Surf Science: Surfboard Tail Shapes

Sep 17th 2019

Surf Science: Surfboard Tail Shapes

In this week’s Surf Science 101, we break down the basics of tail shapes.

To put it simply…wider tails offer more stability and float, and will give you a faster planing speed. While, narrower tails are going to make rolling from rail to rail a little easier. They can also help hold a board steadier on a steeper faced wave.

The shape of the tail’s edges make a difference too. A tail that has rounder angles or no angles at all, is going to help you ‘hold’ the water for a little longer. This means that you will have more control of the board.

When a tail has harder angles, more water will “release” and you will have a looser, more snappy feel to the board. These are best for smaller, more punchy waves.

Finally, a rounder tail is better for a more open face wave with a little more size and carving potential.

The Breakdown of Surfboard Tail Shapes

Basically there are around 5 or 6 main tail shapes. But there are an unlimited amount of variations of each. Some shapers even blend these basics together creating even more options.

To start, the main surfboard tail types are squash tail, square tail, pin tail, round tail, swallow tail and asymmetric tail. In this great article from Surfline’s resident design-o-phile Nick Carroll, he breaks down the pros and cons of each tail:

“Imagine water encountering a surfboard. First — before it comes into contact with the board — it’s free to move. Then, bang! It runs into, or is run into, by the board. Friction slows the water’s passage beneath, around and past the board (hydrodynamic tests show the water moves slowest halfway along the object with which it’s come into contact). Then, as it approaches the tail, the water sniffs freedom. Yesss! It accelerates out and away.

Here’s what that tells us: water is moving at its quickest at the beginning and end of its journey past our board. And thus, the board’s outline is most like to have its greatest effect on waterflow at those beginning and end points.

Thus! The tail shape is a seriously important piece of the surfboard’s overall design.

Here’s a very crude series of explanations of the effects of the basic tail shapes on waterflow, and how they affect a board’s performance.

a) The SQUARETAIL. Water moves straight off the rail line, which is cut off, boom, just like that. It also moves abruptly straight off the square edge behind the back fin. The squaretail gets rid of a lot of water very quickly, which makes it a very fast tail shape; but since the water’s all dumping off a straight edge with no modulation of the flow, the squaretail tends to turn awkwardly in “jumps” from rail to rail, with little subtlety in between. The squaretail also permits a wider tail, preserving volume well behind the forward fins, which helps flotation. WK believes this shape suits a beginner surfer or one who’s experimenting with short, wide boards for small waves.

b) The SQUASHTAIL. This is an adapted squaretail, with some of the benefits of quick release and width for flotation, but the rounded curves off the rails provide some subtle modulation in turns. A “tradeoff” tail, well suited to a wide range of surfers in most waves between two and eight feet.

c) The PINTAIL, or round pin. Water moves off the tail and rails in a diffuse fashion, in a wide range of angles. Since it has a lot of options in that nice curve toward the final pin, the water takes more time to break free. Thus the pintail doesn’t have the raw acceleration of a square or squashtail, but what it lacks in off-the-mark speed it gains immensely in control and subtlety of turning angles, and the generally narrower immediate tail area fits better into barrels than either square or squash. A common tail shape among elite pros, particularly in surf over six feet.

d) The SWALLOWTAIL. Referred to as a “double pin” by at least one of its pioneers (Bob McTavish), the swallow blends a square’s instant rail fall-off with some of the pin’s tube-fitting and turning subtlety. Swallows release concave bottoms better than most other tail shapes and also allow a wider tail shape, which makes ’em popular among some high performance surfers in the nitro-small-wave hotdogger range.

e) The DIAMOND is a largely superseded attempt to soften the square’s hard edges and preserve some of its release speed. Its job is now done more effectively by the SQUASH. “

We hope this give you a little background when you pick out your next board. You can always stop in the store and ask our expert staff what works best on our local breaks or what would be the best choice for your next surf trip.

More Surf Science and Surf 101 articles,coming soon:

Why some breaks are better than others?

Why do waves break?

Glossary of Terms

How to Duck Dive

How to Wax a Surfboard

September 17, 2019 — Cheyne Cottrell