RUDDER DAMAGE: KEY POINTS
There are five main ways that a rudder can break and cause a boat to lose steerage.
1. Rudder stock failure: The rudder stock sometimes fails when bending stress in the stock exceeds the strength of the material. With a spade rudder, this usually occurs just below the lower rudder bearing, at the point of maximum bending load.
2. Rudder blade detaches from the stock: The blade can detach from the stock as a result of sudden impact, delamination or welds corroding through. Rudders are often built by welding some pieces of stainless steel perpendicular to the rudder stock. Foam is then laminated on either side of these “tangs” and fiberglassed over. With time, stagnant water in the rudder can cause the stainless-steel welds between the tangs and the stock to fail.
3. Bearing/bushing failure: Bearings can break down over time, especially in steel bearing systems when seals fail and saltwater gets into the bearing pack. Delrin or other plastic-type bushings can also break down over time through material degradation or undue friction. If a bearing/bushing fails, the rudder can seize completely and/or tilt and bind, depending on your course and angle of sail.
4. Rudder binding: Rudder blade binding is typically caused by fish nets or lines that become wedged between the rudder blade and the hull.
5. Hull deformation or cracking: In some rare cases, rudder failure may be caused by hull deformation or material failure around the rudder bearing mounts. While the least common failure mechanism, it is also the most difficult to repair.
Of course, the best emergency rudder system is the one you never use. So, given these failure mechanisms there are a few things to check to make sure the rudder is in good operational order. These include looking for:
• Pitting, cracks or corrosion of the rudder shaft at joints and especially where it enters and exits the hull
• Moisture in the rudder blade material: use a contact moisture meter or drill a small hole in the rudder blade and check for water
• Cracks or crazing on the surface of the rudder blade, which could suggest hidden flexing of the rudder post
• Any damage in the bearings or gudgeons, including the pintles at the foot of a non-loadbearing skeg
• Cracks or deformation of the hull around the rudder, including cracks in the bottom paint or gelcoat, since these could be a sign of more severe problems
• Movement or deflection of the blade, shaft or bearings when the rudder is pushed in any or all directions