Rudder and bearings

The rudder is a foil-shaped blade turned by a metal or composite rudder stock. The stock passes through upper and lower bearings or bushings and often a rudder tube. Some systems use roller bearings; others plain composite bushings. A rudder-post stuffing box or lip seal limits water ingress where applicable. Internal webs tie the stock to the blade skins. A spade rudder is supported only by its stock; a skeg-hung rudder also has support from a skeg.

The steering quadrant and autopilot tiller arm clamp to the stock but belong to steering/autopilot. Moisture inside a foam-cored blade can corrode metal welds, freeze in cold climates or indicate skin damage; moisture alone does not prove imminent failure.

A stock fracture, internal web failure or lost lower bearing can remove steering. A swollen bearing can jam; a loose bearing creates increasing impact loads. Water entering around the rudder tube can flood the boat. Emergency steering is difficult if the blade is gone or jammed, so a sound rudder deserves close inspection before a long passage.

Service seals and lubricate only where the bearing maker permits. Plain bearings may be machined/replaced; alignment of upper and lower supports is critical. Local skin cracks are opened, dried as required and laminated. Drilling drain holes can diagnose water but is not itself a structural repair.

Dropping the rudder allows stock straightness/corrosion, bearing surfaces and blade entry to be examined. Rebuild a blade when skins/core/webs are repairable. Replace the complete rudder when stock or internal structure is badly corroded, bent or cracked, or when repair engineering approaches custom replacement cost. Ensure emergency-tiller and autopilot interfaces match after work.

• Covered by a standard survey — blade tapping, moisture readings, cracks, impact, stock where visible, bearing play, smooth travel and rudder-tube leakage. The surveyor cannot see internal webs through intact skins.
• Not covered — dropping the rudder, stock dye/ultrasonic testing, bearing disassembly and internal imaging/coring. A focused specialist review costs roughly $500–$2,000 before yard work. Do it pre-purchase for major play, cracking at the stock entry, rusty weeping, impact, stiffness or a known model failure; otherwise schedule a condition check after purchase.

• The broker or owner — “Send invoices/photos for rudder, stock, bearing, seal and grounding/collision work.” “Has the blade ever drained water, shown rusty weeping, jammed or developed play?” “Identify bearing/rudder manufacturer and stock material if documented.”
• The surveyor — “Measure movement at the trailing edge and distinguish bearing play from steering play; map blade moisture/percussion; inspect stock entry, tube, upper support and quadrant attachment; and state whether evidence justifies dropping the rudder.”

With the boat hauled, grip the trailing edge and move it sideways and fore-aft while someone watches the stock/bearings. Turn through the full range with steering and pilot disconnected if allowed. Look for a crack halo around the stock entry, asymmetric fairing, rusty drips, weeping after haul-out and impact at the lower tip. Inside, check the upper bearing/support for flex and the rudder tube for salt trails. Steering stiffness that changes with stock position is important.