Some help with tide please!

[sailorman]

Come on have some backbone! Shallow stuff! Never less than 2ft under the keel!

I jest of course - 'tis over 6nm longer though.[/QUOTE]
That all depends on wind angle at the time ,unless one motors the whole way through the banks & the traffic in & out of London

 

[Tiller Girl]

"Cheese"

How did you know that I ate too much cheese with that brandy last night?

 

[Tiller Girl]

Come on have some backbone! Shallow stuff! Never less than 2ft under the keel!

I jest of course - 'tis over 6nm longer though.[/QUOTE]
That all depends on wind angle at the time ,unless one motors the whole way through the banks & the traffic in & out of London

'tis a very good point. Actually just working the tables now.....

 

[Bru]

Via Foulgers and the Little Sunk 'cos I was a twonk yesterday ...

Dover > Harwich #2
Leg to WP Latitude Longitude Bearing Distance Fuel Leg time (no tides) Leg time (incl.tides) CTS ETA (incl. Tides)
Dover East 51° 07'.300N 001° 20'.700E Start 05:00 Saturday, August 22, 2015
1 St Margarets 51° 08'.600N 001° 24'.400E 60.8° 2.66 0.71 35 mins 24 mins 60° 05:24 Saturday, August 22, 2015
2 S Brake 51° 15'.800N 001° 26'.900E 12.3° 7.37 1.96 01 hours 38 mins 01 hours 18 mins 11° 06:43 Saturday, August 22, 2015
3 N Foreland 51° 22'.800N 001° 27'.800E 4.6° 7.02 1.87 01 hours 33 mins 01 hours 28 mins 1° 08:11 Saturday, August 22, 2015
4 Long Sand Outer 51° 34'.588N 001° 28'.362E 1.7° 11.79 3.14 02 hours 37 mins 02 hours 51 mins 355° 11:03 Saturday, August 22, 2015
5 Long Sand Middle 51° 35'.559N 001° 26'.343E 307.7° 1.59 0.42 21 mins 22 mins 322° 11:25 Saturday, August 22, 2015
6 Long Sand Inner 51° 38'.783N 001° 25'.337E 349.0° 3.28 0.88 43 mins 55 mins 351° 12:20 Saturday, August 22, 2015
7 Little Sunk East 51° 41'.220N 001° 24'.970E 354.7° 2.45 0.65 32 mins 50 mins 3° 13:10 Saturday, August 22, 2015
8 Clr Gunfleet 51° 48'.400N 001° 25'.202E 1.1° 7.18 1.92 01 hours 35 mins 02 hours 11 mins 11° 15:21 Saturday, August 22, 2015
9 Landguard 51° 55'.376N 001° 18'.812E 330.5° 8.01 2.14 01 hours 46 mins 01 hours 43 mins 331° 17:05 Saturday, August 22, 2015
10 Harwich Shelf 51° 56'.881N 001° 18'.207E 346.1° 1.55 0.41 20 mins 22 mins 341° 17:27 Saturday, August 22, 2015
______ ______ _____________ _____________
Totals 52.91 14.11 11 hours 45 mins 12 hours 27 mins
Nm Litres using 4.5 knots using 4.5 knots
(Plan speed) (Plan speed)

Or an 02:00UTC departure which makes for a much quicker passage time ...

Dover > Harwich #2
Leg to WP Latitude Longitude Bearing Distance Fuel Leg time (no tides) Leg time (incl.tides) CTS ETA (incl. Tides)
Dover East 51° 07'.300N 001° 20'.700E Start 02:00 Saturday, August 22, 2015
1 St Margarets 51° 08'.600N 001° 24'.400E 60.8° 2.66 0.71 35 mins 29 mins 61° 02:29 Saturday, August 22, 2015
2 S Brake 51° 15'.800N 001° 26'.900E 12.3° 7.37 1.96 01 hours 38 mins 01 hours 20 mins 12° 03:49 Saturday, August 22, 2015
3 N Foreland 51° 22'.800N 001° 27'.800E 4.6° 7.02 1.87 01 hours 33 mins 01 hours 11 mins 358° 05:01 Saturday, August 22, 2015
4 Long Sand Outer 51° 34'.588N 001° 28'.362E 1.7° 11.79 3.14 02 hours 37 mins 02 hours 30 mins 356° 07:31 Saturday, August 22, 2015
5 Long Sand Middle 51° 35'.559N 001° 26'.343E 307.7° 1.59 0.42 21 mins 22 mins 296° 07:53 Saturday, August 22, 2015
6 Long Sand Inner 51° 38'.783N 001° 25'.337E 349.0° 3.28 0.88 43 mins 39 mins 340° 08:32 Saturday, August 22, 2015
7 Little Sunk East 51° 41'.220N 001° 24'.970E 354.7° 2.45 0.65 32 mins 28 mins 349° 09:00 Saturday, August 22, 2015
8 Clr Gunfleet 51° 48'.400N 001° 25'.202E 1.1° 7.18 1.92 01 hours 35 mins 01 hours 29 mins 357° 10:29 Saturday, August 22, 2015
9 Landguard 51° 55'.376N 001° 18'.812E 330.5° 8.01 2.14 01 hours 46 mins 01 hours 58 mins 335° 12:28 Saturday, August 22, 2015
10 Harwich Shelf 51° 56'.881N 001° 18'.207E 346.1° 1.55 0.41 20 mins 18 mins 352° 12:46 Saturday, August 22, 2015
______ ______ _____________ _____________
Totals 52.91 14.11 11 hours 45 mins 10 hours 46 mins
Nm Litres using 4.5 knots using 4.5 knots
(Plan speed) (Plan speed)


There are some interesting variations in the difference in passage time between leaving at 02:00 and 05:00 which I've no way of telling whether they are genuine consequences of the tidal streams or artefacts of the software extrapolation of the tidal stream data

Whichever route you choose, clearly a before dawn start is the option if you want the fastest passage time. But a more civilised start time isn't a disaster. Three hours longer in bed at the price of an hour or two more at sea

I await the manually worked up info with great interest (genuinely - it is most interesting to compare the two)

 

[Vara]

Be interesting to see what TG comes up with, as I'm sitting in Ramsgate with TG's book in front of me working up the same passage.

 

[Tiller Girl]

Four potential routes:

1. Dover - Foulger's - Little Sunk - Swin - Harwich = 39.07nm
2. Dover - Foulger's - Black Deep - Goldmer Gat - Harwich = 39.73nm
3. Dover - Foulger's - Black Deep - Cork Beacon - Harwich = 42.12nm
4. Dover - Outside Route - Harwich = 46.16nm

Obviously for my book I choose the waypoints conservatively so there is the odd nm that can be picked up by an experienced trotter like the OP. But the impact on each route would be the same.

I work my routes from outside Ramsgate and use HW Sheerness as the basis so bear with me as we will have to add on Dover to Ramsgate. The timings are therefore based from Ramsgate at 4kts average boat speed on neaps.

Route 1:

Depart - 2 Sheerness = 8hrs 41 minutes
Depart - 1 Sheerness = 9hrs 3 minutes
Depart - HW Sheerness = 9hrs 42 minutes
Depart +1 Sheerness = 10hrs 44 minutes

Route 2

Depart - 2 Sheerness = 9hrs 02mins
Depart -1 Sheerness = 9hrs 18mins
Depart HW Sheerness = 9hrs 56 minutes
Depart +1 Sheerness = 10hrs 53 mins

Route 3

Depart -2 Sheerness = 10hrs 05mins
Depart -1 Sheerness = 10hrs 51mins
Depart HW Sheerness = 11hrs 28mins
Depart +1 Sheerness = 12hrs 03 minutes

Route 4

Deaprt -2 Sheerness = 11hrs 02mins
Depart -1 Sheerness = 11hrs 11mins
Depart HW Sheerness = 11hrs 41mins
Depart +1 Sheerness = 12hrs 03 minutes
Depart +2 Sheerness = 10hrs 03 minutes

So I would suggest the goal is to be 'off' Ramsgit two hours before HW Sheerness or 0342 BST on Satursday morning.

I don't do tables for Dover to Ramsgate although after this, next rainy day I will do a set but you have 14.5nm ish from Dover to Ramsgate which would take you 3.2hrs without tide but I reckon leaving Dover 2 1/2 hrs before local HW (ie 0122 outside the harbour!) is arguably going to give you 3nm of helpful tide so say 2hrs 40mins. Trouble is leaving Dover any earlier gives you the end of the adverse tide.

Bear in mind I don't do 1/2 knot tables so 4.5kts will be quicker. Of course if you had a copy of the book you could pick your favourite and work up what it would be at 5kts neaps and interpolate! The book is very reasonable you know.........

Preferred route? Ah well, depth isn't an issue for you, you can easily cross the Sunk Sand in way of the Barrow No 2 without fear. Personally I can't see the point of going down the Black Deep and then across to the Cork Sands unless it is to avoid a beat from the head of the Black Deep to Goldmer Gat - something which is to be avoided if it is really hard on the wind, in which case the diagonal across the Swin can be a nice alternative. Outside route? Yes longer in time but only because it is longer in miles. Quite efficient tide wise and depending on the wind direction may be beneficial.

 

[pvb]

Come on have some backbone! Shallow stuff! Never less than 2ft under the keel!

I jest of course - 'tis over 6nm longer though.

My old boat had an encapsulated keel, and I wasn't too bothered about occasionally gently touching the bottom (ooo er). But the new one draws 2m and is a Bavaria, so I'd prefer to avoid shallow stuff!

And, whilst it might be a longer trip, it's easier and usually quicker!

 

[Tiller Girl]

be interesting to see what tg comes up with, as i'm sitting in ramsgate with tg's book in front of me working up the same passage.

now you tell me!

Funny that, the software wouldn't let me SHOUT

 

[Tiller Girl]

My old boat had an encapsulated keel, and I wasn't too bothered about occasionally gently touching the bottom (ooo er). But the new one draws 2m and is a Bavaria, so I'd prefer to avoid shallow stuff!

And, whilst it might be a longer trip, it's easier and usually quicker!

Well that's the delight of the Estuary. You have to pick the route that suits. Wouldn't argue with that.

 

[pvb]

I'm ashamed to say I don't really do deep analysis of passage planning, but you seem to have reached the same conclusion I suggested in post #12 - leaving Dover 2 hours before HW Dover is a reasonable idea!

 

[Bru]

Seems to correlate reasonably closely (at a quick glance) to the output from the software taking into account the difference between working it at 4 knots and working it at 4.5 knots

Might be interesting to work the routes up at 4 knots in the software to get a closer comparison

 

[Bru]

And to make sure there's no misunderstanding - I have said all along that the optimum departure time is somewhere around 02:00UTC (give or take an hour depending on speed through the water). The suggestion I was putting forward was that a sub-optimal departure time at a more civilised hour and the consequent longer passage time might be preferable (and is what I'd probably choose to do)

 

[Vara]

now you tell me!

Funny that, the software wouldn't let me SHOUT

Well done TG, your answer broadly agrees with mine! .

Just in passing, I will say that although your book looks a bit daunting at first, once you start working it, it all becomes clear and is a great help.

 

[Tiller Girl]

And to make sure there's no misunderstanding - I have said all along that the optimum departure time is somewhere around 02:00UTC (give or take an hour depending on speed through the water). The suggestion I was putting forward was that a sub-optimal departure time at a more civilised hour and the consequent longer passage time might be preferable (and is what I'd probably choose to do)

Happy to agree. I was referring to the 6am start time. Of course this is one of those moments where really we should say I wouldn't start from there! But then if you have reached Dover intending to make Ramsgit, it would be daft to carry on if the tide had turned against you.

 

[Bru]

Of course this is one of those moments where really we should say I wouldn't start from there!.

 

[Tiller Girl]

There are some interesting variations in the difference in passage time between leaving at 02:00 and 05:00 which I've no way of telling whether they are genuine consequences of the tidal streams or artefacts of the software extrapolation of the tidal stream data

I have pointed out to one software company that when tides turn that they slow down and stop and then go the other way. As an example where the tide was flooding north at 000 degrees and then ebbing south at 180 degrees, their software was assuming at dead low water that the tide was heading at 090 degrees. That didn't matter of course since the flow was 0.0kts but the software calculated the flow incrementally between 000 and 090 degrees as it reduced and then between 090 and 180 degrees as the ebb started. Small errors perhaps very small.

The advantage of the tables if I may blow my trumpet for a moment is that the cause of the variations are clear - if not necessarily easy to avoid.

 

[Rivers & creeks]

I like the phrase 'sub-optimal'. Mrs Watson would not countenance a 2am departure on the basis that I would be grumpy for days afterwards. So I think it's an anchor in the harbour and a 4am departure which is frankly cruel enough. It means problems with the woofter but he'll have to have a late walk and crossed legs. Still if I do my usual which is to be nervously awake two hours before we're due to get up then I may as well get going.

 

[Rivers & creeks]

Is this the route from Foulgers?

View attachment 53204

 

[Vara]

I like the phrase 'sub-optimal'. Mrs Watson would not countenance a 2am departure on the basis that I would be grumpy for days afterwards. So I think it's an anchor in the harbour and a 4am departure which is frankly cruel enough. It means problems with the woofter but he'll have to have a late walk and crossed legs. Still if I do my usual which is to be nervously awake two hours before we're due to get up then I may as well get going.

fairly certain that if you have a word with the office, they'll let you move round to the tidal basin so you won't need to anchor.

 

[Tiller Girl]

Is this the route from Foulgers?

View attachment 53204

Yes, that'll do. There is a downloadable chartlet on my web site. Note that the UKHO has revised the depth over the remains of the LIttle Sunk beacon now to 2.3m LAT not drying as shown on this chartlet. But you are going to keep clear of that anyway which is sensible.

I'm off to play boats for a few hours where there is no interweb....