Tide question

[DavidBolger]

Is it better to sail directly against the tide (or directly with it) rather than to have the tide on the beam? Assume that there is no wind against tide waves to battle against.

Scenario
Sailing up the coast and I am beating against a tide but with no waves to mention. The tide will slack in one hour and I have two tacks of 1 hour each to go. Do I sail directly into the tide for 1 hour and then tack when the tide goes slack OR do I sail with the tide on my beam for 1 hour and then tack when the tide goes slack.

I hope I am making my question clear.

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[Guest]

Probably best way to answer is to draw the various triangles and see what result is ......

My thought is that the tide will still in whichever direction you travel in given time deflect you x from your destination ... but the triangles will give better answer ...

<hr width=100% size=1>Nigel ... and of course Yahoo groups :
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[DavidBolger]

But will the tide act stronger or weaker depending upon the aspect of the boat it is faced with. ie beam on or directly into it?

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[Talbot]

wont make any difference to the end result (draw it out if you dont believe me)

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[[3889]]

No - the boat sits on the water like a bottle on a supermarket conveyor belt - the direction it faces does not affect the speed of the conveyor. However, if you can lee bow the tide, ie get it to act on your leeward side, you will be pushed up to windward enabling you to sail much higher than normal which will allow you to reach your desination more directly. It is worth pinching up to achieve this affect in any reasonable strength of tide.
Andy

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[Birdseye]

It depends on the speed of the tide.

Assuming you do mean that there is no tide for the second hour, and measuring "better" as being greater progress in the direction you want to travel, then better progress is made by heading direct into the tide provided that the speed of the tide is greater than twice the speed of the boat. If the tide speed is less than twice the boat speed then it is better to sail the first hour with the wind on the beam.



<hr width=100% size=1>this post is a personal opinion, and you should not base your actions on it.

 

[Guest]

tiadl drift does not care about aspect of the object in it ----- ie your boat. 2 miles drift in 1 hour is 2 mile in 1 hour whatever way you look at it.


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[l'escargot]

Surely that only applies if you drift and don't put power, in this case sails, into the occasion. I am thinking of the "ferry glide" principle. If you go beam on you will lose ground, if you angle into the flow you can hold ground or even progress.

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[Guest]

The only way to know is ...

to draw the current vector and see waht happens with various angles to the current.

My drift comment was basically that whatever you do - the current will still try to drift you in a direction and rate whatever you do. So you counter with engine or sails ... but current is still trying ... and net effect in the end is the vector triangle.


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[Dominic]

A subtle tactical point

If I understood the scenario correctly.......... (and I am not sure that I did).

I agree with you but for one point.

The assumption is that the tide is running at the same speed close into shore as it is far out from the sure. In reality it can run at different rates close in to shore compared with far out. (Never mind the back eddy).

One may choose to stay in the weaker stream for the first tack and thus do better.

However, this usually depends on vast local knowledge or extreme cunning.

The rest of us trust to luck and bluff.


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[Talbot]

Re: A subtle tactical point

yes, obviously if the track takes you through two different currents, such that if you stay on one course you have the effects for a full hour, whereas on the other you move into the area of the other current earlier (or later), then there will be a difference.

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[Dominic]

Just being a little pedantic ...

...for which I apologise.

But in certain areas there can be very strong differences in the strength and even direction of the current as one moves away from the shore.

BUT despite that I totally agree with your earlier comment.

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[DanTribe]

One effect that may influence the choice, is wind strength.
Sailing across the tide will produce a lower APPARENT wind strength than heading directly into it. This is often an important factor in light conditions.

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[AlexL]

isn't this why the lee bow effect works? because of the 'tide wind' effect on the apparent wind - efectively giving you a lift?

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[peterb]

I'm sorry, I don't quite get the picture.

Near the coast the tide is constrained to run parallel to the shore. If you are sailing for roughly equal times against the tide and across the tide, then surely you must be averaging 45 degrees to the shore, and not just sailing up the coast?

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[BobE]

Assuming the tide is at 180 deg to the wind, i.e. opposing it. I would have thought you will sail with the tide pushing you against the wind so that you have a stronger wind and thus travel faster ( Lee bow effect)..Unless by sailing free you can get far enough to windward in the first time period to lay the mark. If you are trying to go dead to windward when the tide becomes foul ie running in the same direction as the true wind the apparent wind will decrease, boat speed will fall, and unless you have made enough distance to windward to allow you to lee bow the foul tide when "laying the mark"( and that's a bit pie in the sky) You'll just have to bite the bullet.. Pinching in a foul tide ain't any good unless you can get it onto the lee bow.. Though the seas should flatten out and help the boat speed...
Or am I talking garbage ? It is I admit difficult to get ones mind round....Now if you expect a wind shift it's much simpler belt off into the expected shift and lay the mark when it comes..
Iess it's all because we are playing about at the interface of two fluids...
And the problem or attraction of sailing is, as the boffin said " there are too many variables in the game to calculate the end result" or whatever..
Cheers Bob E..


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[kingfisher]

Sail INTO the tide.

The tide creates an apparent wind, equal in strength, but opposite in direction to the tide.

Simple: when adrift in a 4 knot tide, on a windles day, you will feel a 4 knot wind over the deck from a direction opposite of the tidal stream..

With the wind on the beam, sailing into the tide: there will be an extra wind vector coming from the rear, thereby increasing the apparent wind, and more importantly, inproving the wind angle.

Sailing beam on to the tide will have exactly the opposite effect.

As said: draw it out in vectors.

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