Over time the amount of play in the bearings between the rudder stock and its tube will inevitably increase. Owners of tiller steered yachts will usually notice failing rudder bearings at an early stage as they will feel the movement of the rudder directly though the tiller and may even see the rudder head moving if it’s easily visible.
On wheel steered vessels, however, you’re further removed from the rudder, so wear may not be apparent until it’s more severe and the rudder can be felt knocking around in a quartering sea. For this reason, it’s worth inspecting the system at least once a season: with the boat securely chocked up ashore try moving the bottom of the rudder blade from side to side (for more detail and further maintenance ideas see my feature: 5 top winter yacht projects.) A small amount of wear, maybe around 1mm at the bearing, is acceptable, but if there’s significantly more than this further investigation will be needed.
Dropping the rudder
Removing the foil will require either a hole to be dug in the ground, or if the yard has a tarmac or concrete surface, the boat must be lifted far enough for the rudder and its shaft to be lowered out of the hull. It therefore makes sense to combine this with lifting the boat ashore and relaunching – it’s worth discussing options with the boatyard before the vessel is hauled out.
Rudderstocks, especially those of tiller-steered boats, are typically held in place with a two-part collet that sits around a recess at the top of the rudder shaft to prevent the rudder slipping downwards out of the boat. With a wheel steered boat it’s also necessary to disconnect the steering mechanism and remove the quadrant before the rudder can be lowered (take a look at How autopilots work for more detail on steering systems).
It’s vital to plan how to support the foil once the collet has been removed. Don’t underestimate the weight of the rudder with a stainless steel stock – expect it to be super heavy and rig lines underneath to take the load, remembering that most of the weight is near the front of the foil. Fortunately, if the boat needs to be lifted to remove the rudder, the boat yard will probably take care of this element of the process. On the other hand rudders with an aluminium or composite/carbon stock are surprisingly light.
Removing the rudder bearings
Once the rudder blade has been lowered the old bearings can be slid off the shaft. Yachts of less than approximately 32-36ft (9.5-11m) with a spade rudder are likely to have plain bearings – simple bushes made of a low-friction and very wear-resistant engineering plastic such as Delrin. You should find two plain bushes, each with a collar, that support the top of the stock and the bottom couple of inches of the shaft above the rudder blade. If you take accurate measurements of the rudder shaft and tube using a Vernier gauge new bushes can be turned up by almost any engineering workshop for a modest price.
Under high loads plain Delrin bushes can become hot and expand, making the bearing stick, so larger yachts tend to use needle roller bearings. In this case, a material such as Delrin is generally used for the rollers and anodised aluminium for the bearing cage. However more recent developments in plastics, such as Vesconite, can be used to produce plain bearings for larger vessels than was previously feasible.
Many yachts built over the past couple of decades have off-the-shelf bearings and rudder tubes from Jefa, the Danish manufacturer of rudders and steering systems that now dominates this market. If so, replacements should be available off the shelf. Otherwise, a new bearing unit will need to be custom made by a marine engineering workshop, which may cost a few hundred pounds and will need extremely accurate measurements. Given the costs involved, if you have to take this route it’s worth getting the engineering company to visit the boat to take measurements and check that the rudder tube has not worn into a slightly oval shape.
Skeg and keel hung rudders
These normally have a similar top bearing to a spade rudder, while the lower bearing sits in a shoe at the bottom of the skeg or keel. On many smaller and medium size boats this is a simple fitting, with a metal pin running inside the metal shoe without a bearing – the relatively small rudders of many boats of this style mean the loads can be quite small compared to those on a spade rudder. Larger boats may have a bush in the lower support – often this will have originally been made of Tufnol, however, Delrin is a good modern alternative material for this purpose.
For more information about rudder maintenance and yacht steering systems, see: 5 top winter yacht projects and How autopilots work.
This article was first published in 2014.