Rob Gray :: ontheroad :: wothahellizat :: wot2 :: diaries :: issue-019


Wed 16 Apr 2008

We've started cladding. No surprises here, we're using five-bar aluminium tread plate again, same as with Wothahellizat 1. Apart from the fact that we like the look, it's very practical, being very difficult to damage and impervious to scratches from trees etc. Not that it's really impervious, it's aluminium and not that hard, but the pattern hides any scratches you do get.

 Most of the first sheet in place. This sheet will have three panels, the top (not yet glued on) and bottom ones are fixed to the frame, while the middle panel is glued to the shutter.

Mon 21 Apr

Still cladding. The plan called for 11 days to do the entire job but as always the plan is wrong (the fact that we're still here 6 months after the original finish date bears witness to this). Still, after five days, we have maybe 40% of the truck clothed so we won't be that far off.

 In area we've done about half of the truck, but in time I reckon we're only about 30-40% done.

In doing this cladding I'm encountering the same issues I did seven years ago while building Wothahellizat 1, to wit...

Last time I made most of the cuts with a circular saw fitted with a tungsten blade. Typically I would make the cut just outside the line then plane it back with an electric plane.

This worked well but required the setting up of a fence to guide the saw, creates a cut that is wider than I would like, and it's almost impossible to plunge the blade into the material to start a cut in the centre of the sheet.

This time I'm using a 4" grinder with a very thin (1mm) cutoff wheel (a steel one, the wheels designed for aluminium are hopeless). By itself this works OK but if you regularly rub the wheel with wax it cuts through the sheet like...oh I dunno, something that cuts through something else really easily.

The resultant cut just needs a little deburring with a file and I'm done.

Pattern alignment
At a casual glance one would be forgiven for thinking that the patterns on a sheet have a pitch that's a submultiple of the sheet size. They look like that are 60x60mm which would make sense because the sheets are 1200x2400 so this would give an integral number of patterns on a sheet, and allow you to simply stick sheets side by side and have the pattern align.

Not so.

The pitch is 59.54x63.73mm, which means that, almost certainly, any two sheets placed side by side will not have aligning patterns.

Now maybe this won't matter to you in your application, but to me misaligned patterns on a truck body looks like sloppy workmanship.

This means that for every sheet on a side, apart from the first one, you have to measure the pattern, compare that measurement with its neighbour, and cut off as much material as required so that when they are placed together the patterns align when you look along the body.

 Nicely aligned patterns on the tread plate sheets.

Note that this means that you could lose as much as 63mm from each sheet, so you should not design the body to require the full 2400mm if you want to align the patterns horizontally.

Note also that, in theory, the same problem applies vertically. There are two reasons however that this is not really an issue, firstly the runs are short, we're only talking about say 2 metres in height as opposed to a length of maybe 8-10 metres. Secondly, you only see the vertical alignment when lying on the ground looking up at the body, not a position normally taken.

These two sheets are aligned pretty well horizontally (the red line) but not vertically as indicated by the fact that the centre "five-bar" pattern has six bars. This can be fixed by trimming the width of all sheets, but that causes problems with the placement of support beams in the frame at standard 1200 centres as you would not know the width of a sheet until you trimmed it.

The sheets have what I call a "grain" and if they are not all placed the same way up they can look vastly different at times.

If you look under most of the bars in the above photo you will see a light mark that mimics the bar. I call this the "shadow", and I make sure that this mark is below the bars on every sheet.

On Wothahellizat 1 there was a single panel that was fixed on "upside down", ie. with the shadow above the bars, and in some lights it looked like a totally different material. It bugged me for years so I'll not make that mistake again.

Last time we used 3M VHB (Very High Bond) double sided tape to fasten the sheets.

It worked well but on Wothahellizat 2 we're using Sikaflex. There are a few reasons for this.

Firstly, when I was dismantling the old body I had a hell of a time removing the panels that were fixed with VHB but at least it was possible with hand tools. However the single panel that was glued on with Sikaflex (for reasons that escape me now) was impossible to remove manually. I had to rip it off with a fork lift.

Next there's the surface preparation. Unlike the standard double-sided (or "mirror") tape that's fairly thick and a little spongy, VHB is only 1mm thick and has no give at all. Therefore the surface has to be almost perfectly true or there will be gaps between the frame and the sheet.

This is difficult to achieve.

Sikaflex on the other hand can be globbed on in just about any thickness, so I don't have to grind every weld perfectly flat and I can adjust the thickness to ensure that adjoining sheets meet evenly.

VHB sticks instantly, you only get one chance to position the sheet. If you place the sheet and immediately realise it's not quite right you can remove it but you ruin the tape because half will stay on the frame and the other half will come away with the sheet. If you don't notice an error until after a few minutes during which time you've pressed the sheet home and maybe helped it along with a rubber mallet, bad luck, you'll ruin the sheet if you try to remove it.

Sikaflex on the other hand takes several minutes to go off, plenty of time to adjust the sheet's placement.

Using Sikaflex
Firstly, which Sikaflex to use? I asked several people, including some in the truck body building game, and they all said 227.

Then I looked on the Sika website, They state quite clearly that 252 is the recommended product for panels on truck bodies. I rang Sika here in Australia and got the same answer so that's what I'm using.

They also state that the area to be glued should be cleaned with their 205 cleaner and primed with 210 primer.

Now maybe they just want to sell more products, but I think it makes sense to follow the party line, so that's what I'm doing.

I apply the glue very liberally and try to ensure that just a little squeezes out from around the edge of the sheet. I then resist the urge to wipe the excess or clean up in any way, do this and you will spend the next half hour with black sticky crap everywhere, several rags stuck to your fingers, and a worse mess than you started with. Let it dry, it's easy to cut off with a knife.

Clamping. Sikaflex provides quite a good bond immediately, even a large sheet will stay in place and will not fall off the frame once it has touched the glue. So I find that minimal clamping is required, certainly you should not clamp too tightly as this will expunge the glue from the clamped area.

The sheet will however slide downwards and this has to be addressed, but not by clamping. With a large sheet I feel that the force required to hold it up by clamping alone is too great. Also you need to be able to rest the sheet in position several times while cutting and trimming it to shape. Therefore I feel that some simple support is required and I've made a few widgets that I can clamp to the body in various ways to provide "platforms" to rest the sheet on. These stay in place until I feel that the glue has set enough to support the sheet.

Cheap material
When I was sourcing the tread plate I was offered a much cheaper product that, on the surface, seemed like a bargain. This plate came from an emerging industrial nation who shall remain nameless...OK I'll give you a hint, this nation will be hosting the Olympic games in a few months, but that's all I'll say. It was about half the price but I wanted to have a look at it first.

A quick visit to the engineering firm I was buying from confirmed that I didn't want the cheap plate. The ribs (or "bars" as they are called) were hardly raised from the surface of the plate at all, this means that the plate would not be as strong as the better quality version. Also the pattern was irregular and looked like it would be difficult to match between sheets. I asked about this and was told that they do sometimes use it and in fact find it impossible to match the patterns, so they only use it for small jobs where sheets are separate and don't have to match.

Tue 22 Apr

Mark & Gail arrive for a visit today. Roger & Kerryn, two other motorhoming friends, were also expected to arrive but their bus broke down at Mark & Gail's place so they're grounded for a while. They hire a car however and drop in anyway, we light a fire and enjoy the evening catching up.

Wed 23 Apr

We were hoping to get two sheets a day stuck on but it's been more like one a day. This is partly because I want the sheets to be as accurately placed as possible, with edges and patterns aligned, and this takes time; and partly because we have to add the insulation to most sheets before they are placed.

We do this because in most cases we cannot get to the back of the sheets, so the insulation has to be added first. Sometimes I can scribe the sheet from behind which makes it easy to know the shape of the insulation. But often I cannot get to the back at all, so I have to measure the bracing and transfer the measurements so I can cut the foam. This can take longer than the cutting of the sheet itself.

 Two of the sheets ready for gluing.

Thu 24 Apr

While Mark is here to help I thought we'd get into some demolition of the old body remains, just remove the timber so I can cut up the steel at a later date.

Or that was the intention.

Once on a roll though we can't stop and before long we have the old lounge room roof completely stripped.

 The lounge room roof has been stripped, the floor sits behind.

Fri 25 Apr

We do some more cladding this morning then Mark says he'll go over and chip away at the demolition. Chris is keen to get it done so we down tools and join in.

Within an hour or so there's no lounge room, just a pile of scrap.

 The lounge room in pieces, just one large bit left to cut up.

 Chris starts burning the timber.

 While I cart the last remaining piece over to the workshop and chop it up.

 The final pile of metal, Mark says I should put it on eBay as a kit motorhome in flatpack form.

 Meanwhile the timber has all but vanished, there's nothing but a pile of ashes left.

 Chris attends the pile hoping to make it even smaller.

Wed 30 Apr

We've got the last of the large cladding panels on so tonight we fire up the heater. The house is still full of holes, and we have towels blocking off most of the bedroom shutters which have yet to be clad, but the heater does a reasonable job of raising the temperature inside.

Apart from being warmer when we go to bed though it's of little use because we're still sitting outside.

Thu 1 May

It's exactly one year since we started building, and while we're not finished we're getting close. We are however marking the day by moving into the truck, that's right, as of today we're officially living in our new motorhome.

Sort of.

Chris doesn't trust me to get the TV working in time for her favourite show so we still sit under the tarp for most of the evening.

Fri 2 May

We're mostly inside now, the TV is installed (albeit rather dodgily) and the chairs are in, but we're still cooking under the tarp because there's some gas left in the camp stove and we're too tight to waste it.

The fridge is outside as well, we're in that limbo area between living inside and living outside the truck, much the same as we were with Wothahellizat 1. When you build like we do, ie. no house and only one set of possessions, there's always a period when you're half in and half out, where the coffee is inside but the milk is outside, the food is inside but not the cooker etc.

It's a real pain but I'm sure we'll get over it and it won't be for long.

 Our home of the last year, a tarpaulin in the corner of the workshop, is being taken down.

 >The fridge is still outside and the camp stove (left of centre on the bench) will stay in service until the gas runs out. The "kitchen" bench is now mostly covered with paint tins.

Sat 10 May

Before we could move in I had to at least get some of the plumbing working. As I mentioned the other day I've decided to redo the plumbing because we were having problems with the pump losing its prime overnight.

So I've move the pump to a spot below the floor and therefore below the tanks, this means that it will always be primed and removes the requirement for a non-return valve. I've also added my second pump, the two will run in parallel.

Also I've replaced the complicated valve system I had to allow filling/draining from the either tank. In it's place I've added two solenoid valves that can be operated from outside where I stand while filling.

The solenoid valves are in parallel with the pumps as shown below (one only shown, the system is duplicated).

This allows me to selectively fill and drain from either tank under electronic control, ie when filling I can control the valves to determine which tank receives the water. Similarly, when draining I can control the pumps individually to suck from either or both tanks.

The system now looks something like the diagram below. This is the same as the ideal schematic above but the elements have been rearranged to physically fit in the space available.

Note that I've separated the two systems in this drawing, in the real thing they are all mixed together due to space restrictions.

 Here's a photo of the finished product, the wiring has yet to be done.

Fri 16 May

I'm slowly getting really pissed off with technology. I know this new stuff is great and overall very reliable but it's so frustrating when it doesn't work.

For example, I've been using my mobile phone for connection to the internet for the past few years and in general it's been good. But the modem function of my current phone seems to have shat itself, leaving me with no access to the World Wide Wait.

In the past when something like this has happened I've got all flustered and wondered how I would survive, and admittedly that was my first reaction the other day. However each time technology causes me aggravation I get a little closer to saying "Sod it" and chucking the computer and everything related to it in the bin.

This time I just couldn't be bothered fixing the problem and left it for a couple of weeks (That's why there's been no posting here for quite some time).

Eventually Chris broke and suggested we get a new broadband modem, I agreed and we're now back on line. I'm happy to be connected again but that was a near thing, next time I get any agro it could be the end of as we know it.

And while I'm on a rant, let's talk about VB.NET.


There that feels better.

I've been using VB6 for years and, while it could do with some improvement, it handles the job of building smallish applications well.

If VB6 is the Vervet monkey of programming languages, VB.NET is a 400-pound gorilla. It's so large and complicated that I find it very difficult to get my head around, there are next to no examples in the help files and every one I've downloaded from the net has not even compiled let alone ran and worked.

Anyway, I've calmed down now and the diaries are back, until the next bout of total computer-generated frustration that is.

What I need are some hobbies that don't require the use of computers, bird watching an astronomy are two that spring to mind. Let me know if you have any ideas.

Sat 17 May

One of the shutters is catching on the frame as it opens. Fortunately they are designed to be removed without too much trouble, so I unbolt it and plane the offending sheet of aluminium.


Sun 18 May

We've finally finished the cladding, thank goodness for that. Now that the truck is weather resistant we can move it from the workshop into the wash bay which is less sheltered. This will free up the space we're been occupying, and I'm sure Peter will be happy to have most of his workshop back.

 The truck in its new clothes.

Tue 20 May

We've been walking on a motley collection of assorted boards for some time and it's getting a bit annoying so it's time to do the floor.

Last time we used straight 19mm thick ply for the floor and lifting some of the old sheets the other day drove home to me one of the reasons Wothahellizat 1 weighed so much.

This time I think we can do better.

We've decided to make the floor out of a home-brew laminate, featuring a layer of 6mm ply, followed by 10mm of closed-cell insulation, and finally some 3mm ply.

This should provide reasonable insulation while being light and strong with a little give.

I also have to make some trapdoors to access the water pumps and the winch.

 The 20,000lb winch is mounted in the middle of the chassis so I need an easy way to access it.

To provide some isolation between the outside and inside the trapdoor's layers overlap those of the surrounding floor.

The trapdoor layers overlap the floor to increase the interior/exterior isolation.

 The trapdoor in the kitchen floor through which I can access the winch.