Easy ways to power up your mainsheet

New production yachts often come with systems that have been designed more for convenience while moored than with a sensible engineering solution in mind, resulting in significant loads placed on the boom, kicker, boom-end fittings, mainsheet tackle and crew.

Duncan Kent is a technical writer for marine publications and websites

Making a few tweaks to how your mainsheet system is set up makes handling easier for you and prevents breakages and wear to your fittings.

Keeping complex sail control mechanisms away from vulnerable areas of the boat is paramount, which is why cruising boatbuilders often position the mainsheet up on the coachroof ahead of the main hatch garage.

Though this effectively keeps it ‘out of the way’, it’s often not ideal from an engineering point of view in that it invariably means the mainsheet is attached halfway along the boom, when best mechanical advantage is offered at the aft end.

When connected further forward on the boom, the load on the mainsheet is greatly increased, so too the amount of human effort required to operate it.

If it really must be on the coachroof, then it should be mounted directly under the first leech reefing point, giving you the same mechanical advantage when the wind is up and you’re reefed.

Mainsheet blocks

The key to any sail control system is to keep friction to a minimum, which means the dimensions of the blocks, sheaves and lines are all important, as well as the type of bearings they have.

In principle, you should choose a sheave diameter of at least six times the diameter of the sheet, within the safe working load of the system.

Upgrading the line to one with superior strength, such as Dyneema, and lower stretch can result in you being able to drop a couple of sizes in line diameter, reducing costs, effort and wear.

The type of bearing a block has makes an enormous difference to the friction in any high-load tackle.

Standard plain bearing models are strong, but hard to turn, whereas ball-race and roller types require far less effort.

However, though ball-race bearings reduce friction, they also reduce the working load capacity as Delrin balls (most common) can distort under load long before a plain metal bearing would.

For this reason, the more popular choice for larger yachts are blocks with roller bearings, that have the low-friction of the balls, but the load capacity of plain bearings.

Specialist Rutgerson supplies a range that’s even maintenance-free, thanks to clever ‘roll- links’ between the rollers that keep out dirt and salt.

Mechanical advantage

A 6:1 tackle theoretically reduces sheet loads to 1/6th, but in real terms it’s closer to a quarter due to the friction in the block bearings.

Upwind the average load on the mainsheet for a 35ft cruising yacht with the mainsheet attached at the boom end is said to be around 150kg in 16 knots of apparent wind.

This would result in an actual hand load of roughly 37kg (including friction) if you were to sheet her hard in at this point with a 6:1 tackle, dropping to a more manageable 15-20kg in 12 knots apparent wind.

Whilst it’s useful to have an idea of how these items are rated, most manufacturers will recommend which size line and block you should use for your set-up.

Overhead mainsheet tracks retain the mainsheet’s mechanical advantage while keeping the track out of the cockpit. Credit: Graham Snook/Yachting Monthly

You can make the main easier to sheet in by increasing the mechanical advantage via an additional purchase (more turning blocks) or, if possible, moving the attachment point further towards the end of the boom.

Remember, though, that the more parts a tackle has, the more line is required, which, when close-hauled, has to go somewhere in the cockpit!

Alternatively, you could use a two-speed, double-ended tackle such as Harken’s self-contained system.

Pulling on both lines sheets it in quickly but requires more effort, whereas pulling just on one line doubles the mechanical advantage, halving the effort needed.

This method uses far less line than a traditional multi- way block arrangement and doesn’t introduce dangerous ‘flying’ blocks where a ‘fine trim’ block is positioned halfway up the mainsheet – just about at head level when tacking.

A widespread problem with any mainsheet system that incorporates a cam cleat can be difficulty with releasing the sheet under load.

Many folk don’t realise that on almost all blocks with a cam cleat attached the lead angle can be adjusted to suit the set-up, which can make life a whole lot easier and avoid you having to use your foot on the sheet to release it.

Sit in the cockpit where you normally would when sailing upwind and check that the cam cleat is in line with or just above where your hands are.

Twist can also be a problem on multi-part mainsheets due to the natural twist in the line, often exacerbated by having two swivels or the line being incorrectly reeved.

The former is simply cured by ensuring there is only one swivel, which is attached to the traveller end so that the lead angle can be changed easily when changing tack.

Some blocks, such as those from Selden, have lockable swivels.

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Reeving is an art form in itself and is by no means obvious.

Very often a multi-part tackle is mis- reeved causing two parts of the sheet to chafe against each other creating friction and the whole set-up to end up twisted.

Correct reeving (if in doubt ask the supplier) eliminates crossed lines and ensures load is balanced evenly across all of the sheaves.

Finally, some mainsheet tackles have a ratchet sheave, although they don’t really help much on a cruising yacht.

They do relieve some sheet load, but a larger mainsheet tackle needs a quick- release jammer to be safe and the faceted V-grooved rope channel simply puts extra wear on the sheet.

Sail control: Getting the most from your mainsail

The Traveller

• The traveller is one of the most important aspects of mainsail trim, yet I have been on numerous yachts where the traveller has been ignored all its life. Not knowing its purpose, many owners leave it fixed permanently in the centre. On one boat I sailed it was even screwed down!
• The reason for having the mainsheet attached to a traveller on a track is to enable it to be used to control the position of the boom under sail. Letting the traveller run down the track ‘spills’ the wind in the mainsail and reduces heeling momentum instantly, without affecting the shape or trim of the mainsail itself. When the gust has gone through all you need do is haul it back up the track to put the power back on, knowing the sail will be set as before.
• If you have an old boat with spring- release locking pins on the traveller, I would advise you modify it or replace it with a purpose-made system. If this isn’t possible, then you’ll need to rely much more on the kicker (see above) for controlling the sail shape when sheeting in and out.

The mainsheet track

• The position of the track is also important. The closer to the mast the mainsheet is attached to the boom, the shorter the track needs to be (as the outboard end of the boom moves in a much wider arc than the inboard end). However, mounting it ahead of a spray hood makes it extremely difficult to adjust the position of the traveller in a hurry.
• Tracks that are mounted overhead on a gantry, like those on the Hunter Legend range of yachts offer something of a compromise. To my mind their good points – long track right across the boat, mainsheet attached at the end of the boom, tackle kept well clear of the cockpit – are somewhat negated by the need for another turning block in the traveller adjusters, increasing friction and making them harder to adjust quickly.
• It makes sense to have the mainsheet track within reach of the helmsman with the mainsheet tackle as close to vertical below the boom end as possible. In some cases, especially on smaller boats, this will mean the mainsheet track is in the cockpit and can restrict access when not sailing. It is possible to install a removable track mounted across the centre of the cockpit well, for example, but quickly detached in port or at anchor to free up the space for relaxing. UK deck gear specialist, Barton produces a range of these for yachts right up to 36ft LOA, complete with traveller adjustment blocks mounted on the end-stops.
• Sometimes (particularly on coachroof- mounted tracks) the track has been ‘contoured’ to suit the curved cabin top. I’d strongly recommend replacing it with a straight, flat piece of track. A curved track encourages the traveller to remain in the centre. If you force it to the end using a powerful adjuster tackle it will simply pull the boom down.

The kicker

The kicker is almost as important as the sheet for controlling the mainsail. Credit: Graham Snook

• The kicker (aka vang) is almost as important as the sheet for controlling the mainsail but is often ignored. The kicker’s primary purpose is to keep the boom from rising up when the mainsheet is eased. It is especially vital if you have a single-point mainsheet fixing or a bridle, rather than a track and traveller, as the former allow the boom to lift as soon as the
• mainsheet is freed.
• Because of the extreme loads it has to undergo, the non-boom end of the kicker should ideally be attached to a reinforced pad eye on the deck or to a stout collar around the mast, rather than a simple, riveted mast fitting.
• A gas-sprung or hydraulic kicker enables you to do away with the topping lift as, when the kicker is released, the spring-loaded vang pushes the boom upwards. It’s sensible to put the main halyard on the boom end to act as a topping lift when leaving the boat to take the permanent load off the spring.

Safety first

• Mainsheet tackles, tracks and travellers, kickers and boom fittings are all subjected to massive loads in heavy conditions, but should the yacht undergo an accidental gybe these loads can increase tenfold. For this reason, it can pay dividends to fit a boom brake of sorts. These ‘adjustable preventers’ not only allow for more control during an intentional gybe, but also stop the boom crashing over and possibly taking the rig down in the event of an accidental gybe. There are several on the market, including the Scott Boomlock, Wichard’s Gyb’Easy, Walder Boombrake, which can really offer peace of mind, particularly when sailing dead downwind.

Leech control

Leach control is important for gust response, adapting to conditions and preventing excessive heel. Credit: Graham Snook

Jeremy White of Elvstrom Sails shares his tips

• Traditionally you’re taught to pull in the mainsheet until you get the desired amount of twist (and so power in the sail), then take the slack out of the kicker, which will lock in that twist setting.
• The problem with mainsheet systems located forward on the boom, is you can’t get the leech tension you need. In this situation you’re forced to use the kicker alone to shape the leech. It is rare you are able to get as much tension via the kicker as you are via the mainsheet without using a winch and when cruising few of us are likely to do this.
• That is not to say it is always a negative outcome. The bonus to plenty of mechanical advantage is that when you ease the main, the leech remains tight which, in turn, gives more finite control. However, I often think the twist that develops in a mainsail when easing a mainsheet with less load in the kicker functions as a very effective safety valve. Racing sailors might want to have very specific control if someone is constantly trimming, but being able to lose a lot of power quickly by easing a small amount of sheet does have its appeal.
• If you are using your traveller then your leech will keep the same shape as you let the traveller down to depower in a gust anyway, so using this most of the time, there is no harm in being set up with less kicker than desirable as this will act as a macro adjustment in a really big gust.

Power up your purchase

• Consider an upgrade. Make sure your traveller is able to move easily while under load, and if possible can be adjusted from the helm. Consider upgrading your mainsheet track. Moving this to the cockpit will increase sail control and you can fit a removable track. At the same time, adding a purchase to adjust the traveller under load will also make sail adjustment much easier.
• Keep a clean sheet. Ensure your mainsheet system is free of twists, is correctly reeved and has the right rope and sheave sizes. Any unwanted friction in the system results in more effort for the crew, so make sure your mainsheet is reeved through the blocks correctly. You can also lock the top set of blocks so they can’t swivel, which will help keep the twists out.
• Here’s the kicker. Use your kicker. This is increasingly vital on those boats without a traveller or on those boats with a mainsheet system located mid-way down the boom. The kicker controls leech twist and gives you better control of power in gusty conditions and downwind.
• Increase the power. Move the adjustment point of the mainsheet further aft along the boom if possible, or add more purchase to your mainsheet system, or opt for a speed-sheet system to reduce sheeting loads. Consider adding more purchase to your kicker system too, to give you more control over the leech shape, though you may need to reinforce or change its mast attachment point. Adjust the angle of your cam cleat to make cleating and uncleating easier.
• Block busters. Get the blocks and cleats set up correctly to reduce friction and make it easier to use. Ratchet blocks are generally unnecessary on cruising boats and add friction, so get rid of these if you have them. Check the bearings of the blocks run freely under load – they may need replacing. Just washing the blocks out with fresh water and spraying with dry lubricant can work wonders with friction.

German mainsheets

German mainsheets that run to the end of the boom offer good control and minimise rope in the cockpit, but the sheet needs working. Credit: Graham Snook

The double-ended, or single-piece mainsheet has become known colloquially as the ‘German’ mainsheet.

Often the sheet will come back to a pair of primary winches, one either side of the cockpit.

With this system a crewmember can sit on the windward side with full access to the traveller and mainsheet winch.

It is a workable solution too for shorthanded sailing on dual-helm yachts, in that the helmsman can control the mainsheet from either helm.

A key disadvantage is that often you end up with all the sheet on one side, unless you constantly even out their use as you go.

To counter this, splicing the ends together makes a continuous loop, but this does make it harder to neatly coil and tidy away.

Increasingly these systems return to a cabin-top winch.

Though this does free up cockpit space, and means there is no mainsheet to catch an unwary crewmember in a gybe, it significantly reduces ease of use and accessibility significantly.

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