Fighting dust intrusion with a 12v fan - positive cabin pressure

EDIT:

I decided to simply weatherstrip the hell out of my tailgate and rear hatch (as well as seal with silicone all drainage holes and gaps in the composite bed / storage compartments). See post #6 below for a more thorough explaination with photos of the weatherstripping application.

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TW,

I recently upgraded to a Snugtop Rebel on my '12 DCSB. I have a set of ARB drawers, constant hot Blue Sea fuse panel, and a fridge in the bed. My future plan is to add some L-track and an upright water tank.



I have been slowly tracking down the problem areas for water/dust intrusion. The water part was easy - copious amounts of silicone under the lip at both front corners has solved that problem.

The dust has been a different story. Those little particules defy gravity and work their way into every tiny crevice around the shell.

To combat this I installed a purpose built 3M bulb seal around the tailgate and the lip on the rear window/hatch. I also filled the drainage holes at the front of the bed and the seams at the rear of the bed (near the bed channels) with RTV silicone. I would say the above modifications blocked about 90% of the dust - but the really fine powder it's still getting in and coating my bed. There are a few spots that simply cannot be sealed well with weatherstripping or silicone.

After searching on the net, I came across an interesting idea. A few forums mentioned that a small fan/blower can be used to create positive pressure inside the cap to keep the dust out. Although this was referenced as a possible solution, I could not find any photos or write-ups mentioning it specifically in a how-to format.

What I'm considering is installing a small computer fan in the back storage cubbie near my fuse panel. It would pull air from the outside of the bed and blow it in; thus creating a small amount of pressure which should, in theory, create an outward blowing draft at every minute gap between the bed and shell. My plan is to power the fan via a relay that is triggered with an ignition hot power source - when the truck is running, the fan would automatically cut on. A switch near the fan would interrupt this circuit if need be to turn the unit off.

I'm currently researching a way to filter the fan to keep it from ingesting dust and defeating its purpose. This shouldn't be a problem as filters are cheap and readily available:



The filters would be a regular maintenance item that I would plan on changing in tandem with my cabin air filter (unless they clogged sooner).

What do you guys think? Any input is welcome. I'm still in the planning stage, but I think this would be a simple and affordable modification.

 

Look at some of the Aussie 4wd sites. I've seen several articles on how to create pressure in the back, unfortunately I didn't save links to any of them.

 

Thanks for the lead. I'll do that and link them here.

 

It sounds like dust is a big problem in Aussieland. It must have something to do with that giant desert

I checked out about a dozen threads on various Australian 4x4 touring forums and the general consensus is positive pressure works at repelling dust. Lots of write-ups and testimonials, so at least the concept is sound with plenty of evidence-based results. However, no one referenced using a fan to create the pressurized cabin. Apparently, air vents are a popular modification on camper shells (or canopies as they call them) as they create the same effect. The best thread I found detailing said vents:

http://www.4wdaction.com.au/forum/viewtopic.php?f=177&t=148488

Some photos:


Well, I'm not going to cut a hole in my new Snugtop, but it's good to know I'm on the right track. I'll take the periodic filter change over a vent that needs to be opened and closed all the time. I know me, and I would forget to close it overnight during a thunderstorm - not good.

That being said, I found this mounting plate for dual 60mm computer cooling fans:

https://www.coolerguys.com/collecti...-2-hole-bare-kit-80mm-kit-for-cabinet-cooling




It measures roughly 8"x4.5" and will hold dual 60mm fans. This plate will cover one of the front bed cubbie holes perfectly and allow for increased airflow with two units. I'll also have some redundancy in case one of the fans fails. According to my measurements, I will still be able to mount a filter on the fans themselves, or on the inward facing part of the plate.

Time to pull the trigger on some hardware.

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EDIT:

I think this unit will actually fit the cubbie hole better. The storage bin will have to be removed, but there should be minimal trimming involved:

https://www.coolerguys.com/collecti...le-bare-kit-dual-92mm-kit-for-cabinet-cooling

 

Another thought - does anyone know if there is a wire at the rear of the second generation Tacoma that is ignition hot? I would rather solder in a fused trigger wire for the fan relay at the rear of the vehicle as opposed to running a wire tap from the dash fuse panel all the way to the rear of the truck.

 

Before undertaking this modification, I decided to purchase some high quality bulb seal - about $45 worth in all - and attempt to completely seal the tailgate and rear hatch area. I also ran a bead of silicone in the crack between the bed and the metal bed sides at the rear of the bed. The interior bed cubby doors were removed and each hole covered with a small piece of aluminum HVAC tape - same for the drainage holes in these compartments. The drainage holes at the front of the bed and the front storage cubbies were filled as well.

After a trip to the Otero Mesa, NM (lots of dusty dirt roads) and a run on the White Rim Road in Moab. I can say that I have all but sealed out dust from the bed. A small amount of very, very fine moon dust will be present on the top of my bed reinforcement brackets if the conditions are very dry and dusty; this I can live with. A quick wipe with a paper towel and it's gone.

That being said, with these results I will likely forgo the 12v fan modification as I think it's not really needed.

Here are some photos of the weatherstrip work that I did to the rear of the bed. For reference I used a Lund 3M tailgate bulb seal kit (for the tailgate area) and another 3M bulb seal strip for the rear hatch and tailgate (purchased at PepBoys). The key here is to buy a 3M product that will adhere well. Also, I probably spend 30 minutes prepping the application area with alcohol wipes. Just like paintwork, great results come from great prep work.

 

Nice work!

 

A friend of mine used positive pressure in his Frontier. He keeps the sliders open and an innertube between the cab and shell. HVAC on fresh, not recirc. Works for him. I've also read that Bedrugs help quite a bit.

 

I found that careful gasketing of the tailgate and a few other gaps was sufficient on my Tacoma. However - and I say this with zero actual experience - I wonder about the positive pressure concept, at least with a small fan. Even though a foam or paper filter provides lot some of surface area, I'd think it would clog up pretty fast. That's based on thinking of the surface area of the bed, or even just the area around the tailgate, say a couple of square feet, that gets covered with a fine coating of dust in just a few miles of dusty road. Now compare that with even a 120mm fan's surface area. Maybe an automotive air filter upstream ... but even a clean air filter may be more pressure drop than a little DC fan can handle.

 

the vent in the first post looks like an awesome way to control moisture while sleeping. any links to that one specifically?

 

I found those photos on an Australian 4x4 forum awhile back and didn't save the link. I think it's an option that most topper manufacturers in Australia offer as an option. Dust is a big problem in the Outback. I'm sure with some work you could find some more info online. The Aussies refer to toppers as "canopies" - try that in your search.

 

Yeah - it looks like it's actually an ARB product, but not sold in the US.

 

Oh yeah, I forgot I posted the link. ARB makes a lot of gear that's not available in the US. They have their own line of toppers for the minitrucks in that market.

 

Great news - my buddy is going to OZ soon. I'm going to have him pick up 1-2 of those cool vents for me. BOOM.

 

You can get them here, they're sold as trailer vents (two way pop-up roof vent).

Low profile:
https://www.amazon.com/Aluminum-Pop...D=41wljkeRrkL&preST=_SX300_QL70_&dpSrc=detail
Scroll down about halfway for high profile:
https://www.etrailer.com/dept-pg-RV_Vents_and_Fans-sf-Roof_Vent-pc-No_Fan.aspx

 

ARB has more street cred.

 

True, unfortunately with the price to go along with it. Looks like they're about $72 kangaroo bucks right now http://www.all4x4.com.au/d259-169/exterior/canopies/arb-canopy-vent/. ARB part number 4700010. The only issue I could see is that they appear to be designed for ARB's shells which don't have the thicker, honeycomb material section like a lot of the US manufacturers use (my ARE has one for example and so does a friend's Leer). I can't find actual dimension specs on them to see if I could make one work. Be neat to have though I expect I'd forget about it most of the time or with my luck, leave it open when it was raining.

 

I had a 1958 alaskan pop up camper for a while. It stuck up slightly above the cab and had a small window you could open to pressurize the camper when running on dusty roads! Not my pic but you can see the small window above the cab.