My 2002 Jeanneau Sun Odyssey 32 was quite a simply-rigged boat when new: to keep the price reasonable, the builders had hardly pushed the boat out when it came to deck gear, writes Bob Goode.

The downside to this was that she could be a bit of a handful in winds above 20 knots, particularly if conditions were gusty. The solution was simple: improve the sail handling controls and fit better sails.

The original ‘Technique Voile’ sails were adequate but lacked the material quality to last long and quickly lost their shape.

One item that needed attending to immediately was the backstay.

The original, a 4mm fixed wire split backstay, did not allow adjustment to flatten the main and tighten the forestay in stronger winds.

I started by fitting a simple strop between the split stays: this allowed me to apply some tension, albeit not easily, to see if the results would be worth the expense and effort.

Bob checked the rig tensions with a good-quality tension gauge before starting work on fitting the adjustable backstay. Credit: Bob Goode

A positive outcome saw me dashing off to buy a good rig tension gauge and setting about recording the tensions in the rig.

Some research on breaking strains and comparison with the recorded tensions allowed me to design a simple cascade that would replace the existing split wires.

I used the strength of the existing wire backstay as a guide to the required strength in the replacement components to avoid introducing any weakness in the rig.

I would keep the same main section of backstay from the masthead but replace the 4mm 1×19 split wires with a single, 5mm 7×19 wire, passing it over a wire block fitted to the main part of the retained backstay.

The ladder was secured on a very calm day in a marina at low water – so no wash from passers-by to allow for fixing the check-line on the backstay. Credit: Bob Goode

The single wire would be shorter to allow for the adjusting pulley system.

Fitting would pose a problem as the mast would have to remain in place while the work was carried out.

Fortunately, the Sun Odyssey 32 has sharply swept back spreaders, so even with the backstay released, the mast should remain fairly secure.

I fitted a stepladder across the cockpit and roped it tightly in place.

Luckily, my berth at Chichester Marina is very calm, and at low water springs, the access channel is so shallow that there are virtually no moving vessels to create an unsettling wash.

Backstay secured and the Barton wire block in place with 7×19 wire threaded. The green line is a temporary check line to hold the backstay in place. Credit: Bob Goode

The stepladder allowed me to reach the connection where the original split wire was fixed to the single backstay running up to the
masthead.

To be on the safe side, I attached a temporary securing line and tensioned it to ensure the fitting at the masthead stayed in place.

With the new flexible wire already threaded through the wire block, I secured the new block to the existing backstay fitting and then connected the fittings back at deck level before threading the Dyneema rope.

Stopper knot and bobble which prevents the tension from being inadvertently released from the adjustable backstay. Credit: Bob Goode

I then used the original rig tension measurements to adjust the new backstay so that the rig was correctly tensioned again.

Next, I checked that the tension in the cap shrouds did not drop too far when tension was hauled on the backstay: this is important as the cap shrouds act partly as backstays and partly to keep the mast from inverting.

All that remained was to whip the knots in place and add a stopper to the adjustment line so that the backstay could not be inadvertently completely released.

Improved performance during the first sail in a fresh breeze quickly convinced me my work to fit an adjustable backstay was worth the effort.

And on top of that, I now have an extra line to play with on longer sails!

Swapping to an adjustable backstay: How the cascade system works

At each stage of the cascade, the safe working load (SWL) can reduce as the total load is shared between the parts of the subsequent cascade.

One end of the flexible 7×19 wire split backstay is secured to the existing deck fitting on the starboard side of the yacht.

From there it goes over a Barton wire block on the end of the existing backstay. The port side end of the 7×19 wire is fitted with a single 60mm block.

An 8mm Dyneema line leads from the port deck fitting over this block to a 50mm triple block.

With another triple block and jammer secured to the deck fitting, a 6mm Dyneema line completes the cascade.

Stainless steel wire

Assuming you don’t have exotic rigging, your mast is probably held up with 1×19 stainless steel wire – ie the wire consists of 19 single strands.

This construction is strong, with little stretch; however, it is also inflexible. If the wire is to go around a pulley, then the wire of choice is 7×19, meaning the wire is made up of seven strands, each consisting of 19 smaller strands.

This is not quite as strong as 1×19, but it is very flexible.

Typically, the breaking strain of 4mm 1×19 stainless steel is around 1,400kg, which is about that of 5mm 7×19 stainless steel.

A safe working load would be no more than half this figure.

Dyneema rope

Dyneema was chosen for its great strength, low stretch and minimal creep under load.

A typical 8mm line has a breaking strain of around 3,000kg, so it is over strength for this application.

The 6mm Dyneema has a breaking strain of around 1,600kg so is also over strength, but is much nicer to handle than a thinner
line would be.

Wire blocks

The breaking load of the Barton wire block is 1,300kg: 60mm Lewmar Synchro blocks are specified to have a safe working load of 800kg, and the 50mm ones around 450kg.

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