A change of speed

MIKE WHITEHEAD

Ahoy.

I always find it comforting when I cross over the international

border back into U.S. waters when I am coming uphill aboard a yacht

from Mexico. This week I have crossed the border twice out in the

Pacific, once last Sunday and then again Wednesday. I traveled south

of the border twice to deliver both of these yachts to Newport

Harbor, and on both days I had a brief stop for U.S. Customs in San

Diego.

Sunday’s cruise up the coast was a little rough below the Coronado

Islands. In contrast, we found flat seas for Wednesday’s voyage. The

flat seas are great to run in, and you save traveling time with flat

seas.

A few factors contribute to saving time, but the primary factor is

that your overall traveling distance is less in flat seas. When

swells build, so does your overall traveling distance. You can

imagine a sine wave and how it curves up and down and up and down.

Try this experiment: First, cut a piece of string exactly 12

inches long and lay the string next to the ruler. Now, keep one end

of the string at the ruler’s zero mark and make uniform waves in the

string. Now, you will see that the 12-inch piece of string is

measuring less than 12 inches on the ruler, and the larger the curves

the less it extends on the ruler. Therefore, you now need a longer

piece of string with the waves to reach the ruler’s 12-inch mark.

Just as true, your travel distance on the water by boat will increase

as the swell heights increase, but the actual distance between the

two points remains the same.

Why is this important? Have you ever heard boaters who have made

that trip before and now they are out of fuel, or how about the

boater who arrives hours overdue? Sea conditions, wind conditions and

the speed over ground are all factors in planning your next voyage.

Keep in mind that speed through the water is not the same as speed

over ground.

Back to our 12-inch piece of string. If you are traveling at 12

inches per hour along the string, then in one hour you would travel

the length of the string. If the string is flat, then you will travel

12 inches along the ruler.

However, if the string has waves and ends at 8 inches, you will

travel an overall distance of only 8 inches in one hour. Cruising

along the string is comparable to speed through the water. In the

first scenario, when the string is flat, the speed through the water

and speed over ground will match, calculating to 12 inches per hour.

Not so in the second scenario. Your speed through the water (along

the string) is 12 inches per hour but your speed over ground (along

the ruler) is only 8 inches per hour. This means you will need 1 1/2

hours to travel the ruler distance of 12 inches.

Time for your test: Is the distance approximately 26.6 nautical

miles from the end of Newport Harbor jetties to Avalon Harbor on

Santa Catalina Island? The answer is yes because the actual distance

as the crow flies between the two points do not change. Only your

overall traveling distance through the water will change when the

swells increase in height.

Keep this experiment in mind for your next voyage, or at least be

sure to have paid your BoatUS/Vessel Assist membership.

TIP OF THE WEEK

Tonight is the Lido Isle Yacht Club’s Nautical Lecture Series

where I will be speaking about the importance of boating to the

Newport Harbor area. Plus, I will share some of my more memorable

cruising adventures along the Pacific coast. For more information

about this event, contact Dick Brown at (949) 675-5404.

Tune in to my “Boathouse Radio Show” every Saturday from noon to 1

p.m. on KCBQ-AM (1170). You can join in during the nation’s No. 1

boating talk radio show by calling the listener line at (888)

344-1170, and you can listen worldwide over the Internet at

https://www.boat houseradio.com.

Safe Voyages.

* MIKE WHITEHEAD is the Pilot’s boating and harbor columnist. Send

him your harbor and marine-related thoughts and story suggestions by

e-mail to [email protected] or visit https://www.boathousetv.com.