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Windsurf Masts

Jorren Eggenkamp at

A mast is just a stick that keeps your sail upright, right? Not really... It's quite literally the backbone of your rig.

The first point to be aware of is that your mast matters. The mast forms the backbone of your gear. The forces from the sail, vibrations from the board, and sailor effort are all linked through the mast. A mast that is a poor match for your sails and/or your own preferences will limit your enjoyment and hold you back.

So, the mast matters – that makes sense. But how to make sense of all the jargon and options that are available? You need to know some of this to avoid buying the wrong mast. Here we give you the information you need.

On this page we keep things simple. We give advice, and outline the theory behind mast bend curves, response, and construction. After reading this article you should be able to make a well-informed mast choice and purchase wisely.

Of course, we also recommend speaking to your local dealer for expert advice and service.


It is good practice to follow the mast type and length recommendation of the sail manufacturer. So the first step is to take a look at the specs printed on your sail or sail bag. A safe choice is to buy your masts and sails from the same brand, as the sails were developed around those masts. But many sail brands use similar mast specs, so mixing and matching across brands is often a possibility. Also, you may consider buying an independent brand (yes, such as Unifiber!) which often works just as well and is more budget-friendly.

Our MAST SELECTOR will help you to make the right choice. The specs are based on the averages from all the brands we’ve measured over the past seasons. You can never record enough data and we’ve measured a lot of masts over the years! The result is a reliable tool that we and our customers have full confidence in.


The key elements to consider when choosing a mast are:

  1. Carbon content
  2. Bend Curve
  3. Stiffness

First, let’s look at carbon content.


Most masts have a carbon content that varies between 30% and 100%. This influences the following factors:

  1. PriceCarbon fibre is expensive, so this gives high carbon content masts a heftier price tag.
  2. Weight. Higher carbon content means less weight. And if you have less weight to move around, that means your sail is easier to control.
  3. Response. The higher the carbon content the more responsive and direct your rig will feel.
  4. Durability. The downside of carbon fibre is that it is quite vulnerable to impact. So if you have a 100% mast, you should be extra careful not to drop it on the street or smash it on rocks. This will cause tiny cracks in the material that lead to weak points in your mast.

Fundamentally, a mast is made from two material types: fibres that give strength and stiffness, and the resin that keeps the fibres together.

Windsurf masts use epoxy resin; and most manufacturers use a mix of carbon and glass fibres. The carbon content is defined as the ratio between carbon and glass fibres. The epoxy is not taken into account. So '100% carbon' means that the mast consists of only carbon fibre and epoxy, and contains no glass fibre.

Unifiber offer three grades in carbon content:

  • ESSENTIALS C50: a budget-friendly and strong mast
  • HD C75: A great mix between durability and performance
  • ELITE C100: Light and responsive. Uncompromised performance.


The Bend Curve represents the shape of your mast under load. The luff curve of the sail should correspond with the curve of the mast. Each sail brand uses its own bend curve. 

To describe the bend curve, masts have tended to be placed in one of three categories:

  • Hard Top
  • Constant Curve
  • Flex Top

A hard top mast has a relatively flexible base and a stiffer top. The flex top has a relatively stiff base and a flexible top. Constant Curve lays in between. The average stiffness is the same for all bend curves. And note that even for a hard top mast, the base is still stiffer than the top.

Each category represents a small range of different curves. So two brands that use Constant Curve masts have similar, but not necessarily identical bend curves. When you combine a mast and sail of 2 brands from the same category, you can be confident that the fit will be at least good enough to work.

Do you want to know how masts are measured and how the different bend curves are defined? We explain all about that in our article MAST MEASUREMENTS.


Through our countless measurements, we noticed that not all brands stayed true to their own bend curve. Some brands have shifted over the years. The trend over the last years is that all brands are shifting towards Constant Curve masts. Some lean towards Flex Top. Hard Top is as good as extinct. 

For Unifiber - independent mast producers - this created a dilemma: Should we just make one bend curve that works 'well enough' in all sail brands?

We thought about it but decided to stay true to our beliefs. The convergence in currently used bend curves means that we have been able to make three new bend curves that are a perfect fit for the vast majority of sail brands out there today. We carefully analysed the leading producers - about 80% of the market - and made the perfect masts to fit their sails. This is the result:

  • Constant Curve - This is the most commonly used curve profile (also for smaller sail lofts).
  • Constant FL Curve - This is similar to the old "flex top" mast, but with more flex low down (around the centre) of the mast. FL = Flex Low.
  • Constant FH Curve - This is also similar to the old "flex top" mast, but there is more flex high up. The centre section is relatively stiff. FH = Flex High.

Take a look at our new MAST SELECTOR to see which bend curve fits your sails. This should give you enough information to choose the correct bend curve. If you're curious and want to know more about the bend curves, the new developments and how we came to our new bend curves, we tell all about it in our BEND CURVE ARTICLE

Below diagrams are a representation of the three curves. The curves are exaggerated to show the differences. 

Note that the 'old' bend curve classification is still a relevant method. But it is no longer precise enough to identify differences between the masts used by major brands. 


If you use multiple sail brands with the same mast, there is a good chance that some combinations will be far from optimal! These pointers will help you to decide if the compromise is tolerable. 

Mast is a little too much flex top

  • Looser leech resulting in a lack of power
  • Battens come closer to the mast, so flipping the battens might be harder
  • Centre of effort moves downwards 

Mast is a little too much hard top

  • Tighter leech -> less control in gusts
  • Flatter profile -> less power
  • Centre of Effort moves higher 

For planing and powered up windsurfing, a little bit too much flex top is usually easier to live with than a little bit too much hard top. Note that we specifically say "a little bit too much" flex or hard top! If your sail is rigged with a mast that has a very different bend curve - whether too much flex top or too much hard top - the sail's intended profile will be lost and it will perform in a substandard way.

Want to know more? In our BEND CURVE ARTICLE we explore this topic in more detail.


The IMCS value indicates how much your mast bends under load. A lower IMCS indicates a more flexible, or 'softer' mast.

Most mast manufacturers adhere to the more or less normalised stiffness for each mast length. E.g., 400 masts are often made at 19 IMCS, 430s at 21, 460s at 25 and 490s at 29. Hence longer masts are made stiffer than shorter masts. Unifiber also follows the above IMCS values per given mast length.

Since almost all manufacturers use the same IMCS values, you don't really have to pay much attention to it. But you could use this knowledge to your advantage:


Stiffer mast:

  • More power
  • Fuller profile
  • Better for heavier riders
  • Good for flat water sailing 

Softer mast:

  • Less power
  • Flatter profile
  • Softer feeling
  • Better for lighter riders
  • Adds control

Changing the stiffness and or Bend Curve of masts is possible in a number of ways. For example, by extending the top or bottom of the mast; or even cutting the mast.

This is a very easy and practical way to soften your rig:

Extend the bottom section part of a shorter mast with 30cm extra extension. For example, a 430 mast with 30cm extra extension becomes a 460.

The result will be a 460 mast with (approximately) the stiffness of the 430 mast.


In 2021 Unifiber introduced the Universal Ferrule System. All Unifiber masts have now identical ferrules (the part that connects the two mast halves), regardless of size, bend curve or carbon content.

This provides some advantages:

  1. If breakage does happen then only the broken section needs to be replaced. That's good for your wallet and for the environment and puts an end to the problem of orphaned sections cluttering your flat/garage.
  2. You can mix and match masts of different bend curves. For example: combine a light-weight Elite C100 top with a more durable HD C75 base.
  3. You can fine-tune bend curves. Combine two halves of different bend curves, which will create a new bend curve. We're still researching this feature. In time we will provide the results of each combination so you can choose your perfect combination. In the meantime, feel free to experiment. 

In theory, it is also possible to combine mast halves of different lengths. But we strongly advise AGAINST doing this. Since each length has a different stiffness, combining different lengths will lead to extremely non-standard bend curves, which are not suitable for any sail.



Unifiber masts give unbeatable value for money, performance and durability thanks to a consistent pre-preg manufacturing process and a high-quality surface finish.

Unifiber offers 82 different mast choices in carbon content, diameter and 3 different bend curves to match almost any sail. We are simply the most versatile and inclusive mast brand and a worldwide expert on mast measurements.

More about masts:

Our knowledge base contains a lot of info about a lot of different topics. Click here for an overview

Check the Unifiber Mast Selector
To choose the correct mast for your sail