What is the route?
Image: Visit Isles of Scilly
Why sail this route?This interior cut joins the west and east seaward approaches to St Martin’s so a vessel may effectively circumnavigate the island with a sufficient rise of the tide. This route can be used in conjunction with Old Grimsby Sound from St Mary’s Road to connect St Mary's Road and Crow Sound with all of the principal anchorages in the northeast and east end of the group as follows:
- • Close south of the 'Hats' commencement waypoint is the Watermill Cove (St Mary's) anchorage.
- • The initial fix for Higher Town Bay (St Martin's) is crossed on the approach to the 'Central' waypoint.
- • The 'Central' waypoint aligns the path through to Tean Sound .
- • But, alternatively, it is perfectly possible to continue along the Men-a-vaur alignement to St Helen's Pool (St Helen's Island).
- • Or, cut accross to connect to Old Grimsby Sound from St Mary’s Road for Old Grimsby (Tresco).
The route may also be very easily adapted to pass Tean Sound and St Mary’s Road connects two of the group’s principal deepwater berthing locations and makes the facilities of St Mary’s Harbour and Hugh town more readily accessible for vessels in Tean Sound.
Image: © Tom Corser 2009 via CC BY-SA 2.0
In a group where no anchorage provides complete protection, all of the time, and vessels have to prepared to shift in order to make the best of the weather, this ability to quickly cut between all of these anchorages is more than useful. Likewise, with a least depth of about 0.5 metres this should not prove over limiting and particularly so during Neaps when, with a tidal range of 2.3 – 5 metres, it is a reasonably available option for most vessels most of the time. Using this internal cut saves hours of sailing for those planning to pass around the north side of St Martin's. In suitable conditions, it can also provide an enjoyable piece of pilotage.
Tidal overviewToday's summary tidal overview for this route as of Thursday, December 8th at 09:55. With large a small section of this route drying to 0.4 metres, a rise of tide will be required for vessels carrying any draft. Vessels carrying up to 1.3 metres can as a general rule proceed 1 hour after LW and freely pass during Neaps. Vessels of 1.8 metres should wait for 2 hrs after LW, which the timer set for 4 hours before and, conservatively, 2 after. For more detailed work:
MHWS 5.7m MHWN 4.3m MLWN 2.0m MLWS 0.7m
Highest Astronomical Tide (HAT) 6.4m, Mean Sea Level (MSL) 2.91m
Shallow (HW +2 to -4 Hours)
(HW ST. MARY'S +0200 to -0400)
(Tidal flow )
Ends in 02:59:27
(Thu 06:30 to 12:55)
Tidal Window (HW -4 to +2 Hours)
(HW ST. MARY'S -0400 to +0200)
Starts in 02:52:26
(Thu 12:48 to 18:48)
What are the navigational notes?
The cut through the flats requires moderately good visibility and an adequate rise of tide to pass over its shallowest point of 0.4 LAT to the northwest of Gunter’s Island. As it is shallow with parts that dry at LAT, with close-lying rocks and ledges, good charts/plotters are key.
It is essential to understand that this route relies primarily upon eyeball navigation with clear visibility and moderate conditions. The route waypoints are a great addition but are not to be relied upon in isolation. They are only intended to assist in identifying the key turning points in the passage and the ledges, rocks and shallows are all best negotiated by keeping a watchful eye. Do not let this be in any way discouraging as the water here is crystal clear over white sand and the ledges have a large amount of weed that cling to then. So everything is highly visible.
Be prepared to take this route under power, in a steady fashion identifying the rocks and marks through the passage along the way. Conservatively planning for a maximum drying height of 0.5 meters LAT or a little more will provide adequate water for most leisure craft at half-tide with the prudent making the approach during the rise. However, this is not a passage a newcomer should attempt at night nor on the ebb.
Image: Michael Harpur
With sufficient tide run into Crow Sound’s 'Hats' waypoint, about 200 metres northwest of Hats south cardinal, VQ(6)+LF1.10s. Then steer the on the 322° (reciprocal 142°) transit of the gap between the two highest summits of Men-a-vaur in line with St Helen's Landing Carn which is a prominent lump of rock Landing Carn at the southwestern end of St Helen's.
Image: Andrew via CC BY 2.0
Just over ¾ of a mile further along, the transit passes 300 metres to the southwest of Gunter's Island. Guther's Island is easily recognised by its twin flat-topped rocks, 12 metres, and its surrounding rocky ledges. The alignment keeps sufficiently clear to avoid the Lower Ledge, drying to 3.3 metres, and then the Higher Ledge, drying to 4 metres, that lie midway between the track and the island. The shallowest and only drying section for this route lies beyond Higher Ledge where it dries to 0.4 LAT. It is passed over once the vessel arrives at the 'Central' waypoint located ¼ of a mile further along when St Mary's TV Tower should be due south.
Image: Michael Harpur
Arriving at the 'Central' waypoint provides the aforementioned option of staying on the 322° (reciprocal 142°) transit between Men-a-vaur and St Helen's Landing Carn for St Helen's Pool (St Helen's Island). The alignment will take a vessel safely into the anchorage, 1 mile from this waypoint, passing its shallowest part, drying to 0.7 metres, east of the awash Scattered Rocks that lie close southeast of the always visible Great Cheese Rock, 3.2 metres. The alignment is at its narrowest part between the Chinks Rocks, awash LAT, and Hunters Lump, dries 0.9 metres which are close, either side of the transit. The south end of the Chinks Rocks are ½ a mile due east of the ruin on Block House Point (Tresco).
Or, alternatively, it is also possible at the 'Central' waypoint to turn west for Lizard Point, less than ½ a mile, to connect with Old Grimsby Sound from St Mary’s Road for Old Grimsby (Tresco).
Image: Visit Isles of Scilly
To continue on to Tean Sound break off the transit at the 'Central' waypoint and steer for the 'Broad Ledge' waypoint located 200 metres west of Broad Ledge north-western end.
With Broad Ledge abeam to the east, proceed northward to 'West Broad Ledge' waypoint. This is located 200 metres east of Broad Ledge West and about midway between it and Stephen’s Ledge and Dog Ledge to the east.
Image: Andrew Abbott via CC BY-SA 2.0
Then continue to the northwest of West Broad Ledge steering to pass between it and John Martin’s Ledge to the south end of 'Tean Sound South' waypoint.
Image: Michael Harpur
The water is deep before John Martin's Ledge and when the ledge passes abeam the southern end of Tean Sound will have 5 metres or more.
The complete course is 1.78 miles from the waypoint 'Hats' to 'Tean Sound South' tending in a north north westerly direction (reciprocal south south easterly).
Hats, 49° 56.246' N, 006° 17.226' W
200 metres northwest of Hats south cardinal, VQ(6)+LF1.10s.
► Next waypoint: 1.20 miles, course ⇓ 322.13°T (reciprocal ⇑ 142.13°T)
Central, 49° 57.196' N, 006° 18.374' W
On the Men-a-vaur in line with the landing cairn on the southwest corner of St Helen's on 322° T, 0.4 miles northwest of Gunther' Island and due north of St Mary's TV Tower.
► Next waypoint: 0.21 miles, course ⇓ 38.75°T (reciprocal ⇑ 218.75°T)
Broad Ledge, 49° 57.357' N, 006° 18.173' W
160 metres westward of the northwestern end of Broad Ledge.
► Next waypoint: 0.23 miles, course ⇓ 352.79°T (reciprocal ⇑ 172.79°T)
West Broad Ledge, 49° 57.581' N, 006° 18.217' W
Midway between West Broad Ledge on the west and Stephen’s Ledge and Dog Ledge to the east.
► Next waypoint: 0.14 miles, course ⇓ 329.92°T (reciprocal ⇑ 149.92°T)