Tips to avoid frigging around with your rigging

by Yachtpro on 14 Sep 2003 Rig-tuning is an inexact science in many situations, so if you are not confident, hire a rigger or a professional who can tune the rig correctly. It will be money well spent. However, here are some good tips on adjusting your rig.

Before trimming your sails correctly, you must ensure that your rigging is tuned in sympathy with the sails you will use and their intended purpose.

Tuning the mast controls its performance in two planes: lateral and fore/aft.

The configuration of your rigging will dictate your goals and the tools you have available to achieve the desired result.

The result we want and how to get it:

Ensure the mast is upright. Check the mast is straight and vertical. Tension the shrouds, being careful not to distort the mast column. When under sail, sideways bend should also be checked.

Set the fore/aft rake for a balanced helm. Adjust the rake by adjusting the forestay to ensure the center of effort (CE) of the rig is over the center of lateral resistance (CLR) of the hull.

This will ensure excessive helm is not required to steer the yacht.

Mast-bend should suit the mainsail shape. Use the backstay and/or runners, in concert with the inner forestay and checkstays, to ensure mast-bend promotes the desired mainsail shape.

Forestay tension to keep headsail luff tight. On masthead rigs use the backstay and on fractional rigs use the runners, where fitted, or shroud tension.

Things you should watch for and eliminate or limit in lateral and fore/aft mast tuning:

Sideways canting: if the mast is leaning over from vertical, you probably have insufficient tension in the shrouds.

Sideways bend: the characteristics of sideways bend depend on the spar and rig configuration.

On fractional rigs it is almost impossible to eliminate sideways bend, due to the unsupported section of mast beyond the hounds, but this bend should be controlled.

The masthead falling off to leeward in fresher breezes has the effect of easing the leach at the head of the main while the lower sections, bending to weather, flatten the main and open the slot. This is often fast but it must be controlled.

On masthead rigs, sideways bend is usually due to slack shrouds and is inadvisable. This usually results in the head of the mast falling off to leeward and can lead to headstay sag and structural failure.

Pre-bend is the amount of fore/aft bend permanently induced into the mast by the combination of mast-step, mast-deck chock and shroud tension.

It is very important because it will enable the section to resist inversion, to set the main correctly and, on fractional rigs without runners, maintain forestay tension.

(Inversion is where sections of the mast bend uncontrollably forward when they are not intended to. Avoid this.)

Once your mast is set in column, most of the sailing controls decide the fore/aft characteristics of the rig.

The controls available and their effects depend on the rig. On masthead rigs, the combination of backstay and inner forestay controls are used.

The backstay sets up mast-bend and controls the tension of the forestay while the inner can induce more bend by pulling the mast forward or be tensioned to stop pumping – the fore/aft movement of the mast caused by the boat hitting waves, etc.

If fitted with swept-back spreaders, the horizontal shrouds will induce pre-bend while the verticals will limit it.

On fractional rigs with in-line spreaders, your base controls are the running backstays and backstay. The running backstays control headstay tension and mast-bend with tension. The backstay controls tip-bend and can free the mainsails upper leach.

On fractional rigs with swept-back spreaders, the backstay controls tip-bend and, to a lesser degree, forestay sag.

Checkstays perform the same function for all rigs. They control the bend characteristics of the mast. Pulling them on straightens the section while freeing them allows the section to bend.

This directly affects the setting of the mainsail luff and may be in slight opposition to the bend characteristic induced by other controls, so it must be used carefully.

Checkstays are also used to reduce or stop mast pump.