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Load Balance and Directional Stability

October 27th, 2015 by

Kayak-sailing 102  Load Balance And Directional Stability.

Prerequisite for this class is Balancing the Leeboards.

Most people are aware that placing weight in the very bottom of a boat acts as ballast and stabilizes a craft, and that adding a weight high above the waterline will make the boat less stable, but it is not so widely understood how the distribution of weight fore and aft affects the boat’s directional stability.

What I mean by directional stability is how controlled a boat will track through the water.  A directionally stable craft will hold a steady course with little input from the helmsman.  A directionally unstable one will change directions on its own, often without warning and can be difficult to steer.

Probably the most important feature of a well-balanced kayak is a properly designed hull.  The overall length of craft, as well as how much rocker the hull has (hull curvature from bow to stern) both play very important roles in regards to directional stability, but so does cargo placement, specifically, how and where this weight is distributed throughout the hull.

Typically in a small craft such as a kayak, the paddler makes up most of the cargo weight.  And in well designed kayaks, the seating position should allow the boat to sit relatively level in the water, allowing it to track through the water in a controlled manner.  So it’s important to know that having a seat too far forward or too far aft will alter the way the boat handles.

An unbalanced kayak with too much weight forward will have a bow that rides too deeply in the water and a stern that rides too high.  In a bow-heavy boat, the bow will effectively act as a keel, biting deeply into the water, thereby reducing the sideways sliding motion of the bow.  At the same time, the stern will loose it’s keel-like effect and slide sideways through the water too easily.  Patti and I call this action “bow-keeling”.

While a limited amount of bow keeling can be beneficial in a sailing kayak by allowing the bow to track to windward more efficiently, too much weight forward can make the kayak want to “weather-cock” or turn into the wind on its own, requiring near constant corrective strokes to stay on course.  Anyone who has been in one of these boats knows that they can be frustratingly difficult to steer.  Once a directional change is initiated either by paddle stroke or hull steering, the stern will want to slide out toward the outside of the turn, requiring a quick corrective stroke to bring it back in line. Then, typically, the corrective stroke will cause the stern to slide back in the opposite direction, past the desired position, and require another corrective stroke.  You see where this is going.

On the other side of the scale, an unbalanced kayak with too much weight in the stern will have its own control issues.  In this case the bow will ride high above the water, allowing it to slide sideways, and the stern will sit too deep, acting like the keel.  Though a stern-heavy kayak can be difficult to steer, it is usually easier to deal with.  The two main control problems with boats having overly heavy sterns are, a difficulty in making tight turns due to the stern tracking too well, and a situation where the boat is constantly wanting to turn downwind because the bow is sliding away too easily.

So… how does one correct an unbalanced kayak?

Shifting cargo either fore or aft is an easy way to do it.  Also if the kayak has an adjustable seat, sliding the seat either fore or aft can be a quick fix.

The next thing to try is adding weight to a compartment in the boat.  Since it’s generally desirable to keep a boat as light as possible, the position of weight, as well as the type of weight used should be considered.

By positioning the weight as close to the bow or stern as possible, one can minimize the amount of weight needed.

As for what kind of weight to use, a good option is to add safety gear such as: dry clothing (in a dry bag), a first aid kit, a water bottle, food, a kayak repair kit, etc.  Being prepared for emergencies is always smart.  And while basic safety gear should always be onboard, another option is to add water weight.  Water is desirable not only because it is dense and requires very little space, but perhaps more importantly it remains neutrally buoyant when submerged.  Added benefits include being able to rinse the salt off at the end of the day, and even drink it if need be.

Patti and I sometimes correct for a bow-heavy boat by adding a small solar shower (basically a water bag with a plastic shower head attached to it) to the aft compartment, and placing it as far back in the hull as possible.

Below is a list of three common symptoms of an unbalanced kayak and how to fix them.

1) The kayak is tracking poorly and difficult to steer, especially when going off the wind (downwind).  It may be bow-heavy.  Try lightening the bow by shifting gear aft, shifting the seat aft, and/or adding weight to the stern compartment.

2) The kayak is constantly wanting to turn up into the wind.  Again, it may be bow-heavy.  Try lightening the bow by shifting gear aft, shifting the seat aft, and/or adding weight to the stern compartment.

3) The kayak is constantly wanting to turn downwind.  It may be stern-heavy.  Try lightening the stern by shifting gear forward, shifting the seat forward, and/or adding weight to the bow.

4) The kayak turns sluggishly, tracks like an arrow while traveling directly downwind, and may also be difficult to turn into the wind.  Again, it may be stern-heavy.  Try lightening the stern by shifting gear forward, shifting the seat forward, and/or adding weight to the bow.

Finally, it should be noted that some boats are just not well designed and will have poor handling characteristics no matter how you balance them.  Even though balancing is always desirable, and will likely improve the overall handling, let’s face it, adding all the cream and sugar in the world into a bad cup of instant coffee will not miraculously change it into a fresh cup of gourmet java.

That said, if you have one of these instant coffee kayaks you can always add a rudder to improve the handling.  Rudders can often compensate for severely unbalanced boats and greatly improve their directional control, but they too can have their issues.  More about rudders in the next post.

I hope this information proves useful.

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Happy Kayak-Sailing!

5 thoughts on “Load Balance and Directional Stability

  1. Thank you for this information. I do have some problems with the balance and in am going tot try out some of your tips.
    Greetings from Holland, Europe,
    Henk.

  2. My wife and I experienced the bow heavy plowing when we borrowed an open cockpit tandem with a rear sliding seat. I was very frustrated with the boats behavior until we beached and slid the back seat aft to trim the boat. WOW what a difference, from that point on it cruised like a dream and we had a great day. Thank you

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