Reduction in anchor scope with chain use - Page 3 - SailNet Community
 5Likes
Reply
 
LinkBack Thread Tools
post #21 of 21 Old 10-17-2012
PCP
Senior Member
 
PCP's Avatar
 
Join Date: Dec 2004
Location: Portugal, West Coast
Posts: 16,201
Thanks: 21
Thanked 103 Times in 86 Posts
Rep Power: 11
 
Re: Reduction in anchor scope with chain use

Quote:
Originally Posted by klem View Post
...

Line effectively provides no catenary so the angle of pull on the anchor is determined by the scope. In calm weather, chain provides catenary and the angle of pull on the anchor will be parallel to the bottom. However, in conditions that actually test the holding power of the anchor, the chain will be stretched out straight and the angle of pull will be determined by the scope, there is effectively no catenary in these conditions. Therefore, the holding power of the anchor is determined by the scope and is independent of what the rode is made out of unless you have ridiculously heavy chain (I am thinking of captaaron and his 5/8" chain on a <30' boat).

Keeping the loads down means providing some shock absorption in the system. Line is a good shock absorber because it is relatively stretchy. In calmer conditions, chain is an okay shock absorber because it has catenary. In stronger conditions, the chain is effectively a steel rod and it has virtually no shock absorption meaning that the loads are higher on the anchor. When you are in conditions bad enough to be testing the anchor's holding power, line will yield lower loads on the anchor.

In conditions that test your anchor, you do not need any less scope with chain than line. Since chain is a terrible shock absorber, you really need a good snubber in bad conditions. Chain still has other benefits such as chafe resistance, easier setting, etc so we shouldn't go out and ditch all of our chain but this rule of thumb is totally bogus.
On windy conditions I use two mooring lines connected to the chain by shackles. The lines have big rubber shock absorbers, the kind that have the line passed several times around. That system provides a good shock absortion especially with waves, making also the live aboard more comfortable on those conditions.

Regards

Paulo
PCP is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

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:
OR

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
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Anchor Rode and Scope for Marker Buoy jetdrvr393 Gear & Maintenance 3 05-13-2012 02:00 PM
G5 5/16 HT Anchor Chain interlude44 General Discussion (sailing related) 4 12-21-2009 08:10 AM
Anchor Chain TxLnghrn Gear & Maintenance 9 12-24-2008 05:03 PM
Anchor chain geoffr98 Gear & Maintenance 4 07-29-2007 04:09 PM
anchor chain SteveCox Gear & Maintenance 11 07-22-2006 07:39 PM

Posting Rules  
You may post new threads
You may 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome