Velocity Predictions Polar Diagram - 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 > Seamanship & Navigation
 Not a Member? 

Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


Reply
 
LinkBack Thread Tools
  #1  
Old 07-14-2011
Member
 
Join Date: Jun 2011
Location: Vancouver Island
Posts: 35
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
CowbaySailor is on a distinguished road
Velocity Predictions Polar Diagram

Can anyone help me find a polar diagram for my C&C 25. I'm looking for the velocity predictions of boat speed vs true wind angle. Its time to learn to sail smarter !!!
Reply With Quote Quick reply to this message Share with Facebook
  #2  
Old 07-14-2011
pedcab's Avatar
Senior Member
 
Join Date: Dec 2008
Posts: 192
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
pedcab is on a distinguished road
Quote:
Originally Posted by CowbaySailor View Post
Can anyone help me find a polar diagram for my C&C 25. I'm looking for the velocity predictions of boat speed vs true wind angle. Its time to learn to sail smarter !!!
I'd say, trace your own! It would be a fine entertainment and you'd get to know your boat a lot better...
__________________
Pedro

Portugal


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message Share with Facebook
  #3  
Old 07-14-2011
Member
 
Join Date: Jun 2011
Location: Vancouver Island
Posts: 35
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
CowbaySailor is on a distinguished road
I have started to do that Pedro. That doesn't give me the best velocity made good (VMG) for my boat.
In your mind which is better. you sail into a puff and the apparent wind angle increases, do you chase the tell tails and heat up immediately or steer straight or bear off slightly ease the sails at the same time. When the boat comes up to speed then head up slightly at close-hauled sail trim ?
Reply With Quote Quick reply to this message Share with Facebook
  #4  
Old 07-15-2011
Senior Member
 
Join Date: Apr 2011
Posts: 218
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 4
MikeWhy is on a distinguished road
CB, did you get my earlier from before the server crash? Just draw horizontal lines tangent to each curve to find the upwind or downwind VMG. It works for any wind angle, but straight upwind VMG is most directly meaningful to your questions, and incidentally the simplest to find.
Reply With Quote Quick reply to this message Share with Facebook
  #5  
Old 07-15-2011
Member
 
Join Date: Jun 2011
Location: Vancouver Island
Posts: 35
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
CowbaySailor is on a distinguished road
I got a message saying you sent one but didn't receive it. Thanks for the info I will plot my collected readings.
Reply With Quote Quick reply to this message Share with Facebook
  #6  
Old 07-15-2011
jackdale's Avatar
Senior Member
 
Join Date: Dec 2008
Location: Calgary, AB, Canada
Posts: 8,966
Thanks: 27
Thanked 54 Times in 51 Posts
Rep Power: 7
jackdale will become famous soon enough
During the server crash, I send a message that US Sailing sells polars, but they are expensive.
__________________
__________________
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 Quick reply to this message Share with Facebook
  #7  
Old 07-15-2011
pdqaltair's Avatar
Senior Member
 
Join Date: Nov 2008
Location: Deale, MD
Posts: 2,285
Thanks: 1
Thanked 36 Times in 36 Posts
Rep Power: 7
pdqaltair is on a distinguished road
They are not too difficult to create, but it does take time.

Simply take many data points and plot with Excel as a circle plot.

Sail Delmarva: Speed Polars

You have to play some games with interpolation and smothing, since wave conditions and load will vary over time. In someways the targets of others are better (depending on how they were developed) and in some ways your own are more valid.

I found I mostly worked on this during long, dull watches.
__________________
(when asked how he reached the starting holds on a difficult rock climbing problem that clearly favored taller climbers - he was perhaps 5'5")

"Well, I just climb up to them."

by Joe Brown, English rock climber




To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message Share with Facebook
  #8  
Old 07-15-2011
Member
 
Join Date: Jun 2011
Location: Vancouver Island
Posts: 35
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
CowbaySailor is on a distinguished road
I found and old book called championship tactics with Gary Jobson and Tom Whidden. In it they have Jim Marshall talking and explaining polar charts. As a radar plotter in the navy I'm pretty sure with a rel vel chart I can figure it out.

Now my question is will I have to plot are each jib in my inventory?
Reply With Quote Quick reply to this message Share with Facebook
  #9  
Old 07-15-2011
pdqaltair's Avatar
Senior Member
 
Join Date: Nov 2008
Location: Deale, MD
Posts: 2,285
Thanks: 1
Thanked 36 Times in 36 Posts
Rep Power: 7
pdqaltair is on a distinguished road
Yes, for every sail combination and reef...

Quote:
Originally Posted by CowbaySailor View Post
I found and old book called championship tactics with Gary Jobson and Tom Whidden. In it they have Jim Marshall talking and explaining polar charts. As a radar plotter in the navy I'm pretty sure with a rel vel chart I can figure it out.

Now my question is will I have to plot are each jib in my inventory?
... but most only plot the largest sails in the inventory.
__________________
(when asked how he reached the starting holds on a difficult rock climbing problem that clearly favored taller climbers - he was perhaps 5'5")

"Well, I just climb up to them."

by Joe Brown, English rock climber




To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message Share with Facebook
  #10  
Old 07-16-2011
Member
 
Join Date: Jun 2011
Location: Vancouver Island
Posts: 35
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
CowbaySailor is on a distinguished road
Thanks for the article on the pdq speed polars that gives me all the info I need. The wing on wing was interesting also. All good stuff.
Reply With Quote Quick reply to this message Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




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
Polar Diagrams sandycohen Racing 18 05-27-2014 01:38 PM
Velocity Prediction Program wwilson General Discussion (sailing related) 0 01-04-2010 12:08 PM
wind predictions xort General Discussion (sailing related) 17 09-26-2008 01:40 PM
How To Find Polar Diagram fo C&C 34? IrishMistRacing Racing 2 06-13-2007 01:02 AM


All times are GMT -4. The time now is 01:49 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.