[Rhodes22-list] Anchor Chain Question

[Mary Lou Troy]

Bill.
A few more thoughts. You've raised some very practical points beyond the 
theory. I've put a few practical observations below from our 10 years of 
experience anchoring on the Chesapeake. These points are probably not 
"generalizable" (I can't believe my spellchecker accepted that) beyond 
anchoring in a mud bottom in mostly shallow water.

>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.)

We've only anchored in 25 feet of water once. It was notoriously bad 
holding ground so we put out most of our 200 feet of rode. There are a few 
places on the Bay where you get to anchor that deep. We are usually 
anchoring in 5 - 6 feet of water mid-tide. Tidal range on our part of the 
bay is usually around a foot.

>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.

We also routinely anchor in crowded anchorages. Even in 5 feet of water we 
sometimes do not get 142 feet (5 feet of water + 2 feet of freeboard x 7 = 
49+ 22 feet of boat = 71 x 2) between boats. Fortunately most boats swing 
with the tidal currents and you don't need that kind of distance. If it's 
windy enough to overcome the tidal currents most boats swing with the wind 
- same effect. We try to have enough distance to allow for variations in 
how boats swing.

>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.

In reality, most of our 16 feet of chain ends up flat on the bottom. I see 
the muddy evidence every morning. Catenary effects would only come into 
play as the wind picks up. After a particularly windy night we will have a 
lot of mud embedded in the chain - mud that helped us stay put. After a 
35-40 knot t-storm I was glad to see all that mud on the chain the next 
morning. We rode that one out with the engine running in case we needed it 
to take the strain off the anchor. Fortunately we didn't ever need to put 
it in gear but the pop-top enclosure and the bimini create a frightful 
amount of windage in a storm.

>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.

Do boats in your harbors generally turn with the wind or the tide? I expect 
your conditions are routinely more extreme. We rarely see a straight line 
between the anchor and the bow. We sometimes see a boat with all chain 
where the chain drops straight from the bow to the bottom. We know he 
didn't set his anchor there because we watched. Having spend many a minute 
watching the rode as our boat swings at anchor, I am certain that the 
pressure on the flukes is not constant. Having hauled many a muddy anchor 
and chain in the morning, I know that the chain spent a lot of time digging 
in the mud - it wouldn't do that if there was a straight line between the 
bow and the anchor. The Chesapeake waters are not clear enough to see the 
anchor even in 5 feet so I have to go by other evidence.

>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.

I don't want my anchor and chain to be clean. I want it dug in so that the 
chain is part of the system that holds the boat in place. If I were 
anchoring for lunch I might consider an anchor with no chain but most of 
our anchoring is overnight - and we have two people on board - one to man 
the tiller and motor - one to haul anchor and wash down the chain and rode. 
If we were single handing we'd be setting and/or stowing anchors differently.

>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.

My only experience is with the Danforth. We have yet to find a rocky bottom 
on the Chesapeake. We'd have to learn all over again somewhere else. Our 
chain spends a lot of time on the bottom. When we had the shorter chain the 
first 3 or four feet of rode where it was attached to the chain would 
occasionally have a lot of mud as well.

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

It's interesting to hear your experiences and observations because they are 
so different from mine. I'll file them away in case we ever come sailing on 
Long Island Sound. I've forgotten - which anchor do you routinely use?

Mary Lou