I thought I was supposed to talk a little about rudder failure at the recent SSS Emergency Rudder meeting, so did some research. I thought I'd share some of the things/ideas on the website.
Different rudders;different problems. Not all rudders are created equal in design, in construction, in durability. If possible it's a good idea to find out how your rudder was designed and built. Most rudders consist of a stock, webbing, fiberglass surface, and foam filling. This is especially true of older rudders.
In almost all rudders the stock is tubular metal, stainless steel, aluminum, possible bronze. Above the rudder the stock extends up into cockpit. On tiller boats the tiller is attached to the top of the post. On wheel boats there is usually a quadrant below deck, but the rudder stock extends up into the cockpit so an emergency tiller can be attached. There is some type of packing gland below the quadrant to keep water out.
The section of the rudder stock that extends down into the rudder can be of different lengths. Some extend to the bottom of the rudder, other spart way down. Many tubular rudder stocks are flattened at some point inside the rudder so that metal webbing can be attached, providing lateral strength. It's possible that some older rudders might have an extension welded on to provide the flattened surface for the webbing. The webbing is almost always the same material as the rudder stock itself - or should be!
The two fiberglass halves that form the rudder are attached to the webbing in various ways, sometimes just by pressure. After the rudder halves are joined, the cavity is filled with foam. Some foam absorbs water; some does not. Older foams are often the absorbable type; newer rudders nonabsordbable. But "non" is not "never." Whichever, it salt water finds its way in. . . .
Sea water should be kept out of the rudder's interior. In practice, it often isn't. Salt water + metal + lack of oxygen = battery. As the old song goes, "something's gotta give." Sometimes it's the welds breaking off the rudder post, creating a free-swinging piece of junk. Other times it's the rudder post itself, at the point of entrance into the rudder or further down.
If your rudder drips when you haul your boat, it's probably time for some serious inspection. Just for fun, catch some of the water and see if it's rusty looking. Attempting to seal things up probably isn't enough in the long haul and will just make the problem worse since the interior is already saturated with salt water.
Another common failure, like Max's, occurs where the round stock has been flattened. The flatten section can flex more than the round section. After a few tens of thousand flexes the stock fails near the point where it's been flattened. If there's a weld involved that's a weak point, too. Both flattening and welding can create weak spots, change the molecular structure of the original material. The resulting break often results in the rudder "folding" up or sideways, sometime jamming against the hull and locking up in some ungodly angle.
This makes emergency steering very, very difficult which is why boats with simple tiller steering carry a dowl to drive the entire rudder out of the boat. Boats with wheel steering, quadrants, seals on the rudder shaft present a more difficult solution, but one that should be thought out ahead of time. If you drive the post out, how will you seal the resulting hole? The stern rising and falling creates immense pressure, driving water up.
If the rudder stock only extends part way down into the rudder, the whole bottom section can simply snap off. But at least you've got what's left and that might be enough to get home on.
An examination of the metal surface just above where the stock enters the rudder might show pitting. It's difficult to assess how deep such pitting might be and since most rudders are tubes, the tube wall can be weakened, resulting in a break just above the rudder itself. Or another "bent rudder" if part of the stock has withstood the corrosion better and hangs in there.
The boat builders/repair folks I consulted with suggested anyone contemplating a long ocean trip drop their rudder and spend some careful time assessing, even going so far as to open inspection ports, digging out the foam and looking at things. It's pretty easy to re-foam and patch the holes. If you dig out a handful of gloppy foam, if you detect rust, if you see corrosion it's time for a new rudder or serious re-build.
Carbon fiber and other exotic materials used in rudder post/rudder construction is a whole other world and I didn't get into that world.
Bottom line is careful inspection, knowledgeable help, the willingness to spend the bucks.
Pat B.
Different rudders;different problems. Not all rudders are created equal in design, in construction, in durability. If possible it's a good idea to find out how your rudder was designed and built. Most rudders consist of a stock, webbing, fiberglass surface, and foam filling. This is especially true of older rudders.
In almost all rudders the stock is tubular metal, stainless steel, aluminum, possible bronze. Above the rudder the stock extends up into cockpit. On tiller boats the tiller is attached to the top of the post. On wheel boats there is usually a quadrant below deck, but the rudder stock extends up into the cockpit so an emergency tiller can be attached. There is some type of packing gland below the quadrant to keep water out.
The section of the rudder stock that extends down into the rudder can be of different lengths. Some extend to the bottom of the rudder, other spart way down. Many tubular rudder stocks are flattened at some point inside the rudder so that metal webbing can be attached, providing lateral strength. It's possible that some older rudders might have an extension welded on to provide the flattened surface for the webbing. The webbing is almost always the same material as the rudder stock itself - or should be!
The two fiberglass halves that form the rudder are attached to the webbing in various ways, sometimes just by pressure. After the rudder halves are joined, the cavity is filled with foam. Some foam absorbs water; some does not. Older foams are often the absorbable type; newer rudders nonabsordbable. But "non" is not "never." Whichever, it salt water finds its way in. . . .
Sea water should be kept out of the rudder's interior. In practice, it often isn't. Salt water + metal + lack of oxygen = battery. As the old song goes, "something's gotta give." Sometimes it's the welds breaking off the rudder post, creating a free-swinging piece of junk. Other times it's the rudder post itself, at the point of entrance into the rudder or further down.
If your rudder drips when you haul your boat, it's probably time for some serious inspection. Just for fun, catch some of the water and see if it's rusty looking. Attempting to seal things up probably isn't enough in the long haul and will just make the problem worse since the interior is already saturated with salt water.
Another common failure, like Max's, occurs where the round stock has been flattened. The flatten section can flex more than the round section. After a few tens of thousand flexes the stock fails near the point where it's been flattened. If there's a weld involved that's a weak point, too. Both flattening and welding can create weak spots, change the molecular structure of the original material. The resulting break often results in the rudder "folding" up or sideways, sometime jamming against the hull and locking up in some ungodly angle.
This makes emergency steering very, very difficult which is why boats with simple tiller steering carry a dowl to drive the entire rudder out of the boat. Boats with wheel steering, quadrants, seals on the rudder shaft present a more difficult solution, but one that should be thought out ahead of time. If you drive the post out, how will you seal the resulting hole? The stern rising and falling creates immense pressure, driving water up.
If the rudder stock only extends part way down into the rudder, the whole bottom section can simply snap off. But at least you've got what's left and that might be enough to get home on.
An examination of the metal surface just above where the stock enters the rudder might show pitting. It's difficult to assess how deep such pitting might be and since most rudders are tubes, the tube wall can be weakened, resulting in a break just above the rudder itself. Or another "bent rudder" if part of the stock has withstood the corrosion better and hangs in there.
The boat builders/repair folks I consulted with suggested anyone contemplating a long ocean trip drop their rudder and spend some careful time assessing, even going so far as to open inspection ports, digging out the foam and looking at things. It's pretty easy to re-foam and patch the holes. If you dig out a handful of gloppy foam, if you detect rust, if you see corrosion it's time for a new rudder or serious re-build.
Carbon fiber and other exotic materials used in rudder post/rudder construction is a whole other world and I didn't get into that world.
Bottom line is careful inspection, knowledgeable help, the willingness to spend the bucks.
Pat B.