When atmospheric pressure increases, the sea level is slightly lowered in the highpressure cell. When pressure is lower, the sea level is slightly higher. The changes are only in inches and fractions of inches.
Approximate number of statute miles a cold front moves in a day (more in winter, less in summer). Warm fronts move approximately 200 statute miles a day.
Avoid a storm’s center by tracking its movements in relation to your course by putting your back to the wind and pointing to the left; that’s where the center of the storm lies.
Rule of 1/12
Tides do not rise or fall at an even rate. Divide the tide’s range by 12. A change of 1/12 occurs in the first hour, 2/12 in the second hour, 3/12 in the third hour, 3/12 in the fourth hour, 2/12 in the fifth hour and 1/12 in the sixth.
The Weather Clock
If you’re in the Northern Hemisphere as you face the wind, and it changes in a clockwise direction, it is generally an indicator that fair weather is on the way. Counterclockwise movement means just the opposite.
Navigation by Estimation
The attention span of the average helmsman working at peak efficiency is 30 minutes, dropping off considerably until four hours, after which he is more a danger than a helping hand.
In a crossing situation with another boat at night, note the other vessel’s position relative to a low star. If the boat and star don’t separate, take evasive action.
Give ’Em the Fingers
The “three-finger rule” says that when an object, such as a lighthouse or tower, appears as tall as three fingers held sideways at arm’s length, it’s about 10 times as far away as it is tall. If the chart says the lighthouse you see is 150 feet tall, when it appears “three fingers” tall you’re about 1,500 feet or a quarter of a nautical mile away from it.
Since sound travels at a known speed, you can tell how far off an object is by timing your echo. Every second of delay equals 200 yards. Use this in fog or at night against cliffs, buildings or even large ships.
Go to the Light
White navigational lights appear first when approaching a shore at night. Red and green lights have about three-quarters of the range of white ones.
Rule of Thumb
Nautical legend has it that the phrase “rule of thumb” came when ship masters never allowed themselves to get closer to an obstacle than the width of their thumb on a chart.
Edge of the Earth
Distances over the water seem greater than on land. When standing eight feet above the waterline, as you might in the cockpit of a cruiser, the horizon is barely 3¼ miles away. At six feet up, it’s only 2½ miles.
A statute mile is the distance a Roman soldier covered in a thousand (mille in Latin) steps, which is now 5,280 feet. By convention, statute miles are used with charts of inland waters and the Intracoastal Waterway. A nautical mile is 6,076 feet, which corresponds to one minute of latitude, and so makes navigation computations easier.
On most planing boats, stow heavy gear to maintain a center of gravity on plane that's about 60 percent of the boat’s waterline length aft of the bow.
Discharge time for the average fire extinguisher. So aim at the base of the fire and get as close in as you can before discharging. Better yet, carry two or three.
Bow and stern lines should be as long as the boat, spring lines 1.25 times the length. This will accommodate even the most extreme tidal ranges.
The eye splices in your dock lines should be at least two feet long to make them easier to place over a piling and to put less strain on the splice.
Allow one inch of cleat horn length for each one-sixteenth inch of rope diameter. This provides enough room for the rope to make a gentle curve without pinching, which weakens the line.
Hey, Big Fender
How big a fender do you need? A good guide is one inch of diameter for every five feet of overall length. A 25-foot boat needs at least a 5-inchdiameter fender.
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The U.S. Coast Guard is asking all boat owners and operators to help reduce fatalities, injuries, property damage, and associated healthcare costs related to recreational boating accidents by taking personal responsibility for their own safety and the safety of their passengers. Essential steps include: wearing a life jacket at all times and requiring passengers to do the same; never boating under the influence (BUI); successfully completing a boating safety course; and getting a Vessel Safety Check (VSC) annually from local U.S. Coast Guard Auxiliary, United States Power Squadrons(r), or your state boating agency's Vessel Examiners. The U.S. Coast Guard reminds all boaters to "Boat Responsibly!" For more tips on boating safety, visit www.uscgboating.org.