Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 20-11-2013, 00:09   #106
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,725
Quote:
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.
__________________

__________________
"Parce que je suis heureux en mer, et peut-Ítre pour sauver mon ame. . . "
Dockhead is offline   Reply With Quote
Old 20-11-2013, 00:10   #107
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,725
Quote:
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.
__________________

__________________
"Parce que je suis heureux en mer, et peut-Ítre pour sauver mon ame. . . "
Dockhead is offline   Reply With Quote
Old 20-11-2013, 00:41   #108
Registered User

Join Date: Aug 2013
Posts: 164
Quote:
Originally Posted by Dockhead View Post

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?
__________________
Tantalus is offline   Reply With Quote
Old 20-11-2013, 00:45   #109
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,618
Re: Terminology ........ Whats your Flavour?

Quote:
Originally Posted by Dockhead View Post
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!
__________________
noelex 77 is offline   Reply With Quote
Old 20-11-2013, 01:30   #110
Registered User
 
Hoofsmit's Avatar

Join Date: Jul 2013
Location: cornwall uk
Posts: 569
Quote:
Originally Posted by Tantalus View Post
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
__________________
Hoofsmit is offline   Reply With Quote
Old 20-11-2013, 03:21   #111
Certifiable Refitter/Senior Wannbe
 
Wotname's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: Van DeStat Super Dogger 31'
Posts: 7,327
Re: terminology ........ whats your flavour ???

Quote:
Originally Posted by Jim Cate View Post
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.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Old 20-11-2013, 03:45   #112
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 6,707
Re: Terminology ........ Whats your Flavour?

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".
__________________
StuM is offline   Reply With Quote
Old 20-11-2013, 03:49   #113
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Quote:
Originally Posted by larryklaas View Post

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
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 20-11-2013, 03:53   #114
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Quote:
Originally Posted by noelex 77 View Post

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
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 20-11-2013, 04:00   #115
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Quote:
Originally Posted by noelex 77 View Post

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
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 20-11-2013, 04:15   #116
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Quote:
Originally Posted by Jammer Six View Post

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
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 20-11-2013, 04:16   #117
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Quote:
Originally Posted by Jammer Six View Post

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
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 20-11-2013, 04:21   #118
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Quote:
Originally Posted by SV Sea Monkey View Post

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
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 20-11-2013, 04:23   #119
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Quote:
Originally Posted by Dockhead View Post

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
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 20-11-2013, 04:29   #120
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 6,707
Re: Terminology ........ Whats your Flavour?

> 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
__________________

__________________
StuM is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
The Coconut Thread forsailbyowner Provisioning: Food & Drink 80 23-10-2011 21:53
Rigging Terminology Question Matt sachs Deck hardware: Rigging, Sails & Hoisting 4 12-09-2011 20:48
Hull Design - Terminology and Pros / Cons arbitrarysailor Construction, Maintenance & Refit 8 01-08-2011 06:59
Terminology question BillKov Monohull Sailboats 17 27-06-2011 05:01



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 19:26.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.