Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 17-11-2013, 04:02   #61
Registered User

Join Date: Aug 2013
Posts: 164
Quote:
Originally Posted by noelex 77 View Post
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?
__________________

__________________
Tantalus is offline   Reply With Quote
Old 17-11-2013, 04:15   #62
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: 10,619
Re: terminology ........ whats your flavour ???

Quote:
Originally Posted by Tantalus View Post
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.
Attached Thumbnails
Click image for larger version

Name:	image.jpg
Views:	77
Size:	33.5 KB
ID:	70589  
__________________

__________________
noelex 77 is offline   Reply With Quote
Old 17-11-2013, 04:26   #63
Registered User

Join Date: Aug 2013
Posts: 164
Quote:
Originally Posted by noelex 77 View Post

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?
__________________
Tantalus is offline   Reply With Quote
Old 17-11-2013, 04:35   #64
cruiser

Join Date: Dec 2012
Location: Seattle
Posts: 1,130
Re: terminology ........ whats your flavour ???

Quote:
Originally Posted by Tantalus View Post
How is the wind different on a boat on the water than it is on land?
It's wetter.
__________________
Jammer Six is offline   Reply With Quote
Old 17-11-2013, 04:44   #65
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 6,715
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.
__________________
StuM is offline   Reply With Quote
Old 17-11-2013, 07:42   #66
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: 10,619
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.
__________________
noelex 77 is offline   Reply With Quote
Old 17-11-2013, 08:06   #67
Registered User
 
OldFrog75's Avatar

Join Date: Feb 2013
Location: Santa Monica, CA
Boat: Club Sailor; various
Posts: 922
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?
__________________
OldFrog75 is offline   Reply With Quote
Old 17-11-2013, 08:13   #68
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: 19,764
Quote:
Originally Posted by OldFrog75
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.
__________________
"Parce que je suis heureux en mer, et peut-Ítre pour sauver mon ame. . . "
Dockhead is online now   Reply With Quote
Old 17-11-2013, 08:40   #69
Registered User
 
Sailing Cowboy's Avatar

Join Date: Apr 2011
Location: Home Port: West Palm Beach, Live: Seattle
Boat: Beneteau Oceanis 473
Posts: 315
Re: terminology ........ whats your flavour ???

Quote:
Originally Posted by Dockhead View Post
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.
__________________
Sailing Cowboy is offline   Reply With Quote
Old 17-11-2013, 09:20   #70
Registered User
 
cwyckham's Avatar

Join Date: Apr 2011
Location: Vancouver, BC
Boat: Niagara 35
Posts: 1,870
Re: terminology ........ whats your flavour ???

Quote:
Originally Posted by Dockhead View Post
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
__________________
cwyckham is offline   Reply With Quote
Old 17-11-2013, 09:44   #71
Marine Service Provider
 
Maine Sail's Avatar

Join Date: Jan 2007
Location: Maine
Boat: CS-36T - Cupecoy
Posts: 3,061
Re: terminology ........ whats your flavour ???

I need to find myself a good looking boat wench. I do prefer them horizontal though..
__________________
Marine How To Articles
Maine Sail is offline   Reply With Quote
Old 17-11-2013, 10:19   #72
Senior Cruiser
 
FSMike's Avatar

Cruisers Forum Supporter

Join Date: Aug 2009
Location: Bahamas/Florida
Boat: Solaris Sunstar 36' catamaran
Posts: 2,654
Images: 5
Re: terminology ........ whats your flavour ???

Quote:
Originally Posted by Dockhead View Post
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).
__________________
Sail Fast Live Slow
FSMike is offline   Reply With Quote
Old 17-11-2013, 10:38   #73
Registered User
 
Capt Phil's Avatar

Join Date: Jun 2010
Location: Stateline NV
Boat: Prior boats: Transpac 49; DeFever 54
Posts: 2,749
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
__________________
Capt Phil is offline   Reply With Quote
Old 17-11-2013, 11:07   #74
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: 19,764
Re: terminology ........ whats your flavour ???

Quote:
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.
__________________
Dockhead is online now   Reply With Quote
Old 17-11-2013, 11:32   #75
Registered User
 
Hoofsmit's Avatar

Join Date: Jul 2013
Location: cornwall uk
Posts: 569
Quote:
Originally Posted by Jammer Six View Post
It's wetter.

I love this
__________________

__________________
Hoofsmit 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 08:00.


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.