How a thorough rig inspection saved my mast and our Atlantic crossing

Dave Carey on performing a rig inspection, measuring up and ordering new fittings and re-rigging and retuning the mast on a 47ft cruising yacht... all while living aboard

rig inspection

As a former RAAF (Royal Australian Air Force) aircraft technician, I was always going to perform a thorough rig check before attempting my first ocean crossing.

Our 1984 Moody 47 Roam is a solid blue water performer, but as I am quickly learning, boats are only as reliable as the owners who maintain them.

Having never attempted an ocean crossing, I erred on the side of caution in the way I prepared for our west to east passage across the Atlantic.

Our vessel, although stoutly built, was made in the 1980s and has many of the original fittings.

One of the main issues I was concerned about was the rigging and in particular, the chainplates.

The rig had been replaced seven years ago – not an overly long time as far as standing rigging is concerned – but what did set off alarm bells was that the chainplates, and their mounting hardware, had never been replaced.

After tracking down the original owners of the boat, I found she had completed seven Atlantic crossings, enduring over 30 years of cyclical loading. A little investigation showed that the deck plates had never completely sealed out the water from penetrating the deck. This combined knowledge planted a seed of doubt in my mind.

Thankfully I have never had an issue with heights. After preparing my bosun's chair and emergency lines, and with my wife, Erin, at deck level on the winch, I clambered up the mast with my magnifying glass, a rag and my iPhone for taking pictures.

Forget the view of the bright blue sea and focus in hard on your stainless rigging (click image to enlarge): (Left) Hairline crack – only visible in the right light; (middle) crack circled in chainplate; (right) Crevice corrosion in chainplates where stainless meets the deck (only revealed by pulling the chainplate)

With a spectacular view of the turquoise Caribbean waters of Marigot Bay, St Martin, I set to work. It took me the better part of the afternoon to properly clean and inspect the rigging and I was not overly happy with what I found. Although difficult to see, hairline vertical cracks had appeared in the swages, and there was also some pitting – not discoveries that filled me with confidence prior to tackling the open ocean.

Corrosion is an insidious thing; from the outside everything can look fine, giving the unsuspecting sailor the impression that their gear is in good condition. When I pulled bolts from my chainplates I found that in some cases, corrosion had rendered them completely useless. Corroded threads, pitting and missing steel were all present.

Why I replaced all 36 of my boats 5/8in diameter chainplate bolts.

Perhaps the scariest find was the stem fitting bolts. With only a ratchet in hand, I put some pressure on the nut of the bolt to undo it, the bolt snapped clean off. To my surprise and horror, as I performed the same manoeuvre on the second stem fitting bolt, the same thing happened.I wasn't too happy about how this was unfolding, and as I quickly secured spare halyards to the windlass horn and forward cleats to support the rig, I had visions of my forestay parting at the bow, and my mast crashing down in a tremendously dangerous fashion.

With halyards in place, I was able to breathe a little easier and take stock of the situation.

It was clear that I’d have to replace all 36 of the 5⁄8in diameter chainplate bolts in the boat.

The next day I visited three chandleries, two rigging shops, and a local commercial fastener store before I managed to obtain the correct bolts, nuts, and washers for the job.

Having lost faith in my boat's mounting hardware, inspecting the chainplates themselves was the next item on the agenda. There isn't much to be gained without pulling them to see how the steel looks as it passes through the deck. This is the area where crevice corrosion usually forms.

By using halyards to support the mast I was able to remove the forward and aft lowers, and could then pull the corresponding chainplates. Rust staining on them was obvious, but inspection with a magnifying glass would be required to get an accurate picture of the damage.

Pitting is another cause for concern. As I cleaned and inspected them, the small brown holes in the steel staring back at me helped confirm the decision to replace rather than reinstall them to keep my boat seaworthy.

On many cruising yachts, the bow roller is integral with the stem fitting. These beautifully crafted, seamlessly welded items, when observed closely, are amazing things. Often, the manufacturer will weld circular stainless steel plates onto the main body of the chainplate where the clevis pin is installed, to counter the point loading experienced in that area.

Again I was surprised to see that my stem fitting had a crack in it; the welded circular plate had separated after years of fatigue and exposure to the elements. At this point, it was time to speak to a professional fabricator.

In the Caribbean islands, there are many marine chandleries and fabricators to be found. It is pretty much a case of speaking to the local yachties, or putting out a call on the VHF radio net to find a reputable company. With the knowledge of which company to use, I made contact and discussed the job with them. The plan was to have them cut the stem fitting from the bow roller, manufacture a new one and weld it back in exactly the same orientation. I was assured that a jig would be made to match the angle of the old bow roller/stem fitting, as the angle had to be correct due to the rake of the bow.

Naively believing this would be done, I didn't measure the angle of the stem fitting myself, something that would have saved me heartache in the future. The new stem fitting was fabricated, polished and welded to the bow roller arrangement, looking good as new.

On returning to the boat, I gathered all the necessary tools to reinstall the newly fabricated and highly polished bow roller/stem fitting. In the excitement of collecting the unit, and admiring the polished finish and craftsmanship, I hadn't noticed the glaringly obvious mistake the shop had made, the angle of the stem fitting was too small, there was no way this item was going to bolt in.

After returning to the fabricators, and following a few heated words, workers were organized to come to my boat at anchor, measure the correct angle and adjust the incorrectly made item.

Luckily, on the second attempt, I was able to massage the item into place and bolt the forestay back on.

There was no denying I had a sour taste in my mouth, and I wasn't very keen to give more business to this rigging company. It was time to source a new fabricator. I managed to track down a man who worked out of shipping containers in the industrial side of town. I was assured by a local who runs the radio net in St Martin (thanks Shrimpy's Laundry!) that his work was top-notch.

It soon became apparent that this one-man shop had all the machinery and expertise to complete the task of fabricating the remaining eight chainplates. After meeting the South African gentleman who runs the shop, the job was discussed and a price agreed on.

From here I went through the process of supporting the mast with halyards, removing one chainplate at a time, having it made and polished, then installing it with new bolts.

Another issue to look out for with boats that have protrusions through the deck is leaking deck plates. When water gets into this area, it will cause crevice corrosion, and rot cored decks.

Having felt the wet, rotten plywood in these areas, I knew a repair would need to be carried out using West System epoxy.

I really love this product; it's easy to use, makes strong permanent repairs and can be used on a variety of jobs from structural gluing and fairing, to osmosis repair.

Using a cordless drill with an Allen key in, you can machine-out the rotten ply. Allow some time for the area to dry before mixing the thickened epoxy then form it into the repair area. Carrying out this task will help when resealing the chainplates, and will ensure your deck is properly supported.

Regardless of how good your hardware and chainplates are, if the knees that are fibreglassed into the boat are rotten, the mast is at risk.

When inspecting the knees, pull bolts and use a scriber to determine if the timber is rotten. Push the scriber into the timber of the bolt hole, a little wetness is no cause for concern as the area can be scraped out and some thickened epoxy used to remake the hole where the bolt goes through.If there is significant moisture and rotten timber, the knee may need to be replaced.

If you have come this far in your quest for seaworthiness, don't stop now, do the job right. Fortunately, mine were solid.

My next task was to measure up the old rigging before ordering replacements. I chose a calm day and had my wife hold the tape at deck level while I took the measurements according to the rigging manufacturer's guidelines.

Remember that some measuring tapes stretch, so be sure you only put enough pressure on the tape to get an accurate reading, and that the tape is following the contour of the wire as it passes through the spreaders.

When measuring up, pay attention to the number of threads showing inside the turnbuckle at deck level, try not to be on the upper or lower limit when it comes to turnbuckle adjustment. I checked the measurements of our rig three times to be sure.

When the new rigging arrived in St Martin from Florida, it was like Christmas had come early. I could feel the Atlantic crossing was in our grasp; the reality was setting in and we might actually have to leave the Caribbean!

I found the best way to replace an upper shroud was to go aloft in the bosun's chair with the required tools and a long length of 8mm rope. I have a large permanent snatch block for a spare halyard near the uppermost sheave, and this was an adequate purchase point.

I attached the rope to the installed rigging wire while Erin took the tension off the shroud by loosening the turn barrel at deck level. I knocked the clevis pin out and then – while holding the rope passed through the snatch strap – slowly lowered the wire rope to the deck.

At this stage you will have the entire weight of the shroud attached to the 8mm rope in your hands, so you’ll have to physically brace yourself as you sit in the bosun's chair; a falling swage fitting from this height could go through the deck, or hit someone.

With the shroud lowered, Erin undid the rope and tied off the new shroud in the same manner.

At first it was easy to use the rope to pull the new wire rope up the mast. However, it became much harder as I hauled the entire weight of the wire rope.

Once the new shroud was hoisted up, I popped the clevis pin through the swage fitting and the tang, and installed the split pin. From here I fed the shroud through the recess in the spreaders.

Once routed correctly, Erin tightened the turn barrel at deck level by hand.

It's very important to ensure that the spreaders bisect the angle of the cap shroud. According to Sail & Rig Tuning by Ivar Dedekam, this is very often neglected and has been the cause of a number of mast failures

Mast tuning is not overly complicated when approached in a systematic way. A correctly tuned rig will ensure a faster boat, with less heel and will allow you to point higher, something every sailor seems to need sailing between the Caribbean islands!

Begin the rig tune by initially straightening the mast, which is carried out by adjusting the forestay, backstay, and upper shrouds.

To check the mast is centred, swing the main halyard to the port cap rail, then to the starboard cap rail, it should be equidistant, If not, adjust the upper shrouds accordingly and hand tighten the corresponding turn barrels, making sure to stop the wire rope from turning as you tighten the turn barrel. There are usually two flats machined onto the lower swage to accommodate a spanner.

Allow the boom to rest on the deck, or prop it up with a piece of timber, so the topping lift can be released. The lower shrouds should be loose at this stage.

Masts are usually set with a slight (1°-3°) aft rake, which improves upwind sailing ability. This can be eyed off or specifically set using a plumb bob mounted to the top of the mast.

The forestay length is predominantly used to set the mast rake, with the backstay being used to determine the forestay sag.

Don't induce too much aft rake as this will lead to increased weather helm.

Maximum backstay tension is generally agreed to be 30% to 40% of the stay's breaking load.

With the mast rake set, hand-tighten the backstay turn barrel, and with the mast in its desired position, you are now ready to put some tension into the rig.

To check the mast is centred, swing the main halyard to the port cap rail then to the starboard cap rail. It should be equidistant.

A simple but effective method of determining the tension in the wire rigging is to measure the stretch of the installed wire from a set point as the rig is tensioned.

With an accurate tape measure, place a mark on the upper shrouds, 2m above the top of the lower swage fitting.

As the turn barrels are slowly and equally tightened, measure the amount of stretch in the wire, by comparing the mark on the rig with the tape measure 2m mark. As the tension comes up, this measurement will increase. Every millimetre of stretch is the equivalent of inducing 5% of the breaking load of the wire, over the 2m sample distance.

It is generally accepted that a figure of 15% of the breaking load of the wire is how tight the shrouds should be. This equates to 3mm of stretch.

Set the mast pre-bend by adjusting the forward lower shrouds. This is done to flatten the upper half of the mainsail.

With the rig tensioned, use the main halyard to recheck the mast has remained centred. Also, look up the mainsail track; it should be straight.

The backstay can also now be tensioned to approximately 30% to 40% of the stay's breaking load. However, do check this figure with the boat manufacturer, remembering that over the 2m sample we’ve marked out, 1mm of stretch equates to 5% induced breaking load, so 30% on the backstay would be 6mm of stretch measured over 2m.

All in all our chainplate and rigging replacement was completed for a fraction of the cost of hiring a project manager or a rigger. The job was reasonably difficult. You need to feel comfortable working at height, and have a good working knowledge of what safety precautions you will implement. Some things to consider are:

■ How competent are you working aloft with hand tools?

■ Do you have the strength to be repeatedly climbing your mast?

■ What processes do you have in place to deal with an emergency while you are aloft?

■ Can you handle the responsibility of knowing you replaced your rigging?

■ Do you have an assistant who you trust with your life to hoist you up the mast, and perform deck level duties?

■ Are you meticulous with measuring and recording numbers?

■ Do you have the required tools and hand skills to perform the task?

This article was published in PBO September 2020 with the following expert opinion from Mike Coates, who has since passed away.

This is a very well carried out inspection. Dave's training has held him in good stead and he has possibly gone a lot further than most riggers would. He is obviously well versed regarding crevice corrosion, which quite often goes unseen until disaster manifests itself.

Cracking of swaged terminals is not an uncommon cause of failure and can often be attributed to over swaging by the rigger attempting to get the swage down to the correct size, straightening of a bannered or similar swaging defect.

Often this is a result on older swaging machines where the bearings have worn, giving play in them, allowing the gap in the swage blocks to open sufficiently to prevent the machine producing a swage down to size in a single pass. To counter these defects the swage is often passed through the machine numerous times resulting in work hardening of the material and subsequent cracking which can go undetected for some time. Very rarely – and this is from my own from experience – the swage has been produced by incorrectly specified material, that is, it was made from a material which was not malleable resulting in cracking.

On the subject of crevice corrosion, boats moored in the tropics suffer more readily from crevice corrosion owning to the raised temperature and higher humidity. We were often requested to fill swages with a silicon sealant prior to swaging to help prevent any possibility of water ingress and subsequent hidden corrosion within the terminal.

I was a little sceptical at doing this at first, fearing it may compromise the grip of the wire in the terminal, but pull tests revealed little if any difference.

Annual rig checks are essential. These should include looking for broken strands of wire where they exit the swage terminal.

If you suspect you have a cracked terminal this can be checked using an NDT (non-destructive) spray, which usually consists of three spray cans, a cleaner, a dye and a developer. After cleaning, the dye is applied and left a few minutes and then cleaned off with the developer. Any cracks will have residual dye left in them making them much easier to see.

NDT kit

All standing rigging should be replaced preferably by the eighth year and by the tenth at the latest. This is because the rig is subjected to cyclic loading which causes unseen work-hardening of the material, which in the long term can result in failure. A good example of cyclic loading is to straighten a wire coat hanger then repeatedly bend it back and forth – eventually the wire will fail.

If in doubt about any part of your rig consult an experienced rigger for advice.