FIRST CASTING IS A FAILURE

But boy did I learn a lot! Below is an unedited description of the learning process!

Casting A Rudder Heel Bearing: The difference between failure and success
Well, it turns out that the rudder heel bearing cast was a little more difficult than I grasped. My first casting was a failure - as far as the casting itself was concerned - but what an incredible educational opportunity. I had been trying for years to engage my brain to learn about casting, but just could get no traction because I am an experiential learner. Once I got my hands dirty, learning went into superdrive. Everything made sense.
So consider the rudder heal bearing anatomy - a slanted back wall and a slanted "socket" for the rudder post to sit in. Now consider the mold half with the plug for the socket, as well as the back wall. There is only one direction that the pattern will lift out after that half of the mold is formed - and then only if the back wall of the pattern and the socket walls are parallel. You could, however, lift the template and break the plug off, and then reglue the plug.
The reason the first casting failed was my lack of understanding, a lack of how molten metal behaves as it solidifies. Molten metal solidifies from the outside in. The walls of the mold absorb heat from the metal closest to them, and as the heat is absorbed the metal solidifies, with the interior isolated pockets remaining molten the longest. This fact leads to a fundamental visualization model of THE PATH OF SOLIDIFICATION, which includes not only space but time as well. A successful casting starts with a pattern whose design has incorporated the consequences of THE PATH OF SOLIDIFICATION.
The failure of my first attempt at casting the rudder heel bearing is a perfect example of making a pattern that did not consider the PATH OF SOLIDIFICATION. Consider the shape of the original heal bearing. The aft portion has some relatively sophisticated curves that appeared to be a lot of work, so I just simplfied the pattern to have thicker walls and no pattern, reasoning that it would be less work, and stronger as well. WRONG! It turns out the those thick walls created a massive, isolated pocket of molten melt that solidified very slowly - well after the rest of the bearing had solidified and was CONTRACTING. The stress put on the molting internal pool created what is known as a "hot tear", somewhat a akin to a fissure in a glacier, right in the bottom of the socket. So those curves on the back of the original mold were not for looks. They were to keep all the walls close to the same thickness, which would allow uniform cooling with no late cooling pocket of molten metal.
It also did not help that at the bottom of the socket two wall meet. That focuses the stress from both walls, making the junction a likely place for a failure. So radiusing all intersecting walls is another fundamental rule of pattern making. And I did add a radius of JB Weld in the second pattern.
One last mistake I made, as another consequence "of over designing" the pattern, was that I did not have enough bronze to complete the pour. Sort of ended up with a 9/10 height bearing on the first try. That was ok, but there was another consequence. Even the original heel bearing had walls that were thicker in some places than than others. To deal with this situation, one makes sure that that PATH OF SOLIDIFICATION never blocks off the path of incoming molten metal to these isolated pockets. Then even as the rest of the solidifiying metal contracts, more molten metal is coming into the area. When the whole mold is full you should still have a "reservoir" in the spru cup that feeds the space created by the contraction of solidification. Since I did not have enough metal, there was no reservoir.
If you want to get into casting I highly recommend the U. S. Navy Foundry Manual.