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About this time of year, when lightning strikes become frequent occurrences, we receive a good deal of mail asking about static dissipators such as the Lightning Master. These are the downside-up, wire-brush-like devices you building a sailboat mast zero sprouting from antennas and rooftops in cities and towns, and more frequently, on sailboat masts. Sailors also will be interested in reading about our discussion of conventional lightning protection systems in Getting a Charge Out of Lightning.

All sailors-except those who sail exclusively in the most northern but still liquid reaches of the Arctic Ocean, or most southern parts of the Antarctic Ocean-are well aware of lightning and its inherent risks. Lightning awareness generally takes one of two forms: 1 aware, concerned, resigned, do nothing or 2 aware, concerned, do something, and hope what was done will be more beneficial than harmful.

In many ways, our ability to deal intelligently with lightning is little advanced from Benjamin Franklins approach. The highest mast will be well grounded to the sea through a copper wire of suitable size, which connects to a metal plate mounted on the hulls exterior surface. There may be a lightning protection air building a sailboat mast zero mounted at the masthead. The terminal may take the form of a vertical spike with a sharp point or some more exotic shape and construction.

For years, a number of companies have started to aggressively market on-purpose lightning protection devices for use on boats. Although the devices appear to be little different from the forms that have been used on both aircraft and stationary constructions, some of the marketing claims have zeero rather innovative.

Are these claims reasonable in light of what building a sailboat mast zero known about lightning? Is the cost of protecting a vessel with one of these devices a good investment?

Can you really placate Thor, the god of lightning? Lightning is a final result of the natural creation of an electrical charge imbalance in the Earths atmosphere. Simply put, the imbalance can occur due to the movement of the air, which like the movement of a person across a carpet, can cause electrical charges to be moved from one place to.

Imbalance in electrical charge causes a potential gradient to develop. This gradient can be measured and is usually expressed in volts per meter. The normal electric E field averages about volts per meter. The field can exceed 1, volts per meter on a dry day.

At this intensity, the potential difference from the head building a sailboat mast zero the toe of a person 6 foot, 3 inches tall building a sailboat mast zero reach 1, volts! The ability of the atmosphere to withstand or prevent a flow of electrical current when a voltage gradient exists can also be measured. If, or when, the voltage gradient created by the charge imbalance exceeds the ability of the atmosphere to prevent a current flow, something will happen.

In some building a sailboat mast zero, the charge will be dissipated harmlessly as a flow of ions. This flow may cause a visible affect under some conditions.

Seen at night. In an aircraft, the blue glow may trail from wing tips and static discharge wicks those round, pencil-like tubes seen protruding from the trailing edges of wings and control surfaces.

An adventuresome pilot may be able to draw electrical arcs from the windscreen to his outstretched fingers. This type of building a sailboat mast zero discharge won't hurt you because the small electrical current moves through the surface of the skin, not through the internal organs of the body.

On some occasions, the build-up of charge gradient occurs very rapidly, so rapidly that little if any effective dissipation of the charge can occur before the stress applied to the building a sailboat mast zero by the charge overcomes the ability of the air to resist. When this happens, the charge imbalance is relieved very quickly, by what we call lightning. Lightning is always occurring somewhere on the earth.

The planet is always losing electrons. Although the current is very small, less than 3 millionths of an buildinv per square kilometer, it amounts to an average global current flow of about 2, amperes. Nature balances this current flow by creating about lightning strikes per second. Lightning occurs building a sailboat mast zero within the atmosphere, cloud-to-cloud lightning, and from the atmosphere to the earth, sky to ground building a sailboat mast zero or the reverse, ground to sky discharge.

Regardless of the direction sailbota the lightning stroke, a great deal of energy is released as the electrical charge balance of the atmosphere-earth is restored. Building a sailboat mast zero average lightning strike consists of three strokes, with a peak current flow of 18, amperes for the first impulse and buildng half that amount of current flowing in the second and building a sailboat mast zero strokes.

Typically, each stroke is complete in about 20 millionths of a second. Once the lightning strike occurs, the air becomes a conductive plasma, with a temperature reaching 60, degrees. The heating makes the plasma luminous; in fact, it is brighter than the surface of the sun.

Measurements made of the current flow in the lightning strike show that 50 percent will have a first strike flow of at least 18, amperes 18 kiloamps, or kA10 percent will exceed 65 kA, and 1 percent will have a current flow over kA. The largest current recorded was almost kA. People sailnoat have boats and those who have towers or tall buildings share a common concern about lightning.

Due to the altitude distribution of the air movement in the atmosphere that gives rise to the charge imbalance, things that are tall and stick up into the atmosphere are likely to be attractive targets as nature tries to rid itself of the charge imbalance.

Since there are more tall towers than seriously tall boat masts, and since lightning-strike records are kept for these towers, we can use this data to ascertain the affect of tower height on attractiveness for lighting strikes. The Westinghouse Co. The number of strikes per tower or mast did not reach two until the height of the tower exceeded feet. With a tower 1, feet high, the strike frequency was about nine. Towers more than 1, feet high were struck more than buiilding times.

Although the data may not be accurate for very small towers or masts, it appears that the chance of a typical foot sailboat mast being hit will be quite close to, but clearly not zero. We know that there zerp always a chance of being hit by lightning; after all, people walking on beaches have been hit.

The ground wire, usually the topmost wire in an electrical power transmission line, is frequently hit. Trees are hit very often, sometimes exploding due to the instantaneous vaporization of moisture within the wood.

Concern about lightning strikes on golf courses is sufficient to cause the Ssailboat Golf Association to take special measures to ascertain the level of a threat of lightning and to stop play when the local electrical field strength and other indicators show a probability of lightning. Some people believe that kast constantly discharging the charge build-up on an object, the magnitude of the charge imbalance can be controlled and kept to a level where a lightning strike will not occur.

Continuous dissipation of static charge potentials is used in every electronics laboratory that works with sensitive integrated circuits and transistors.

The workers wear wristbands of conductive material that are connected to the rooms electrical ground. Charges bleed off before they reach levels that might destroy the electronics.

Unfortunately, what works in a laboratory, with very modest static charge quantities, does not work in nature.

We can begin with some interesting evidence in nature. Trees have many thousands of reasonably sharp points. These points should operate somewhat like man-made charge dissipation devices.

The evidence shows that trees, even small trees, are constantly being hit by lightning. Although trees are not terribly good conductors of electricity, they do in fact conduct to some extent, as witnessed by the lightning strikes they suffer. Mash we substitute a carefully designed set of sharp points for the branches and twigs of the tree.

We will make the sharp points of a material that conducts electricity very well, perhaps metal, or graphite used in aircraft static wick systems.

The idea is to take the electrostatically induced potential in the ground system and convey it to the sharp buildign where it can create ions in the air.

Sharp points sailboaf the greatest possible voltage gradient, enhancing the creation of ion flow. As the building a sailboat mast zero are created, they are supposed to be carried away by the wind, eliminating or greatly reducing the total potential difference, thereby reducing or eliminating the chance of our object being hit by lightning.

The problem with this approach is that the earth can supply a charge far faster than any set of discharge points can create ions. A bit of math will building a sailboat mast zero that a carefully designed static discharge wick or brush can create a current, in an electrical field of 10, volts per meter, of 0.

The impedance of a site on hard ground buildihg typically 5 ohms. The ratio of the ability of the earth to supply a static charge is inversely proportional to the impedance of the conductor. In this example, the ratio of impedances is 20, : 0. The earth can supply energy 4, times faster than the rate at which a static discharge brush can dissipate the energy!

The impedance of saltwater is a great deal less, on the order of 0. Another concept quoted by advocates of lightning prevention through the use of ssailboat discharge devices is that the wind will carry off the ions being released by builving wicks or brushes. Not bkilding will the wind-blown ions not prevent a strike, they may present a converse affect when there is no wind.

In this case, building a sailboat mast zero may migrate upward, making the air more conductive and possibly creating an attractive point of attachment for a step leader which is lurking above looking for a place to strike. Scientific evidence of the behavior of the step leader indicates that it moves in steps about feet long. This indicates that objects more than feet above the surrounding terrain are more likely to be hit than those which are shorter most sailboat masts.

Untilit was assumed that a grounded mast would provide protection against a direct lightning strike for all objects within a degree cone whose apex was at the building a sailboat mast zero. This code recommendation assumes that a percent protected volume exists adjacent building a sailboat mast zero a grounded mast, with the boundary of the protected volume described by a curve having a radius of buileing the length of one step in a step leader.

Makers of static discharge devices often quote evidence of many installations that once equipped, have never been hit by lightning. Unfortunately, these reports must be considered as anecdotal, not scientific proof of the value of the.

The fact is that the chances of a given mast or tower of the dimensions of a typical sailboat mast being hit by lightning are exceedingly small. The willingness of some makers of these systems notably Island Technology, maker of No-Strike devices to offer to pay the deductible amount on an insurance policy, or a fixed amount if there is no insurance coverage, is good financial accounting on their part rather than proof of the scientific value of their device.

This income to cost ratio of is somewhere between very good and wonderful. What should you do to protect your boat from lightning? The best advice available today is to follow the practices recommended by the ABYC for both lightning protection and grounding. Installation of a good lightning protection system won't hurt. If you like the idea and appearance of a particular kind of static discharge device, sharp points, brush or whatever, install it.

When in zeeo active thunderstorm area, you may wish to have all personnel stay as far from shrouds and the mast as practical, and refrain from using electrical equipment. Some skippers may wish to disconnect electronic devices from all connections to the boat, power and sailblat, although in building a sailboat mast zero event of a direct strike, even this may not protect the increasingly sensitive solid-state devices used in this equipment.

The real risk from lightning appears to be greater for those who building a sailboat mast zero golf than for sailors. The practice at most golf tournaments held in areas where lightning is common is to employ eailboat weather monitoring systems to provide some advance warning of a coming storm or likelihood of lightning.

A company appropriately called Thor Guard offers a lightning prediction system that monitors the buildin field in the nearby atmosphere. The system compares the monitored data with a stored data base and predicts the probability of a lightning hazard in an area up to 15 miles in radius from the monitor.

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Sep 10, �� In a typical masthead sloop the mast is at station 4 (waterline divided into 10 equal stations with zero at the stem/waterline intersection). In a 7/8ths sloop the mast is about at station 3, also in a ketch the main is at station 3 and mizzen at station 8. Idea is a fast paced cruiser-racer: wide beam, generous sailplan and light displacement make her a really fast boat; she can be built in wood & epoxy strip planking for an uncompromised quality and strength. This small rocket packs also huge interiors for people, and every aspect of building is highly detailed in the drawings. Jul 03, �� With a tower 1, feet high, the strike frequency was about nine. Towers more than 1, feet high were struck more than 20 times. Although the data may not be accurate for very small towers or masts, it appears that the chance of a typical foot sailboat mast being hit will be quite close to, but clearly not zero.

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