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Setting: Urban Fantasy/ Think present daytime, but with RPG elements.

Summary: My MC needs to make armour for his army. He can do so using his crafting skill. The skill would allow him to make any Item that he has become familiar with (gained its template). He can swap out/in other material when making the item. (Example: turning a silk scarf template and crafting a wool scarf)

Rules:

  • He can only use dead/living material (Think bone, silk, wood, leather, nails, teeth, etc.)
  • He can make the material fit the design. (Think bone plate looking as if cast out of one piece of bone, not several bits stuck together. Bio printed look)
  • He can use magic to upgrade the item three times (Making the bone denser, or mixing it with another living/dead material).
  • He can repair the armour after every major engagement, but it has to hold up on its own for a while.
  • The people wearing his army are 50% stronger than your average human. So the armour can be thicker/bulkier looking (Think 40k Space marine armour).
  • The bone he’d be using would be similar to those he can find on earth (Human, cow, bull, crocodile, etc.)

Scene: The people fighting him would be typical fantasy knights wielding steel swords, axes, clubs, etc. The army he would command would be like humans, only slightly stronger.

Question: Could his bone armour ever get similar defensive capabilities to steel if he can mix it with other materials he can use, or simply upgrade the armour several times to make it denser?

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    $\begingroup$ Crafting magic could benefit from more details : Can he make a wood scarf, and if so, has it the same hardness as wood (ie be very impracticable to wear) or as the silk recipe he knows? Does he know big armor templates for his space marines troops or does he have to use regular, frailer soldier armor instead? $\endgroup$ Commented Jul 27, 2022 at 8:42
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    $\begingroup$ "Think present daytime" and "typical fantasy knights wielding steel swords, axes, clubs, etc" don't quite gel. Obviously the victors would be the ones who picked up some decent modern firearms. $\endgroup$ Commented Jul 27, 2022 at 9:13
  • $\begingroup$ Good question no. He’d be able to swap materials that make sense. So a cloth and steel piece of armour he could create out of leather and bone. A wool scarf he could create out of silk, or a shield from wood could be turned into bone. So the materials would have to make ‘sense’. Modern weaponry would not be a factor in this scene. He’d be mostly facing people that would have comparable armour/weaponry as those in the medieval era. (Bows, crossbows, axes, shields, swords, plate mail, chain-mail, gambeson, etc) $\endgroup$ Commented Jul 27, 2022 at 9:39
  • $\begingroup$ @OsiriumWrites just shoot them, then they won't be getting in range to use their bows and swords. Job done! $\endgroup$ Commented Jul 27, 2022 at 11:03
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    $\begingroup$ without knowing how much stronger magic can make bone this can't be answered. $\endgroup$
    – John
    Commented Jul 27, 2022 at 14:20

3 Answers 3

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Like some scientists the MC uses bioinspired materials to make his armor.

Oysters shells for example can be extremely tough and have the benefit of being light. The secret is how the shell's microstructure is organized and dissipates the energy. A previous answer has a picture of armor made of shells and note that helmets were also made using cowery shells. There was a bunch of press a few years ago about how DOD was funding research into a transparent oyster armor based on a kind of oyster found in the Philippines. By controlling layered structure could also be tailored to make different colors or be shiny like mother of pearl.

Layers within pearl

Limpet teeth are thought to be the strongest and toughest natural material. Again due to the microstructure

The teeth are both stretchy and strong thanks to their unique composition. They contain millions of aligned nanofibres, made from a natural mineral called goethite, which are embedded in a softer shell of chitin. Amazingly, samples were stretched to four times their original length without losing their elasticity.

The goethite is a form of iron oxide, and the chitin is a natural polymer.

Limpet tooth microstructure

So perhaps when your MC is meditating or crafting he might be thinking of shells or bones and realize if he makes them with little tiny sliding bricks connected with more springy stuff, and instead of just the calcium of bones he has a little iron available and ends up with little iron oxide crystals instead of calcite crystals....

Perhaps he ends up with a very light weight tough armor, and perhaps how he does it, it could be colors in various ways or shiny, after all it is magic.

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  • $\begingroup$ This is perfect! Thank you! $\endgroup$ Commented Jul 27, 2022 at 14:42
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Bone is bad, but there are ways he can make better armor than real armor.

For the purposes of armor (tensile and shear) the densest bone has comparable strength to pure aluminum for armor, once you account for it being slightly lighter but slightly weaker. Its about half as stong but also half the weight so you can even them out with density, but you can't go any denser because you will have already hit the point of it being completely solid bone. So the magic armor is about as strong as aluminum as the same size, which means it is shit compared to steel armor. Its better than textile armor but worse than even crappy steel armor.

the main constraint on armor is less weight than it is bulk, armor interferes with movement, making it drastically thicker makes it worse than useless. to reach the same strength as low quality steel armor you bone armor would need to be about 5-6 times thicker. this means it is about 10-15mm thick, or for americans the "metal" part of the armor is about half an inch thick. this means you can't make gauntlets out of it, and it will interfere with most movements. Bone is better than nothing but much worse than steel. it ends up ridiculously thick, remember it still needs cloth padding underneath it. You can't just make up for bulk with strength, you can't move your arms through your armor no matter how strong you are. His armor is lighter but worse than steel armor. If they really are so strong that is even more reason steel is better, weight means even less than bulk for them.

Actually the one saving he may have is he can make better armor padding, he can make foam leather/chitin which means he can make much much better and lighter padding than armor normally has, comparable to modern foam padding. that's where the real benefit is, if he gets real steel armor made he can make much better padding, lighter, more effective, and custom fit.

If he has you use bone the armor needs to have far less coverage to make up for the bulk, every opening needs to be exaggerated. Again better than no armor or just cloth armor but it will never be as good as steel.

Bio-composites.

if he can make armor out of anything organic he can make decent armor. he can make it out of bio-composites. once his still is high enough he can layer goethite and hydroxyapatite in a chitin matrix. he can get something comparable to modern composites, which combined with better padding means fairly decent armor, not quite as good as the best steel (its hard to beat a reinforced iron lattice without going to carbon fiber) but about as good as low grade steel armor and lighter to boot. It will be about twice as thick (but still lighter) and it may not hold up as well but it will be serviceable armor.

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Comparing strength of bone and steel

Young’s Modulus (GPa) Bulk Modulus (GPa)
Bone 80 15
Steel 190 - 210 160

Steel is much stronger than bone.

Bone Tissues

Bones consist of different types of tissue.

  • Compact bone makes up the dense outer layer of bone. Its functional unit is the osteon. Compact bone is very hard and strong.
  • Spongy bone is found inside bones and is lighter and less dense than compact bone. This is because spongy bone is porous.
  • Bone marrow is a soft connective tissue that produces blood cells. It is found inside the pores of spongy bone.
  • Periosteum is a tough, fibrous membrane that covers and protects the outer surfaces of bone.

Increasing bone strength

To increase the strength:

  • Compact bone consists of closely packed osteons or haversian systems. MC will convert spongy bone and bone marrow into compact bone by adding or increasing the density of osteons.
  • MC will replace spongy bone and bone marrow with Compact bone taken from other bones.
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  • $\begingroup$ Correct. But the MC can use magic to enhace the materials he is working with. So, say he wants to make a breastplate out of bone. He could further enhance the bone material with more bone, making it denser. Would something like that be reasonable, or would it prove to heavy? $\endgroup$ Commented Jul 27, 2022 at 9:37
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    $\begingroup$ If magic can make bone as strong as steel, then magic can make bone as light as feather. $\endgroup$
    – imtaar
    Commented Jul 27, 2022 at 10:15
  • $\begingroup$ This answer needs a why. Why is bone less strong than steel? It doesn't provide insight or knowledge compared to the base question nor to the underlying problem. Additionally, strength and be various moduli are not the same as strength (or toughness), although they are often related. $\endgroup$
    – PipperChip
    Commented Jul 27, 2022 at 16:05
  • $\begingroup$ @PipperChip To explain why steel is stronger than bone, we need to explore atomic structure, bonding of atoms, forces of attraction between atoms of iron and carbon and other materials, slipping of crystal planes etc. We can read books on "Strength of Materials" or take a course in a University. $\endgroup$
    – imtaar
    Commented Jul 28, 2022 at 8:41
  • $\begingroup$ @imtaar I am well aware of the intricacies of materials and acknowledge a post on the internet can only be the tip of the iceberg, but properly answering this question requires condensing and summarizing the underlying issues. This answer does none of that, simply stating what the asker already knows. Answers are not useful if we do not shed more light on the situation. $\endgroup$
    – PipperChip
    Commented Jul 28, 2022 at 13:16

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