ANCHORING

[Theis]

That story is interesting. However, apparently he still doesn't realize his mistakes. I have seen people with chain put down a limited scope and wondered what they were doing.

1. The water he said was 10-12 feet deep and he put down 75 feet of chain. However, his bow is probably 3 feet above the water, so the effective water depth is 13 -- 15 feet giving him a scope of about 5 to 1, the minimum. Add to that the three, perhaps five foot waves, and the effective depth becomes 15 to 20 feet, and he was down to 3:1 ratio - too little scope. It might also have been that the water, being driven up the Hudson also went up a couple feet. Lasltly, he didn't allow for the possibility that the anchor was on a shelf, and that between where he was and the shore, when the anchor started dragging, the bottom might have dropped a couple feet - let us say to 13-14 feet of water, further reducing the scope.

2. People with chain figure they need less scope than with line (he said 3:1), the theory being that the weight of the chain causes it to sag, so that at the anchor, where the scope is relevant, the scope is greater than the scope if the line were straight. That theory is false. In a big blow, particularly when supplemented with the force of waves, the chain can be as taut and straight as a nylon line. The weight of the chain concept is only relevant when there is no major blow or seas.

3. The disadvantage of chain compared to line is that it has no give. With chain, when the waves and wind hit the boat, and the chain is pulled taut, the jerk to pull the anchor out is a multiple of what it is with line because nylon line stretches. With line, a boat does not get jerked. What makes the chain so particularly dangerous is that if it is taut when the boat is at the bottom of the trough, the bow rising with an oncoming wave becomes almost a vertical force on the anchor. The whole floatation of the boat is pulling the anchor up out, not just the force of the wind and waves.

4. A scope of 5:1 is not adequate for a severe storm. A safe scope is 8:1.

For all the years he had been sailing, his experience is a tough way to learn about the details of anchoring, but I have seen the same presumptions/attitude in anchorages I have visited. That does not mean to say that I have not also had my problems.

[commanderpete]

[NOTE: This thread was spun off another one. Here is the story Theis was referring to].

http://www.searoom.com/paramour.htm


Anchors are designed to work with the pull on the shank of no more than 8 degrees above horizontal.

If the rode becomes taut in storm conditions, this angle can only be maintained with a scope of 7 to 1 or more.

In calmer conditions, the weight of an all-chain rode keeps the chain on the bottom and the pull horizontal. This allows for a shorter scope.

[Theis]

As for the anchor issue, do all anchors, CQR, Danforth, Fortress, Bruce, mud, etc. have the same 8% angle? I had thought my Danforths were 15%. What makes that angle so critical, and relatively independent of the holding ground (sand, mud, gravel, etc.)?

In the West catalog, they too mention 7:1, although my word is that 5:1 is generally good enough - unless there is a hurricane coming down the pipe. But then the problem is that the bottom is frequently not flat. Sand can have ridges with an up side and a down side. If you're on the up side, I guess 5:1 might be OK. On the down side, 7:1 might still be inadequate.

Does the 7:1 include a safety factor and 5:1 what it should be on a flat bottom without a safety factor? 7:1 is a lot of line if you're in 30 feet of water.

I did notice that the West Catalog recommends a snubber for anchor chain so that there is some give when the chain pulls taut. I wonder if our friend had one. The catalog also mentions that the depth is the water depth PLUS the distance to the deck.

[commanderpete]

Here is the link where I got that 8 degree figure.

http://www.irbs.com/lists/trawlerworld/0102/0160.html

It also touches on the use of a "kellet" or "sentinel."

As for me, I don't anchor out very often. During the day I'll just toss out the lunch hook. On the other hand, I have had alot of experience kedging off sandbars.

Still, there seems to be alot of discussion about the "best" type of anchor, and not enough attention paid to anchoring techniques such as properly setting the anchor and sufficient scope, etc.

[Theis]

Wow! Now I Understand why my confusion was not mine alone. The time I anchor out is overnight, generally. I do it because, as ageneral rule. it is either the only place to stay, or it is cheaper - But I guess it is sort of like wondering whether house doors should be locked. You roll over at night wondering if you reallly adequately checked to be sure the anchor had snugged up, have the wave patterns changed, are those waves coming from a different direction (where the the boat is fully exposed). and so forth. The only way to counter that and convince yourself to lighten up is to have some assurance, based on knowledge in the trade, that you are being conservative and have considered all the elements in setting an anchor.

With the Ariel's on one hand, our windage is minimal. The boat is low to the water. On the other hand, several hundred feet of line is very difficult handle or stow, and the weight of a couple hundred feet of chain impossible. Forget that. 6' of chain is about my maximum.

Thanks for the website.

[Mike Goodwin]

AH grasshopper!

Now you understand the double edge sword of the shallow Chesapeake Bay . When sailing it is a curse , but when anchoring at night there is always a cozy cove with 10 to 20 feet of water with a soft bottom that sets quick and holds tight (unless you are sitting on an oyster bar , as opposed to in an oyster bar getting tight ) .

When cruising the Bay I carry 10' of chain and 300' of line and never have had to use more than 150' ( there are some deep areas that the 300' would be needed if forced to anchor there )

[Theis]

Mike:

What size line, and what size/type of anchor do you carry? Last year for the first time I went from 150' to 350' and am glad I did it. The line is in two sections with a swivel joining the two if I want to combine them, so I don't have to drag the weight of 350 feet of line. I thought 350 feet was preposterous, but I guess not - but then I was thinking 5:1 scope was adequate. I don't know of anyone out here that carries that much line - at least in the 30' and under league.

[Mike Goodwin]

I have 3 strand nylon 1/2" ( which is one size larger than needed 3/8" [rule of thumb is 1/8" per 9' of boat LOA ] ) and 1/4" BBB chain .

For an anchor I have several "Danforth" style up to a 35H (major overkill for an Ariel ) , a 12H is more than enough for an Ariel and a 5H is a 'good weather or lunch hook ' for me .

Danforths are good for most of the Bay as we have not that much grass or rock , you may need a 20-30lb Bruce or CQR for the Lakes .

[Theis]

This is getting interesting. Where do you stor 300 ft. of line, 10ft. of chain and a 35 H (I assume that is 35#)? Do you always sail with a provisioning boat alongside with several young dudes to help you lift that to put in the water, and to take it out? Or do you do as others are want to do, have their wife raise the anchor?

This discussion has brought to my attention a real problem with my lunch anchor.

But before I discuss that, I have three "anchors": a 17# Danforth with 150' or 1/2" line, the bitter end having a thimble eye, a 9' para tech sea anchor with 200' or 1/2" line, and a 11# Danforth with 75' of 3/8", the bitter end also having a thimble eye. I carry 200 ' of 1/2: line which can be connected to either the 17# Danforth or to the sea anchor, using a stainless steel swivel shackle. I have anti chafing gear where the line passes through the chock.

The lunch anchor, has only 75 feet of 3/8" line. Figuring that the bow is 3' off the water, and 6' of line cross the deck and are tied to the cleat, and a 7:1 scope, that anchor is only good for 7' of water, without waves. So I'll be going to the XXX boat store, now combined with the XXXX boat store, when they have a sale, if they do any more, and getting 200' of that 3/8" stuff. The smaller anchor needs the scope more than the bigger anchor with the chain rode.

I use the lunch anchor for more than just a mid-day swim. At night I use it as a second anchor to control the swing of Solsken. With 350' of line out, the total swing of the boat can be over 1/10 mile. The lunch anchor limits the swing to half that, if it holds, and also serves as a second anchor to distribute the load.

Two questions:

1.Does the strength of nylon anchor line deteriorate with time? It is only minimallyexposed to the sun or light .

2. The end of the anchor line obviously goes to the cleat on the foredeck. However, where else is best for it be tied? The maststep? The shrouds? The stanchion bases? My concern is that the aluminum cleat, with both anchors attached, could break in a particularly viscious storm and then the ballgame would be over. But the problem with the maststep is that I would not like to see the anchor pull the mast step out. There are only two screws holding the wooden block mast step - certainly not built for forward stress.

[Mike Goodwin]

1st, the 35H has never been on the Ariel , I just have it off my old 38' .
The 25 & 12 go cruising and just the 12 for daysails .
Chain and line fit the forepeak area , rarely carry the 300' , as I have never needed more than 150' and usually about 70' is enough .
In good weather with a soft bottom , I'll put out 10' of chain and 30 or 40' of line in 10 or 15' of water . At night I'll let out more line .

Put a cleat on the bulkhead at the chainlocker , the bitter end is always attached there .

[Theis]

I take it you run your line through the deck plate into the forepeak area through the screw cap in the bow. I have elected not to do that, because of several problems. First, I keep several of the sails in the forepeak. Secondly, I don't want the seaweed/muck often not adequately cleaned off for one reason or another to be migrating down there. Thirdly, it is too much work taking the cap off (and the potential to lose it), and lastly, I am not convinced that I can prevent water from entering through the hole in a bad rainstorm, or if the bow gets pulled under a wave.

Rather, I keep both anchors and line forward in the starboard cockpit lazarette. The additional 200' of line I keep either in the forepeak locker or in the stern of the port lazarette (better). In rougher situations, I throw the anchor over the side from the cockpit, the line being tied at the bow.

So the bulkhead is not an alternative for me for tying the anchor. Are the forces on an anchor line with the Ariel sufficient to pull the maststep forward, or am I conjuring up ghosts?

[Mike Goodwin]

I installed a hawse in the foredeck for the anchor line . You're being too paranoid about burying the bow and shipping a bit of water .
With my setup , I hang the anchor aft on the stern rail with the line led outside the rails and just toss it over , "Emergency Brakes " .

[Mike Goodwin]

My 300' of 1/2" nylon weighs about 15 lbs and fits in a 5 gallon bucket . I dont understand the weight/space issue .
I keep my sails in a sail bag , so only the bag gets dirty .

[Theis]

Mike, you got me going this morning. I read your messages, and found the weight thing difficult to comprehend. I didn't want to be accused of exaggerating - after all, we are sailors, not like those fishermen that don't know right from wrong.

So I put on my old chesterfield over my jamies , wearing my fedora, the one with the flaps to cover my ears and my polarfleece slippers, and went out through the snow to the garage carrying a super accurate bathroom scale.

It was cold, about 0 F, with a Force 18 wind. The wind chill had to be below 150 degrees, and that is Celsius. Nothing was stirring. The tea in my cup froze as it was being transferred to my lips. But knowing I had to get an answer back, I continued notwithstanding the clear and present danger I faced.

Here is what I came up with, checked and rechecked. The weight of the lines was taken when dry and cold.

The 200 ft of 1/2 inch line, with the galvanized (not stainless) shackle is about 20#. I don't understand how your line could be half the weight of mine.

The 17# Danforth, with 6 ft of chain and about 150 feet of 1/2" line is about 30#.

The total would be about 50# dry, perhaps 55# wet. Further, it is bulky. You are probably right that the 150 or 200' could be put in a dry wall bucket (I use a bag instead).

Anyway, for this wimp here, the 50# to 55#, could be overwhelming for my wife, and could be difficult for me as well when added to the weight of the beer consumed. It might result in my deciding to use a dock for $20 for the night, rather than anchor out and row ashore - expensive decisions.

Incidentally, our mutual lunch anchors are about the same, and that is why I now realize that the 70 ft. of line is not really adequate, although my experience is that under pleasant weather conditions, it has worked adequately, unless there are weeds.

[Ed Ekers]

I don't have anything to offer to this thread. But My God how appreciative am I that we live in California. We went sailing/racing yesterday. It was around 65 degrees with a twelve knot breeze and we were complaining that it was "cold" while we were just sitting and waiting for the race to get started. .....ed