Glossary Of Terms


Inside Foil

A classic fin configuration traditionally involves a fully symmetrical centre fin together with half foiled side fins (with a flat inside face).

However the performance of a fin is not only measured on its outline or template but also on its foil characteristics. Correctly designed these foil characteristics enhance the performance of the board by reducing drag and generating optimum lift. This is where inside foil technology really comes to its own as it reduces water flow distortion (drag) and improves hold and speed, all in all making for a smoother more powerful ride. 4WFS offers inside foil technology on a number of fins across all material types.

Kite Surfing

These foils are particularly recommended for use in directional kite-surfboards. Note that high-density installation blocks should be pre-installed in all kiteboards to provide additional support. Refer to the maunufacturers installation instructions for more information.


New Foil

These are the latest additions to the range.



Quad configurations can vary greatly depending on personal preferences. We’ve indicated some of the more popular quad fin foils here for ease of reference.


Speciality Foil

Those fins are more unique in nature or are used in specialist configurations.


Twisted Foil

Twisted Foil Technology (TFT) takes “Inside Foil Technology” to a new level altogether. TFT combines the benefits of the latest in Inside Foil Technology with a more complex double sided curvature. Twisted foil fins display a strong upright base with an accentuated splay towards the tip, whilst at the same time harnessing the benefits of a complimentary clean inside foil and progressive inside twist that maximises laminar flow and lift.

The result is a foil that seamlessly integrates drive with turning power making for a smooth yet powerful ride.TFT foils are only available in the fibre glass and hexalight range and are limited to the 4Z, 4MK and 4Q1 signature series.


Fin FlexFin Flex

Fin flex refers to the degree by which the uppermost section of a fin flexes relative to its base. Fin flex is an important characteristic particularly as it is an active contributor to the boards ability to accelerate through turns. Generally fins possessing a lower degree of flex are more responsive with a greater degree of accuracy in the timing of the acceleration. Fins that are characterised by too much flex tend to be sluggish in their response and may lack drive; conversly fins that offer no flex whatsoever are characterised by a lack of responsive acceleration through turns.

Fin Terminology


Fin Terminology

Click on the image on the right to view an explanation of the terms used for foils.



Rail-To-Rail Transition

It is rail to rail movement in surfing which generates speed as a board traverses along a wave. When a board is “catching” rails it traditionally focussed attention on the boards bottom edge. However improving rail to rail transition is equally possible by increasing side fin splay outwards towards the rail.



The board feels unresponsive and sluggish as its dynamics are at odds with surounding water flow.



The feeling of “holding” in the face of the wave but with accelerated forward momentum off the bottom and top turns.


Foot Positioning

Correct foot positioning is fundamental in maximizing a board’s potential. With thruster fin set-ups it’s more beneficial for the surfer to have their rear (back) foot positioned behind the 2 front side fins, usually the front foot is around 1/2 way up the board and back foot more or less above the centre fin.



“Hold” is similar to “Drive” but the effect of the term is that the board doesn’t “drift” or “slide-out” on bottom & top turns.



This refers to powerful breaking waves (doesn’t necessarily mean big) but usually “tubing”.



The board feels very responsive and actually too responsive: can even slide/drift off bottom & top turns.



The board doesn’t want to project forward, no matter how hard you push, the board seems to delay its response.



The requirement to create speed is directly linked to a board’s responsiveness. Usually the more responsive the board is, the quicker it is to get speed.



The board is difficult to turn and requires a lot of effort to perform.



Some surfers have an aggressive approach to riding waves and their movements look erratic whilst others have smooth flowing approaches. Wide or narrow foot stances and body positioning and the manner that each surfer approaches riding a wave and their corresponding style, plays a large role in a board’s performance.


Turning “Tight” in the Pocket

This is when the surfer wants to execute their manoeuvre in the most critical section of the wave.


Weak/Flat waves

When the waves have no power and seem “gutless”.