Jin’s lecture on shipbuilding continued.
“The resistance water exerts on a ship can be categorized into wave-making resistance, viscous frictional resistance, and viscous pressure resistance,” Jin explained. “Think of wave-making resistance as the energy a ship spends just to create waves, while viscous frictional resistance is essentially the water’s stickiness.”
Jin’s knowledge was drawn from hobby magazines he’d read back when he built models; it was somewhat superficial and full of gaps. However, in this world, there was no one else capable of providing such a systematic explanation.
“Viscous pressure resistance is the drag caused by the low-pressure area that forms behind the ship, which tries to pull it back.”
“...?”
Since Jin only half-remembered the details himself, he couldn't elaborate further. Fortunately, his "students" were all practical-minded.
“When you move your hand underwater, if you push with your palm flat, the resistance is high, right? But if you rotate it ninety degrees, the resistance drops.”
This kind of analogy was enough to make them understand.
“Yeah, I think I get it,” Ernest said.
With time running short, Jin pressed on with the lecture.
“As for the ship's stability...”
“The shape of the hull bottom is...”
“The structure of the hull itself is...”
It was all recycled information from his old magazines, but Marcia and Prince Ernest listened with rapt attention. So did Hanna, Elsa, Lishia, and Rodrigo.
“My, Lord Jin’s talk is quite informative,” Rodrigo remarked.
“Onii-chan’s explanation is so easy to understand,” Hanna added.
“It’s been a while since I heard Jin-nii’s technical talks, but I understand ships much better now,” Elsa said.
“I’m glad to hear that, but...”
Jin looked over at the primary student, Prince Ernest, and saw that he was busy scribbling notes onto parchment.
“Jin, that means you have to be extremely careful when building a large ship,” Ernest noted.
“That’s exactly right.”
On this point, Jin, Elsa, and Rodrigo could draw from their experience building the Bernstein back in the Shouro Empire.
“The larger a ship gets, the more the magnitude of the forces acting on various parts of the hull changes. You understand that, right?”
“Yes. It’s the effect of the waves,” Ernest replied.
“The shape of the hull bottom is vital as well.”
In this manner, Jin laid out every basic principle of shipbuilding he could think of.
After about an hour and a half of general theory, he moved to the workshop floor to demonstrate using the actual vessels.
“Look, see how smooth the surface is?”
“Oh, you’re right. That’s to reduce the viscous frictional resistance, isn't it?” Ernest asked.
Ordinary wooden ships generally used rot-resistant wood but lacked any specific surface treatment or preservative coating. Things were different here.
“When wood gets wet and is then exposed to air, mold grows and it rots,” Jin explained.
“Wait, really?”
“It’s true. Though, strangely enough, it won’t rot if it stays completely submerged in water.”
That much was evident from the way sunken shipwrecks often retained their form.
“That’s why we treat the wood so it doesn’t absorb moisture, and then apply a finish to repel the water.”
“That’s even more necessary for a large ship,” Ernest observed.
A large ship represented a massive investment; one couldn't afford to let it rot away.
“As for the specific method... well, that’s Marcia’s own secret technique, so I won't explain that part.”
Ernest laughed and nodded understandingly. “Of course! Everyone should have their own secrets to work on.”
“Catamarans and trimarans are very effective for small boats,” Jin continued, “but for large ships, the strength of the connecting sections becomes a major problem.”
“Ah, because the waves exert different forces on different parts of the hull simultaneously,” Ernest said.
“Precisely.”
It seemed the core of the lecture had been successfully conveyed to the prince.
By this point, Princess Lieschen had clearly reached her limit for technical talk and was chatting idly with Lishia.
Hanna, however, wore a dead-serious expression, determined not to miss a single word of Jin’s explanation. Watching her, the princess looked just a little bit lonely.
＊ ＊ ＊
To wrap things up, everyone was treated to a ride on the boats.
First was the Cygnus, the former champion. It was a tight squeeze, but they managed to fit three people.
“Wow, this feels amazing!”
The Cygnus sped around the bay, the salty breeze whipping against their faces.
“Your Highness, please try to remember this specific swaying, the maneuverability, and the acceleration,” Marcia said to Prince Ernest while running the Cygnus at about eighty percent power.
Next was the recent winner, Bib #6. It didn't seem to have a proper name yet.
“Mmm, I can definitely feel the difference!” Ernest cried.
By moving from a catamaran to a trimaran design, each individual hull was slightly shorter, which improved the turning radius. Furthermore, since the distance between each center of buoyancy was greater, the period of the swaying was longer and more stable.
“The acceleration seems even better too.”
“Yes, that is the effect of the 'horizontal waterwheel'... the screw,” Marcia explained.
“I see. But wouldn't it be bad if algae or seaweed got tangled in there?”
Marcia was genuinely surprised that Prince Ernest had identified the screw's primary weakness so quickly.
“...Yes. That’s why we have to be very careful about where we navigate.”
“With a small boat, you could probably clear it by hand, but I wonder how a large ship would handle it...”
Prince Ernest was already thinking several steps ahead.
＊ ＊ ＊
“Jin, Marcia, Elsa, Hanna, Lishia—thank you all. Reiko-chan, Edgar, Arrow, thank you for taking care of us,” Ernest said.
The time was 11:00 AM. The prince and princess prepared to bid Jin’s group farewell.
“Do not worry, for we shall be escorted back by the Kingdom of Elias,” Princess Lieschen announced with a smile. She then turned her attention to Hanna. “Hanna, stay well. Let us meet again soon.”
“Take care of yourself too, Lies-oneechan!”
Outside Marcia’s workshop, the carriages and guards arranged by Marchioness Firenziano were standing ready.
“Lord of Kunlun, I shall now escort their Highnesses to the capital, Borgia,” the Marchioness informed him.
Jin had considered offering Konron 3 for the journey, but he learned that an airship was scheduled to meet them at the Guest House.
“Well then, we shall take our leave.”
“Jin, see you later!”
“Jin, thanks for everything!”
The Marchioness and the royal pair waved from the carriage windows, and Jin waved back. The carriages slowly lurched forward and began to roll away, eventually vanishing from sight.
“They’re gone,” Marcia murmured.
“Mm,” Elsa agreed.
“It feels a little lonely now,” Hanna said.
“Yeah...” Jin sighed.
“It really does...” Lishia added.
Even the most boisterous times spent with friends must eventually come to an end. Marcia, Elsa, Jin, Hanna, and Lishia each expressed the quiet melancholy of the parting in their own way.