Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 30-11-2010, 07:13   #1
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: The boat: Cowes (Winter), Above 60N (Summer); me: somewhere in the air!
Boat: Cutter-Rigged Moody 54
Posts: 23,843
Anchoring Stern-to in a Storm

Have we come to any conclusions about this? I recall it was much discussed over the years.

The problem with lying to an anchor in a really bad storm is that the center of aerodynamic pressure of your boat with the sails down is ahead of the boats center of gravity as well as the boat's keel. That means that wind pressure tends to make the boat's head fall off -- tends to blow the bow off. It means that being anchored bow-to is inherently unstable in a strong wind.

That's the same principle which explains why it can be hard to get your boat's head through the wind when it's really blowing. And why backing up into a strong wind is the best way to maneuvre in close quarters and strong wind. Your boat will back into a strong wind with stability, because the wind will not blow the stern around like it does the bow. That's because the center of pressure is behind your keel, when you're backing up, so the effect of wind when backing upwind is just to keep you on course, not blow you off.

Apparently that's the same principle that makes a boat yaw at anchor in a strong wind. This yawing can break your anchor rode or snubbers or bridle in a really bad storm. There are many accounts of boats anchored in hurricanes yawing wildly, and being knocked on their beam ends at the end of every yaw, putting huge stresses on the ground tackle.

So someone recommended anchoring stern-to in such conditions, claiming that the boat will lie stably like that.

Has anyone actually tried this out in anger? Any thoughts?
__________________

Dockhead is online now   Reply With Quote
Old 30-11-2010, 07:21   #2
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29 49.16 N 82 25.82 W
Boat: Pearson 422
Posts: 13,746
Have you read the writeup by Don Jordan, developer of the Jordan Series Drogue?

Jordan Series Drogue - Mooring and Anchoring
__________________

__________________
The water is always bluer on the other side of the ocean.

Sometimes it's necessary to state the obvious for the benefit of the oblivious.

Rust is the poor man's Loctite.
skipmac is offline   Reply With Quote
Old 30-11-2010, 07:26   #3
Freelance Delivery Skipper..
 
boatman61's Avatar

Community Sponsor
Cruisers Forum Supporter

Join Date: Jan 2010
Location: PORTUGAL
Posts: 23,482
Images: 2
pirate

Quote:
Originally Posted by Dockhead View Post
Have we come to any conclusions about this? I recall it was much discussed over the years.

The problem with lying to an anchor in a really bad storm is that the center of aerodynamic pressure of your boat with the sails down is ahead of the boats center of gravity as well as the boat's keel. That means that wind pressure tends to make the boat's head fall off -- tends to blow the bow off. It means that being anchored bow-to is inherently unstable in a strong wind.

That's the same principle which explains why it can be hard to get your boat's head through the wind when it's really blowing. And why backing up into a strong wind is the best way to maneuvre in close quarters and strong wind. Your boat will back into a strong wind with stability, because the wind will not blow the stern around like it does the bow. That's because the center of pressure is behind your keel, when you're backing up, so the effect of wind when backing upwind is just to keep you on course, not blow you off.

Apparently that's the same principle that makes a boat yaw at anchor in a strong wind. This yawing can break your anchor rode or snubbers or bridle in a really bad storm. There are many accounts of boats anchored in hurricanes yawing wildly, and being knocked on their beam ends at the end of every yaw, putting huge stresses on the ground tackle.

So someone recommended anchoring stern-to in such conditions, claiming that the boat will lie stably like that.

Has anyone actually tried this out in anger? Any thoughts?
A reasonable assumption.. till you look at the problems..

1/ No boat is set up with fittings strong enough to take the loads...

2/ Great until the waves start then the blunt stern will add to the loads as the waves smack up against it... also there's the likelyhood that they'll start flooding your cockpit.... as for those with a canoe stern... would that not yaw as well..

Maybe someone knows better...
__________________


Born To Be Wild.. Click on the picture.
boatman61 is offline   Reply With Quote
Old 30-11-2010, 07:26   #4
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: The boat: Cowes (Winter), Above 60N (Summer); me: somewhere in the air!
Boat: Cutter-Rigged Moody 54
Posts: 23,843
Quote:
Originally Posted by skipmac View Post
Have you read the writeup by Don Jordan, developer of the Jordan Series Drogue?

Jordan Series Drogue - Mooring and Anchoring
Indeed, that's one of my main sources of information. I find it totally convincing, but the purpose of this thread is to find out whether others have confirmed any of this theory in practice.
Dockhead is online now   Reply With Quote
Old 30-11-2010, 07:28   #5
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: The boat: Cowes (Winter), Above 60N (Summer); me: somewhere in the air!
Boat: Cutter-Rigged Moody 54
Posts: 23,843
Quote:
Originally Posted by boatman61 View Post
A reasonable assumption.. till you look at the problems..

1/ No boat is set up with fittings strong enough to take the loads...

2/ Great until the waves start then the blunt stern will add to the loads as the waves smack up against it... also there's the likelyhood that they'll start flooding your cockpit.... as for those with a canoe stern... would that not yaw as well..

Maybe someone knows better...
I'm particularly interested in these questions -- practical experience.

As to fittings -- it might be worthwhile to create them for this purpose. You need them anyway in order to use a Jordan series drogue.

As to waves -- interested in people's experience. I suppose different boats will suffer from this to different degrees -- big center cockpit boats probably least susceptible.
Dockhead is online now   Reply With Quote
Old 30-11-2010, 07:39   #6
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2006
Posts: 1,594
Yup

that's my quote about the subject to Mr Jordan..

I've only used it in winds upward of 25-35kts and the difference was amassing....

A Cape Dory's wineglass stern has no issues with wind waves from astern that I felt... Waves were only a few feet though....


All of Seraph's cleats are through bolted with 1/4 alum backing plates... They'll handle the load....

I will be adding 'stern chainplates' to handle the series drogue before sailing off.
__________________
Randy

Cape Dory 25D Seraph
rtbates is offline   Reply With Quote
Old 30-11-2010, 07:44   #7
Registered User
 
Tallswede's Avatar

Join Date: Jun 2010
Location: Baytown Tx
Boat: Hunter 23.5, AMF Sunbird & 36' Prairie Trawler
Posts: 101
It seems to me, you could be putting a lot of pressure on your rudder fittings also. Especially a vessel with a transom hung rudder. Waves hitting the transom could put some great force onto the fittings. Every boat being different, you would have to assess yours as to how it would handle these stresses.

Kevin
Tallswede is offline   Reply With Quote
Old 30-11-2010, 07:46   #8
Freelance Delivery Skipper..
 
boatman61's Avatar

Community Sponsor
Cruisers Forum Supporter

Join Date: Jan 2010
Location: PORTUGAL
Posts: 23,482
Images: 2
pirate

Quote:
Originally Posted by Dockhead View Post
I'm particularly interested in these questions -- practical experience.

As to fittings -- it might be worthwhile to create them for this purpose. You need them anyway in order to use a Jordan series drogue.

As to waves -- interested in people's experience. I suppose different boats will suffer from this to different degrees -- big center cockpit boats probably least susceptible.
Anchorings a totally different thing to trailing a drogue.... one is designed to slow your rate of drift...
The other is to STOP any possible drift... loads would more than double...
__________________


Born To Be Wild.. Click on the picture.
boatman61 is offline   Reply With Quote
Old 30-11-2010, 07:57   #9
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: The boat: Cowes (Winter), Above 60N (Summer); me: somewhere in the air!
Boat: Cutter-Rigged Moody 54
Posts: 23,843
Quote:
Originally Posted by boatman61 View Post
Anchorings a totally different thing to trailing a drogue.... one is designed to slow your rate of drift...
The other is to STOP any possible drift... loads would more than double...
Yes, but double a given load is not a huge engineering difference. So if you're creating the strong points anyway, you just double their strength. I don't think this is a fatal problem to anchoring stern-to.

Also, remember, that if the theory actually works in practice, you will have dramatically less snatch loads than an ordinary anchor rode has to suffer.

I think experience with trailing drogues may also be relevant on the wave question. I understand that waves do not typically crash over the stern of boats trailing drogues. The waves lift them up and over. I wonder if this is true to boats anchored stern-to, also?
Dockhead is online now   Reply With Quote
Old 30-11-2010, 08:03   #10
Senior Cruiser
 
sneuman's Avatar

Cruisers Forum Supporter

Join Date: May 2003
Location: Jamaica
Boat: Tayana 37 Cutter
Posts: 3,169
Images: 37
Quote:
Originally Posted by boatman61 View Post
A reasonable assumption.. till you look at the problems..

1/ No boat is set up with fittings strong enough to take the loads...

2/ Great until the waves start then the blunt stern will add to the loads as the waves smack up against it... also there's the likelyhood that they'll start flooding your cockpit.... as for those with a canoe stern... would that not yaw as well..

Maybe someone knows better...
Canoe stern/double enders exempted from #2?
__________________
Voyage of Symbiosis: http://svsymbiosis.blogspot.com/
sneuman is offline   Reply With Quote
Old 30-11-2010, 08:04   #11
Registered User
 
swagman's Avatar

Join Date: Sep 2005
Location: Winter land based UK New Forest. Summer months away. Making the transition from sail to power this year - scary stuff.
Boat: Super Van Craft 1320 Power Yacht
Posts: 2,175
Images: 10
Send a message via Skype™ to swagman
If you've a canoe stern and a very strong rudder I am sure hanging backwards may feel ok. If you've any other style of boat I suspect not.

The design of all boats will find the greatest hull strength right on the bow; the aerodynamics flowing from the bow to aft is usually better than the other way around, and as is a simple matter to prevent yawing by hanging a drogue off ones anchor chain, why bother hanging backward?

Most modern designs hung from the stern would soon find the wave slop onto broad transoms driving the crew mad. It could certainly place greater wear onto a skeg or spade rudder.

Methinks this is all why most hang from the bow.

Cheers
JOHN
__________________
Don't take life too seriously. No ones going to make it out alive......Go see our blog at http://www.sailblogs.com/member/yachtswagman/
swagman is offline   Reply With Quote
Old 30-11-2010, 08:08   #12
Registered User
 
Tallswede's Avatar

Join Date: Jun 2010
Location: Baytown Tx
Boat: Hunter 23.5, AMF Sunbird & 36' Prairie Trawler
Posts: 101
I think if I had a canoe sterned boat I would anchor it by the stern. I've anchored my little boats by the stern in protected spots and enjoyed not sailing around at anchor. If the waves pick up though, the slapping and pounding get old quick. LOL

Kevin
Tallswede is offline   Reply With Quote
Old 30-11-2010, 08:10   #13
Registered User

Join Date: Aug 2010
Posts: 976
I'm pretty sure that backing into the wind when slow-speed manuvering has nothing to do with the shape of the bow, stern or hull. Rather I believe it has to do with the location of the prop and the force being generated while under power.

Think of trying to drag a rope vs. trying to push a rope. I don't think this can be likened to anchoring bow into the wind or stern into the wind. While the bow may drift, it is still designed to ride up and over or through the waves, while the stern is decidedly not. Nor is the stern designed to take waves up over the transom, while the bow is designed to be able to be buried into a wave.

Ive' seen quite a few small boats get swamped anchoring and docking stern to, while those next to it, bow to ride it out just fine. Just a thought, but hey, what do I know.
Shrew is offline   Reply With Quote
Old 30-11-2010, 08:49   #14
Registered User

Join Date: Dec 2009
Posts: 3,016
Images: 4
The stern of most cruising boats is significantly overloaded. Plus some recent designs place much of the buoyancy far aft. These issues make taking seas on the stern problematic. Then there's the reverse transom and open transom of some boats....
daddle is offline   Reply With Quote
Old 30-11-2010, 09:19   #15
Registered User

Join Date: May 2008
Posts: 2,246
Jordan's stern-to mooring is intended for protected anchorages where wind loading (especially during a yaw) rather than wave action is the the principal source of stress. This is reasonable since it is far easier to find a wave protected anchorage than a wind protected anchorage.

Many of today's boats have woefully unsupported bow cleats - often installed in the middle of an unsupported piece of deck with no solid timber going to the keel or even a heavy cross member. If there are two cleats, they often are in the same piece of weak deck. By contrast, there's a lot of beefy places to attach cleats or strong points in the stern quarter of most boats where laminates for the hull and deck come together and the gunwale forms a natural I beam.

Better, most stern cleats don't need chocks to have a fair lead for a bridle - removing the single biggest risk of parting a line.


Carl
__________________

CarlF is offline   Reply With Quote
Reply

Tags
anchor, anchoring

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale: Sea Anchor, Storm Tri-Sail, Storm Jib Gailwind Classifieds Archive 15 24-10-2010 06:24
Docking Stern in First wingover Seamanship & Boat Handling 18 28-06-2010 03:34
Anchoring for a Storm SCCatSailor Multihull Sailboats 45 13-09-2008 15:34
Stern extension? Brandywine Multihull Sailboats 6 10-02-2008 17:39
anchoring by the stern. rtbates Seamanship & Boat Handling 25 18-02-2007 00:38



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 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.