Surfing Explained: Ep6 Nose & Tail Shapes

Over the next two episodes (6 & 7) of Surf Simply's animated exploration of surf science, we explore how the different characteristics of the nose and tail shape alters the performance of wave suitability of the surfboard.

This episode was written and animated by Surf Simply Coach Will Forster.

Season 1 will cover 5 episodes over the next 5 weeks:
Ep1: Understanding Speed and Grip
Ep2: Generating Speed and Grip
Ep3: What is Surfboard Volume
Ep4: Using an Online Volume to Weight Calculator
Ep5: The Function and Physics of Fins
Ep6: Nose & Tail Shapes - Part 1 Nose

Transcript:
The outline has a profound impact on the way a board functions, and where its strengths and weaknesses may lie. And when I say outline, I literally mean what would remain on the floor if I took a sharpie out and drew around it.

For the purpose of analysis, we are going to split the board in half, and in this episode talk about the front half of the board while in a future episode we will examine the remainder of the board, as they do slightly different jobs, at slightly different times.

The front half is at its greatest influence during paddling as it's where our shoulders and chest might lay, where as once we’re on our feet we mostly surf from behind the midway point. It is also the first point the oncoming water flow will contact our board, and in the same way a car or aeroplane needs to efficiently move through the air with as low drag and turbulence as possible, a surfboard does too. In fact a surfboard has to pass through two different densities of fluid; water under the board, and air over the board. But for this episode let’s stick with the water.

From nose to tail a surfboard acts as a hydrodynamic foil, so we need to consider how the board is affecting the water flow as the board is moving. For a foil to work at its most efficient, we’re are trying to achieve as much lift as possible, while limiting drag and turbulence. This combination will allow our paddle speed to reach its maximum, and allow us to catch waves earlier with less effort.

The surfboard shaper might increase or decrease the shape and volume of the nose, depending on the users specifications and surfing level. And to understand these differences, we need to talk about the functions of differing nose shapes and their effect on drag.

There are two types of drag; frontal drag and form drag. Frontal drag is the point of which the nose of the board, or car or airplane first cuts its hole through the fluid. Form drag is everything behind that, like our heavy bodies laying on the board or the rest of the surfboard itself.

The upsides to giving the surfboard a nice sharp point is that with less frontal drag the board can cut its way through the water when paddling. Plus, once up and riding a small nose reduces the swing weight of the board, allowing the rider to turn the board faster or with less energy, whilst also lowering the chance of the rail catching during the turn by simply removing a lot of the material upfront.

The downsides to having a sharp pointy nose is that the narrower the nose, the less surfboard and volume and buoyancy there is lifting our heavy body parts out of the way, so increasing the overall drag, and higher drag means a potential lower paddle speed, and because of this we might have to compensate in other ways when selecting our waves.

For example, a performance shortboard surfer with a narrow nose might need to take off on a steeper wave where the gravitational potential energy can be converted to kinetic energy faster. This can be demonstrated when comparing two children slides of the same height, with one being steeper than the other. Even though the height of the slides and GPE is the same for both kids, it is obvious the child on the steeper slide will reach the bottom of the slide quicker. This allows the surfer with more drag to compensate for having a slower paddle speed.

In contrast, a surfboard that has a wide nose with lots of surfboard underneath the chest, is able to provide more lift, making it less necessary to compensate using a steeper wave. Hence why longboards or specifically designed small wave boards with their wider noses and higher volumes can normally take off earlier on less steep sections of waves.