NealB
Well-Known Member
Thank you for that!
Yes ... I think agreeing to disagree is the only solution on this forum: but it could be, to me at least, a fascinating discussion over a pint or two.
My toast: "Safe S-curves, and fast passages"
Course to steer for crossing the channel
- Thread starter FairweatherDave
- Start date
Thank you for that!
Yes ... I think agreeing to disagree is the only solution on this forum: but it could be, to me at least, a fascinating discussion over a pint or two.
My toast: "Safe S-curves, and fast passages"
East Cardinal
Well-Known Member
“Cheers”
Ehecatl
Well-Known Member
When you get sight of land, look for a white tower set back a bit on a hill. That is pretty much opposite the East entrance through the outer breakwater
BelleSerene
Well-Known Member
Take care. You can lose your yacht navigating like that.
http://www.yachtingmonthly.com/sailing-skills/how-to-use-vector-charts-safely-33747
BelleSerene
Well-Known Member
No. By following a pre-determined 'nav track' (by which you mean over the ground, blissfully unaware of how the water is going to move over it), the only way you’re 'determining where your vessel is' is by looking at your GPS. Any fool who finds himself aboard a boat can do that. And he can then set his CoG vector to a rhum line and end up in Cherbourg by constantly varying his course to offset the seemingly random tide. The whole point is that the fool does it by 'plotting a historic position'; a navigator predicted that position and got it right. It’s not rocket science.
There was a time when great seamanship was required in the Navy. Now it seems many navigating officers aren’t worthy of dayskipper skill. High boatspeed and the redundancy of sail are fair reasons, or excuses at least - but perhaps if a navigator has to cling to a ground track in order to end up where he wants, something has gone badly wrong?!
Tranona
Well-Known Member
I assume this is either a joke or you are being deliberately obtuse.
You really seem to have no understanding of navigating a small yacht safely.
It is NOT the same as navigating a big ship. The objective is to recognise the forces that are having an effect on your boat over the duration of the passage and either using them to your advantage or minimising any negative impact. When you are sailing a boat at 5 or 6 knots, and are limited in your direction of travel, tide rates of 3 knots - common in channel waters - have a substantial impact on both your speed and/or your direction of travel. As these forces, particularly tide are predictable and measurable, it makes sense to plan in advance how they will affect you and then shape a course to steer to take best advantage in reaching your destination. The same principle applies whether you are going across tide as in this discussion or along the tidal flow as in coastal sailing.
If you bothered to do an RYA course covering navigation this will be the basis of all your learning because it is fundamental to efficient passage making under sail. As you have already discovered by doing the calculations on a 60 mile channel crossing following this method reduces the passage time by between 10-15%. The difference can be even starker on a passage going with or against the tide. For example a regular passage for me is Poole to Cowes. This can be achieved comfortably in a tide and with a free wind my boat will achieve 6 knots through the water. With the tide my average SOG is 7.5knots, and against is nearer 4 knots.
So, forget all your big ship and high speed power boat navigation strategies. With a sailing boat the objectives of navigation particularly with respect to tides are different as the resources available to you and the impact of external factors greater.
Dutch01527
Well-Known Member
I have read and understood the thread. I was trying to contribute to the debate with a view of how the Merchant Navy professionals would approach the problem. You might not agree with the approach but it is standard practice developed over many years. Plot a course and stick to it. Might be a bit less efficient but safer than trying to plot the variations of time, tide and leeway. Perhaps you should inform the Merchant Navy training colleges and examiners that you have a better way.
Tranona
Well-Known Member
Fine. But we are not navigating merchant ships.
Nobody is questioning how merchant and naval ships navigate - just pointing out that their methods are inappropriate for small, slow, wind propelled yachts.
Is it not unreasonable to recognise this?
prv
Well-Known Member
Sure. But nothing says that the predetermined track has to be a straight line over the ground.
Mine is drawn on the chart same as yours, it's just a different shape. I check every hour (actually often more frequently, but at least each hour) that I'm following it, and make corrections if not.
And I'll be in the pub an hour or two before you finish punching the Normandy tide.
Pete
DJE
Well-Known Member
I will check my old paper chart when I get home. But I seem to remember that the "Area to be Avoided" around the mid channel buoy was to keep the big ships appart betwwen the TSSs. Not sure that it applied to small craft.
East Cardinal
Well-Known Member
And there you have it!
Making corrections to follow a predetermined track. You are not therefore keeping a constant heading and allowing tidal drift to produce your S curve. So you cannot have it both ways.
I have actually done RYA theory courses (Coastal Yachtmaster and Ocean Nav)
I will leave it there.
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East Cardinal
Well-Known Member
No need for that.
It may be good but I don’t think the RYA day skipper is equivalent to RN ( FNO or PWO(N) ).
Uricanejack
Well-Known Member
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Uricanejack
Well-Known Member
NealB
Well-Known Member
That is very surprising (I mean that literally: it is most definitely not meant in any sarcastic way)!
When I did the Yachtmaster Theory, back in 1987, we spent a lot of time doing various cross Channel passage plans. It was drilled into us that the S-curve is quicker, no less safe, and therefore more seamanlike, than staying on the straight line over the ground.
I was taught, incidentally, by a retired RN Commander who was in strong demand as an ocean racing navigator.
I've checked, just now, a few of my navigation text books.
The first four I opened, all have excellent explanations of what we're calling the S-curve approach. They are by some highly regarded people:
- Sir Robin Knox Johnston (ex MN Navigating Officer)
- Captain John Illingworth (RN Officer, and crack racing skipper in his day)
- Eric Hiscock (pioneer ocean cruising yachtsman)
- Bob Bond (ex RAF Navigator, ex RYA Cruising Coach)
You have said nothing, other than dogma and discipline, to justify your shout of "rubbish" to Tranona.
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Angele
Well-Known Member
Not in the middle of the English Channel you can't.
dom
Well-Known Member
Not to forget Brittany Ferries, especially when slow steaming, and in that vein Carnival Corporation, Moller Maersk.....
Sensing a spot of trolling here mind
Angele
Well-Known Member
Yes. I think it was meant to be a mini-roundabout, giving shipping going into Southampton or Portsmouth a good point at which to "peel off". But I don't recall reading anything that said it didn't apply to certain classes of vessel.
KellysEye
Well-Known Member
Rules for a channel crossing Article 10 are here: https://www.gov.uk/government/upload...65/msn1781.pdf
prv
Well-Known Member
If I do the sums right (mostly, the visual interpolation between the speeds and locations given in the stream atlas, rather than actual sums), I don't need to make any corrections. This doesn't always happen, but it's not uncommon either. I am keeping a constant heading - either literally to the degree if my plan was perfect and I didn't need to touch the autopilot, or broadly constant with one or two small corrections during the passage because the tide's stronger or weaker than my planning assumed. Certainly not constant corrections to react to the changing tide. And absolutely I am allowing tidal drift to produce the curve - where else would it come from?
Pete
