Anchor question - Page 3 - SailNet Community
 11Likes
Reply
 
LinkBack Thread Tools
post #21 of 29 Old 07-11-2015
Senior Member
 
windnrock's Avatar
 
Join Date: May 2012
Location: On my boat
Posts: 151
Thanks: 3
Thanked 4 Times in 3 Posts
Rep Power: 8
 
Re: Anchor question

This is a discussion that apparently will never end. Physics is governed by certain "laws". If I have 150' of 3/8' chain out at approximately 225 lb.(less 13% for steel in salt water or 196 lb.), even if the wind is howling and the chain pulled straight, the mass or weight of the chain remains unchanged and presses down both on the bow of the boat as well as the anchor. Because it is not a straight rod, it also, stated simply, exerts force inwards >< .
A small, lightweight, aluminum Fortress or Danforth on a nylon rode is absolutely fine for many applications. Day sailors have relied on this equipment for a long time without too many problems. But, an aluminum anchor that weighs 10 lb. in your hand only weighs about 6 on the bottom (a 10 lb. steel anchor weighs about 8.5 lbs. in salt water) So, if you have a hard or grassy bottom you will have issues. If the wind comes up or the current switches around, you will have issues. The same anchor, made from heavier material will work better. It may only be slightly better but more weight is what you want for holding, period. The size of the flukes will only matter if they get buried.
There is a very good reason why so many people are switching to more modern designs, they work better.
My primary consideration was not storage but keeping my home where I put it. I employ the heaviest anchor I feel I can work with in difficult conditions, 77 lb. I chose a design that works better on most bottoms than others, a Rocna. I attached it to the boat with the heaviest rode I could deploy and recover manually even in deep anchorages, 3/8" D70 at 1.5 lb./ft.. I also use a 3/4" bridle with up to 25' leads. Of course my boat is a 41' Bristol cutter and weighs, supplied, 16.5 tons. I have remained firmly at anchor in 4.5 knot current that shifted 4 times a day, did not drag in winds topping 50 knots (that is 4 times the force of a 25 knot wind) and set it in rock, mud, sand, gravel, grass and weed. Chances are good that you might not need to cover that. A 25' boat on the Chesapeake would use considerably less. I would not choose a primary anchor under 20 lbs. though and would use (or at least carry) 25' of chain to add to the end of the rode. Rocna, Manson and others make smaller versions for small boat and day use. They work vastly better than older types but, in mud, with little current or wind, a 20 lb. rock will work.
windnrock is offline  
Sponsored Links
Advertisement
 
post #22 of 29 Old 07-11-2015
Member
 
mrmac's Avatar
 
Join Date: Jul 2013
Posts: 40
Thanks: 28
Thanked 2 Times in 1 Post
Rep Power: 0
 
Re: Anchor question

While you are pondering anchoring's seemingly infinite variables, recognize that increasing scope past a certain point has little/no benefit.

Using the calculator linked below, let A be the distance from the seabed to the chock and B be the length of your rode. Plug in some probable numbers to see for yourself. Eventually angle X, the angle of elevation, is little affected by an increase of rode.



Right Triangle Trig Calculator
mrmac is offline  
post #23 of 29 Old 07-11-2015
Junior Member
 
Join Date: Oct 2012
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Anchor question

I have used that type of anchor for years, and they are great...once you get them to the bottom. I found that by using chain, about the length of the boat and one size larger than the manufacturer recommends for your size boat, will help a lot in getting the anchor to the bottom. It will also help the anchor to set. What I found was that without the extra weight, the anchor tended to "fly" in the water if the boat was moving. I would recommend practicing, because the lightweight anchors can be a little more difficult to set, but they are great once they do. You probably have a great anchor.
CMKF is offline  
 
post #24 of 29 Old 07-11-2015
Senior Member
 
hpeer's Avatar
 
Join Date: May 2005
Location: Onboard
Posts: 1,646
Thanks: 19
Thanked 49 Times in 49 Posts
Rep Power: 15
 
Re: Anchor question

Quote:
Originally Posted by Lummox3077 View Post
Ok so as I posted , I just put a deposit on my first sailboat. I've been around power and bass boats since before I was born so I'm not unfamiliar with boats and boating. I am unfamiliar with the anchor on this new boat.. the seller claims it's a magnesium Danforth, Methinks it's probably aluminum. If it were steel I'd say it's a 15 pounder, this thing feels like 5. It does have about 6 feet of chain which is also really light and a little short IMO for a 23' boat.

I've always been under the impression anchors and their tackle should be heavy to stay on the bottom. I am in NJ where we have mud and sand and grass. Has anyone every used these tin foil anchors or just I just use it as a backup and go get a big piece of steel like I have in my other boats?
I grew up in Manahawkin. In the mid 60's I spent a lot of time clamming in Little Egg Harbor, just south of the causeway bridge to LBI. 14 to 16' boats. We used small danforths.

There were many days when the small, 10 lb ish, anchor just would not set. If the bottom was soft then fine. But if was medium to hard sand then I would have to force ably drive the anchor in by hand.

The fluke just did not have enough weight to penetrate.

So to answer yr question, it depends. Out of the time you will be fine. But if you are closer to the inlet, with a sandy bottom, you might have a challenge.
hpeer is online now  
post #25 of 29 Old 07-11-2015
Senior Member
 
pdqaltair's Avatar
 
Join Date: Nov 2008
Location: Deale, MD
Posts: 3,724
Thanks: 4
Thanked 131 Times in 129 Posts
Rep Power: 12
 
Re: Anchor question

Quote:
Originally Posted by Omatako View Post
I am probably just too dumb to understand the real meaning of that statement so let me test it.

My rudimentary definition of catenary is that it is the weight of the chain between the boat and the anchor which is lifted when the boat pulls back against the rode.

So if I'm anchored in 20 metres of water and I put down 100 metres of chain (5:1), it would have a lesser catenary effect than if I put down 140 metres of chain (7:1). The boat pulling back on the chain would want to straighten the chain, thereby lifting it - this is my understanding of "catenary".

And if I'm anchored in 3 metres of water and I put down 15 metres of chain, when the wind stiffens the boat will pull back and the chain will lift off the ground. My understanding of that is that it is also catenary.

And if I have a power boat that can be anchored in 1 metre of water and I put out 7 metres of chain, the boat pulls back, the chain tries to straighten and is lifted - this is also catenary.

To be sure, the catenary effect of 100 metres of chain is going to be far better than the catenary effect of 7 metres of chain but catenary is catenary.

The definition does not change with the depth of the water. At least I don't think it does. So the quoted statement should be that there is no (should probably be "little") catenary effect in shallow water.

Educate me.
Yes, agreed. However, in storm winds (50 knots) the load will be ~ a ton and I think we can all imagine that a chain with 2000 pounds tension is laser-straight. There are calculators on-line that will show that the deflection is only a few inches. The wind speed at which point this becomes true is certainly depth dependent, but the story always ends the same way in strong winds.

I like chain and I use all-chain. But my reasons are chafe and windlass handling. It does other good things. But at the same time it is terrible for energy absorption in many circumstances. I have the data to show (have posted it here before) that peak load can be 4x wind speed with all-chain.

For the OP--back on-thread--I would never use all-chain in this part of the world (mid-Atlantic US) in a small boat with no windlass. It is simply not the best answer, and I cruised a smaller boat for many years with a mixed rode. It was the right answer.

Writing full-time since 2014
Author--Rigging Modern Anchors

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

"Keeping a Cruising Boat for Peanuts"
"Faster Cruising for the Coastal Sailor"
"Singlehanded Sailing for the Coastal Sailor"

Last edited by pdqaltair; 07-11-2015 at 10:27 PM.
pdqaltair is offline  
post #26 of 29 Old 07-12-2015
Senior Member
 
Irunbird's Avatar
 
Join Date: Aug 2008
Location: Tampa, Fl
Posts: 347
Thanks: 12
Thanked 10 Times in 9 Posts
Rep Power: 12
 
Re: Anchor question

I almost hate to ask this, but I've been wondering about this myself.. We own a 30' lightweight boat (Olson 30- about 4200 lbs all up) and I think the anchor is a galvanized steel Danforth. I believe it weighs somewhere in the neighborhood of 12 lbs (it's not sitting in front of me, so this is from memory). Now that we live in Tampa (moved from Charleston) and I'm planning on cruising around and anchoring much of the west coast of Florida (and eventually in the keys), would I need any different setup? I have about 8 ft of chain and the rest is nylon, but scope should be easy if planning to anchor in the shallows of the coastline and tucked into rivers.

Any suggestions would be helpful-

Ray
Irunbird is offline  
post #27 of 29 Old 07-13-2015
Senior Member
 
JimsCAL's Avatar
 
Join Date: May 2007
Location: Glen Cove, NY
Posts: 4,563
Thanks: 5
Thanked 205 Times in 197 Posts
Rep Power: 13
 
Re: Anchor question

Quote:
Originally Posted by Irunbird View Post
I almost hate to ask this, but I've been wondering about this myself.. We own a 30' lightweight boat (Olson 30- about 4200 lbs all up) and I think the anchor is a galvanized steel Danforth. I believe it weighs somewhere in the neighborhood of 12 lbs (it's not sitting in front of me, so this is from memory). Now that we live in Tampa (moved from Charleston) and I'm planning on cruising around and anchoring much of the west coast of Florida (and eventually in the keys), would I need any different setup? I have about 8 ft of chain and the rest is nylon, but scope should be easy if planning to anchor in the shallows of the coastline and tucked into rivers.

Any suggestions would be helpful-

Ray
That's a marginal setup for regular use while cruising, but with the addition of some more chain (at least 25 feet total), will make a decent second anchor and rode for your boat. I would get a better anchor (like a Rocna, Manson Supreme, etc.) with chain and rode for your primary.
JimsCAL is online now  
The Following User Says Thank You to JimsCAL For This Useful Post:
Irunbird (07-13-2015)
post #28 of 29 Old 07-13-2015
Senior Member
 
rnixon's Avatar
 
Join Date: May 2013
Location: San Francisco Bay Area
Posts: 178
Thanks: 12
Thanked 8 Times in 8 Posts
Rep Power: 7
 
Re: Anchor question

Quote:
Originally Posted by windnrock View Post
This is a discussion that apparently will never end. Physics is governed by certain "laws". If I have 150' of 3/8' chain out at approximately 225 lb.(less 13% for steel in salt water or 196 lb.), even if the wind is howling and the chain pulled straight, the mass or weight of the chain remains unchanged and presses down both on the bow of the boat as well as the anchor. Because it is not a straight rod, it also, stated simply, exerts force inwards >< .
Yes, the tension in the rode exerts a force on the boat inwards along its length, and similarly, inward along its length at the anchor. It does not press down on the anchor, unless there is so little tension at the anchor end that it sags..
rnixon is offline  
post #29 of 29 Old 08-14-2015 Thread Starter
Member
 
Join Date: Jun 2015
Location: Southampton NJ
Posts: 31
Thanks: 1
Thanked 1 Time in 1 Post
Rep Power: 0
 
Re: Anchor question

Update.. I realize this post is a few weeks old, I just wanted to report that I have been sailing a couple times when work allowed. And.. I did anchor up for lunch with the little anchor one time. If anyone is familiar with Tice's Shoal in Barnegat Bay, it felt sandy and covered with eel grass. Well that little anchor holds.. period.. Figuring I'm new at the sailing thing and I had a little room to play, I decided to try and sail off the hook instead of using the outboard, well I pulled as much rode as I could by hand and still had about ten feet in the water pretty near vertical, and she was stuck firm. No problem, I'll clamber back 15' to the cockpit, raise a little sail and tug the anchor free from the bottom while manning the tiller, mainsheet, and anchor rode. Did I mention that little anchor has some bite? Well I suddenly became stretch Armstrong before common sense kicked in and I threw a loop over a jam cleat, popped the anchor free, hoisted the main, held the tiller between my legs and pulled the anchor in hand over fist so fast she was water skiing.

But I raised my anchor under sail without using the iron genny. It was a good day for a newbie.
MedSailor likes this.
Lummox3077 is offline  
The Following User Says Thank You to Lummox3077 For This Useful Post:
oysterman23 (08-16-2015)
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:
OR

Log-in











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 type question abrahamx Gear & Maintenance 57 09-15-2013 10:05 AM
Anchor Chain Question DulceSuerna General Discussion (sailing related) 26 11-07-2010 04:09 PM
Yet another anchor question. Has anyone seen/used an Oceane anchor? SVDistantStar Gear & Maintenance 2 08-28-2008 01:09 AM
Anchor rode question nk235 Seamanship & Navigation 29 08-06-2007 10:55 PM
Anchor question saltypat Gear & Maintenance 5 07-25-2007 09:35 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