MoodySabre
Well-Known Member
TG’s latest edition has been delivered. It is a huge leap forward from the original. So much information that it is at first mind boggling but so easy to understand and plan from. Stupendous job Roger. Take a bow.
Crossing The Thames Estuary
- Thread starter MoodySabre
- Start date
tillergirl
Well-Known Member
Thanks Roger. Kind of you.
tillergirl
Well-Known Member
I have added a Utube video which explains the new tables. I am sorry about the voice; it's mine ?
ex-Gladys
Well-Known Member
As a previewer of the video I have to say Roger has done an excellent job with it. His view is that his voice is boring, I have to disagree!
Poecheng
Well-Known Member
Roger, it sounded good to me - thanks for that. Few like to hear their own voice.
And particular thanks for the SW Sunk chartlet which we used to good effect on Sunday coming from Ramsgate to the Orwell.
Coming up Barrow Deep and then into the Kings Channel, it struck me that we could nip over the Gunfleet north of the Old Gunfleet Lighthouse and therefore make a more direct line for Harwich. Is that daft?
And particular thanks for the SW Sunk chartlet which we used to good effect on Sunday coming from Ramsgate to the Orwell.
Coming up Barrow Deep and then into the Kings Channel, it struck me that we could nip over the Gunfleet north of the Old Gunfleet Lighthouse and therefore make a more direct line for Harwich. Is that daft?
tillergirl
Well-Known Member
I definitely don't like mine!
Just checked the Admiralty chart: that area of the Gunfleet hasn't been surveyed recently. Indeed it shows 'surveys 1996 - 2014'. It would be 'experimental' to try to cross there - and you would be on the ebb?
Gladys and I plan - actually Gladys hasn't exactly agreed yet - but we will go back down to the Middle Sunk on a suitable day. In September we did an 'exploratory' down there and found signs of bad and good. The bad is the north-east finger that extends from the Middle Sunk which hampers a crossing to or from the Essex Rivers but to and from the Suffolk Rivers might be good. I say might because we concentrated on the 'finger' (not very nice, very steep and would get a bit of an upwelling of tide on a windy day) rather than to complete right across down to the Black Deep (it takes time, we sort of plotted the edge of the Middle Sunk knoll down to the Black Deep). If we do a little more, it might be possible to recommend (with experience) heading north from the BDM2 (in middle of the Black Deep) until just short of 51 degree 40N and turn 045T and holding that until finding over 5m CD. Then heading straight to the NE tip of the Gunfleet.
The diagonal would avoid the unmarked wreckage of the Sunk Beacon and the 'finger. BUT I stress we should confirm what I think might be safe. I said 'with experience' because one would need to be confident that the GPS is accurate and that it would be necessary to retain on zero XTE. I also stress that Glads and I need to extend the 'exploratory' before that idea is recommended.
A word about current charts in respect to the Middle Sunk. The Admiralty issued a block in December 2021 which updated the 'finger' based on the exploratory by Glads and I, and a 2016 PLA survey. If you have an update on Navionics since March THIS YEAR, you can see the correction. If anyone is using a 2021 or older Navionics chart it would be out of date in respect of the Middle Sunk - obviously. If you use C-Map, you need to check on the format and again have an update this year (I would suggest you check against the UKHO block). Even if you have a C-Map Max format it would not be up to date. I cannot comment on other electronic charts.
The UKHO Block is copyright of the UKHO.
Just checked the Admiralty chart: that area of the Gunfleet hasn't been surveyed recently. Indeed it shows 'surveys 1996 - 2014'. It would be 'experimental' to try to cross there - and you would be on the ebb?
Gladys and I plan - actually Gladys hasn't exactly agreed yet - but we will go back down to the Middle Sunk on a suitable day. In September we did an 'exploratory' down there and found signs of bad and good. The bad is the north-east finger that extends from the Middle Sunk which hampers a crossing to or from the Essex Rivers but to and from the Suffolk Rivers might be good. I say might because we concentrated on the 'finger' (not very nice, very steep and would get a bit of an upwelling of tide on a windy day) rather than to complete right across down to the Black Deep (it takes time, we sort of plotted the edge of the Middle Sunk knoll down to the Black Deep). If we do a little more, it might be possible to recommend (with experience) heading north from the BDM2 (in middle of the Black Deep) until just short of 51 degree 40N and turn 045T and holding that until finding over 5m CD. Then heading straight to the NE tip of the Gunfleet.
The diagonal would avoid the unmarked wreckage of the Sunk Beacon and the 'finger. BUT I stress we should confirm what I think might be safe. I said 'with experience' because one would need to be confident that the GPS is accurate and that it would be necessary to retain on zero XTE. I also stress that Glads and I need to extend the 'exploratory' before that idea is recommended.
A word about current charts in respect to the Middle Sunk. The Admiralty issued a block in December 2021 which updated the 'finger' based on the exploratory by Glads and I, and a 2016 PLA survey. If you have an update on Navionics since March THIS YEAR, you can see the correction. If anyone is using a 2021 or older Navionics chart it would be out of date in respect of the Middle Sunk - obviously. If you use C-Map, you need to check on the format and again have an update this year (I would suggest you check against the UKHO block). Even if you have a C-Map Max format it would not be up to date. I cannot comment on other electronic charts.
The UKHO Block is copyright of the UKHO.
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Morpheous
Well-Known Member
What a fantastically useful post, thanks to all contributing and thanks to Roger for the book. If only Imray would let me log in so I can order it! I'm in the process of purchasing a boat at North Fambridge and will be bringing it round to Dartmouth in May if the purchase goes smoothly. First leg will hopefully be to Brighton. Any pearls of wisdom for motor boats on this trip? I'm hoping to cruise around 20 knots.
Plum
Well-Known Member
Hope your fuel tank is big enough to get you there in one leg
mine certainly isn't.Morpheous
Well-Known Member
I think I can do Brighton in one leg, fuel up then on to Dartmouth. North Fambridge to Brighton looks about 130NM. I don't know what consumption I'm going to get exactly but looking at other useful threads on this forum I found some old discussions about the very boat I'm buyingHope your fuel tank is big enough to get you there in one leg
A Princess 410. So I think I have a range of about 200NM with 20% contingency. Hopefully.tillergirl
Well-Known Member
Bizarrely, a while back, I wondered whether tides actually matter to a 20 kt passage and I drew up some second edition tables including the Crouch to Ramsgate. Mathematically if you had the worst tide at every sector, the passage would take you 30 minutes more compaired to the best tide at every sector. This data being a second edition tables, I don't have a readily available 'purple point' (I hope you watched the video?). But to do the third edition tables I have a quite large Excel file which produces full tables for 8 and 10 knots. So using the Mega+Autotable, I can see that the quickest passage at 10 kts has a departure time at the Crouch Landfall Waypoint at +3.45 Sheerness and a duration of 2hrs 48 minutes.
Using the +3.45 Sheerness start time using the 20 kt second edition tables, I predict a duration of 1hr 20 minutes (which is a lucky wild stab as 1hr 20mins is only 2 minutes worse than the theoretical best). There will be a 'window' (I hope you saw the video x 2) of course and you could start at the Landfall waypoint at +1.00 with little penalty.
30 minutes of fuel at 20 knots of course is not inconsequential - especially this season. The Landfall waypoint is in the Whitaker channel midway between the pairs 3 & 4 and 5 & 6 so you would need to plan to depart Fambridge in time (beware the speed).
But then if you plan to do one passage to Brighton, wot about the tides from Ramsgate to Brighton. Using that start time of +3.45 Sheerness, you would be at Ramsgate at +5.05 Sheerness. UKHO average Sheerness as +0120 relative to Dover, so you would be at Ramsgate at -6.30 Dover. You then carry the ebb past Dover and Dungeness. But the west going tide ends past Dungeness at -3hrs Dover. So I conclude starting at the Crouch Landfall wpt earlier.
Starting at the Crouch Landfall Waypoint at +1.00 Sheerness is predicted for a duration of 1 hr 29 minutes arriving off Ramsgate at +2.29 Sheerness (aka +3.49 Dover). Frankly that is just a little early as you would have some adverse tide (but not significant) down from the North Foreland. I have no charts west of Folkstone so I haven't got the distance Dover to Brighton but you would lose the favourable tide at Beachy Head at around +6.00 Dover.
Sorry, that's a quick look and I sort of wrote it as I thought it through. I think it is a trade off: bit of adverse Frambridge to the Crouch Landfall Wpt v ditto dropping down from North Foreland v losing the tide past Beachy Head.
Using the +3.45 Sheerness start time using the 20 kt second edition tables, I predict a duration of 1hr 20 minutes (which is a lucky wild stab as 1hr 20mins is only 2 minutes worse than the theoretical best). There will be a 'window' (I hope you saw the video x 2) of course and you could start at the Landfall waypoint at +1.00 with little penalty.
30 minutes of fuel at 20 knots of course is not inconsequential - especially this season. The Landfall waypoint is in the Whitaker channel midway between the pairs 3 & 4 and 5 & 6 so you would need to plan to depart Fambridge in time (beware the speed).
But then if you plan to do one passage to Brighton, wot about the tides from Ramsgate to Brighton. Using that start time of +3.45 Sheerness, you would be at Ramsgate at +5.05 Sheerness. UKHO average Sheerness as +0120 relative to Dover, so you would be at Ramsgate at -6.30 Dover. You then carry the ebb past Dover and Dungeness. But the west going tide ends past Dungeness at -3hrs Dover. So I conclude starting at the Crouch Landfall wpt earlier.
Starting at the Crouch Landfall Waypoint at +1.00 Sheerness is predicted for a duration of 1 hr 29 minutes arriving off Ramsgate at +2.29 Sheerness (aka +3.49 Dover). Frankly that is just a little early as you would have some adverse tide (but not significant) down from the North Foreland. I have no charts west of Folkstone so I haven't got the distance Dover to Brighton but you would lose the favourable tide at Beachy Head at around +6.00 Dover.
Sorry, that's a quick look and I sort of wrote it as I thought it through. I think it is a trade off: bit of adverse Frambridge to the Crouch Landfall Wpt v ditto dropping down from North Foreland v losing the tide past Beachy Head.
tillergirl
Well-Known Member
Reverting to my old personal question 'do tides matter at 20 kts?': doing a simple distance divided by speed (e.g. 31.42/20), on a lake would take 1hr 34 minutes. So there actually is 14 minutes tide benefit on the above. 14 minutes might not be that important but 14 minutes saved over that distance is 11%. Extrapolating that twixt Fambridge to Dartmouth seems to me to be worth saving in fuel charges. Or am I being a little twee?
oldgit
Well-Known Member
Our recent trip back from Limehouse to Rochester took about 5 hours at 10 knots over the ground. Big tide so suspect minimum 2 + knots tidal assistance.
A fag packet calculation suggests that we saved a journey time of 20% ( ish), or around a hour and a bit due to a favourable tides.
Ebb out of Thames and Flood up the Medway.
Boat uses around 12 litres of fuel an hour at those speeds.
Club is charging £1.24 per litre at the moment.
To put things in perspective was charged £18.00 quid for two tiny drinks in well known riverside watering hole.
Marmalade
Well-Known Member
New edition ordered. Invaluable resource for an east-coaster.
Poecheng
Well-Known Member
3rd Edn just been delivered - looks great.
PetiteFleur
Well-Known Member
Mine arrived yesterday - looking great.
Morpheous
Well-Known Member
Mine arrived yesterday too, thanks Roger, great work
