It hardly ever rains in San Diego where I live but when it does, like all FPV pilots I know, I stay home and watch my weather app.
Many pilots use a silicon-based conformal coating as a best practice to protect from situations like wet grass causing a water induced short on the PCB.
But is it enough to fly during a rainstorm?
This is what I wanted to find out. I saw on the weather forecast a storm front rolling through San Diego in a few days so I decided to test this out.
Here is the conformal coating that I normally use on the ESCs of my race quads.
Its available on Amazon for around 10 - 20 USD and it has a nail polish type brush attached to the lid for application.
Here is how I used it:
First thing is to build the quad to completion and actually fly it to be sure all your components are working properly. You can also use an existing quad, but you'll want to be sure to clean the electronics before applying the conformal coating. This is what I did.
Remove all the electronics and any shrink tube you have covering any PCBs.
I often fly at the beach and as you can see above some of my electronics were starting to build up corrosion due to the moist air on the coast.
My ESCs had heatsinks covering the FETs so I removed them and set them aside to reinstall later.
The dirt you see NEEDS to be removed before applying coating. I used a toothbrush and isopropyl alcohol.
Next, desolder the motors and get new shrink tubing ready to re-cover the ESCs.
Now liberally apply conformal coating to both sides of Flight controller and ESCs.
CAUTION:
DO NOT apply to the boot button, USB port, or motors as they will become essentially useless. For the best possible waterproofing, I also coated connectors. Keep in mind that this will make it very difficult to ever unplug these connectors.
I use an air can to blow coating between small openings like these capacitors.
You can use a blacklight to see if there are any spots you missed. The picture below shows a spot in the upper right that was missed. Below that is what it should look like.
For the FPV Camera, I removed the PCB inside the housing and coated it being very careful not to get anything on the video sensor.
For rain flying, I also recommend using Rain X or equivalent to help water bead on the lens. It will make it much easier to see when flying.
All the same applies to the VTX and RX. Don't coat the bind and VTX channel buttons.
Let everything dry overnight.
Reinstall everything, shrink up all the shrink tubing you are using and you're good to go.
A few things to remember:
- Anytime something is desoldered or resoldered you must reapply conformal coating to the area
- Isopropyl alcohol will remove coating if needed
- It may be a good idea to seal up your batteries and coat the solder side of the xt60 as well as wrap a Butyl Sealant Tape around the connector joint after plugged in. I did not do this and it didn't seem to matter
- Since trying this, I have 7 batteries flown in the rain and several more after and have had no noticeable issues. I will update this blog if any of the 2 quads I flew in the rain have any issues. Please don't hold me responsible for any issues that arise from trying this method