Cruising at anchor

We have 50' of chain on our CD-25. The boat is lightweight with considerable windage, so it sails around some at anchor. Regarding scope, we use more than 5:1 if any wind is forecast, usually using 7:1 to 10:1. In a tight anchorage, we see what everyone around us is doing before committing to more than one anchor, so we aren't swinging different from other boats. I guess we also do a Bahamian mooring (two lines off the bow in a V") a little different from most: I prefer to not attach those lines together, so either rode can be adjusted for length as the wind changes direction or speed.

We use a Delta as our primary, a danforth as our second anchor.

We got to experience some of that Florida norther at anchor stuff. Along with Brent and Dixie (Discovery), we were in a crowded anchorage in Boot Key Harbor, when authorities chased people in half the anchorage out, because of a plan to start installing mooring balls... in a few days. During a norther with winds gusting above 40 mph. The result: twice as many boats in half the space. Even with two anchors out, Wild Blue swung more at anchor than most of the other (bigger, heavier) boats... we had to use a shorter scope than I would have liked because of the crowded conditions. Fortunately, with our shallow draft, we could get closer to the mangroves than the other boats.

The downside: someone with a boat that looked like ours had been in the anchorage the week before - they drug anchor through the sea-grass and generally created havoc amongst the people anchoring there. And, of course, they all thought that was us. :disgust

During that particular blow, the winds were so nasty that they flipped our dinghy, putting our dinghy motor upside down in the salt water! The shuttle boat service in Boot Key Harbor had ceased running due to the weather, but gave us a ride to shore so we could get the dinghy motor attended to right away... with the understanding, "If you aren't back in an hour, you are on your own to get back to your boat." Understandable. Joan stayed on the boat to keep an eye on the anchoring. Brent went with me to the outboard shop. Another boater onshore gave us a ride to the shop, the shop mechanic gave us a ride back to the marina. The shuttle boat driver said, "This is the last run until the weather breaks!"

It was two days before the wind let up. We took turns on anchor watch, neither of us getting much sleep, not able to get to shore. Even with two anchors out, the boat swung around uncomfortably. Numerous boats in the anchorage drug. Being closest to shore, bow into the wind, we didn't have to be concerned about anyone dragging into us, but there were times when boats beside us swung close enough for concern.

Anchoring isn't a "fixed situation" that is an always. The situation changes with the weather. I haven't checked how much we "sailed" at anchor - interesting to see the distance covered in Roy & Dixie's original post on this thread.

Best wishes,
Jim B.
 
JamesTXSD":3t4vwvr8 said:
I prefer to not attach those lines together, so either rode can be adjusted for length as the wind changes direction or speed.
Click to expand...

Just to clarify how I did it (and this was on my first trip, so just getting a feel for the boat): Once things settled out and I got a feel for how the boat was going to ride, I used some small stuff and tied the two rodes together just forward of the bow roller, but in such a way that it could be easily/quickly undone or changed if necessary. (I don't yet have fairleads or any specific rode lead set up, so the rode was simply going out over the roller.) What this did was keep either rode from going up against the "ears" of the roller as the boat swung to the limit on either side. The rode (and me) were much happier.

In future I'll either set up fairleads or perhaps attach a snubber to the bow eye - not sure yet.
 
The above link is at:
http://www.goodoldboat.com/reader_services/articles/anchor.php
As I review these various schemes--two things jump out at me. You may restrict the distance the boat swings, but as you put side forces on the anchors--the holding power is reduced. Second, your boat can still go back and forth, but will cover less distance. We have tried all of the various tricks in C Dories, and with a shoal draft, basically no keel, and a lot of windage, the boats all ways seem to go back and forth. Also wind direction is rarely constant--it is often shifting a few degrees, and thus the wind comes on one side of the boat and then the other.
 
Keen observations Bob.
Seems to me the 60 degree set he illus. with the equidistant triangle is the best when possible. I had not given much thought to the anchor sailing behavior of our boats, thinking that is just what my boat does. But I really am appreciating the anchoring strategies.

A separate thought: Is it correct that a deeper draft boat though it may swing (anchor sail) as widely, would not go through as many cycles of swinging in a set time period if under the same forces and length of rode as our boats?

Tom
 
Yes the 120 degree set is often used in hurricane moorings. But in my own experience with the C Dory 25 in the Broughtons were we were having a lot of sailing with some strong winds, I tried the spring line off the anchor to an amidships cleat, two anchors at a number of different angles, a weight and a second anchor on one of the primary rodes. None of them stopped the sailing--but several techniques slowed it down a bit. Certainly all heavy chain, in mud will dampen the movement--as might a heavy enough Kellet--ours is only 30 lbs (heavy for a C Dory however) Even on a heavy mooring, I have had boats sail. We moved the heaviest mooring blocks at Two Harbors with our 35 ton ketch, as we sailed back and forth, even with a stern mooring. (There was some swell associated with that episode)

Deeper draft, heavier vessels do slower "sails", but there can be a lot of force when they come up and are stopped at one end of the swing. I have noticed different movement with fin keel, light displacement boasts, vs full keel heavy displacement boats, but both can sail.
 
To minimize (read not eliminate) your vessel 'hunting' at anchor in heavy wind, I have had some success using

1. More chain, increase scope

2. A bridle made with a secondary rode using a rolling hitch (Prusik knot) attached to the primary anchor rode to (a.) keep the bow to the wind or (b.) somewhat off the wind (in a "hove to" position). (a.) is cleated equally amidship to port and starboard cleats, (b.) cleated to bow cleat and stern cleat adjusted length and angle to comfort.

3. Stabilize helm amidship

4. Jerry rig an anchor sail aft amidship (easier on a sailboat)

5. Use a stern para-anchor to help reduce swing

Good luck out there.

Aye.
 
It it possible that apparent swing at anchor is sometimes the boat yawing side-to-side at the end of the rode with little actual swing over the ground?
 
I just came across this description of of forces applied in mooring for the Jordan Series Drogue.

http://www.jordanseriesdrogue.com/D_14.htm

I found most interesting the diagrams explaining those forces. While it is mostly concerned with sailing vessels, the principles are still the same. I'm trying to wrap my head around the idea of mooring stern into the wind.

Brian
 
Brian,

Stern to the wind mooring may be OK for a sailboat with a relatively tall stern. But not OK with a boat having a square stern and the usual cutout well for OB propulsion. His arguments about reduced yawing and sailing on anchor may be valid, but as others have indicated, there are ways to reduce sailing while keeping the bow into the wind and seas.
 
The large ocean going sail boats are designed to take seas on the stern, when moving slowly down wind. The Jordan Series Drogues use this principle. Most sailboats are displacement hulls, (many ULBD are flatter aft) and many are almost double ended at the stern--that is at the waterline is a fine entry, and less likely to be pushed around by the large waves, than a square flat stern. These boats develop a lot of buoyancy as the sides flare out toward the deck. We have taken large waves over the stern of sailboats which would fill the cockpit of a C Dory with water and cause serious damage. The C Dory depends on going the speed of the waves to prevent these seas from overtaking the boat and breaking into the boat.

At anchor in when the seas are not large, a small motor boat could be anchored to the stern, but if there are any seas, then it is dangerous, and a number have been swamped. (The NFL player lost off the West coast of Florida, trying to pull the anchor from the stern, rather than cutting the line; the boat capsized and one of the crew slipped off the bottom and drowned/hypothermia. The structure of a C Dory is mostly forward, where there is no lateral resistance under the water, thus it tends more to weathercock when moored by the stern.
 
colbysmith":w2inxtvg said:
I always thought the recommended scope for any serious holding was 7:1, or more.
Click to expand...

It is, but... a lot depends on where you are anchored, type of boat, who's around you, etc. More scope is always nice, from a pure holding perspective, but there are a number of reasons or situations where one might choose to put out less.

Some examples:

1) Windy but completely sheltered (no waves) anchorage.

Maybe it's a small cove, and windy but with no fetch (so no waves can build up). In this case 5:1 or 6:1 might be just fine. Waves put a lot more strain on the anchor (dragging) than just pure wind (until you get up to crazy amounts of wind).

2) You are in an anchorage with quite a few other boats, and they don't have out a ton of rode.

There is a concern about being the "odd boat" in an anchorage. Not that you want to follow the crowd in a stupid way (way to little scope), but when you have to coexist with others - and you are all swinging - sometimes it's just as (or more) important to "blend in" with the crowd and all swing together. So maybe you put out 5:1 (or leave if that's not enough).

And too, beyond a certain prudent amount, too much scope can be a pain for others (and potentially a problem for you). Say you pull into a calm cove and anchor in 20'. The forecast and holding are good, there is not a lot of fetch, and it's 4' from the water's surface to your anchor fairlead, so you put out 160' of rode, for a bit better than 6:1 scope. But, unbeknownst to you, the boat that was already there (not that you are crowding them; there is plenty of room for two boats) decided that if 7:1 was good, 10:1 would be even better, and put that much out. When he swings, he's going to clear the anchorage!

From a reverse angle: In bigger boats I had a "rule" to always put out around 90' of rode, no matter how shallow. In other words, in 8' of water I wasn't going to put out 60' of chain and call it 5:1 scope.

So... for me it comes down to "it depends." More scope is great in a "pure" geometry equation; but oftentimes there is more going on than just that.

Of course in the C-Dory you can anchor in 3' of water, so it's all different again :D
 
Since I started all this anchor discussion a lot of interesting information has been presented. I mentioned 5x1 scope, but I am not really sure of what it actually was. Here is how I actually determine what length of anchor rode to pay out on our personal boats. As I lower the anchor to the water, Dixie will have been steering as slowly as possible to the spot we have decided to anchor (determined by all the points discussed previously). When I am ready, I give a hand signal for her to go into reverse. After the boat begins to move aft, I begin to lower the anchor. As the anchor reaches the bottom, I keep only enough strain on the anchor rode as it is paying out to keep it laying out in a straight line. When I see a fair scope building, I hold back a little to cause the flukes to begin to dig in, then release the strain to allow the rode pay out and the short length of chain I use to fall back onto the bottom. I do this several times until I can tell the anchor has firmly set. I will also have been trying to keep the wind from blowing the bow too far around and Dixie will have been moving from reverse to idle depending on wind speed. After I can feel a good strain on the anchor, I will cleat the line down and Dixie will be signaled to put the engine in reverse and apply some power to set the anchor firmly, cause the line to begin to stretch noticeably, and the boat to cease any aft movement. When power is removed, the boat will actually spring forward on the line and I will feel the anchor is ready for happy hour. I leave the GPS map on a setting that will show my anchor swing full scale through the night.
 
One type of anchoring that seem to work for me to limit swing is - after deploying, setting and cleating off my primary anchor - I take my secondary, which is a 10pd. navy with 4' chain and drop it off the bow. After I feel it touch bottom, I let out about 6' more rode and cleat it off. The primary holds you to weather and the secondary deployed in this manner limits or dampens your swing. It will also complement the main somewhat. After they are both set I pull both lines down to the bow eye to increase scope angle. If we are anchoring close to shore I also have a 3pd. PWC slipring anchor. I have this on a 30' rode. This is one time I think it is OK to throw an anchor. :smilep I attach the bitter end to a stern eye. I hold the anchor and about half the rode coiled up in my right hand. The rest I coil up in my left hand - leaving room between to swing. I then throw the anchor hard towards shore(underhanded). Almost immediately I throw the other coils with my left hand. This then becomes my stern tie.

Practising this type off throw is good if you ever have to throw a long or heavy line to somebody on shore or to another boat for towing, etc.

Although I hope never to find out, I figure the 3pounder would make a good throwable anchor for kedging as well.

Another way to use 2 anchors for better holding is to join them with a short bridle then a single rode from the bridle to boat.

Navy anchors may not be as popular as some but I find they work well - if you get the 2 piece ones(where the shaft can be removed from the flukes). I find on these the shaft can rotate to form a very steep angle with the flukes - allowing them to start digging quickly on less scope. I also find they drop fast and straight without sailing or twisting the rode. Don't buy the ones that are heavily vinyl coated, sometimes this can limit the movement of the shaft.

A heavy anchor should never be deployed off the bow with limited scope if weather is expected. It can hold the bow down into waves resulting in "green" over the top. :shock: It will impede the boats ability to rise and move forward over the wave.

Regards, Rob
 
thataway":2sk33att said:
Yes the 120 degree set is often used in hurricane moorings. But in my own experience with the C Dory 25 in the Broughtons were we were having a lot of sailing with some strong winds, I tried the spring line off the anchor to an amidships cleat, two anchors at a number of different angles, a weight and a second anchor on one of the primary rodes. None of them stopped the sailing--but several techniques slowed it down a bit. Certainly all heavy chain, in mud will dampen the movement--as might a heavy enough Kellet--ours is only 30 lbs (heavy for a C Dory however) Even on a heavy mooring, I have had boats sail. We moved the heaviest mooring blocks at Two Harbors with our 35 ton ketch, as we sailed back and forth, even with a stern mooring. (There was some swell associated with that episode)

Deeper draft, heavier vessels do slower "sails", but there can be a lot of force when they come up and are stopped at one end of the swing. I have noticed different movement with fin keel, light displacement boasts, vs full keel heavy displacement boats, but both can sail.
Click to expand...

Bob, forgot to say thanks for posting the correct link to" Hooking... for a good nights sleep" back on pg.2, and the follow up comments to my question.

When you said Broughtons I assume you meant in B.C.. I have some fond memories camping and fishing there at the entrance to, I think it was called White Passage. We usually did a wall tent base camp but didn't set it up due to the good fortune of being able to use a private kayak shack in between their excursions. I owned a 15.5' Sorensen at the time. The fish police pulled up suddenly in an inflatable. My wifes' niece and and my kids were on the boat. We were catching Pinks and I had a five gallon bucket with the fish put in head first where you couldn't force another one in. Yes, it looked wonderfully strange, and yes they wanted a real close look at everything. Every T was crossed and I dotted and fish correctly identified, sized, etc. etc. I probably didn't get them all back in the bucket but I didn't get a ticket, Yea!

You said the 120 degree set is often used in hurricane moorings. Do you know why the 120 degree set would be preferred over the 60 degree set? If I am understanding the author correctly he thought the equilateral triangle of 60 degrees was best due to putting almost 50% less strain on each line.

Thank you and all, wishing the best this thanksgiving,

Tom
 
Tom,
The 120 degree set is used in hurricanes because as the eye passes over, the the wind will reverse direction by 180 degrees. With the 3 anchors set at 120 degrees apart, you will never be more than 60 degrees off a direct set on any one of the three anchors. The point being that even at 60 degrees off a direct set, most anchors will have excellent holding power. If you do a 180 reverse on many anchors, they will pull out; some will not reset.
 
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