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    Posted: 02 Oct 17 at 9:59am
Originally posted by JimC


GRF is basically sound on sailing in tide, and what he calls lee bow effects are valid. They just aren't the dumb theory you'll find by that name in some old books and from some old sailors.

Really?

When he also says this:

Originally posted by iGRF

 if you can get the flow from the windward side to even head on, then it's worth the effort, if you can get it from nose on, to the lee side then you will see benefits, providing... Your forward motion isn't seriously compromised or your main driving foils (the sail)end up too head to wind to be effective.

I'd say the above is a dumb theory. 

Foils experience flow in the direction the boat is moving through the water, at the speed the boat is moving through the water. No matter what you do, no matter what tide, no matter what wind. 

Pinching will first stall your sails and then when you slow your foils will stall, and you will side slip. The foils will then experience a flow from the lee, because that will be the direction you are slipping too. No one wants to the slipping to leeward when going up wind. 




Edited by mozzy - 02 Oct 17 at 10:01am
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Posts: 370 		Post Options Post Options   Quote Old Timer Quote  Post ReplyReply Direct Link To This Post Posted: 02 Oct 17 at 9:55am
Originally posted by By The Lee

That just isn't true as the tide has no effect on your speed though the water only over the ground therefor imagine your boat is traveling at 3 knots through the water you will have exactly exactly the same amount of flow over your foils regardless of where the tide is on your bow. The problem with all these lee bow theories is they treat the boat as if it is tethered to the bed whereas in reality there is only one way the tide can take you and that is with the direction of current. There are only 3 gains to be made in tide: fixed objects(marks), change in tide across a course and the effect tide has on your apparent wind. The best analogy would be to imagine we are racing on a treadmill (not a prefect comparison as as you said tide is rarely the same across a course). The treadmill can only move you in one direction and it moves everybody at the same rate regardless of there heading.

Give up now ... he will never get it ... 
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Posts: 370 		Post Options Post Options   Quote Old Timer Quote  Post ReplyReply Direct Link To This Post Posted: 02 Oct 17 at 9:51am
Originally posted by JimC

The back story behind this is that in the dim past there used to be a dumb theory about sailing in adverse tide called the lee bow effect, which still persists in some quarters, but GRF has never come across. It was nonsense, ....

The above is exactly what he is referring to below ...  sadly he still believes ...

Originally posted by iGRF

I'm sorry, but just inching high enough to get an unfavourable tide onto the bow as against the weather side, can make a difference, 

Still deluded ....


Edited by Old Timer - 02 Oct 17 at 9:51am
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Posts: 3420 		Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 17 at 10:30pm
I can't remember who ? but an obscure science fiction writer once stated that heavier than air flight was only possible due to an as yet unidentified anti-gravity static charge generated by friction, inversely proportional to air density and specific area of surface, perhaps this is what lee bowing taps into. Wink

Edited by 423zero - 02 Oct 17 at 1:25pm
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Posts: 6499 		Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 17 at 10:17pm
You believe what you want to and I'll trust my experience. Dinghy sailors told me all the codswallop thirty five years ago, they are as wrong now as they were then. The tether you seek but fail to grasp is your rig. You are sailing between two fluids, suspended between them and the directions in which they are moving and the power you use to pursue your course over the ground is the sum of their efforts, you just need to dial into it and stop thinking two dimensionally.
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Posts: 114 		Post Options Post Options   Quote By The Lee Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 17 at 8:56pm
That just isn't true as the tide has no effect on your speed though the water only over the ground therefor imagine your boat is traveling at 3 knots through the water you will have exactly exactly the same amount of flow over your foils regardless of where the tide is on your bow. The problem with all these lee bow theories is they treat the boat as if it is tethered to the bed whereas in reality there is only one way the tide can take you and that is with the direction of current. There are only 3 gains to be made in tide: fixed objects(marks), change in tide across a course and the effect tide has on your apparent wind. The best analogy would be to imagine we are racing on a treadmill (not a prefect comparison as as you said tide is rarely the same across a course). The treadmill can only move you in one direction and it moves everybody at the same rate regardless of there heading.

Edited by By The Lee - 01 Oct 17 at 8:57pm
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Posts: 6499 		Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 17 at 8:45pm
Originally posted by By The Lee

To be fair everything iGRF said is true apart from the non sense apart pinching to get the tide on a favorable side of the bow...


OK, let's just requalify this, forget the boat, think about your foil, if you can get the flow from the windward side to even head on, then it's worth the effort, if you can get it from nose on, to the lee side then you will see benefits, providing... Your forward motion isn't seriously compromised or your main driving foils (the sail)end up too head to wind to be effective.

Now, some of these awful things you sail, have such sh*t foils of course it doesn't work, but just as gybing plates have an effect, so does skewing the tide off your weather side to head on, if it is at all possible, then you'll have an advantage over those that don't bother, the same as you will against those that don't 'hunt' lifts when they come along and just sail a bit faster.

I admit, all this is easier on a board than in a boat, but it can be done, I do it all the time, that girl Europe sailor showed me the skewing body technique we use on boards applied to a boat down the lake, and since I've dialled it I can get a similar stuffing the boat without stuffing the sail effect, I've seen lots of other good sailors doing it so it can't just be me.

Edited by iGRF - 01 Oct 17 at 8:49pm
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 17 at 7:05pm
I wouldn't call anything I explained in my previous post "lee bow effect" because of the other meanings which JimC alludes too (tacking on the lee bow to give dirty air and pinching up so the tide is on your lee bow rather than bow). 

What the tide does is change your apparent. If the tide is against the wind it increases your apparent, if its with the wind is decreases it. If it's cross the wind it changes the apparent wind direction. 

But critically, from a strategy point of view you can't make use of this knowledge unless things are changing. You can't make use of shifts if the wind isn't shifting and so you can't make use of the tide unless it changes too (over time or over the course). 

Which is just what I was pulling iGRF up on.You never stated how things were changing, so I didn't understand why he was saying 'go that way'. 

Strategy is simple, the question is always; is this tack better now, or later. If the answer is later, then tack. The difficult bit is knowing what will happen later, and iGRF didn't state that in any of his scenarios, so they made no sense. (i used to have a coach who said "always sail the tack which is reducing the distance to the windward quickest; the long tack rule. This is okay, but often not perfect, as there are often situations where you are on the favoured tack, but if it the tack is only going to get better still, then you should sail the unfavoured tack first. e.g. persistent shift). 

Interesting facts about tide:
1) When the tide is with you up a beat, you get a double benefit; not only will you get the VMG increase equal to the current, but you will also see an increase in wind speed which will give a boat speed increase (unless you're over powered), so the gain of sailing in more tide is amplified. 

2) If you're in a boat that has a VMG faster than the wind downwind, and it is wind against tide, you're better sailing against the stronger tide, as the increase in apparent wind strength will outweigh the current you're fighting against. And vice versa if the current is with you downwind.
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Posts: 114 		Post Options Post Options   Quote By The Lee Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 17 at 6:25pm
To be fair everything iGRF said is true apart from the non sense apart pinching to get the tide on a favorable side of the bow...
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Posts: 6499 		Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 01 Oct 17 at 1:53pm
I'm not sure of the question in point 1, and point 2, would be better served with a diagram, classic cross tide tends to be the scenario I'm describing, but tide can be 360 degrees, it can be coming from 0, 90, 180, 270 or 360 and obviously the effects will all be different.

Something I used to tell inland windsurfers that helped them in their reasoning, the wind we traditionally sail on is 2d apparent, the true wind and the created wind, tide is just a third element in the creation of the apparent wind sometimes it strengthens the true wind, some times it assists the created wind, or has the opposite effect and the key to using it is working out which it is.

Edited by iGRF - 01 Oct 17 at 1:58pm
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