Self Steering

Damage to our Windvane

I awoke one morning to the worse thought. We had a rather dolly night in the marina and I was worried that our windvane might be contacting the pier behind the boat.

My fear was confirmed when I looked outside to find that the dock lines had stretched a few feet and the pendulum of the windvane was lightly but steadily contacting the pier.

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This small touch made some big problems. The pendulum was being pushed by 18 tons and that force easily bent the pendulum. I overlaid the old and replacement pendulums so you can better see the damage. See how the bracket bent?

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If I align the brackets, you can see how fiercely the strut is bent.

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The discrepancy at the bottom is most alarming. This is thick stainless steel and it bent so much!

Thankfully, all the damage was contained to the pendulum and I was able to order replacement parts from Scanmar to get our Monitor Windvane back up and running!

Monitor Wheel Adapter Unspooling

Monitor windvanes are remarkable machines. They will steer you on your course with only a whisper of wind! 

They perform this magic without question, but only ask that you balance the helm perfectly! If you do not, the force of the rudder may cause the ropes to unspool from the adapter and the whole system fails. 

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If you seem to have just a wee bit of weather helm that you can't trim away, try using a clothes pin to hold the rope on the adapter. If the rudder turns the wheel, the clothes pin will keep the rope from lifting up and coming off. 

This is not a replacement for proper sail trim, simply a crutch to get you through a time when perfect sail balance seems to elude you. 

Self Steering in Action

Our self steering system was designed and built by Scanmar. We have their Monitor Windvane mounted on our stern. The unit is known as a Servo-Pendelum system, where the wind information from the windvane is fed down to the servo-pendulum (rudder paddle in the water) to then use the force of the water passing by to power the wheel and control the boats rudder. 

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The system works very well and is powerful enough to steer us straight on a course in the worst of weather. The harder it blows, the faster you will go. The faster you move through the water, the more force the paddle has to pull on the control lines of the wheel and turn the rudder. 

While sailing in heavy weather where you are surfing down waves in excess of 8 knots may seem fun, it is in light weather that the unit really proves itself! 

We have found that it works well when we are sailing along at around 4 knots, and well enough to keep us on course all the way down to 2 knots. When we are sailing slowly, there is less wind and we don't move very fast; meaning that the paddle has less umpf to pull on the wheel, but at the same time, a well balanced boat will sail straight in these conditions regardless. 

We absolutely love our Monitor Windvane, and greatly enjoy watching the paddle snake its way through the water behind us as we manage to sail straight on our course! 

Repairing the Monitor Windvane

When the gale was approaching, we hove to and settled in to ride out the storm. Since we were not going to be sailing for the next few days, and instead simply drifting through the water sideways, I lifted the paddle out of the water on our windvane. This presented extra stress to the Monitor windvane and led to the following failure.

Had the storm been as predicted, blowing only 20-30 knots, no damage would have occurred. The storm increased in intensity and duration, building to 40-45 knots for several days. During this time, various rouge waves bypassed the slick and broke onto the boat. These waves imparted a furious amount of energy onto the boat and all of its equipment.

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The Monitor windvane was hanging out on the stern with the paddle raised high to avoid being pressured by water as we drifted laterally. The issue was these powerful breaking waves would slam into the paddle and cause incredible stress in the form of shock loads onto the equipment.

Through out the storm, only one piece of the Monitor windvane broke. Thankfully it was an easy piece to replace, but sadly it rendered the entire unit inoperable until the part was replaced.

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The head of a 1/4 inch stainless steel bolt sheared off! This caused the lower gear of the unit to rotate slightly and allowed the entire unit to come undone. While out in the storm, I was not able to look at everything closely enough to determine the problem, so I hand steered for over a day to get us back to shore. Once in the safety and tranquility of a safe harbor, I gave the unit a much closer inspection and located the problem.  

Luckily, there was a hardware store within walking distance of the boat and the replacement bolt was had for only $0.55! I used a rubber mallet to tap the gear back into alignment with the shaft and the bolt hole so that I could easily slide the new bolt through the hole.  

I then called the company because I was unsure about how the gears should interact, as in which teeth of the top and bottom gears are supposed to rest on.  You see, when the bolt sheared and the lower gear rotated slightly, it then allowed the top gear to slip out of place! When I first looked at it, the top gear was facing up and was not contacting the bottom gear at all. I noticed the small arrow on the bottom gear pointing at the first groove and figured that must be there to indicate something.

Upon speaking with the owner, that arrow points to the groove that the left most tooth of the top gear is supposed to rest in as the gears first come together. With that knowledge I was able to get the unit put back together and calibrated, giving me the ability to leave it in charge of steering us on our next ocean voyage. 

One thing that is still unclear is how the paddle should be placed during a storm. If you leave it down while hove to, it will be under intense lateral stress as you drift through the water. If you raise it up, the paddle is no longer under the same stresses, but any impact to it will be accentuated by the long lever arm it has created. The manufacturer told me that they are not yet completely certain which configuration is best for a storm which has led me to my next decision. 

If the weather is calm enough before the storm, I plan to climb out on my stern and remove the paddle from the unit. If the paddle is not there, then it doesn't matter if it is up or down! The paddle and the air blade are the two largest surfaces of the unit, and if they are removed, the remaining structure will be able to live out the storm without fear or risk of damage. 

Monitor Wind Vane Installation: Part 6, Clearing the Transom

The wind vane needs to have access to swing and move without obstruction. This means that all our clutter and gear needs to be relocated and moved away from the transom. The big things that need to go are the stern anchor, davits, and wind sensor pole. 

I cleared off the large components, but left the stern light mounted below the rail. This too had to be removed as it interfered with the counterweight movement. If the Monitor were set on a starboard tack and close reach, the lead weight would bump into the stern light and make the unit get stuck.

The stern light was not that major of a problem since the Monitor has a stern light built into the frame. The other equipment was more of an ordeal to remove and relocate. The stern anchor for instance is frequently used to position our yacht with an East/West orientation. This orientation keeps the cockpit shaded and the solar panels in full sun all day long. 

The davits on the transom were of a different use. They were a royal pain in the stern to use, so I rarely every used them for their intended purpose. I purchased them to hoist the dinghy up and bring it along as we sailed, but it was very inconvenient. The dinghy needed to be tied up well to avoid it from sloshing side to side as we heeled over. It also required a bunch of fenders to avoid damage to the lettering on the stern. This was the first and last time I ever raised the dinghy on the davits!

From then on, the davits served other purposes, like storing our spare lines or raising batteries into the boat while on the hard. 

The davits were removed and disassembled, but they will be stored in a locker. Should we find ourselves on the hard and in need of lifting many heavy items into the boat, we can always assemble and install the davits temporarily. Rope storage will be relocated to another location on the boat, possibly a lazarette organization system for the ropes. Storing the ropes inside a locker fulfills a few tasks: it keeps the ropes away from salt, it keeps the ropes out of the sun, it keeps the rope out of sight.

Salt makes the ropes stiff and harder to use when you need them. The sun eats up the ropes via UV degradation. Keeping the ropes out of sight makes the boat look neater and also reduces the risk of someone else using the rope for their projects on their boat.

The Monitor Wind Vane is the most important piece of equipment on the transom, so its mounting requirements take top priority. If anything impairs its ability to function, that thing must be removed and relocated. Storing ropes or lifting batteries is not the priority while sailing across an ocean! Keeping these priorities in line allows us to maintain the yacht in the most functional of methods and will allow us to sail in the safest method possible.