[Rhodes22-list] Anchor Chain Question

Bill Effros bill at effros.com
Tue Mar 22 00:11:15 EST 2005


Mary Lou,

I'm sure I've heard the same things about anchoring that you've heard, 
but when I started to actually check them out, a lot of those things 
didn't make sense, and many of them seem contradictory.

Let's start with John's explanation, which is well written, and pretty 
typical.  In order to make his examples work, he's got to anchor in 30 
feet of water.  I have never anchored in 30 feet of water, nor have I 
ever paid out 200 feet of rode.  (When I first read explanations of 
anchoring like this I bought 300 feet of line on a single anchor rode, 
but most of it has never been in the water.)

In practice, I would be happy if I could anchor in 10 feet of water, pay 
out 70 feet of rode, + my 22 ft. boat = 92 feet x 2 = 184 feet...I would 
need a circle greater than 184 feet in diameter with no other boats 
encroaching to be sure we would not foul each other's rode or bump in 
the night.  (John's circle would be larger than a football field.)  I've 
never been in a busy anchorage where boats stayed a football field away 
from each other.

In fact, in most busy anchorages you are lucky to get a 100 foot 
circle.  22 feet of boat, 28 feet of rode, 7 foot depth, 4:1 scope.  If 
this is the way you are anchoring, then your 16 feet of chain represents 
more than 50% of the rode--however it weighs only around 10 lbs, and 
would not be sufficient to create a catenary shape between your bow and 
the anchor.  If you actually anchor in 30 feet of water, your 16 feet of 
chain would still weigh only 10 pounds, and could still not create a 
catenary between your bow and anchor.

When I look around my harbor at hundreds of anchored boats what I see 
are very short scopes, no catenary shape, a straight line between the 
anchor and the bow, no chain on the bottom, constant pressure on the 
flukes of the anchors, and very little drifting.

When I looked in the West catalog to find drawings of anchor lines with 
chain on the bottom I was surprised to see that they are no longer 
drawing anchor lines this way (see p. 725) -- it's a straight line from 
the anchor to the bow.

I think everyone should anchor in a manner that allows them to sleep in 
the night, but I find it interesting that so much of what we read turns 
out to be wrong in practice.  As Wally has mentioned, the biggest 
benefit of the all line rode is that it comes up clean.  It is much 
easier to handle and store, and it is light enough so that even a child 
can haul it on board.

Anchoring on coral is a frowned upon practice in most places that still 
have coral.   Danforth anchors are the wrong type to use on rocky 
bottoms.  Again, like Wally, I have never seen abrasion on my all line 
rode.  I don't think line abrasion is a valid reason to use chain.  I 
don't think either the chain or the line spends much time on the bottom.

As far as I can see, the real reason people use chain is that it is 
easier for the windlasses to pull up chain.  Since a lot of these boats 
have really heavy anchors--too heavy even for Roger--they need something 
to pull them up, and they need chain so the windlass can do its job.

I was surprised to find on our boats that all line rodes worked just as 
well as chain/rode combinations.

Bill Effros




The catenary concept

Mary Lou Troy wrote:

> Bill,
> I've always heard that the primary function of chain is to keep the 
> pull on the anchor low, to increase the catenary and to reduce shock 
> loads in all but the most extreme conditions (when a snubber is needed 
> as well). There's a better explanation of this than mine at 
> http://www.johnsboatstuff.com/Articles/anchor.htm
>
> Our Danforth holds better with 16 ft. of chain than it did with 8 ft. 
> of chain because the extra weight of the chain is keeping the 
> direction of pull on the shank low. In many places we anchor I now use 
> less scope because we are much closer to the needing the scope 
> required for an all chain rode. (thinking 3:1 all chain, calm 
> conditions; 5:1 chain/nylon rode, calm conditions; 7:1 chain/nylon 
> rode, more difficult conditions)
>
> Mary Lou
> 1991 R22 Fretless
> Ft. Washington, PA / Swan Creek, MD
>
> At 09:30 AM 3/19/2005 -0500, you wrote:
>
>> Bill,
>>
>> As I understand the function of chain, its primary purpose is to 
>> prevent line abrasion on the bottom.  If you don't have a rough 
>> bottom you really don't need chain.  As soon as you set a Danford 
>> type anchor you have pulled the chain off the bottom, and the chain 
>> and line should stay off the bottom, putting all the pressure on the 
>> anchor flukes and causing them to dig strongly into the bottom.
>> If you have sufficient scope, the pressure on the anchor is 
>> horizontal within the design specifications, and it should reset 
>> itself as needed if the boat slowly swings around it due to wind or 
>> current shifts.  When you are ready to retrieve it, you move the boat 
>> over the anchor and pull vertically, and the anchor releases.  (You 
>> can pull the boat over the anchor by hauling in the line, but it's 
>> much easier to motor over, and pull just line straight up until you 
>> get to the anchor, which in our case should weigh less than 10 lbs.)  
>> The beauty of the Fortress anchors is that they are both lighter and 
>> stronger than conventional anchors.
>>
>> Bill Effros
>>
>>
>>
>> William E. Wickman wrote:
>>
>>> You are right Wally.  It is all mud and clay with the occasional 
>>> rock cropping here.  I think I may cut my 20 ft chain in half and 
>>> carry the resulting pair of 10 ft lengths for use when I go to the 
>>> coast.
>>> Bill W.
>>> --------------------------
>>>
>>>
>>>
>>>
>>> ----- Original Message -----
>>> From: rhodes22-list-bounces
>>> Sent: 03/19/2005 06:57 AM
>>> To: rhodes22-list at rhodes22.org
>>> Subject: Re: [Rhodes22-list] Anchor Chain Question
>>>
>>> Bill,
>>>
>>> I agree with Bill here. I started out using about 8 feet of chain. 
>>> For my conditions I quickly found out that I don't need any chain. I 
>>> anchors in fairly shallow coves with red clay bottom. It has never 
>>> been a problem. The chain seemed like extra hassle and weight. 
>>> Everyone told me this was going to be a big problem. It has worked 
>>> just fine and I spend a bunch of nights anchored. I would guess your 
>>> conditions up river are much the same. If you plan on towing your 
>>> boat to the coast I would suggest chain but don't see any need on 
>>> the river.
>>>
>>> Wally.
>>>
>>>> From: Bill Effros <bill at effros.com>
>>>> Reply-To: The Rhodes 22 mail list <rhodes22-list at rhodes22.org>
>>>> To: The Rhodes 22 mail list <rhodes22-list at rhodes22.org>
>>>> Subject: Re: [Rhodes22-list] Anchor Chain Question
>>>> Date: Mon, 14 Mar 2005 19:04:01 -0500
>>>>
>>>> Bill,
>>>>
>>>> I've got the Fortress FX11, and I think it's a terrific anchor.  I 
>>>> also have the smallest Guardian anchor, which I store in a pouch, 
>>>> unassembled, and I've been very happy with that one also.
>>>>
>>>> I think those people know a lot about anchors, and I would be 
>>>> inclined to follow their recommendations.
>>>>
>>>> I have several lines with differing amounts of chain on each, and 
>>>> several with no chain at all.  I find I always go for the no chain 
>>>> at all, because I've never had any trouble with it, and it's so 
>>>> much easier to handle.
>>>>
>>>> The trick to anchoring (as with so many other things) is practice.
>>>> Try setting your anchor when it's not critical.  See if you have 
>>>> enough navigation skill to be able to determine if your anchor is 
>>>> dragging.
>>>>
>>>> When it's really blowing you shouldn't be on our boats in the first 
>>>> place.  Anchoring and praying is not the answer.  If you are 
>>>> trapped in a situation like this, and can't get to shore, head for 
>>>> open water and heave-to.  Practice heaving-to, too.  Work with the 
>>>> elements, not against them.
>>>>
>>>> The guy who developed those anchors recommends setting 2 at 180 
>>>> degrees apart and tying both off on the bow.  Then neither one will 
>>>> have to reset if current or wind shifts.  Differing lengths of 
>>>> chain will  not matter, longer scope can be set because the boat 
>>>> will rotate in a much smaller arc relative to other boats.
>>>>
>>>> Avoid anchor overkill.  That goes for the chain, too.
>>>>
>>>> Bill Effros
>>>>
>>>>
>>>>
>>>>
>>>> William E. Wickman wrote:
>>>>
>>>>> I just got my nifty Fortress FX7 anchor.  The instructions that 
>>>>> came with
>>>>> the anchor said to use a short length of anchor chain (6 feet of 
>>>>> chain if
>>>>> anchoring in 25' of water or less, and add another 6 feet of chain 
>>>>> for each
>>>>> additional 25' of depth).  Their claim is that chain anchor rodes 
>>>>> lack the
>>>>> shock absorbancy of nylon rope when the wind increases.  This 
>>>>> advice runs
>>>>> contrary to what I have been reading in the Rhodes FAQ that most 
>>>>> of you are
>>>>> using around 20 feet of chain.  So, does the Fortress require less 
>>>>> chain
>>>>> because it is so light?  What gives?  I presume that these anchor 
>>>>> guys know
>>>>> what they are talking about, but...
>>>>>
>>>>> Also, since I have 20 feet of chain that I use with my gbi anchor, 
>>>>> what are
>>>>> the dynamics of using shorter chain on a second anchor when 
>>>>> setting two
>>>>> anchors?  Does it really matter?
>>>>>
>>>>> B. Wickman
>>>>>
>>>>> __________________________________________________
>>>>> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
>>>>>
>>>>>
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>>>
>>>
>>>
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>
>
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