Victory Without a Fight

He needed to enter the relevant parameters to calculate the sail angle.

"Wind on the port side, crosswind, speed twelve knots, true wind over the sea twenty-five knots." Su Ming entered each value and had Zijin use the data to direct the zombies in adjusting the sails. "Twenty-six degrees clockwise!"

Zijin did not understand at all. After that adjustment, the sails stood vertically, cutting straight into the wind. Other sailing ships tried to expose as much sail as possible to catch the wind. Su Ming, however, was doing everything he could to reduce the area exposed, letting the sea breeze pass almost straight through the masts!

It was like combing the air with a giant six-toothed comb!

But what baffled her even more was that, unreasonable as it seemed, the Zhiyuan really was picking up speed!

As the ship accelerated, the software prompted him to increase the sail angle further and lower the plate-shaped keels. Zijin directed the zombies to make the adjustments in sequence. Eight enormous, flat keels descended from the hull into the water, providing lateral resistance.

"Speed eighteen knots, apparent wind thirty-one knots!" Su Ming glanced at the readings and made calculations on the sand table.

"We really can catch up to them!" Zijin struggled to accept what was happening. Although the Zhiyuan had reached nearly twenty knots last time, those had been abnormal conditions, and both sides in the battle had known the speed was unsustainable. Now, however, the power unit was operating at only sixty percent, a third of its previous peak output, and the ship had already surpassed that speed!

The Zhiyuan continued to accelerate as Su Ming fine-tuned the sail angles. Gradually, the ship reached twenty knots.

"Could you explain a little?" Zijin could no longer contain her curiosity. "I might not understand, but I really want to know what kind of sorcery this is-how can a ship reach twenty knots in a twenty-five-knot wind?"

According to the conventional understanding of sails, the faster a ship traveled, the smaller the difference between its speed and the wind's, and the weaker the wind's thrust. Even in the current twenty-five-knot gale, for example, the Jade Sea and Tang Valley could manage only twelve knots with the wind at its back.

What was more, the Zhiyuan was sailing in a crosswind, with the sea breeze blowing almost perpendicular to its direction of travel.

So how was it reaching twenty knots in a twenty-five-knot wind? Was it relying on that steam engine, which was barely doing any work?

"This isn't the principle your world's sailing ships use for propulsion," Su Ming explained. "The wind simply passes along both sides of the rigid sail. Because of fluid dynamics, the pressure drops sharply on the curved side, producing a static pressure perpendicular to the sail's surface."

"Static pressure?"

"Mm. The force from this static pressure is much greater than the thrust a sail gets from catching the wind," Su Ming replied. "I'll get you a few books on hydrostatics and the Bernoulli equation to read later."

"...Thanks."

A wing sail was, as its name suggested, configured like an airplane wing on Earth. The only difference was that an airplane wing operated horizontally, while a wing sail stood vertically on the hull. The two worked on the same principle.

But presumably this world had nothing like airplanes either, so Su Ming could not explain how this modern kind of sailing ship worked to Zijin in just a few words.

"I'm not reaching twenty knots in a twenty-five-knot wind," Su Ming said, trying to explain a little more. "The faster the wind moves relative to the sail, the stronger the thrust from static pressure. Add the true wind speed over the sea to the Zhiyuan's speed across the wind, and the apparent wind at the sails has already reached thirty-two knots!"

True wind was the absolute wind speed measured relative to the sea's surface. Apparent wind was the wind speed perceived from the ship, with the ship's own speed added in.

"Okay, you've successfully put me off." The scholar decisively gave up.

Using the time and speed, Su Ming marked their position on the sand table again.

"A distance of 140 kilometers. If the 'onlookers' stay where they are, we'll catch up in a little over three hours." He finished his calculations. Of course, there was no chance the enemy would stay put. "I'm betting they'll run west with the wind."

Zijin looked at the sand table and agreed with his conclusion. If the "onlookers" wanted to move toward the Jade Sea and Tang Valley, they would have to sail into the wind, tacking in a zigzag that required frequent changes of direction. If they managed two knots doing that, their sailors would deserve credit for their dedication.

The scholar did not understand wing sails, but she knew ordinary sails inside out. If those ships also headed southwest, with the wind coming from behind at an angle, they could probably make six to eight knots.

And if they headed west, they would have the most favorable wind angle and could make twelve knots!

Su Ming knew full well that the "onlookers" were south of the Zhiyuan, yet he had still chosen to head southwest in order to flank them along the outside. He was not simply chasing them in a straight line; in this contest, he was blocking their best escape route.

The Zhiyuan was heading toward where they would be positioned later on the timeline.

Nearly an hour after setting sail, the two released the balloon again.

"Use a thicker tether. A height of one thousand meters will be enough," Su Ming told Zijin.

The balloon soon reached the desired altitude, and the radar began scanning.

Everything was exactly as expected. The "onlookers" had chosen to head west at full speed with the wind. They clearly believed the Zhiyuan could not maintain twenty knots, so as long as they held their speed, there was no chance of being caught.

Su Ming made minor adjustments to their pursuit course based on the radar scan.

Over the next two hours, Su Ming maintained a speed of twenty knots. Another radar scan showed that the "onlookers" had adjusted their course and begun heading southward, their speed dropping to ten knots. On the right side of the battlefield, the "carrier battle group" and the "squirrel battle group" had changed course and were moving this way.

But the Zhiyuan was clearly leaving them farther and farther behind. Meanwhile, the distance between it and the "onlookers" had closed to ninety kilometers.

Su Ming calculated how much fuel remained. The steam engine could probably run for a little over four more hours, which left little margin, so there could be no mistakes.

During this time, Su Ming installed the newly acquired X-band radar at the top of the mast. Having done it once before, he knew the ropes. This time, he used the balloon's S-band radar as a reference to initialize and calibrate the marine radar. Once he had calibrated the ship's heading line, the mast radar was finally ready for use.

As soon as it was switched on, a thin line began sweeping in circles across the new circular screen in the control room, scanning the surroundings. The "onlookers" were soon located, 88.2 kilometers away!

Although its advertised operating radius was over a hundred kilometers, Su Ming knew it would come nowhere near that on Earth. Yet in this other world's electromagnetically blank-slate environment, it really did perform exceptionally well! Unfortunately, the item had been "picked up on-site"; otherwise, Su Ming would definitely have given the shop a five-star review and left the comment, "Personally tested-works at 72 nautical miles"!

Zijin, meanwhile, had been inscribing magic arrays on the Zhiyuan in preparation for battle. Seeing the mast radar begin to rotate, she took a look with her omniscient vision.

[This is much more convenient!]

[Its range is shorter, so the two complement each other perfectly.]

Su Ming reduced the X-band radar's scanning interval to five minutes and began correcting their pursuit course.