Early season passage planning poser

N

NFCN

Well-Known Member
Joined
4 Sep 2006
Messages
197
Location
France
Visit site
Cherbourg, to arrive in time for the market this Sat, leaving Gosport at 1800 in a well equipped Moody 33...

I just wondered if anyone with time on their hands might look at the forecasts (which seem to vary from a W to SSW F3 to 5) and the tides (coming off springs, easterly set in the later part of the passage) and comment whether:

- you'll be thrashing to windward all the way chum and you'll be set too far east - it's Honfleur for you

- fantastic close reach all the way - you'll make the eastern entrance

- wish I was there - you'll cruise in and smell the baguettes at about 0700...
 
I think you've said it yourself - just too much variation in the forecast to be able to tell at this range - it seems likely that there will be just too much S in the wind to fetch into Cherbourg - it's certainly time you checked up on "lee bowing" - it could make all the difference /forums/images/graemlins/smile.gif
 
Many times done similar trip, i always used to calculate tides etc and spent many an hour planning passage. Have to admit last 2 times I've pointed at Cherbourge and sailed to the compass and you tend to be near enough so any alterations can be made a few hours out. As to wind keep your fingers crossed its not on the nose the whole way ( done that as well ). For this cracking advice, bring us back a bottle of cheap plonk /forums/images/graemlins/laugh.gif
 
looks like a west 4-5 over friday night so a nice sail dependant on sea state. If you can leave a few hours earlier from GoSport the tide will benifit you better round the back of the island. Forcast looks okay at this early stage in the week best look again nearer departure time.

If you can get in and out okay i would prefer st V for the saturday market rather than cherb. Looks like cherb have some new pontoons for visitors acording to may YM. have a good one
 
[ QUOTE ]
wish I was there - you'll cruise in and smell the baguettes at about 0700...

[/ QUOTE ]Nick, (assuming BST) depart Bridge at 20:30 and steer 187.5 Mag at 5.7 kn gets you to Cherbourg (West entrance) at 06:58. Alternatively depart Bembridge Ledge at 19:30, steer 204.7 Mag at 5.5 kn gets you there at 07:22.
Of course, if it's SW instead of W then it'll be a different story and the baguettes will be stale.
 
Thanks Danny - thought you might pop up and use your excellent software to give me a steer, as it were. It looks as if it is all down to the westerly quotient in the wind. St Vaast will be easier but, alas, the lock gate doesn't open until lunchtime - in which case (unless anyone knows better) we'll be having a British fry up while anchored (reasonably sheltered I suspect), then getting our heads down until it is time to come in for a very long lunch...

Nick
 
My reading of the runes would suggest a WSW 15-18 kts. Personally I would transit through the needles and then a nice reach across.
 
Hey bedouin. "Lee bowing" will not make any difference. Sure the distance will look shorter on the chart but will not make you cross the channel any quicker or help you point upwind any more.
 
Are you sure mixmaster? The latter part of the passage is going to be during the easterly set, taking me downwind, and not helping at all - whereas if the tide was running westwards, towards the wind, I would get a real lift to windward. Like many sailors I've lee bowed many times before to good effect...

The seas may be flatter, with wind over tide, but if I'm trying to go to windward the tide can be a real help...
 
I'm with NFCN on this. There's a mental trick that's sometimes useful when thinking about these problems. Your boat floats on the water and, unless under way, moves with the current. So - instead of thinking of the current flowing in a certain direction - think of the land moving in the opposite direction! That way you can imagine your boat's course as a straight line through the water (assuming a constant heading) and your planned landfall as a moving target! It works for me.

Imagine a SSW wind and a Westerly set: Cherbourg effectively moves to the East so maybe you can make it on one tack. Now imagine an Easterly set: Cherbourg "moves" upwind to the West and now it's on the nose all the way.

(This 'trick' becomes less accurate as the current flow increases or the wind speed decreases - because the flow of the current then makes a significant difference to the wind direction and strength)
 
Yes I'm sure. If you were tacking you would tack as dictated by wind shifts and not whether the tide was ebbing or flooding at that particular time.
Now as a prudent navigator I would always err to being a bit upstream of my destination (regardless of wind direction in most cases).
The tide may be in your favour towards the end but against you at the beginning. First principles really, calculate the net tide vector and then course to steer. If tacking then, work the wind shifts not which direction the tide is at the moment (which will not change to surprise you).

Now having said that, if tacking I would prefer to be on the tack that is "lee bowing" given the current tide set and therefore giving me a ground track that does not stray too far east or west but that's only in case of a dramatic windshift against me.

Strictly mathematically speaking. With wind on the nose and not shifting it would not matter what tack you are on given the set of the tide.
 
Agreed. All the current really does is help or hinder your passage to your destination. If you're unlucky it may prevent you from sailing directly to a given point which you could otherwise have fetched. If you have to tack anyway, and the current remains constant, then there is no advantage in one tack or the other. There is certainly no added advantage in pinching up to put the current on the "lee bow" when sailing close hauled against the current.
 
The point is that crossing the channel you will normally experience approximately two complete tides. Under those circumstances choosing how to combine tacks with the tides can make the difference of a couple of hours to the passage time.
 
[ QUOTE ]
The point is that crossing the channel you will normally experience approximately two complete tides. Under those circumstances choosing how to combine tacks with the tides can make the difference of a couple of hours to the passage time.

[/ QUOTE ]Well, if you cross from the Solent to Cherbourg at around 5kn you'll only experience approximately ONE complete tide (abt 12 Hrs). Whether you need to tack or not will affect the passage time (and therefore the best 'average heading' calculation) but, after that's been calculated, it makes little difference which tack you are on during each half of the tidal cycle. Of course, it makes a big difference to the ground track and you might want to make sure you approach the destination on a particular tack or cross the traffic on the most perpendicular tack.
 
Bedouin you're wrong. Under the circumstances you describe, the state of tide vs what tack you're on will make no difference.
 
Oh dear - not again.

If you are crossing the channel into the wind the choice of how to combine tack with tide has a huge impact - if you don't believe me then just do the maths.

If you take the example of 3 kn tide crossing a 10 kn wind the difference in heading close hauled on the two tacks is about 30 degrees.
 
Yeh - gotcha! I apologise, Bedouin. I misunderstood your point entirely. What you're saying is that, assuming the tidal flow (or current, or whatever) changes direction then that can produce a useable wind shift at some time during the passage? I agree - and I think it's the same point I was trying to make around midday yesterday (doesn't time fly when you're enjoying yourself).

Problem is we got diverted onto a discussion on "lee bowing" which I for one think of as something somewhat different and which is being chewed to death in another thread.
 
[ QUOTE ]
Bedouin you're wrong. Under the circumstances you describe, the state of tide vs what tack you're on will make no difference.

[/ QUOTE ]Mixmaster, I think Bedouin's making the same point as you made earlier...[ QUOTE ]
If you were tacking you would tack as dictated by wind shifts and not whether the tide was ebbing or flooding at that particular time.

[/ QUOTE ]...The incontrovertible (wow!) point being that change in tidal flow produces a shift in apparent wind.
 
That's it - that is generally known as "lee bowing the tide". Although obvious people don't realise just what a difference it can make, crossing the channel in an F2-3 lee-bowing rather than the opposite can knock hours of the passage time.
 
You must log in or register to reply here.

Share this page

Top