Originally Posted by rslifkin
Exactly what I'm afraid of and trying to find out. From my searching around online, I haven't found a single mention of a boat with reverse Ackerman on the rudders. So it's definitely uncommon at the least. My hope is that someone else has seen it somewhere and might have a "it might be done for this reason".
Realistically, there's only 1 steering quirk I can think of that might be related. At higher displacement speeds (6 - 8 kts) going hard over on the rudders produces a good, tight turn, but one heck of a nasty shudder in the boat. I've always assumed it's prop cavitation and disturbed water flow from the stern moving sideways too quickly, but I wonder if it could actually be a water flow issue around the rudders. This only shows up at certain speeds, it's no problem at idle, and once you're a bit above hull speed you don't get as much of a stern sliding sideways effect in a turn, so it's all good and smooth.
So full disclosure, I was not familiar with the term "Ackerman". Spending a little time time on ChatGPT I now understand the theory and why it's important in cars. I asked a few follow-up questions relating to dual rudder boats. This was the latest reply:
The dual rudder system used in boats is typically not designed using the Ackerman geometry like in land vehicles. While the principles of the Ackerman geometry are based on the fact that the inside and outside wheels of a vehicle need to turn at different angles during a turn, this is not necessarily the case in boats with twin rudders.
The dual rudder system in boats is designed to improve handling and control, particularly at high speeds or in rough seas, by providing better stability and control. The two rudders can work independently or together to provide more precise control over the boat's heading and direction, but the design of the system is typically not based on the Ackerman geometry used in land vehicles.
That being said, some boats with twin rudders may have steering systems that incorporate some principles of the Ackerman geometry, but this is not a common design approach for dual rudder boats. Instead, the design of the steering system in twin rudder boats is typically customized to the specific requirements of the boat and its intended use, based on factors such as the size and weight of the boat, the type of water it will operate in, and the desired level of maneuverability and control.