True Wind Speed and Direction - Page 2 - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #11  
Old 11-28-2008
.
 
Join Date: Nov 2006
Posts: 10,851
Thanks: 0
Thanked 4 Times in 2 Posts
Rep Power: 12
Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice
Jim,

the ST60 is NOT to be used to tell you where, as in which magnetic direction, the wind is coming from..it's used to tell you, in relatiion to your bow, where is the true/apparent wind and how strong they are...

It's a sail realted instrument, not a navigation instrument.
Reply With Quote Share with Facebook
  #12  
Old 11-28-2008
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 11 Times in 11 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
Just be aware that it will only give you an approximate true wind and direction. The reason I say this is that the ST60 wind instruments, like those of most brands, will use the boat's speed through the water (STW) for the calculation, and the speed through the water may or may not be accurate, since the speed transducer can be affected by things like current. It would far more accurate for the wind instrument to use GPS derived SOG and heading.

For instance:

Say the boat is sailing a course of 0˚ at 10 knots, and the true wind is 10 knots at from the east @ 90˚. If there is no current affecting the knotmeter—the knotmeter shows a speed of 10 knots, and the apparent wind will be 14.14 knots at 45˚. The wind speed indicator will calculate a true wind of 10 knots @ 90˚—which is the true wind speed in this case.

However, if the boat is moving at 10 knots with a heading of 0˚, with a five knot northerly current—the knot meter will only show a speed of FIVE knots. The boat is still moving at 10 knots SPEED OVER GROUND, the apparent wind will still be 14.1 knots at 45˚... but will calculate the true wind to be 11.14 knots at 63.5˚, which is wrong.
__________________
Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Share with Facebook
  #13  
Old 11-28-2008
Nearly an Old Salt
 
Join Date: Oct 2008
Posts: 263
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 6
goboatingnow is on a distinguished road
I'm not aware of any instrument sets that use SOG to calulate true wind. is anyone?
Reply With Quote Share with Facebook
  #14  
Old 11-28-2008
Senior Member
 
Join Date: Jun 2007
Posts: 2,710
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 9
SEMIJim will become famous soon enough SEMIJim will become famous soon enough
SD, thanks for the caution, but I understand the effect of current and the difference between hull speed and speed over ground. In the places we'd use the device, current would be mostly a non-issue, because there's not much current, if any. Most times our speed log and GPS SOG agree with one another to within one or two tenths of a knot, if not right on. (Other than when we're under motor in rivers or canals, where there are currents.)

Jim
Reply With Quote Share with Facebook
  #15  
Old 11-28-2008
Senior Member
 
Join Date: Sep 2006
Posts: 2,216
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 9
Rockter will become famous soon enough
I wonder how it copes with leeway? If I am side-slipping, how does it know? I trust it makes an allowance for that too?

The boat never really sails the way it is heading. It could be compensated for, I suppose.
Reply With Quote Share with Facebook
  #16  
Old 11-28-2008
Senior Member
 
Join Date: Apr 2008
Posts: 476
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
negrini is on a distinguished road
Send a message via AIM to negrini Send a message via Yahoo to negrini Send a message via Skype™ to negrini
This subject piss me off .....

Jim,

we had this discussion some time ago ( I fully disagree to Raymarine ..... ). And still in the same position. Raymarine requires the wrong SOW information (Speed Over Water provided by that damm dirty paddle that goes into log inst.) to calculate TRUE wind. This is an aberration from an engineering stand point, as the only info rasonably accurate for TRUE (any true) calculation is SOG (Speed Over Ground) which any ordinary GPS can provide with far good accuracy. Although Raymarine agree with that, they insist in to use SOW, instead. OK, they could use both (precedence to SOG of course), but seems this is the only way to force users to BUY the damm log. I still love Raymarine technology, but every time I go through this I get pissed !!!!
__________________
Nave Rara
Beneteau Oceanis 43
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #17  
Old 11-28-2008
Senior Member
 
Join Date: Aug 2006
Location: wherever
Posts: 5,262
Thanks: 8
Thanked 17 Times in 16 Posts
Rep Power: 11
xort has a spectacular aura about xort has a spectacular aura about xort has a spectacular aura about
I'm unclear; can the ray st be used with gps only or not?
Reply With Quote Share with Facebook
  #18  
Old 11-28-2008
.
 
Join Date: Nov 2006
Posts: 10,851
Thanks: 0
Thanked 4 Times in 2 Posts
Rep Power: 12
Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice Giulietta is just really nice
look guys..I don't think I understand why this is deacying like this..there is even a guy with a blood clog about to burst over this...

It is nothing more than a sailing aid...NOT a navigational instrument...

It's better than nothing....it is what it is..I've been using them for decades....

never had any issues...

besides..I use tell tales and the windex...both are apparent wind indicators...

True wind is to prove if the BFS merda de boi is true or not...

Who the hell sails on true anyway???
Reply With Quote Share with Facebook
  #19  
Old 11-28-2008
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 11 Times in 11 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
Nope... doesn't account for leeway at all. If your boat is side slipping that much, you're probably doing something wrong.
Quote:
Originally Posted by Rockter View Post
I wonder how it copes with leeway? If I am side-slipping, how does it know? I trust it makes an allowance for that too?

The boat never really sails the way it is heading. It could be compensated for, I suppose.
__________________
Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Share with Facebook
  #20  
Old 11-28-2008
Senior Member
 
Join Date: Apr 2008
Posts: 476
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
negrini is on a distinguished road
Send a message via AIM to negrini Send a message via Yahoo to negrini Send a message via Skype™ to negrini
Giu,

I'm don't know if you take merda de boi at any price. Despite refusing daily offers, here, we try like hell don't pay for it! It is the principle/concept behind, not the fact itself. 'Cmon .... we're not discussing if boating is essential to living or not ....

Xort, No, it doesn't work !! If you have Raymarine, the only way to display the "almost true" wind is to install the ST speed.
__________________
Nave Rara
Beneteau Oceanis 43
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wind Orientation Mark Matthews Learning to Sail Articles 0 03-06-2005 07:00 PM
Understanding Apparent Wind Steve Colgate Learning to Sail Articles 0 11-10-2002 07:00 PM
Understanding Apparent Wind Steve Colgate Seamanship Articles 0 11-10-2002 07:00 PM
Understanding Apparent Wind Steve Colgate Racing Articles 0 11-10-2002 07:00 PM
Wind Michael Carr Seamanship Articles 0 08-31-1997 08:00 PM


All times are GMT -4. The time now is 11:57 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.