Though built for experimentation, the vessel Jin had crafted was, for all intents and purposes, a small prototype ship.
"Ooh! This is so comfortable!"
Marcia zoomed back and forth across the Erme River, clearly in high spirits.
"Oh, the stability seems excellent," Rodrigo noted, watching with a satisfied expression.
Jin observed the scene, noting that dividing the hull into three sections had certainly been the right move. With one hull in the front and two in the rear, the ship naturally stabilized its bow against the current when traveling upstream. When heading downstream, the relative velocity against the water was lower, making stability less of an issue.
"I think it would be better to make the rudder a bit larger," Marcia called out.
As she tested the craft at various speeds, navigating up and down the river, she began to identify points for improvement.
"Also, it would be great if it had a tighter turning radius..."
She was considering how much easier it would be if the boat could change direction quickly, even in the narrowest parts of the river. This was particularly important given that the final version would likely have a larger hull.
There were a few other minor adjustments to consider, but those two were the primary ones.
"Wow, that looks like so much fun!"
Watching Marcia's trial run, the younger girls of Kaina Village—ranging in age from about ten to fifteen—cried out in envy.
Come to think of it, Kaina Village has golem horses for the land and occasionally an airship in the sky, but they don't have any boats.
As he watched the girls staring longingly at the vessel, Jin felt a plan starting to take shape.
＊ ＊ ＊
"On that note, I'd like to place an order with the Marcia Workshop as well," Jin announced when Marcia finally brought the experimental ship back to shore just before noon.
"I'm not quite sure what you mean by 'on that note,' but sure, no problem."
Marcia accepted without a second thought. Since the boat would be used on the same river, building them simultaneously would save a considerable amount of effort. More importantly, it was a request from Jin. Once she heard it was because the village girls wanted to ride one, she was even more eager to help.
"I want as many people as possible to know the joy of being on the water," Marcia said with a laugh.
Looking at her, Tiberio remarked, "You really do love ships, don't you, Marcia-san?"
"Of course! I've been on them since I was a little girl."
Marcia replied with a radiant smile, and Tiberio narrowed his eyes as he watched her, as if looking at something dazzling.
"Well, let's break for lunch," Jin suggested to the group.
It was already past 11:30 AM. Having been active since the early morning, everyone was starting to get hungry, and no one voiced any objections.
"Ooh! What is this!?" Tiberio asked, his voice full of curiosity.
"It's suiton," Jin replied.
Back when he was at the orphanage, the Orphanage Director used to make it for him often. It was a simple dish: a dough made by mixing equal parts bread flour and cake flour, kneaded with water, torn by hand into chunks, and then boiled in a clear soup.
The original version had been basic, featuring only green onions, but the dish served now was an improved version of that foundation. The ratio of cake flour was slightly higher to increase the softness of the dumplings. However, they had to be careful not to boil them too long, or they would fall apart. The clear soup was finished with a proper dashi broth, and in addition to shalots, it was packed with wild vegetables gathered from the hills near Kaina Village.
"This is delicious! The texture is so unique."
Tiberio had clearly taken a liking to it.
"Is this the second time I've had this? It's wonderful."
Jin had served it to Marcia once before on Hourai Island, and it had been such a hit that he decided to put it on today's menu.
"Yes, it's even easier to eat than last time."
If there was too much bread flour, the dumplings held their shape better but became quite chewy. While that was fine for something the thickness of udon, many people found them a bit too hard when served as hand-torn chunks.
"Yeah, it's good."
Jin was satisfied with the result. It was a refined version of a nostalgic flavor.
"Father, there are seconds if you'd like."
"Yeah, thanks."
Jin’s portion had been carefully adjusted, the soup slightly cooled to match his preference. It was the kind of attentive detail only Reiko could provide, knowing her master's tastes inside and out.
＊ ＊ ＊
"Now then, shall we discuss the improvements?"
Marcia spoke up the moment the post-meal tea was served. She was a true workaholic.
"Come on, let's rest for just a little longer," Jin chided her, blissfully ignoring his own similar tendencies.
"Ugh, fine."
"...Marcia-san really does love shipbuilding, doesn't she..." Tiberio whispered.
"Ah, hahaha."
"Well, since we're relaxing, how about I share some technical insights about ships?"
When the wryly smiling Jin made the offer, Marcia bit at the chance with lightning speed.
"Yes, please!"
Even Rodrigo looked expectant. "Technical talk from the Magi Craft Meister himself? I'm looking forward to this."
Tiberio’s interest was equally apparent.
"I hope I don't disappoint you all," Jin prefaced, before beginning his explanation. "Now, why is it that a ship floats on water?"
Jin began to explain Archimedes' Principle. Rodrigo, who wasn't familiar with the specifics, leaned in to listen.
"An object placed in water becomes lighter by the weight of the water it displaces. Therefore, the weight of the water equal to the volume of the submerged part of the ship is exactly equal to the ship's total weight."
"Huh..."
"The same applies to an airship—like Konron 2 or Konron 3. If the inside of those gas bags were a vacuum, the ship would become lighter by the weight of the air that would normally fill that space, causing it to rise."
"I see."
Jin added that since air pressure would crush an empty gas bag, the next best thing was to fill it with helium, a gas lighter than air.
"...But let's get back to ships. The weight of an object divided by its volume—its weight per unit volume—is called specific gravity. We use water as the standard, setting its specific gravity at 1. If you divide a ship's weight by its volume and the result is less than 1, it floats. If it's greater, it sinks."
"Aha, I follow you," Tiberio said, nodding repeatedly.
"By the way, if you have an object with a shape that's hard to calculate, you can find its volume by submerging it in a container filled to the brim with water and measuring how much overflows."
By finding the volume this way and weighing the object, one could calculate its specific gravity. Jin mentioned that this was how a famous scholar once determined if a crown was made of pure gold or an alloy.
"How fascinating."
Jin explained the concept without using names like "Ancient Greece" or "Archimedes," but the lecture was received exceptionally well.
"You must tell us more sometime."
Having had a sufficient post-meal rest, the group finally transitioned into their design review meeting.