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 29-08-2019, 14:45   #1
Registered User

Join Date: Aug 2019
Location: Northern California
Posts: 24
deep water anchoring techniques and comparison with shallow

Hi,

I have a trip to Martinique planned, which will be first in Caribbean for me. I am told that Martinique has some deep water anchorages which can be a challenge. Other then the difference in scope requirements due to increased depth, are there any additional considerations I should be aware of? Please kindly let me know your best practices for deep water anchoring.

I have previous experience in Eastern Med anchorages with mud and good holding in 3-10 meter depths, so let me know with compare and contrasts if possible for deep water anchorage techniques. Truly appreciate the experience and wealth of information.
__________________

corsaircpt is offline   Reply With Quote
Old 29-08-2019, 16:07   #2
Elvish meaning 'Far-Wanderer'
 
Palarran's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: Boat - Bahamas - Me - Michigan
Boat: 56' Fountaine Pajot Marquises
Posts: 3,099
Re: deep water anchoring techniques and comparison with shallow

I like anchoring in deep water. The weight of the chain really helps to mellow out the movement of the boat. I can't say what is the norm but what we do is take our time and insure a good set. So we will start at 1000 rpm's in reverse for a minute, wait to see if there is any movement, go to 1500, wait a minute, then finish with 2000 rpm for another minute. This is for water over 25 meters.
__________________

__________________
Our course is set for an uncharted sea
Dante
Palarran is offline   Reply With Quote
Old 29-08-2019, 17:01   #3
Registered User

Join Date: Aug 2019
Location: Northern California
Posts: 24
Re: deep water anchoring techniques and comparison with shallow

Thank you Pallaran. Wrt to rocky bottoms, is there any concern with the chain getting stuck and unable to retrieve ?
corsaircpt is offline   Reply With Quote
Old 29-08-2019, 17:11   #4
Registered User
 
wingssail's Avatar

Join Date: Jan 2010
Location: On Vessel WINGS, wherever there's an ocean, currently in Mexico
Boat: Serendipity 43
Posts: 1,046
Send a message via AIM to wingssail Send a message via Skype™ to wingssail
Re: deep water anchoring techniques and comparison with shallow

I have anchored in over 60' several times. In many places in the South Pacific it was easier to anchor in 65' because at that depth there was less coral to make setting the anchor difficult. Needless to say I don't use 5:1 since I only have 300ft chain. However the catenary of 200-300 ' of chain should be sufficient to keep the pull on the anchor parallel to the bottom.

In fact I would usually put out 3:1 in those depths.

Regarding the risk of getting the anchor caught on the bottom when you cannot free dive to release it: It is good to have a working phone and local contact who can help you hire a diver.
__________________
Sailing is a sport, an athletic activity, not a sedentary one.
Fred Roswold-Fred & Judy, SV Wings, Mexico
http://wingssail.blogspot.com/
wingssail is online now   Reply With Quote
Old 29-08-2019, 17:37   #5
Registered User

Join Date: Jan 2009
Location: Home port is San Diego, California, but Rutea is currently cruising the west coast of Central America.
Boat: Contest 48
Posts: 953
Images: 1
Re: deep water anchoring techniques and comparison with shallow

We had a delightful time in Martinique and the depths at which we anchored were usually in the 4-5 fathom range - Iím not sure where your information came from that indicates otherwise.

When we were in the Maldives there were a couple of occasions where we had to anchor up to 20 fathoms.

Fair winds and calm seas.
nhschneider is offline   Reply With Quote
Old 29-08-2019, 17:38   #6
Elvish meaning 'Far-Wanderer'
 
Palarran's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: Boat - Bahamas - Me - Michigan
Boat: 56' Fountaine Pajot Marquises
Posts: 3,099
Re: deep water anchoring techniques and comparison with shallow

Yah, hard to say about rocky bottoms. We have scuba gear so ultimately we can get it back. Only one time have we had to and then it was stuck on an old mooring line in a harbor in the Peloponnese of Greece. I don't know how much chain you have but can say that after 4 years in the Med we went from 100 meters to 120 meters and quite honestly - needed it often. There are some seriously deep bays in Turkey and Greece where the sides are very steep but the bottoms are flat and have good holding.
__________________
Our course is set for an uncharted sea
Dante
Palarran is offline   Reply With Quote
Old 30-08-2019, 03:14   #7
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Boat: Bestevaer.
Posts: 11,642
Re: deep water anchoring techniques and comparison with shallow

The technique is very much the same. As you note, with chain rode it is possible to reduce the scope especially in mild to moderate conditions. Generally there is little choice, as our sized boats do not carry enough chain for longer scopes in deep water anyway. You can add some rope rode to increase the scope and while there is always the risk of chafe, the drawback can be mitigated by keeping the rope off the bottom, but all chain is still nice.

Because of the lower scope you do need to be a little more careful when anchoring on a downslope. Downslopes reduce the effective scope quite dramatically. Having said that, a few minutes ago I anchored in 29m at 3:1 on a resonable downslope. So the rules can be bent with good gear and a little bit of caution. I hope .

The anchor is no more likely to become caught in deep water, but it becomes impossible to freedive and release the anchor and in the deeper anchorages you reach the stage where even with (recreational) scuba gear the anchor is too deep.

The other consideration is the power of the windlass. Chain is heavy, so deep anchorages place far more demands on the windlass. Ideally try and gradually increase the maximium anchoring depths used and monitor how the windlass is coping with the extra weight.
noelex 77 is offline   Reply With Quote
Old 30-08-2019, 03:37   #8
Registered User

Join Date: Nov 2007
Location: Probably in an anchorage or a boatyard..
Boat: Ebbtide 33' steel cutter
Posts: 4,680
Re: deep water anchoring techniques and comparison with shallow

This is (probably, if the equation is right..) the scope required to just lift the last chain link with 10mm chain and 250Kg force>>


https://www.desmos.com/calculator/gwj6bkzkpv

Equation is scope = square root ( (2 * depth * force) / (chain weight per metre in water * depth * depth) )
Can't actual remember where it came from but seem about right using some online calculators to check, if anyone knows better it would be interesting

Blue line is the equation above, brown line is scope = (2 * depth + 25)/depth which isn't a bad approximation imho. obviously will be different for different chain or force.
conachair is offline   Reply With Quote
Old 30-08-2019, 03:41   #9
Senior Cruiser
 
hpeer's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: Philadelphia
Boat: Murray 33-Chouette & Pape Steelmaid-44-Safara-both steel cutters
Posts: 5,398
Re: deep water anchoring techniques and comparison with shallow

We have been into St Pierre a few times and St Anne once.

St Pierre is steep to but there is generally room for 2-3 layers of boats in reasonable depth. I tend to anchor on the South end near Anse Turin, it’s a bit wider area and quieter but a longer dingy ride to town. There is a lot of churn so if you don’t like your spot wait until morning and move. Try to arrive with sufficient daylight. I came in at midnight because of engine trouble and anchored on the extreme N end but I was in the way of local fishermen who let me know I was in the wrong place, quite firmly.

There is a bit of current so you can swing. The bottom was not foul.

St Anne is busy but not excessively. Good anchoring there.
hpeer is offline   Reply With Quote
Old 30-08-2019, 09:30   #10
Registered User

Join Date: Nov 2016
Location: Gulf Coast of FL
Boat: Pearson
Posts: 317
Re: deep water anchoring techniques and comparison with shallow

Depending on your anchor a trip line can be attached to the bottom of the anchor and attach a float so the line travels directly up so it doesn t snag, a fender can be used as a float. If snagged take in all scope motor directly over the anchor and sometimes the boars rocking motion will break it free, or motor to the oposite side of how its set and pull in that direction. A all chain rode makes this more difficult.
__________________
Ken Z
Ken Z is offline   Reply With Quote
Old 30-08-2019, 10:25   #11
Registered User

Join Date: Sep 2013
Location: Alert Bay, Vancouver Island
Boat: 35ft classic ketch/yawl.
Posts: 1,586
Images: 4
Send a message via Skype™ to roland stockham
Re: deep water anchoring techniques and comparison with shallow

A rule of thumb I have for all chain anchoring is 12m plus 3x depth (comes from the RYA) it allows for the scope reduction in deeper water and works up to 20m. It does assume the correct weight of chain and anchor for your boat. Most boats do not have a windlass that will lift more than about 20m chain and the anchor from the bottom so that creates the effective limit. Around here (Pacific NW) it is common to find 100ft+ within a few meters of the shore so many people carry 3 long lines and tie to a tree!!
roland stockham is offline   Reply With Quote
Old 30-08-2019, 10:50   #12
MJH
Registered User

Join Date: Feb 2007
Location: Gig Harbor, WA
Boat: Tayana Vancouver 42ac
Posts: 286
Re: deep water anchoring techniques and comparison with shallow

Quote:
Originally Posted by corsaircpt View Post
Hi,

I have a trip to Martinique planned, which will be first in Caribbean for me. I am told that Martinique has some deep water anchorages which can be a challenge. Other then the difference in scope requirements due to increased depth, are there any additional considerations I should be aware of? Please kindly let me know your best practices for deep water anchoring.

I have previous experience in Eastern Med anchorages with mud and good holding in 3-10 meter depths, so let me know with compare and contrasts if possible for deep water anchorage techniques. Truly appreciate the experience and wealth of information.
I have not been to Martinique but deep anchoring in the Northwest is an everyday experience. I would say 60 feet is the norm and have had to anchor at 100' a time or two. A lot depends on the weather, bottom, and how protected you may be in a blow. I have 300' of 5/16' High Test chain and put out 250' a couple times a year.

When taking up your anchor it helps to be moving forward slowly under engine power on the reverse course of putting it out. I've never had a stuck anchor but if you do bring in as much as you can at low tide and let the rising tide do the rest.

~ ~ _/) ~ ~ MJH
MJH is offline   Reply With Quote
Old 30-08-2019, 11:11   #13
Registered User

Join Date: Aug 2016
Location: Becalmed in the Med
Boat: Prout Snowgoose 35
Posts: 1,181
Re: deep water anchoring techniques and comparison with shallow

I found that if the bottom is flat you can reduce scope significantly, since you have a lot more weight in the chain that isn't sitting on the bottom.

Retrieving the anchor if stuck will be difficult unless you are a world class freediver or carry scuba gear, and have someone else onboard. You can attach a trip line. If i know the area is foul I like to attach one, that is beneath the water when anchored in over say 14m. Deep enough to avoid even large boats snagging it, but shallow enough that I can dive on it.

If you have a decent windlass then weight shouldn't be a problem, but might take longer to weight the anchor. The working load of an 800w windlass is around 120kg, and maximum of 350kg. The only weight you lift is that which is not sitting on the bottom, so if you have 10mm chain weighs around 2kg per meter. So you could have a 25kg anchor, and 40m below the surface and still be within the normal working limits of the windlass.
mikedefieslife is offline   Reply With Quote
Old 30-08-2019, 12:24   #14
Registered User

Join Date: Jul 2009
Location: Cruising the Caribbean
Boat: Island Packet 40
Posts: 70
Re: deep water anchoring techniques and comparison with shallow

I wouldnít be too concerned about deep anchorages in Martinique, we have spent several months there in the last couple of seasons. On average I would say that most anchorages are under 30 feet with the very odd spot you may run across 40. There are spots where you will watch your anchor hit the bottom in 15 feet of clear water. Anse Mitan is one spot where the shallower areas get taken up first and you may end up in 40 feet. I concur with another poster about St Pierre, anchor just south of the main anchorage, there are a couple of small bays there. Keeps you out of the sh*t show of everyone trying to anchor on the shelf in town. St Anne is a fabulous spot, easy anchorage with plenty of sand and can hold hundreds of boats. Nice little village with the town of Marin a dingy ride away with all amenities.
lovinlifebda is offline   Reply With Quote
Old 30-08-2019, 13:21   #15
Registered User

Join Date: Aug 2019
Location: Northern California
Posts: 24
Re: deep water anchoring techniques and comparison with shallow

thank you all, lovinlifedba especial thanks. mikedefieslifem this was quite good so thank you. Pallaran, agree with comments about Turkey and Greece. My sailing in Turkish southwest coast has been exceptional, just a heavenly spot all around.
__________________

corsaircpt is offline   Reply With Quote
Reply

Tags
anchor, anchoring, water

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
deep draft/shallow draft Miran Monohull Sailboats 5 27-07-2017 14:36
Same stability for deep and shallow draft??? GTom Monohull Sailboats 33 06-03-2017 10:26
Shallow keel for shallow water? troppo General Sailing Forum 12 01-03-2016 15:24
Anchoring in Exposed Shallow Water: How Quickly Things Can Change . . . thinwater Anchoring & Mooring 9 19-10-2011 18:25
Shallow Water Anchoring sailorboy1 Anchoring & Mooring 50 10-12-2010 03:58

Advertise Here


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 17:46.


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.