# Factors affecting the design of an efficient paddle wheel

• paddlewheel99
In summary, a student is undertaking a physics project to investigate the factors affecting the design of an efficient paddle wheel. The factors considered so far include the number, size, and shape of paddles, as well as the rotation speed of the paddles. The student has decided to keep the hull shape constant for all designs. Through research, it has been determined that the motion of a paddle wheel boat follows the law of conservation of momentum, with the paddles pushing water in the backward direction to propel the boat forward. The goal is to design a paddle wheel that maximizes forward motion while minimizing energy expenditure. The student is seeking input on the physics aspect and constructing an experimental model. Some considerations for the model include the paddle shape, submersion
paddlewheel99
I'm a student undertaking a challenging physics project. My project is based on the Factors affecting design of an efficient paddle wheel.
Until now the factors i could think about are:
-Number of paddles
-Size and shape of paddles
-Rotation speed of paddles
Since my object of study is paddle design, I have decided to keep the hull shape constant for all possible designs.
After doing heavy research and study I have understood that the motion of a paddle wheel boat will obey the law of conservation of momentum. As the paddles push the water in the backward direction, the boat would be propelled forward as per the above law. An effecient paddle wheel would be one that translates into maximum forward motion for a perticular amount of energy spent.
I would appreciate your inputs on
1. Explanation on the physics aspect
2. Constructing a experimental model

paddlewheel99 said:
I'm a student undertaking a challenging physics project. My project is based on the Factors affecting design of an efficient paddle wheel.
Until now the factors i could think about are:
-Number of paddles
-Size and shape of paddles
-Rotation speed of paddles
Since my object of study is paddle design, I have decided to keep the hull shape constant for all possible designs.
After doing heavy research and study I have understood that the motion of a paddle wheel boat will obey the law of conservation of momentum. As the paddles push the water in the backward direction, the boat would be propelled forward as per the above law. An effecient paddle wheel would be one that translates into maximum forward motion for a perticular amount of energy spent.
I would appreciate your inputs on
1. Explanation on the physics aspect
2. Constructing a experimental model

What paddle shapes have you found so far in your research? What have you found so far about the difference in efficiency between a paddle wheel and a propeller?

Consider the diameter of the wheel.

how much it is submerged underwater.

hint: less submersion is more efficient but slower

hint: less submersion is more efficient but slower

Why would this follow? The paddle wheel is only doing useful work when it is submerged. More submersion should be necessarily more efficient; this is one of the principle advantages of the (fully submerged) screw.

It's no different than paddling a kayak manually. You maximize efficiency by submerging the entire paddle. Sure, submerging half the paddle let's you move the oar more quickly, but you move less mass, generating thrust less efficiently. Velocity is bad (wasted energy), momentum is good (pushes the boat forward).

''What paddle shapes have you found so far in your research? What have you found so far about the difference in efficiency between a paddle wheel and a propeller?''

Actually my only aim is investigating factors affecting design of paddle wheel (to make it efficient) I will conduct all the experiments later, first i want to get all the physics theory and hypthesis in order.
It is correct that the more you submerge the paddlewheel in water, it will become more efficient. Which i did not think of, so i would have to keep this factor constant, right? The material of the paddlewheel and paddles should also be same?
Now i am confused, can anyone suggest me what should be my research question (it should ideally be narrow) Mine so far: Investigation of the factors affecting design of a good efficient paddle wheel, or should i investigate only one factor which will allow me to write atleast 4000 words.
Also:
Newton's Laws of Motion, namely his third law which essentially states that for every action (a) there is an equal and opposite reaction(r) . In this case the paddle wheel is (a) and movement of boat is (r). What other forces would act on the boat?
Can anyone give me more physics behind this topic in terms of:
rotational motion, angular speed, torque, etc.
Will the angle or something come into play? (i am confused about this part)

Last edited:
Well, with a flat paddle, as the water is pushed it is compressed and will tend to roll to the sides and away from, a flat paddle.
A concave paddle will also compress the water, but tends to "hold" more water volume.
Consider this "l" versus this ")" or this "]"

Curl said:
less submersion is more efficient but slower
talk2glenn said:
Why would this follow?
The obvious case is if the paddle wheel is completely submerged, then it only generates a torque and no net linear force, since you have equal and opposing forces on the paddles opposite from each other on the wheel.

For partial submersion, there's some ideal point where the paddles don't waste too much energy pusing water downwards at entry, and upwards at exit. Too little submersion and the paddles don't move enough water.

pallidin said:
Well, with a flat paddle, as the water is pushed it is compressed and will tend to roll to the sides and away from, a flat paddle. A concave paddle will also compress the water, but tends to "hold" more water volume. Consider this "l" versus this ")" or this "]"
A "V" shaped paddle would have an issue with slowing down a boat, not sure if it's more efficient in forrwards mode.

Just trying to study the relationship between angular momentum and the linear momentum for the paddle wheel. Will all the angular momentum be transferred to linear momentum, can there be any equation linking it (specific ref. to the paddle wheel)

All the angular momentum might not be transformed into linear momentum.

Since you are studying efficiency of paddle wheel out of curiosity I would like to know how to work out the efficiency percentage of paddle wheel. In many boat design forums they mention the efficiency in terms of percentage. How to calculate this percentage.

Can your paddle wheel have a shroud?

kryptic3k said:
All the angular momentum might not be transformed into linear momentum.

Since you are studying efficiency of paddle wheel out of curiosity I would like to know how to work out the efficiency percentage of paddle wheel. In many boat design forums they mention the efficiency in terms of percentage. How to calculate this percentage.

I imagine it would be the usual output/input power, where power = F*V.

rcgldr said:
The obvious case is if the paddle wheel is completely submerged, then it only generates a torque and no net linear force, since you have equal and opposing forces on the paddles opposite from each other on the wheel.

For partial submersion, there's some ideal point where the paddles don't waste too much energy pusing water downwards at entry, and upwards at exit. Too little submersion and the paddles don't move enough water.

A "V" shaped paddle would have an issue with slowing down a boat, not sure if it's more efficient in forrwards mode.

Articulating blades?

mender said:
I imagine it would be the usual output/input power, where power = F*V.

So if we want to calculate input power do we derive force value from torque. Also what velocity do we consider. Should it be velocity with which water is pushed back.
I hope someone clarifies this power and efficiency calculation.

Phrak said:
Can your paddle wheel have a shroud?

I don't think having a shroud will help. It will make the project even more complicated. It would be better to stick to calculations of power.

talk2glenn said:
Why would this follow? The paddle wheel is only doing useful work when it is submerged. More submersion should be necessarily more efficient; this is one of the principle advantages of the (fully submerged) screw.

It's no different than paddling a kayak manually. You maximize efficiency by submerging the entire paddle. Sure, submerging half the paddle let's you move the oar more quickly, but you move less mass, generating thrust less efficiently. Velocity is bad (wasted energy), momentum is good (pushes the boat forward).

The difference is that, with just one kayak paddle, you waste time getting back to the beginning of your stroke. With a wheel, you can arrange to have at least one paddle in the water all the time. And there would be a limit to the practical size of a kayak paddle.

I could ask why it has to be a wheel. What about paddles mounted on a belt which dips into the water and then takes each paddle back along the whole length of the ship? Losses due to entry and exit would be reduced significantly. Never had those on the Mississippi, did they?
Lots of maintenance problems though.

Okay, so now i want to study one factor related to paddles in detail: no. of paddles, or shape of paddles or rpm of paddles. Which factor do you think i should study, which will allow me to give detailed argument and discussion on physics concepts

Last edited:
paddlewheel99 said:
Okay, so now i want to study one factor related to paddles in detail: no. of paddles, or shape of paddles or rpm of paddles. Which factor do you think i should study, which will allow me to give detailed argument and discussion on physics concepts

I would think that the number of paddles might be a good place to start.

I forget if we covered this already, but an even better project would be to compare the efficiency of a paddlewheel to a propeller, given the same power input...

paddlewheel99 said:
Okay, so now i want to study one factor related to paddles in detail: no. of paddles, or shape of paddles or rpm of paddles. Which factor do you think i should study, which will allow me to give detailed argument and discussion on physics concepts

Honestly I think you should study classical mechanics and fluid dynamics first, then you'll be able to solve the paddle wheel issue on your own.

The benefit is that you can use your physics knowledge for the rest of your life as well as for this project.

## 1. What is the purpose of a paddle wheel?

The main purpose of a paddle wheel is to convert the energy of flowing water into mechanical energy, which can then be used to power machinery or generate electricity.

## 2. How do the size and shape of the paddle affect efficiency?

The size and shape of the paddle are important factors in determining the efficiency of a paddle wheel. A larger paddle will be able to catch more water and generate more power, but it will also create more drag. The shape of the paddle can also affect the amount of drag and the efficiency of the wheel.

## 3. Does the speed of the water affect the design of a paddle wheel?

Yes, the speed of the water is a crucial factor in designing an efficient paddle wheel. The faster the water flows, the more energy it can transfer to the paddle wheel. Therefore, the design of the paddle wheel must be able to withstand high water speeds and efficiently convert that energy into mechanical energy.

## 4. Are there any other factors that can impact the design of a paddle wheel?

Yes, there are several other factors that can affect the design of a paddle wheel. These include the material used to construct the wheel, the angle at which the paddles are positioned, the number of paddles, and the spacing between them. All of these factors can impact the efficiency of the paddle wheel.

## 5. How can the efficiency of a paddle wheel be improved?

There are several ways to improve the efficiency of a paddle wheel. These include optimizing the size and shape of the paddles, reducing drag by using streamlined designs, and using lightweight and durable materials. Additionally, regularly maintaining and cleaning the paddle wheel can also help improve its efficiency.

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