Let's Get to the Bottom of the Lee-Bow Effect Once and For All

[Seaworthy Lass]

Originally Posted by foolishsailor

Im comfortable with the CTS discussion from the other thread. *But sailing upwind in steady current to a fixed point is not the same as sailing a single tack in the same current and calculating a CTS.

Well, what happens with a steady current? Do you think the "course" is either side of your rhumb line, or either side of your straight course through water?

Why would this definition of "course" suddenly alter if the current was variable? You still have a straight line to sail relative to the water.

[Seaworthy Lass]

Originally Posted by foolishsailor

Even if the current is a real world example like sailing across the Solent with a variable over time and distance current to a point dead upwind. You will not be calculating a CTS you will instead estimate the correct times to tack based on your estimates of magnitude and direction of current since sailing up wind requres the boat to be hard on the wind the whole time.

I would disagree with that at first glance (let me think on it to see if I change my mind). I would think with current varying over a long period of time you would tack every time the other tack became closer to your CTS. ie You follow whatever tack is closer to your CTS.

[foolishsailor]

Because a CTS is a Course to Steer - and you are not steering that course if it falls within your tacking angle and therefore it provides no benefit.

I can see how you could use the CTS as a center point if you wished to short tack up the CTS or almost like a CTE to let you know how far off you are when tacking...

...however it yields no benefit and can be very misleading, especially as on your last tack to lay your destination you will be nowhere near your CTS and if you are going dead upwind and have a tacking angle of 100°, depending on the magnitude of and direction of current you could be over 50° off your CTS.

I can CTS being used as an element in upwind strategy with current but not the same way it is used with a single tack course to lay a mark like discussed in the other thread..

For example see the drawing I just made,it is a real world example of a winning strategy that happened in Cowes Week this year in the quarter tonner class. An example of immense forethought and risk that in retrospect we all thought to ourselves - why didnt we do that? The currents are approximate but very close to the day based on my Winning Tides tidal planner for the Solent.

CTS played a role in two places - The winning boat choosing its CTS to cross sailing the least time and distance and the final Sailing angle to lay the mark the remaionder of the fleet choose - but more importantly would be calculating current relief and assist and where a change in tack will optimize this.

[foolishsailor]

Originally Posted by Hoofsmit

ok..... I see it as a course to steer....you are just doing another one when your vectors change.
but my opinion seems unworthy of comment to most

Not at all - but your comments I think are encompassed by the discussion at hand and I hope they are being addressed.

[I.Grind]

Originally Posted by Hoofsmit

ok..... I see it as a course to steer....you are just doing another one when your vectors change. but my opinion seems unworthy of comment to most

Sorry HS, took time out to sleep. I agree with your assessment of the situation. I also doubt this thread will ever come to a complete resolution unless standardized terminology is adopted for the purpose of this discussion. Rules of engagement. I think it has now evolved into factoring current into CTS anyways, as LBE has pretty much been discredited. If the comments were not so long and well thought out I might think this were simply an exercise in boosting post count.

[Seaworthy Lass]

Originally Posted by foolishsailor

Because a CTS is a Course to Steer - and you are not steering that course if it falls within your tacking angle and therefore it provides no benefit.

I can see how you could use the CTS as a center point if you wished to short tack up the CTS or almost like a CTE to let you know how far off you are when tacking...

Why would short tacks or long tacks make a difference in steady conditions? They just add up. If following short tacks works along the CTS, then following long tacks does as well .

Originally Posted by foolishsailor

...however it yields no benefit and can be very misleading, especially as on your last tack to lay your destination you will be nowhere near your CTS and if you are going dead upwind and have a tacking angle of 100°, depending on the magnitude of and direction of current you could be over 50° off your CTS.

Judging the last tack is an issue in any situation. Tacking along the CTS does not suddenly remove the need for that judgement.

Originally Posted by foolishsailor

I can CTS being used as an element in upwind strategy with current but not the same way it is used with a single tack course to lay a mark like discussed in the other thread..

Why not? You have just stated it would work for short tacks. Why on earth would you be using the rhumb line as your reference point?

Originally Posted by foolishsailor

For example see the drawing I just made,it is a real world example of a winning strategy that happened in Cowes Week this year in the quarter tonner class. An example of immense forethought and risk that in retrospect we all thought to ourselves - why didnt we do that? The currents are approximate but very close to the day based on my Winning Tides tidal planner for the Solent.

CTS played a role in two places - The winning boat choosing its CTS to cross sailing the least time and distance and the final Sailing angle to lay the mark - but more importantly would be calculating current relief and assist and where a change in tack will optimize this.

Will look at this later. Juggling chores and CF at the moment .

[foolishsailor]

I.Grind - I think you are right we have all moved past Lee Bow Effect I think??? I hope???

But we are now entering a new area that i think is beneficial to cruisers which is optimizing vectors upwind in adverse current. What Lee Bow Effect wishes it was

Angela,

See attached drawing. The dotted red lines are your laylines and your tacking angles. I am assuming a tacking angle of 90degrees.

If you calculated a CTS and short tacked the CTS line you would not be sailing an optimal course by a long shot as once you started entering the middle of the channel every port tack would be dead into the peak current.

A much faster route would be to sail on starboard tack the whole way across the channel until you reached near your layline and then tack so that now you are in lesser current for the entirety of your port tack .

[Hoofsmit]

Originally Posted by foolishsailor

Not at all - but your comments I think are encompassed by the discussion at hand and I hope they are being addressed.

very true they are (apart from the title of the thread.).... I am learning all the way

I tried to do a paste as you have done of the Fowey estuary where I raced but it would not load. we have more restrictions to beating up the side of a channel with small valleys creating wind veers the tidal eddies are also complex

your picture sums it perfectly .....

to me each leg is a course to steer for the next tack, meaning a course to steer has tidal vector etc etc worked in

so in affect we navigate in real time because the next cts is taken from a fix with a guess at the next wind or current change , we just try and do the maths in our head.!!!

From what I understand you are saying, you are doing the same just different way of putting it?

[Seaworthy Lass]

Originally Posted by Hoofsmit

ok..... I see it as a course to steer....you are just doing another one when your vectors change.
but my opinion seems unworthy of comment to most

Hoof, you are not being ignored. It is just that your questions are being answered as the thread is progressing.

Originally Posted by I.Grind

Sorry HS, took time out to sleep. I agree with your assessment of the situation. I also doubt this thread will ever come to a complete resolution unless standardized terminology is adopted for the purpose of this discussion. Rules of engagement. I think it has now evolved into factoring current into CTS anyways, as LBE has pretty much been discredited. If the comments were not so long and well thought out I might think this were simply an exercise in boosting post count.

Yes, we definitely need standardised terminology. That is vital.

Yes, this thread is evolving. It is not off topic though. The discussion is basically about management of current and since we have shown LBE does not exist, it is progressing to general management.

I certainly don't need my post count boosted. Just the opposite. I would prefer to have some shaved off so I don't look like a blabbermouth LOL.

[Hoofsmit]

Originally Posted by I.Grind

Sorry HS, took time out to sleep. I agree with your assessment of the situation. I also doubt this thread will ever come to a complete resolution unless standardized terminology is adopted for the purpose of this discussion. Rules of engagement. I think it has now evolved into factoring current into CTS anyways, as LBE has pretty much been discredited. If the comments were not so long and well thought out I might think this were simply an exercise in boosting post count.

thankyou very much....... perfect summary

but at least I have learnt a lot .... but there are so many views which are probably founded on experience in this thread ..... just the desire to use them as a proven rule drives it forward ... its not a bad thing

[Seaworthy Lass]

Originally Posted by foolishsailor

See attached drawing. The dotted red lines are your laylines and your tacking angles. I am assuming a tacking angle of 90degrees.

If you calculated a CTS and short tacked the CTS line you would not be sailing an optimal course by a long shot as once you started entering the middle of the channel every port tack would be dead into the peak current.

A much faster route would be to sail on starboard tack the whole way across the channel until you reached near your layline and then tack so that now you are in lesser current for the entirety of your port tack .

You would certainly not be short tacking up your CTS, as that is only effective if conditions are steady or changes cancel out exactly along the way. Here the current is changing and does not cancel out. I have never suggested trying to follow short tack along the CTS when tacking with variable conditions that do not cancel out along the way.

It does not change the issue that the "course" is either side of the CTS. In these situations you want to be on the side of the "course" that will be knocked later. No different I think to thinking about the rhumb line dividing the "course" when there is no current and the true wind is altering because of veering wind.

Give me some on on this. I will look at it after dinner, as this actually needs some consideration. This was the next step and not one I have thought about, although think I mentioned to Dockhead very early on, this is where I was eventually wanting to head.

Your example is a complex one. Really about the hardest. Variable current that does not cancel out, and worst still, increasing then decreasing. May have to skip my glass of wine tonight if I want to give it any serious consideration .

[Hoofsmit]

I think what is evolving is peoples mind set of getting from A to B.

A race with a strong tidal infleuence , is very different to a passage plan in the Med.

We haven't even looked at hull speed ( mixed PYS class)its entertaining watching a skiff racing against a 90 year old keel boat in the same race )
the mind boggles !!!!

[foolishsailor]

The example with the simple drawing is a common crossing situation anywhere as current is always greater in deeper water which is usually the middle and slower in shallower water, usually the edges.

Ahd even if it were the opposite such that the current was worst on the side than in the middle - you would still use this to your advantage and in the case of the drawing where you found the lightest current your would make tack there onto port and sail on to your layline before tacking back.

I look forward to your response - I am sure I will learn something from it and refine my own upwind strategy.

By the by, if something you poke holes in helps to put me on the Podium - I will write your name on a piece of paper, tape it to the trophy before the photos!

Have your glass of wine, my fingers are tired as well.

Cheers

[foolishsailor]

Originally Posted by Hoofsmit

I think what is evolving is peoples mind set of getting from A to B.

A race with a strong tidal infleuence , is very different to a passage plan in the Med.

Absolutely. Sailing with my wife and kids I am surely not going to short tack up either side of the Solent using my depthsounder to tell me when to tack away from shore and my SOG to tell me when to tack back in.

However it doesnt always have to be that dramatic and Cruisers can definitely benefit from understanding Angela's brilliant method of creating a running CTS for crossings and they can also benefit from understanding that not all tacks are created equal when going upwind in adverse current.

Wow, I havent posted this many times in one day in a very long time.

Time for a rest and to play with the kids.

Ill log back in later

[Hoofsmit]

Originally Posted by foolishsailor

I.Grind - I think you are right we have all moved past Lee Bow Effect I think??? I hope???

But we are now entering a new area that i think is beneficial to cruisers which is optimizing vectors upwind in adverse current. What Lee Bow Effect wishes it was

Angela,

See attached drawing. The dotted red lines are your laylines and your tacking angles. I am assuming a tacking angle of 90degrees.

If you calculated a CTS and short tacked the CTS line you would not be sailing an optimal course by a long shot as once you started entering the middle of the channel every port tack would be dead into the peak current.

A much faster route would be to sail on starboard tack the whole way across the channel until you reached near your layline and then tack so that now you are in lesser current for the entirety of your port tack .

depends.... if the centre of the stream is doing 4 kts and you have a boat speed of 2 knots you are better off short tacking in the 1 knot zone to the side you are on
But that will be affected by tidal height, you might have to much draft to even contemplate it ! the joys of being a tactician

then again .... if you are in a fast planning dinghy with low wetted area you might well risk heading into the middle a little more !


Seaworthy.... are you starting to see the change in mind set of the table cloth?

the tidal/ current vector is now longer than any other applied !!!!!!!