26

For regular paper weight and size A6, roughly a card postal size one can tear from the middle vertically the top half and bend the two flaps 90 degrees in opposite directions like a helicopter's blades and fold the bottom half on itself like a narrow rod to make it act like balast. This will be a primitive gyro- copter and will descend in a slow controled ...


17

I really love this game idea! I think a flat piece of paper falling face-down is probably the least aerodynamic thing you could possibly drop if it maintained its shape and orientation, but naturally the paper bends and changes angle (edge-down) as it descends, tending towards the path of least resistance. Therefore, my thought is that your goal should be to ...


8

What a fun challenge! We had a good time trying out various designs :) I did eventually come up with a helicopter-style design that falls about 50% slower quite consistently. Build instructions: Cut diagonally along the red line. Fold one half in the opposite direction. Fold up the edges along green lines to add rigidity. Put a single staple through the ...


6

Extrapolating from the Gyrocopter idea for A4 paper size, I arrived at following conclusions: Bending (i.e. not creasing a fold) part of the helicopter blade along its length provides ample structural stability at the cost of some air resistance. The result however has a nice wing profile. Structural stability is most important at the blades' root, so you ...


5

The factors that affect a car's top speed - IMHO - can be grouped to the power train factors : engine power gear box and differential ratios size of the wheel and to the losses: overall aerodynamic coefficient of drag friction related loses (e.g. wheel resistance), (however for the top speed it has a negligible effect). Usually regarding the losses the ...


4

It is important to realize any airborne device will go in the direction of the sum of all force vectors (including gravity). We have our centrifugal impeller drawing air in from the bottom. The device will be pulled down. The air flow out the sides will create low pressure, pulling the device down. The device will have a better chance flying if it is ...


3

You do not want to overcome the force of static friction when accelerating because that's when the dynamic friction takes over and your wheels slip. That means that the force applied on the edge of your wheel is limited by the static friction which limits how much effective torque you can apply to accelerate (or maintain speed while overcoming losses due to ...


2

I suggest using the relationship below to derive the equations you are looking for. $F = ma$ $W = mg$ $D = \dfrac{C_d\rho V^2A}{2}$ $C_d$ = Drag Coefficient (Shape dependent) $\rho$ = Atmospheric Density The terminal velocity is reached when $W = D$, $mg = \dfrac{C_d\rho V^2A}{2}$, thus $V_t = \sqrt{\dfrac{2mg}{C_d \rho A}}$ Note, at this stage, $a = \dfrac{...


2

This question could get better answers in the Aviation StackExchange. You are right partially in that at the beginning of the stall the vortices separate from the top of the wing but the wing still has significant lift albeit with a lot of drag. But in the next stage of the stall, these separated vortices get blown past the trailing edge of the wing and the ...


1

With respect to the ground, an airplane tears up the air it goes through - the disturbance isn't uniform it's unsteady, it moves across the world. With respect to the airplane, the air flows around it the same way all the time. Airflow around the plane is uniform and steady.


1

TL;DR: I will expand on DKNguyen answer, which provides all the salient points. i.e. (my interpretation) the downforce is desirable to provide a better interface/grip between the car and the ground.) Comparison of drag and lift coefficients for automobiles. The following graph presents a comparison of drag and lift coefficients. figure (source ...


1

What limits top speed is technically how high the wheel RPM can go. because even with infinite torque and traction for the wheel, the car isn't going to go any faster than the linear velocity the edge of the wheel is turning at. But what limits the car's ability to get to theoretical top speed is the torque output to overcome the ever increasing losses as ...


1

TL;DR: the time required to reach a $p$ percentile of the Terminal velocity $$ t_p= \sqrt{\frac{2\rho_{sphere}r}{g \cdot C_D \rho_{air}}}arctanh\left(p \right)$$ the distance travelled required to reach a $p$ percentile of the Terminal velocity $$ x_p= \frac{2\rho_{sphere}r}{C_D \rho_{air}} \log \left(\cosh\left(arctanh\left(p \right)\right )\right ) $$ ...


1

The terminal velocity $V_t$ will be reached when the drag coefficient is equal to the force of gravity: $$F_{drag} = mg$$ $$C_D\frac{1}{2}\cdot \rho_{air} \cdot A \cdot V_{t}^2= m\cdot g$$ where: $C_D$: is the drag coefficient (for a sphere is 0.5) $\rho_{air}$ is density of the liquid the sphere is passing through (if air then 1.225 kg/m3) $A$: cross-...


1

No. Lift will not be created. The split toroid shape is not of any use. The airflow turning into the "donut" creates turbulence (and hence losses) and a downwards force since the airmass is accelerated upwards. Further degrading any desired lift would be the fact that the air would mostly circulate out of and into the impeller. As mentioned in ...


1

Nature created a light structure (hollow bones in birds), materials (feathers) and a precision control system (brain, nerves, muscles and tendons etc) to achieve flight. Matching that with the tech we have is challenging since hollow tubes do for the bones and hang gliders have that. The materials used in terms of silks etc are light but any matching of ...


1

I'm not exactly clear what you're asking but I'll try an answer. I didn't watch the other video, but a teardrop shape is the best pure shape. Bullet train design has diverged from the original design (shaped like a bullet), which was solely concerned with air resistance. The changes have led to elongated noses that act to help with two trains meeting or ...


1

Just the ambient pressure. The dynamic part is used separately in other contexts. I am a private pilot. During the flight sometimes the ATC (air traffic control) issues information and weather advisories like: Altimeter 2990. winds 160 at 25. we set the altimeter at that pressure. The altimeter reads the ambient pressure. The dynamic stagnation pressure is ...


1

To add more to Kamran's answer, Generally for streamlined bodies like aerofoils, pressure drag force << Skin friction drag force << lift force. If the flow is separated, there will a reverse flow on the surface of the aerofoil and this will lead to a drastic increment in skin friction drag. so the efficiency $(C_L/C_D)$ of the airfoil also comes ...


Only top voted, non community-wiki answers of a minimum length are eligible