Stopring and rack and pinion geometry
The Jefa rack and pinion system should always be delivered with the stopring. The stopring will prevent the output lever from going over the dead point. If this happens, the yacht will not be able to steer any more with all due consequences. The stopring will prevent the steering pedestal from damage, but when no rudder stops are fitted, all forces will have to go through the draglink and in the event of a collision, the draglink could get damaged. Fitting rudder stops in combination with the stop plate will protect both the pedestal and the rudder.
As the output lever and the tiller lever are not pointing 90° starboard or port when the rudder is midships it is important to understand about the offset angles used with the rack and pinion system. The rack and pinion systems uses a principal known as “wide angle geometry” which gives very direct steering near midships and an increasing mechanical advantage (reduction) as the rudder approaches full travel. This results in the most direct, positive system available to a helmsman.
To accomplish this effect the pedestal output lever is shorter than the tiller lever in a ratio of 1.54:1. At midships therefore the tiller arm and output lever are not pointing 90 degrees sideways, but instead are angled slightly forward. This offset angle is known as B° and varies dependent on the distance between the pedestal and the rudderstock. The shorter the distance the greater the offset angle B.
To ease the installation and set-up of the levers, the keyway in the tiller lever will be machined in the correct offset angle. Please be aware that the keyway in the rudder shaft should always point 90° starboard or port.
The stopring can be rotated to achieve the correct offset angle. To ease the installation we have machined a degree scale on the stopring that should be referenced to the mounting bolt. The machined arrow should point to the bow of the ship. (On special installations with the rudderstock in front of the pedestal the arrow will point aft.)
The Jefa stopring is fitted with large diameter delrin blocks to prevent any damage to the output lever and to soften the stop forces.