Late Ming sea owl

Chapter 305: Victory of the Reporting Ship
The hydrology at the mouths of large rivers is dynamic, which is reflected not only in the monsoon but also in the tides and runoff.

Winter is the dry season of the Pearl River, when runoff is stable and low, and the effect of ocean tides becomes more significant. Although the Pearl River Estuary is a weak tidal estuary with a maximum tidal range of only more than three meters, winter tides still greatly change the water flow.

Specifically for the Ohori Channel, the normal water flow direction is from northwest to southeast, and the flow rate can exceed three knots when it is high. If the flow rate is against the wind and the current, it is basically difficult for a sailboat to sail.

However, during the winter dry season, the flow rate of the Ohori Channel will decrease, and at high tide it may even change direction, that is, flow from southeast to northwest. The Dangan Channel, which is basically parallel to the Ohori Channel, has a gentler flow in the second half, but that waterway is crossed by dangerous four-foot reefs.

Therefore, if you want to enter the Dahao Channel in winter, tides are an unavoidable problem. The tides at the mouth of the Pearl River are irregular semi-diurnal tides, which in later generations only exist in the coastal areas of Guangdong, the west coast of Taiwan, and the Bohai Bay.

The so-called semi-diurnal tide means that there are two high tides and low tides every day, while the irregular semi-diurnal tide means that the water levels of the two high tides and low tides are inconsistent, and the duration of the high tide and low tide is also inconsistent.

The tidal cycle of the Pearl River Estuary is roughly 12 hours and 24 minutes. Judging from the time of high and low tides, a cycle lasts about 30 days. In other words, the time of high and low tides twice a day will be delayed by 48 minutes compared to the previous day, which is exactly 30 hours in 24 days.

In this 30-day cycle, there are two periodic high tides, namely the new moon day on the first day of the lunar calendar, and the full moon day on the fifteenth day of the lunar calendar, collectively known as the new moon and full moon tides.

The reason why it is in these two days is that the tidal phenomenon is mainly caused by the gravitational force of the moon and the sun. As early as the reign of Emperor Renzong of Song Dynasty, our ancestors had a preliminary understanding of this.

The Xia calendar used in ancient times was mainly based on the changes in the moon. On the first and fifteenth day of every month, the moon was approximately in the same straight line as the sun and the earth. The superposition of gravity would cause a large fluctuation in the sea level.

Due to the inertia and friction of sea water, as well as the influence of the seabed topography and coastline contour, the new and full moon tides often do not occur strictly on the new moon or full moon day, but are delayed for a few days.

Specifically for the Pearl River Estuary, the lunar and full moon tides will be delayed by one and a half days than the theoretical time. That is to say, the nearest high tide will arrive on the second day of March, with the two high tides at 6:48 in the morning and 7:12 in the evening respectively.

On the second day of March, the sky was about to dawn, and the new moon and full moon tides that had started at midnight had been rising for more than two hours. The 20 reporting ships of Huiyou Company lit up their mast lights one after another and sailed out of the home port on the west side of Wai Lingding Island.

This fleet was going to carry out the surprise attack plan that Lin Hai mentioned. Instead of heading north to the eastern entrance of the Dahao Waterway, they headed south back to the Danggan Waterway from which they came.

The fleet formed a column and continued to sail westward along the Dangan Channel, with the ships not following closely but keeping a considerable distance from each other.

The sea breeze at dawn was extremely sweet, and the surprise attack fleet rode the crosswind to reach an ultra-high speed of nearly twelve knots. In just two quarters of an hour, the fleet had arrived at the south of the Zhizhou Islands, about ten kilometers away from the home port of Wai Lingding Island.

At this time, a red sun had already emerged from the water and was immersed in the seawater at the stern. The surprise attack fleet turned off the mast lights and continued to move forward along the Dangan Channel.

To the north of the Zhizhou Islands is the eastern entrance of the Dahao Waterway. The next section of the Dangan Waterway is roughly parallel to the Dahao Waterway, with a series of islands including the Zhizhou Islands, Guishan Island, Zhongxin Island, and Niutou Island in between.

There is a pillow box channel between Guishan Island and Zhizhou Islands, which can connect the Dangan Channel and the Dahao Channel. If the surprise attack fleet does not intend to turn back, this is the last chance to enter the Dahao Channel.

However, the fleet did not turn north in the Zhenxiang Waterway, but continued to sail west along the Dangan Waterway until it reached the southwest side of Guishan Island.

At this time, it was the end of the Mao period and the beginning of the Chen period, and the sea level was at its highest, which also meant that the ebb tide had begun.

The Dangan Channel turns northwest from here, roughly 35° north by west, and the wind direction at this time is 5° north by east. In other words, the fleet can no longer ride on the crosswind, and will have to sail close to the wind, with a windward angle of about 40°, which is the so-called near windward. At this near windward angle, a square-rigged ship cannot sail, even a schooner of this era can hardly sail, and can only take a zigzag route against the wind - in the next section of the Dangan Channel, this is tantamount to suicide, because there are dangerous four-foot reefs!
"Captain, that's the four-foot reef, right?" On the flagship of the surprise attack fleet, the Lubode, Captain Wei Xiaodong and his personal soldiers were standing on the deck at the bow, looking out at the reef on the sea in the northwest direction.

"It should be." Wei Xiaodong's answer was very calm, but in fact his heart was already in his throat.

He remembered what Lin Hai had said to him and all the captains of the reporting ships: "As a captain, the most important thing is to stay calm at all times! Please remember that your tone and expression will be contagious to everyone on the ship."

The captains of the reporting ships are all young members of the Navy Department. They have relatively little experience and each of them was selected by Lin Hai himself. They have reached this position based on their own abilities and drive.

Wei Xiaodong is one of the best captains of the warship. He is only 25 years old this year and stood out from the earliest batch of sailors who participated in Western-style sailing training.

He just glanced at the four-foot reef, then turned around to watch the sailors operating the sails - the Lubod was adjusting its course.

Under the command of the boatswain, the sailors on the deck are using the sailing pole to adjust the angle of the mainsail. To sail close to the wind, the sail must be kept in the middle of the angle between the wind direction and the heading. This is actually a universal rule, and it is the same for sailboats sailing in any wind direction.

At the same time, in the wheelhouse that Wei Xiaodong could not see, the helmsman was turning the steering wheel and coordinating with the sail handling operation.

Finally, the course of the Lubode was basically stabilized - it did not zigzag, but moved straight forward at an angle close to 40° to the wind!
Wei Xiaodong smiled towards the rising sun. He prayed silently in his heart that the wind direction would not change, especially not to turn counterclockwise...

"Captain, how big is the Four-Foot Rock?" The soldier was still staring at the reef in the distance. The Lubode was still ten kilometers away from the Four-Foot Rock, but it could be seen without a telescope.

"I don't know, maybe just four feet." Wei Xiaodong didn't look back, still with a smile on his face. This was naturally a joke.

The Four-foot Rock is of course more than four feet. The reason why this reef is dangerous is that it is too big. Under normal water levels, the part of it that is exposed above the water is several thousand square meters, and the depth of the underwater part is unknown. No one knows how far away from it is safe enough.

However, the Dangan waterway is not very wide in this section. If a ship gets too close to Niutou Island, it is very likely to run aground.

What's more, if the wind direction does not deviate to the clockwise direction, the Rubber will not be able to get closer to the direction of Niutou Island - 40° is already the limit of the windward angle of the reporting ship. Next, it can only move straight into the wind, or move towards the direction of the four-foot reef!
The water level was still high at this time, but the ebb tide had already begun. The surprise attack fleet was sailing against the wind and the current, and could only run at a speed of more than three knots.

The 20 reporting ships were like a team of knights in cloaks, rushing towards an unknown fate against the howling north wind.

An hour later, the Lubode successfully left the four-foot rock behind, followed closely by the Yangpu...

In the end, the surprise attack fleet successfully sailed out of the danger zone at the cost of three ships running aground and two ships running aground - the remaining fleet still had 15 ships and 120 guns!

"Captain, we won!" Wei Xiaodong's personal soldiers were so excited that they burst into tears. This was an outstanding surprise attack, and its thrilling level was comparable to Deng Ai's sneak crossing of the Yinping Mountain Road during the Three Kingdoms period.

(End of this chapter)