I have done this twice while I owned Obelix. I can give you a few pointers.
Here is the process:
First anchor securely in shallow water, probably not less than 10 feet, since the rudder and post must
come down to clear the boat, but also not too deep, as you may drop the rudder and will need to retrieve
it. You can measure the rudder length from the bottom of the boat, then inside from the hull to the
top of the rudder post, plus a couple of inches for the hull thickness. This is how deep you need to be
to get the rudder and post to clear the bottom of the boat.
Then carefully tie a line to the rudder, it is heavy and will sink when free, it does not float. Note that
the rudder shape is not easy to tie to, be careful.
Next, disconnect the steering yoke bar that runs between the rudders. If you have an autopilot position
sensor on the rudder, disconnect it. Disconnect and remove the yoke arm from the top of the rudder post.
The rudder should now be free of connections to the boat, and if you are lucky, will want to slide down
and free. Prevent this with ropes until you can dive into the water to retrieve it.
If the rudder does not want to slide down and out of the boat, you may have a bent rudder post. In this case,
you can push down on the post from inside the boat, levering against the bottom of the step immediately
above it. I used a small hydraulic jack, but you can probably get by with a 2x4 as a lever. Be sure to protect
the bottom of the step with a board so you do not damage it. If the helm turns freely, your post is probably
not bent. You can also dive on the rudder and check the clearance between the top of the rudder and the
bottom of the boat. My clearance was about the diameter of my little finger.
Retrieve the rudder and post from beneath the boat and effect your repairs.
Re-insert the rudder and post from beneath the boat, which can be tricky since you will be free-diving beneath
the boat and the rudder will want to sink. Some ropes will help force the rudder back up into the boat.
Remake the connections that you undid above.
The rudder post is hollow and will fill with salt water during this process. Though it is stainless steel, this is not
really good. Use your dingy pump to empty the post of water as best you can. If you are anal about this, fill
the post again with fresh water and re-drain it.
St. Francis designed the rudders to be sacrificial. Rather than break up the fiberglass around the steering post,
the rudder post is designed to bend. Not bend easily, but more so than break up the boat's fiberglass. I have
repaired a bent post, but it is not an easy process, and hopefully you will not need to do this.
It is possible to control the boat with a single rudder if you need to. Disconnect the steering yoke bar from the
damaged rudder and leave the end free. Hopefully the damaged rudder is frozen in a straight forward-aft
I hope this helps,