Sailing Navigation Safety - What is 'Safe Speed'?

by John Jamieson on 14 Oct 2013 Could you be sailing too fast in some conditions? After all, it's rare that a cruising monohull sailing boat's speed can come close to that of her powerboat cousin.

But the International Rules for Prevention of Collisions at Sea -- written to help vessels avoid collisions in all waters -- do require skippers to regulate speed based on visibility, environment, and your ability to maneuver your vessel with control. Use these five vital 'speed' tips for safer sailing worldwide:

1. Visibility Conditions at Your Location
Fog comes to mind right away. But so do rain showers, squalls, heavy weather with blowing spray, dust storms, or even night time. Night time? Our perception decreases after sunset, as does our ability to see unlighted or dimly lighted objects. Studies show that we are often most sluggish in the wee hours of the new day (around 0200 or 0300 in the morning).

So, it makes good 'sea sense' to reef at night and carry a smaller headsail. Big Genoas can block visibility and turn into a handful if a squall comes up. Keep speed down at night time for easier sail handling and less stress all around for skipper and crew.

2. Traffic Density Where You Are Sailing
Does your sailing route take you close to or near an area frequented by commercial fishing vessels or anchored small boats? Will you sail near traffic lanes or traffic zones? Sail clear to avoid the risk of collision.

Navigation Rule 9 cautions sailing vessels or vessels less than 20 meters (65.6 feet) not to block or hamper boats or ships in narrow channels or waterways. Just another good reason to 'stay clear to stay safe'.

3. Your Vessel's Ability to Maneuver, Stop or Turn
You may have heard the old recommendation to never proceed faster than the speed in which you can bring your vessel to a complete stop in one half the present visibility. That might seem silly for small boats, and indeed it applies more to big ships, but it does make good 'sea sense'.

If in a blinding squall, lower your speed to the minimum or stop the boat. The wisest move may be to heave to and wait it out. Fast moving squalls rarely last longer than a half hour or so. And, if you stop or slow your boat, the weather system will pass by faster than if you tried to run before it.

In the Coast Guard, we sometimes encountered vicious squalls that lowered visibility to the point to where our bow was invisible. The radar could become so cluttered with rain and sea return, that our ability to pick up a vessel by radar would be next to impossible. We would back off the throttles to give us just enough speed to maintain steerage.

As a matter of fact, the single factor of safe speed played a crucial role time and again in saving lives when I was in the US Coast Guard. Read this true sea tale from the Caribbean long ago...

Slow Speed Saves Lives in Operation 'Able Vigil'

In the early 90's Cuba's Fidel Castro opened a narrow 'window of opportunity' to allow citizens to take to the sea in tiny rafts or boats to head to the US. Many of these craft were unseaworthy with just a few inches of freeboard. They were overcrowded and often in danger of capsizing. Many had no lights and were too small and low to the water to be picked up by radar.

Our mission was to rescue them as soon as they entered International waters. At nighttime the difficulty of rescue increased exponentially. We slowed our speed to a crawl and stationed lookouts forward and aft. And they looked and listened. We often never saw them--but heard them!

If you recall, listening is mandated by Rule 5 in the Navigation Rules. And it worked. We would pick up voices of the people in their tiny rafts before they were sighted at all. The result? Not one casualty or fatality from collision. This combined Coast Guard/Navy effort rescued over 30,000 people in one of the most successful peacetime rescue operations in US history.

4. Nighttime Background Lights
Imagine a chameleon that rests atop a huge green leaf. That reptile will turn green like the leaf to become next to invisible. The same can happen at nighttime when you sail in areas with lots of city lights. New York city can be a magical place to sail through at night, but small boat navigation lights will be next to impossible to spot if superimposed with the bright lights of the shoreline.

Consider what the other guy or gal sees from their boat. Pretend that you can beam aboard their boat and look back at your boat. Will you, too, be invisible in the background scatter of lights. Slow down if necessary and increase visual scans when lots of lights are present at night.

5. Your Draft Relative to Water Depth
Power vessels that travel at high speed in shallow water can experience 'stern squat'. In water depths of about 2X or less draft, the stern of the boat will drop toward the bottom. This makes the rudder and propeller inefficient and steering sluggish. Small sailboats may experience a similar condition when water depth approaches 2X the draft of your boat. For example, with a 3 foot draft, you should slow down in water depths of 6 feet or less water depth to maintain positive rudder and propeller performance.

The Rules carry this requirement because you need both of these apertures to give maximum efficiency to avoid collision. Check the water depth of any shallow area you plan to transit and adjust your speed. If your rudder or propeller feel sluggish, slow down to regain control.

You can read more about safe speed and additional hints for vessels equipped with radar in internationally accepted Rule 6 of the Navigation Rules. Click here to download the Navigation Rules to your computer or mobile device now. See Rule 6 for the complete list of 'safe speed' factors that will help you stay safe on the waters of the world. The rule in the link is courtesy of the US Coast Guard, but is standard internationally for all waters and oceans.

Follow the above five sailing tips to increase sailing and cruising safety. This will keep you and your sailing crew or partner safe--wherever you choose to sail or cruise!

John Jamieson (Captain John) with 25+ years of experience shows you the no-nonsense cruising skills you need for safer sailing worldwide. Visit his website at www.skippertips.com. Sign up for the Free, highly popular weekly 'Captain John's Sailing Tip-of-the-Week'. Discover how you can gain instant access to hundreds of sailing articles, videos, and e-Books!