Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 05-08-2011, 23:30   #1
Registered User
 
rhumbunctious's Avatar

Join Date: Nov 2010
Posts: 68
Hammocks and Stress on Standing Rigging

I see alot of hammocks strung up on decks, attached to the standing rigging (e.g. forestay and shrouds, etc.) and while it's clear that this works, I've been wondering what kind of stress and possible reduction in lifespan this may cause to the rigging. Since the stresses on standing rigging are expected to be vertical along the length of the wire, and the hammock places a bending stress horizontally, what is that doing to the wire? Is it causing or increasing work hardening at the point of stress/bend?

I'm wanting to string a hammock up myself, but am concerned about the long term affects/damage to the rigging.

Any experts care to comment?
__________________

__________________
If a man speaks at sea where there is no woman to hear, is he still wrong?
-
Cruising the Baltic in 'Merihiisi', a 1979 Westerly Berwick Ketch
rhumbunctious is offline   Reply With Quote
Old 05-08-2011, 23:39   #2
Registered User
 
avb3's Avatar

Cruisers Forum Supporter

Join Date: Jul 2010
Location: Florida/Alberta
Boat: Lippincott 30
Posts: 9,913
Images: 1
Re: Hammocks and stress on standing rigging

Quote:
Originally Posted by rhumbunctious View Post
I see alot of hammocks strung up on decks, attached to the standing rigging (e.g. forestay and shrouds, etc.) and while it's clear that this works, I've been wondering what kind of stress and possible reduction in lifespan this may cause to the rigging. Since the stresses on standing rigging are expected to be vertical along the length of the wire, and the hammock places a bending stress horizontally, what is that doing to the wire? Is it causing or increasing work hardening at the point of stress/bend?

I'm wanting to string a hammock up myself, but am concerned about the long term affects/damage to the rigging.

Any experts care to comment?
I am NOT an expert, but I would suspect the stresses on the rigging inflicted in the normal course of sailing would be much higher then a static stress that a hammock produces.

Again, not an expert, but common sense tells me the loads from sails are significant higher then a 180 Lb or a 220 lb person just lounging.

I would be more concerned that whatever attachment mechanism I used doesn't the impact integrity of the wire.
__________________

__________________
If your attitude resembles the south end of a bull heading north, it's time to turn around.
avb3 is offline   Reply With Quote
Old 05-08-2011, 23:51   #3
Registered User
 
rhumbunctious's Avatar

Join Date: Nov 2010
Posts: 68
Re: Hammocks and stress on standing rigging

Quote:
Originally Posted by avb3 View Post
I am NOT an expert, but I would suspect the stresses on the rigging inflicted in the normal course of sailing would be much higher then a static stress that a hammock produces.

Again, not an expert, but common sense tells me the loads from sails are significant higher then a 180 Lb or a 220 lb person just lounging.

I would be more concerned that whatever attachment mechanism I used doesn't the impact integrity of the wire.
The stresses along the direction of the rigging are certainly much more when sailing, but when sailing there aren't stresses across the rigging, perpendicular to the wire. You're quite right about how the hammock is attached is the concern.
__________________
If a man speaks at sea where there is no woman to hear, is he still wrong?
-
Cruising the Baltic in 'Merihiisi', a 1979 Westerly Berwick Ketch
rhumbunctious is offline   Reply With Quote
Old 06-08-2011, 02:48   #4
Registered User

Join Date: Jul 2011
Location: Boston, MA
Boat: 1990 Irwin 43 CC
Posts: 50
Re: Hammocks and stress on standing rigging

Although the force is probably more than 200 lbs because of the angle, I tend to agree that on any boat 25 ft or larger the stress jnduced through the use of a hammock is minimal.On a smaller boat that has loose rigging, it may indice some kinks.
__________________
Ahmet, S/V Waterdancer 1990 Irwin 43 CC
Winthrop Yacht Club
Moderator BostonLiveaboards Yahoo Group
waterdancer is offline   Reply With Quote
Old 06-08-2011, 04:46   #5
Registered User
 
dockbumdan's Avatar

Join Date: Feb 2011
Location: Onboard Georgetown, MD.
Boat: Seidelmann, S37' 1985
Posts: 46
Send a message via Skype™ to dockbumdan
Re: Hammocks and stress on standing rigging

I have a hammack rigged between my roller furler and my mast, boat's a 37, I use the same ATN crusing spinnaker "Tacker" that I use for flying my crusing spinaker, I can't imagine that the stress induced by my weight onto the furler is more than the stress caused by the spinnaker.
__________________
SV\Trinity
www.sailingtrinity.com
Docbum@me.com
dan.sloopjb@gmail.com
If you never ran aground, Your Not Sailing!
dockbumdan is offline   Reply With Quote
Old 06-08-2011, 09:31   #6
Senior Cruiser
 
Jim Cate's Avatar

Cruisers Forum Supporter

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 11,454
Re: Hammocks and Stress on Standing Rigging

Consider the loads imposed on your forestay by a partly furled genoa... the hammock will not overstress the shrouds unless an elephant should have a nap in it.... on a trailer sailor!

Cheers,

Jim
__________________
Jim and Ann s/v Insatiable II , lying Port Cygnet, Tasmania once again
Jim Cate is offline   Reply With Quote
Old 06-08-2011, 09:44   #7
Registered User
 
Unicorn Dreams's Avatar

Join Date: Aug 2007
Location: Clear Lake Marine Services - Seabrook, Texas
Boat: Gulfstar, Mark II Ketch, 43'
Posts: 2,359
Re: Hammocks and Stress on Standing Rigging

I don't think that 100 lbs. or so side load on 1/4" cable is going to be much, toggles should eliminate some of the stress.
I swing my hammocks under the booms of my boat.
Admiral has a tendency when I'm sleeping and don't answer her, to loosen the main sheet and let the boom swing over the side of the boat. Just glad I don't tie slip knots when rigging it. She hust might untie and dump me in the drink..
__________________
Formerly Santana
The winds blow true,The skies stay blue,
Everyday is a good day for SAILING!!!!
Unicorn Dreams is offline   Reply With Quote
Old 06-08-2011, 10:01   #8
Registered User

Join Date: Dec 2009
Posts: 3,016
Images: 4
Re: Hammocks and Stress on Standing Rigging

A quick estimate with pencil...a 100kg person is probably not a problem. An elephant, no way. The sideways pull on the forestay is maybe 100kg...depends on the sag in the hammock (more sag, less force). The tension in the stay will be from 10 to 40 times that (up to 4000kg or 8800# on a really tight rig) depending on the amount of forestay sag (more sag, less tension).

So it's not insignificant in some cases. And I could imagine the wire or foil getting a kink in it from the sharp bend if the rig was really loose or the napper was a big fan of cheeseburgers.
__________________
daddle is offline   Reply With Quote
Old 06-08-2011, 10:08   #9
Registered User

Join Date: Jun 2011
Location: Oahu, HI
Boat: Pearson Vanguard 32
Posts: 47
Re: Hammocks and Stress on Standing Rigging

Use multiple lines attaching the hammock to the forestay to spread the load. That or a couple sheets of stiff leather around the forestay as well.

That would help to prevent kinks.

Still doesnt prevent the overall total stress on the forestay though....
__________________

__________________
Acedude is offline   Reply With Quote
Reply

Tags
rigging

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not 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 Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 01:43.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.