Are You “NavRules Legal” Under Sail and Power?

Captain John from gives a colregs refresher on the required dayshapes you need while under sail or power.

Did you realize that the Navigation Rules (sometimes called the “NavRules”) require that you hoist day shapes in certain situations. Now, I’m not here to tell you what to do, but to share with you what the Navigation Rules say we are required to do in certain situations.

After all, those Rules were written for one purpose–to prevent collisions. Are you sure that you are in compliance in the US Inland waters or in International waters? Check this little-known Rule to find out!

Turn to Rule 3, General Definitions, in the Navigation Rules (both International and Inland) to understand how the Rules define different types of vessels. Sailboats can be “sailing vessels” or “power-driven vessels” at any given time. How do you know which you are? Read this excerpt from Rule 3:

Rule 3 General Definitions (b)The term “power-driven vessel” means any vessel propelled by machinery. (c)The term “sailing vessel” means any vessel under sail provided that propelling machinery, if fitted, is not being used.

What Does a Dayshape Tell Others About You?

Navigation dayshapes are similar to navigation lights. They can tell other vessels what type of work you are doing or how maneuverable you are (i.e. diving, dredging, laying underwater pipeline, fishing (except with trolling lines), trawling, towing, broken down, restricted in maneuverability, aground, anchored, motor-sailing, etc…). That way, other vessels near you will know how to maneuver in order to avoid collision or danger.

The Rules state that dayshapes shall “be complied with” (used in accordance with the Rules) by day, in all weathers, and must be of a certain color and shape (Rule 20(d) and Annex I, paragraph 6). Each Rule specifies where on the vessel the specific dayshape should be carried.

For example…

Have you passed by a large ship at anchor with a black ball hoisted high above her deck? The anchor ball dayshape must be hoisted by day, in all weather conditions, in the forward part of the vessel, and be black in color and of a certain size (minimum sizes are specified for vessels 20 meters (65.6 feet) or more in length (Annex I, paragraph 6). Some smaller vessels or vessels anchored in certain areas may not be required to show the anchor ball dayshape (see Rule 30 for more on this).

Vessels Proceeding Under Sail and Power

Sailboats are often required to carry dayshapes when being propelled by sail and power. You are now a power-driven vessel, and must make that clear to those around you. In International waters–or those waters seaward of the Demarcation lines, you must carry a cone with the point downward hoisted in the rigging.

In Inland waters–or those waters of the U.S. shoreward of the Demarcation lines, only sailboats 12 meters (39.4 feet) or more in length have this requirement. That’s not to say smaller sailboats could not do so, but they are not required to do so.

So how can we verify whether or not we must hoist this dayshape when we are motor-sailing? Let’s look at Rule 25(e) for the answer. Throughout the NavRules, if a Rule says “shall”, that means we are required to comply with that specific Rule or that specific part of the Rule. If it says “may”, that means we have a choice. These two words–”shall” or “may”–can make a whale of a difference in any Rule!

International – Rule 25(e) (e) A vessel proceeding under sail when also being propelled by machinery shall exhibit forward where it can best be seen a conical shape, apex downwards.

Inland – Rule 25(e) (e) A vessel proceeding under sail when also being propelled by machinery shall exhibit forward where it can best be seen a conical shape, apex downward. A vessel of less than 12 meters in length is not required to exhibit this shape, but may do so.

As you can see, just those vessels in Inland Waters less than 12 meters have an option. All others are required to hoist the dayshape when proceeding under sail and being propelled by the engine.

What Does the Other Skipper See?

Consider what the skipper on a power boat might assume if he or she sees you under sail. Pretend that you can “beam yourself aboard” a powerboat like the crew on those old Star Trek reruns. Now look back at your sailboat under sail and power and what do you see? Sails are up, so it seems to be a “sailing vessel”–but then again–maybe not!

After all, you might not see exhaust water flow from the sailboat’s stern tube. So how do you know whether to give way to this sailboat or not? If you do not see a black cone with the point downward, this vessel has status as a “sailing vessel”. If you see a black cone with the point downward, this vessel has status as a “power-driven vessel”. And that means she must maneuver in accordance with the Rules for “power-driven vessels”.

Match the Dayshape Dimension to Your Sailboat Size

Annex I of the Navigation Rules gives detailed information about color and sizes of dayshapes (and many other specifications on technical details on navigation lights). Annex I, paragraph 6(a) and 6(a)(ii) states that a cone dayshape must be…

- Black in color.

- Have a base diameter of at least 0.6 meters.

- Have a height equal to that of the base diameter.

Important Note for Smaller Sailboats! A vessel less than 20 meters (65.6 feet) does not need to carry a shape of these dimensions, but the shape should be proportioned (the Rules use the term “commensurate“) to the size of the vessel.(see Annex I, paragraph 6(c)).

Use these sailing tips to determine when you need to carry those dayshapes required by the Navigation Rules for safety and to help prevent collisions at sea. Keep your sailing crew and sailboat safe and sound on the waters of the world–wherever in the world you choose to cruise!

Courtesy of

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