Narrowboat in the Cut: Squat, Return Flow and Towpath Power

What Is Squat?

Squat is a phenomenon where a boat's draft (depth of submersion) increases as it moves through water due to the displacement of water by its bow. This effect can be significant in narrowboats, especially when navigating through locks and cuts.

The increase in draft can reduce the clearance under bridges or over shallow areas, posing safety risks if not managed properly.

Return Flow and Its Impact

When a boat passes through a lock or a narrow section of waterway, it creates a wake that moves backward. This return flow can cause additional challenges for the boat, such as increased resistance and potential instability.

Understanding how to navigate these flows is essential for maintaining control and safety during transit.

Critical Speed: The 4 mph Limit

The critical speed of a narrowboat is often set at around 4 miles per hour (mph) due to the increased risk of squat and return flow effects. Exceeding this speed can lead to significant safety issues.

This limit ensures that boats can safely navigate through various waterways without compromising safety or causing damage.

Comparing Diesel Engines with Towpath Horses

Historically, narrowboats were often pulled by horses on towpaths. Comparing the power output of a diesel engine to that of a horse helps in understanding the efficiency and practicality of modern propulsion methods.

While diesel engines offer more consistent and powerful propulsion, they also require maintenance and fuel, whereas horses provided natural and sustainable energy.

Frequently asked questions

Try it live

Everything above runs in your browser — open Narrowboat in the Cut: Squat, Return Flow and Towpath Power and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.