Rudder assembly

[mrmal56]

Need some help with the rudder assembly.
Bought a Saltare and am restoring it.
The usual stuff, stringers, floor, engine rebuild, upholstery.
Have never owned an inboard before so I'm not familiar with the drive systems and steering.
A couple things:
The rudder can slide up and down about an 1.5". Is this normal or am I missing some seals, spacers, packing etc. ??
Second thing, the rudder does not line up with the propeller shaft, is this normal or do I have an alignment problem. Seems to be offset about 1".??'

Any comments would be appreciated.

[OUI]

The offset rudder is normal. It allows the shaft to be removed without removing the rudder. The up and down movement is not normal. The packing nut could be loose or it could need new packing material.

[DKJBama92Mariah]

Mr. Mal,

I posted on the rudder play subject in another thread ( http://www.supraboats.com/bb/viewtopic.php?t=1915 ), but i'll paste it into this post since it's actually more on topic here.

Inboard rudders are offset for two reasons:
1) So you can pull the driveshaft without removing the rudder; and
2) The offset may work to counteract prop torque (this one is pure speculation on my part, but it seems logical.

As far as the rudder slop is concerned: There will always be a little left-right slop due to the way the steering cable is mounted. The up-down slop is troubling though.

The "tiller arm" is the arm which fits over the rudder shaft on the inside of the boat and connects the rudder to the steering cable. This allows the back-forth motion of of the steering cable to be translated into a twisting motion that turns the rudder.

The tiller arm serves a second purpose though. It keeps the rudder in the boat. The arm is on the rudder shaft and it typically rests against the packing nut on the rudder box. holding the rudder up and keeping it from just falling out of the hole in the rudder box.

Lemme simplify:
1) rudder shaft goes through the hole in the rudder box
2) the rudder should be pushed all the way up where the rudder is flush with the bottom of the boat
3)Inside the boat, the tiller arm slides over the rudder shaft coming up through the hole
4)With the rudder as far "up" as it will go, the tiller arm gets slid down the rudder shaft as far down as it can go...when the tiller arm is resting on the big nut on the rudder box.
5) The tiller arm gets locked into place where it is.

This should result in a minimal amount of up/down play for the rudder.

What you are describing with the up/down slop indicates that the tiller arm has slipped upwards on the rudder shaft allowing the rudder to drop down to where it is not flush with the bottom of the boat. The slop you find is most likely caused by this.

Does it really matter?
Yes, for two reasons.
1) If there is slop, it means the tiller has moved at least some on the shaft. If it can go this far, it could possibly slide all the way off over time, leaving your rudder at the bottom of the river and a nice 1" hole in the bottom of your boat that is fairly inaccessible to try and plug the leak. This scenario is pretty unlikely though.

2) When the rudder turns, half of the props thrust is being diverted by the rudder which causes the boat to turn in the desired direction. At high turn angles and high throttle, the amount of force exerted on the rudder and shaft is substantial. Think of the rudder as a lever with its fulcrum located where the rudder exits the boat. The longer the lever, the greater the mechanical advantage

Let me give an example to clarify. Say you clamp two pieces of steel pipe in a vice. One pipe is 2ft long and the other is 5 feet long. Grabbing the end of the 2ft pipe and pulling on it to bend it would be very difficult. Grabbing the end of the 5 ft pipe, you have 2.5x the leverage/mechanical advantage and could probably bend the pipe pretty easily.

Now apply the example to the rudder situation. If the rudder is hanging 1" lower than it should, that makes the "lever" longer. The force exerted on the rudder itself by the prop is the same, but because of the longer lever and the mechanical advantage it gives, the force exerted at the fulcrum (where the rudder shaft exits the boat) is greater.


DOES ALL OF THIS REALLY MATTER? Yes

After all, the rudder is strong and it can't be THAT much force? Yes it can be.

Be mindful, although your prop is NiBRAl(Nickel, bronze, and aluminum alloy), the other underwater gear (strut, fins, and rudder) is typically not because the expense of the nibral alloys. These parts are most likely a more common bronze alloy (an alloy of copper and tin). The difference between the two is in how brittle they are. Bronze is much more brittle than Nibral or steel. Bronze will typically break before it bends while steel is just the opposite.

Bottom line, if your rudder moves up and down, you need to check the tiller arm. If you ignore it, it won't just go away will likely rear its ugly head at the least opportune time.

The consequences of just ignoring this have the potential to suck really bad. First, if the tiller arm comes off and the rudder falls out, you could be swimming home to call a salvage company to pull your boat off the bottom of the lake. Second, if the rudder shaft breaks due to the increased loads, you'll be limping home at idle using only a boat paddle to steer. (You do carry a paddle dontcha? Smile

In either of the above situation, you would be faced with replacing the rudder. I've done it and IT IS NOT FUN, but thats a story for a whole nother thread.

DKJ

Edit: 1/4" or so of up/down play in it probably won't make a huge difference; just keep an eye on it and make sure it doesn't get any worse over time. However, any more than 1/2" and I'd say you need to get the boat looked at pronto.

Also, let us know what precise types of slop you are experiencing. I'll classify them into 4 types of movement:

1) Fore/aft rocking - while gripping the bottom of the rudder, you can make it rock or wobble frontwards and backwards.

2) Side-to-Side rocking - while gripping the bottom of the rudder you can make it rock or wobble left and right.

3)Rudder slides up and down through the hole on the stuffing box.

4)Steering slop - you can turn the rudder left and right by hand without the steering wheel turning.

Diagnoses and solutions:

1 and 2) Stuffing box and/or rudder shaft worn - replace both

3) Tiller arm has slid up on the rudder shaft - discussed above; reseat the tiller arm and make sure it is properly secured

4) Wear in the steering components near the rudder. Two components:
a) there is a ball joint that connects the end of the steering cable (shiny part) to the tiller arm; this could be worn out.
b)There is a metal plate on the inside of the boat in the center aft of the transmission, driveshaft and stuffing box. This plate shares bolts with the driveshaft strut which is directly below it. The end of the steering cable SLEEVE (the black part) has sort of a ball joint that bolts to this metal plate. It is a single bolt that fastens this and it is notorious for loosening up and causing steering slop. I check mine yearly. Also recommend loctite and a split locking washer.