Anchoring Basics

[Freestyle]

I left my Dutton's Seamanship book in my stateroom on the USS Lexington when they gonged me ashore to the civillian world twenty years ago. Now I am cruising full time and trying to pull things from memory. Here are some basic questions:

1. What is the recommended scope for a 43 foot boat using a full size (I dont know the number) Danforth with 10 feet of chain and 3/4 inch nylon line?

2. My swing circle appears to anger the sailboaters down here in the Keys. Can someone give me a step by step for a Bahamian Moor so I can cut this down?

3. Even if I do not Bahamian Moor, is putting both anchors out (above mentioned danforth and a smaller one with 12 feet of chain) helpful or hurtful and is there a right way to do it? (A guy in Key Weird lectured me that my anchors were working against one another when I swung a circle.

I have reached the point in middle age where I would rather ask questions and expose ignorance than wake up to the thud of a collision caused by guess work anchoring.

Thanks

Bruce

 

[Traveler 45C]

What did you do on the Lex before you got gonged? I served aboard Midway and Enterprise.

Scope is a function on water depth not length LOA. For your rode, a 7:1 scope will hold you fine. Water depth + bow freeboard X 7. Bring back any memories?

Bahamian Moor: Set your 1st anchor as usual, fade back an extra distance to allow you’re down current anchor to have proper scope, drop and set it. Adjust your position in between the two anchors and leave some slack in your down current rode. A weight attached to both rodes will keep them from fouling your running gear.

 

[MikeP]

The difficulty is that anchoring depends on a whole bunch of conditions. On a calm day when you are not leaving the boat, 4:1 scope might work OK. Overnight, or you are leaving the boat, I agree w/Traveler and wouldn't put out less than 7:1. Of course you also have to consider the tides - if you anchor at low tide in 10 feet of water with a 5:1 scope of 50 ft (measured from the waterline, not from the deck), you will have considerably less scope if the tide raises the level to, say, 16 feet. And, if the winds are fairly brisk, you would want more scope. Also, how good is the bottom and do you have the optimum anchor for the bottom's holding conditions.

An obvious reduction in scope can be obtained with all-chain. Until this season, I had no experience with all chain. But the 53 we purchased at the end of last year has an all-chain rode and a nylon/25ft chain rode. Now, after using it extensively, I am a total convert to all chain and never deploy the nylon/chain rode. The boat moves around far less with chain deployed than with nylon. Of course, if you don't have a windlass that can handle chain, there would be a substantial expense of a new windlass and several hundred feet of chain.

Increasing the length of chain on your rode would help as well - I'd suggest 25 feet which is what we used on our previous boat, a 36 footer.

 

[Traveler 45C]

In, “The Complete Book of Anchoring and Moorings” (I forget the authors name), it is recommended that the chain weight be at least as heavy as the anchor that is attached to it. If you’re using a Fortress, the chain weight should be as heavy as if you were using a steel anchor.

With an all chain rode, just remember to snub up with 3 strand nylon for shock absorption when the winds pickup. This will reduce the stress on the ground tackle and deck gear.

I highly recommend the book.

 

[Pascal]

7 to 1 is the "standard" scope for most boats.

you can get away with less scope (5:1, even 4:1) :
- calm conditions or not for the night
- more chain / all chain
- oversized anchor
- set it with more scope (7:1) then reduce it

don't forget to add tide and bow height to water depth...

on a heavy Hatt, i really dont see any reason not use all chain, or at least 100' which will be enough for most situations in the keys/florida. in normal conditions, even up to 30kts, i dont use snubbers. Many recommend as much chain as LOA... maybe... but i feel better with all chain.

you may want to check you anchor size to make sure it's adequate. go one size above what' s recommended for your boat size.

sailboters always complain... ...were they also complaingin about your generator?

I've never used a bahamian moor, never felt the need for it (i don't anchor overnight in strong currents), mostly out of concern of catching the running gear or stabilizers. weight shoudl help but between the 2 anchors and the weight it's much easier to find an no current anchorage!

putting a stern anchor will cut swinging but if the wind picks up and shift, you'll have a lot of windage and may end up dragging both... that would make a lot of sailboters angry.

in addition to fouling each other, using 2 anchors means it will take longer to leave if you start dragging or if someone start dragging into you...

i use all chain with a fortress 55. no problem... i recently had to use only 4:1 in mud (crowded harbor)... 15/20kts, it held fine but i didn't sleep as well as i normally do.

 

[Nonchalant1]

I completely agree - buy the "Complete Book of Anchoring and Mooring" by Earl Hinz. It's excellent.

Re: Bahamian mooring, above description is good, but be careful. The idea about anchoring in with others is to have non-overlapping swing circles which keeps everybody OK when the wind shifts. If you do a good bahamian or fore & aft anchoring job and everybody else is on 7:1 nylon rode, when the wind shifts they can move around a lot, and you don't, so they bump into you. If staying close to your original position is what you want, bahamian is fine, or better yet do a fore & aft anchor, which is done the same as bahamian but with one anchor from the bow and one from the stern. This prevents fouling your running gear and keeps you in one place a little better.

As a courtesy, maybe anchor first with as short a scope as conditions allow and then VHF call (or dinghy over to) the close boats and ask....just say you want ensure safe anchoring and wondered what type of anchoring the boats here are using so you can match up. Or ask how long their rode is so you can keep safe distance. More than half of sailboaters are friendly.

Doug

 

[spartonboat1]

Did the sailors complain about your metal halyards beating against your baseball bat aluminum masts in the wind overnight....oh, sorry, different issue...

 

[jim rosenthal]

No, they like that sound....it lets them know all the rigging is still there..