of the drainage fittings. Any leaves or debris which got blown onto the roof, would get washed into the channels around the hatches and would block the drainage holes; water would then back up, and would flood the interior of the truck.

I quickly learnt the need to regularly unblock these drainage holes, but occasionally something big would get stuck, and the hatch would leak again. The final straw came when I found water dripping through the inside of the electrical cabinet (home to a battery charger, solar regulator, mains consumer unit, mains changeover, alternator regulator, voltage dropper, etc), and I realised that the security hatches had to go. For a while I toyed with the idea of modifying the hatches to improve the seal, but realising that I was overcomplicating the problem, I decided to simply replace them with an off the shelf hatch. And so I set hunted for a hatch, of which preventing torrents of water from gushing inside was higher up the design priorities list than preventing prybar wielding thieves from descending through the roof.

Wanting to retain the ability to use the hatches to access the roof, I looked for hatches that opened fully and used as much of the existing aperture as possible. I ended up purchasing a pair of Lewmar ocean hatches, a tough marine hatch with a thick aluminium frame and thick acrylic 'glass'. It would have been remarkably fortunate if the hatches had simply fitted over the existing hatch frame, and of course this wasn't the case. I got a local welder to cut two plates to blank off the apertures after removing the existing hatches, with new apertures cut into them for the Lewmar hatches, and with holes drilled and tapped to fix them in place. Both blanking plates and hatches were fitted with relative ease; the photo below shows the hatch being fitted in the bathroom, during its construction.

With the roof waterproof, I began planning how I was going to build the roof rack. The design was simple enough, and I was confident I could fabricate it, but I quickly realised I had nowhere to build it. I do not have enough space to weld up a 5m x 2.5m roof rack in what is left of my garden, and even if I did, I do not have anywhere flat enough to let me set it out precisely. I could also think of no sensible way of welding the rack in-situ; my MIG torch is 4m long, and so even with the welder on the raised tail-lift, I was still only able to reach a short area at the back of the roof. I like to undertake as much of the work on Jim as I am able to myself, with the tools and time I have available, but in this case I took Jim for a short holiday to Brownchurch, the experts in custom roof-racks. Brownchurch are well respected amongst Land Rover owners for building tough roof racks, and I am fortunate that they are located about 10 minutes away from my house.

Despite the job being rather different from their normal output, Brownchurch completely understood what I wanted, and in a few weeks, they designed, built and fitted Jim with a galvanised steel roof rack. The layout I had given them, did not allow sufficient space between each solar panel for box section steel of a suitable size, and so Brownchurch fabricated the rack from angle section, with each panel sitting within the frame. Below is the rack, back from the galvanisers and awaiting fitting.

I asked Brownchurch to fit the awning for me. It is heavy - I suspect around 100kg - and with no forklift, hiab, gantry crane or anything else mechanised to assist, my enlightened powers of precognition foretold of damaged spines, crushed fingers and broken awnings, should I have attempted to fit it myself. I will fit the solar panels and decking panels myself, after I have run the wiring for the solar panels, and perhaps some power cable for a few work lamps. Here is how Jim looks with his new hat.

And below is how the roof looks presently, after the weather presented another perfect opportunity to test and observe the effectiveness of the waterproofing efforts.

 The awning is slightly more involved to erect than I would have liked (remove locking nut, wind out, fit torsion bar, and fit both storm bars or legs), but the space it provides is awesome, and if the ten extra minutes it takes to erect mean that it wont become a mangled wreck in the first gust of wind, then I suppose it is worth it.

Before I can fit the solar panels and decking to the rack, I have to have to drill and paint about 200 holes for the cable clips, solar panel bolts, earthing links, and decking rivets. I started on Saturday but the job quickly reaffirmed that the batteries on my trusty 14.4v Makita drill have reached their terminus. Now I just have to convince myself that I really do need to upgrade to a lithium-ion drill...