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Old 16-11-2013, 18:39   #46
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I'm too simple to deal with the fine print. To me, apparent wind is what I get when my boat is moving. True wind is what I get when my boat is not moving. Anything else is of no practical use to me, so I don't add more clutter to my brain. I don't see how we can establish a firm terminology when half of us can't spell. I'm thinking about starting a thread just for spelling. A windlass is a device to help you raise your anchor. Windless is when you're becalmed. When you talk about a bearing, it's cutless. When you talk about a sword, it's cutlass. When you have a small boat or tender for the big boat, it's a dinghy. If you have a dingy, you should clean it. Etc. ad infinitum.
Can you puta link to your spelling thread, I'm dyslexic , my spell checker does not work on here
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Old 16-11-2013, 18:39   #47
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Re: terminology ........ whats your flavour ???

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Too true. And how about the "bowsprint"?
That's the term for doing the running jump off the bow onto the dock and breaking your ankle.
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Old 16-11-2013, 19:08   #48
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Re: terminology ........ whats your flavour ???

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Originally Posted by goboatingnow View Post

which by the way noelex, virtually everyone can now determine ground wind
My B&G instruments will display ground wind, but most instrument systems will not.

Of course you can calculate ground wind using some simple maths and a calculator, but by the time you had done the calculation the wind will have changed

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Now you had a speed over the ground, so you CAN calculate TRUE wind
SOG is used to calculate ground wind STW is used to calculate true wind.

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you can feel true wind,
The wind you feel is apparent wind. The true wind speed and direction may be very different.
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Old 16-11-2013, 19:13   #49
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Re: terminology ........ whats your flavour ???

I was just reading through my copy of 1917 American Practical Naviagator and they were describing the fact that the Beaufort scale was developed by assigning particular sail wardrobes on naval ships. clearly nobody ever felt the need to talk about water referenced wind. You looked at your sails, used the table to reverse out the boats motion and that was true wind. i.e. the wind the forecaster was telling you about.


then along came all that STW computed wind , nonsense.

dave
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Old 16-11-2013, 19:28   #50
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Re: terminology ........ whats your flavour ???

There is a lot of confusion in this thread.

Let's assume we have a completely steady wind and some current. You have a typical Raymarine ST 60 wind system and switch it to display "true wind" that is exactly what it will display. The wind will not be same as the wind experienced on land, or on a buoy that is anchored near the boat.
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Old 16-11-2013, 20:29   #51
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Re: terminology ........ whats your flavour ???

Yeah but how can you measure true wind since the instrument introduces its own drag coefficients? True wind would just be apparent wind with high accuracy.

- physics minor
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Old 16-11-2013, 21:15   #52
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Re: terminology ........ whats your flavour ???

One of my peeves...

RPM's

It is not revolutions per minutes


It is RPM or revolutions per minute
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Old 16-11-2013, 21:38   #53
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Re: terminology ........ whats your flavour ???

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One of my peeves...

RPM's

It is not revolutions per minutes


It is RPM or revolutions per minute


R'sPM?
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Old 16-11-2013, 21:48   #54
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Re: terminology ........ whats your flavour ???

> RPM's

One of my pet peeves. Grocer's apostrophes
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Old 16-11-2013, 22:45   #55
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Re: terminology ........ whats your flavour ???

"Knot: one nautical mile per hour."

US Sailing, Basic Keelboat, (Portsmouth, RI: United States Sailing Association, 1998), 84.
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Old 16-11-2013, 22:57   #56
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Re: terminology ........ whats your flavour ???

1 Knot =

101.26859143 feet per minute
33.75619714 yards per minute
1.852 kilometers per hour
1.68780986 feet per second
1.15077945 statute miles per hour
0.51444444 meters per second
Nathanial Bowditch, LL.D. The American Practical Navigator, an Epitome of Navigation, (Bethesda, Maryland: National Imaging and Mapping Association, 2002), 349.

Now I want to see who argues with Bowditch.

The military taught me the same thing it taught StuM.

It's particularly useful when one section of your transmission addresses one station on the net and the next section addresses a different station. For instance, a company commander addressing first platoon with one sentence and second platoon with the next sentence.

Example:

"Alpha one, this is Alpha six. Move south. Break. Alpha two, move east. Out."

I've heard people using break to interrupt a conversation. They always sound to me like they learned to use coms playing EVE.
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Old 17-11-2013, 01:59   #57
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There is a lot of confusion in this thread.

Let's assume we have a completely steady wind and some current. You have a typical Raymarine ST 60 wind system and switch it to display "true wind" that is exactly what it will display. The wind will not be same as the wind experienced on land, or on a buoy that is anchored near the boat.
This may clear up some of the confusion...there again, maybe not. From the naval manual, based on Bowditch.

"Wind Conversion theory and operation is familiar to anyone knowledgeable in nautical science or with maneuvering boards. The meteorological or maritime convention is always used: Wind direction is the DIRECTION FROM WHICH THE WIND IS BLOWING. True Wind is the direction (in degrees T) and speed of the actual wind, regardless of whether there is a moving ship measuring it. Relative Wind (RW) is the direction and speed of the wind (measured with respect to the bow) relative to your ship's movement through the water. Apparent Wind (AW) is RW expressed in degrees true. "
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Old 17-11-2013, 03:03   #58
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Re: terminology ........ whats your flavour ???

In addition to Tantalus' quote from the naval manual, here's another which defines True Wind as what some call Ground Wind.

Establishing more truth in true winds

"Quality control of automated weather station (AWS) data at the World Ocean Circulation Experiment Surface Meteorological Data Center reveals that only 20% of studied vessels report all parameters necessary to compute a true wind. Required parameters include the ship's heading, course over the ground (COG), speed over the ground, wind vane zero reference, and wind speed and direction relative to the vessel."

and

"The true wind is defined herein as a vector wind with a speed referenced to the fixed Earth and a direction referenced to true north. These techniques are developed to improve the accuracy of true winds calculated by maritime automated weather systems (AWS). "
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Old 17-11-2013, 03:05   #59
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Re: terminology ........ whats your flavour ???

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Yeah but how can you measure true wind since the instrument introduces its own drag coefficients? True wind would just be apparent wind with high accuracy.

- physics minor
True wind is displayed by most mid level wind instruments at least relative to the bow. It just needs STW and apparent wind ( leeway is ignored unless the instruments are sophisticated ). Compass integration allows for an absolute true wind heading.

Ground wind can also easily be calculated in the same way integrating the GPS, but very few instruments will do this. Because of the the greater accuracy and consistency of SOG instead of STW I think it a better display on most cruising boats ( no errors from one tack to the other, or with a slightly fouled paddle wheel).

True, (or Ground) wind is very different from apparent wind they can be 180 degrees apart in certain circumstances and a very different magnitude.
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Old 17-11-2013, 03:31   #60
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Re: terminology ........ whats your flavour ???

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.
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