Newsletter Fall 2009
Articulating Rudders---by Hugh Hazeltine
Our boat is Hull #12 or 3rd in the line of Great Harbor GH37s. Before I ever piloted the vessel, I thought a twin screw 37’ boat would be a breeze. Well a breeze is all it takes to make it interesting. Weighing in at 44,000 lbs, a bow that is off the water, and a cabin top that is 14’ and having no keel to preserve her shallow draft, a little wind on the beam and a GH37 will move sideways quite easily. We loved the boat but controlling it at low speeds in windy conditions was a challenge from the start. The original Wesmar dual prop bow thruster was not up to the task. We replaced that with a Vestus 95 single prop that fixed the bow thruster issue.
The early Great Harbours were built with rudders fashioned from a ˝€ť” thick steel plate, and were rectangular. Simple to build but not very sophisticated. It was my experience that the rudders would stall beyond 25 degrees of deflection. Stalling is where the flow of water over the rudder becomes turbulent and no longer provides lift in the desired direction but now merely drag. The consequences of this is that too much redder deflection can have a negative effect. After 25 degrees you can have less turning power instead of more. This is called control reversal. At Hull #34 (Lo Que Se A) Mirage installed a new kind of rudder. It was airfoil shaped. Two GH37’s traveled together, one with the old and one with the new. The new rudder boat could turn in half the radius (idle power and calm wind) of the old. I wanted one of these new rudders but ran into a communication problem at Mirage. I went looking for another solution. I had seen articles about articulating rudders. But where to find one sized for our boat?
I found Deflector Marine in Washington State. I talked to Lowell Stambaugh on several occasions over several months. Each time I had a thorny question, Lowell had an answer. We have a much greater percentage ahead of the pivot point than behind now. Thats because the aft part is so much more powerful, Lowell said.
He told me that boat builders have a whole boat to design and build. They don't have the time to dedicate to rudder design that he has.
Take a look at the articulating rudders and notice the hinge of the trailing flap. It has an ultra-hi molecular weight plastic hinge pin. It won't rust. The mating of the two pieces has no open spaces. none for the barnacles or other growth to set up house in. The rudders are made of stainless steel. The installation was done at Embree marine in St. Petersburg, Fl. Since we had the rudder shoes off we pulled the shafts and renewed the cutlass bearings. One of our strong dripless shaft seals had failed and we replaced both with Buck Algonquin traditional stuffing boxes with GFO stuffing. Blue skies rudder shoes are U shaped. The cavity of the U collects barnacles, paint chips, and water during haul outs. So we had the channel filled in with fiberglass board. No more well of goo.
So how does it work? I am very satisfied. It has taken some time to adjust to how powerful the rudders are. With the rudders hard over, you can look back and see the prop wash exciting the stern at a 50-degree angle. Sometimes while maneuvering, I want to turn and move ahead little. If I have the rudders too far displaced, all I get is a turn and no movement ahead.
A powerful rudder can have value at other times. We were in waves 20 degrees off the bow. We had to slow to 4 kts so the bow would follow over the top of the wave and not get any air under it and pound. With the old rudders there were times when the Robinson autopilot could not keep up and we would fall off our desired heading. The new rudders will provide more turning power with less displacement and give the autopilot a chance in those situations.
Another time, we were approaching the Englewood Bridge at 4 kts with the articulating rudders. Sharissa shouted she couldn't get the pin out to lower the mast. We were just about to come between the dolphins leading to the bridge. (I know why did we wait so long?) I brought the helm hard over and the boat did a beautiful 180-degree turn. Otherwise I would have had to use reverse to stop the boat and that would have been hard on the engine mounts at that speed.
The delivered price of the rudders was $6600 plus $1000 of installation costs. I understand the Mirage rudders can be had for much less. So was it worth [it]? It is something we use every time we move the boat. What value can you put on being able to maneuver your boat with confidence?
(Editorâ€s note: Hugh is a pilot, and an instructor with Delta Airlines)