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Old 17-11-2013, 03:02   #61
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Perhaps the most important thing is to understand what your instruments display. Most sailors think when they switch their instruments over to "true wind" they are getting a reading of what the wind would be on land. This is not the case (if there is any current). If you are not sure turn off your GPS you will find your true wind speed and heading remain unchanged. This means the instrument is not displaying a ground referenced wind, it is displaying water referenced wind. The wind display does not indicate what would be happening on land.

I get the impression most people want to use "true wind" to mean what is correctly defined as "ground wind". I do have some sympathy for this view the terms are misleading and out of step with our use of terminology elsewhere.

However, apart from changing the nomenclature that sailors use we have the the problem what do we call the "other" wind. We need three names to distinguish the three types of wind.

Apparent wind
True wind
Some other term?

We also need to re-label all our wind instruments replacing "true wind" with the "some other term" if we are going use "some other term" to describe water based wind.
It's not just that people "want" to use that terminology, it's that it is the historical, and most accurate, terminology. Sailors have been using various means of calculating true wind for an awfully long time, and doing it fairly accurately using rather simple tools. From that perspective it is the more recent use of "ground wind" to reference what had always been "true wind" which causes the confusion. What is water referenced wind, and why would it be called true?
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Old 17-11-2013, 03:15   #62
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Re: terminology ........ whats your flavour ???

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It's not just that people "want" to use that terminology, What is water referenced wind, and why would it be called true?
Water referenced wind is what your wind instruments will display when you switch them on to "true wind".
This is not the same direction and velocity as wind is felt on shore.

The instrument below is not displaying the wind on shore it is displaying the wind with respect to the water. This is called "true wind" by sailors (hence the dot indicating it is displaying true wind) but you want to call something else. I am still not sure what.
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Old 17-11-2013, 03:26   #63
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Water referenced wind is what your wind instruments will display when you switch them on to "true wind".
This is not the same direction and velocity as wind is felt on shore.

The instrument below is not displaying the wind on shore it is displaying the wind with respect to the water. This is called "true wind" by sailors (hence the dot indicating it is displaying true wind) but you want to call something else. I am still not sure what.
How is the wind different on a boat on the water than it is on land?
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Old 17-11-2013, 03:35   #64
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Re: terminology ........ whats your flavour ???

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How is the wind different on a boat on the water than it is on land?
It's wetter.
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Old 17-11-2013, 03:44   #65
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Re: terminology ........ whats your flavour ???

> This is called "true wind" by sailors

This used to be called "true wind" by sailors because it was the best approximation they could get to "true wind".

It is still calculated and called this by some instrument makers. Others do actually calculate and display "true wind" because with the advent of GPS giving accurate COG/SOG it is now possible to do so.
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Old 17-11-2013, 06:42   #66
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Re: terminology ........ whats your flavour ???

Let's take a very simple example just looking at windspeed and ignoring a direction calculation problem problem.

The wind on land is a steady 10 knots from the North.
Our boat speed is 5 knots towards the north (we are motoring directly into wind)
There is a three knot current running from North to south.
What will our wind instruments read?

Apparent wind will read 10+5-3=12 knots
True wind will read. 12-5=7 knots.
Note our wind instruments do not read the wind with reference to the ground when switched to "true wind" the wind instrument on shore would read 10 knots our instruments on the boat would read 7 knots.

If our instruments could read ground wind (and very few can) it would read 12-SOG.
SOG is 2 knots therefore ground wind is 10 knots

It is important to realise that both true wind and ground wind provide information to the sailor.
The racing sailor will use his velocity prediction program to have a target boat speed to aim for. Even though it is actually blowing (on land) 10knots the correct true windspeed on the boat is 7 knots, so this is the figure that should be put into velocity prediction program.

On the other hand sailor that wants to decide if the windspeed has reached its forecast maximum of 10 knots will want to know that the ground wind has now reached 10knots even though the true wind is only 7 knots.

It is a pity that most instrument packages will not display ground wind.
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Old 17-11-2013, 07:06   #67
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Re: terminology ........ whats your flavour ???

Many boats have a wench like contraption mounted on the bow to help raise an anchor. Most people refer to this as a windlass but since they are generally mounted vertically rather than horizontally isn't it technically a capstan?
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Old 17-11-2013, 07:13   #68
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Many boats have a wench like contraption mounted on the bow to help raise an anchor. Most people refer to this as a windlass but since they are generally mounted vertically rather than horizontally isn't it technically a capstan?
The wench-like contraption on the bow hauling up the anchor is technically referred to as a Boat Girl. While Boat Girls can be very useful in the horizontal position, they are exclusively found in the vertical position when hauling up anchors. Capstans and windlasses are completely different. They were invented for sailors who don't have Boat Girls, which are much more versatile.
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Old 17-11-2013, 07:40   #69
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Re: terminology ........ whats your flavour ???

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The wench-like contraption on the bow hauling up the anchor is technically referred to as a Boat Girl. While Boat Girls can be very useful in the horizontal position, they are exclusively found in the vertical position when hauling up anchors. Capstans and windlasses are completely different. They were invented for sailors who don't have Boat Girls, which are much more versatile.
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Old 17-11-2013, 08:20   #70
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Re: terminology ........ whats your flavour ???

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The wench-like contraption on the bow hauling up the anchor is technically referred to as a Boat Girl. While Boat Girls can be very useful in the horizontal position, they are exclusively found in the vertical position when hauling up anchors. Capstans and windlasses are completely different. They were invented for sailors who don't have Boat Girls, which are much more versatile.
Post of the week! LOL
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Old 17-11-2013, 08:44   #71
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Re: terminology ........ whats your flavour ???

I need to find myself a good looking boat wench. I do prefer them horizontal though..
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Old 17-11-2013, 09:19   #72
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Re: terminology ........ whats your flavour ???

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The wench-like contraption on the bow hauling up the anchor is technically referred to as a Boat Girl. While Boat Girls can be very useful in the horizontal position, they are exclusively found in the vertical position when hauling up anchors. Capstans and windlasses are completely different. They were invented for sailors who don't have Boat Girls, which are much more versatile.
Post of the week indeed!
I feel I should point out that Boat Girls tend to have higher maintenance requirements than windlasses (or capstans).
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Old 17-11-2013, 09:38   #73
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Re: terminology ........ whats your flavour ???

Never worried much about 'true wind, apparent wind' or whatever. On deliveries, the only thing that mattered was DMG. That was where the money was made... less time over the bottom, more $ in my pocket. Get there fast with no breakdowns and arrive with as many as you left with. Not a difficult formula... Phil
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Old 17-11-2013, 10:07   #74
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Re: terminology ........ whats your flavour ???

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Originally Posted by noelex 77 View Post
It is important to realise that both true wind and ground wind provide information to the sailor.
The racing sailor will use his velocity prediction program to have a target boat speed to aim for. Even though it is actually blowing (on land) 10knots the correct true windspeed on the boat is 7 knots, so this is the figure that should be put into velocity prediction program.

On the other hand sailor that wants to decide if the windspeed has reached its forecast maximum of 10 knots will want to know that the ground wind has now reached 10knots even though the true wind is only 7 knots.

It is a pity that most instrument packages will not display ground wind.
I agree, at least for people sailing in tidal waters. When I installed new electronics last winter, I installed a Maretron DSM250 which has a weather screen showing ground wind speed and direction, among other things. The wind direction is shown on a compass rose, referenced to the compass, rather than to your bow as our instruments show True and Apparent.

It has been incredibly useful. If you are doing chart work and want to know where you can sail, you see it instantly. You instantly see how the weather is changing, discriminating that from changes in True Wind resulting from tide changes. When you wake up in the morning, you can look at it and immediately see what the wind is doing, so that you know whether that passage you had planned is going to be ok or not.

For people in non-tidal waters, it is less useful, because with no current, True Wind = Ground Wind, both speed and direction. The problem for those people would be that our instruments don't show True Wind referenced to the compass, although I think my B&G Tritons could be set up to do that if I would update the firmware.
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Old 17-11-2013, 10:32   #75
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It's wetter.

I love this
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