It’s been a hot summer. It’s been a humid summer. Flying in a Sonex during a hot and humid summer can feel like being an ant under siege by a boy with a magnifying glass. There are several solutions out there, but none of them fit well in the small cargo bay. Additionally, keeping weight to a minimum is critical.
My estimated weight completed is around 10-12lb depending on the quantity of ice used. The Amp draw is less than 3 amps. Longest flight has been 2 hours with ice to spare.
The solution for me and my wife was to design our own unit, which would help cool the plane and keep the weight and costs low.
The original design utilized an Attwood 3″ fan inside a 4″ flange. The look was clean and everything fit well. The air volume is notably lower than the new Attwood 4″ Series II fan. The remainder of the blog includes the building of the 4″ fan, although I have not secured it permanently yet.
How well does that giraffe looking thing actually work? Quite well actually. The unit can be used to keep your face and body cool. Depending on the day and how well insulated your interior is, it can keep your face and upper body cool on a sunny 90 degree day or the entire cabin cool on an 80 degree day.
How does it work? It cools the air two ways: 1) warm air is cooled through the condenser then blown into cabin, and 2) removing humidity from cabin.
Air is cooled and dehumidified as it passes through the condenser. The air is further cooled as it passes over the ice water before being sucked up into the fan. The fan blows the cold air into the cabin. I estimate the air temp to be between 65-70 degrees. The 4″ fan blows 200 cfm.
The basics of how it works as drawn by my 3rd grade skill set :):
All parts came from Amazon and the local hardware store. 4 main parts make up the unit: the cooler, fan, heat exchanger and the pump.
The parts list (click on item for a direct link to Amazon):
A: 9-Qt Cooler
B: 4″ Blower (It is important to note the 4″ blower needs to be the new series II. The older model uses significantly more amps)
Additional hardware store parts needed: Plexiglas, screws to secure Plexiglas, nuts, washers, 6′ lamp cord, cigarette lighter plug with built in fuse, 4″ flexible plastic drain spout tubing, electrical connectors, etc.
Tools needed: soldering iron, box cutter, shrink tube, stand off post threaded, drill, dremel with sanding and cutting wheel, etc.
Tip#1: When drilling holes in Plexiglas, start with a small hole and work up one bit at a time to reduce the risk of cracking. Wear safety glasses.
Pretty simple build and pictures are worth a thousand words.
The basic steps I followed were:
- Remove the lid from the cooler base
- Cut the bottom side of the lid off leaving the lip around the edge of each side
- Drill holes for the fan, switch and heat exchanger
- Drill pilot holes for stand-off post, which secures the heat exchanger, 4 corners of lip to secure Plexiglas, power cord
- Cut fan hole in Plexiglas, heat exchanger (Be careful not to crack the Plexi)
- Mount all of the hardware to the lid
- Wire everything up (pretty straight forward wiring)
- Mount the Plexiglas (I used foam door weather stripping to seal off the gaps which is important to do)
Note: I have been testing various fans (2.5″, 3″ and the Series II 4″) which is why the duct tape is being used to secure the fan. I will be securing the 4″ Series II permanently shortly as it works the best.
I used quick connectors on the fan wires so the unit can be easily removed.
We have also been testing the exit port. A cap with holes drilled in it on the edges and the face increase the air volume. It appears to keep the cabin cooler than an open port.
We are installing a 90% efficient carbon heat shield rated at 1,500 degrees (1/8″ thick) under the carpeted firewall and floor board. We are also creating a closure to the cargo area so no heat will come into the main cabin which should significantly cool the entire cabin of the aircraft even on hot sunny days.
In-flight water weight reduction enhancement coming soon:
The next upgrade is to install a drain port 3″ above the floor line of the cooler with a vent line out the belly of the plane. As the ice melts, the cooler becomes full of water. In fact, a 7lb bag of ice fills the cooler almost to the top. The goal is to let the water (all but 3″) drain out of the plane as I fly, reducing weight as the ice melts. 3″ is important to keep the pump submerged.
Please feel free to post questions or comments!
Fly safe and cool. Josh