Don't bite the dust!

Dust is a dirty fact of life in off-road caravanning, but it doesn’t have to ruin yours

Let’s start with the facts. Dust in Australia is everywhere off the bitumen and no manufacturer can claim truthfully to have banished it completely from their caravan, camper trailer or motorhome, as there so many variables.

The real problem is that most caravanners accept such faults from many manufacturers/dealers as being the norm and after handing over their money, are left with defects that should never have been there in the first place. So fight back!

Yet some makers do markedly better than others and there are many lessons they have learned (often at great expense) that you can apply to your caravan or camper – or when purchasing an off-roader.

GAS VENT DRAMAS

One of the greatest variables is whether your van has internal gas cooking or heating.

Australia’s strict gas regulations require manufacturers to maintain a specific airflow through the van or pop-top, so that if gas is inadvertently left on, or there’s a leak (not uncommon in off-road vans where pipes can fracture from movement) it isn’t fatal.

Many argue that these regulations, which were adapted to cover caravans rather than being framed specifically for them, are over-strict, but manufacturers have to adhere to them or else potentially end up in the Coroner’s Court!

With no internal or diesel internal cooking and heating, these gas regulations don’t apply, so you can have a solid entry door and there’s no need to build in further vents in the upper walls or pop-top.

Of course, you have to be travelling through dust for it to be an issue and the finer the dust, the more penetrating it is.

Most people think that the source of any dust problem inside a caravan are the holes or spots where they see the trails of dust ingress, but the root cause is where the air escapes from.

Dust enters if there is a lower pressure inside the caravan to the outside. The low pressure creates a partial vacuum and sucks in the dust through holes and gaps. These holes often are where electrical or plumbing cables and pipes pass and behind the fridge, while where the wheel boxes join the floor and around the doors and window seals are other prime suspects.

Air-conditioners generally have a drain hole so while sealed to fresh air-flow, small holes in the air-conditioner housing by the manufacturer, become a source of escaping air, while windows and doors have very small drainage holes.

In some cases, they’re less than 1-2 mm in diameter are necessary to prevent build-up of moisture and corrosion. but these also let the air escape.

Go out on a dark night, turn on all the van’s inside lights and then slide underneath looking for pinholes of light. A silicone sealant will deal with many of them, while worn window or door rubbers should be replaced.

An interesting point here is that many serious off-road caravans don’t have rear windows because it’s here that most of the dust gathers. So, every time you open and shut the window, you are weakening the seal to the point where ultimately it will leak.

KEEP YOUR COOL WITH FRIDGES

Fridges are big dust offenders. They require external venting to function efficiently, but all too often the air cavity behind the fridge that vents to the outside causes problems if not sealed off properly to the interior of the van.

However, one of the problems with letting your fridge vent to the outside in dusty conditions is that dust in the fridge cavity will settle on the evaporator coils and ultimately they will no longer be able to dissipate heat, the by-product of refrigeration.

This in turn means that the fridge will work harder to maintain temperature and increase your 12-volt usage, which is bad news for an off-road caravan relying on solar power.

Many off-road vans for this reason have external body hatches that you should raise when camped to allow their 12v fridges to work more efficiently and will allow the compressor coils to be dusted off, while some manufacturers vent their fridges internally, which is technically less efficient, but overcomes the dust issue.

Doors are notorious for letting in dust, largely because most manufacturers fit those made by major suppliers rather than go to the expense of tooling up to build their own. It’s a bigger problem for a manufacturer with a range of different-sized models.

So, the manufacturing tolerance between the door and a hand-built caravan often results in an imperfect seal, while continually opening and closing weakens seals.

DUST-BUSTING TACTICS

Several Queensland off-road specialists including Bushtracker and Australian Off Road employ an auxiliary external flap that is pressure tightened over the door vent when fording streams, where they can be semi-amphibious up to one metre of water in Bushtracker’s case and keep bulldust out when travelling in dusty conditions.

As they can’t be fitted once you’re inside the van, we understand these doors meet the gas venting regulations.

Others off-road custom builders, notably Melbourne’s Trakmaster, swear by the carefully positioned ‘scupper vent’ fitted to the forward roof section of the caravan.

The principle is simple. By pressuring your caravan positively, dust will not enter. I can speak from personal experience that this system works. A scupper vent was fitted to the first Jayco Expanda pop-top I bought in 2008 and I have travelled dust-free with ‘pressure hatches’ fitted on various Trakmaster full height caravans and pop-tops over the years.

The vent on my current Pilbara Extreme is topped by an optional cowling to funnel air into the van and according to Trakmaster this $200 option makes a significant difference. However, Trakmaster’s Richard Metcalfe admits there’s no perfect solution, as different tow cars travelling at different speeds will cause different air flow patterns over the caravan.

To find a universal solution, Trakmaster has trialled various systems over the years including different vent locations, but placing the vent too far back can actually create a vacuum and suck dust in.

They’ve also fitted fan-operated units on customer requests, including boat bilge blowers. But the blower must have a 100 per cent duty cycle rating, as it may be running for many hours on end in this application.

Trakmaster have also experimented with filters, but say that these can reduce airflow through the scupper vent by as much as 50 per cent.

THE PERFECT SOLUTION?

Not surprisingly, given their marketing focus on leading-edge technology, Kimberley has developed what they see as the ‘Gold Standard’ in dust suppression.

Kimberley boss Bruce Loxton says the problem with normal pressure vents is that they’re less effective at low speed and this is compounded by the fact that this is when the dust is thickest.

Kimberley’s solution is their patented positive pressure system called ‘Always Positive’ that employs three separate components interconnected like a series of water falls.

These include a high-pressure tank with air at 40-50PSI that’s shared with Kimberley’s optional air suspension if fitted. A small compressor will occasionally cut on to re-pressurise this tank, which has a regulating valve that fills a large volume, lightweight PVC ‘bladder’ at 3-4PSI very quickly.

The system has an automatic flow control valve connecting the bladder to the inside of the caravan with air from the bladder automatically bleeding through to deliver a constant 0.1PSI increase inside over the outside pressure.

The compressor and pressure regulator come on only when the vehicle is connected to the caravan and the ignition is on with a signal to the caravan. An air filter is fitted outside as an air-cleaner before the compressor, which doubles up as a tyre-inflating device.

The bad news is that you’ll need to spend around $165,000 to enjoy it, as it’s only standard on Kimberley’s top-of-the-range Black Caviar tandem off-roader.

THE DIY OPTION

If you’re looking for a cheaper solution and you’re fairly handy, here are some DIY ideas we found on various caravan forums, although we can give no guarantees about their effectiveness:

• You can buy a scupper vent online for around $60 and fit it yourself, but it will be a matter of trial and error as to whether you have selected the optimum location. Remember that the van is travelling in the tow vehicle’s dust.

Also, remember that you only need to open the scupper when travelling off-road, otherwise you’re creating unnecessary pressure on your caravan’s window and door seals, particularly if cruising at up to 110km/h.

• After sealing every gap and pinhole as best as you can, set up a 12v fan that draws air in through an air cleaner and in to your van. If you get the volume right, clean air will be blown out of any leak and dust will be discouraged from entering.

• Four-Season or Fantastic hatches won't work at speed to solve the problem. They are made for normal breeze blowing over the van when stationary and you may damage them if they are open at highway speeds.

• Wheel arches are the biggest culprit in on-road vans and the hardest to seal. Get inside the cupboards with a can of expander foam and silicon. Also, put extra foam sealing tape inside the external hatches.

• If you know you’re going to be on a dusty road for any time, don't run the fridge.

• Put a plug in the shower drain and a thick piece of foam rubber into the four seasons vent. Although it’s illegal, some people place bathroom flannels or foam between the door and screen door to filter dust from coming in through the gas vents.

Don't bite the dust!

Tags