The main rudder was seeming suspicious, and I was unsure of its condition, so had it removed. In the picture, the rudder shaft is being heated to force it to expand and break free of the bearing it is seized into, so the rudder can be removed.

The main rudder was built of aluminum over a plywood core (see picture in next entry). Aluminum and steel don't tend to work so well underwater on the same boat (different metals cause electrical currents to flow between them, causing one of the metals to corrode), and the combination is generally avoided.