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Old 17-11-2013, 11:52   #76
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Originally Posted by Dockhead View Post
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.
Oh oh oh

I want one

Can I have one for chrimbo

Please
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Old 17-11-2013, 11:55   #77
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Re: terminology ........ whats your flavour ???

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Originally Posted by Maine Sail View Post
I need to find myself a good looking boat wench. I do prefer them horizontal though..
Look how much fun we had due to my spelling mistake. Good ones all around.
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Old 17-11-2013, 13:51   #78
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Re: terminology ........ whats your flavour ???

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Originally Posted by StuM View Post
That said, the current usage is as a unit of speed - specifically one nautical mile per hour (as recognised by ISO).

Knots per hour is not a speed, it is a rate of acceleration.

1 knot per hour is about 0,000014g
This from a group that uses commas to mark the end of the decimal portion and periods to mark the end of a sentence. Not very consistent, as compared to using both for phrasing, huh?

0.000014 g

How ISO resolves this is political doublespeak, typical of a standards organization.; they wimp out and create a standard method no one wants.
  • ISO 31-0 (after Amendment 2) specifies that "the decimal sign is either the comma on the line or the point on the line". This follows resolution 10
    of the 22nd CGPM, 2003; there is a brief reference to the history of this in [1]
    .
  • Numbers consisting of long sequences of digits can be made more readable by separating them into groups, preferably groups of three, separated by a small space. For this reason, ISO 31-0 specifies that such groups of digits should never be separated by a comma or point, as these are reserved for use as the decimal sign.
I started a thread some time ago on whether terms such as "broad reach" referred to true" or apparent wind because I had noticed variable usage; it went in circles with no one authoritative source identified. The mathematical concepts of relationships between alternate frames of reference are simple, but the nomenclature is inconstant between writers. Context generally makes it clear.
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Old 17-11-2013, 14:26   #79
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Re: terminology ........ whats your flavour ???

About the term "Break"...

In the Marines we were taught that "break" had one function: to save the radio by not burning out the transmitter with a lengthy sit-rep or other discourse. Say "break" and unkey the radio for a moment. The "break" only needed when comms became lengthy/detailed. For us, "break" meant: I pause but will continue.

A good time to "break" was when the intended recipient would change - a convenient usage today so as to draw attention to a coming change.

But when giving instructions to different recipients radio procedures would dictate identifying the second unit anyway, "break" or no "break"! "Squad Alpha go North; Squad Bravo go NNW", for example.

Of course, those were times long gone by - Forty-something years! - and radios are tougher now. {Remember tubes? } Then again, maybe we were taught that way really so as to give those Navy folk a chance to jump into the chatter! IE: "Negative Negative, you idiot jarheads! Fast movers are enroute to drop napalm to your bleedin' north!" Oh.... Never mind..... "Squads Alpha Bravo belay my last..."

Darn I'm getting old.
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Old 17-11-2013, 14:59   #80
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Re: terminology ........ whats your flavour ???

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Originally Posted by Hoofsmit View Post
Taking the risk of being called a limey or pomme ( or what ever else you care to call an English man)

It would appear that there is an Atlantic divide , The ASA teach one thing the RYA another......... CF another

I suppose it does not matter as long as the captain and crew/ navigator agree on your ship.

But when discusing the finer points of tidal currents in a forum we need to have continuity

I propose ( seconder and quorum needed) ( and I am not going to be the chairman) that this thread is used as a reference to what is understood by CF members, we can even have acronyms ( requested by some of our honourable members)
this question is really a moot one. wind is constantly moving direction. so what, if it is ground or water based. wind is N.S.W.E. or somewhere in between. never found this to be confusing
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Old 17-11-2013, 15:12   #81
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Re: terminology ........ whats your flavour ???

< so what, if it is ground or water based. wind is N.S.W.E. or somewhere in between. never found this to be confusing

Yep, to the traditionalists who say "true wind" is water based because that used to be the only way to measure it: Does it really make a difference when at that time, the limit of accuracy was something like "Force 4 from Nor-Nor-West by North"?
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Old 17-11-2013, 15:16   #82
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Funny, from my Army days, we wee told to "break" transmissions on the theory that it made it harder for the bad guys to direction find and therefore be able to triangulate your position
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Old 17-11-2013, 15:46   #83
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Originally Posted by thinwater View Post
This from a group that uses commas to mark the end of the decimal portion and periods to mark the end of a sentence. Not very consistent, as compared to using both for phrasing, huh? 0.000014 g How ISO resolves this is political doublespeak, typical of a standards organization.; they wimp out and create a standard method no one wants.[*]ISO 31-0 (after Amendment 2) specifies that "the decimal sign is either the comma on the line or the point on the line". This follows resolution 10 of the 22nd CGPM, 2003; there is a brief reference to the history of this in [1] .[*]Numbers consisting of long sequences of digits can be made more readable by separating them into groups, preferably groups of three, separated by a small space. For this reason, ISO 31-0 specifies that such groups of digits should never be separated by a comma or point, as these are reserved for use as the decimal sign. I started a thread some time ago on whether terms such as "broad reach" referred to true" or apparent wind because I had noticed variable usage; it went in circles with no one authoritative source identified. The mathematical concepts of relationships between alternate frames of reference are simple, but the nomenclature is inconstant between writers. Context generally makes it clear.
Point taken
I am approaching another thread with alternate points of reference as a starting point, totally capsizing it actually if it works.
Unfortunately I'm dyslexic , which means I have to read and rewrite then edit so slowly that the thread has lost my last point. The great thing is that this allows me as with most of this condition ,to put a understood theory into practice a lot quicker than some.
Converting a practical ability into a understandable theory is not so easy.
So I am discredited from the offing !
But you are correct
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Old 17-11-2013, 18:22   #84
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Re: terminology ........ whats your flavour ???

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Originally Posted by svmariane View Post
About the term "Break"...

In the Marines we were taught that "break" had one function: to save the radio by not burning out the transmitter with a lengthy sit-rep or other discourse. Say "break" and unkey the radio for a moment. The "break" only needed when comms became lengthy/detailed. For us, "break" meant: I pause but will continue. [...]
And I was taught that we said "break" in the middle of a long transmission so anybody with emergency traffic could cut in. This would be especially true on VHF #16, the emergency and calling channel.

Of course I don't remember where I was taught this, but it was probably as a ham operator, or when I was was studying for my First Class Phone license (this ticket no longer exists). It could be completely wrong, but it sure makes sense.
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Old 17-11-2013, 19:41   #85
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Re: terminology ........ whats your flavour ???

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And I was taught that we said "break" in the middle of a long transmission so anybody with emergency traffic could cut in. This would be especially true on VHF #16, the emergency and calling channel.

Of course I don't remember where I was taught this, but it was probably as a ham operator, or when I was was studying for my First Class Phone license (this ticket no longer exists). It could be completely wrong, but it sure makes sense.
And we know that nobody hangs there on VHF 16 while yacking away... Talk of pet peeves! That really gets up my left nostril.


Anyway - it might make sense to insert a break in longish radio transmissions for (insert reason), and I've no qualms about that.

But consider: Even if Operator Longwind just keeps chatting away, anybody else can still broadcast an emergency on the same freq and Operator Goodguy would (probably?) hear the overlapping talk. And might even respond to the emergency call while Longwind chatters along. Not clean or elegant, but maybe do-able. I can't be the only one who's heard dueling conversations over a radio freq.

And for the other post re: Army and keeping xmissions short to confound being DF'd.... Point taken.
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Old 17-11-2013, 19:59   #86
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Re: terminology ........ whats your flavour ???

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[...]
But consider: Even if Operator Longwind just keeps chatting away, anybody else can still broadcast an emergency on the same freq and Operator Goodguy would (probably?) hear the overlapping talk. And might even respond to the emergency call while Longwind chatters along. Not clean or elegant, but maybe do-able. I can't be the only one who's heard dueling conversations over a radio freq.

And for the other post re: Army and keeping xmissions short to confound being DF'd.... Point taken.
Yes, "break" only makes sense for a long transmission. Due to the "capture effect" a powerful FM signal (such as the Coast Guard's) might completely cover up a weaker signal from someone trying to break in. This is less of an issue with AM or sideband (such as aviation VHF or marine SSB) where you will still hear a much weaker signal, but with FM the blocking effect can be absolute.
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Old 19-11-2013, 06:17   #87
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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.
Correct it's display a mathematical vector that's of little use to anyone outside of boat polar generation. In practice as has been done for centuries , such a measurement is approximated to the land TRUE Wind . Ie the sailor compares the reading with the expected forecast wind ( a very common usage of such info ) ignoring the small errors typically induced by current.

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Old 19-11-2013, 06:19   #88
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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.
It's may be so in military communications , but it has no place in marine VHF parlance

Dave
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Old 19-11-2013, 10:52   #89
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Re: terminology ........ whats your flavour ???

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Originally Posted by goboatingnow View Post
It's may be so in military communications , but it has no place in marine VHF parlance

Dave
Why do you say that? Please explain your reasoning (or source)...
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Old 19-11-2013, 11:56   #90
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Re: terminology ........ whats your flavour ???

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hi all
in another thread we have found these terms to have different meanings to some

whats your take on it?


here is mine

i stand to be corrected


from the English dictionary
True
/tru/ Show Spelled [troo] Show IPA adjective, tru·er, tru·est, noun, adverb, verb, trued, tru·ing or true·ing.
adjective 1. being in accordance with the actual state or conditions; conforming to reality or fact; not false: a true story.




1.) true wind = un affected by any other factors

True wind is the angle measured clockwise through 360-degrees of the direction the wind is coming from relative to True North.


Apparent applies to that which can readily be seen or perceived:



2.) Apparent wind = what is perceived to be the wind direction at the helm position

Apparent Wind is the angle measured clockwise through 360-degrees of the direction the wind is coming from across the deck relative to the bow.

angle and velocity influenced by induced heading wind , leeway, current/ tidal stream and any thing else that affects what you feel .... including bean induced

3.) Tide =
a. when referenced to height or range it means one thing
b. when referenced to flow/current / stream it means velocity or direction

Tide is the vertical movement of water. The tide rises and falls. It does not come in or go out.

Current is the horizontal movement of water.

4.) Leeway = the affect on a vessel from wind induced side ways move ment
i think that's it for now
Leeway is the lateral slippage of a vessel caused by a variety of factors including press of sail, wave action, current, and/or "prop walk." It is expressed in degrees left or right of dead ahead.

May I suggest you consult an excellent reference: The Encyclopedia of Nautical Knowledge.
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