# What is Propellers: Definition and 31 Discussions

A propeller is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral, that, when rotated, exerts linear thrust upon a working fluid, such as water or air. Propellers are used to pump fluid through a pipe or duct, or to create thrust to propel a boat through water or an aircraft through air. The blades are specially shaped so that their rotational motion through the fluid causes a pressure difference between the two surfaces of the blade by Bernoulli's principle which exerts force on the fluid. Most marine propellers are screw propellers with helical blades rotating on a propeller shaft with an approximately horizontal axis.

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1. ### I Can Leverages and Propellers Work Together to Create Efficient Movement?

Hello, My first innocent thread. I want to be clarified about a subject that it's hanging around me. Maybe is ridiculous, but I want to know if the force that I applied in center of the propeller (I think it calls "boss") is equal to force applied in edge of the blades to get it move around...
2. ### How do surface piercing propellers work?

We have a new boat, and it has surface piercing propellers. Half of the prop is above (out of) the water, and half is below. I can't quite understand how that actually works or why it would be better.
3. ### Exploring Moment of Inertia & Angular Acceleration for Drone Propellers

Hi, I am building a drone for a school project and I am also looking into how it flies. Recently I have been looking into angular momentum, torque, moment of inertia and angular acceleration. However I am struggling to understand moment of inertia and angular acceleration. If possible please...
4. ### Single and Dual-Rotating Propeller Question

Hoping that someone can explain what the optimum angular displacement between the front and rear propellers actually means here in the following paragraph. It concerns the single-rotation case of the experiment: "Both the eight-blade single- and dual-rotating propellers were mounted in four-way...
5. ### Function for the Thrust of a Ducted Fan

I'd like to design a ducted fan capable of generating 800 N of thrust. Though I can do fairly high level math, I just really don't even know where to start in calculating (or at least relatively accurately estimating the thrust generated by a propeller, particularly a ducted one (as I understand...
6. ### Do surfaces ahead of propellers decrease thrust?

Hi! I have had this question for ages, nearly impossible to find anything on the web. My experiments confused me even further! Its concerning the blockage effects of surfaces ahead of a propeller. For example let's consider the usual dual vectoring propellers on the sides of airshipcars like...
7. ### How Does Changing Propeller Weight Affect Max RPM?

Hello all... I have a question about an engine-driven propeller. While a propeller is being spun, the air resists it and the maximum power of the engine will turn at "max rpm" when the drag from the air interacting with the propeller becomes equal to the torque generated by that engine. Now...
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### Blades/propellers - power optimization - drone hovering

I wonder what is the best figures for blades/prepellers - assuming I am trying to optimize battery life and my main usage for the drone is hoovering. I can not play with the arm length. I do consider 4 blades over 2 blades at the same propeller - not sure if it will help. Any feedback or idea is...
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### Relating propeller thrust, power, and rpm together

Hi All, I am involved in a research project regarding electric aircraft. I've done a fair bit of research into this but am having trouble keeping all the different parameters and how they affect each other straight in my head. Fundamentally I am putting together a model whose parameters I can...
10. ### Why are air plane propellers small?

Why are the blades of air plane propellers thin compared to ship propellers? Why shouldn't air planes use the same blade design?
11. ### Challenges in Implementing McCormic's Vortex Theory of Propellers

Hello all, I have been attempting to perform the iterative procedure outlined in McCormic's textbook (1995) for the vortex theory of propellers. However, I have become stumped when attempting to get tangential velocity relative to tip speed after the first iteration as a part of the equation is...
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### Hello - Introduce Myself - 65 yr old Male who likes to think

I have no letters ahead, behind, beside, above, or below my name, but I do love science - particularly applications of science that may be moving through unchartered waters, I snap out if it and face my reality - that notion had been staring me in the face for much too long of time -...
13. ### One big propeller vs. multiple smaller propellers....

The question is which is better from the efficiency point of view: One big propeller or multiple smaller ones? Or are they the same? My general impression is that a bigger one will have much more better efficiency as if you consider the following points: 1. lift is proportional to the area of...
14. ### Is it possible for "me" to make a hoverbike?

Hi, I saw a video of a guy who made a hover and figured; hey, I should try making one too. I've a general design in my mind. His design had two propellers, one on the front and one on the rear. I wanted to make a bike with more than 2 propellers( assuming more the propellers, greater the...
15. ### Propeller Weight & Number of Blades: Effects on Thrust

Does the weight of a propeller have any effect on the thrust provided? For example, if there are are two propellers of the same size same speed but different weight, would the one with more weight have a greater or lesser thrust? also would effect do the number of blades(faces) have on the way a...
16. ### Propellers on an RC Quadcopter?

Hey forum, So I plan on creating a remote controlled quadcopter and I have a query regarding its propellers' sizes. I read that small propellers require motors with a high KV (RPM per volt), and large propellers need motors with a lower KV. There seems to be a way of determining how to match...
17. ### Concerning the Airfoil of Variable Pitch propellers

Hello, I am not an expert in aerospace engineering, merely a hobbyist so bear with my ignorance. lately I have been thinking of creating my own propeller and variable pitch system using a CNC machine as a longer term goal. This desire arose due to the fact that there are no commercially...
18. ### Can a fan or prop handle high pressure and volume for a 12 inch plenum?

I am trying to figure something out and having a lot of difficulty. I would sure appreciate some help. I have a situation where I will need either a fan or a prop. It will need to build up 10-20 lbs of pressure in a plenum but will also need to be able to provide a constant force a large amount...
19. ### Propellers in a Tunnel: Benefits & Noise Suppression

First off, please allow me to preface this by stating I am a HS graduate with a miniscule physics background, so if this is a stupid question, I humbly apologize. That being said... I have 2 questions, both of which are probably inane. #1. What would be the beneficial effect, if any, of...
20. ### Propeller Speed and Stacked Plane Propellers

My background is electrical engineering, but I have a question regarding the mechanics and physics regarding plane propellers. The purpose of a plane propeller is meant to provide thrust to the plane. Similar to a plane wing, the propeller generates lift but does so in a direction that is...
21. ### How Do I Calculate RPM for a Propeller in a Uniform Water Flow?

hi to all! Say i have a uniform flow of water of 1m/s.. if i put a propeller with known diameter and blade angle...what would be its RPM?...i want to design a flow meter...pls help me!..i need to have basic and approximate formulas on the blade parameters and its RPM..thanks! Regards dioross
22. ### How do waterflow and propellers interact?

hi everyone! need some help about propellers..say i have a fixed mounted propeller and a flow of water with known velocity runs through it.. what would be the rpm of the propeller??.. i know there a re lots of things and parameters to consider... i need some good references, calculations ,and...
23. ### A helicopter flies off, its propellers rotating. Why doesn't the body

A helicopter flies off, its propellers rotating. Why doesn't the body of the helicopter rotate in the opposite direction?
24. ### Anyone know a thing about propellers?

at what diameter, pitch, and blade number would be the best combination for a high speed propeller? i'd like the diameter to be under 8 foot in diameter.
25. ### Differential of propellers for air and water

Is there a way to determine the diameter (or other dimension) differential between a propeller traveling an object through water as opposed to one traveling through air, the hp of the driving motor being equal in both cases?
26. ### Propulsion Help: Seeking Advice on ROV Propellers

Hello Forum. I'm new here, and thought this would be a good place to ask some questions. Currently at my school, we are building an ROV for a competition. I came here to ask specifically about propellers in terms of sizes, and rpm. Last years team entered the competition without any...
27. ### Calculating Lift Force of Helicopter Propellers

Homework Statement A 5400 kg helicopter accelerates upward at 2.17 m/s2. The acceleration due to gravity is 9.8 m/s2. What life force is exerted by the air on the propellers? Answer in N. Homework Equations Fnet=ma The Attempt at a Solution I am making the acceleration positive...
28. ### How Can I Calculate Thrust as an Airspeed Function for Propellers?

Does anybody here knows how can i calculate (or plot) the Thrust as an airspeed function? I guess it'd be something related with Pitch, Diameter, HP, air density... Or... a way to calculate RPM as a pitch, diameter and power function? thanks!
29. ### Why propellers used for cargos

I think my question is obvious :wink: Most of the cargo planes, almost every, use turbo props or turbofans; c 130, c 160, cn 235, a 400 m.. I am wondering that what makes props choosable for cargo planes ?
30. ### Why do the propellers pull an aircraft, but push a ship?

I think that the title of the topic is very self explanatory. I want to know what the explanation is for the different implementations, I reckon that it might have something to do with the density of air and water.
31. ### Calculating Thrust from Propellers for Model Airplane

can anyone tell me how to calculate thrust for a model airplane. i know the propeller size and pitch and also the engine power and RPM. Any help would be much appreciated regards reg_ram