Personally, when fitting out a bare hull I install all hardware onto the transom first before moving onto the boat’s internals. First job is to find centre and install the strut, then mount my rudder on the RHS of that. The reason being rc boats always race in a clockwise direction and that keeps the blade in the water at all times while turning.
You always want to mount the rudder first, then work the servo position around that, never the other way around.
There are multiple different styles of servo mounts available these days. In the end the servo will either lay on its side or stand up depending on the mount you choose. In most builds its just a personal preference and the end result will be the same. Just remember the goal is to mount the servo arm in a direct line to the rudder arm where possible. If for some reason this can’t be done a small bend in the servo rod is ok, but compound bends will cause trouble. Obviously the closer the servo is to the rudder the better, but you need to be able to access it easily for adjustment or replacement. All the way back is not necessary.
After mounting the rudder simply feed a piece of servo rod into rod joiner hole
and mark the transom for the hole to be drilled. There should be sufficient clearance next to the rudder to allow for the water proof boot. Depending on the type of fitting you’ve chosen to hold the boot you may have to drill up to a 10mm hole. Remember as the rudder moves side to side the arm will not be moving in straight line in and out, hence the clearance.
Lay down servo mounts
A lay down servo mount is just that, the servo is mounted on its side and the servo horn faces up.
Use a single sided horn (servo arm) or cut a 2 sided one in half. Now install the servo into the mount you’re going to use.
To position the servo mount in the boat simply feed the servo rod through the transom and line it up with the servo horn. Top hole is preferred as it will give the most amount of travel. If it turns out your servo arm is too low to reach the rod you can either space the mount up by epoxying a piece of wood underneath (in well over 500 custom builds I’ve never had to resort to that), if it’s a V hull you have the option to mount it higher up the V and bend the rod to the side slightly.
On something like a hydro with a low transom, or some cats, its more likely to be just right or the arm may even be lower the top of the horn. The second hole down is usually enough to give enough travel, but you can always bend the rod up for extra.
Stand up servo mounts
This style will allow for dual servo rods, which means 1 rod either side of the rudder for push pull motion. Its also best suited to larger V hulls over 40” with a high transom/deep V.
Positioning remains the same as before, feed the rod through the transom and find a suitable spot to mount the servo.
Simple trick to avoid bending a servo rod for height.
This style servo joiner can be used on the servo or rudder, or both. It can be mounted on top or underneath the rudder horn giving you a large amount to height adjustment without ever bending the rod. Before you drill the hole in the transom, do some measurements once you know how high the servo will sit inside the hull.
Don’t forget the joiner can also be mounted top or bottom for when using a stand up mount as well!