Mast extensions

Extensions, mast extensions or the way we decide to call them, are one of the most important accessories to rig our sail properly. Have you ever put the wrong extension in the car? Took the RDM when you needed an SDM, or a 15cm when the sail require a 24cm. No one can be proud of calling himself a windsurfer if never had a mishap with his extensions.

If you are here it’s because you surely need one and it’s our goal to solve your problem. Not only will we offer you a good selection of them, they will be sorted by type, size and materials.

RDM – Carbon – 30/36cm

RDM – Aluminium – Several sizes

SDM – Aluminium – Several sizes

Some tips to help you choosing your mast extension

To choose your windsurfing extension, you must take into account the mast diameter, the range of sails for which you will use that mast and which luff those sails have. Then you must choose the material based on the rest of the components of your gear.


We have two options for the diameter:

  • RDM (Reduced Diameter Mast) also known as skinny
  • SDM (Standard Diameter Mast) also known as fat

The mast is what define the whole set since the extension or extensions we choose must have the same diameter the mast has. Also keep in mind that the sail is designed for one type of mast or for the other. Normally, modern sails requiring smaller masts than 460cm, are designed for RDM and the sails requiring bigger masts, freerace or slalom with cambers, design them for SDM.

Sail range

Normally, we use the same mast for several sails, and for that we must use an extension that allows us to adapt the length of the mast to the one required by each of them. This measure will usually be found in the sail itself under the description “luff”, and is the measure of the curve that goes from the top of the sail to the downhaul. If you want to know more about how a sail works, I recommend you visit this article that details it.

Medida del ExtensorSome sails clearly have detailed the mast length and the extension they need, otherwise you must subtract the measure “luff” to the measure “mast”.
In the example of this sail, the luff is indicated at 475cm and then indicates that the appropriate mast is 460cm. Therefore the extension that we must have for this sail is 15cm. It is also noteworthy that the sail here specifies that it is designed for SDM.

With which we already have all the data!!! An SDM extension greater than 15cm, for this sail I would definitely choose the North Uni XT SDM

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