DIY Thermal Pack/Inner Canvas

TacoBell

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Apr 3, 2024
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Thought I'd post my recent project up here in case others had questions or wanted to create something similar. I used a post here by ski3pin as a starting point for my build : https://www.wanderthewest.com/forum/topic/5269-building-an-arctic-cold-weather-pack/

If anyone is interested in the details let me know and I can get better pictures or a do a more informative writeup. I started the build having zero knowledge of sewing and learned/improved as I went so this is definitely a doable project! Total time spent was about one weekend ~20ish hours

Materials list:
Barricade Barrier Fabric (Seattle Fabrics) - similar to the fabric used in the link above ~7 yards ~$160
Adhesive/Sew-on velcro $100

Starting point - 1992 Hallmark LaVeta. It comes with a three-layer pop up material. Canvas-like material on the outside, a foam midlayer, and a thin polyester(?) inner. The inner layer durability is questionable and was falling apart when I got the camper so I cut it out. What you see is the foam midlayer.

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I started with creating four panels for each side of the camper with plans to cut-in the windows after test-fitting the panels. The panels attached on the top and bottom using adhesive velcro stapled into the ceiling/camper walls. The panels attached to each other using an overlapping tab of velcro on the end of each panel. I sewed buttonholes for all of the bungees that pulled the canvas inwards when putting the roof down.

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Once I test-fit the panels, I used a bright external light to trace out the window outline. I then cut the windows out with a generous hem.

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I have heard of condensation issues between the thermal pack and the outer canvas before so i wanted to prevent that with this project by minimizing the ability of the humid air inside the camper to invade the air space in between the inner/outer layers. Each window has velcro on both sides. One side of the velcro mates with the velcro from the original window. Hopefully this prevents humid air from getting in between the layers. The original windows attach to the velcro on the interior side of the thermal pack. Hopefully this makes sense.

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Finished product

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Wow, nice work. And good thought about moisture getting between the layers. The arctic pack I have uses a breathable fabric, so moisture would get through anyway.
 
Looks nice.

Please be aware that water vapor molecules are very small on the order of 0.27 nm in diameter. That is why water filters are able to filter out viruses that are 0.1 micron (100 nm) to .5 micron (500 nm) in diameter You cannot keep water out using velcro or any fabric that can breathe. Humid air will permeate every space.

If there is a cool surface between the inside of the vinyl wall and the inside of the liner that is at or below the dew point water will condense on it. In general, the higher the humidity the more water will condense on that cold surface.

The two main sources of water vapor are your breath and the biproduct of burning propane from a stove. Your skin also continuously produces some water vaper through transpiration and most of the time it is imperceptible (referred to as insensible perspiration).

All of the OEM heaters are vented so they do not produce water inside the camper.

While there are many actions one can take to minimize condensation, it is very challenging to eliminate it in our pop up campers. Often out of sight is out of mind and when we do discover the condensation problem it comes with a surprise, such as wood damage, mold, etc.

Therefore, I suggest that it is best to assume it will happen and to check for it and take measures to dry things out before closing up your camper.

The recommendations at the following link are applicable to all pop-up campers:

https://roofbunk.com/blogs/roof-tents-101/top-best-ways-how-to-stop-condensation-in-a-roof-tent

P.S. We frequently check behind our liner and it is not at all unusual to find condensation on the inside surface of the main vinyl side. We peel back the liner as far as necessary to access the areas with condensation and wipe down the side material, then air out before closing up. Seems to have mitigated musty smells and mold formation since we started doing that more than 5 years ago.


I hope this is helpful,


Craig
 
Vic Harder said:
Wow, nice work. And good thought about moisture getting between the layers. The arctic pack I have uses a breathable fabric, so moisture would get through anyway.
Agreed. Very cool. I did look up the Barrier fabric you used and Seattle Fabrics does say that it uses a "breathable film", so hopefully that will help with moisture issues.

I like your concept of having the original windows velcro to your new liner.

This is a project I keep thinking I should do, but something else keeps distracting me.
 
Is the thinsulate sandwiched between to thin panels more insulating than the Barricade fabric? Also, we have a Northstar so I want to leave it up and still have the fan suck in the canvas. Any input?
 

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