My Aircraft sits outside and always has a cover left on. For 3 years I have been putting in 2 containers about 15 cm x 20 cm by 6 cm deep (6″ × 8″ × 2 inches deep) full of Silica Gel beads. The beads are 5 mm. One container sits in the front, one in the back
This does seem to reduce the relative humidity inside by about 10% and when I put the beads in, I never have condensation on the inside of the windows.
Three years ago, my original plan was to pop a solar panel on the wing and install a small computer fan to blow the air through the Silica Gel beads. This project never happened but my question to this very knowledgeable form is do I need a fan? Does the lower relative humidity next to the Silica Gel “suck” the moisture in at fast enough rate that I’m wasting my time?
The cabin volume is a PA28, reasonably well sealed due to the cover always placed on (the seal on the baggage door is not great though). Should install the fan or not? Perhaps a more sensible question should be what levels of Humidity are acceptable? I have digital monitor that can store months of data so can download the conditions inside the cabin.
My tests, posted earlier, suggest that forced air through the dessicant is not needed if you just leave it in the cockpit. I say this because it comes out after a week or so apparently having absorbed as much as it is going to absorb. But I haven’t tested forced-air so this remains conjectural. One issue is that you would need to power the fan somehow and the battery required for 1 or 2 weeks is not insignificant – of the order of 0.5kg lithium, to drive a small PC-type 5V fan.
If you want to force dried air up the exhaust or up the crankcase breather, etc, it definitely needs to be forced.
Calcium chloride is deliquescent, and the resulting fluid is an electrolyte. Not good if spilled in an aircraft.
The Aero 360 has a reasonably watertight reservoir, but it can easily leak if tipped over. So to avoid that possibility I keep a couple of them permanently in a plastic washing up bowl, so there is no likelihood of the liquid spilling on to the aircraft. (I remove the bowl complete with the dehydrators before flight.)
I have the big one with 2 tablets in my trailer and it reduces the relative humidity by about 5-10%. Have to insert new tablets each month or so in winter. During the other time of the year I open the doors from time to time to exchange the air inside. However I have the trailer parked at home.
I have heard rice will do the same thing as silica? Changes in atmospheric pressure will push air in and out of cabin, and there is nothing you can do about it. A fan could increase the rate of changing air, which is opposite of what you want. Heating up the cabin, is a much better way to reduce the relative humidity. The other way is to have a tiny steady flow of dry air into the cabin.
It will be nice to ventilate on sunny days maybe ? A solar panel will do this automatically.
