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FOLIO 5 (verso)
A page from Manuscript H containing Leonardo da Vinci's investigations into the physics of air and flight, comparing air resistance to the buoyancy of water.
A facsimile reproduction of Manuscript H, folio 5 verso, shows Leonardo's characteristic mirror writing in Italian.
On motion original: "motu"
If the falling weight presses against itself from below as much as its own weight, such motion will be of a slowness almost equal to the motion of birds. With ribs original: "rami," literally branches, here referring to the structural supports of a wing that beat the air, and with little force, a man will be sustained in the air without any hindrance.
O
If the flyer has the weight of four men, and its wings have a length of 40 cubits braccia: an Italian unit of length, approximately 23 inches or 58 centimeters and a width of 8 cubits, and they weigh 200 pounds original: "libre", it will be so.
O
The air will provide such resistance that it can support the bird, just as water supports a ship original: "nauilio" that enters into it with its weight.
O
FOLIO 6 (recto)
Folio 6 recto of Manuscript H, where Leonardo analyzes the density of air and its behavior around moving objects, drawing parallels with navigation.
A facsimile reproduction of Manuscript H, folio 6 recto, displays Leonardo's mirror writing and his analysis of fluid dynamics.
The flyer will fall apart if the wings are not joined to one another by ribs, because air, like water, is composed of a dense substance. For this reason, it opens reluctantly before the motion of a ship, and even more reluctantly closes behind that ship. This arises from the difficulty and sluggishness of the movement of the air that must reunite.
O
On motion original: "motu"
Air moves with almost as much difficulty as water and is of nearly the same nature. Because air moves like water behind a ship, it is composed of a density and softness such that it cannot quickly close over the back of the vessel.
O
FOLIO 6 (verso)
Folio 6 verso of Manuscript H, detailing the materials and dimensions for the construction of artificial wings.
A facsimile reproduction of Manuscript H, folio 6 verso, shows Leonardo's technical notes on the construction materials for a flying machine.
Just as the air opens reluctantly at the front, it closes even less easily behind the flyer.
O
On motion original: "motu"
One of these wings shall have ribs 40 cubits long and 8 cubits wide. It shall be composed of ribs made of cane with fustian fustian: a heavy, durable cloth made of cotton and flax skin over them, and with donkey skins over the fustian. The fustian should be on the underside so that as the flyer moves, the air is pushed aside and does not pass between the ribs of the flyer. You must ensure that the said wing is dense meaning airtight or impermeable.
O
FOLIO 7 (recto)
Folio 7 recto of Manuscript H, focusing on the airtightness of wing structures made from cane and skin.
A facsimile reproduction of Manuscript H, folio 7 recto, shows the conclusion of Leonardo's instructions for making the wings airtight.
On motion original: "motu"
The ribs shall be made of cane with a covering of fustian, and donkey skins over the fustian. The donkey skin should be over the fustian, and there should be fustian on the underside so the air does not pass through the ribs.
O
You must ensure that the wing moves with such velocity that it generates a force to prevent the air from passing through the ribs. It must be dense so that its nature does not allow it to open between the ribs of the flyer. You must make the wing dense so the air is trapped beneath it, using the strength of fustian and donkey skin.
O
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