A small boat like my Hunter 26 isn’t set up to carry a very large anchor, so lots of scope is necessary (a danforth 14 lb comes standard). But, in a crowded anchorage where larger boats with all chain rode and, what must be an anchor off an old war ship, can be a problem when the wind changes direction. My boat (with scope) swings, theirs doesn’t. Was wondering if you think sliding another weight down the rope portion of the anchor rode would help? (ie. allow less scope) And, could I use my “lunch hook” anchor (danforth style 8 lb.) as the weight? Thanks
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Tom
Scope is scope
Your scope, with chain & nylon rode, should be the same as their scope, even with all chain rode. Those with all-chain can try to "get by" with less scope than you, as long as the wind in your anchorage remains low all night long. What you suggest adding to your system, in an attempt to limit your swinging room is called a "kellet" or "sentinel". I have used such a system on my boat, ABI makes an attachment that will slide down your rode (for sale at Sailnet) to which you can attach a weight and a retrieval line. I used a 10 lb. mushroom anchor as the weight. The ABI attachment is smooth and will resist chafing your rode. The big problem that I encountered using a kellet was from other boats who entered an anchorage after I was anchored. The other boats attempt to estimate the position of your anchor based on the angle that your rode enters the water and the water depth. Using a kellet will mask that, as the weight sometimes causes your rode to even hang straight down into the water on windless days (the weight is suspended off of the bottom). Other boats would sometimes anchor much closer to my boat than they normally might have had I not used a kellet (much too close for my comfort). I'd even been accused of not knowing how to anchor or what scope was (by powerboaters naturally). No one knew the terminology, kellet, sentinel, how it all works.... But there was a definite relationship between having anchored neighbors too close, and using the kellet. When I didn't use that system, I didn't have the problem nearly as often.
Your scope, with chain & nylon rode, should be the same as their scope, even with all chain rode. Those with all-chain can try to "get by" with less scope than you, as long as the wind in your anchorage remains low all night long. What you suggest adding to your system, in an attempt to limit your swinging room is called a "kellet" or "sentinel". I have used such a system on my boat, ABI makes an attachment that will slide down your rode (for sale at Sailnet) to which you can attach a weight and a retrieval line. I used a 10 lb. mushroom anchor as the weight. The ABI attachment is smooth and will resist chafing your rode. The big problem that I encountered using a kellet was from other boats who entered an anchorage after I was anchored. The other boats attempt to estimate the position of your anchor based on the angle that your rode enters the water and the water depth. Using a kellet will mask that, as the weight sometimes causes your rode to even hang straight down into the water on windless days (the weight is suspended off of the bottom). Other boats would sometimes anchor much closer to my boat than they normally might have had I not used a kellet (much too close for my comfort). I'd even been accused of not knowing how to anchor or what scope was (by powerboaters naturally). No one knew the terminology, kellet, sentinel, how it all works.... But there was a definite relationship between having anchored neighbors too close, and using the kellet. When I didn't use that system, I didn't have the problem nearly as often.
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Dave
Scope is not really scope
What you are interested in is to have as close to a horizontal pull on your anchor as possible. The load that is transmitted from your boat to the anchor is a tension load along the axis of the rode. A rope or chain can not be loaded in compression only tension. At the connection to the anchor you can draw what is called a free body diagram showing a force vector at the angle of pull of the rode on the anchor. Now a little trigonometry applied to the angle the rode makes with the anchor will convert that force vector into a horizontal and a vertical component. Any angle will result in a vertical component that is acting to pull your anchor out of the ground. The longer the rode the smaller the angle and the greater the horizontal component and the more the anchor wants to dig in along the angle of the anchor and stock. In the case of a danforth I think this is about 37.5 degrees but I'm not sure. Anyway chain allows a shorter scope by being heavier and to get the same angle on the anchor as rope you can use a shorter scope. The sentinel lowers the rope rode in the water to reduce the angle of the force vector also. Where you can have problems is in a very strong wind if the line goes totally taught with no catenary then the sentinel is no longer effective and the scope may then be insufficient. I always use 7 to 1 minimum scope and if the swinging room doesn't allow it then find another place to anchor. Now Block Island's great salt pond on Labor Day weekend will never allow a 7 to 1 scope swinging room SO I DON'T GO THERE THAT WEEKEND!!!! Dave
What you are interested in is to have as close to a horizontal pull on your anchor as possible. The load that is transmitted from your boat to the anchor is a tension load along the axis of the rode. A rope or chain can not be loaded in compression only tension. At the connection to the anchor you can draw what is called a free body diagram showing a force vector at the angle of pull of the rode on the anchor. Now a little trigonometry applied to the angle the rode makes with the anchor will convert that force vector into a horizontal and a vertical component. Any angle will result in a vertical component that is acting to pull your anchor out of the ground. The longer the rode the smaller the angle and the greater the horizontal component and the more the anchor wants to dig in along the angle of the anchor and stock. In the case of a danforth I think this is about 37.5 degrees but I'm not sure. Anyway chain allows a shorter scope by being heavier and to get the same angle on the anchor as rope you can use a shorter scope. The sentinel lowers the rope rode in the water to reduce the angle of the force vector also. Where you can have problems is in a very strong wind if the line goes totally taught with no catenary then the sentinel is no longer effective and the scope may then be insufficient. I always use 7 to 1 minimum scope and if the swinging room doesn't allow it then find another place to anchor. Now Block Island's great salt pond on Labor Day weekend will never allow a 7 to 1 scope swinging room SO I DON'T GO THERE THAT WEEKEND!!!! Dave
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Tom
Wind speed
Dave indirectly points out that there really is another dimension to desired scope, that being wind speed (and current, in some places like the NW). I use an all-chain rode on my existing boat, but I also use the same scope with all-chain that I'd use with my previous boat's chain/nylon rode. Granted, at the same windspeed, the catenary for all-chain will be greater than chain/nylon. However, wind speed is dynamic and not static, and we do get unforcasted nightime williwaws here in the islands. 7:1 is a fine scope to wish for and makes for great reading in Chapman's. Maybe that is possible on the East Coast, but with deep water, or deep water so close to shore in the NW, that is just not possible. The reel of nylon rode required would take up too much room down below.
Dave indirectly points out that there really is another dimension to desired scope, that being wind speed (and current, in some places like the NW). I use an all-chain rode on my existing boat, but I also use the same scope with all-chain that I'd use with my previous boat's chain/nylon rode. Granted, at the same windspeed, the catenary for all-chain will be greater than chain/nylon. However, wind speed is dynamic and not static, and we do get unforcasted nightime williwaws here in the islands. 7:1 is a fine scope to wish for and makes for great reading in Chapman's. Maybe that is possible on the East Coast, but with deep water, or deep water so close to shore in the NW, that is just not possible. The reel of nylon rode required would take up too much room down below.
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Dave
Scope Options
If the water is too deep to have the required amount of scope for safe anchoring (5:1 is the minimum I have ever heard) of 7:1 then my recommendation is to sell all your belongings and move to the east coast where most anchorages are about 10 to 20 feet deep and 7:1 is never limited by amount of line you can carry. But there is another option. That is to set more than one anchor. If you set tandom anchors or even three equally spaced anchors then the boat has less tendency to pull out the anchor as it swings. Another trick of the trade I always use is an anchor riding sail to minimize swing and keep the load steady on the anchor. So in a short scope situation, a sentinel, anchor riding sail and tandom anchors should do the trick. (you shouldn't really have to move to the east coast despite the rain). Best regards, dave
If the water is too deep to have the required amount of scope for safe anchoring (5:1 is the minimum I have ever heard) of 7:1 then my recommendation is to sell all your belongings and move to the east coast where most anchorages are about 10 to 20 feet deep and 7:1 is never limited by amount of line you can carry. But there is another option. That is to set more than one anchor. If you set tandom anchors or even three equally spaced anchors then the boat has less tendency to pull out the anchor as it swings. Another trick of the trade I always use is an anchor riding sail to minimize swing and keep the load steady on the anchor. So in a short scope situation, a sentinel, anchor riding sail and tandom anchors should do the trick. (you shouldn't really have to move to the east coast despite the rain). Best regards, dave
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Tom
Check out the recent thread...
...entitled "How much scope do you use..." Most people would say that they use 5:1 or less, be it nylon, chain, or a combination of each. That is, most people in the real world would admit this. How much one would use is entirely up to the mariner, his/her judgement and experience, and the local conditions. There is no hard and fast formula that is best for everyone or in every place and/or condition. Despite the challenges of anchoring in deep water, 13 foot tidal variations, and fast currents, the west coast provides enough natural beauty, fresh air, and wonderful cruising grounds for me.
...entitled "How much scope do you use..." Most people would say that they use 5:1 or less, be it nylon, chain, or a combination of each. That is, most people in the real world would admit this. How much one would use is entirely up to the mariner, his/her judgement and experience, and the local conditions. There is no hard and fast formula that is best for everyone or in every place and/or condition. Despite the challenges of anchoring in deep water, 13 foot tidal variations, and fast currents, the west coast provides enough natural beauty, fresh air, and wonderful cruising grounds for me.
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Don Alexander
Yes
On both of my last two boats and when in tight anchorages I have dangled the kedge anchor over the bow with enough scope to just lay on the bottom at high water. Stops all the sailing about over the main anchor too.
On both of my last two boats and when in tight anchorages I have dangled the kedge anchor over the bow with enough scope to just lay on the bottom at high water. Stops all the sailing about over the main anchor too.
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Jay Beery
swinging rights
We just came back from bareboating a small cat in the BVI. One night in Great Harbor. just off Foxys Bar, another cat dropped anchor damn near on mine! I politely informed him of the amount of chain I had out and asked him to pick up and move upwind 23-30 feet and re-anchor. There was plenty of room. After blowing me off as a know it all, I took great pleasure in making him move at O-dark-early the next morning to get off my anchor so I could pull it up!!!! This was my first charter as captain. And to tell you all the truth, I couldn't believe all the bone-headed moves I saw down there.
We just came back from bareboating a small cat in the BVI. One night in Great Harbor. just off Foxys Bar, another cat dropped anchor damn near on mine! I politely informed him of the amount of chain I had out and asked him to pick up and move upwind 23-30 feet and re-anchor. There was plenty of room. After blowing me off as a know it all, I took great pleasure in making him move at O-dark-early the next morning to get off my anchor so I could pull it up!!!! This was my first charter as captain. And to tell you all the truth, I couldn't believe all the bone-headed moves I saw down there.
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Tim King
weight for anchor
Hello Michael, A sentinal will help reduce swing but don't use another anchor. Murphys Law says it will foul in your tackle and you'll have a big mess on your hands. Sentinals are available at most chandleries and this is one situation where using the right tool will make a big difference. Tim
Hello Michael, A sentinal will help reduce swing but don't use another anchor. Murphys Law says it will foul in your tackle and you'll have a big mess on your hands. Sentinals are available at most chandleries and this is one situation where using the right tool will make a big difference. Tim
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Michael Bell
Thanks to all
...for the input. We do have a different situation here in the NW. Any of you that have been in the Desolation Sound area will attest to that. It’s not uncommon to drop anchor less than 100 feet from shore and pay out over 200 feet of line. Thankfully, it’s broken granite and snagging an anchor into a crevice is the only way to get hooked.
...for the input. We do have a different situation here in the NW. Any of you that have been in the Desolation Sound area will attest to that. It’s not uncommon to drop anchor less than 100 feet from shore and pay out over 200 feet of line. Thankfully, it’s broken granite and snagging an anchor into a crevice is the only way to get hooked.
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