Forces on a dockline while docking.... - Page 5 - 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 > General Interest > General Discussion (sailing related)
 Not a Member? 


Like Tree17Likes
Reply
 
LinkBack Thread Tools
  #41  
Old 05-01-2013
pdqaltair's Avatar
Senior Member
 
Join Date: Nov 2008
Location: Deale, MD
Posts: 2,267
Thanks: 1
Thanked 36 Times in 36 Posts
Rep Power: 7
pdqaltair is on a distinguished road
Re: Forces on a dockline while docking....

Quote:
Originally Posted by svHyLyte View Post
... or intuitively understand or appreciate that kinetic energy is equal to the integral of the dot product of the velocity of a body and the differential change of the body's momentum....
Yup, that's one way of making it complicated.

I guess what I'm suggesting, in a way, is a simplification; wouldn't it be nice if ropes were rated for both strength and energy absorption per foot over a few thousand cycles. That matters more, for most applications. It also makes the calculations for dock lines and anchor rodes simpler, since the surge energy is what matters. Two ropes may be of the same strength, but what about fatigue life?

Climbing ropes are rates simply; the number of standard falls survived, with a limit on extension and impact force.
__________________
(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
  #42  
Old 05-02-2013
svHyLyte's Avatar
Old as Dirt!
 
Join Date: Nov 2008
Location: Tampa Bay Area
Posts: 2,823
Thanks: 15
Thanked 114 Times in 108 Posts
Rep Power: 7
svHyLyte is on a distinguished road
Re: Forces on a dockline while docking....

Quote:
Originally Posted by pdqaltair View Post
...I guess what I'm suggesting, in a way, is a simplification; wouldn't it be nice if ropes were rated for both strength and energy absorption per foot over a few thousand cycles. That matters more, for most applications. It also makes the calculations for dock lines and anchor rodes simpler, since the surge energy is what matters.....
I agree with this sentiment entirely although, frankly, I suspect most non-technical types might not understand the information and thus apply it improperly. Frankly, I would wager many do not understand the significance of the information presented in this thread though it really can be quite important. Knowing how to use a snubbing line/spring to warp a boat around, or stop her, can be the difference between relief and (serious) regret.

FWIW...
__________________
"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
Reply With Quote Quick reply to this message Share with Facebook
  #43  
Old 05-02-2013
Thanks Courtney.
 
Join Date: Sep 2006
Location: IL
Posts: 3,954
Thanks: 1
Thanked 1 Time in 1 Post
Rep Power: 11
T34C has a spectacular aura about T34C has a spectacular aura about T34C has a spectacular aura about
Re: Forces on a dockline while docking....

Knowing the energy absorption of the dockline might be a great idea, but whats the energy absorption of the cleat on the dock? Or the bolts holding the cleat, etc... Seems like using a better docking procedure might be a better idea since you would eliminate many of those variable.
Tempest and svHyLyte like this.
__________________
hunter Legend 37 Semper Paratus
Formerly - Tartan 34C Yawl
Reply With Quote Quick reply to this message Share with Facebook
  #44  
Old 05-02-2013
svHyLyte's Avatar
Old as Dirt!
 
Join Date: Nov 2008
Location: Tampa Bay Area
Posts: 2,823
Thanks: 15
Thanked 114 Times in 108 Posts
Rep Power: 7
svHyLyte is on a distinguished road
Re: Forces on a dockline while docking....

Quote:
Originally Posted by T34C View Post
Knowing the energy absorption of the dockline might be a great idea, but whats the energy absorption of the cleat on the dock? Or the bolts holding the cleat, etc... Seems like using a better docking procedure might be a better idea since you would eliminate many of those variable.
Unless I really know a marina's equipment, I will only surge/snub from a piling. I have seen more than one bulkhead/dock cleat ripped out by a snubbing/surge line and with the line under much pressure, they are slung like a rock from a sling-shot.
__________________
"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
Reply With Quote Quick reply to this message Share with Facebook
  #45  
Old 05-02-2013
Member
 
Join Date: Jul 2012
Location: Baytown Texas
Posts: 94
Thanks: 1
Thanked 1 Time in 1 Post
Rep Power: 3
Tallswede is on a distinguished road
Re: Forces on a dockline while docking....

Quote:
Originally Posted by svHyLyte View Post
Unless I really know a marina's equipment, I will only surge/snub from a piling. I have seen more than one bulkhead/dock cleat ripped out by a snubbing/surge line and with the line under much pressure, they are slung like a rock from a sling-shot.
Ain't that the truth! I've seen more than one cleat pulled out and a couple launched. Visiting backwater marinas while exploring is a good way to learn alternate docking procedures. Most are not very well equiped with cleats so pilings and other protrusions have to suffice. I really like the looks of that docking thingy for use with a boat hook and after reading this thread will go out and practice other methods besides just going slow.

Kevin
Reply With Quote Quick reply to this message Share with Facebook
  #46  
Old 05-02-2013
jrd22's Avatar
Courtney the Dancer
 
Join Date: Nov 2000
Location: San Juan Islands., WA, USA
Posts: 3,828
Thanks: 3
Thanked 16 Times in 16 Posts
Rep Power: 15
jrd22 will become famous soon enough
Re: Forces on a dockline while docking....

40+' sailboat, full throttle in forward, 40 knot tailwind, one line coming tight on a cleat = something is going to give. Unless it's a perfectly straight, unobstructed path from the deck to the dock cleat there's going to be a chafe/break spot, and unless both ends are spliced eyes any knot is going to reduce the breaking strength of the line by about 50%. I suspect that the skipper was allowing the line to slip around the winch to avoid the shock load.
__________________
John
SV Laurie Anne

1988 Brewer 40 Pilothouse

Reply With Quote Quick reply to this message Share with Facebook
  #47  
Old 05-02-2013
Thanks Courtney.
 
Join Date: Sep 2006
Location: IL
Posts: 3,954
Thanks: 1
Thanked 1 Time in 1 Post
Rep Power: 11
T34C has a spectacular aura about T34C has a spectacular aura about T34C has a spectacular aura about
Re: Forces on a dockline while docking....

Quote:
Originally Posted by svHyLyte View Post
Unless I really know a marina's equipment, I will only surge/snub from a piling. I have seen more than one bulkhead/dock cleat ripped out by a snubbing/surge line and with the line under much pressure, they are slung like a rock from a sling-shot.
I've also seen old pilings that were previously thought very strong simply break off..
__________________
hunter Legend 37 Semper Paratus
Formerly - Tartan 34C Yawl
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
Forces acting on mast plate Barquito Gear & Maintenance 25 02-22-2013 05:25 PM
Wow, bad dockline setup.... SHNOOL General Discussion (sailing related) 12 08-09-2011 08:15 PM
transient dockline inventory -single vs. double braid? hazmat17 Gear & Maintenance 3 06-04-2010 10:51 AM
Dockline failure from snubber argofred Gear & Maintenance 24 07-24-2009 06:13 PM
Loads & Forces on a Sailboat FishFinder Gear & Maintenance 6 05-01-2009 05:27 PM


All times are GMT -4. The time now is 07:14 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.