Friday, July 10, 2009

Tis the Season...

Preparing for a storm front aboard Karma during the 2009 NOOD Regatta.

With as wet of a Spring/Summer season as we have had, it is more a matter of "When" versus "if" one of the many boats on Lake Michigan make see electrical interference courtesy of mother nature. The chances of thunderstorms over the water are increased on days when the surface temperature rises on land (warm/humid) and that is layered over by cold air patterns. This produces unstable air masses. The warm air filled with water vapor rises and mixes with the upper colder air and a thunderstorm is produced.

Enclosed is an article on what you can possibly do to manage these situations. (disclaimer: There are many opinions on what to do, but in truth there is no panacea for preventing a lighting strike. As the article states the best on the water solution is to manage safety of your passengers and essential electrical instrumentation.)

Lightning Protection
What is a lightning strike?
We all know what a bolt of lighting is. Lightning can be unnerving just ask any Dog.
Lightning is formed by the difference between positive and negative charges. Lightning strikes when the electrical potential becomes greater than the resistance (insulation) of the air, and forces a conductive path to earth (ground or water surface) and will use the best conductor in its proximity. A boat will be a better conductor than air, so if you are close to a storm, lightning will look to you to find an easier path.What are the chances you will get struck?

BoatUS published these statistics.

Note the highest incidents are on sailboats, due no doubt to the tall masts. Catamarans are even worse due to the width falling close to the cone of arc from a strike.What can happen when you are struck by lightning?

Large merchant ships that are made of steel, are good conductors, and so when these vessels are struck by lightning as they often are, the voltage is dispersed to water by the vast quantities of steel plate. These vessels are relatively safe from lightning.However for small boats, once a lightening strike hits you and electrical charge gets into the boat, side flashes can destroy electrical instruments and engine controls, and knock holes in the side of the boat, as they find their way to water. Side flashesThis is not only expensive to fix it is a real safety issue. Holes in boats no good, destroyed engine and instruments no good.To help prevent damage to you and your boat, we need to provide a better conductor than the boat itself, so from the highest, or most extreme point, we need to provide a path to ground i.e. the water.

Sailgemini gives this report of a strike Here you can learn what they did in preparation and what damage occurred. They spent 3 months repairing the damage.

Before we look at what you can do to prevent damage in case you are hit we will take a look at how you can avoid getting hit and what precautions you can take while out on the water.
Warning of impending strike or thunderstorm

When on the water or going out on the water Check weather status. Thunderstorm generally appear in the afternoon, with 70% occurring between noon and early evening. watch for development of large well defined dark clouds.

Tools that will help you follow weather patterns;
Thunderbolt the personal lightning detection device
-XM weather on a chartplotter
-Cell phones can show weather radar
-NOAA forecast via VHF
-Precautions to take if a storm is imminent.

Depending on what kind of boat you are in, planning for a lightning storm or potential strike should include Protection of Human Life and essential boat equipment.

-Preferably get off the water

-If not keep low, and in center of boat

-Keep inside and in middle of cabin

-Avoid high areas or tall objects

-Keep body parts out of water

-Stay away from metal especially grounded metal

-Do not touch any part of a lightning protection system

-A sailboat mast forms part of a lightning protection system

-Disconnect electrical & electronics equipment

-Put any movable electronics on the oven. This may sound silly but an oven is a
faradays cage.

-Lower antennas that are not part of ground protection system

-Turn off Engine controls

-Lower outriggers, outriggers are perfect for attracting a strike

-Learn CPR. CPR can resuscitate a victim of a lightning strike