A swamp cooler is an evaporative cooler that cools the air by blowing it through a moist filter material.
You’ll need a plastic trash can that you cut 3 inch holes all around. In the lid you’ll cut a hole for a 10 inch car radiator fan. You line the trash can with evaporative cooler plastic filter. Drill several small holes in the bottom of the trash can.
The trash can sits in a beer keg tub full of water. Get a 12 volt boat bilge pump and connect the outlet to a hose that rings the top of the filter media. As the bilge pump brings water up to the top of the trash can, the water trickles out of the ring of plastic you attach around the top. As the water flows though the filter, the fan sucks air into the trash can and as the water evaporates, it cools and humidifies the air. I used a ten inch air-conditioning duct to pump the cool air into the top vent of my camper.
The whole rig ran all day long and kept the camper very nice for afternoon naps or just a great place to get away from the dust. We turned it off at night. One 100 watt solar panel and a deep cycle 60 amp hour battery worked perfectly.
I’ll get more of the specs and info for your build soon.
And here they are! This is a video I did for Burning Man HIVE. Their social media experiment. You need to create a Burner Profile to join HIVE but it’s the best place to start your Burner journey https://hive.burningman.org/posts/rat-solar-skill-sharpening-weekly-topic-17-swamp-koolers-16-min-51822
Here’s another great article from another Burner that uses a 5 gallon pail
https://www.instructables.com/Easy-Mode-FIGJAM-5-Gallon-Bucket-Swamp-Cooler/?utm_source=newsletter&utm_medium=email
And here’s a video of a similar 5 gallon bucket cooler that uses a larger fan
https://www.youtube.com/watch?v=aHbQYajfGqM
A followup edit: It didn’t work out as well in 2022. My trailer was broadside facing south instead of the end wise and it was much hotter. Next time I will shade the trailer, better insulate the windows, add an ice tray to the top of the swamp cooler, add an inside filter, and tie my two batteries together to balance my load. Having more battery power will allow us to run it until it cools down after sunset. It did cool the temperature down ten degrees and that was a little relief during the very hot and dusty afternoons. A fellow campmate was getting 20 degree temperature drop from his swamp cooler with shade and an ice tray. We use cooler water for the swamp coolers.