Storm tactics at anchor: Surviving gales in Scilly

The Isles of Scilly are lovely but have no harbours or anchorages with all-round shelter, so visiting yachts must be prepared to move around according to wind direction.

If a gale is forecast, some pilotage guidance even recommends retreating to the mainland.

Most yacht crews ignore that advice because, after working to reach Scilly against the prevailing winds, they are reluctant to surrender their westing.

That leaves the option of finding somewhere safe to hide. And thinking about storm tactics at anchor and on moorings.

When Storm Evert hit the islands in peak holiday season in July 2021, large numbers of yachts were in the islands.

Numerous boats dragged anchors, broke free of moorings or went aground, though many more weathered the storm unscathed.

Piecing together the events of the night, and the possible causes of the events that unfolded, make it a fascinating case study of anchoring and mooring tactics that might help other yachts weather other storms moored and anchored.

Information has been provided by Pete Hicks, Amy Caldwell and Dickon Berriman at the RNLI, Stuart Caldwell of the Maritime and Coastguard Agency, St Mary’s harbour master, Dale Clark, and marine manager for Tresco Rob Featherstone.

I’d like to extend thanks to all for their input.

When strong winds threaten, the first task is to study available forecasts and assess the likely track and timing of the associated weather feature, which will often be a depression approaching from the Atlantic.

If it is likely to pass to the south, or directly overhead, it could generate an east or south-east wind which then fades and backs to become a strong northerly, but which may allow boats to shift anchorage in the lull.

The timing can be important because shifting anchorage in a lull may be impossible at low tide, when many channels will be shallow or dry.

A depression tracking close to the north will generally be more serious, with winds typically rising from the S or SE before strengthening and veering round towards NW, often with a violent veer as the cold front passes.

Decisions and drama

Storm Evert hit Scilly on Thursday 29 July 2021. Until the day before, there had been a complex area of low pressure to the west and a Met Office forecast of unsettled conditions but nothing exceptional.

On the Wednesday, the 0500 Navtex bulletin predicted a maximum of Force 6 but in the 1100 bulletin, transmitted at 1420 BST, that had changed to: ‘cyclonic 6 to 8, possibly 9 for a time’, which prompted urgent activity among the many visiting boats.

The 0500 bulletin on Thursday was even more alarming, with: ‘west or south-west 3 to 5 becoming cyclonic 7 to 9, possible 10 later in far west’.

Mary and I had anchored our twin-keeled Sabre 27, London Apprentice, in the drying channel outside Bryher’s Green Bay.

As the new depression seemed likely to pass north of the islands, we expected winds to swing through the typical SE-S-NW arc but we knew the limits of that arc would be important, as we had previously experienced two comparable gales at Scilly.

If we anchored at Old Grimsby, close under the old blockhouse as we had in 2003, we would be protected from SE but become exposed to winds and swell if the veer went right around to NW.

In Green Bay, on the other hand, we would be exposed to wind but better protected from the NW, and in 2010 the veer towards NW had been particularly vicious.

In the end we plumped for Green Bay and moved closer inshore. During Thursday, the wind backed to SSE and stiffened before starting a very gradual veer.

At 1900 the Seven Stones Light Vessel recorded South Force 7 (steady wind speed rather than gusts).

We were exposed to increasingly vigorous wave action and at 2000 the wind reached SSW 8. A cold front was then followed by ferocious gusts and a further veer to SW.

Continues below…

That put us in the lee of Bryher and the larger waves subsided but there were breaking crests all around us in the darkness, although we were only 80m off the beach.

At 2200 the Seven Stones recorded wind at the top end of Force 9. At 0125 we touched down as the tide fell, and retreated to our bunks.

At 0400 the wind at Seven Stones was NW8 but we were comfortably aground. By late breakfast time it was all over.

The breeze was down to WNW3, the sun was out and the pressure, which had dropped from 1013 to 999mb, was back up to 1010mb.

The scene in Green Bay

There were 16 yachts in Green Bay, all taking the ground with a mixture of twin keels, triple keels, lifting keels, beaching legs and twin rudders, and all at anchor.

The flat foreshore had a layer of sand over dense shingle and pebbles.

Some skippers tried to dig-in their anchors during the morning low tide on the Thursday, but it was difficult because the substrate behaved as running gravel, and most of the anchors would penetrate further by themselves, when under load.

Modern single-fluke anchors such as Deltas, Rocnas, Mansons and Spades all performed well in the strongest wind, burying until their shanks were almost hidden.

In the outer part of the anchorage, at least one boat dragged slightly but we had noticed her sheering wildly; her motor was running slow ahead and also the tide out there was flowing to windward, both influences possibly causing the anchor chain to slacken in the lulls, so that the bow swung off in the gusts.

No boat suffered damage.

Four yachts had anchored well up the beach, near to the HW mark, so were solidly aground for much of the gale, and three other boats were further north, in a snug corner behind the commercial jetty.

A large Moody had remained at anchor in the drying channel, outside the bay, but had not dragged.

I had unintentionally carried out an experiment: the depth at HW would be 3.5m and we initially laid one Delta anchor on 20m of chain, but the wind backing to SSE threated to push us over a patch of rubble, so we laid our second Delta out to port as a temporary wing anchor, on only 16m of warp with a 7½kg chum weight but no chain.

The wind direction changed only gradually, and we actually lay to this second anchor while the strength increased to Force 8, before the veer allowed the first anchor to take the load again.

Several other skippers had used chums, which help to damp-down snatch loads and also reduce sheering.

Wider picture

Elsewhere there was chaos. For yachts caught in the Isles of Scilly in bad weather, the three most likely failures are a broken mooring connection, a dragged mooring or a dragged anchor, and all three occurred during that wild night.

At Hugh Town, the St Mary’s Harbour staff had diligently warned all skippers to reinforce their strops to the visitor moorings, preferably with chain, and yet numerous strops broke or chafed through.

One yacht came adrift, then secured to a local boat and reportedly caused damage before breaking free again and driving on to rocks, where the crew were lifted off by Coastguard helicopter.

In other locations, at least two visitor moorings with single clump sinkers dragged (for the first time in anyone’s memory) and their moored boats went ashore.

There were also many instances of dragged anchors: a large ketch in St Helen’s Pool drove ashore on Tean’s outliers, and a cutter that had been anchored off Old Grimsby dragged for half a mile until grounding near Tresco’s eastern extremity.

Both rescues involved the helicopter. Several yachts also dragged off New Grimsby, in Porth Cressa and in The Cove, between St Agnes and Gugh.

Most of the dragged anchors had been laid in relatively deep water and many came up swathed in weed.

Three yachts anchored inside the bay at Old Grimsby, where they took the ground at low tide; they were on clean sand and remained secure.

As the local lifeboat was much in demand and suffering problems on one engine, the Sennen Cove Tamar-class lifeboat battled out from the mainland to assist.

The former’s small Y boat was also in action over low tide, when the depths were shallow, and the crews worked heroically through the night.

Other vessels lent a hand: a Tresco harbour boat assisted several yachts off New Grimsby and in Green Bay a boatyard RIB helped at least one yacht by re-positioning a stern anchor.

Storm tactics at anchor and on moorings: How to avoid problems

Mooring

The buoys in St Mary’s harbour are on a ground chain grid and highly unlikely to shift.

However, they are slightly outside the harbour and in a westerly wind will be very uncomfortable indeed.

To put it another way, if the Earth was flat, those moorings would have a good view of America, with nothing in between.

Pete Hicks, coxswain of the St Mary’s Lifeboat, offers the following advice: ‘If possible, have a mooring strop made up that fits your boat’s cleat layout, with a rubbing patch for across the stem rollers with a thimble and a good shackle to attach to the mooring itself. Many of the incidents we see of yachts breaking their moorings is after a rope which has just been passed through the mooring buoy’s chain or shackle chafes out. At least take a turn in the chain to stop movement or tie off the rope with a suitable knot (round turn and 2 half hitches or Anchor bend). If you don’t have one of these, spread the load, use plenty of ropes. Attach to different points on the boat, not just one cleat. The windlass is a good place.’

The moorings are also very close together, so a boat that breaks adrift is likely to collide with others.

Elsewhere, visitor moorings with heavy clump sinkers should be okay in most conditions.

However, the buoys at New Grimsby, Old Grimsby and Tean Sound are in deep water and exposed to winds blowing along their channels, from NW or SE, when their motion can become violent.

Anchoring

In Green Bay many of the yachts were, like us, lying to short scopes to avoid tangling with one another, and yet all anchors held, most of them without budging.

Elsewhere, at least one of the yachts that dragged in deep water had her CQR on about 100 metres of chain but that did her no good.

Our second anchor was on a scope/depth ratio of less than 4 to 1 (measured from the stem head) so when the warp lifted the chum it would have been pulling upwards at about 15º, and yet the anchor remained solidly embedded, in winds of near gale force.

Much is written about the need for lots of chain on the bottom but I reckon it is even more important to ensure that the anchor has connected properly to the seabed.

In Scilly, that generally means using a modern anchor and anchoring on sand, so that the hook can dig in cleanly.

In Green Bay, we had it easy because there is little weed, but in deeper water it is essential to look for patches of light-coloured sand.

The dark areas indicate weed, which may be loose or may be growing on rock or boulders, which is just as bad.

Our Delta anchors are surprisingly effective in boulders, but I would not trust them to hang on to the lumps in a Force 9.

Hiding from the elements

Whatever the likely wind directions, finding a spot with good shelter will be easier with a boat that can take the ground – just like all the working craft that once frequented the islands.

A twin-keeler will be the best option, because it is unlikely to be damaged if it swings on to rubble, but a single-keeled yacht will become a much safer vessel for the Isles of Scilly as soon as its owner fits beaching legs.

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