Pressurising/cooling canopy

A lot of canvas canopies have two flaps on the front that, when open positive pressure the canopy while the vehicle is in motion. Have a few mates that swear by this system, I have a rigid canopy and I purchased a secondhand heater fan that I use drawing through a Holden V6 flat panel air filter. It's can be a bit heavy on power though.

On the canopy of my ranger I used a home made version of a ship's scupper vent where the air is forced in and has to go slightly forward to go down into the canopy
The white bit you can see in the roof is a cut off plastic plumbing fitting that has the rear of it ( can't see here ) cut down so there is only a ridge facing forward.

As you can see the air has to go down into the canopy and at the back of the scupper I cut about a 5mm hole for any water collected to be blown out the rear.
This pressurised air then goes out all the little air gaps etc that usually the suction at the canopy brings all the dust in through.
It was a bit of a ''trial and see'' but we've just done 30.000 K trip around Aus and dust in the canopy ?

Mine is a white painted ally box with no vents. I thought about them, but was in a hurry to finish it and was going to see how it went and fit them later, but then decided not to bother. Some guys I know fitted solar powered ventilators, but for the amount of air they shift I don't know if it would make that much difference.

Mine does have a roof top tent on top, so that works for shade/tropical roof and stops it getting too hot. Some foam insulation bonded into the roof would probably be of more benefit than a fan, better to keep the worst of the heat out in the first place.

During the day when driving the fridge copes no worries as it has the extra Amps from the alternator, when stopped the side doors are generally open or the sun is going down,so it doesn't get hot then either.

If you do go with some vents, look at how they do it on cars. Inlet high at the front (You can get clever with air filters on the inlet if you want) and outlets on the sides towards the rear. Thin rubber flaps are enough of a seal, provided you have fresh air coming in the front. Don't put them on the back as then they will be more likely to suck in the dust that swirls in the vortex behind the vehicle..

I presume you're getting an alloy or steel tradie type canopy.

I have a fully sealed tradie canopy with no airflow at all to ensure dustproofness. I run my compressor fridge as a freezer. It does not suffer unduly in the closed canopy - my frozen stuff remains frozen. If I were to use it as a normal fridge I would expect a similar result.

When the canopy is sealed up when driving I presume the compressor runs more, but that doesn't matter because then it is powered by the alternator system.
When camped and the fridge is running off the second battery the canopy is usually open or partly open for ventilation.

To get positive pressure you need an air inlet but no outlet, so there would be little or no air circulation and therefore little or no practical ventilation benefit for your fridge.

If the door seals are done right I don't think you need positive pressure, and in my experience the lack of incoming air makes no difference to the fridge's performance.

The subsequent lack of dust is the huge benefit.

Thanks for the prompt replies. So it appears that a sealed alloy canopy will be better off remaining sealed and minimising heat via coverage on top (will do) and insulating, rather than bothering about a fan?

Certainly makes life easier (I'm going to insulate anyway, and really can't see myself stopping regularly to open or close a vent).

Cheers,

Mark

I have a 2007 build 79 series single cab 100,000k.on dirt roads has a 40lt engel inside no dust at all.
Will have a dog shortly so have to have a rethink.

I have a Concept Canopy made in Brisbane. They have a vent on either side. One at the front and one at the back on the opposite side. On dirt roads I simply open the front and close the back vent which pressurises the canopy and no dust. Otherwise I leave both vents open which allows airflow through the canopy. The airflow helps a little when I carry fuel for the outboard/chainsaw etc. If sealing completely be careful of carrying gas bottles. I am not an expert but if these leak in a sealed unit ????

G’day all,
My experience is,
A few years ago I had a 40 litre Engel in the back of a freestyle cab. I found when closed up and hot, the fridge wasn’t cooling and was running the aux. battery down. Fridges do need cooling air to work.
Now I have a aluminium canopy and I am going to vent/duct air to the fridge, as I have the fridge running all the time , weather travelling or parked while working. Am going to try a thermostatically controlled fan .
Probably ok to not have ventilation when travelling as others have stated , charging while moving and doors open when stopped.
Cheers

Insulation is one of the best things you can do for any metal canopy it will greatly reduce the radiant heat. I have only done the roof on mine so far, it has made a big difference but haven't done the front wall or any of the 3 doors yet.. My neighbour has done his roof and walls with rubber insulation from Clarke Rubber before that you could only hold your hand on the inside wall or roof for a very short time before it got to hot now you hardly feel any heat coming in. Yes it will slowly heat up during the day everything does but it is much better than getting the radiant heat blasting into the canopy.

I have a solar vent on top of my roof and an intake vent in the front wall I put some thin foam in it to reduce the dust and it works well The fully enclosed alloy canopy on my ute can be up to 7 deg cooler inside compared to the cab of my patrol.

When I first put the canopy on a couple of yrs ago, before I insulated the roof and fitted the vent and solar exhaust fan I was travelling on holidays during summer and my Evakool wouldn't get below 5 deg in the fridge section till later in the day. I had it dialed up to 9 which is flat out where as I usually only needed to run it at 4 to 5 around half way. It was incredible hot inside the canopy because there was no air flow or insulation and all of heat trapped inside the canopy I'm surprised the fridge survived.

ARB canopy on tub.
ARB rear mounted pressurising vent.

150k, much on SA and NT back roads and deserts, never get more than a cm of dust in the jamb.

I leave it open all the time.
Only in very heavy rain and highway driving does it need to be shut, or a very small amount can be blown in over time, but then dust is not an issue :)

Never an issue with dust from oncoming (passing) traffic, it is brief.
If behind a vehicle, or in convoy and the dust is bad, I stay back far enough to avoid dust plumes, if wanting to overtake I'm patient, and / or call on the 2 way to arrange the process in a good manner, or just sit back and enjoy the small differential in speed.

Dust just blows over, the very minimal amount that may go into the open vent, goes straight out through the open tailgate jambs.

I have a aluminum fully sealed canopy by Metalink it is gunmetal grey but we painted the roof and the inside off white and we also have two solar panels on the roof it is dust proof and reasonable cool inside with the panels keeping the direct sunlight of the canopy plus the white roof.

We've got 2 canopies Mark. One is sealed and the other, which we use in the desert, has had 2 forward facing vents fitted. These are the ones sold by ARB, about 75 x 200mm and cost around $70.





Being bare alloy it gets very warm, but don't seem to have had any dramas with the fridges. I often leave the sliding window open, depending on wind direction. The amount of dust that gets in is minimal, but might be different on heavy bull dust tracks. You might be able to swing your CEO to getting a white roof, to help with cooling?

Very easy to go overboard with accessories for these canopies, making them ultra heavy and threatening the vehicle's GVM. Couple of things I've done to restrict weigh gain is an upright fridge, and Oates plastic drawers, from Bunnings. The 80L upright is only 5kg heavier than a 40L Engel, and saves using a heavy dropslide. Plastic drawers are okay, but heaps lighter than a pair of Titan drawers at 60kgs empty.

Good luck with your build, it's fun............and expensive!

Bob

I am sure one thing not touched on here in this thread, or the numerous past similar threads, is . . . if you are pressurising to keep dust out, you NEED an opening for escape like tailgate jambs, or some may feel general loose canopy doors on theirs is enough.

All you need is slightly more air coming in, than can escape, and this seems to work at speeds over say 20ks or so in my experience.

The vent at top is also good for allowing hot air rising to escape when parked, in camp, etc, a little more bearable at least.

Just wandering if anybody has put in vents in there canopy head board, like in the fridge box of a T-VAN [fluted vents outside with air filter held in place on inside] with Muller vents down the back of the roof. Muller vents will suck filtered air through front vents on move, and then Muller vents will let hot air escape went parked, this is what I am thinking in next build.

Matt

Hi Mark

I have an aluminium canopy with no vents and no dust or water ingress. It has 2x120 watt solar panels on top and an Engel 60-litre fridge that runs constantly.

This current one has done circa 120,000 kilometres of outback travel, and a previous vehicle had the same set-up (different canopy) and was the same construction.

My experience has been a well manufactured canopy appears to remove the need to have vents or be pressurised for dust. And while on a hot day the canopy temperature does increase with the ambient temperature the Engel never misses a beat even after 12 years of constant running.

Both of my canopies have been manufactured by Dave Vella, Dave's Metal Products in Sydney.

Good luck with your research...

Cheers, Baz - The Landy