Blog May 2014

What Is a Maritime Expert Witness?

 A maritime expert witness is a person who possesses knowledge of matters relating to the construction of ships, marine shipping, or navigation and who offers this expertise in a court of law. They prepare an analysis of situations and present the information to attorneys, judges and juries. They offer general insight on the cause of an accident, reconstruct the events of an accident and determine environmental threats. They also may be called upon to analyze the cause of personal injury suits and product liability suits.

An expert witness is a person who has specific knowledge in a given field and is called to testify in a court of law. The court permits this person to testify without having been present at the scene of the crime due to specialized training or experience in a given field. Unlike other witnesses, who are only permitted to give testimony based on observed facts, an expert witness gives technical testimony based primarily on expertise and opinions. The court allows either the prosecuting or defense attorneys to use such testimony to support claims made by the prosecution or the defense.

A maritime expert witness analyzes the cause of marine causalities and personal injuries during litigation for either the defendant or the plaintiff. An maritime expert witness may also be called to testify in environmental cases and offer analysis on the threat of hazardous materials such as lead, toxic PCBs and other toxic metals either aboard the ship or at the ship yard.

A maritime expert witness may be called upon to recreate the technical events causing an accident. An expert witness can provide testimony and analysis on the design, construction, and operations to determine the cause of the injury. A maritime expert witness is instrumental in product liability cases and can help determine whether an accident was due to faulty ship design or construction, management of the ship, or maritime operations.

Our services are available to offer expert witnesses when maritime accidents occur and the cause is unclear. An exceptional maritime expert witness service will provide the knowledge of fundamental maritime principals to advance the case and demonstrate the probable cause and effect necessary to the courts. The service will always include an analysis either supporting or defending claims and prepare reports for litigation. The analysis should cover each phase of the design, maintenance and operation of either the ship yard or the ship.

WIND AND WAVES                    

The relationship between the wind and the waves is very important to boat to skippers. So important  that a completely new classification system was designed as a guideline incorporating both wind speed and the wave conditions most readily found at those speeds. This system, called the Beaufort Scale, was developed in 1805 by Admiral Sir Francis Beaufort of the British Navy. It is a guideline for what can be expected in certain conditions and a weather classification system. It assumes open ocean conditions with unlimited fetch.

Aside from just wind speed, temperature is also a factor in creating waves. Warm air (which rises) moving over water has a less acute angle of attack on the surface than does cool air (which sinks). A cold front moving across open water will create much steeper waves and hence create breakers sooner than a warm front moving at the same speed.

Also, a change in wind direction over existing waves can create confusion and hence larger waves. If a wind has been blowing northeast over an open body of water for three days and suddenly switches to northwest over that same body of water, new wavelettes will form within the existing system of waves. The energy of both systems will multiply to create larger waves.

When a wave system meets a current flow one of two things can happen. If the wind and current are both going the same direction, it tends to smooth out the waves, creating long swells. If the current and wind are moving in contradicting directions, it will create much steeper and more aggressive waves.

MAKING SENSE OF THIS

So, what does all this mean? Why is it important to know how waves are made? Well... You can determine several things from waves.

One of the things you can tell based on waves, is boat speed. This assumes that your vessel is a displacement ship, like a keelboat, and not a planing one like a speedboat. When sailing a displacement vessel, the boat is constantly displacing a large chunk of water as it moves along. The heavier the boat, the deeper the trough it carves through the water. Now, along with the physics of waves we discussed above, we can add that the faster a wave travels, the longer it is. As a boat's speed increases, the number of waves that it pulls along the hull decreases until the boat is actually trapped between the crest and trough of a single wave that it has created itself moving through the water.

Understanding the Waves        

The first rule of waves, especially in the open ocean, is that there are no rules. Kind of a hypocritical statement considering the intent of this, but it is a cold hard fact. There are simple physical factors that makeup the "normal" wave, but within the forces of nature, there a myriad of other factors that need be considered. Regardless, an understanding of what makes a wave can be of considerable benefit  to the everyday sailor.

There are three factors that make up waves:

• Wind speed Length of time the wind has blown
• Distance of open water that the wind blows over; called fetch

All of these factors have to work together to create waves. The greater each of the variables in the equation, the greater the waves. Waves are measured by:

• Height (from trough to crest) Length (from crest to crest) Steepness (angle between crest and trough)
• Period (length of time between crests)

Waves are never created in one uniform height. Waves fall into a systemic pattern of varying size. Therefore, in order to classify wave height we determine the significant wave height, which is the average of the highest 1/3 of the waves in a system. This is how weather reports will specify wave height. Once you have the significant height, it is simple to determine the theoretical average height, the highest 10% and the highest wave sizes in a given area. Mathematically speaking, it's simple arithmetic based on predetermined ratios:

TYPES OF WAVES

Waves take their time to develop; they don't spontaneously erupt from the ocean. It takes a certain speed of wind to blow over a certain distance for a considerable length of time to create lasting waves.

There are three different types of waves that develop over time:

• Ripples
• Seas
• Swells

Ripples appear on smooth water when the wind is light, but if the wind dies, so do the ripples. Seas are created when the wind has blown for a while at a given velocity. They tend to last much longer, even after the wind has died. Swells are waves that have moved away from their area of origin and are unrelated to the local wind conditions -- in other words, seas that have lasted long beyond the wind.

The definition of swells can be a bit confusing when you understand that waves never actually go anywhere. The water does not travel along with the waves, only along with the current -- two mutually exclusive elements of water animation. If two people stand at either end of a long rope and undulate their arms up and down in an equal rhythm, waves will develop along the length of the rope that appear to move from one end to the other. The rope fibers aren't actually moving at all, other than up and down. This is exactly what is happening with waves. The speed, or velocity of the wave is measured by how long it would take a wave to pass a given point crest to crest -- say a line drawn on the ground beneath the rope. There is a slight movement of the water particles within a wave, Waves can be further described as:

• Non-Breaking
• Breaking

A non-breaking wave, is a "normal" rolling wave. A breaking wave is one who's base can no longer support it's top and it collapses. Depending on the size, this can happen with considerable force behind it -- 5 to 10 tons per square yard. Enough force to crush the hull of a ship. When the ratio of steepness of a wave is too great, it must break. This happens when a wave runs into shallow water, or when two wave systems oppose and combine forces

Next: Wind & Waves     

Watch Schedules and Ship's Bells       

I was recently asked a question concerning why ships sounds bells and what they signify.

So here we go………

As early as the 15th Century, a bell was used to sound the time onboard a ship. (Time, in those days, was kept with an hourglass.

The bell was rung every half hour of the 4 hour watch. A 24 hour day was divided into six 4 hour watches, except the dog watch (16:00 - 20:00 hours) which could be divided into two 2 hour watches to allow for the taking of the evening meal.

The bells were struck for every half-hour of each watch, with a maximum of eight bells. For instance, during the Middle Watch you would hear the the following:

00:30 1 bell
01:00 2 bells
01:30 2 bells, pause, 1 bell
02:00 2 bells, pause, 2 bells
02:30 2 bells, pause, 2 bells, pause, 1 bell
03:00 2 bells, pause, 2 bells, pause, 2 bells
03:30 2 bells, pause, 2 bells, pause, 2 bells, pause, 1 bell
04:00 2 bells, pause, 2 bells, pause, 2 bells, pause, 2 bells

At eight bells your watch was over! All other 4 hour watches followed this same procedure except the Dog Watches.

At the end of the First Dog Watch, only four bells were struck, and the Second Dog Watch bells were struck like this: 6:30 PM, one bell; 7 PM two bells; 7:30 PM, three bells; and at 8 PM, eight bells.

Chances are that at some point in your boating experience you will probably want to anchor. You may want to stop and fish, swim, have lunch or stay overnight. You might need to drop anchor  to control the boat if bad weather is blowing you ashore or if your engine has quit and the wind and current are pushing you into shallow water or other boats.

Long before you experience the reason, the first step in anchoring is to select the proper anchor. In spite of manufacturer’s claims to the contrary, there is no single anchor design that is best in all conditions. On most pleasure boats, the three anchors you will find most are the fluke or danforth type, the plow and the mushroom anchor.           

Mushroom anchors do not have the holding power of a fluke or plow anchor and should only be used on small, lighter weight boats. Check with your  local marine supply store . They can help you select the proper anchor for your boat and for the waters in which you will be boating.     

Anchors also must have something to attach them to the boat. This is called the anchor rode and may consist of line, chain or a combination of both. The whole system of gear including anchor, rode, shackles etc. is called ground tackle.

The amount of rode that you have out (scope) when at anchor, depends generally on water depth and weather conditions. The deeper the water and the more severe the weather, the more rode you will put out. For recreational boaters, at a minimum you should have out five to eight times (5 to 1 scope for day anchoring and 6 to 8 to 1 for overnight) the depth of the water plus the distance from the water to where the anchor will attach to the bow.

For example, if you measure water depth and it shows four feet and it is three feet from the top of the water to your bow cleat, you would multiply seven feet by six to eight to get the amount of rode to put out.

Thinking ahead can make your boating experience even more pleasurable.