Terminology

Aerodynamic center

The point where the pitching moment due to the pressure forces (the moment causing the airfoil to rotate up or down) does not change with angle of attack.

Aspect ratio

For aircraft, this is the ratio of the wing span to the mean chord. For a fish tail it is the ratio of the tail height to the height of the tail where it attaches to the fish’s body, the caudal peduncle.

Angle of attack

The angle of the airfoil relative to the flow direction

Brushless motor

A Brushless Motor (BLDC Motor) is a motor that doesn’t use brushes to spin the core. The advantages of a brushless motor over brushed motors are high power to weight ratio, higher speeds, higher efficiency, and low maintenance.

Buoyancy

Archimedes principle tells us that there is an upward buoyant force on a body in a fluid equal to the weight of the fluid that is displaced by the body.

Caudal peduncle

Where the tail of a fish meets its body.

Center of buoyancy

The center of buoyancy is the center of mass of the displaced fluid.  

Center of gravity

The center of gravity is the point about which all weights are evenly spread, so both the magnitude of the weight and the location of the weight matter.  

Center of pressure

The location where lift and drag forces act; center of pressure will change with angle of attack.

Centroid

The mean position of all points in a shape.

Chord

The chord is the line that connects the leading edge and the trailing edge of the wing.

Compression

When a structural member is being pushed on.

Density

An object’s mass per unit volume.

Dihedral

Upward angle of the wing.

Drag

Drag is a force on a body, moving in a fluid, that opposes the direction of motion.

Electronic speed controller

An Electronic Speed Controller (ESC) is used to control a brushless motor’s movements through energizing magnetic coils to rotate the motor.

Feather microcontroller

In this kit we use an Adafruit Feather HUZZAH ESP8266 WiFi microcontroller. Please view the Adafruit Website for more information.

Free body diagram

A sketch of a system used to represent all the forces and moments on the system.

Fuselage

The body of the airplane.

Gravity

The force that attracts an object towards another object with mass (for us here on Earth, it’s the force pulling us down to the center of the planet).

JST connectors

JST (Japan Solderless Terminal) connectors are electrical connectors of a standardized type.

Lift

Lift is the component of the aerodynamic force that acts perpendicular to the fluid flow.

Moment of inertia

A measure of how much a shape resists bending; has units of length⁴.

Neutral buoyancy

When an object is neither sinking nor rising.

Pin headers

Male and female headers are distinguished by pins (male side) versus sockets (female side).

Pressure

The ratio of the amount of force to the area over which it is applied.

Servo

A servo is a motor that can be controlled precisely. The servos we include in the BLIMP kit are non-continuous servos that have precise control in a 180 degrees of motion and weigh 3.7 grams.

Step-down regulator

A Step-Down Regulator is a module in which the output voltage is lower than the input voltage. We use this to lower the input voltage from 7.4 volts to 5 volts so that we don’t fry the feather board!

Tension

When a structural member is being pulled on.

Thrust

A propulsive force (for example, the force of a jet engine pushing an airplane forward).

Truss

A truss is an assembly that uses beams and simple connections, often leveraging triangular geometries, to make a remarkably strong structure.

Vector

A vector is a quantity with both magnitude and direction (example: forces are vectors).

Viscosity

Viscosity is a measure of the stickiness of a fluid.

Wing span

Distance across the wing, from one tip to the other.

Wing sweep

Angle the wing makes with the fuselage.