Knowing your tides and their heights is key to conquering the fearsome Plateau des Minquiers, says Ken Endean
Roughly half way between Jersey and Brittany, the Plateau des Minquiers is the southernmost part of the British Isles and is also widely regarded as being the scariest part for small boat sailors.
This is hardly surprising as it is a vast reef with hundreds of granite fangs, swept by strong tidal streams.
At high water, practically everything is submerged apart from the tiny Maitresse Ile, a jumble of rocks and boulders that supports a dozen stone huts, a helicopter landing pad and a toilet.
Pilotage advice for entering Les Minquiers (The Minkies to its friends) has always involved a degree of approximation, compounded by some errors in published information.
Until 2004 the largest-scale UKHO chart contained mistakes and at least three pilot books added questionable advice.
On the current chart the earlier glitches have been eliminated but shifting sand banks are introducing further complications.
For British sailors, pilotage advice has traditionally assumed that they would start from St Helier and enter the Minkies from the north, closing the Demies des Vascelin buoy (see routes chartlet) before identifying the northern beacons and aligning themselves with the transits.
In the approaches to Maitresse Ile the water becomes calmer as the tide falls, when the western rocks begin to uncover and act as breakwaters, so it may be sensible to arrive during the ebb.
However, if prospective visitors sail from St Helier during the ebb they will have to crab across strong west-going currents.
For Minkies first-timers, this will add stress to a situation that may already feel stressful, and in light winds (advisable for a Minkies visit) it may be necessary to burn fuel in order to keep to schedule.
After making a few expeditions to the Minkies, Mary and I now prefer to adopt a relaxed approach by starting from the Iles Chausey, departing at high water and simply dropping down-tide to the westward, to enter the Minkies from the south.
In 2015 a spell of fine weather prompted us to repeat this strategy, with the intention of checking any recent changes before returning to Chausey on the evening flood.
In from the south
A yacht approaching Maitresse Ile will sail over and between various drying rocks and banks. Therefore the most important part of our passage plan was a tidal curve calculation to predict the height of tide at hourly intervals during the day.
Before passing over or close to a submerged obstacle, we wanted to know the depth of water that should be covering it.
When aiming to steer between or around visible rocks, using them as navigation marks, we needed to know the times when they would be exposed to view.
A list of tidal heights, hour by hour, would enable us to deduce this information by comparing the charted drying heights with the predicted tidal heights.
Our westward passage was a gentle reach in a light southerly breeze until we turned on to the 347º southern transit, defined by a white pillar and two vertical white discs on the Rocher du Sud Bas (see main chartlet below).
At nearly half tide down there was only a slight cross-current. This transit line changes to an unmarked zigzag, which looks tricky but a lot depends on the height of tide.
One would normally begin the zigzag by turning to steer NW when abeam of Petit Rocher du Sud Bas.
On this occasion, that rock was just below the surface but precision was unnecessary because the height of tide was 7.5m and there would be ample depth of water over the 4.2m drying rock that lies SW of Rocher du Sud Bas.
On a previous visit we had arrived with the height of tide about 3.8m, when the 4.2m drying rock was exposed and were able to simply steer between it and Rocher du Sud Bas. (NB. Some pilot books have shown the 4.2m drying rock as much lower, or have ignored it completely.)
The second part of the zigzag is not guided by any visible marks – I normally turn to steer 005º when the transit beacons bear NE – but again it was not essential to maintain an accurate track because we knew that we would have plenty of water over the nearest hazard, the 2.2m drying outlier of Rocher du Sud.
The next leg is 078º towards the Rocher Blanc beacon (cross supplemented by white stripe on rock and red board); the exact line is probably not critical and steering on a compass bearing used to be adequate before the red board was installed.
According to my measurements the sandbank south of the Demies beacon dries by around 1.5m but it may be higher at times; several small drying rocks are shown on the chart but they appear to be lower than the bank.
However, two rock spurs that extend south of Maitresse Ile dry by approximately 5.5m and 4.1m (my estimates) and the final 008º transit (Rocher NE striped beacon and Grande Gauliot pole with diamond topmark) leads around their eastern side.
In the 1990s two pilot books, British and French, invited confusion by advising a final leg of 038º towards Rocher NE, which would actually pass over the rock spur with the 5.5m drying head.
Both books assumed that the beacon positions were in accordance with the UKHO chart, but at that time the chart was showing all the beacons in the wrong places.
In fact, using that 038º line would be quite safe at high tide but at half tide or lower it is quite likely to involve a keel-loosening experience.
Unfortunately, advice promoting the 038º course is currently being perpetuated on at least two websites, so I can only caution navigators not to believe everything on the web.
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The northern option
The conventional way in from the north is to first close the Demie de Vascelin buoy and pick up a transit of Jetée de Fontaine de Bas beacon against the northern flagstaff on Maitresse Ile, then divert towards the Grune Tar beacon until finally turning on to the 167º line of the Rocher du Sud Bas beacons (note that the twin discs are orange when viewed from the north).
However, this Rocher du Sud Bas transit crosses a drying sandbank, which has moved further east than shown on the current chart.
Until recently it was possible to squeeze between the bank and the nearest rock, which dries by 3.3m, but in 2015 that gap appeared to be closed.
Many local boats, particularly when arriving near to low water, steer directly from Jetée des Fontaines de Bas towards the Puffin Beacon and then through the narrow slot between Petite Gauliot and Grande Gauliot, before reaching Maitresse Ile by crossing a low neck between Rocher NE and Rocher Blanc.
That low neck is more sand than rock but there are a few hard lumps, therefore slow speed and a bow lookout are advisable.
Between Jetée des Fontaines de Bas and Puffin, Jetée des Fontaines dries by 7.4m and makes a useful lateral mark when it is uncovered and visible.
The usual anchorage is on sand between Maitresse Ile and Rocher NE.
Local advice suggests turning off the 008º transit when the southernmost hut chimney is on line with the prominent black-and-white toilet, although by that point it is normally possible to con a yacht by eye, with submerged rocks visible as dark masses against lighter sand.
The sand dries by about 1.2m and most yachts will lie afloat at low water neaps.
For fin keels and low spring tides it should be safe to anchor on the lines of the approach transits, but it is always sensible to make a visual check for rocks as the tide falls.
During our visit, a French flagged Trapper arrived late and anchored in poor light.
At low water in the morning its skipper was alarmed to find that he was almost on top of the 4.1m drying rock. Perhaps he came in on the 038º line.
At low tide, the water around Maitresse Ile was placid, with no swell, and we rowed ashore to the long landing slip.
The stone huts, some of which have been modernised internally, perch on top of what looks like a huge heap of rubble but at high tide the sea is very close.
They survive because the reef to the west disrupts big waves.
Rest and home
After a spell ashore, we returned on board, raised the anchor and started to sail away, only for the wind to fade completely.
We decided to return to the Maitresse Ile anchorage for the night. There is a mooring laid by the States of Jersey but when we borrowed it on a previous visit our boat spent the whole night thumping against the heavy Hippo buoy.
This time we chose to anchor, leaving the buoy for a visiting French catamaran and carefully checking that our swinging circle was over sand, between the buoy and the rocks by the Puffin beacon.
The sun was out and the sea calm, so Mary decided to go for a swim. We were soon joined by one of the hut owners and a party of day-trippers from St Helier, all wanting to inspect ‘the loo’, the most renowned piece of local architecture.
For small boat skippers, the Minkies may be an acquired taste but after several visits I am coming to the opinion that they can be a more convenient destination than Les Écrehou, Jersey’s other offshore reef.
At the Minkies there is more room for anchoring and if conditions deteriorate retreat is possible in any of three directions.
The worst scenario would be an increasing wind during poor visibility or at night.
Then, even with a chart plotter, conning a boat between unseen rocks in a cross-current would be nerve-racking. However, while the tide is fairly low the water between the rocks should remain relatively flat.
When the sea rises to about half tide level many of the risks are eliminated because most of the reef’s outliers are covered by at least 2m of water.
The best way to remain in control of the situation is to know the height of tide at all times.
As the evening flood covered the rocks between the Puffin Beacon and Maitresse Ile, some swell entered the anchorage but at 2 hours before high water the current swung to flow NW and London Apprentice became more comfortable, lying with her stern to the incoming waves.
The wind was forecast to become SW4-5 overnight and that might have induced us to make a hasty departure.
However, during the hours of darkness the tide would be falling and with low water soon after dawn we expected to be sheltered until the next flood submerged the rocks to windward.
Morning light brought a wind of SW3-4, gradually increasing, and the French cat left early, heading south.
We opted for a downhill sail to Jersey and took time for breakfast before departing via the northern transits.
On crossing the northern sand bank we noted the depth and calculated a drying height of 4.1m.
The east-going tide was fairly weak across the reef and became much stronger at the Demie de Vascelin buoy, but with wind on our quarter we enjoyed a fast broad reach all the way to St Aubin, where the pleasant anchorage north of the fort has absolutely no rocks.