Lee bowing

Lee-bowing does exist and is quite simple mathematics. Tell me which of these simple steps you disagree with and we can discuss it from there.

1) We sail in the apparent wind not the true wind.

2) The true wind is caused by atmospheric pressure differences and is relative to the surface of the Earth at any point. (I'm neglecting tiny differences due to friction against the moving sea at this point)

3) Tidal streams move the water relative to the ground (including the surface of it upon which we sail).

4) From that it is simple geometry to appreciate that the presence of a tidal stream affects the apparent wind felt by a boat for a given true wind. If the tide is on the lee bow, the apparent wind is lifted compared to the apparent wind without tide, therefore you can sail higher close-hauled.
 
Lee bow effect exists or not depending on how you percieve the vectors. And is often misunderstood.
It certainly makes a disproportionate difference when a small windshift moves the tide from the lee bow to the weather bow!
 
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Lee bow effect exists or not depending on how you percieve the vectors. And is often misunderstood.
It certainly makes a disproportionate difference when a small windshift moves the tide from the lee bow to the weather bow!

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No, that makes no difference at all. The angle does not change compared to what you would see if there was no tide.
 
All four of JCP's points are correct - but the point is that although the current alters the apparent wind it does so for all craft equally! Any differences in their individual apparent winds are due to their own motion relative to each other. In fact for the sake of simplicity one can forget the current altogether, reverse the current vector and add it to the true wind. All that this does is make everything relative to the water surface rather than the ground.

What (I believe) most people understand as lee bowing (and which is a mythical effect) is as follows: my destination lies directly up current and I am sailing close hauled. Due to leeway I know I'm going to slip to downwind of my destination. Ah ha! I decide to 'lee bow' by pinching up slightly to eliminate the leeway - the idea being that the loss in boat speed will be compensated by the fact that I won't have to tack to reach the destination.

Some people describe this by saying that the flow of the current, which now has an angle of incidence to the leeward side of the keel, pushes the vessel to windward. They call it lee bowing.

It's a load of round things! There is no "current incident to the leeward side of the keel". There is only the normal force generated by the boat's movement through the water.
 
If you are correct in what you claim most people are thinking, then I agree, they are wrong!
It all comes down to vectors being a difficult concept for many, compounded by vague definitions. we probably mostly agree about what's going on but are talking in circles.
Tide has an effect on your lee bow. Tide has an effect on your windward quarter come to that. There is therefore a 'lee bow effect', but it is often misunderstood, mis-represented and mixed up with poor visualisation of the heading/cog/tide equation. And of course tide, wind and boatspeed are not constants, they all vary with both time and position.
Its interesting to hear how others think about these things, some people seem to cling to odd concepts, but go quite quickly to the windward mark!
 
I'd never heard of that use of the term lee-bowing before, but certainly I agree you wouldn't gain from it. (Although I've occasionally done it when cruising when the crew looked disinclined to put down their tea and sandwiches for a tack.)

I've only ever understood lee-bowing to refer to using the cross-tide to effectively shorten the distance sailed, such as when crossing the English Channel.
 
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I've only ever understood lee-bowing to refer to using the cross-tide to effectively shorten the distance sailed, such as when crossing the English Channel.

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Lee Bowing applies to any leg sailed where the angle of water flow to wind allows you to sail in such a way that the water flow is coming from the lee side of the boat. The angle can be quite acute if your boat is capable of sailing close to the wind.

Where the angle is small a skipper who is aware of the situation can instigate the lee bow affect by luffing slightly - this changes the apparent wind angle and hopefully enables the skipper to sail more closely to the true wind.

Lee Bow affect cannot be felt when the wind and flow come from the same direction.

Lee Bow affect applies lots of different scenarios - a lot occur within the harbour!
 
This is getting bizarre. A thread starts about Lee Bowing the tide in the context of a channel crossing, then lots of people turn up and start talking about something completely different (something to do with dinghy racing as far as I can see) and then claim it does not exist.

Weird or what?
 
It didn't start in the context of a channel crossing - it referred to another thread which was talking about channel crossing - this one was vague enough to be about lee bowing in general ...

If you want any tips on how to go faster more efficiently then look at the racing fraternity - they've (well the ones at the front) usually got the best way to get from A-B the quickest - sometimes it involves a lot of grunt ... but a lot of the time it involves using a lot of grey matter - and those are the ones we are more interested in.

A sailing technique can be identified in just about any sailing boat - reference to dinghy racing is good as it all tends to happen a lot more quickly in a more confined space - so the affect is more apparent.

Anyone who believes the Lee Bow affect does not exist can please explain how I (with many others towards the front of the racing fleet) can point around 10 degrees higher than those behind - in the same patch of water & wind, in the same class of boat ... which I (and the others) put down purely to using the lee bow affect.
Detail: rounding a mark, the next buoy is to windward - with a starboard tack bias. Sailing hard on the wind on starboard the tide is right on the nose. With a little pinch the tide is now on the lee bow - and pushes us to windward, the change in apparent wind allows us to continue at around the same speed as before. Those behind don't do this and end up sailing closehauled but ~10 degrees lower. We end up at the next mark miles ahead.
 
Re: Lee bowing myth

The reason is that the blokes in front of the racing fleet usually point about 10degrees higher than anybody else and sail about half a knot quicker too is why they are in front of the racing fleet!
If the "lee bowing" is taking you to windward then, what was a little bit of pinching would become major pinching and you will go slower.
This posting is a complete re-run on the subject exactly as I encountered several times before and nobody has yet mentioned ferry- gliding ---oops I've gone and done it.!!!
 
Re: Lee bowing myth

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The reason is that the blokes in front of the racing fleet usually point about 10degrees higher than anybody else and sail about half a knot quicker too is why they are in front of the racing fleet!

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EH? What a crap response!
Why are they quicker?

Because they know how to trim properly and because they know how to make the most out of the elements that are affecting their boat ... ie wind AND water current - lee bowing being one of the major contributors.
 
Re: Lee bowing myth

You give no reasoning for your thinking .... it would be like me saying "Gravity doesn't exist" .... with nothing to backup that statement.

Btw - my Knickers are not in a twist ... unlike your (current) thinking ....
 
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The presumption of the lee-bow effect is that if you are sailing directly into
the current you can pinch slightly, putting the current on your leeward bow, and the current will push you
up to weather. This is obviously false because the only direction the current can move you is in the
direction it is going (the stick on the river).

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False - The aerofoil shape of the keel works in the same way as a glider wing - we all know that gliders gain LIFT from the air passing over the wing - without this they would just fall out of the sky.

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The fallacy here, though, is that the judgment of going toward the wind and being swept away are made
in reference to fixed objects such as the mark, an anchored boat, or land. In reality, both boats are being
affected equally by the current and the wind "sees" both boats in the same way. In other words, if you
were following the race in a motorboat and were in the ocean where you couldn't see any land for
reference, the boats would look identical on either tack, and in fact you would have no clue that there
even was current unless you knew from charts or perhaps from the surface condition of the water. Put
another way, if you're sailing on a boat with apparent wind strength and direction instruments, they'll
read the same on both tacks because the boat is affected in the same way by the current on either tacks
(the stick in the river again).


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Again - completely false - this guy is either on a massive windup or really is talking out of his arse!
 
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False - The aerofoil shape of the keel works in the same way as a glider wing - we all know that gliders gain LIFT from the air passing over the wing - without this they would just fall out of the sky.

[/ QUOTE ](Oh dear! I can't let this one pass) So, to follow your analogy, are you saying that if I fly my glider in a headwind I get more lift (due to the increased airflow over the aerofoil)? I don't. I just fly slower (with reference to the ground). My airspeed remains the same as does the lift.
 
In my far-off days of dinghy racing, lee-bowing referred to tacking, on a windward leg, just to leeward, and preferably just clear ahead of an opponent. This causes the windward boat to sail in the deflected air, and disturbed water, created by the leeward boat. The effect is dramatic. The windward boat sails lower and slower, falls off to leeward into the wind shadow of the aggressor and loses still further. Particularly useful in team racing. Water current has nothing to do with it.
Lee bowing the tide is different and, IMO, can only be usefully exploited if the tide vector alters during the passage.
 
I'll have one last attempt and then I'm out of here!

Forget about sails for a moment.
When a boat is in a current the boat moves freely with the current ie as far as the boat is concerned it is always in current-free water. If you anchor, the situation changes dramatically and by moving the tiller you can move the boat in the current because you are now attached to the riverbed over which the current is flowing.
Let go the anchor and you are back into the free situation. When you are sailing (beating) you are in the free situation and the only current is due to the forward motion of the boat. So where are you going to find the magic component which will lift you to windward if you can just manage to get your bows through the direction of the current??
This marginal situation is quite different from the bigger picture of using a tidal stream to advantage on a passage where one tack is clearly more advantageous than the other.
 
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