Sail tuning is one of the skills that gets overlooked during the learning process of windsurfing. Most people can kind of rig the sail correctly but are either unsure, or just plain don’t know how to tune a windsurf sail. A badly tuned windsurf sail can make the experience of windsurfing unpleasant. There are only a few parameters you really have to look out for, depending on the sail. This guide should help for most windsurfing sail types although it will vary (or be missing aspects) for sails that have cambers for example.
When I rig my sails there are basically three things I look out for.
How to Tune a Windsurf Sail Correctly
Before I start, a quick disclaimer. Each sail type and brand will have different properties and their performance will vary greatly from one sail to another. This guide should be used to start you off but ultimately it is up to each sailor to test out variations to this starting point to see what works best for them. You can also check out the manufacturers websites to see what they recommend for their sails.
With the sail on the ground I push down on the sail with both hands. The sail foil should be just touching the boom on the other side. If it touches too easily I tense the outhaul more, if it doesn’t reach the boom I release some outhaul.
This also depends on the wind. If the wind is light you can release the outhaul a little to make the sail curve more round. If the wind is stronger or you feel overpowered you can tense the outhaul more to make the curve flatter so the sail doesn’t pull as much.
Too much outhaul
If we pull too much on the outhaul, the sail will be very flat, which means that it will lose the profile. This means that all the advantages of having a wing shape are lost and all you are left with is a wall for a sail.
For vey strong winds this can help take some power out of the sail so that you can get back to the beach but the performance is greatly compromised. It is also not very good for the life of the sail.
Not enough outhaul
If we do not pull enough outhaul the sail will have too much of a curve. This is bad for two reasons:
Firstly, we will not be able to go upwind as much as the angle of attach when on a close haul is steeper.
Secondly, the battens will not be able to change the side of the mast easily. If they don’t change onto the lee side we have a bad sail profile which is not efficient. And if they have to be passed on to the other side with a lot of force, the end of the batten sleeve will wear out fast and there will come a moment when you have the batten poking out next to the mast.
The leech (the outer edge of the sail between the mast top and the end of the boom) should be loose up to about the 3rd batten starting from the top (for wave and ferried sails) and until nearly the batten just above the boom (for slalom sails).
The reason for the loose leech is that the wind is faster the higher up you go. Therefore the angle of attack of the sail has to adjust to the different apparent wind at that height. That is why slalom sails (which are usually bigger and higher) need more loose leech.
Another benefit of the loose leech is that the sail is less rigid which means that in gusty winds it is less aggressive to catapult you. You control the loose leech with the downhaul.
Too much downhaul
If we pull the downhaul more than is necessary, we will have a long loose leech. This greatly reduces the effective sail area which reduces the power that we can get out of the sail. This is OK if we want to use a sail that is too big but obviously, going down a sail size might be a better solution.
However, sometimes we only have one sail, or our next smaller sail is too small and the only solution is to play with the tuning.
Not enough downhaul
When we do not tense the downhaul enough we leave the mast too straight. One result is the wear effect that we have with too little outhaul mentioned before.
The other reason for making sure we put enough downhaul on the sail is that, with a flat sail the pressure point is unstable. With every movement of the sail it seems to wander around. This is really uncomfortable for relaxing in the harness.
Aside from that, the lack of loose leech also means that the top of the sail contributes to the active sail surface, bringing the sails pressure point higher. This results in the sail being more prone to catapult you.
The first batten above the boom should be at about 1/3 or 1/2 of the mast width. The reason for this is that I have found that it works best for air flow performance and also allows the battens to change sides when going into the other direction. This is controlled with the downhaul and the outhaul.
One last tip
In terms of altering the aspects of the sail, keep in mind that you want to get the downhaul set correctly before you mess around with the outhaul as it has the greatest impact.
Windsurf sail tuning
By now I hope you will have realised the importance of having the sail tuneed correctly. With these guidelines you should be off to a good start. I recommend you test different settings and see how the performance of the sail is affected.
If you have any questions regarding tuning the sail, let me know in the comments.