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Western cut into the Tesco Channel (Scilly)

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What is the route?
This is a cut from the western side of the Isles of Scilly into the Tresco Channel that lies between the islands of Tresco. It is approached and entered to the south of the Northern Rocks and Mincarlo, to pass in between Bryher and Sampson. The passage between the islands is deep but the Tresco Channel itself is shallow and drying.

Why sail this route?
With deep water leading all the way in between the islands, a commencement point than can be confidently identified by the 'Steeple Rock' West Cardinal and the vast majority of supported by a leading alignment, this cut is very straightforward cut.

The pass between Sampson and Bryher as seen from Bryher with Yellow Rock in the

Image: Michael Harpur

It provides a convenient western approach into the Tresco Channel and thence to New Grimsby Sound Click to view haven connecting with Tresco Channel crossing the Tresco Flats Route location. This cut in may also be used to provide a deeper approach to New Grimsby Sound from St Mary’s Road. By using the North West Passage Route location to the 'Steeple Rock' West Cardinal it provides a means of avoid the shallower sections of the Tresco Channel crossing the Tresco Flats Route location between The Hulman and Little Rag to enter from deep water to the north of the sand spit on Tresco Flat. All that is required to continue to New Grimsby Sound is a sufficient rise of tide to pass over 0.7 metres LAT, as opposed to 1.7 to cross the sandbar on the flats. It may also provide an easier exit out of New Grimsby during fresh winds from the northwest, round through north, to the northeast, when it can be difficult to depart. In suitable conditions, it can also provide an enjoyable piece of pilotage.

Mincarlo to the northern rocks, a deadly coast in poor conditions
Image: Michael Harpur

However, it should always be borne in mind, that this cut requires fair weather and settled conditions with good visibility. It should not be attempt in any developed westerly component winds or if there is any significant swell. In any such conditions, the Northern Rocks and the shoals and outliers to the west of Bryer and Sampson are very particularly ugly and make for a formidable lee shore. But more specifically there are covered rocks that lie very close to the alignment mark on both sides of the approach and should a vessel be pushed off the alignment it a very dangerous situation could develop very quickly.

Please note

The current tidal event is springs so expect streams to be at their strongest.

What are the navigational notes?
Please use our integrated Navionics chart to appraise the route. Navionics charts feature in premier plotters from B&G, Raymarine, Magellan and are also available on tablets. Clicking the 'Expand to Fullscreen' icon opens a larger viewing area in a new tab.

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Please zoom out (-) if all of the waypoints are not displayed.
The above plots are not precise and are indicative only.


Mincarlo Island, as seen over Bryher's Colvel Rocks, with the Steeple Rock
cardinal just visible

Image: Michael Harpur

Use the North West Passage Route location to arrive in an area about 250 metres south of 'Steeple Rock' west cardinal marker buoy, Q(9)15s. It is moored about 350 metres southwest of the rock and serves to mark both the entrance to the North West Passage and this cut between the islands. As always, beware of lobster pot buoys in and around Scilly.

Mincarlo Island
Image: Michael Harpur

From the 'Steeple Rock' waypoint steer the course bearing 058°T (reciprocal 238°T) east by northeast towards the passage which should be visible between Mincarlo Island and Bryher, passed to port, and Samson, passed to starboard, searching out the transit.

Yellow Rock sitting in a position midway between the islands
Image: Michael Harpur

The first mark is Yellow Rock which is a small rocky islet, 3.9 metres high, a little over two miles distant laying between Samson and Bryher.

Abbey Hill monument on Tresco
Image: Michael Harpur

Once this is identified look for the Abbey Hill monument situated ¾ of a mile to the northeast of Yellow Rock on Tresco. Once identified bring the monument over Yellow Rock to provides a range mark that tracks into the second 'Bream Ledge' waypoint. Keep on transit as dangers lie close to the track on both sides.

Depart the alignment after 'Beam Ledge' waypoint as the alignment soon after passes unnecessarily close to Long Ledge, that extends from Sampson, and over an isolated shoal that dries to 1.2 metres located a little over ½ a mile along the shoal.

The 'Clovel' waypoint sets up a course to pass between the Outer Clovel Rocks and the aforementioned shoal with a further outer and covered shoal with 0.9 metres LAT over it.

The cut joining the Tresco Channel
Image: Michael Harpur

From here the course continues in between Bryher and Yellow Rock into the Tresco Channel. The final waypoint is close before it dries at LAT, 150 metres south by southeastward of the isolated Lubber's Rock, that dries to 1.7 metres, on Bryher side of the channel and opposite from Appletree Point.

From here, with a sufficient rise of the tide proceed to New Grimsby Sound Click to view haven by steering northeastward to connect to the track of the Tresco Channel crossing the Tresco Flats Route location.

The view out through the pass from the front of the harbour master's posts
Image: Michael Harpur

The harbour master has placed two white posts in Cliff Field, beneath Plum Hill on the Tresco shore, that provides a transit northwest side of the sand spit clearing Lubber's Rock and the rocks from Appletree Point. It will also keep clear of Little Crab Ledge, that dries to 2.4 metres, and Great Crab Ledge, that dries to 5.3 metres.

Tresco Harbourmaster's alignment marks
Image: Michael Harpur

This may be used to converge with the track of the Tresco Channel crossing the Tresco Flats Route location to continue into New Grimsby Sound.

Plumb Hill posts in alignement
Image: Michael Harpur


The complete course is 2.48 miles from the waypoint 'Steeple Rock' to 'Lubber's Rock' tending in a north easterly direction (reciprocal south westerly).

Steeple Rock, 49° 55.320' N, 006° 24.000' W
400 metres southwest of the 'Steeple Rock' west cardinal marker buoy, Q(9)15s, and as ¼ of a mile south of the rock it marks.

       Next waypoint: 1.23 miles, course 58.02°T (reciprocal 238.02°T)

Bream Ledge, 49° 55.970' N, 006° 22.382' W
150 metres southeast of the southeastern end of the Bream Ledge (awash at high water).

       Next waypoint: 0.65 miles, course 48.46°T (reciprocal 228.46°T)

Colvel Rocks, 49° 56.400' N, 006° 21.628' W
250 metres south of the Outer Clovel Rocks and north of the shoals sitting in the alignment.

       Next waypoint: 0.61 miles, course 60.82°T (reciprocal 240.82°T)

Lubber's Rock, 49° 56.695' N, 006° 20.807' W
150 south by southeastward of the isolated Lubbers Rock, that dries to 1.7 metres, on Bryher side of the channel. It dries from here on in LAT.

What is the best sailing time?
May to September is the traditional UK Sailing season with June-July offering the best weather. The British Isles weather is highly variable, and the amount of bad weather varies quite widely from year to year. This is because they are islands positioned between the Atlantic Ocean and the large landmass of continental Europe. As a result, the entire area lays under an area where five main air masses meet and alternate:

  • • Tropical Maritime Air Mass - from the Atlantic

  • • Polar Maritime Air Mass - from Greenland

  • • Arctic Maritime Air Mass

  • • Polar Continental Air Mass - from central Europe

  • • Tropical Continental Air Mass - from North Africa

Depending on the movements of the jet stream, any and all of these air masses can come in over the isles, creating weather fronts where they meet and bringing with them all types of weather.

The prevailing winds for the British Isles as a whole are from the western quarter which generally blows for two-thirds of the year predominantly from the southwest. Gales from the westward are felt in all seasons, but from November to March, inclusive, they are most frequent and generally last three or four days. Of these, a southwest gale is considered to be the most powerful system. The winter period is largely characterised by wind and rain.

The fine summer weather of the sailing season is typically punctuated by the passage of an Atlantic depression that bringing periods of strong wind and rain, and sometimes poor visibility. These gales rarely cause surprises as they are usually forecasted well in advance. Good weather windows of 48 hours are easy to predict but any longer than that there's an increasing chance of change.

Fogs are frequent in all parts of the Channel and are formed both on the English and French coasts. In summer they only obscure the land in the morning and are readily dispersed by heat or a light breeze. But the moist haze, driven in by westerly winds from the sea, tends to linger and is only dispersed by strong winds. In the eastern part of the Channel, it is rare for the land to be completely free from mists. The only exception is when the wind is from the northeast which makes the mist free coastline highly distinctive from a great distance.

With thanks to:
Micheal Harpur eOceanic.

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