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The advantages of a wide mainsheet track, and how to use it.

More and more we see good performance boats emulating the top race boats* by fitting a mainsheet traveler.  So what are the advantages and how should we use it ?   

* Note that full-foiling boats do not need wide tracks as do the non-foiling race boats. This is due to the fact that at the much higher foiling speeds, their apparent wind direction varies very little.  So while they still use a track, it does not need to extend beyond the sides of the main hull.

With a traveler, your lower mainsheet block will be attached to a traveling slide with rollers on the sides to engage in the track.

You need this to roll easily, so first a note; keep the track sides clean and you might want to occasionally spray it with silicon for low drag, though in a dusty environment, this may also mean cleaning it more often too ;-)

There will be blocks and cleats at each side with either a 2 or 3 part tackle to pull the traveler to the position you want.  Mainsheet systems with a strop will only permit the lower mainsheet block to go out about the width of the transom at best and the same with mainsheets that are blocked down to each transom corner.    A wider track offers more ability to pull the boom down vertically to flatten and straighten the leech which is more efficient in the most common moderate wind range.  This is particularly important for multihulls, when apparent winds are higher.

Some tracks are straight but these are a compromise as the mainsheet can only pull down vertically over a range of boom angles IF the track is curved, to be always closely under the mainsheet boom block.     With a straight track, there is always a compromise for the sheeting.  Outboard, the track may be too far to the rear, when the mainsheet will be pulling the boom from the mast, or if too far forward near the centerline, the boom will experience compression on the mast that can cause excessive mast rotation with a rotating mast or potentially damaging compression on gooseneck fittings.

A curved track generally avoids these issues and fast racing trimarans can have them wide enough to permit keeping vertical mainsheets as much as 40 deg out from the boats centerline, for full control of leech tension and twist over a wide range of sailing angles and wind strengths.  Here is an early maxi-tri IDEC that not only had a very wide traveler track with a rear beam curved to suit, but I also just noted it shared a drop down spade rudder like the W17!  These huge boats use their tall, fully battened mainsails more like a rigid wingsail that rotates about the mast.  Twist is negligable but the leech load is high.   The traveler control lines are then used more than the mainsheet, controlling the angle of attack while the sail holds a semi-rigid shape via mainsheet tension. 

This highlites one of the main advantages of the curved track that other mainsheet systems just cannot match ... the ability to pre-set any (or zero) twist for the current wind conditions and then leave it set while the traveler is adjusted to suit the attack angle and boat heading.  This assures the best overall mainsail trim and efficiency.

Later IDEC models also showed-off a wonderfully wide track with the mainsheet winched down hard, with sail angle of attack controlled by the traveler position.  (Hard to argue with her efficiency as she is the fastest ocean racer on the planet, holding the Jules Verne circumnavigation record since 2017 at just under 41 days.   In 2025, she will try to break that .. but with an all-female crew skippered by Alexia Barrier).

But back to reality now.  For smaller boats, there will always be a compromise and curved tracks are then a rare luxury, so the W17 trimaran is quite unique to enjoy one.  It does come with 'quite an added chunk’ to the cost of outfitting though … but for me it’s worth it for the added control and efficiency.  (Installing the Barton ‘box’ track that you can bend yourself, offers a healthy savings over the Harken option, especially when pre-bent track shipping of the latter is factored in).

So how should we use such a traveler?

As it is basically to allow the best leech tension and twist for the conditions the boat is sailing in, we need to discuss what these are.

Let’s start with the most common moderate wind conditions of say 5-15 kts (though this range may vary somewhat with different boats)

For the typical multihull, this most common mid-range requires high power with high pointing ability and typically this is achieved with a straight, flat leech sheeted down just to leeward of the centerline.   Again, how far to leeward varies with different boats with the W17 seeming to work better with the traveler out vertically over the transom corner, about 12”(300) off-center.

If you bring it farther to windward the sail can stall.  Adding telltales to the leech will allow you to visually see this … you want those leech telltales to be flying straight aft.    (Which reminds me:  when I was learning to race among quite a few dinghy (mono) experts, they would often repeat to me ... "If in doubt, let it out")

If you have the traveler farther out, you will lose some power and pointing ability, although speed can be marginally higher.  It should be noted however, that when sailing a wiggly course in and over waves, that a flat sail with no twist is at risk of stalling as its not practical to keep changing the boom angle to suit the constantly changing course.  In this case, a little twist allows more of the sail to be effective so is generally needed when sailing a wiggly course over waves.

So what about in lower winds?  First of all, we need to slacken off the clew and push it forward to give more sail camber … particularly low down where wind speeds are lowest.   But high camber is at risk of stalling, especially as the variation of the apparent wind from the deck to the mast top is highest in low winds.  So to counteract this, we need to allow a little twist in the sail and this comes from applying less down-load on the boom.  To achieve this we bring in the traveler but ease off on the mainsheet itself.  This allows the boom to swing up and for the leech to fall off higher up.  But as we can see from this diagram, the twist required from wind gradient variation is not high.

In high winds, we may be ‘on overload’ so now need to depower the sail.  This is also possible by removing the down component of the mainsheet, but in this case, we do not bring in the traveler but we can let it out a little and then just ease the mainsheet for the top of the leech to fall off.  Newer sails with square tops achieve this more easily as the extra area at the top now has a leverage aft of the mast that will twist the upper sail to leeward as that part has a couple of battens, keeping it quite a stiff panel.

 When sailing somewhat off wind, we can keep the mainsail nice and flat to the wind with the traveler fairly far out but with the mainsheet quite hard down.   This is efficient and fast.   But again, if we need to depower we can ease off the traveler and then the sheet.  But if we need to play the boom angle for gusts or change of sailing angles, just playing the traveler will be more efficient on a curved track, rather than easing the mainsail that allows twist that will lose power.     (While playing with such sail adjustments, it's also very important to make small tiller adjustments simultaneously, so that the speed is kept up as far as possible.  Accelerating a slowed boat takes time and your average speed will definitely suffer).

So you can see that organizing your boat to be able to readily move the traveler even under load, can add to improved performance and control.

It’s never a good idea to have TOO much twist especially downwind, as then you add power to the head of the sail that will roll you side to side. A flatter sail (made possible by a circular track) will make for a steadier ride.

Although this might be considered another subject, adjusting the tiller of a rotating mast can also factor into this, as when going downwind, you can add considerable more power with more mast angle, as this then works as a vertical end plate to the sail.  But also, you can DE-power the sail when sailing on a deep reach by removing the mast rotation and adjusting the tiller to place the mast straight or even have the mast nose slightly to leeward.  Of course, you can only achieve this if your mast tiller control lines are independent of your boom, which is typically the case when there is a flat cabin top or deck to arrange the mast tiller tackles.

When gybing with a stable multihull, it's common to use the track control lines to bring the traveler to the centerline.   You can then sheet in the mainsheet bringing the straight tensioned leech near the eye of the wind and then a small movement of the tiller will drop it over to the other tack and the new windward control line can then be let out to absorb the slight shock.  This is much safer and more controlled than the wild gybes one often sees on monohulls, so choosing to gybe instead of tacking in certain conditions is a much more common event on a multihull than on a mono where the knockdown often causes the boat to broach.

Here is one half of the Barton track on a W17. The doubled line coming towards the camera is the 2:1 control line tackle that limits how far out the traveler can go.  There is one each side and to prevent them from falling in the water when slack, there is a small trapezoidal net held up with soft wire hooks, to catch the control line.   It’s light and effective.

Having explained the advantages of a wide traveler, one may ask why more boats do not have them ?    Monos only have a narrow beam to mount them, so the gain would be small compared to use on a multihull.  But generally, it's a lack of space plus the extra cost that persuades a builder (private or pro) to compromise performance perks and use something simpler.   A higher percentage of multihulls have them though.

My associate Andre Baetz thought it would be handy to add a set-up procedure for those using a track for the first time.

Here is how Andre sets up his Farrier using his own traveler.                                                                               

  Good practice for main sail trim using the traveller and the sheet:    [by AB - Aug 2024]

Having given the above, it's actually important to start sail trimming from the most forward sail and work aft just as the air also flows aft.  Otherwise you would be in another never ending circle.  So first, start with your jib.    (write me if you are not sure how to set up the jib)

Mike 2024

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Copyright mjw - 2024


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