How do you decide how much anchor line

[Alpo]

Is there a rule of thumb - six times the depth to the bottom, or something like that - or what?

 

Story. They're out in the Gulf. The water is 20 foot deep. They drop anchor with 30 foot of chain and 120 foot of 3/4-inch nylon.

 

I thought that 150 foot of anchor line seemed a lot for a 20 foot bottom.

 

But I ain't a sailor.

[Still hand Bill]

Correct, 5 to 7 x water depth.  Chain length equal or greater than boat length. Chain is included in the 5-7x number.   So for 20 ft, you would need 100-140 ft.  

[Loophole LaRue, SASS #51438]

Alpo:

 

Although you'll hear different rules of thumb from different sources, 3:1 is an often used (and in my mind inadequate) scope ratio; 5:1 is safer, but I prefer 7:1.  Remember, you want the rode to form a curve, not a straight line; you want to maintain horizontal pull on the anchor so that it digs in; if not, you will pull the flukes up out of the bottom, and drag anchor.  You also have to consider the design of the boat, wind, current, sea conditions, and bottom conditions; when in doubt, add more scope

Also, you need to add the distance from the water surface to your bow chock (on the deck) to the "depth" before you make your length of scope calculation.

 

LL

[Cliff Hanger #3720LR]

The length of chain is to hold the rope down closer to the bottom so the strain on the anchor line does not lift the anchor shank up and bring the fluke up out of the sea bottom, loosing it's grip to hold.

 

I have had my anchor drag on the bottom because of heavy winds.

To stop this, I put a second anchor on the first anchors rope and dropped it.

The second anchor kept the first anchor chain on the bottom and stopped all dragging.

[Alpo]

50 minutes ago, Cliff Hanger #3720LR said:

lift the anchor shake up

Did you misspell shank? Because I can't find anything about an anchor shake. Except a beverage.

 

[Larsen E. Pettifogger, SASS #32933]

I use to just tie a rope to the anchor and throw it over the side.  If the anchor hit the bottom before the rope ran out everything was OK.  If not the boat would drift until the water got shallower.  No math involved.

[Tequila Shooter]

2 hours ago, Loophole LaRue, SASS #51438 said:

Alpo:

 

Although you'll hear different rules of thumb from different sources, 3:1 is an often used (and in my mind inadequate) scope ratio; 5:1 is safer, but I prefer 7:1.  Remember, you want the rode to form a curve, not a straight line; you want to maintain horizontal pull on the anchor so that it digs in; if not, you will pull the flukes up out of the bottom, and drag anchor.  You also have to consider the design of the boat, wind, current, sea conditions, and bottom conditions; when in doubt, add more scope

Also, you need to add the distance from the water surface to your bow chock (on the deck) to the "depth" before you make your length of scope calculation.

 

LL

 

In the Navy they set an anchor watch to report to the bridge how the anchor line is riding, talk about boring. 

[Henry T Harrison]

Less than twenty seconds to google the answer to satisfy your daily dose of attention question 

[Cliff Hanger #3720LR]

Alpo, thanks I corrected the misspelling.

[Texas Lizard]

4 hours ago, Loophole LaRue, SASS #51438 said:

Alpo:

 

Although you'll hear different rules of thumb from different sources, 3:1 is an often used (and in my mind inadequate) scope ratio; 5:1 is safer, but I prefer 7:1.  Remember, you want the rode to form a curve, not a straight line; you want to maintain horizontal pull on the anchor so that it digs in; if not, you will pull the flukes up out of the bottom, and drag anchor.  You also have to consider the design of the boat, wind, current, sea conditions, and bottom conditions; when in doubt, add more scope

Also, you need to add the distance from the water surface to your bow chock (on the deck) to the "depth" before you make your length of scope calculation.

 

LL

With all that I think I will stay on dry land and set the emergency....Nothing to think about....Works or it don't....

 

Texas Lizard

 

I am a dry land type....Don't like to feed the fish....

[Sedalia Dave]

3 hours ago, Tequila Shooter said:

 

In the Navy they set an anchor watch to report to the bridge how the anchor line is riding, talk about boring. 

 

Better than the Mail Buoy Watch. 

[Alpo]

1 hour ago, Cliff Hanger #3720LR said:

Alpo, thanks I corrected the misspelling.

Thought it might be a term I was unaware of. The first time I saw the term "anchor rode", I thought it was a typo of "anchor rope".

[Cliff Hanger #3720LR]

Having sailed and built sailboats, I am sure that when the sailors put names to the equipment used on boats, they were all drunk and slurred their words or just made up words.