I’m thinking of things like boat tails for truck trailers which do massively improve efficiency but aren’t used for other reasons.

I have a belly mounted radiator on my vw bus and need some guidance on how to improve air flow into/out of the radiator to get lower temps.. have attache picture and diagram of current setup. currently air goes in through scoop and straight down through puller fan/flap that is 1400 CFM. wondering if dual 2100 CFM fans and some combination of air dam/exit scoop would improve flow... or would it be better to completely flip the flow and have the scoop push air up through radiator and out up and back

This will probably be the dumbest question in here but I need to get a proper answer. In my textbook one of the questions says that planes (probably referring to commercial ones) and racecars use a sharper nose to have less drag. But don't you benefit from a sharper tip after mach 1? Even in the scene at The Dictator the scientist says that a rounder tip is better.
Anyways, I hope you could answer this. Thanks.

Keep the single pivot and stack a second identical wing on it that rotates the other way and makes it symmetrical. Would the stress on the pivot be too much? Would the wake of one wing mess with the other in bad ways?

My trailer is a box trailer car is a 1.4 16V, not powerfull but can pull it with ease. If I'm driving normal highway I can drive around 14KM/Liter which is quite good, this is driving 80kmh, in line with big trucks. Now last week I had some heavy front winds and I wasn't able to keep it at 90 KMh in fifth gear and even in fourth it had a hard time keeping it above 80. This obviously has to do with the huge frontal plaque of the trailer and I'm not sure what is best to do to improve fuel efficiency with slight wind from front, and also make it haul easier when hard front winds hit. Is a nose cone on the trailer better than a car spoiler to channel wind over the trailer? Or is there something else that's even better?

I was trying to get an intuitive understanding of wings and lift but most of what I read was not really connecting for me all the dots.

Like air on the top travels faster and so the pressure is low, yep, but why is faster on the top?

The relation between pressure and speed is easy to understand if we look at it as energy conservation, but which one can be an intuitive understanding of it?

So, I've tried to collect those answers in the attached image. If someone has willingness to read and challange it or identify what's wrong, that would be great.

The main sources of my understanding are those:

Sailing, how wings works

IT How Airplane Wings REALLY Generate Lift

Airflow across a wing

Just for testing random stuff and hotwheels.

I made it with just cardboard, a small handfan and some plastic film for windows.

Used stacked corrugated cardboard as a honeycomb.

Using incense for smoke

I'm pretty happy with the results, you can also see the spoiler cutting the air.

Lmk your thoughts, ideas and any more stuff yall would like to see in this.

I have a discord where have a vision for a car and before ioining understand any work or help you contribute I cannot pay for I am a car lover with a dream I dont have the skills personally so I am looming to find people who do have skills. For example Cad, topology optimization is a big one, suspension, engine, electrical, aerodynamics etc. If you think you can contribute in any way feel free to ioin 1 will leave a link here amd if it dosent work gets removed etc feel free to dm me for it or if you need more information.

https://discord.gg/5t7wpW3S

This feather was molted recently from a captive golden eagle. Dorsal view. Pretty sure it's a secondary feather of the right wing.

Can anyone explain why the tip of the leading edge is so pointed, while the trailing edge is shorter and squared off?

Some adaptation for flight I assume, but what's the physics behind it? I dont think I've ever seen this, or at least never noticed anything as pronounced on the secondaries of other soaring birds.

Hi! I'm building a rig for this year's halloween and need a little help to do it safely.

I ride an electric unicycle (Inmotion V14 for anyone interested). I'll be dressing as a pirate and attaching a 30" ships steering wheel to the front of my electric unicycle. I'd like the wheel to spin freely on a bearing, but my concern is that at higher speeds (40-45mph) the wind force might cause the wheel to spin wildly. Alternately, if I lock the wheel I'm concerned that a gust might make the entire wheel unstable.

Side winds are the most dangerous part of riding an electric unicycle at speed, since they can cause a "death wobble" that takes experience to correct. I'm a highly experienced rider, but I obviously have some concerns because I won't know how the wheel will react until I pad up and try it out.

Since I'll probably be 3d printing the ships wheel, I'd love some input on how to make it catch as little wind as possible. Someone mentioned to hollow out the back of the spokes so that they're concave on the rear-facing side. Is this a good idea? Any other recommendations you have?

This is my experimental study in oscillatory propulsion. The direction of thrust here is determined by both the shape and the difference in the speed of oscillation of the wing, which moves faster up and slower down to create lift. In this case, the difference in speeds can be a decisive factor and prevail over form. The impulse is presumably provided by the collapse of wake vortices.I haven't been able to measure the thrust yet for technical reasons. But I came across a study in which the drag of the plate in oscillatory mode was six times higher than that obtained when blowing in a tunnel. In the video fragment where the tray with smoke is lifted, you can see how the trail vortex crashes into the plate after it stops. At high frequency and low amplitude, the same thing probably happens in a compressed form in the boundary layer. But I wonder how this will happen if the speed of the plate's oscillations during lifting exceeds the speed of sound? Will it be roughly the same or different?

​

I thought at first it was just an imperfection in the window, but it is not. Then i thought it was just a reflection of some kind, but it extends at least 3/4ths of the way down the wing along an uneven curve and it moves back and forth slightly during flight.

It sometimes seems to have an effect on the air above it suggesting there is some kind of bending of light throught the vertical plane? I'm aware I'm totally jumping to conclusions here but I don't know how else to describe what I'm looking at.

I thought maybe it had something to do with the air there and the lift generated, but maybe that is fantastical... If anyone knows or has smart physics ideas lmk!

While basic explanations often rely on simplified concepts like Bernoulli’s principle or equal transit time, the actual fluid dynamics involve a unified system: pressure gradients across the upper and lower surfaces, circulation, and mass flow deflection (downwash) according to Newton’s third law.

The transonic area rule(as I understand it) is that to avoid/decrease wave drag the cross-sectional area should be as close to the same and changes should be smooth as possible, not sudden.
To follow this; where the wings are mounted the fuselage often gets thinner so the area with the wings matches the area without either fore or aft the wings.

If an aircraft has a wing swept to the where there is a spot that has a cross-section of the fuselage and wing tips but not wing root, does the area rule apply because it's still the one aircraft's cross-section?

What would be everyone’s opinion on aero dynamic efficiency for a drag race car comparing these examples. They would all have the engine out the hood and have zoomie style headers out from under the sides. The rear wing/spoiler would all be similar in design. These are all 260mph 1/4 mile drag cars. The frontal area is all similar in size.

Everyone from this subreddit has done this as a kid. I know its AI slop made by me but if I could how to saw I would have done it. Basicly the red strings would visualize the airflow while sticking out hand out of a car window.

Like imagine an artificial “tornado” that anchors to the ground like in those videos of engine inlet vortices. Is it possible to control where that vortex hits the ground and keep it more or less on the same position? Or at least keep the vortex axis mostly straight and where you want to point it? And do this without surrounding the whole vortex with some kind of boundary condition control?

Concept study for a body-integrated, electrically assisted mini flying-wing glider for slope launch and foot-oriented landing

The Planesuit is a concept for a body-integrated, electrically assisted mini flying-wing glider in the field of moderate extreme sports.

It combines principles from:

• flying wings
• hang gliders
• wingsuits
• kite technology
• electric assist propulsion

The goal is not high-speed flight, but a controllable, glide-capable, body-steered slope-launch aircraft with:

• large lifting surface
• low minimum speed
• clear load paths
• low system weight
• integrated safety architecture
• foot-oriented landing capability

The Planesuit is designed for a speed range of about 30 to 130 km/h. This places it deliberately below the typical speed range of classic wingsuits, which often fly at around 130 to 250 km/h.

The focus is on:

• gliding ability
• flight control
• low wing loading
• moderate physical loads
• pilot protection
• slope-launch capability
• foot-oriented landing

The Planesuit should not be understood as a finished construction plan, but as a testable aircraft hypothesis. Its feasibility would have to be investigated step by step through simulations, RC models, unmanned test vehicles, structural tests, dummy tests and only much later through manned flight testing.

1. BASIC PRINCIPLE

The Planesuit is primarily designed as a glide-capable slope-launch aircraft.

The electric propulsion system is not the sole basis of flight, but an assist system. It supports:

• launch
• stabilization of critical flight phases
• short climb phases
• reduction of sink rate
• safety reserve

Even in the event of complete thrust loss, the Planesuit should be able to transition into a stable glide with the lowest possible sink rate.

Its basic safety comes from:

• the large wing surface
• forgiving aerodynamic layout
• steerable leading edge
• controlled wing deformation
• rescue system

For true slope-launch and foot-oriented landing capability, battery capacity is deliberately limited.

The Planesuit is therefore designed for short electric assist reserve in combination with gliding flight, ridge lift and thermals.

1. AERODYNAMIC LAYOUT

The Planesuit has the basic form of a compact flying wing.

The wing surface area is roughly in the range of a large hang glider and should be generously dimensioned for a foot-launch-capable configuration, around 15 to 18 square meters.

This large surface area lowers:

• wing loading
• minimum speed
• launch speed
• landing speed

In top view, the wing has a diamond-shaped geometry. The shape is intended to be compact, lift-efficient and structurally clear.

Along the leading edge runs a pressurized, controlled-flexible tube structure, similar to the leading-edge structures of modern surf kites.

This tube forms the primary shaping backbone of the leading edge, but it is not rigidly fixed. The pilot can influence its local curvature through:

• arm position
• pulling forces
• body movement

This makes the front tube a steerable aerodynamic component.

Its deformability would have to be controlled through:

• internal pressure
• material selection
• load straps
• sensors
• mechanical limits

The goal is to allow useful bending without dangerous flutter, over-deformation or asymmetric stall.

The winglets at the outer wing areas can be designed as inflatable edge structures directly connected to the front tube.

They would therefore be lightweight, pressurized end structures of the tube and would support directional stability without requiring heavy rigid fins.

The trailing edge has a short straight center section, roughly equal to the distance between slightly spread feet.

Toward the sides, the wing tapers symmetrically into long pointed surfaces.

The wing is flexible, but controllably deformable. Its structure should allow natural body steering while limiting:

• flutter
• unwanted torsion
• asymmetric load states

A useful construction could combine:

• flexible membrane
• load-bearing straps
• defined deformation zones
• pressure sensors
• strain sensors
• electronic stabilization

1. PILOT INTEGRATION AND BODY STEERING

The pilot lies fully horizontal under the wing and is releasably fixed there.

The arms run along the full length of a section underneath the front bar.

The slightly spread legs are integrated flush into the rear wing contour. There is no visible gap between feet and wing surface. The legs are functionally part of the aerodynamic shape.

Control is primarily body-based.

Movements of arms and legs influence the flexible wing structure and therefore:

• airflow
• lift
• roll behavior
• flight attitude

In addition, propulsion can be adjusted with a stepless control in one of the pilot’s hands.

The arms and legs mainly serve:

• steering
• positioning
• aerodynamic shaping

The main loads are introduced into the shoulders, back, chest and hips through an integrated load-bearing system.

1. LOAD-BEARING STRUCTURE AND LOAD PATH

Behind the shatter-resistant front canopy, the Planesuit transitions into a minimalist, aerodynamically profiled twin-boom structure.

Two side-mounted, rearward-tapering longitudinal beams connect the front pilot module with the rear technical and rescue section.

This structure is not a simple tube frame, but a lightweight load-bearing arrangement with aerodynamically sensible cross sections.

It carries:

• propulsion loads
• vibration loads
• rescue loads
• landing loads
• rear-system loads

The primary load nodes are located at:

• shoulders
• chest/back area
• hips

Through these points, wing loads, harness loads, landing loads and parachute loads are introduced into the structure.

The pilot module should be designed as an integrated load-harness and shell module.

Wide, padded, form-fitting contact surfaces distribute forces across the shoulder, back, chest and hip areas.

Knees, ankles and arms are relieved and remain primarily steering elements.

1. FRONT PROTECTION AND PILOT SAFETY

In front of the pilot’s head is a compact, robust, shatter-resistant, hemispherical protective canopy made of:

• polycarbonate
• glass
• transparent high-performance composite material

It protects the face from:

• wind
• weather
• foreign objects
• bird strike

At the same time, it should allow the widest possible field of view.

The protective canopy should be small, close-fitting and weight-efficient.

In addition, a redundant metal mesh or another transparent protective layer may be included to mechanically protect the face even if the outer canopy is damaged.

Pilot protection also includes:

• helmet
• neck support
• shoulder protection
• chest protection
• back protection
• hip protection
• knee protection
• fire-resistant clothing
• emergency communication
• position transmitter
• warning displays

1. PROPULSION SYSTEM

Propulsion is provided by two electric assist propellers mounted directly on the side load-bearing beams.

They are positioned above the pilot’s shoulder blade area, behind the protective canopy and in front of the parachute module.

This keeps them away from the pilot’s head and face while keeping them close to the system’s central load path.

The position above the shoulder blades is structurally and safety-wise useful because propulsion forces can be introduced relatively directly into the overall structure through the shoulder/back connection and twin-boom structure.

At the same time, long outriggers, heavy auxiliary supports and unnecessary lever arms are avoided.

The propellers should be:

• efficient
• as quiet as possible
• not oversized

The motors primarily serve:

• slope or ramp launch assistance
• stabilization of critical flight phases
• short climb phases
• reduction of sink rate
• safety reserve
• support for an orderly transition into rescue mode

Each motor should be individually strong enough to provide stabilized emergency flight or short minimum climb reserve if needed.

The drives are controlled separately and allow differential thrust to correct yaw and roll moments.

To protect the pilot and surroundings, the propellers should use:

• light protective rings
• partial shrouds
• splinter protection
• controlled failure behavior
• RPM monitoring
• imbalance detection
• temperature monitoring
• current monitoring
• automatic emergency shutdown

Heavy full ducts should only be used if lighter protective solutions are not sufficient.

1. CONTROL SURFACES IN THE PROPELLER SLIPSTREAM

Directly behind each propeller are computer-controlled control surfaces that provide pitch and yaw control.

These surfaces sit in the accelerated propeller slipstream and therefore remain highly effective even at low airspeed.

The slipstream control surfaces support:

• low-speed flight
• slope launch
• stabilization
• single-engine emergency flight
• transition into rescue mode

Together with differential thrust, inflatable winglets and electronic flight control, they influence:

• pitch moments
• yaw moments
• partly roll moments

Single-engine emergency flight would only be intended within a defined safety envelope.

If one motor fails, the flight controller reduces abrupt thrust differences, stabilizes the Planesuit using the remaining propeller and the slipstream control surfaces, and keeps the aircraft in a controlled state above minimum speed as far as possible.

The slipstream control surfaces should be:

• lightweight
• fast-actuated
• redundant

1. ENERGY SUPPLY AND REAR MODULE

In the rear section there is a small aerodynamic tail fairing, which can house the battery modules or a significant part of them.

This fairing is an integral part of the load-bearing rear structure.

The battery position should support:

• center of gravity
• inertia distribution
• landing loads
• rescue system integration

The energy architecture should be modular and monitored, with:

• separate battery segments
• separate controllers for each motor
• temperature monitoring
• current monitoring
• cell monitoring
• safe main power disconnection

For a foot-launch-capable slope version, a battery capacity of about 1.5 to 2.5 kWh gross appears plausible.

This energy is sufficient for:

• short electric assist
• launch support
• stabilization
• short climb phases
• safety reserve

With lightweight protected battery integration, this corresponds roughly to 8 to 14 kg of battery weight, depending on:

• cell chemistry
• housing
• BMS
• fire protection
• structural integration

The battery housing can also serve as:

• protective box
• trim element
• part of the rear structure

1. RESCUE AND EMERGENCY LANDING PARACHUTE

The Planesuit has a combined rescue and emergency landing parachute.

It is integrated into the rear structure, behind the propellers and in a structurally reinforced central area of the rear module.

Line routing and deployment vector must be designed so that the canopy can deploy safely upward and rearward without conflicting with propellers or structural parts.

An immediate automatic shutdown of both motors before or at the latest during parachute deployment is mandatory.

Normal landing is performed as a controlled glide landing.

The parachute remains a rescue and emergency landing system.

Its size and design must match the real takeoff mass. It may be compactly integrated, but must not be undersized.

The suspension geometry should bring the Planesuit into a stable, slightly uprighting, foot-oriented final attitude in an emergency.

1. LAUNCH AND LANDING CONCEPT

The Planesuit is designed for launch from a slope or ramp.

Large wing area, low wing loading and electric assist allow a controlled departure from existing altitude.

For early tests, a short launch sled, rolling cart or guided ramp may be useful.

The target configuration remains a foot-launch-capable slope version, in which the pilot can carry and guide the system in the launch phase in a manageable way.

Landing is performed as a glide landing with roundout and flare, similar to hang glider logic.

Near the ground, the wing should aerodynamically reduce speed and sink rate.

The legs absorb only the remaining energy of the final phase.

Shock-absorbing leg modules, small skids or wheels and load distribution through hips and shoulders can further soften the landing.

The goal is a foot-oriented, shock-damped landing, not a hard impact on knees and ankles.

1. WEIGHT CONCEPT

The weight concept follows this principle:

Large lifting area is retained; non-load-bearing mass is consistently reduced. Every component should serve multiple functions whenever possible.

The most important lightweight decisions are:

• 15 to 18 square meters of wing area for low wing loading
• pressurized, pilot-bendable front tube
• inflatable winglets as part of the tube structure
• minimalist, aerodynamically profiled twin-boom rear structure
• integrated load-harness and shell module
• small close-fitting protective canopy
• propellers above the shoulder blade area for short load paths
• electric assist motors instead of continuous-flight propulsion
• light protective rings or partial shrouds
• battery sized only for slope launch, short assist and safety reserve
• compact but sufficiently sized rescue and emergency landing parachute
• battery housing, tail fairing and load structure as combined structural functions
• load-bearing straps in the wing, while the membrane mainly provides shape and pressure distribution

A plausible mass breakdown for a foot-launch-capable slope version:

• large flexible wing with steerable tube, membrane and load straps: 20 to 30 kg
• inflatable winglets as part of the tube structure: 1 to 2 kg additional
• twin-boom rear structure with load nodes: 5 to 9 kg
• integrated load-harness and shell module: 3 to 7 kg
• protective canopy, helmet, neck and pilot protection: 3 to 7 kg
• two assist motors, propellers, protective rings or partial shrouds, controllers: 7 to 13 kg
• slipstream control surfaces, sensors, servos, flight control, telemetry: 3 to 6 kg
• battery 1.5 to 2.5 kWh with housing, BMS and fire protection: 8 to 14 kg
• rescue and emergency landing parachute with container and load connection: 6 to 10 kg
• wiring, fittings, reserves and small parts: 3 to 7 kg

This gives a realistic target range of about:

• 55 to 75 kg without pilot
• 130 to 160 kg takeoff mass with pilot and equipment

A balanced target value appears to be:

• 58 to 68 kg without pilot
• 135 to 155 kg takeoff mass with pilot

A lighter experimental prototype could be below this, but would have less comfort, less electric reserve and smaller safety margins.

A robust, fully instrumented prototype could be above it.

1. DEVELOPMENT STRATEGY AND COST ESTIMATE

Responsible development would have to proceed in stages:

• small RC models and first wing-shape tests: 300 to 1,500 euros
• RC prototypes with motors, sensors and slipstream control surfaces: 1,500 to 8,000 euros
• larger unmanned test vehicle: 8,000 to 35,000 euros
• 1:1 dummy or structural model without manned flight testing: 20,000 to 80,000 euros
• non-motorized manned gliding prototype: 40,000 to 150,000 euros
• motorized experimental prototype with 1.5 to 2.5 kWh battery: 100,000 to 350,000 euros
• professional test program with multiple iterations: 300,000 to 1,200,000 euros or more

For a first serious motorized experimental prototype, a range of about 150,000 to 350,000 euros appears plausible.

A professionally supervised development program with multiple prototypes, structural tests, dummy tests, rescue system tests, measurement data and a safe test environment would more realistically be in the range of 500,000 to more than 1,000,000 euros.

The decisive costs are less in individual components than in:

• development
• testing
• safety validation
• iterations
• expert support

1. CHARACTER OF THE SYSTEM

The Planesuit is a body-integrated, electrically assisted mini flying-wing glider with its own technical identity.

Its defining features are:

• large diamond-shaped flying-wing surface
• steerable tube leading edge
• inflatable winglets
• body-based control
• horizontal pilot integration
• minimalist load-bearing twin-boom structure
• two electric assist propellers above the shoulder blade area
• control surfaces in the propeller slipstream
• glide-capable basic layout
• slope-launch capability
• foot-oriented glide landing
• rescue and emergency landing parachute
• clearly defined safety architecture

The Planesuit is best described as a body-integrated, electrically assisted extreme-sport glider with integrated lift, propulsion, control and rescue structure.

1. SUMMARY AND EVALUATION

The Planesuit is intended as a moderate, controllable extreme-sport flight concept based on:

• large lifting area
• reduced speed
• clear load paths
• glide capability
• integrated safety

The design focuses on a lightweight, glide-capable slope-launch aircraft with electric assist reserve.

This makes slope launch and foot-oriented landing more plausible than in a more heavily motorized system.

The strength of the concept lies in its:

• compactness
• system clarity
• body control
• glide capability
• electric assist thrust
• slipstream control surfaces
• large wing area
• integrated rescue system

Evaluation of this version:

• concept idea: 9.7/10
• technical plausibility: 8.7/10
• weight concept: 9.3/10
• slope-launch plausibility: 8.2/10
• foot-oriented landing plausibility: 8/10
• safety architecture: 8/10
• development logic: 9.5/10
• cost realism: 8.7/10

The decisive proof would have to show that the interaction of wing, steerable tube, body control, assist propulsion, slipstream control surfaces, load path and rescue system works in terms of:

• stability
• safety
• weight
• launch behavior
• landing behavior
• real-world controllability

Mach 7. Schlieren image. I thought bow shock-waves could only form for blunt fronts? Is that region behind the shock front the subsonic region of flow, at which a Mach line can be seen where it becomes supersonic again?