Time of slack water in the Corryvreckan

[Allegro]

Hi,

Am tentatively planning a cruise from Ardfern to Iona in 10 days time. Its neaps, and if the weather's suitable we'd probably go straight through Corryvreckan rather than up the Sound of Luing, but the pilot book's on the boat and I wondered if anyone had the time of slack water there. I'd choose to go through with the last half hour of the flood, and have a feeling it turns eastward about 1 3/4 hours before HW Oban. Has anyone got the books at home (or memory!) to confirm that?

Cheers
Patrick

 

[Bodach na mara]

You may be able to get a prediction here:
http://easytide.ukho.gov.uk/easytide/EasyTide/SelectPort.aspx
The nearest "port" seems to be "Loch Beag" which looks like Crinan to me. There is certainly a dot for Oban. (You select the location from yellow dots on a map.)

 

[Richard10002]

"the W going stream in the gulf begins at HW Oban +0410, and the E going at HW Oban -0210.....

Slack water occurs at HW Oban +0400 and -0230 and lasts almost 1hr at neaps but only 15mins at springs....."

page 468 Reeds 2006.

Hope this helps

Richard

 

[Kantara]

Hi
according to the Almanac, West Going stream starts HW Oban + 0410, Eastgoing HW Oban - 0210. Slack water occurs at HW Oban +0400 & -0230 and lasts nearly an hour at Neaps.
Hope the weather is better than this week - I'm setting off at the same time for Ireland!
Must type faster

 

[PembrokeshirePromise]

Having dived it - I'd say it was brief and unpredictable - but the official position is:

From:

http://www.whirlpool-scotland.co.uk/images/whirlpool/pilot.doc

Tidal streams
7.255
The strength and direction of the tidal streams in the Gulf of Corryvreckan depend on the difference in sea levels at the two ends of the gulf, as given in 7.11. At the E end the range at spring tides is 1.5 m and that at the W end is 3.4 m, and HW is 30 minutes earlier at its E end than its W end. Computations from these date show that the stream should be slack at 2 hours before HW and before LW at the E end. Also, that the W-going stream should be strongest 1 hour after LW at the E end and that the E-going stream should be strongest 1 hour after HW at the E end.
In the Gulf of Corryvreckan the higher and lower levels, which differ by more then 0.9 m at spring tides, are only 1 mile apart; in consequence the stream have very high rates during spring tides. See caution at 7.253.
Within the gulf these streams set as follows:

Interval from HW Oban Remarks
+04.10 W-going stream begins
- 0210 E -going stream begins

The rate of the W-going stream is 8 1/2 kn at spring tides and that the E-going stream is rather less.
In the channel between Eileen Mór (56º 08.7N, 5º44’.6W) and Jura the W-going stream is weak but the E-going stream sets strongly NE forming a race.
Beyond the Gulf of Corryvreckan the W-going stream extends W into the Firth of Lorne, as given at 8.70. and the E-going stream extends ESE as given at 7.139.
7.256
Eddies and overfalls. During the W-going stream eddies form on both sides of the main stream. Off the SW extremity of Scarba the eddy, which sets very strongly to the E. begins at +0510 Oban. This eddy meets the main stream over the inequalities of the bottom off Cams nam Bairneach, in the vicinity of a rock with a least depth of 29 m over it, 3 cables SSW of the bay.
This interaction causes violent and dangerous turbulence, resulting in the formation of a whirlpool known locally as The Hag, which wells up in a position downstream of the 29 m rock to a height of several metres and creates a roar which can be heard at a considerable distance.
From this position heavy overfalls extend W, indicating the decision of the eddy from the main stream. Close S of the overfalls the stream may be setting by as much as 8 1/2 kn to the W, whilst close N of them the eddy may be setting nearly as strongly to the E.
During the W-going stream and eddy also sets E from a position 3 cables E of Camas nam Bairneach, towards and around Rubha Righinn, 5 cables farther E. On the S side of the gulf the eddies are of little importance; the W-going stream forms a small eddy to the W of Carraig Mhór, the N extremity of Jura, and another in the bay N of Bàgh Gleann nam Muc, 6 cables WSW.
During the E-going stream, a W-going eddy sets around Rubha Righinn and along the S coast of Scarba which creates slack water at Bàgh Gleann a’ Mhaoil (7.272) (56º10’N, 5º41’W). On the S side of the gulf, between Eilean Mór and Jura, an eddy sets W and SW round the N of Eilean Mór, creating overfalls where this eddy meets the main stream.
For further details see Admiralty Tidal Stream Atlas: North Coast of Ireland and West Coast of Scotland


Or everything you never wanted to know about it:
http://www.lulu.com/items/volume_1/54000/54076/1/preview/corryreport.PDF

Concludes there is about 2GW of power in the gulf !

 

[machurley22]

Patrick,

Have you seen Claymore's Definitive Tidal Gate Table

Dave

 

[claymore]

I was just about to mention that!

 

[machurley22]

What kept you?

No west coast chart table should be without one. BTW what colour would you say it was?

 

[claymore]

Grey of course!
I've been away for much of this week so only saw it last night. Out again today until tomorrow evening.
Up to the boat sometime midweek next week - either late wednesday eve or crack of sparrowsfart on Thursday.
You around?

 

[machurley22]

Sadly no, I'm working next weekend.

Now that I come to think of it I'm probably working this weekend too since I have placed Silkie and self at the disposal of that awfy nice Webthang chap, starting ramorra.

 

[claymore]

Es oor wee pal webnut onywhaur near tae crackin a bottle tae celebrate completion of his joblist?

 

[machurley22]

From the length of the weekend job list I've just received from him you'd have to say that he's nearer but not quite near enough to be defined as near, as such, as yet.