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 Living on the Road :: Wothahellizat Mk2: Construction Diary : #17

Mon 18 Feb 2008

Despite the lack of activity on the web site there has been a lot happening, a thousand small and mostly uninteresting jobs. I've added stays to most of the shutters, fire-proof lining around the cooker, insulation around the oven etc.

We've also been working on the roof for the past day or so. We're using all the solar panels from Wothahellizat 1 and it's a pretty tight fit.

In keeping with my "no holes in the roof unless absolutely unavoidable" policy the panels will not be screwed directly to the roof.

Rather I have placed aluminium battens across the vehicle, these are glued to the roof sheets and will also have their ends riveted to the gutter when that's installed.

We have eight Uni Solar 64w panels and two Kyocera 120s but I have allowed space to upgrade two of the 64w panels with two of the new 165/170w jobs that are similar in area but longer and thinner.


The roof layout.

As you can see the panels cover most of the roof which is a good thing because they form what's known as a "tropical roof", a cooling device I have only seen in Africa and Australia.

To keep the vehicle cool it helps to park in the shade, but of course this isn't always possible or even desirable when you need the sun for power. So the solution is to carry your own shade in the form of a second roof mounted above the vehicle's main roof with an air gap of an inch or so separating the two.

This tropical roof cops most of the heat and the air gap allows convection currents to carry the heat away.

As the solar panels are mounted on 1" battens they make a pretty good tropical roof, the small amount of roof not covered by panels will have timber sheets mounted to the battens to act as shade givers and also provide somewhere to walk.

In Wothahellizat 1 I used timber battens and aluminium sheets for the walking areas, but I've reversed the arrangement this time mostly because the timber battens where beginning to rot.

Tue 19 Feb

I'm adding the solar panel battens today. As mentioned before, in order not to pierce the roof with fasteners these battens are glued along their entire length and will be mechanically fastened to the gutter trim on the ends.


The battens have been bent but not cut to size so they are still too long and are resting on the gutters.

As the roof is slightly gabled the battens have to follow the same curve. This is easily done by cutting part of the way through the aluminium box section and bending it. If I was doing this in steel I'd weld up the cut, but I can't weld aluminium so I'll just apply liberal amounts of gorilla snot (sealant) to fill the gap.


By cutting part way through the aluminium I can bend it to any angle I like and retain most of the strength of the box section.

After cleaning and priming I apply Sikaflex and stick the battens down. Once that's done we paint the roof with Penetrol, it takes about 24 hours to dry so that's it for the roof today.

I then start making the shelves for the camera cupboard.

Wed 20 Feb

The Penetrol is dry so Chris can paint the roof with Thermashield, a special insulating and sealing paint for motorhome roofs.


The recently Penetrolled roof.

The battens have to go from edge to edge across the roof but I still need to allow water to flow along the gutter so it can reach the drains. To facilitate this I cut out some sections from the ends of the battens.


The cut out section on the batten ends (circled) and the down pipe fitting used upside down to stop surface water entering the hole in the roof.

Also notice the upturned down pipe connector in the above photo. I need a hole in the roof to pass all the aerial and solar cables and there's a few ways ways to do that.

For example you can try to seal the holes around the wires with glue or use proper cable glands for each wire. The glue option never works. The cable glands do work but I'd need one for each wire (about 12 of them) and they only seal if you're using round wires, not figure-eight as will be used for the solar panels.

Another method is to not even try to seal the hole, just use a large opening with a high surrounding lip to stop surface water from entering, then cover it over with something, in this case I'll use one of the solar panels.

We used this method in Wothahallizat 1, I had a huge hole through which I passed several wires but which also acted as a vent. In six years it never even looked like leaking.

Thu 21 Feb

We're sleeping in the truck for the first time tonight, very exciting. Not that it's ready to move in, but our normal bedroom (the Landcruiser) is full of junk we're taking up to our container tomorrow.

Fri 22 Feb

Well that worked a treat, it was very comfortable, the only problem was mosquitoes as we have no netting up in the windows yet. Actually, even if we did have netting it wouldn't make much difference because we don't have any walls either.

It takes all day to drive up to our land, talk to some neighbours, drop off the stuff and return. One thing we learned is that just about all the neighbouring blocks have sold recently, and that ours has increased in value by 70% over the last two years.

After all the losses we've made over the years it's nice to have a win for a change.

Sat 23 Feb

We burned a mosquito coil last night and that did the trick, no mossie bites all night.

Thu 21 Feb

I'm about to start mounting the solar panels, but first I want to test an idea.

In an attempt to further cut down the heat the reaching the roof I've decided to add insulation under the panels. There are two questions though, will it make much difference, and will it affect the efficiency of the panels.

Most solar panels derate considerably when they get hot, for example the 120-watt Kyocera panels drop their output to 87 watts with the cell temperature at 45° and insulating behind them probably won't help as it will reduce the airflow.

To help overcome this I've drilled holes along the sides of the panels and left air gaps in the insulation.


The presumed airflow through and under the panels.


Testing the insulation underneath a Kyocera 120w panel.

I leave a half-insulated panel out in the sun to see how it goes. The area under the insulation is certainly cooler than the other non-insulated half, but the panel above it is also hotter.

I'll go ahead with the idea and we'll see how it works over time. One thing in our favour is that eight of the ten panels we have are Uni Solar panels and these don't derate in the heat.

Tue 4 Mar

The panels are installed, they can be hinged on one side for maintenance.


The roof is almost entirely covered in solar panels. What's not is plywood tropical roof (the grey bits) or reserved for aerials.


Here's another view that also looks down into the bedroom and kitchen.

Wed 5 Mar

Doing the solar wiring today. I've added blocking diodes although from what I've seen most people don't bother with them.

In theory, when it's dark, the batteries can discharge back through the panels. I think this discharge current is very small and only a problem when a motorhome is kept for long periods in the dark which presumably will not be the case with ours once we get it out of this workshop.

There is however a reason not to use diodes, and that is that you get a small voltage drop over them and therefore a small loss of power. I'll put them in the circuit though partly because I'm using Schottky diodes which have a very low voltage drop, and partly because I've had the diodes for years and may as well use them.


The solar wiring. The wires from the panels (5 off, one per pair of panels) enter at the top of the photo and connect to the blocking diodes on the right. From there they go to the relay where they are joined. The current leaves the relay in a thick wire and goes to the regulator. Mouse over the photo to highlight some of the details.

I've also run the wiring through a change over relay, when fully wired this will allow me to bypass the regulator and connect the panels directly to the batteries.

Once again I'm not convinced that this is a great idea but I know that our regulator does not appear to allow much absorption time and I would like to be able to force more charge into the batteries manually.

When our batteries are charged they should be taken to about 28.8 volts and held there for a period of time known as the absorption time before dropping them back to the float level of 26.7 volts. Our inverter/charger will hold them at the absorption voltage for two hours, however the solar regulator seems to go straight into float once the 28.8v level is reached.

The abovementioned relay will allow me to override the regulator and force the system to continue charging the batteries. Of course one has to be careful here, you can damage batteries if the voltage gets too high.

Once again, time will tell if this is a good idea.

Tue 11 Mar

We're working on stays for the time being and it seems that every shutter requires a different design for its stay.

Some are simple pieces of RHS that prop the shutter open, while others are telescopic with spring-loaded pins that lock the stay at the correct length.

The simplest way I can think of to make a spring-loaded pin is just to weld the pin to a lenght of flat bar and weld the other end of the bar to the outer part of the stay.

The trouble with this is that the "spring" is just made from mild steel and I'm worried that it will eventually stay bent out and not hold the pin in. If this happens there would be no way to bend the spring back as I would have to bend it past the stay so it can return to the correct position.

So just in case this happens I've offset the spring, this gives me something to bend if I have to reshape it.


One of the more complicated stays, showing detail of the spring that holds the pin. The pin that does the locking is not visible here as it's inside the stay, I've extended it through the spring to form a small handle and that's the part you see here.

I've also spent a great deal of time working on the rear shutter/deck roof. This shutter is actually two in one, the whole thing can open as per a normal shutter, but there's another shutter within that. By leaving the main part closed and opening the inner shutter two windows are revealed.

This design should allow this rear wall to be totally open when the area is being used as a deck, partially open when the weather is nice and the area is being used as part of the lounge room, closed to the elements but allowing us to see out when the weather is bad, or totally closed when driving or at night.

Confused? Hopefully when it's all finished I can post some photos that make it clearer, meanwhile here's how it looks today.


The deck in its open position.

Thu 13 Mar

While installing the solar panels the other day I realised that we really need a ladder to access much of the roof. While it's easy enough to climb onto the roof through the hatches, you can't move around much because it's not a great idea to walk on solar panels. This will make cleaning and general maintenance difficult.

So we need a ladder, but were to store it?. We looked at those telescopic ones, they would be easy to store but they're pretty heavy and cost a fortune.

We finally decide on a cheap extension ladder and figure that we can store it under the body between the rear wheels. I even make some brackets to do this but then realise that we may have problems with the chassis hitting the ladder when it twists.

When mounted in this location I have about 200mm (8") clearance between the wheels and the ladder and the wheel travel is only about 150mm so in theory that shouldn't be a problem. But when the chassis twists this clearance will reduce, also the ladder is fairly close to the tool boxes which are mounted on the chassis. They could also hit when the chassis twists.

So I have to find somewhere else to mount the ladder, and Chris comes up with the idea of hanging it under the motor bike trap door.


The ladder mounted under the motor bike trapdoor.

This will make the trapdoor slightly heavier to lift into place and may impede the winch cable a tad, but apart from that it's a pretty good place to store the ladder.

I also have to cut the ladder down a bit because it's over 2.4m (8 feet) in length and the truck body is only 2350mm wide.

Mon 17 Mar

Now that the ladder is taken care of, what can I do with that potential storage area? There's a cranny 500mm wide and varying in depth between 75 and 150mm, it's the full width of the truck and just crying out to have something long and thin stored there.

Initially I planned to put the shovel, spade, axe, and related "gardening" tools there and have them slide out on a long tray. But although there's 150mm of height inside the body, anything that slides out has to pass through a 75mm gap and two of the tools are over 75mm in height. I could hinge the compartment and drop it down but then it would be difficult to reach in and unclamp the various items.

I've figured it out, I'll make a tool rack that both slides out and drops down. I've also decided that, rather than make a single rack that spans the entire body, I'll make two that go roughly half way, so some items will be accessed from one side and some from the other.

Each rack is just a hinged frame with assorted cradles and clamps to hold the odd-shaped tools in place. I will not sheet it in to form a tray as this will only collect dirt, although the tools are over the wheels and will cop a lot of crap, especially if we get into some mud. I may add a small amount of sheeting to protect them from the majority of the stuff thrown up by the wheels.

Wed 19 Mar

Today I'm building a mount for the spare water tank. In all we have seven tanks, two banks of three make up the main water storage inside the body, while the seventh tank will be mounted under the chassis and provide an outside source of water for washing hands etc.

It's other purpose is to provide an emergency supply if we have a major leak and loose all the water from the main tanks.

There's a lockable tap on this tank but of course most taps and valves provide no convenient method of mounting, so much time is spent building a mount to hold the tap securely.


The mount for the water tank's tap. The round body of the tap sits in the cradle formed from two pieces of flat bar, and is clamped down using a bar across the threaded rods.

Thu 20 Mar

With the water tank mount and the tool racks finished I pull them all out and set up the wash bay as a spray booth.


Some of the recently-sprayed components. The water tank mount is in the foreground, with one of the tool racks hanging behind it.


Some of the brackets that hold the tools firmly in place. No wonder it takes so long to build a motorhome.


The finished left side tool rack.


Here's the outlet from the tank connected to the tap with some vinyl tube. As the tank hangs below the chassis the tap and outlet are potentially at risk from sticks etc so they're mounted on top of bash plates.


The finished tank mount ready for installation.


And installed. The tank sits up inside the chassis rails and hangs down by about 200mm (8").


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