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Seafaring A-Z Alphabet – “K” is for…


Seafaring “K” is for…

Let’s get this rolling with:



Keel – On ships, the “keel” is a beam around which the hull of a ship is built. The keel runs in the transverse centreline of the ship, from the bow to the stern, and serves as a basic foundation or spine of the structure, providing the major source of structural strength of the hull.

The keel is generally the first part of a ship’s hull to be constructed, and laying the keel, or placing the keel in the cradle in which the ship will be built, is often a momentous event in a ship’s construction — so much so that the event is often marked with a ceremony, and the term lay the keel has entered the language as a phrase meaning the beginning of any significant undertaking.

Modern ships are now largely built in a series of pre-fabricated, complete hull sections rather than being built around a single keel, so the start of the shipbuilding process is now considered to be when the first sheet of steel is cut.

The keel contributes substantially to the longitudinal strength and effectively local loading caused when docking the ship. The most common type of keel is the “flat plate keel”, and this is fitted in the majority of ocean-going ships and other vessels.

Duct keels are provided in the bottom of some vessels. These run from the forward engine room bulkhead to the collision bulkhead and are utilized to carry the double bottom piping. The piping is then accessible when cargo is loaded.

If a ship suffers severe structural stress — classically during a shipwreck when running aground in a heavy sea — it is possible for the keel to break or be strained to the extent that it loses structural integrity. In this case the ship is commonly said to have “broken its back”.

Such a failure means that the entire structure of the ship and its machinery has been compromised and repairing such damage would require virtually re-building the ship from the ground up. A ship that has broken its back is almost certainly “unsalvageable” and subsequently written off by its insurers.

Vessels have also been known to “break their back” when loading heavy cargoes too quickly. There have been numerous bulk carriers which have been loading iron ore, and as they haven’t been able to ballast fast enough – the weights have caused the keel to snap.

The word “keel” comes from Old English “cēol”, Old Norse “kjóll”, = “ship” or “keel”. It has the distinction of being regarded by some scholars as the very first word in the English language recorded in writing, having been recorded by Gildas in his 6th century Latin work “De Excidio et Conquestu Britanniae”, under the spelling cyulae Carina is the Latin word for “keel” and is the origin of the term careen (to clean a keel and the hull in general, often by rolling the ship on its side).

Keel - Haul

Keel haul

Keel-Haul – Keels aren’t just parts of the vessel which are important from a construction perspective. Back in history they were also something that punished sailors were dragged down through the water across.

It was a form of punishment once meted out to sailors at sea, which saw the sailor tied to a line that looped beneath the vessel, thrown overboard dragged under the ship’s keel. On large ships, victims were keelhauled from port to starboard while on smaller vessels they had to endure being keelhauled from bow to stern.

As the hull was usually covered in barnacles and other marine growth, if the offender was pulled quickly, keelhauling would typically result in serious cuts, loss of limbs and even decapitation. If the victim was dragged slowly, his weight might lower him sufficiently to miss the barnacles, but this method would frequently result in his drowning.

Keelhauling was legally permitted as a punishment in the Dutch Navy by a Dutch ordinance of 1560, and the practice was not formally abolished until 1853. Keelhauling has become strongly associated with pirate lore.

The earliest known mention of keelhauling is from the Greeks in the Rhodian Maritime Code (Lex Rhodia), of c. 800 BC, which outlines punishment for piracy. It is also pictured on a Greek vase from the same era.

The reputation of this brutal punishment means the term still survives today, although usually in the sense of being over-punished or receiving extreme discipline for lightly violating the rules.

King Spoke

King spoke

King spoke – It perhaps goes without saying that the ship’s wheel is used to steer the ship, either used to keep it on course or to change the heading as required. But stick with us.

Together with the rest of the steering mechanism, it forms part of the “helm”. It is connected to a mechanical, electric servo, or hydraulic system which alters the vertical angle of the vessel’s rudder relative to its hull.

In most modern ships the wheel is replaced with a simple toggle that remotely controls an electro-mechanical or electro-hydraulic drive for the rudder, with a rudder position indicator presenting feedback to the helmsman.

When and where a more traditional wheel is used, then one of the handles/ spokes is provided with extra grooves at its tip which could be felt by a helmsman steering in the dark and used by him to determine the exact position of the rudder.

This was the “king spoke” and when it pointed straight upward the rudder was believed to be dead straight to the hull, and so is uppermost when the helm is amidships.
The king spoke is often marked with a ring carved on it or by a Turk’s head knot fixed round the spoke.

Tying Knot


Knots (Tying) – Knots are one of the mainstays of seafaring heritage, skill, and expertise. The use of knots is the measure of a mariner – from tying bowlines blind behind your back, through to a flick of the wrist and a figure of eight skitters up they line. Knots are not just for show – they are vitally important too.

In essence, a knot is a method of fastening or securing linear material such as rope by tying or interweaving. It may consist of a length of one or several segments of rope, string, webbing, twine, strap, or even chain interwoven such that the line can bind to itself or to some other object (the “load”).

Knots have been the subject of interest for their ancient origins, their common uses, and the area of mathematics known as knot theory. Knots are cunning, clever and wonderful. There is a thing of innate beauty in a well-constructed knot.

There is a large variety of knots, each with properties that make it suitable for a range of tasks. Some knots are used to attach the rope (or other knotting material) to other objects such as another rope, cleat, ring, or stake. Some knots are used to bind or constrict objects. Decorative knots usually bind to themselves to produce attractive patterns.

Knots are fast and useful, but unlike a more time consuming splice, they do weaken the rope in which they are made. So there is a trade off – the speed and effectiveness of knots, but the knowledge that a rope is weakened as a result.

Knots differ in the effort required to untie them after loading – but the right knot done well should really come undone easily – and that is what separates those that are very difficult to untie, such as the water knot, as these are said to “jam”. They lock part of the knot and tightly bind it with pressure from other parts of the rope. Those knots that come untied with less difficulty, such as the reef knot or bowline, are referred to as “non-jamming”.

The list of knots is extensive, but common properties allow some system. For example, loop knots share the attribute of having some kind of an anchor point constructed on the standing end (such as a loop or overhand knot) into which the working end is easily hitched to using a round turn. An example of this is the bowline.

While the other form is of “constricting knots” – these often rely on friction to cinch down tight on loose bundles; an example is the Miller’s knot. Knots may belong to more than one category.

The proper tying of a knot can be the difference between an attractive knot and a messy one, and occasionally life and death too. This is artistry with purpose, and it should still be a thing of immense pride for any mariner. No amount of technology will erode the need for knots – and so they should be continued to be practiced and perfected.



Knots (Speed) –As with any other means of transport ships have always needed to know how fast they are going. However, with no landmarks to gauge their progress across the open sea, sailors couldn’t tell how fast or how far they were traveling. In order to this a unit of measure was needed, and a means of measuring it. Enter the nautical mile and the knot.

When the nautical mile – 1.852 kilometres – was introduced in the 15th century, sailors suddenly had a handy standard against which to measure speed and created the “chip log”, the world’s first maritime speedometer.

The “chip log” consisted of wedge-shaped piece of wood, a small glass timer, and a really long rope. The wood was attached by line to a reel, and weighted on one edge to float perpendicularly to the water surface and thus present substantial resistance to the water moving around it.

The chip log was “cast” over the stern of the moving vessel and the line allowed to pay out. As one sailor watched the sand empty through the glass, his shipmate held the line as it played out behind the ship and counted the knots, placed at a distance of 8 fathoms – 47 feet 3 inches (14.4018 m) from each other, as they passed between his fingers.

Dividing that 14.4 meters by 30 seconds told them that one knot equalled 1.85166 kilometers per hour, or one nautical mile. By performing the calculation using the actual number of knots that unspooled, the sailors were able to measure the ship’s speed.

The knot count would be reported and used in the sailing master’s dead reckoning and navigation. Thus the term derives from counting the number of knots in the line that unspooled from the reel of a chip log in a specific time.

The knot is a unit of speed equal to one nautical mile (1852 metres) per hour, approximately 1.151 mph. The ISO Standard symbol for the knot is “Kn”. But “Kt” is also common.
Worldwide, the knot is used in meteorology, and in maritime and air navigation—for example, a vessel travelling at 1 knot along a meridian travels approximately one minute of geographic latitude in one hour.

Today, maritime speed is determined by ultrasonic sensors or Doppler measurement. But the instrument for measuring a vessel’s speed is still called a log. While marine and aeronautical distances are still measured in nautical miles.


Damaged ship

Knock-for-knock – Marine insurance is a complicated business – so anything which can make it more straight forward, simple and effective is important. One such measure is the concept of insurers accepting some levels of loss between themselves, this is where the “knock-for-knock” concept comes in.

A knock-for-knock agreement is an agreement between two insurance companies whereby, when both companies’ policy-holders incur losses in the same insured event. The process originated in the motor insurance market – but is common in the marine industry and oil and gas sectors.

A ‘knock-for-knock’ clause in a contract is usually included with the intention that each party should bear responsibility for any damage or loss to its own property, or accident or injury to its own staff, without making a claim against the other party, even if the other party is at fault.

In essence, each insurer pays the losses sustained by its own policy-holder regardless of who was responsible. The rationale is economic and administrative efficiency.

While an insurer may be able to pursue a recovery from the party responsible for an accident or from its policy-holder, this is a costly administrative procedure. The knock-for-knock agreement simplifies recovery claims among insurers and, over time, attributes costs fairly among insurers.

However, knock-for-knock agreements between insurers have been criticised as unfair on the party not responsible for an accident. Under English jurisdiction, it appears that, depending on the wording and exact circumstances, a knock-for-knock clause might protect a party who is performing a contract badly, but it might not protect a party who does not perform the contract at all – unless there is very clear wording in the contract to state that this is what the parties have agreed to.

“Knock for knock” is a common contractual arrangement in the oil and gas industry. The operator of an oil and gas property requires the assistance and expertise of many kinds of contractors, including drilling companies, well service companies, facility constructors, equipment suppliers, and caterers. Generally, the operator will engage these services under a ‘Master Service Agreement’ which sets forth the essential commercial terms under which the work will be performed. One of these terms is the allocation of the risk of loss to people and property.

In general, a knock-for-knock agreement means that each party working on an oil and gas worksite, or a vessel — the operator and each contractor — agrees to protect and indemnify all the other parties against injuries to that party’s employees and agents, and destruction or damage to that party’s property. This allocation is not based upon the fault or culpability of the party whose employee was injured or whose property was damaged. The goal is the efficient defence and payment of a claim through having a single party responsible for the loss.

Knock-for-knock clauses have been incorporated into some standard charterparties, such as BIMCO’s Supplytime 2005 (clause 14(b)), Towcon 2008 (clause 25) and Towhire 2008 (clause 23). Indeed, English courts have recognised knock-for-knock clauses as being a market practice in offshore operations and have given full effect to such clauses in a number of English court decisions.

Koschmieders Law


Koschmieder’s law – Even with modern technology, one of the most important aspects of maritime navigation and a safe passage is visibility.

Meteorological visibility refers to transparency of air and visibility is a measure of the distance at which an object or light can be clearly discerned. It is reported within surface weather observations either in meters or statute miles, depending upon the country.

Visibility is the greatest horizontal distance at which selected objects can be seen and identified. Reduced visibility often occurs during periods of heavy rain and snow and also occurs when sunlight is scattered or absorbed by atmospheric particles. Fog droplets and haze particles are small enough to scatter and absorb sunlight, leading to reduced visibility. The meteorological definition of fog is a cloud (stratus) which has its cloud base on or close to ground, and reduces visibility to less than 1 km.

Haze is caused when sunlight encounters tiny pollution particles in the air. More pollutants mean more absorption and scattering of light, which reduces visibility. The attenuation of light due to scattering and absorption by atmospheric particles is referred to as extinction. In general, scattering is the primary cause of light extinction and therefore visibility reduction. The smallest pollution particles (< 2.5 microns) scatter sunlight more efficiently than larger particles. Even in the dark, meteorological visibility is still the same as in daylight for the same air.

Visibility is so fundamental to shipping that the rules of conduct at sea change when navigating in or near an area of restricted visibility. Different rules apply in restricted visibility. Restricted visibility, whatever the cause, includes any situation where you cannot see the other ship or its navigation lights.

Rule 19 “Conduct of vessels in restricted visibility” of the Collision Regulations states that in such conditions there are no ‘stand-on’ or ‘give-way’ vessels. Every vessel must take action and every vessel must proceed at a safe speed with its engines ready for immediate manoeuvre.

It becomes almost a case of all bets are off…and everyone has to navigate with extreme caution and readiness. A safe lookout is essential, and so assessing if the ship is getting close to another and/or if there is a risk of collision is the key.

Visibility is estimated using Koschmieder’s Law (V = 3/σ), where V is the Visibility and σ is the extinction coefficient in km-1. The law relates to the apparent contrast of an object against a sky background, at a given distance of observation.