Boat Handling 101

By Capt. Mark Manes, NorCal/Lake Tahoe Chapter

Let’s just say that you have just spent all winter getting your boat ready for the season.  Countless hours of sanding, varnishing, cleaning, and painting – and your girl is now finally ready for the show. After easing her gently down the launch ramp into the water, you load up all your friends and supplies, preparing for a great weekend at another A.C.B.S. event. You carefully pull away and drive her over to the docks and look for your assigned slip, the wind begins to pick up a little and you get out of position trying to line up for your slip. Panic ensues as you soon realize that you are getting set on another club member’s boat. You hit the throttle hoping to get out of it and misjudge.  BAM! you slam into your friend’s boat, damaging both your boat and your buddy’s boat, ruining what could have been the perfect weekend.

None of us ever want that situation to play out like that, we take pride in our boats and have a great deal of time and money invested in them. After many years of handling large dinner cruise boats, crewboats, tugboats, and now ships – there have been a few bumps and scrapes along the way. My favorite saying is “Keep going till it sounds expensive, then back up a little bit!”, another one is “You know what makes a good tugboat operator? 1 million dollars in damage!”  Anyone that has messed around in boats before has had their fair share of “whoopsies”. My goal in writing this article is to try and explain some of the basic principles of boat handling to help prevent them.

“A ship can be more successfully and safely handled taking advantage of, and cooperating with, the elements to the fullest extent instead of disregarding and working against them.”

• Carlyle J. Plummer, author of Ship Handling in Narrow Channels

The most common mistake that I see people make is thinking that their boat is like a car, well it’s not.  What I mean by this is twofold; 1- A car steers from the front, while a boat steers from the stern, and 2 – A car has brakes, a boat has reverse, which can be quite unpredictable.  When you see something on your right that you are trying to avoid hitting, the immediate reaction is to turn to the left (like in a car).  Wait!!  What about the stern of your boat? BAM! you just smacked the thing you were trying to avoid (time to get out the brush).  This article will explain pivot point in great detail, take it to heart, and understand that the stern of your boat will swing in the direction opposite from your bow. When maneuvering, one must always pay attention to the stern when working around solid objects.  As far as the boat brakes go, well, we will talk about that with propeller torque below as well.  Another piece of advice is that, in general, more throttle does not make the problemed situation any better. 

I would like to discuss three fundamental principles: The Pivot Point, Propeller Torque, ,Shallow Water Effect, and Wind.

THE PIVOT POINT:
The pivot point is the spot on a boat’s fore-aft axis that it turns around on. If the boat is dead in the water, the pivot point will be on the opposite side of any force applied (wind/current). If there is wind, the vessel will rotate around that point depending on its shape and draft. In general, boats will lie beam to the wind when dead in the water and rotate back and forth in a seesaw motion around the pivot point, which shifts as the vessel gets headway or sternway. 

 

 

 

Once a vessel has headway, the pivot point will move aft to about 1/3 the distance from the bow, typically just forward of the drivers’ seat on most of our boats. Meaning that the bow of the boat will be turning in the direction you are trying to go, while the stern is going in the opposite direction around the pivot point. 

 

 

 

 

The lever arm from the pivot point to the stern of your boat is long, so the rudder has more power to turn the boat. This is why the rudder is effective only after you have headway.  Think of it like getting a piece of pipe to extend your wrench to get more leverage vs. using a tiny short-handled wrench. The longer lever arm is much easier and has more power.

I emphasize the headway aspect due to my next statement: when you have sternway, the pivot point moves all the way to the stern of the boat, directly at the rudder.  So, the rudder becomes that short-handled wrench at that point. It has a very small lever arm to work from and will not give you much effect until you gain headway. The other critical thing to note here is that when you have sternway, the entire boat length is now being acted on by the wind and current. The forces now have a much larger lever arm to work with, as the pivot point is now at the stern. That is why when you are backing up, the bow will always fall off with the wind, use that to your advantage. Have you ever noticed that when you are backing up, the rudder is not very effective unless it is very large?  Most of our boats will not steer very well when backing. They are very prone to be acted on by external forces like wind and current.  I hope that this gives some of you some insight into why your boat behaves the way it does and allows you a greater understanding of the forces involved.

PROPELLER TORQUE:
Another part of the boat handling equation is propeller torque. Most of our boats have “right-handed” propellers. This means that if you were to look at your boat from the transom and put it forward, the propeller would spin clockwise or “right.”  If you can picture that, imagine that the propeller will “walk” the stern of the boat in that direction as you put the boat forward. The rudder easily overcomes this force because, as we learned earlier, the rudder has a big lever arm when the pivot point moves forward. When we put the boat in reverse (astern), the opposite is true. The stern of the boat will now want to go to Port as the propeller “walks” in that direction due to it spinning counterclockwise. However, the wash from the propeller is now going towards the bow, away from the rudder, so it will have little to no effect. The propeller “walk” will be most strongly felt when the boat still has a little headway and you back hard because the pivot point is still forward. The propeller side torque will be less as you gain sternway because the pivot point will move to the stern. If you happen to own a boat with a “left-handed” propeller, the principle is the same, just the opposite.

So now that you know the basics or Propeller Torque, how will you apply them? Next time you are in a tight space with your boat, try leaving your hard rudder right (if you have a left-handed propeller, do the opposite). Leave the rudder there, and then simply rock your engine ahead and astern. You will find that the boat will make a very small diameter turn quite easily. Every time you go ahead, the rudder is helping that stern go to the left. Every time you go back, the propeller torque will assist you and do the same. Hence you will make a tight right turn within a narrow fairway. In an open area, try the opposite and you will see that it doesn’t work well.

Many times when maneuvering, it’s better to back and get sternway and let the wind just carry your bow around, even if it is initially not the direction you wanted to go. You get to show off more of your boat as you are spinning around in circles – which is great.

When backing, the rudder is practically useless. The boat will not follow the rudder until you have some stern way built up, and even then, it is marginal at best. This is because of the pivot point location and the propeller wash not going over the rudder.  You are better off leaving the rudder hard over the way you want the stern to go when you run ahead on the engine (unless you are going a long way astern). You can play with this concept in an open area, giving you a feel for how the rudder will react when backing.  Another thing to try is get some sternway on and then take the boat out of gear – you may find it will follow the rudder more easily.

SHALLOW WATER EFFECT

Have you ever noticed that your boat handles differently when you get into really shallow water?  Shallow water is defined as any depth that is less than 1.5x your draft.  Most of our boats draw about 2’ of water, therefore if you get into 3-4’ of water you are going to start feeling the effects. What you may notice is that your boat will become more “Directionally Stable”. Meaning, that it does not want to turn as easily and your boat’s overall turning radius will get larger.  Additionally, your boat will have a harder time stopping while carrying her way longer, and the propeller torque that we talked about earlier will be more pronounced. Displacement is the weight of the volume of water that your boat takes to float. That displaced water has to go somewhere as your boat travels through the water, it wants to fill in that created “hole” where the boat was.  Turning creates higher water pressure on the outboard side of the turn, and is usually relieved by water going under your boat or around it. When you get in shallow water, the water cannot go under the boat easily; thus, pressure builds on the outboard side of the turn, preventing the boat from turning. Furthermore, the water filling in the “hole” will want to rush in behind the boat to fill it back up, in shallow water it will hit your stern and not be able to go under the boat – giving you a push. Finally, in shallow water the propeller is closer to the bottom which will have a much stronger effect due to the lack of available water.

WIND

When is the last time that you had a successful docking in high winds?  For most of us, the answer is “rarely”, wind can be a bit scary for most boaters.  Wind force on a boat can be figured out in the following manner with this formula:

Wind Force in POUNDS = .004*W*V²

Where “W” = Length*Height of your boat – Length*Underwater Area

And V is wind speed in knots

For example, let’s say you have Layne’s 22’ Chris Craft U-22, we can assume that the Height of the boat is roughly 4’ overall and it probably draws about 1’ max (not including the prop and rudder).  And let’s say that there is 25 knots of wind on your beam as you are coming into the dock.

The calculation would be as follows:

W= (22*4) – (22*1) = 66

Force = .004*66*625 = 165lbs of force!

Now we can begin to understand why people get hurt when they try and put their hands and feet out to try and stop the boat from hitting the dock, that 165lb force is substantial.  30 knots of wind is equal to 1 knot of current on the beam is a good rule of thumb.

As we just discussed with pivot point, if you are travelling ahead with a rudder straight ahead, your boat will want to turn into the wind.  Why? Well we just explained it, that wind has a large lever arm because the pivot point is forward, the reverse is true when backing.  These are powerful things to understand when docking in the wind, use them to your advantage and don’t fight them.  If you back and get sternway, your bow is going to fall off rapidly with the wind every time.  It is best to practice in an open area with wind to see how your boat reacts to the elements.

PUTTING IT ALL TOGETHER

Now that you have the understand of “why” things happen, let’s try some exercises to apply what we have just learned.  There are a few things to consider when approaching these; the shape of your transom, the length of your boat, and the size of your rudder.  A flat deep transom coupled with a short boat will make backing in a straight line more challenging (my V-Drive Arabian was a classic example of this). The reason is simple, your pivot point will be moved even farther aft on a deep flat transom, giving the rudder little chance and the boat a huge lever arm to work with.  Once the bow gets momentum one way or another, it will tend to increase in speed unless corrected early.  A long skinny boat will tend to back straighter with less effort.  The size of your rudder will also make a difference in how each boat will behave during these tests. Learning how your boat will react is critical when you need to back out of a narrow fairway without causing a scene. I recommend that you experiment in open water (don’t try this in a marina!) with little or no wind to start, then repeat all these with wind to see the difference in the reactions. 

(Reverse the rudder instructions if you have a left-handed propeller):

TEST #1:

1. Put your boat engine astern, and leave the engine running at idle astern.
2. Try and steer using the rudder without taking the boat out of gear.

TEST #2:

1. Put your boat engine astern at idle.
2. Take the boat out of gear once you have sufficient sternway.
3. Try and steer using the rudder after taking the boat out of gear.

TEST #3:

1. Put the rudder hard PORT and then give the boat a kick ahead on the engine.
2. Stop the engine and put the rudder amidships (centered).
3. Run the engine astern and leave it running astern.
4. Immediately shift your rudder hard STARBOARD (this may help counter propeller torque).
5. If the boat gets going one way or the other, shift your rudder and give a kick ahead to straighten out, then repeat step 1.

TEST #4:

1. Put the rudder hard PORT and then give the boat a kick ahead on the engine.
2. Stop the engine and put the rudder amidships (centered).
3. Run the engine astern.
4. Shift your rudder hard STARBOARD (this will help counter propeller torque).
5. Once you have sufficient sternway, take the boat out of gear and coast.
6. If the boat gets going one way or the other, shift your rudder and give a kick ahead to straighten out, then repeat step 1.

TEST #5

1. Put the rudder hard PORT and then give the boat a kick ahead on the engine.
2. Leave the rudder hard PORT
3. Run the engine astern.
4. Once you have sufficient sternway, take the boat out of gear and coast, leave the rudder hard PORT.
5. As the boat begins to torque with her stern going to Port, give a kick ahead to straighten out, then repeat step 3.

TEST #8 (my favorite)

1. Put the rudder hard PORT.
2. Run the engine astern.
3. Increase the throttle to a little stronger than idle. (you can try even more if you want)
4. Observe how the bow will fall around rapidly to starboard wanting to “swap ends” due to the propeller torque and rudder going in the same direction.
5. This is a fun way to quickly turn your boat around with very little effort.

As I mentioned earlier, every boat will behave a little differently, so these tests are great to figure out which method works best for your boat. To figure out “center” or amidships on your wheel, count the turns stop to stop and then take half the number back and that should give you a centered rudder. The number of turns stop to stop on your steering wheel may help make the decision on which method is easiest. Some boats take very few turns, others can take many.

One other little trick to try when there are high winds and docking is to put out the anchor upwind of the dock if possible.  Make sure you have enough line, then simply keep slipping the line until you get to the dock.  It is best to try this in the open first with a controlled environment to get the hang of it. This isn’t super quick and would take some planning, but it is very safe and can possible prevent some damage.

Shiphandling is a skill; it takes practice and lots of experience. I try and learn from every maneuver that I do. I never walk away saying, “that was a perfect job!” Stay humble and pick apart every landing you make. Learn from your failed dockings on what you did wrong and analyze how you can do it better next time.