Tips and Tricks for JSail, by Eduard Rodes

This guide aims to help you to get the maximum speed of your sail in all wind conditions.

The first thing we must understand is that there is no magic formula that achieves maximum performance from our sailing. Even more, the correct setting of the sail depends not only on the wind and waves but also on the sailor’s weight and technique.

As every sailor is different, and every day we face different wind and sea conditions, we must understand how the different controls we have on board work and how they affect to the sail to find the perfect combination that will make us faster. The constant adjustment of the sail to the sea and wind changes is the key to maximize our speed.


People tend to confuse power with speed, which is a mistake. A boat should not be compared to a car, where it is usually true that greater power can develop faster speed. A more appropriate comparison would be with a tractor. High power tractors are able to drag large weights, but very slowly. A small, low power tractor is able to go faster, but not moving big weights.


Sailing is more or less the same: for light weights, flatter sails are faster. You need power if you're really heavy, when you need the sail to help you to pass the wave. But that same sail, used by someone light will offer bad results; the sailor will have to hike a lot, will get tired very soon and the boat will go slowly from the begining.


So the RED model should not be used by someone weighing less than 43 or 44 Kg, the BLUE should not be used by someone weighing less than 33 or 34 Kg; and the GREEN has an excellent upwind angle and an exceptional speed for lighter sailors

Now you have the correct sail, let’s check the...


Sprit: The sprit tension is the control that we will readjust more frequently during the race.

Something to consider is that when sailing we have two winds: the prevailing wind and the gusts. We should always adjust the sprit tension to the prevailing wind and when the gusts blow we should see some creases on the sail as if the sprit was not tight enough.

There is something very important that we must know: the sprit is the control that has more influence on the leech. This is very important to understand, especially when we sail in very light or strong winds.

If the sprit is too tight, it will cause an excessive leech tension. This is the worst thing that can happen to us in light winds. Always make sure that in light wind the sprit is quite weak. Even a small fold due to being too loose could improve the speed at extremely low wind conditions. This is why it is so important to adjust the sprit when we change from going upwind to reach or downwind and vice versa.

In case of strong winds, when it’s difficult for us to keep the boat flat, we should reduce the sprit tension in such a way that appears a big and permanent fold on the sail, as if it was divided into two halves. The look is not very elegant, but the sail works perfectly in all directions. Just relax and… enjoy the speed you'll get from this! However, if that happens too frequently you should ask yourself if a less power model wouldn’t be better for you.

Vang: It keeps the leech tension when the gusts make us ease the sail sheet or when we go downwind and the sheet does not work vertically. When we go windward it often doesn’t have any tension... in this case the leech is controlled by the main sheet.

In case of medium/strong winds we tight the vang enough to keep the boom to the correct height even when we ease the mainsail in the gusts.

Out haul: Controls the sail foot tension and controls the depth of the sail, specially in the lower part. This is a control that we'll use frequently when we want to optimize our boat speed, both upwind and downwind. It can be easily adjusted while sailing and it is a superb tool to set the sail depending on the conditions we have to face.

Recommended tension: When the out haul is loose, the vertical folds shouldn’t exceed the first seam of the sail. In flat waters it is preferable to tighten a little more the out haul to have better upwind angle. When it is difficult to keep the boat flat, in strong wind conditions, we must tighten the out haul to flatten the sail.

Rake: This is a really very important point. The boat behaviour depends entirely on it and it is worth it to pay a special attention to it. When we prepare the boat to go to the water you should have an initial rake of about 286 cm (measured from the upper rear mast to deck edge above the rudder fittings). Sprit and vang must be absolutely loose to avoid mast bending.

We will do the final adjustments in the sea in the following way:

  • e must be sailing upwind with the wind coming from starboard to avoid the sprit interferences. We are sitting down and hiking as we will during the race, (depending on the wind go more forward or aft, hiking a lot or sitting almost no the dagger board...) The boat must be perfectly flat, not hilling at all (remember that the maximum speed going upwind is always like that).
  • All the controls (vang, sprit, out haul, cunningham) must be correctly adjusted to the current conditions and the wind tales perfectly oriented. When everything is ok, leave the rudder to see what happens. If the boat goes luffing too quickly we must move the mast forward. If, by contrast, the boat wants to go downwind, we must decrease the rake of the mast. Repeat this operation until the boats luffs gently. This is the balance we want.

It should be done before each race.

In case of soft winds the correction will be very little, but in medium or strong wind days will need to pull the mast quite forward to compensate its bending, which produces that the sail centre moves aft. We must maintain the initial balance in any wind conditions, and that is only achieved by modifying the rake in the described way. It should not give us fear having to give many turns in the cockpit. The only target is the balance.

Sometimes, just for pure curiosity, when we go back to the shore, we use the measurer tape to check the rake we were sailing with and we can have a surprise… If the boat was going well, that was the correct rake at that time (which does not mean that it will work the same in the next regatta, even in very similar conditions… wind may have changed, different waves, different clothes... it has to be readjusted again). We must give the necessary rake in any condition of wind, it has to work always the same, keeping the balance; the rudder should never be too hard.

In case of really strong wind, when we have serious difficulties to keep the boat flat, we will reduce the rake until you get a reading of 279 - 281 cm and we will ease the sprit to produce the crease we mentioned earlier. But also in these conditions will be follow the same process described here to find the balance.

The sail height limiters:

Higher: It controls the sail height. In case of low wind the sail must be as high as possible (without touching the upper limit of the measurement stickers); in case of strong wind the sail should be as low as possible (without touching the lower limit of the measurement stickers).)

Lower (or cunningham): It controls the luff tension. The luff tension must be proportional to the strength of the wind. The cunningham, which has to be always installed, has to be adjusted in the following way: from no turns to maximum 3 turns. The ratio is as follows: with little wind, more turns cunningham; when the wind raises and we have to hike to keep the boat flat, 1-2 turns. When we have to depower the sail, 0 turns.

With 0 turns the luff must be very tight, but not enough to produce a “wave” just after it. It is preferable that the rope which controls it is long enough to be adjusted to this point every day

Main sheet: This not only determines the sail angle, but also has a huge influence on the leech when we go upwind. This means that whenever we sheet in or ease it, we adjust the sail angle against the wind, but also change the leech tension.

You must control the sail at all times and react to the gusts trimming the sheet. When the gusts reach us we must ease a little the mainsail in order to increase the speed and we sheet in again when we have the speed to go higher.

Sail ties: Another important point. We must understand that the mast will bend and this can affect negatively the sail. We can avoid it by using the following process:

1st Fit the sail as always but leaving all the mast ties loose except the top and the goose neck ones, which must allow a distance of about 2-3 mm between the mast and the sail (never less than this). The boom ties must allow a distance of 10 mm between the sail and the boom.

2nd Tight the out haul to the end and tight the sprit enough to allow you to tight the main sheet a lot (a short distance between the boom end and the aft deck) without wrinkles on the sail.

3rd Once in that position simply fasten the ties keeping the distance between the bending mast and the straight luff (which has to be straight in all wind conditions). If at any point the distance between the sail and the mast is more than 10 mm, shorten the distances of the top mast and gose neck ties and do it again.

In this way we allow the mast to bend as much as it needs without altering the sail shape, which simply would depower the sail and make it slower when passing the waves.

It is not necessary to readjust the ties to different wind conditions... If you follow the mentioned process correctly the ties will allow the mast and the sail work correctly at all times.


The fine sail tuning needs to be done while sailing, when we know the real wind and waves conditions. You can readjust the out haul, the sprit, the vang, the rake and the cunningham. We must ensure that the boat has enough power to pass the waves as we need, that it has the correct upwind angle... We can get it testing and testing until we have the boat in race conditions. The wind tale at the leech will tell you if it is too tight. If it hides downwind it means that we must do something to open the leech: loose a little the vang and/or the sprit, tight the out haul… You should see it 60% of the time

Preparation according to wind/waves conditions

Light wind (0-8 knots) with no waves:

On flat waters, we want a sail that can make us go very high. As we have no problems with the waves, we want to transform all the power of the sail in capacity to go upwind.

Luff tension: It should be loose. 3 laps at the cunningham. This will give us a flat sail in the front area and better angle to windward.

Out haul: Although the wind is light, in flat waters it is better to have the out haul a little tight. Flatten a little the sail in these conditions will reduce the sail drag, improving the flow of the wind. This will also improve our upwind angle.

Vang: In light airs it should never work in upwind course. The vang should only be set to maintain the shape of the leech only when sailing downwind.

Main sheet: The main sheet will control the leech tension upwind. We should constantly adjust it in the gusts. When we ease the main sheet the leech gets open at the upper section, and when we tight it the leech closes.

The proper trimming will keep the best leech tension and will also give us the best twist for that condition. Tightening it in excess will close the leech and will reduce dramatically the boat speed. Not tightening it enough will make the leech be too open, and won't let the boat go so high as it could.

Soft wind with waves:

When the waves become bigger, it is important that the sail increases its power. When the boat passes a wave there is a speed decrease. We need the sail to retrieve it quickly: we need acceleration.

Out haul: We should now start to ease the out hole to enhance the sail and get more acceleration, which will work better on and after the wave.

Luff: A little more tension on the luff will pull the sail power centre forward, which will help us to pass the waves and accelerate after them. We still want a loose luff because too much stress on it would flatten and depower the sail. 2 turns of the cunningham rope.

Main sheet: It is important to trim it constantly to ensure that the boat sails as high as possible and, at the same time, accelerates when the waves reduce our speed. Don't forget that by doing this we open and close leech, which must give us the correct power at all time.

Medium winds (9-17 knots):

When the wind increases we have to tighten sprit and vang. We still need all the power of the sail for the waves. In this kind of conditions it is always good to remember that we cannot go high if we are not going fast.

Out haul: The out haul must be set according to the wave conditions. The smaller waves we have, toe more we can tighten it. The bigger the waves are, the looser it has to be. The sensations we have onboard are very important to determine the out haul need. If the boat has trouble to pass the waves, we can try to ease a little the out haul. If our boat sails lower than others but we have good speed we can tighten it a little.

Luff: If we sail without waves, some small horizontal creases starting in the luff could work make our boat go really fast. But if the waves are big, this does not help us at all. One turn on the cunningham rope.

Vang: In these conditions it is very important that we have enough tension on the vang, both to keep the leech tension during the gusts and for downwind courses. If we don't have enough vang tension, we will see how the upper part of the leech opens, and the sail loses power.

Strong winds (18 and more knots):

More power than we need. In these wind conditions, our top priority is always to keep our boat flat when we go upwind. To flatten the sail will help us to achieve it.

Out haul: The tension will depower the sail. The more wind we have, the more we will tighten it.

Cunningham: Even in extreme conditions, when we want the sail as flat as we can, don’t remove the cunningham rope. If you did it the vang would no longer work correctly and will open the leech in the downwind courses. 0 turns on the cunningham rope.

Sprit: If we have already tightened the out haul and the luff, and yet we cannot keep the boat flat, we can substantially ease the sprit, creating a large fold on the sail from the top of the mast to the end of the boom, as said above. This will open the leech and will significantly reduce the sail power.

Vang: A well trimmed vang is essential to accelerate and plane when the gusts arrive. It is also very important because it gives stability to the boat on the downwind courses, helping us to surf the waves, and to jibe much more easily.

Remember that in case of real difficulties to keep the boat flat, even after trimming all the controls for these conditions, you can lift the dagger board about 15 -18 cm, which will be very helpful. But this is to be done only if all the rest is not enough.

Get 100% of your sail:

Are we getting the most out of our sail?

As we mentioned earlier there is no magic formula to prepare a sail. Then, how can we know if we prepare perfectly the sail for the different conditions? The evidence is the answer. The best and the only way to see if your sail needs adjustments is testing your boat speed with other sailors who have a similar level. It is very important that during the tests, the changes are introduced one by one and tested several times before the next change. If you introduce several changes at the same time you will never know which of them have really affected the speed.

So we must train and do all the tests we can before every race with all the sailors we can. This will lead us to maximum speed and will prepare us for the race.

Good luck!

Eduard Rodés

 29er National Coach

 JSail importer for Spain