wind conditions and reefing - Page 6 - 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.


Like Tree38Likes
Reply
 
LinkBack Thread Tools
  #51  
Old 09-24-2012
Senior Member
 
Join Date: Sep 2010
Location: Manhattan
Posts: 133
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 5
AndreasNYC is on a distinguished road
Re: wind conditions and reefing

I was thinking I would strap them to the bottom of the kheel for maximum leverage.

Actually our cockpit is pretty small so where where sitting 3 on the high side and 2 on the low.

A
Reply With Quote Share with Facebook
  #52  
Old 09-24-2012
Senior Member
 
Join Date: Feb 2011
Location: San Francisco Bay area
Posts: 2,250
Thanks: 2
Thanked 38 Times in 38 Posts
Rep Power: 4
MarkSF is on a distinguished road
Re: wind conditions and reefing

In that case the effect is likely to be minimal at best, and could even make the boat tip more. The guys on the high side, when heeled, could be over the centre of mass, while the low side have a considerable arm. As the boat heels more, mass higher up has the effect of reducing the righting moment.
__________________
1984 Bristol 31.1
Alameda, California, USA
Reply With Quote Share with Facebook
  #53  
Old 09-25-2012
AdamLein's Avatar
Senior Member
 
Join Date: Nov 2007
Location: Coquitlam, BC
Posts: 1,866
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 7
AdamLein will become famous soon enough
Re: wind conditions and reefing

Quote:
Originally Posted by MarkSF View Post
In that case the effect is likely to be minimal at best, and could even make the boat tip more. The guys on the high side, when heeled, could be over the centre of mass, while the low side have a considerable arm. As the boat heels more, mass higher up has the effect of reducing the righting moment.
Presumably the folks on the high side are as far or farther from the axis of rotation than the folks on the low side. So their righting arm is as long or longer.

I say "as far or farther" because the center of buoyancy shifts to leeward, which I think implies that the axis of rotation shifts to leeward as well.
__________________
s/v Essorant
1972 Catalina 27
Reply With Quote Share with Facebook
  #54  
Old 09-25-2012
Senior Member
 
Join Date: Feb 2011
Location: San Francisco Bay area
Posts: 2,250
Thanks: 2
Thanked 38 Times in 38 Posts
Rep Power: 4
MarkSF is on a distinguished road
Re: wind conditions and reefing

Quote:
Originally Posted by AdamLein View Post
Presumably the folks on the high side are as far or farther from the axis of rotation than the folks on the low side. So their righting arm is as long or longer.

I say "as far or farther" because the center of buoyancy shifts to leeward, which I think implies that the axis of rotation shifts to leeward as well.

Your first paragraph presumes wrongly that righting arm is only related to distance from axis of rotation. There's a vector component too. Righting moment is proportional to the horizontal component of the distance, as it's gravity acting on the weight, doing the work.

Think of 3 people on each side, with the boat at an extreme angle of heel. The 3 on the high side could be directly over the centre of rotation and despite being a long distance away from it, the horizontal component of their distance is zero and hence they provide no righting moment.

The 3 on the low side are the same distance from the centre of rotation but their horizontal component is maximised. They are making the boat heel more.

Generally the effect of ALL weight above the waterline is to reduce the righting moment, and the more the boat is heeled the more the effect.

The exception is when the weight is on one side, but the effect of that still drops as you heel and can reverse in effect at extreme angles.
__________________
1984 Bristol 31.1
Alameda, California, USA
Reply With Quote Share with Facebook
  #55  
Old 09-25-2012
AdamLein's Avatar
Senior Member
 
Join Date: Nov 2007
Location: Coquitlam, BC
Posts: 1,866
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 7
AdamLein will become famous soon enough
Re: wind conditions and reefing

Quote:
Originally Posted by MarkSF View Post
Your first paragraph presumes wrongly that righting arm is only related to distance from axis of rotation.
It does not. I can make the same argument using only the horizontal component of the distance, which is what I was actually intending.

I guess what I'm not sure about is the vertical location of the axis of rotation, relative to the crew's COG.
__________________
s/v Essorant
1972 Catalina 27
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
How do you guys find ACCURATE wind conditions? NewportNewbie General Discussion (sailing related) 48 11-03-2011 01:34 PM
sail plans at different wind conditions for C37 yzlian Pacific Seacraft 0 04-11-2011 11:25 AM
Is there an Internet website that shows wind, tide, water conditions? kldzx9r General Discussion (sailing related) 9 09-22-2007 11:07 AM
Live wind conditions - what are your favorite web sites? tenuki General Discussion (sailing related) 16 08-15-2007 07:33 AM
Wind conditions test sailors (The Hindu) NewsReader News Feeds 0 05-23-2006 04:15 PM


All times are GMT -4. The time now is 05:02 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.