"Of course you can. If there are any materials you need, feel free to ask Butler B or C."
When Greena and Freddie tentatively brought up their desire to research Blow Floaters at Jin Nidou Castle, Jin gladly gave his approval.
"Isn't that great, Freddie?"
"Yeah. First, let's build a basic craft."
"Right."
Using 64 light silver (= titanium) for the framework, Freddie and Greena began constructing their own original Blow Floater.
"Forming! Forming!"
"Ugh, this is tough... Why is it so hard to get the dimensions right on the first try?" Freddie grumbled.
With extremely small components, the slightest error could lead to massive discrepancies, while with exceptionally large pieces, it was difficult to gauge the overall dimensions. Both extremes were a magi craftsman's nightmare.
"Jin-sama makes it look so effortless, though..."
"...I don't think it's fair to compare ourselves to him."
"True."
"Let's just work at our own pace."
"No objections here."
Freddie and Greena were in complete agreement.
"...So, for now, we're designing it as a three-seater, right?"
"Yes. Basically, only the two of us will be riding, but I think having some extra room is important."
"I agree. In that case, should we make the dimensions roughly the same as Jin-sama's Taube?"
Just then, Butler B chimed in with a suggestion.
"If it helps, I have a reference table correlating total weight with the required wing surface area."
"...What do you think?"
"I don't see any harm in looking. Those values shouldn't change from person to person, after all."
It was essentially a mathematical table. Since the numbers were universal constants, Freddie figured there was no reason not to reference them rather than wasting time calculating everything from scratch.
"Hmm... I suppose you're right."
Greena agreed, and they proceeded to settle on the diameter of the disc wing that would serve as their main lifting surface.
"It all comes down to balancing it with the Blow Engine, right? How about we start a bit on the larger side just to give ourselves plenty of leeway?"
"Yeah, sounds good."
The two continued working in this manner.
Debating their ideas back and forth along the way, they spent five days completing a single Blow Floater.
"Hmm..."
Before taking it out for a test flight, Freddie and Greena asked Jin to give the entire craft an inspection.
For his part, Jin appreciated that they didn't let pride in their work get the better of them and were willing to ask for a review.
He inspected the craft with thorough care.
"Mm-hmm. Joint strength is sufficient, and the material distribution is even. The framing looks solid."
Jin went through his checks step by step, sharing his findings as he went.
"You used thinned 64 light silver for the wing surface as well, huh? The current strength is adequate, but you might want to reconsider that for future designs."
"What do you mean by that?" Greena asked.
"Right now it's fine because the framework of the main wing is shaped like this. But if you ever switch to an elliptical wing or a diamond wing, certain sections might end up lacking sufficient strength."
Because the wing caught airflow from below, it was constantly subjected to forces trying to peel it apart, Jin explained.
"Although it will add weight, it would probably be better to increase the number of ribs. You can offset the extra weight by strategically lightening the structural members with cutouts."
"...I see. Understood."
"As for the Blow Engine output... looks like there's plenty of headroom. It should be more than enough."
"What a relief."
Hearing Jin's final assessment, Greena let out a sigh of relief.
Freddie, meanwhile, was already brainstorming ways to put Jin's advice into practice.
"Jin-sama, regarding what you mentioned earlier, could we use Ground Spider resin for the wing covering?"
Tensile strength was arguably the single most critical quality required for a wing's outer skin.
The Ground Spider resin produced on Hourai Island possessed even greater tensile strength than un-Reinforced 64 light silver.
"Ah, that's a good eye. Though in that case, you'll need to add quite a few more ribs to support it."
"Right!"
Freddie beamed, thrilled to have his idea validated by Jin.
"J-Jin-sama, are there any tricks to lightening a structure?" Greena asked in a bit of a rush, not wanting to fall behind Freddie.
"Well, now. It all comes down to understanding the structure so you can cut weight without sacrificing strength. It might be worth your while to look into structural mechanics."
"Understood!"
Structural mechanics sounded a bit imposing, but the library at Jin Nidou Castle held reference materials on the subject.
Take bending strength, for example, using square beams of uniform length as an illustration...
Setting a beam with a cross-section of 1 × 1 (height × width) as the baseline, what would the vertical bending strength be for beams measuring 1 × 2, 2 × 1, and 2 × 2, assuming the material and length remained identical?
Providing the answer to that question was the domain of structural mechanics.
If the strength of 1 × 1 was considered 1, then 1 × 2 would have a strength of 2, while 2 × 1 would reach 4. Following that logic, 2 × 2 would be 8.
In other words, a cross-section that was taller in the direction of the bending force provided significantly greater resistance.
From this principle, one could see that the extreme upper and lower edges bore the greatest load when resisting a bend, which naturally revealed the optimal areas where material could be hollowed out without compromising structural integrity.
Furthermore, while a quadrilateral would easily distort under lateral forces, a triangle would not. This was the foundation of a truss structure.
By utilizing trusses, exceptionally strong frameworks could be constructed from slender, lightweight members.
The Dome roofs and diagonal cross-braces between pillars were classic examples.
Beyond that, there were rigid frame structures where the joints were rigidly fixed to prevent deformation.
In terms of cross-sectional design, there were the H-beams commonly seen in steel construction, the L-angles and C-channels favored in aluminum work, and honeycomb structures.
Hollow pipes, too, were products of structural mechanics.
At any rate...
Rather than giving them the direct answers, Jin chose to point them toward building that foundational knowledge for themselves.
"I see... I've always been the type to think practical experience matters more than theory, though."
Hearing that, Jin chuckled.
"Haha, someone with an artisan's mindset naturally leans that way. Conversely, someone with a researcher's temperament will prioritize theory first. Neither approach is wrong; it's all about finding the right balance."
To Jin, Greena seemed more artisan-minded, while Freddie leaned toward the academic side. In his eyes, they made a well-matched pair that complemented each other's strengths.
"Either way, is it all right if we take it for a test flight?" Greena asked.
"Sure, go ahead. Just be careful, all right?"
"Yes!...Um, we were actually planning to have Shal serve as our test pilot."
Shal was the child-type automata with red hair and brown eyes that Greena had built previously.
"That's a sound choice."
Jin himself often entrusted test runs to Reiko or Jin D. It made even more sense here, considering neither Greena nor Freddie had any real experience piloting a Blow Floater.
Granted, Greena had at least piloted the elliptical-wing aircraft Tempest via remote control before.
Regardless, safety came first.
And so, under the watchful eyes of Jin, Reiko, Butler B, and Butler C, Greena and Freddie prepared to conduct the maiden flight of their prototype Blow Floater No. 1.