Articulating rudder 101

I need a lesson on articulating rudders! I saw a boat for sale where the owner claims he spent 7k on it and it works better then a stern thruster?? Can y'all elaborate on this? I'm trying to learn. Never really knew what the pros or cons where on this, for in all my boating years, I never really even knew what one really was!

Articulating rudders, if done right and the exisitng setup allows it, have a large following. Since the current owner claims it works so well, ask for a demonstration at both low and high speeds prior to sea trial. I've heard where low speed results are good but vibration can creep in at cruise speeds. if install/design not done right. Also ask the owner if he has traveled in following seas - this has created some AR issues with resultant AP wandering.

BTW, stern thrusters costs are a lot less than bow thrusters and for many vessels less than $7K

A couple of Mainship owners have installed articulated rudders on their boats according to reports on the Yahoo forum. Mainships being a somewhat high speed trawler have small rudders and at low speeds their performance is awful.

They liked them a lot. The cost of $7,000 is in the ballpark. OTOH a stern thruster would do everything an articulated rudder will do and more.

David

Mako,
What kind of boat do you have? How many degrees does your rudder deflect? On some boats they just need to be rigged to swing more. 35 degrees is supposed to be the maximum according to some rule of thumb but my rudder swings 45 each way and works so well I wouldn't spend $300 on an articulating rudder.
march,
Faster boats like a Mainship 30 I'm sure wouldn't benefit from over 35 degrees but slower boats w big rudders would. Judging from my own experience.

You can added an extension on the actuator to make the rudder swing a larger degree. Also a fish shaped rudder will improve the performance, and that just Epoxy that most yards can do. I do not know what the Eagle rudder angle is, but can almost push the stern side ways with very little forward motion.

I do not have a trawler yet. Just doing my homework, LOL... Just never heard of an "articulating rudder" and wanted to hear about what is, how it works, and if it is desirable or not. The boat that I will have end up being a single screw 7-8 knot cruise boat.

Or you can redrill your rudder arm/steering ram hole closer to the rudder shaft. This would be all but FREE! K.I.S.S.

1976mako20 said:

wanted to hear about what is, how it works, and if it is desirable or not.

Click to expand...

You are familiar with the tail of an airplane, right? Now imagine if the entire vertical portion pivoted like your boat's rudder AND the portion that normally pivots on the airplane is still articulated and it turns as well when the main part does, giving a little more directional influence. Or even simpler stand up, arms at your sides, bend one at the elbow so that your hand is extended in front of you thumb up. Now pretend your arm is your rudder and your elbow is its pivot point. Rotate it as your rudder would keeping your hand inline with the rest of your arm. Now do the same thing but while rotating your arm/rudder pivot your hand at the wrist in the same direction. Your hand is the articulated portion.

Worked on a few boats with Flap Foil Rudders, both single and double rudder installations.
They were pretty impressive

Here is a good animation on how an articulated rudder works

http://www.rudderpower.com/html/rudderaction.html

There was a story about these rudders a few years ago in Passage Maker.

Argh...moving parts under water.

I have an articulating rudder on my boat from Bayview Engineering - http://bayviewengineeringind.com/Rudders.html. When I ordered my boat it was my intention to install this rudder as soon as possible so I had the boats steering system upgraded to bigger helm pumps and a bigger steering ram. My observation is that the rudder works as advertised. Coming into a dock for a side landing I just turn the rudder hard over away from the dock and give it a short burst of power and the stern moves right against the dock. Sometimes that alarms the people watching on the dock but most of the power moves the boat sideways rather than ahead.

When the anchor comes up with 20 lbs of mud we lower the anchor back into the water and I put the helm hard over and go in a circle that has a diameter of about the boats length. Around around we go until the anchor is clean and I never come close to my neighboring boats. The boat really does turn in a tight circle.

The one problem I have is that the rudder makes it hard for the autopilot to keep a straight course with a following sea. With a big following sea, we have to hand steer but I think most boats would have the same problem.

Would I do it again? I don't think so given the problem with the autopilot. I believe I would go for a stern thruster rather than an articulating rudder and have the same capability but than again, there is nothing to break on the rudder.

Ron

I am considering a new build, 45 ft. SD trawler.

Coming from a twin engine background, I like the idea of these and watched some videos on YouTube, in particular two Noric 37's, one with, one without, and the turning radius of the Art. Boat was amazing.

Are others also finding issues with the boat maintaining a steady course, especially while using auto pilot?

But use would involve Pacific Ocean, mostly SoCal, coastal runs.

We have a big rudder and if those interested in articulated rudders just increased the size of their existing rudder there probably wouldn't a need for a trick rudder. And for slow only boats increasing the rudder swing to 45 degrees each way does wonders. And I'm quite sure the autopilot would have better performance not worse.

Eric, size certainly helps, but Just making the rudder bigger doesn't necessarily to the same thing as using an articulating rudder. I'm just sad that Ron couldn't have many more years to inform us of how well his worked for him.

Dave,
Yes. Dead slow maneuvering is greatly enhanced w articulated rudders. They are very effective when the boat is going very slow.
But if your rudder is big enough maneuvering at slow speeds w high deflection angles is excellent. I sure don't need more rudder performance.
It's a matter of gains and losses. What's to be gained and lost?
And I for one don't believe there is negligible drag increase from the trick rudders. The "Y" or Shilling rudder especially. The propwash encounters the flanged trailing edge of the rudder just behind the prop where the velocity of seawater is very high. Imagine holding onto a rudder stuck in the water just behind the prop of an outdrive. Of course you couldn't hold onto it unless it would fit in your hand. Maybe not even then. There's got to be serious drag .. IMO. And this drag is holding one's boat back all the time it's in fwd gear. And significantly at cruise power setting or more.

EDIT,
The rudder in Ron's link is fully articulated and not subject to the drag experienced by the Y or Shilling rudder. The only real loss from this type is the cost. I'm sure it has a bit more drag but not a significant loss.
The problem w auto pilot is something I won't experience as we have no AP. I'd take one free but .....

How much effect does the articulating rudder have on backing?

Ships and commercial boats that need more maneuverability use a articulating rudder. I've seen boats with so much side thrust, they could turn around in their own length. I built 2 rudders about 30 years ago for a fishing company's seiners. They were happy. I also modified an existing steel rudder to the design. About the last third of the rudder pivots about 15° or more. It puts a lot of force mostly sideways. I don't think just adding 10° more swing to a standard rudder would have as much effect. I think you could build a stainless one for a lot less than $7G.

Youtube video of a commercial boat: