Chainplates

Westerly Chainplates – Sealord/Oceanlord

Camomile is a 1985 Westerly Sealord and, in common with most Westerly boats, is “as tough as old boots” however in common with just about every other design of boat she has her Achilles heel(s).  Chain plates are one of the foundations of a sailing rig and both before we set sail for the other side of the world and during our adventure they have given us a few “moments” (see https://yachtcamomile.wordpress.com/2010/03/05/on-to-galapagos/ ) and also needed some care and attention which I describe below along with a few recommendations for those who may own a similar arrangement.

 Forestay – Bow roller chainplate

Bow roller chain plate

Bow roller chain plate

As with many largerWesterlyboats, the Sealord has a double bow roller with the forestay toggle attached to the centre of three vertical webs which is thickened in the area of the clevis pin hole. The weakness with this arrangement on Camomile was between the front horizontal part of the chainplate and the front edge of the centre web where a crack appeared in the weld.

I had heard of this problem on other Westerlys but am not aware of it having caused a rig failure however felt that the problem should be addressed before the crack propagated.

Roller plate removed

This involved stripping the chainplate and the adjacent stainless strake then, as there were no other signs of stress or fatigue adding a lateral reinforcement. The strip down and reassembly operations of the through bolts were by far the most difficult part of this job as the access below decks is restricted to a small chain locker hatch just large enough to squeeze a torso through with arms raised and thus not something for anyone with claustrophobic tendencies to attempt. In addition to thisWesterlypractice is to lay fibreglass over the nuts which prevents leakage but, as they can spin, also prevents their removal from outside. The solution for this was to remove the drill from a hole saw and allow the saw to centre itself over the bulge of the glassed nut. This removes a small disc of fibreglass which allows a socket onto the nut to remove it.Instructing the fabricator how I wanted to add the lateral web and its drainage holes was achieved by cutting pieces of card and taping them to the roller chainplate as a mock-up of the addition. The fabricator used this card as a template and made a good job of the modification.

Added reinforcement plate

On reassembly I attempted to lay fibreglass over the nuts and washers inside the hull as this is the typical treatment throughout the boat but success was limited to the vertical surfaces as I found that making fibreglass stick, laying upside down under the deck with such limited access, was impossible. I had in any case ensured that the modified roller chainplate was bedded down on the deck with PU mastic and figured that any small leakage which might occur is in a well drained area anyway.

My recommendation to Sealord or other double bow rollerWesterly owners would be to inspect the suspect area and, if no cracks are seen, to keep a reasonably frequent watch on it if you are clocking up sea miles. If you see a crack then obviously fix it as loosing a forestay under sail is a good way to break your mast which can spoil your whole day.

 Babystay

When Camomile was surveyed, both before we bought her and then before setting off about 10 years later, the two surveyors both zeroed in on the babystay.

12mm gap under heads bulkhead

They thought that they spotted some distortion of the deck in the vicinity of the chainplate and both insisted on removal of the headlinings below to inspect the condition of the coach roof and bulkheads. They saw the small brass backing plate with no evidence of movement in the laminate so therefore concluded that, as was common with Westerly practice, the rig had been tensioned up a bit early during construction and had “pulled” the laminate a little.

Many thousands of sea miles and a few gales later this turned out to be wrong. The deck was in fact being pulled upwards but was taking the bulkheads below with it leaving no sign behind the headlinings that movement was taking place. The clue to what was going on came from the floorboards which became more and more curiously misaligned to the point where a joint under the heads bulkhead, which would have been closed when the boat was made, had eventually opened up to show a 12mm gap. I had monitored this gap after our Atlantic crossing, after the Pacific crossing and following our return trip fromNew ZealandtoFiji. It had steadily grown from 6mm to 12 at which point I resolved to address the problem.

The cause was that the heads bulkhead which bore most of the load from the stay was only partially bonded to the hull and, after a few oceans worth of abuse, had started to open. This did not look as if it had the potential for a sudden catastrophic failure but was worrying nonetheless.

Fortunately there was a hull reinforcement just below the heads which, when stripped of it’s protective flocoat back to key able fibreglass layup and reinforced with a wide multi-axial tabbing tape laid in with epoxy resin, could serve as an excellent anchor zone.

Longitudinal member exposed for rework

Access was extremely difficult but by cutting an access hole in the heads shower tray floor and enlarging access under the forepeak sole it was perfectly achievable.

Cutting laminating access in heads shower tray

Epoxy multiaxis tabbing to reinforce member

I toyed with the idea of leaving the movement that had already occurred and just re-bonding what I had, but realised that it would be better to attempt to rectify the movement to ensure that the stresses were distributed more evenly. The problem then became how to pull back that 12mm gap to zero so I developed a small stainless jacking arrangement and bonded this into the hull reinforcement profile. I then added a link to the heads/forepeak bulkhead.

Cross section of jacking arrangement

Getting this whole mechanism in place was a little like performing keyhole surgery but once it was in place I then waited for 3 weeks to ensure that when I returned to tension it the epoxy layup had cured to near its maximum strength.

I slacked off the babystay and tightened the tensioning bolts a turn at a time. Millimetre by millimetre the 12mm gap obediently closed up to zero and to my surprise the whole operation took place with no nasty creaking or groaning taking place which I partly attribute to doing the job in Fiji where the temperature in the shade was in the mid thirties.

Finally I gingerly re tensioned the baby stay and was rewarded by everything performing as expected.

Bolted, plated and re-tensioned

I was satisfied now with the integrity in the lower section of the load path but still had doubts about the below deck chain plate area despite it having had a clean bill of health from the professionals. It just looked a bit lightweight however I was happy enough to go to sea with it and decided to monitor it.

Around 2000 seamiles later we made landfall in Opua NewZealandfollowing a 900 mile beat to windward into large seas. A test for babystay and crews alike!

My grandpa taught me that if you fix a problem in one part of a dynamic system then be ready for it to pop up somewhere else. He was wise in these matters and right in this case too because having succeeded in anchoring the bulkheads in place, the slightly under engineered, chainplate reinforcement now found itself with too much work to do. When I stripped the headlining away to inspect the area I noticed some movement in the plate, the edge of the tabbing to the plywood bulkhead and that the tabbing made a hollow noise in certain places when tapped. Removing the plate and cutting the loose tabbing away behind it revealed that the bolt holes had become elongated.

Backing plate and tabbing removed revealing elongation of holes in bulkhead

It was time to replace that piece of bent brass with something a bit more workmanlike and to renew the bond between the bulkhead and the deck.

Working inside boats with sticky or dusty materials is always difficult as the mucky stuff always seems to wander and attach itself to something that it shouldn’t, particularly when you are working above your head, so I masked up well before starting.

Masked up ready for dust and sticky resin

I got some 40mm stainless angle iron out, cut it, had it welded and pre-drilled it.

< Cut and welded stainless angle reinforcements>

I then went to town on the laminate around the chain plate cutting away the “dead” tabbing and adding around 7mm of heavy multi axial tabbing tape to the existing matrix with epoxy resin then bedding the new reinforcement onto it.

Removing dead tabbing

Heads side reinforcement bonded and bolted

The top reinforcement has provision for a link to the hull reinforcement to be achieved by adding a vertical strap should it be necessary to reduce the role of the bulkhead in load path (just in case Grandpa’s adage strikes again).

My recommendation to Sealord and Oceanlord owners would be; check your deck for a bulge around the babystay and if you suspect one then lift the floor outside the forward heads door. If there is no link between the heads bulkhead and the hull then think about having one put in. If there is a link then remove the headlining and take a look at how the bulkhead tabbing is doing.

 

 

Cap/Lower shrouds

There appear to be two weaknesses with these chain plates. Firstly they have a threaded section within the deck matrix and, particularly if the V profile is not well aligned with the angle of the shroud (the second problem and noted on a number ofWesterlyboats including Camomile), water ingress can occur. The combination of salt water immersing the thread and flexing seems most likely to be the cause of a failure such as the one below.

A U bolt failure mode (courtesy WOA)

I know of at least 2 cases of these chainplates failing and feel that in the Sealord the lower shrouds present the greatest risk due to the amount of dynamic load going through the system in a seaway.

Checking for this type of problem is as easy as firstly taking a visual check on alignment. If the upside down V of the chainplate is misaligned with the shroud at all then remove it and either replace it or have it recranked to the right angle. Secondly pull the plate out completely and inspect the “hidden” threaded part for cracks.

Small footprint and insufficiently cranked

< Suspect chainplate with sealant suggesting prior movement & leakage>

Camomile had one poorly aligned plate and one leg with pitting from corrosion on it so I decided to replace all four fittings keeping the good fittings as back-up (get me to a yard) spares.

The “pure and Christian” fix would be to change the plates out for the RCD version and I am at something of a loss why Westerly did not use this design in the first place as my Babystay is anchored on this style of plate anyway.

Babystay RCD type chainplate

I think however that this could be achieved as a retrofit more easily on the cap shroud plates than on the lowers partly because of the below decks arrangement and partly because of the angle of the shrouds which, for the lowers, would make for a piece of significant surgery.

In the end I decided to stick with the original style with the following changes.

  1. Increased diameter to 16mm for increased strength
  2. No threaded section within the deck to discourage corrosion driven crack propagation within the thread roots
  3. Precisely cranked angle to match the shroud alignment (18.5 degrees for Camomile’s rig).
  4. Enlarged sealing plate to combat water ingress
  5. Increased the length of the threaded leg so that the whole “hidden” section can be pulled up for inspection or resealing without having to remove the stay.

    Beefed up replacement

This meant that it was only necessary to drill slightly larger holes in the deck and trim away a slightly larger area of Treadmaster to achieve a seal. Because the design was so similar re installing took just a few hours.

Enlarge holes and seating area

My recommendation to Sealord or otherWesterly owners with the pre-RCD style chain plates is; pull them out and have a good look for cracks and crevices and don’t go on any serious passage with one that is not cranked to the angle of its shroud.

In any event have a good think about how you would respond to a breakage in the calm of your home or harbour as this is infinitely preferable to addressing it a when you are tired and all around you is rapidly turning to custard – see https://yachtcamomile.wordpress.com/job-list/response-to-shroud-breakage/ for my ideas on this.

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