Help Needed: Calculating Canoe Resistance for Mechanical Engineering Project

Hello everyone,

As a mechanical engineering student, I am in search of an appropriate method to calculate the resistance to forward motion of a canoe, similar to the one depicted in thes pictures I will attach. I would greatly appreciate any guidance, advice, or methods that you could share to assist me in tackling this challenge.

I plan to measure the dimensions of the canoe and assess the wetted surface area. For analysis, I've heard of the waterlines method, but I am open to other suggestions. Your expertise would be invaluable.

Thank you in advance for your help!

 

Calculating that resistance is fraught with a bunch of variables. You can calculate the wetted surface drag with a limited degree of confidence. The surface itself causes some differences. A perfectly smooth surface and one that is less smooth. Your textbooks may lay down some numers that you could use for that part of the calculation.

Dynamic drag is a whole other deal. That depends on the configuration of the displaced area and more influentially on the velocity of the boat through the water. Reynolds numbers, Froude numbers and other combinations of variables make the sum of the drag somewhat difficult to predict. Sea state also plays into the puzzle.

 

Thank you, sir, for your response. Actually, I didn't specifically study naval construction in school, but I stumbled upon this project by chance, so I need to learn everything from scratch.
I tried using the MaxSurf software, and the result I obtained was not convincing because, for different calculation methods within the software, it provided very different values.

 

Calculating the resistance is the Holy Grail of Naval Architecture. There are some rules of thumb (approximations based on existing models) that can let you know if your numbers make sense. However, software is of not much use unless you have the knowledge to interpret the results. Are you doing this as a personal challenge or is it a school assignment?

 

Thank you for your response. Indeed, this is a school project I am working on. Your advice and expertise would be greatly valuable in this endeavor. Do you have any suggestions on how I could proceed with this task? Your assistance would be greatly appreciated.

 

Thank you for your response. Indeed, this is a school project I am working on. Your advice and expertise would be greatly valuable in this endeavor. Do you have any suggestions on how I could proceed with this task? Your assistance would be greatly appreciated.

 

Are there other projects you can do instead of this? It is difficult even for Naval Architects with expensive software. You should check form drag vs surface friction. The ratio change with speed and depends on the shape. Also, on a boat, the trim (longitudinal angle) has a huge influence in drag. If this project was assigned to you and gives you not choice, try to narrow the scope of the study. What is the description of the project?

 

Do you really believe it?. I know it's not like that. Maybe it's that you don't know what the profession of naval architect entails. You should consider them a little better.

 

That's correct, since there are many variables and without validation, how will the user know what is correct and what is not!
It requires a degree of investigation and critiquing that maybe beyond the user.

Well, this poster agrees with Gonzo's HERE and HERE, or have they changed their mind simply to provoke an argument?

To summarise:

Sounds like an agreement to me!

 

Indeed, this project has been assigned to me. The goal of the project is to design the propulsion transmission system for the mentioned canoe. For this, I need to evaluate the power required for propulsion at a given speed. By understanding the resistance to movement, we can determine the necessary power. This will allow me to initiate the mechanical design calculations.

 

Ousmane,

Hello, welcome to the Forum.

Do you have a final weight loaded and making way?
Find yourself a very similar hull, match the weight and tow it with a scale.
Measure your resistance at different speeds, plot the data on a graph.
You will be within ~5% accuracy.

Are you in Mali?

 

When you say "school" ...as language, and definitions are often country dependent, what age group are you referring to here?
As this shall also help how to provide guidance.

 

Not enough parameters are specified!

Are you required to mathematically calculate the power required, or is it allowed to be done experimentally as proposed in post number 11?

Why do you need a transmission, lots of boats around do not use them at all by compensating with propeller design and engine type, size, torque, and RPM? Is it a fossil fuel, electric, Steam, Etc engine propulsion? Is it required to use water/air propellers, or can some other method be used, like oscillating fins, Paddle Wheel, rowing mechanisms, rope tows, etc?

Does it have to be efficient, fast, or both? If foils can be used that might simplify the calculations, but that is not shown in the pictures?

 

I just need to assess the power, regardless of the method, unless it doesn't require too much time and resources.
Here are the results I obtained using MaxSurf with the Holtrop method. I'm wondering if the power obtained in this way reflects reality.

 

The results don't reflect reality. On the low end, the graph would have to be expanded to read it. However, at 16 kmh it shows it requires about a 60 kW engine, which would not fit on a canoe. From experience, in a 30' (9.1m) canoe with 8 people and some gear, a 4HP (~3 kW) outboard propelled it to approximately 6 kmh in flat water. I believe a canoe may be outside the parameters of the software.