Custom truck camper, let's talk materials

#16
I'm now keenly interested in this air circulation problem. I will have mini split air conditioner so there is no internal/external air exchange involved with that. I believe it will dehumidify the air which I do need to pay attention to draining that. Given that I can regulate the interior temp cheaply (energy wise) how do I get fresh air in and keep the Co2 and Co levels under control?
 
#17
Thanks for sharing this. I think there are a number of Aerogel products. Which are you familiar with? I'd like to investigate this further.
The makers have made it very simple. The stuff used for high performance insulation is a specific product. You would only get a different product if you needed high temp as well. Applications like insulate your exhaust system.
You will want "spaceloft"
https://www.ebay.com/itm/Aspen-Aero...m570.l1313.TR12.TRC2.A0.H0.Xaerogel.TRS0.TSS0
 

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#23
Having positive pressure only matters when you are moving, so I would think you could achieve that pretty easily. The pressure required is pretty low. Something as simple as a computer fan drawing from a filtered intake would do it. It's not totally passive, but extremely low draw. I think drawing from the engine induction system would create smells and pollution in the cabin. You need good gaskets for sure.

I'm now keenly interested in this air circulation problem. I will have mini split air conditioner so there is no internal/external air exchange involved with that. I believe it will dehumidify the air which I do need to pay attention to draining that. Given that I can regulate the interior temp cheaply (energy wise) how do I get fresh air in and keep the Co2 and Co levels under control?
This is a tough one. The amount of air turnover to remove unburned hydrocarbons and combustion byproducts is pretty low unless you have some leaky and inefficient systems in the cabin. During cooking times, you may need more. The amount of turn over to stabilize O2 levels is also surprisingly low. Moisture removal is a big environmental problem, but if you have a way to handle that you can close things way down. Here's the problem though. Most RV manufacturers issue recommendations for air exchange that are 10x, or more, higher than you actually need. They do that for liability reasons. It doesn't really concern them that your furnace is running constantly to keep up with the massive heat loss this creates. It doesn't concern them that your fuel requirements are huge either. I'm reluctant to tell you what I know too. I will say that this issue is worth looking at. I also think that any attempt to minimize air exchange should include a monitoring system for key indicators. A gas leak, CO build up, or compromised O2 levels need to be detected. I have created such a system using an Arduino based electronic platform and commercially available sensors. Being able to see what is really happening in real time is extremely interesting. The system should always have a minimum passive exchange designed in, that is not susceptible to mechanical or electronic failure.

The makers have made it very simple. The stuff used for high performance insulation is a specific product. You would only get a different product if you needed high temp as well. Applications like insulate your exhaust system.
You will want "spaceloft"
https://www.ebay.com/itm/Aspen-Aerogel-SPACELOFT-Insulation-Hydrophobic-Mat-Per-Linear-Foot-6mm-24/380906349501?hash=item58afc9a3bd:g:eek:l0AAOSwo~la9DpC:sc:USPSPriority!95136!US!-1&_sacat=0&_nkw=aerogel&_from=R40&rt=nc&_trksid=p2380057.m570.l1313.TR12.TRC2.A0.H0.Xaerogel.TRS0.TSS0
Thanks Aernan! I love finding new materials to work with!
 
#24
This is a tough one. The amount of air turnover to remove unburned hydrocarbons and combustion byproducts is pretty low unless you have some leaky and inefficient systems in the cabin. During cooking times, you may need more. The amount of turn over to stabilize O2 levels is also surprisingly low. Moisture removal is a big environmental problem, but if you have a way to handle that you can close things way down. Here's the problem though. Most RV manufacturers issue recommendations for air exchange that are 10x, or more, higher than you actually need. They do that for liability reasons. It doesn't really concern them that your furnace is running constantly to keep up with the massive heat loss this creates. It doesn't concern them that your fuel requirements are huge either. I'm reluctant to tell you what I know too. I will say that this issue is worth looking at. I also think that any attempt to minimize air exchange should include a monitoring system for key indicators. A gas leak, CO build up, or compromised O2 levels need to be detected. I have created such a system using an Arduino based electronic platform and commercially available sensors. Being able to see what is really happening in real time is extremely interesting. The system should always have a minimum passive exchange designed in, that is not susceptible to mechanical or electronic failure.
To break down the points:

  • Cooking gases
    • I'm planning on using an induction cook top but may do propane cooktop. So I could get no gasses except food smells here.
    • In addition I am adding a large window behind the range that I can open and considering some kind of hood or fume extractor.
  • heating gases
    • Heating will by done by diesel fired hydronic furnace that is mounted external and has it's own dedicated exhaust system. The Mini Split AC acts as a "heat pump" as a backup. So no gasses for me there.
  • human respiration - O2, CO2
    • This is my biggest concern and I would love a system to monitor and alert. Please tell me more about the arduino based solution.
  • Humidity
    • Sink/Dishes
    • Shower Bathroom
    • Wet clothes/boots
    • regular respiration
    • cooking (evaporation)
To control humidity I expect the AC unit will dehumidify and drain. In addition the hydronic heat source will be piped into every locker/closet to help dry interior spaces. Should I look into a stand alone unit to dehumidify?

Regarding the Engine Air filter.

The LMTV has a giant air filter. I just pulled one out today. It's 1' wide and probably 3' long.
http://www.oshkoshequipment.com/products/detail/49/5296/Air-Filter-Element-M1078-and-M1083
After that air filter I would probably want to do a much tighter filter or active charcoal to remove any other dust/smells.

System Design Ideas:

I imagine some main air passage with a large bulk air filer. Then pass into the living space and a second replaceable HEPPA style filter. Then a squirrel cage fan and/or low power booster fan. Maybe search HVAC stuff. Then a set of shutter louver that closes when there is no air pressure.
From there the air should circulate and exit a different shutter louver.
 
#26
A few comments about the structure and material.

Using larger steel beams spaced further apart to gain the same strength with additional wall thickness for insulation and fewer beams for fewer thermal bridges vs aluminum. Maybe 1.5" x 1" or 1.5" x 1.5". OR 1.5" square for all the main edges/corners, and 1" on the inside or outside plane for fewer thermal bridges.

If square walls using foam sheet in between the beams. Sheets are easy to cut, are square, and can be purchased locally/cheaply in various thicknesses. Seal the edges with spray foam cans. If you go the 1.5" square main, and 1" square filler panels you can simply use the thinner 1" sheets for in between the 1" square tubes, than cover the full span with a 2nd layer of 1/2" sheet to stop the thermal bridges in all but the corners. Window structure can be the 1" square, so the additional 1/2" sheet will help there a bit too.

Use aluminum sheet riveted to the outside ala' the Airstream method. Check Airpark Supply for the different types and thicknesses. I found them to be the best source when doing my Airstream. Rivet using Olympic blind shavable rivets from the outside, or standard wide flange pop rivets can work too if you want to add additional sealant. They make a Trempco product and Sikka products for sealing up Airstreams. Vintagetrailersupply and airstream supply are good sites to use. They are urethane based, and lasted 45 years on my Airstream without leaks, so they work well enough. I used them when modifying/repairing/re-sheeting the Airstream with good effect. Vintagetrailersupply is a better source, but it comes from VT, so it takes a while. Airstreamsupply is OK, but I have had issues with incorrect items, and their communication is lacking at best...especially on backorder situations. Airpark supply was better for sheet aluminum if you don't already have a source. Even if you do have a source for sheet aluminum, you can use the site to get ideas on thickness. I think I used .028". Since I was polishing, I needed Alclad. You can go cheaper if painting, so don't waste your money there.

On the inside you can use sheet metal, ply, plastic, other. Perhaps put a layer of foam flexible insulation just inside the ply (or whatever you choose) inside walls to help reduce a little bit of the thermal transfer at the corners. The screws will still carry some. You know, the 1/4" near cloth like closed cell that they use in similar fashion to reflectix for windshields, etc.

The nice thing about all this is that it is repairable when away from the garage. Rivets can be drilled out and replaced if sheeting needs to be addressed, screws/rivets on the inside as well. Steel can be welded in the field if you have a battery welder, or if not can be welded in most countries whereas aluminum take a higher skill set (as you well know). Sheet insulation can be routed or hand carved to allow wire passages through the walls if you need to retrofit.

Since you have a relatively small space, and are using an F250 which is likely diesel, go with a diesel air heater. You have a fuel source already, they don't have to be vented due to CO2/Oxygen consumption, and put out dry air. Do some Tern windows or other double paned ones to avoid condensation, and you will really only ventilate to cook/shower/comfort. The space you are heating is relatively small, so the diesel air heater should be more than enough.

When you are more comfortable with composites etc., sell this one, take all the info you learned, and built out one of those. You may find that you don't need to though unless it is a weight issue.
 
#27
Steel vs Aluminum beams:
steel is cheaper and easy to weld. You can make aluminum as strong as steel and lighter but it will be bigger. If you are welding aluminum the process is more expensive.

Hollow tube stock vs channel:
I would prefer of there are no voids in my structure so I am opting to make mine out of hat profile instead of tube so I can fill the interior of the beams. It may be possible to fill the tube but you can't fill + weld because it would melt the foam.

Foam sheets vs blown in foam:
The stuff sold at home depot the XPS (ping stuff) has an R value of 5.
Open cell has a value of 3.6 and closed cell of 6.5
So I am going to opt for for closed cell spray foam. I will insulate the interiors of the sealed beams with XPS for simplicity.

I agree the fewer beams you have the lower the thermal bridging will be.
 
#28
Voids in structures. Just thinking out loud here, but a hollow tube is an air gap, in a similar way to the air gap between window panes. Curious about the necessity to fill those voids.

With a tube steel frame, one could also weld eyelet lifts on top of the camper for overhead lifting. Not as much of a use for a camper back vs. say a medium duty truck big platform type habitat, but could be quite useful in the right situations.
 
#30
My truck has a massive air filter for the engine. Would there be any harm tapping into the air line post filter for the cabin?
Lots of good info here, but this is not a good way to achieve positive cabin pressure.

In essence, an engine is an air pump. It sucks in, compresses, and blows out. So the only pressure an engine creates is during and after combustion (or after a turbo or supercharger, but moot point here). If you were to tap into the intake after the air filter, you are creating a new place for the engine to pull air from that is not filtered, which is exactly the opposite of what you're trying to achieve and would create a vacuum on the whole camper. Additionally, intakes are rather noisy and if the camper is open to the cockpit, it would add a noticeable amount of sound while driving.

If you've ever noticed on cargo trailers. there is usually a forward facing intake vent mounted high and towards the front wall. There is no corresponding exit vent. This creates positive pressure in the trailer while in motion. It's mounted as high as possible to avoid contamination from the tow vehicle and though it's not perfect, it is effective.
 
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