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The Rules of the Road – Safe Speed and Boat Handling Skills

Source: Mariners Learning System, by Captain Bob Figular

The Navigational Rules of the Road (Rule 6) states that you to the need to set a safe speed in all conditions of visibility. This obviously does not mean the same “safe speed” applies in good as well as restricted visibility. The first requirement of this rule is to consider what the state of visibility is because safe speed in any condition must be closely related to the immediate circumstances and conditions at hand. A boat at high speed has a large amount of force. With an untrained operator, this force can be dangerous.

The following different factors should be considered to determine safe speed:

Heavy seas: Slow down as winds and seas increase; the boat will handle more easily. Pounding or becoming airborne fatigues the hull and could injure your crew or cause them chronic body aches and pains.

Traffic density: Do not use high speed in high traffic density areas. A safe speed allows response to developing situations and minimizes risk of collision, not only with the nearest approaching vessel, but with others around it.

Visibility: If conditions make it difficult to see, slow down. Fog, rain, and snow are obvious limits to visibility, but there are others. Visible features and obstructions (river bends, piers, bridges and causeways), along with heavy vessel traffic, can limit the view of “the big picture.” Darkness or steering directly into the sun lessens ability to see objects or judge distances. Prevent spray on the windscreen (particularly salt spray or freezing spray) as much as possible and clean it regularly. Spray build-up on the windscreen is particularly hazardous in darkness or when you experience glare.

Besides Heavy Seas, Traffic Density, and Visibility there are additional external factors that will have an effect your vessels ability of running at a safe speed.

In shallow water, the bottom has an effect on the movement of the vessel. Slow down in shallow water. In extremely shallow water, the vessel’s stern tends to “squat” and actually moves closer to the bottom.

In narrow channels and canals, a vessel moving through the water will cause the “wedge” of water between the bow and the nearer bank to build up higher than on the other side. This bank cushion tends to push the bow away from the edge of the channel.

As the stern moves along, screw suction and the movement of water to “fill-in” where the boat was creates bank suction. This causes the stern to move towards the bank. The combined effect of momentary bank cushion and bank suction may cause a sudden shear toward the opposite bank. Bank cushion and bank suction are strongest when the bank of a channel is steep. They are weakest when the edge of the channel shoals gradually and extends in a large shallow area. When possible, it is best to operate your vessel in the center of an extremely narrow channel to avoid these forces. Slower speed also reduces the amount of cushion and suction. Some rudder offset towards the closer bank will help to avoid continuous cushion and suction effects by.

When meeting another vessel close aboard, bow cushion and stern suction occur between the vessels much the same as bank cushion and suction. Helm corrections should be used to compensate. As both vessels move through the water, the combined effect is greater than what a single vessel encounters from bank interaction. Caution should be used so the bow does not veer too far from the intended track and the stern swings into the path of the other vessel.

Before vessels are bow-to-bow, a small amount of right rudder should be used to ensure the bow is clear. The bow cushion will increase separation. As the vessels near bow-to-beam, using left rudder will enable the vessel to keep away from the right-hand bank and to stay parallel to the channel. When the vessels are bow-to-quarter, the bow cushion will be offset by the stern suction, and bank cushion may need to be offset by some right rudder. Finally, as the vessels are quarter-to-quarter, stern suction will predominate, and will require left rudder to keep the sterns apart.

When meeting another vessel in a narrow channel or operating near a bank the following bow cushion and stern suction considerations apply:

  • The deeper your vessel’s draft, the greater the cushion and suction effect, particularly if your boats draft is nearly the same as the depth of the waters you are operating in.
  • The closer to a bank or another vessel, the greater the cushion and suction will affect your boat.
  • In very narrow waterways, slow down to decrease cushion and suction effects, but not slow your vessel to the point of losing your ability to maintain bare steerage.

When meeting another vessel in a narrow channel, the bow cushion and stern suction effects caused by the other vessel should be balanced with the bank cushion and suction effects due to the channel.

As your boat moves forward a combination of bow and stern waves move outward at an angle to the vessel track. The wake height and speed depend on vessel speed and hull type. Relatively large, semi-displacement hulls, proceeding at cruising speed, cause some of the largest wakes. Some lighter craft actually create a smaller wake at top speed while operating in the planing mode rather than at a slower speed. Displacement boats make the largest wake at hull speed. As the helmsperson you should learn how to operate your boat so that it leaves the least wake possible when operating in close quarters or around small vessels. This may require slowing your vessel appreciably to ensure safe operation.

All vessels are responsible for their wake and any injury or damage it might cause. Only a poorly trained or ignorant boat operator trails a large wake through a mooring area or shallows, tossing vessels and straining moorings. A large, unnecessary wake, particularly in enclosed waters or near other smaller vessels, is unnecessary and can cause damage or injure others.

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