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Thank you for choosing North Sails for your Optimist. This tuning guide has been designed to help you get the best out of your North Optimist sail.

North sails provide two radial sail designs to suit light/medium P4 and heavy sailors P5. There are also three cross cut designs for the light XM 08, medium DZ6, and Heavy CZ5 sailors.

The sail tuning principles apply across the range of sails, use the tuning guide as a start and then refine it to suit your style making your own personal guide.

Which sail is best for me?

Onshore Set-Up

Sail Ties

Getting the sail ties right is very important, especially on the mast. If one tie is too tight compared to the others it creates a hard point on the sail and upsets the natural luff curve that is built into the sail. Make sure the ties are tight so that they do not slip, and then tie a half hitch around either side of the reef knot to ensure it does not come loose.

Mast ties

Asa start, set the mast ties so that there is a 1mm gap between the frontedge of the sail and the mast. Make sure that the top tie is tiedtight, as there is a lot of tension here pulling the sail from the mastwith the sprit. If it is too loose there will be a tension line runningfrom the sail tie below it. The main tie at the bottom of the mast canbe eased about 5mm to allow the tack of the sail to sit cleanly abovethe boom.
Fig.1 Head tie too loose.

The diagonal tie at the top of the mast is very important and will control where your sail is on the black bands. In light/ Medium winds set the tie so that the sail is towards the top of the black bands. In strong winds especially if you are light set the sail so it is towards the bottom of the black band.

There are two schools of thought as to whether the sail ties should be adjusted on the mast. The first and easiest is to leave the mast ties for all conditions. In light winds the mast does not bend therefore keeping the sail ties equi-distant will make the sail slightly fuller in the luff and easier to steer to. In medium winds the mast will bend and the luff curve on the sail will match the mast bend. In stronger winds the mast will bend slightly more than the luff curve on the sail, however this is not a problem as we want to loose
power anyway.

The other theory is that the sail ties should be eased slightly at the top and bottom of the mast in light wind to compensate for the mast not bending. About 8mm then gradually tighter and tighter to a 1mm gap in the middle. In medium wind the ties should be tied evenly which will match the luff curve to the mast bend. In stronger winds, especially for heavier sailors the mast will bend more than the luff curve, therefore the top and bottom of the mast should be tied tight and the middle eased about 4mm.

If you want to point more and flatten the entry of the sail ease the top and bottom mast ties.

If you want a deeper entry to the sail ease the middle mast sail ties and go slightly

tighter at the top and bottom. 

Boom ties
Tie the boom ties so that there is an 8 mm gap all the way along the foot, remember that the ties cannot be looser than 10mm. At either end of the boom tie the ties tight in a breeze (1mm gap) and slightly more eased in light wind (4mm gap).

Mast Rake

Pull the mast back (without bending) when measuring the mast rake as this will be the position the mast will be in when sailing upwind. Notice there is a certain amount of movement fore and aft which is good as it allows the mast to rake forward slightly for downwind. Make sure the mast is tight sideways, or power from the rig will be lost.

Raking the mast forward moves the centre of effort forward and very slightly higher, meaning there is less feeling on the rudder and there is more power. Going forward also means that you sheet down the leech more so you have to be careful in light winds not to close the leech.

Raking the mast aft gives more feeling in the rudder and reduces power slightly.

As a rule set the rake;
109-110 inches for very light (0-6 knots and flat water)
1’11-1’12 for medium (7-14 knots)
1’12 - 1'13 for breeze (15 knots plus, if heavier you will be able to keep the rake further forward in
strong winds)

If you don’t want to adjust go 1’10 ½-1'11 for sailors less than 37KG and 1’12 for sailors heavier than this.


There are a variety of masts to choose from. Generally the heavier you are, the stiffer the mast should be and vice versa. McLube the mast so that the ties rotate freely and do not stick.

Fig 2. Luff too easedFig 3. Luff too tight
Preventer (luff tension)
The luff tension needs to be set to less in light winds (more twists) and tighter as the wind increases (less twists). In light winds when sailing the luff tension should be only just tighter than creases being visible from the mast ties. As you get to sitting on the side beginning to hike take more twists out, up to max tension in the breeze. As a guide three twists in the light to no twists in the breeze. Set the luff tension so that you only just remove the horizontal creases coming off the mast ties.

In light and medium winds the leech tension on the main will mainly come from the mainsheet tension. Therefore the kicker needs to be set for downwind sailing. The leech should be able to just flick open as the boat goes over waves. As a general rule of thumb the top batten should be parallel to the boom, if it is outside this it is too tight, if it is inside this it is too loose.

In strong winds you need to get the kicker almost as tight as it will go. Do this by sheeting the main really hard and pulling the kicker tight.

4. Outhaul not tightened5. Outhaul not tightened6. Outhaul tightened7. Outhaul tightened

Out Haul

The outhaul has a major effect over the shape of the sail, especially in the bottom half. This should be calibrated and settings recorded so that when you find settings that suit you, they can be reproduced. In very light winds and flat water the sail needs to be slightly flatter to help the air flow over the sail. In these conditions you can tighten the outhaul so that wrinkles are removed from the foot, keep tightening and stop just before a tension line parallel with the boom starts to appear. In medium winds ease the outhaul so that wrinkles just begin to appear perpendicular to the boom. As the wind increases and you start to get overpowered go increasingly tighter on the outhaul (see figures 4, 5, 6 & 7).

Fig 8.Sprit too tightFig 9. Sprit too easedFig 10. perfect Trim


The sprit is a major control over the leech tension of the sail and hence the air flow andthe power. If it is too tight wrinkles appear from the top of the sprit parallel with the sprit (figure 8). If it is too loose wrinkles appear from the clew to the top of the mast (figure 9). It is better to have it slightly too loose than too tight! In light winds slight wrinkles are good from the tip of the mast to the clew as this will help open the leech. In medium winds the sprit can be a little tighter so the wrinkles are just gone, only appearing in gusts. When you start to get overpowered it is possible to ease the sprit slightly, it doesn’t look nice but will help to depower the sail. Remember don’t depower the sail just so you do not have to hike as hard. In powered up conditions the harder you hike the faster you will go! Downwind especially in light and marginal winds ease the sprit slightly to get the most out of the sail, no creases equals fast here. Practice tensioning and de-tensioning the sprit so that you don’t lose ground while carrying out the adjustment (figure 10 shows the perfect trim).


The mainsheet is one of the most important controls you have over the sail. As a guideline the sheet should be trimmed so that the boom is just over the back corner of the boat. As long as you are not overpowered, in gusts you should sheet in a little tighter (about 1 inch of main) and in the lulls/ waves ease very slightly to keep the boat moving. Work hard on getting a feel for the boat and how it is going through the water. If you are too tight on the main the boat will feel slow and sticky, too loose and you will not be able to point. In light winds look for the leech tell tales flying about 90% of the time. In medium winds the leech tell tales should fly about 70% of the time, in strong winds you will find they fly most of the time! In strong winds once you start to get over powered and you are having to ease the sheet out of the back corner of the boat, it is time to depower the sail, first of all outhaul, then sprit. Keep a tuning diary each time you go sailing so that you can reproduce fast settings. The Optimist is a tweaky boat and to get the most out of your North sail it is important to be on top of the settings.

Good luck on the water!


Contact the Optimist Experts: 

Vince Brun

(619) 226-1415 Work
(619) 251-1737 Mobile
(619) 224-7018 Fax

Tim Healy

(401) 683-7997 Work


David O'Connor

+61 02 9998 8500 Work
+61 421 540 002 Mobile


Juan Carlos Romero

(410) 212-5303 Work