"If I remember right, the resistances acting on a ship are wave-making resistance, pressure resistance, and frictional resistance, aren't they...?"
To be precise, they were wave-making resistance, viscous pressure resistance, and viscous frictional resistance.
"You told me about wave-making resistance a long time ago, Jin."
Wave-making resistance was the energy lost from the waves generated as a hull pushed through the water, increasing proportionally with the square of the ship's speed.
Fluid dynamics existed to predict and calculate these forces, but unfortunately, it was a subject first taught at science and engineering universities, so Jin lacked an in-depth understanding.
Be that as it may, the "current" Jin figured that the Jin of four hundred years ago probably hadn't disclosed everything he knew about ships.
And that was only natural. After all, when you had limitless power at your disposal, minor inefficiencies hardly mattered.
The same held true for ships.
"Yeah. Aside from that, there's pressure resistance and frictional resistance."
"I think I get the gist of pressure resistance. It's the drag from taking the water head-on, right?"
"Well, you could put it that way... More accurately, it seems you get pulled back by the negative pressure from things like the eddies that form in the ship's wake."
"Ah, I see!"
Having conducted countless submerged tests, Marcia grasped Jin's explanation right away.
"Then there's frictional resistance. You'll probably understand this best if you picture the water as a much more viscous liquid."
"Ah, got it. That makes sense."
"I'm guessing your experiments already factor in wave-making resistance and pressure resistance. But you've probably overlooked frictional resistance."
Hearing his explanation, it felt as though the scales had fallen from Marcia's eyes.
"For what it's worth, I use Surface Treatment on the exterior of my ships to drop the coefficient of friction as much as possible."
Regardless of testing, lower friction was simply always better.
"I see! So that's another reason your ships are so incredible, Jin!"
Convinced, Marcia's face lit up with satisfaction.
"Yeah. And in an emergency, I also deploy a water-warding barrier."
Since that prevented the hull from ever making direct contact with the water, frictional resistance became negligible, and because wave-making resistance and pressure resistance vanished as well, the ship could reach blistering speeds.
"Right... Waves might still form, but since it's the barrier making them rather than the ship itself, the ship doesn't lose any of its own thrust."
"That's exactly it."
"Yeah, your ships really are in a league of their own, Jin. It's totally cheating. Completely absurd, even."
"Hey, now."
"Haha, just kidding. But I want to find a way to pull it off without relying on tricks like that."
Jin assured her that he understood completely, validating her point.
"Most of what I've made up to now came from necessity. But when it's purely for the love of the craft, I think it's great to push things as far as they can go, just like you're doing, Marcia."
There were very few things Jin had crafted purely as a hobby. Whether it was Reiko, the golems, or the aircraft, ships, and spaceships... nearly all of them had been created to protect a peaceful way of life.
At best, there was only the wooden boat Shark, which he had built under deliberate constraints.
"Well then, time to get back to the experiments."
Having caught her breath, Marcia stood up. Jin rose to his feet as well.
"Good luck out there."
"Thanks, you bet!"
With that, Jin and Mini-Reiko made their way back to the laboratory.
"Father, speaking of making things, I hear Stearena-san has started working on something new."
"Oh?"
His curiosity piqued by Mini-Reiko's comment, Jin decided to stop by Stearena's workshop.
"Whoa."
The room was bathed in a verdant glow—the vibrant green of fresh grass.
"Is that... olivine, perhaps?" Mini-Reiko murmured from her perch on Jin's shoulder.
Olivine was a volcanic mineral.
Among its varieties, forsterite possessed a fresh grassy or green-apple hue, commonly known as peridot or olivine.
The name "olivine" was said to have come from the color of olives.
As a volcanic mineral, it was mined in substantial quantities on Hourai Island.
As a brief aside, Perido, one of the Five-Color Golem Maids, had been named after it on account of her green eyes.
"Oh, Jin-kun."
Stearena, who had been engrossed in her work, looked up and noticed him.
"Are you building a golem?"
"Yes. As you can see, this time I'm making a green peridot golem."
How typical of Stearena, Jin thought with a smile.
In the past, she had crafted a crystal golem out of transparent rock crystal, as well as a topaz golem from blue topaz.
Now, she was taking on a peridot golem.
"Magi-craft really is convenient, isn't it? A peridot this massive could never exist in nature, after all."
Because peridot formed in the upper layers of magma where cooling happened relatively quickly, large crystals were virtually nonexistent, leaving mostly small grains.
To overcome this, Stearena had used the magi-craft spells Fusion and Homogenize to synthesize a single, massive peridot, which she was now shaping into a golem.
"This is gorgeous, too..."
Stearena's sculptural work was always magnificent, but Jin felt this golem was no exception—in fact, it was easily her finest piece yet.
"Thank you. I'll have it finished by dinner tonight, so I can show it off to everyone."
"I'll look forward to it."
Figuring it would be distracting to watch her work for too long, Jin excused himself and left the workshop.
"Do you think this is because you made Jackie, Father?"
Jin had returned to the House and was having lunch.
Incidentally, the members of the Jin Family were each making and eating their own meals today, leaving him alone with Elsa—along with Mini-Reiko, of course.
"Mm. Rai-nii seems to be thinking about making a new Schwarzritter or a next-generation Neon, too."
"Knowing Reinhard, that sounds about right..."
When Jin wondered aloud whether anyone else was working on a project, Mini-Reiko spoke up.
"It isn't physical crafting, but Saki-san is conducting some research."
"Saki is, huh...?"
Well, she was originally an alchemist—which is to say, a chemist—so it makes sense, Jin thought with a nod.
"Also, Beena is making something, too."
"Is she?"
Beena was a magi craftsman from the commoner faction who had once been known as the Magi Craft Queen, so it was hardly surprising that she had started up a project of her own.
"Are you planning to make anything, Elsa?"
Her former servant, Edgar, was currently serving Shu Nidou.
"No, I'm fine."
Elsa replied that she had no particular desire to build anything.
Then she added:
"I want... to research Healing and plant magic."