Boundary Foil

A rotary driven craft that, partially or fully, passively rides the boundary layer of two different media whose "gearing ratio" is adjusted for acceleration and/or top speed
Published: 7/7/21
Author: GiverofMemory
Maintainer: GiverofMemory
License: Site License
Categories: See Footer
See Also: Solar#light
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Discussion: BoundaryFoil-Talk
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This is a water foil similar to a kiteboard but with a propeller or otherwise turning device below the water that is geared to a fan or turbine or otherwise turning device above the surface of the water. It also has some sort of hull or platform that can either touch the water or preferably be slightly above the water most of the time to reduce drag.

So this invention is not only for a board, but also a boat. The difference to a standard boat is it uses foils with the propellers below the water. These foils can provide lift and/or stabilization and/or anything else in addition to the rotary motion, but do not need to.

The diameter ratio between the fan and propeller is very important. Also the gearing ratio between the two is also very important. These should be tuned for each intended use case.

As the wind pushes the craft forward the rotation of the propeller in the water turns the fan and blows the craft forward. It can theoretically travel faster than the wind. This craft can theoretically travel with the wind or against it. It is based on the "travelling faster than the wind" invention

Here is a picture of one possible implementation of this invention. The rider can also be holding a parachute or a sail or something else to help the craft get going. The way to think of this physics principle is you are trading acceleration for top speed. So you might need a "starter" to provide some initial acceleration such as a sail or parachute.

Of course there can also be variable gear ratio's to act as a sort of transmission, or even multiple propellers and/or fans of different sizes to provide optimal torque at different speeds. For example a small propeller and/or big fan might be good for slow speeds getting started (or vice versa), and a big propeller and/or small fan might be good for getting torque at high speeds (or vice versa). These realities can be used with, or instead of, other "starter" methods like sails or parachutes. All can be used together if desired.

Also of course this invention can be used in combination with other conventionally or future propulsion methods including gas power, electric power (including solar power and/or electrosolvumdynamics), nuclear power, etc.

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