Terminology ........ Whats your Flavour?

[Dockhead]

Originally Posted by Tantalus

It just occurred to me that, while there have been several sources cited establishing true wind as being relative to ground or true north, there have been no citations of literature regarding the contrary view that true is based on "water wind". Any citations please?

Have a look at your wind instrument manual.

[Dockhead]

Originally Posted by StuM

For those who say "true wind" is water referenced: when a boat is making leeway (being physically pushed sideways through the water by the wind), is the "water based true wind" actually referenced to the water or is it referenced to the boat?

Excellent point - that will introduce an error.

[Tantalus]

Originally Posted by Dockhead

Have a look at your wind instrument manual.

Wouldn't that be kinda like reading the side of a box of Cocoa Puffs to find out what a balanced diet would be?

[noelex 77]

Originally Posted by Dockhead

As to options, I think the instrument makers have it right. Give us ground wind only in relation to a compass rose; useless and potentially confusing in relation to bow.true wind in relation to bow only water-referenced.

The problem is a lot of cruising boats have inaccurate logs. This means inaccurate true wind. The GPS always reads correctly no matter which tack you are on upwind or down.
Even those boats with accurate logs don't always stay like that during a trip, especially cruising weedy areas. It is not unusual in high growth non tidal areas like the Med for cruising boats to remove the log completely, or at least give up the ritual of cleaning it.

I don't want everyone to switch to ground wind, but it would be nice if the instrument makers at least gave us the option. All the data is available to the wind instruments. The calculations are very simple (and identical to true wind) all we need is a software option that allows SOG to substitute STW (for ground wind off the bow)

The instrument makers know best? Bah! Humbug!

[Hoofsmit]

Originally Posted by Tantalus

Wouldn't that be kinda like reading the side of a box of Cocoa Puffs to find out what a balanced diet would be?

I like this

[Wotname]

Originally Posted by Jim Cate

And then there are those perennial favorites:

"Knots per hour" and "Amps per hour"

Gag reflex is engaged.

Jim

Just came into this thread late - but...

Jim, what is wrong with "Amps per hour"; how would you define say an electrical source that had a capacity 10 Ampere hours if not as 10 Amps per hour (or say 1 Amp per 10 hours etc). ...
Unless you are taking objection to saying "Amps per hour" in lieu of "Ampere hours" - in which case, I also would have the gag reflex engaged.

[StuM]

An ampere is a flow rate (electrons per second). Same concept as gallons per hour for a water maker or bilge pump or engine. "amperes per hour" is like saying "gallons per hour per hour".

[goboatingnow]

Originally Posted by larryklaas

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.

The movement rate and direction of the tide is called the set and drift , current is not tide , though one can talk of tidal currents


Dave

[goboatingnow]

Originally Posted by noelex 77

If there is little difference (I see you point, but don't quite agree. The thirty percent windspeed difference in my example indicates this) then ground wind is more preferable as the GPS derived speed tends to more accurate (on a cruising boat) than log based speed which is subject fouling.

Small speed differences can have a significant effect on true/ ground based wind calculations (especially the angle).

Rather than ground based wind as the default it is only possible to use true wind on most wind instruments. Which is historically based, but is silly in this day and age. Instrument makers should at least give us the option. Even those that prefer true could switch to ground wind if the paddlewheel becomes fouled.

BTW. For accurate polar generation true wind rather than ground wind is needed. Ground wind is irrelevant as far as the sails are concerned.

Ground wind is not " irrelevant " as far as sails go. It's the primarily motive power. Water referenced wind is used in polar to remove the effect of current generated winds , so as to produce a symmetrical polar not influenced by tide. But it's a mathematical abstraction , you can only experience true ( land wind ) md apparent wind. You can never experience water referenced wind

Dave

[goboatingnow]

Originally Posted by noelex 77

Well we have some great experts on CF. So I will cite Dockhead who explained it very well:

I suppose you want an outside reference. So with a quick google search I came up with:
(I still think Dockheads explanation is better)

True Wind

Dockheads description way be clear bit it is errorenous. A reading of for example Bowditch 1917 edition will clearly show that mariners regarded true wind on board as land wing or forecast wind.

On fact Beaufort, developed his f1 to f 12 by way of the set of the sails of ships of the line. So that sailors could relate the wind they experience to forcasted winds.

True wind as mariners use it now is a instrument maker concoction. And despite what Dockhead says. There are only TWO winds that matter. Ground wind and apparent wind. These are real and exist. water referenced wind is a mathematical vector construction

Remember when a boat is stopped in the water you are still feeling apparent wind. ( by its very definition ) all wind on a boat is apparent wind, there's is nothing else really there.


Dave

[goboatingnow]

Originally Posted by Jammer Six

If you say so.

If you call "mayday", you will be answered by the U.S. Coast Guard, which is one of five military organizations.

Why do you think military SOP has no place in marine communications, since a lot of marine communication IS military?

I notice you've been asked for a citation, and I'll add my request to that list: please its your source.

I am a licensed CEPT VHF instructor and candidates this side of the pond sit a comphrensive exam on marine VHF operating procedure and the GMDSS

I have yet to meet a US sailor that understand how to properly use a VHF radio in all circumstances nor has any clue about GMDSS ( which the US has implemented )

I suggest a read of this

http://sail-lbs.com/wp-content/uploa...1906435202.pdf

Would be in order for all ex colonials lol.

You will notice that " break " is not a recognised proword, this is specifically because it breaks the requirements of listening before transmitting

Dave

[goboatingnow]

Originally Posted by Jammer Six

If you say so.

If you call "mayday", you will be answered by the U.S. Coast Guard, which is one of five military organizations.

Why do you think military SOP has no place in marine communications, since a lot of marine communication IS military?

I notice you've been asked for a citation, and I'll add my request to that list: please its your source.

See my citation post , not to mention I am a registered certified CEPT marine VHF instructor.

Dave

[goboatingnow]

Originally Posted by SV Sea Monkey

Don't tell the Navy.

Military is not the best example of VHF usage. I saw a most flagrant violation of VHF procedures by a US military vessel anchored in Cartehena bay in Spain, to the absolute consternation of the Spanish coastguard.
( they did a VHF ch 16 alert excercise that involved actually broadcasting voice alerts on ch 16 )

Dave

[goboatingnow]

Originally Posted by Dockhead

I agree with both of you. I think Dave meant that no one bothered to think much about the distinction so long as there was no accurate way to measure.

As to options, I think the instrument makers have it right. Give us ground wind only in relation to a compass rose; useless and potentially confusing in relation to bow.true wind in relation to bow only water-referenced.

True wind on a boat should be land wind. Or the actual true wind a d that's what instrument makers should compute. What's provided ie water referenced winds , outside of polars is actually useless. The vast majority use the " true wind" to relate the wind to the forecast. Which means they should be using ground computed wind . How many people press the button and write the " true wind " into the log. What they really mean is the true wind ground referenced.

Dave

[StuM]

> this is specifically because it breaks the requirements

Care to tell us all exactly where this is specified as the reason for it's non inclusion.


Edit: Your one reference jusr doesn't mention it. I provided three references earlier which do specifically give it as a proword:

ACP 125(F), Communication Instructions Radiotelephone Procedure
ICAO Manual of Radio Telephony and
UNDP Guide to Radio Procedures for Emergency Responders