"Hmm, I wonder how using canards in this configuration will work out?"
Jin voiced his thoughts.
"What do you mean, Jin-sama?"
Rubina asked.
"Well, when flying through the air, a disturbance called turbulence is generated behind the wings to a greater or lesser degree. That's why in aircraft, the main wings and tail wings are attached slightly offset from each other."
"Ah, is that so?"
"In other words, you are concerned that the turbulence created behind the canards might negatively affect the main wings, correct?"
Lordtoss grasped what Jin was trying to say.
"Right. So, tailless aircraft do have their own set of advantages."
Jin had never formally studied aeronautical engineering, aerodynamics, or fluid dynamics. He had only acquired fragmented knowledge during the process of building models.
On the other hand, that knowledge was quite practical.
Even so, since it was intended for models, it remained somewhat questionable how well it would apply to full-scale craft.
"If that's the case, then maybe this one instead."
Jin picked up another sheet of paper and folded it deftly.
This time, it was a standard triangular paper airplane.
Incidentally, there were hang gliders with a similar shape as well.
"It's called a delta wing, and this shape is well-suited for building up speed."
Conversely, it was also well-suited for flying as a paper airplane. In other words, its usable speed range was wide, Jin explained.
Because it allowed for a large wing area, the wing loading (aircraft weight per unit of wing area) could be kept small, ensuring stability at low speeds.
"I'd love to go with this one."
Rubina was the first to agree.
"Yes, that sounds quite good."
Lordtoss agreed as well.
"All right, let's conduct our research along these lines then."
Jin stated his conclusion.
To put it bluntly, since this was a world with magic, they could force things to work out to some degree.
Even so, a design following the laws of physics was undoubtedly more efficient.
"So, is this our research?"
"Experiments with models are important."
Jin and the others were conducting experiments by folding origami airplanes of various shapes, launching them, observing them, and repeating the process.
"We aren't aiming for supersonic speeds, so the sweep angle doesn't need to be that steep."
Jin was thinking of setting the sweep angle to around sixty degrees, making the planform an equilateral triangle.
"Indeed. That shape seems well-balanced as well."
"Wouldn't it be fine if it were a bit wider? Around forty-five degrees, maybe?"
"In that case... seen from above, it would be a right triangle. That wouldn't be bad either."
Jin and the others continued exchanging opinions like that.
Over on Hourai Island, Reinhard was also riding this wave of enthusiasm.
Although he did not usually take much interest in vehicles, it seemed the Marikka Cup had set his blood boiling.
"Maybe I'll try building a craft for myself too....Leila, lend me a hand."
"Yes, Reinhard-sama."
Leila was an automaton Reinhard had crafted with wisteria-colored hair.
Usually, she served as his assistant like this, and by donning a suit of armor, she became the Black Knight.
That said, outside of test runs, she had never publicly unveiled her Black Knight persona. There had simply been no need.
Reinhard leisurely proceeded to build his craft at his own pace.
In the end, Jin and his group's prototype became a delta-wing aircraft with a forty-five-degree sweep angle.
Viewed from above, it was an isosceles right triangle, but because the wingtips were clipped off and fitted with vertical ailerons, it looked like a stubby shogi piece or a truncated home plate.
"In the models, this was about the most stable."
"Indeed."
Though called models, they had been fabricated out of 64 light silver. While they started at around thirty centimeters in total length, by the time of the final experiments, they measured two meters in length—nearly half the size of the actual craft.
They had Reiko throw them to observe their gliding performance.
"Oh, right. How about we build three craft with the same basic configuration?"
Jin suggested.
"Ah, and then each of us can do the final adjustments individually?"
"That sounds interesting."
Rubina and Lordtoss agreed as well.
Even so, design came first.
Since there were no formulas to calculate the necessary values, many parts had to be decided by rule of thumb.
The wing area had to be balanced against the anticipated aircraft weight (including passengers), but with abundant precedent data available, this posed no problem.
As for strength, using 64 light silver for the structural materials made it easy to Reinforce, so that did not present much of an issue either.
That being said, since Jin was overseeing it, the baseline strength alone was already more than sufficient.
"And then there are the control surfaces."
Since it fell under the category of a tailless aircraft, elevons (elevator + aileron) would be placed on the main wings, and a rudder on the vertical stabilizer.
"Considering low-speed situations, let's add thrusters as well."
"That would be best."
These would be operated from the cockpit using control cables.
"Have you decided on the specifications for the propulsion system and Blow Engine?"
Lordtoss asked Jin.
"Of course. I plan to give this part a design with plenty of margin."
Jin intended to design and Craft it himself.
"If so, all that's left is the area around the cockpit."
Rubina insisted that she wanted to give some thought to comfort, and neither Jin nor Lordtoss had any objections.
"We'll probably be riding it for somewhat long periods, after all."
Jin also wanted to suppress vibrations and shock upon landing.
The concepts for these structures were already well thought out; all that remained was to build and adjust them.
The prototype was completed the following day.
The test flight by Reiko was a complete success without any issues.
"We did it."
"We did it!"
"We managed it."
Upon the earnest request of Rubina and Lordtoss, the first craft they built was to be preserved.
Their reason was that "since this is a masterpiece we built ourselves, we want to keep it in its completed state as a memento for ages to come."
Once built, it remained as a design base, reducing the labor to recreate it to less than a tenth. The more they mass-produced it, the greater that benefit became.
This time, they were to build three identical craft, adjust them individually, and compare them.
Jin was looking forward to that in its own right.
"Reinhard is building something too, after all."
Since the time difference between Onogoro Island and Hourai Island was exactly half a day, sleeping and waking according to their respective day-and-night cycles meant they could not easily know each other's status, but that was where Laojun came in.
Through Laojun, Jin and Reinhard were able to keep track of each other's situation, albeit briefly.
"If we're going to compete, it would be nice to do it on Planet Hehl."
At Jin's words,
"That sounds wonderful."
"That sounds great!"
Both Rubina and Lordtoss agreed.