Course to steer at a given speed. - 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 > Skills and Seamanship > Learning to Sail
 Not a Member? 


Like Tree3Likes
Reply
 
LinkBack Thread Tools
  #11  
Old 12-06-2012
jackdale's Avatar
Senior Member
 
Join Date: Dec 2008
Location: Calgary, AB, Canada
Posts: 8,833
Thanks: 26
Thanked 36 Times in 33 Posts
Rep Power: 6
jackdale will become famous soon enough
Re: Course to steer at a given speed.

Quote:
Originally Posted by jrd22 View Post
Sailing isn't straight line, or constant speed. Your course will vary based on wind direction, speed through the water, etc so while your question is a good mental exercise it's not a practical application for sailing. In other words, line up the bearing line on your chartplotter with your destination and do your best to get there as soon as possible:-))
It is a fairly standard part of coastal navigation courses.

Your use of a bearing line will result in a curved course.

A example is crossing Georgia Strait from Vancouver to Silva Bay. On a strong ebb if you wish to minimize the time on course you will have to point further north than the bearing found on your chartplotter. If you simply use the bearing and maintain it you will up down by Thrasher Rock.

Of course, this is predicated on the ability to point.
__________________
__________________
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203, 204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)
Reply With Quote Share with Facebook
  #12  
Old 12-06-2012
jrd22's Avatar
Courtney the Dancer
 
Join Date: Nov 2000
Location: San Juan Islands., WA, USA
Posts: 3,816
Thanks: 3
Thanked 14 Times in 14 Posts
Rep Power: 14
jrd22 will become famous soon enough
Re: Course to steer at a given speed.

sv+ jack- note the smiley at the end? Tongue in cheek response to the OP's question about a straight line solution to his question. I too have been getting where I'm going for 40 years. Here in the PNW it's not uncommon to be crabbing 40-50 degrees one way and then the other a few minutes later while trying to maintain a course.
__________________
John
SV Laurie Anne

1988 Brewer 40 Pilothouse

Reply With Quote Share with Facebook
  #13  
Old 12-06-2012
jrd22's Avatar
Courtney the Dancer
 
Join Date: Nov 2000
Location: San Juan Islands., WA, USA
Posts: 3,816
Thanks: 3
Thanked 14 Times in 14 Posts
Rep Power: 14
jrd22 will become famous soon enough
Re: Course to steer at a given speed.

Actually, if you use the bearing line on your chartplotter and change your heading to compensate for leeway, current, etc in order to keep the line on the destination you will travel a straight course to the destination. In your example Jack, if the current is ebbing in Georgia in order for the bearing line to be pointed at Silva B you will have to be pointing further and further N as you get into the main current and then less as you get out of the current as you approach destination. The bearing line gives you your direction traveled over the ground so it adjusts your heading if you keep the line on the destination. I do it all the time crossing Rosario in the power boat and end up with an arrow straight line regardless of the varying currents.
__________________
John
SV Laurie Anne

1988 Brewer 40 Pilothouse

Reply With Quote Share with Facebook
  #14  
Old 12-06-2012
chucklesR's Avatar
Senior Member
 
Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Posts: 5,977
Thanks: 10
Thanked 30 Times in 30 Posts
Rep Power: 9
chucklesR is a jewel in the rough chucklesR is a jewel in the rough chucklesR is a jewel in the rough
Re: Course to steer at a given speed.

Jack, JRD etc..

Quote:
Of course, this is predicated on the ability to point.
Or of course, not to point (so well).
I add 3-5 degrees of lee way as an assumption when I'm laying base course lines.

Absolutely correct - but, assuming the OP doesn't have a chartplotter and a autopilot to follow it, the exercise is a good one - to determine an approximate course to get one near his destination.

That curved course line looks a lot more like a snake every time I look at my wake.
__________________
Lessons learned are opportunities earned.
Reply With Quote Share with Facebook
  #15  
Old 12-06-2012
Junior Member
 
Join Date: Oct 2011
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
seanpatrick is on a distinguished road
Re: Course to steer at a given speed.

First, I'd like to say thanks for all of the responses. You guys have really given insight to someone who doesn't spend much (if any) time on the water. (Marine nav. is just a hobby of mine.)

Second, a big thanks to svHyLyte. Your explanation of Polars is exactly what I was missing.


Quote:
Originally Posted by svHyLyte View Post
In terms of your question seeking a specific time of arrival...
Sorry, I should've clarified this part a bit. It was a problem about keeping a schedule that got me thinking, but my question here was not ultimately about that. It was mainly about staying on course with a variable speed, such as in a sailboat. And as I said, you have resolved that problem for me.

Thanks, again!
-Sean
Reply With Quote Share with Facebook
  #16  
Old 12-06-2012
jackdale's Avatar
Senior Member
 
Join Date: Dec 2008
Location: Calgary, AB, Canada
Posts: 8,833
Thanks: 26
Thanked 36 Times in 33 Posts
Rep Power: 6
jackdale will become famous soon enough
Re: Course to steer at a given speed.

One way to do the calculations

https://www.youtube.com/watch?v=7ahoGVGA1do
chucklesR likes this.
__________________
__________________
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203, 204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)
Reply With Quote Share with Facebook
  #17  
Old 12-07-2012
chucklesR's Avatar
Senior Member
 
Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Posts: 5,977
Thanks: 10
Thanked 30 Times in 30 Posts
Rep Power: 9
chucklesR is a jewel in the rough chucklesR is a jewel in the rough chucklesR is a jewel in the rough
Re: Course to steer at a given speed.

Quote:
Originally Posted by jackdale View Post
One way to do the calculations

https://www.youtube.com/watch?v=7ahoGVGA1do
he said the magic word 'leeway'

What he didn't say was "oops, I can't steer that high, so I fell off 3 degrees, then had to tack 3 miles to starboard' because the on shore wind shifted.

jackdale likes this.
__________________
Lessons learned are opportunities earned.
Reply With Quote Share with Facebook
  #18  
Old 12-07-2012
jackdale's Avatar
Senior Member
 
Join Date: Dec 2008
Location: Calgary, AB, Canada
Posts: 8,833
Thanks: 26
Thanked 36 Times in 33 Posts
Rep Power: 6
jackdale will become famous soon enough
Re: Course to steer at a given speed.

Quote:
Originally Posted by chucklesR View Post
he said the magic word 'leeway'

What he didn't say was "oops, I can't steer that high, so I fell off 3 degrees, then had to tack 3 miles to starboard' because the on shore wind shifted.

Actually it can work the other way. In 2007 Van Isle 360, when we were coming back from about 55 miles offshore, we got this great lift that took us to within about three miles of the leg finish. Then the wind died - offshore breeze competing with the prevailing westerlies.
__________________
__________________
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203, 204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)
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
Bum Steer - rudder gland question skipgundlach Gear & Maintenance 1 03-09-2012 10:46 PM
Windvane self steer CRN1857 Gear & Maintenance 8 08-04-2010 01:02 PM
Why does boat steer to hard starboard? funsailthekeys Gear & Maintenance 14 09-08-2008 01:50 AM
Steer with rudder or outboard? eMKay Learning to Sail 19 06-05-2008 07:33 PM
How to Steer in Waves Carol Cronin Racing Articles 0 06-10-2002 08:00 PM


All times are GMT -4. The time now is 02:17 PM.

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.