Otherworld Bone Dragon Operation Guide

Chapter 36 Victory without a fight
Zijin didn't understand at all, because after this adjustment, the sail was completely vertical, pointing directly in the direction of the wind. Other sailboats maximize their surface area exposed to the wind to catch it. Su Ming, however, was doing everything he could to compress the sail's surface area exposed to the wind, allowing the sea breeze to pass almost directly through the mast!

It's like using a giant six-toothed comb to comb through the air!

But what baffled her even more was that despite this illogical approach, the Zhiyuan was actually getting faster and faster!
As speed increased, the software prompted to further increase the sail angle and simultaneously instructed the lowering of the side spruce-downs. Violet directed the zombies to adjust in sequence, and four massive spruce-downs were inserted into the water from the hull, providing lateral resistance.

"Speed ​​18 knots, wind speed 31 knots!" Su Ming glanced at it and calculated on the sand table.

"We can actually catch up with them!" Violet tried to accept the situation. Although the Zhiyuan had reached speeds of nearly 20 knots last time, that was an abnormal state, and both sides knew it was unsustainable. Now, with the engine running at only 60% capacity, just one-third of the previous peak, the speed had already exceeded that!
The Zhiyuan continued to increase its speed, and Su Ming made minor adjustments to the angle of the sails. Gradually, the ship reached a speed of 20 knots.

“Let me explain it to you briefly.” Violet couldn’t contain her curiosity any longer. “I may not understand, but I really want to know what kind of witchcraft this is—how can a ship travel at 20 knots with a wind speed of 25 knots!”

According to traditional sailing theory, the faster the boat's speed, the smaller the speed difference between the boat and the wind, and the lower the wind's thrust. For example, in a strong wind of 25 knots, the Biyugu, sailing with the wind at its back, can only reach 12 knots.

Moreover, the Zhiyuan was sailing across the wind, with the sea breeze almost perpendicular to the direction of the ship's movement.

So how did it manage to run at 20 knots in a 25-knot wind? Was it just because of that slow-moving steam engine?
“This is not the propulsion principle of sailboats in your world,” Su Ming explained. “The wind simply passes through the left and right sides of the rigid sail. Due to fluid dynamics, the pressure drops sharply on the curved side, resulting in a static pressure perpendicular to the sail surface.”

"Static pressure?"

“Yes, the force of this static pressure is much greater than the thrust of a sail carrying the wind,” Su Ming replied. “I’ll get you some books on fluid dynamics and Bernoulli’s equations to look at later.”

"……Thank you."

A wing sail, as its name suggests, is the configuration of an airplane wing on Earth. The only difference is that an airplane wing operates horizontally, while a wing sail is inserted vertically into the hull; the two are equivalent in principle.

But presumably, there are no airplanes in this world, so Su Ming couldn't explain the mechanism of this modern sailboat to Zi Jin with just a few words.

"I didn't achieve a speed of 20 knots in a wind of 25 knots," Su Ming tried to explain further. "The faster the wind is relative to the sail, the stronger the hydrostatic thrust. Right now, the actual wind speed at sea, combined with the Zhiyuan's lateral movement, means the sail's apparent wind speed has reached 32 knots!"

True wind is the absolute wind speed with the sea surface as a reference point, while perceived wind is the wind speed perceived from the ship's perspective, plus the ship's own speed.

"Okay, you've successfully persuaded me to give up." The scholar decisively gave up.

Based on the time and speed of travel, Su Ming remarked his position on the sand table.

“It’s a distance of 140 kilometers. If the ‘onlookers’ stay put, we can catch up in just over three hours,” he calculated. Of course, it was impossible for the enemy to stay put. “I bet they’ll choose to flee westward with the wind.”

Zijin looked at the sand table and agreed with the conclusion. If the "onlookers" wanted to approach the Azure Sea Valley, they would need to sail against the wind, adopting a zigzag course that required frequent changes of direction. At that speed, they could only manage two knots; their sailors would be quite dedicated.

She didn't understand wing sails, but she knew all about ordinary sails. If they chose to face southwest, that is, with the tailwind, these boats could probably reach a speed of 6 to 8 knots. But if they chose to face west, that would be the most comfortable angle with the wind, and they could reach 12 knots!
Su Mingming knew that the "onlookers" were located slightly south of the Zhiyuan, yet he still chose to head southwest, intending to encircle them from the outside. He wasn't simply pursuing them in a straight line; he was blocking their best escape route in a strategic maneuver.

The Zhiyuan points to the future distribution on the timeline.

Nearly an hour after takeoff, the two released the balloons again.

“We’ll thicken the cable; a height of 1000 meters will be enough,” Su Ming said to Zi Jin.

The balloon quickly reached altitude, and the radar began scanning.

Everything went exactly as expected; the "onlookers" chose to sail west at full speed with the wind. They clearly believed that the Zhiyuan's 20-knot speed was unsustainable, so as long as they maintained their speed, there was no chance of being overtaken.

Based on the radar scan results, Su Ming made minor adjustments to the pursuit direction.

For the next two hours, Su Ming maintained a speed of 20 knots. Another radar scan showed that the "spectators" had adjusted their course, shifting southwards and reducing their speed to 10 knots. On the right side of the battlefield, the "carrier battle group" and the "squirrel battle group" also adjusted their course, moving towards this side.

However, it is clear that they are being left further and further behind by the Zhiyuan. The distance between the "onlookers" and the Zhiyuan has been reduced to 90 kilometers.

Su Ming calculated the remaining fuel and estimated that the steam engine could run for about four more hours, which was a bit of a stretch, so there was no room for error.

During this time, Su Ming installed the newly acquired X-band radar at the top of the mast. Practice makes perfect, and this time he used the balloon's S-band radar as a reference to initialize and calibrate the ship's radar. After calibrating the bow line, the mast radar was finally ready for use.

As the system was officially powered on, a thin line began scanning the surroundings in a circle on the newly added circular screen in the control room. The location of the "onlookers" was quickly found: 88.2 kilometers away!

Although it boasts a working radius of over a hundred kilometers, Su Ming knew that was far beyond what could be achieved on Earth. However, in this alien world's blank electromagnetic environment, it actually performed exceptionally well! It was a pity this thing was "pick up on-site," otherwise Su Ming would definitely have given the shop a five-star review and left a comment: "Tested and working within 72 nautical miles!"
Meanwhile, Zi Jin had been inscribing magic arrays on the Zhiyuan, preparing for battle. Seeing the mast radar begin to rotate, she used her omniscient vision to take a look.

This is so much more convenient!

[Their areas are relatively close, which complements each other perfectly.]

Su Ming reduced the X-band radar's scanning cycle to 5 minutes and began to correct the pursuit course.

****
On the radar, Su Ming clearly saw the "onlookers" frantically changing direction, trying to escape.

They initially veered southwest, reducing their speed to 7 knots, and then attempted to escape at a 60-degree angle of attack towards the southwest. Su Ming didn't tolerate this, keeping his course directly pointed towards them, openly telling them that he could see them at any time!
(End of this chapter)