Waterproofing a Standard Servo

Waterproofing a Standard Servo (well, splash proofing it at least)

The post describes a process I used to protect a standard servo against water.
The servo was a Hitec 919, but most servo use the same basic construction 

The main entry points for water below the mounting flange are protected by a spray coating.

The splined shaft is protected using grease on the inside of the casing and an O-Ring on the outside.

Details of the steps follow.

Step 1.
Partially disassemble the servo by removing the 4 screws from the bottom, and remove the top and bottom casings.

Step 2.
Slide out the Motor and PCB assembly.
Apply a Conformal Coating to the PCB to improve its resistance to water.
I didn't spay it directly, because I wanted to avoid any moving parts, but rather sprayed a few millilitres into a small container, and applied it to the PCB using a wooden ice cream stick.

Step 3.
Apply grease to the bearing area just below the splines.

Step 4.
Reassemble the servo.

Step 5.
Add an O-ring  (1mm by 4mm) to splines.

Step 6.
Use a file on the bottom of the servo arm splines, to increase the gap between the top of the servo housing and the servo arm.
The gap needs to be increased so there is enough room for the O-Ring when the Servo Arm is screwed down, without it being too tight ,and causing undue friction.

Step 7.
Apply a protective spray coating lower part of the servo below the mounting flange.
I used masking tape and Red Plasti Dip.

Unfortunately, I forgot to take a photo before installing the servo back into the Wingsail, and this photo is not good.