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Preventing or reducing anchor swinging

28K views 60 replies 19 participants last post by  camaraderie 
#1 · (Edited)
UPDATE - POST #43 HAS MY COMPLETE TRIAL RESULTS AND SHOULD WORK ON (sail)BOATS 40' and UNDER I TESTED ANCHORS AND TECHNIQUES BOTH!!!

I didn't even think about this until the other night when I was out on the hook in 20ft of water and we had a huge wind storm come along pushing over 45 mph and gusting to 65.

Earlier in the night, the breeze was from the west, so I set my anchor and a 7:1 scope properly and went to bed. Well, at about 3AM we get these retardedly huge wind storms from out of nowhere, and I was woke up from a great sleep by the lid on the anchor locker slamming down on the deck and the sound of the rigging whistling. Not too fun, I think. I don my pfd and foulies over my boxer shorts and run upstairs to the cockpit.

I climbed out to the cockpit and turned on the gps and set the anchor drift alarm for 200 feet, thinking that if I busted that ring, it was slipping out and would need to be reset. I then rethought this idea because the line on the 7:1 was pulling strong, so I reset the alarm for a 100ft circle. I was clearly shooting left to right and back quickly on the gps screen, but not falling backwards. When I got to the far side of either swing, the boat would hang then she would sloooolwy creep over to leeward, then fly back to the other direction.

I went back to the bowsprit and dropped out another length of anchor rode to increase the line to over 220 feet according to my rode markers... This was out of sheer nervousness and when I am thinking of a semi-survival situation, I like to have to think I can do something else to help me stay safe. Remember, it was dark, I was dazed from being jostled from my sleep, cold, and now starting to get wet. Not the best of times on a boat, and why I was "fiddling" to try to help myself out. It's almost like if I'm productive during a storm or another problem, I can feel like I am doing something to better the situation so I do little tasks like re-check everything or so fotrh.

Well, I never slipped, but I was getting annoyed with how much the boat swings at anchor. I was all alone, so could not have someone to help me set up to hove or heave-to. I could not have time to start the engine, then run to the bowsprit and haul up the anchor before I was pushed the 1/2 mile to shore by the wind.

I was considering throwing out the para-anchor behind the boat to slow the creep-creep-creep-then fast swing to port then creep-creep fast swing to starboard garbage... is this a correct assumption? Can I put it out to slow this swinging, or should I use something else???

I really don't want to drop two anchors off the ship, I singlehand about 90% of the time and I need as little interruption to geting underway as fast as possible when conditions get worse than my anchor can hold. Is there something better I can drag or tow to reduce this? I keep hearing that people have tow-warps? What is this for and what are they?

Some details -

7800lbs, 30ft boat, full keel, 4 feet of freeboard, 1 foot of cabin over the deck, bare poles under anchor

rode is 10ft of chain, 400ft of 3 strand

12kg Scottish Bruce anchor. (nope it has never slipped...)

Winds often exceed 40mph in shallow (under 30 feet) water, so it gets VERY confused out there I'm confused too, should I just never sleep on the hook out there, and pay the slip fees, or is there a remedy?

Thanks,

Robert
 
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#2 · (Edited)
It may help to have more chain - 10 ft seems short. We have 200 feet of chain - but you should have at least enough to hit bottom. A double loop bridle on the anchor chain and a reefed mizzen will also help control swing - to an extent, or in your sloop rig, perhaps even a small staysail off the backstay.
 
#3 ·
I would recommend going up to at least 30' of chain. 10' is pretty short for a boat your size, but it also depends on the anchor. Certain designs, like the Fortress, set better with less chain...

To reduce the boat kiting, you might want to either install a bridle or try anchoring from the stern. Don Jordan, creator of the Series Drogue, has an interesting paper on anchoring from the stern, which you can read here.

Another, less radical, option is to add a line to pull the anchor rode off to the port or starboard quarter, so that you're not dead into the wind, but in the position that you would be in if you were hove to. This is recommended by the Pardeys IIRC.
 
#4 ·
Others have gone with a riding or anchor sail.
I am not sure, (because I don't use one,) what the limitations are as far as wind speed.

 
#5 ·
I have never done this myself, but if I was in those conditions I would try a small anchoring sail as described in this month’s issue of "DIY Boat Owner". It’s Issue #2 2007, page 41. Probably see it on line. They describe how to set the sail up to stop the very sway you describe. The anchor sail technique is also described in many other articles and books. Try a search for more info. Maybe you can find a set up done on a boat like yours.

Wayne
 
#6 ·
Are you sure the winds were 45mph-65mph? With a 7 to 1 three strand rode, you were awfully lucky not to drag. As others have mentioned, the amount of chain you have is so short I would actually discount it, unless you were running a Danforth or Fortress style anchor. With a rope rode like you have, I would normally overnight with 10 to 1 out and more for a storm. Outside of that, a riding sail or bridle would lessen the shifting (OK... I have nothing else to add). I would definitely get a lot more chain. That alone may decrease any "oscillations" you may have on the hook.
 
#7 · (Edited)
With a long nylon rode and gusty winds, you are gonna have a slingshot effect anyway as you can easily get a 20% stretch. A riding sail can help a bit as can a bridle on the bow or a central sampson post to keep the pull linear and in line with the keel. More chain may be desireable from a holding standpoint (depending on your anchor) but as long as the majority of your rode is nylon, you are going to have considerable stretch. I would not add chain to avoid swinging...only to provide more secure holding.
 
#8 ·
The problem with carrying too much chain, like 200 ft, is that the ship will be down by the bow and will tend to nod a lot. My 36 ft, 10 ton ship is noticeably bow-heavy with all that chain in the bow, and there really is no other place to put it. Maybe 50 ft of chain would be more manageable, and the rest rode. I know not.

I have not used the anchor for, like, 6 years, so maybe it's time to go back to lighter tackle.

The swinging is a matter of physics... the boat tries to pay off weather, then gets tugged back, to repeat the show the other side. Maybe a stern para-anchor would help to slow the swing.
 
#9 ·
My boat will hunt a lot at anchor even in light winds. I have used an achor sail for wind gusts of up to 35 knots. Even in these conditions, the boat tends to be much less "restless", although I have noticed a moment of heeling when the wind shifts direction.
 
#10 ·
Rockter--

Erring on the side of heavier with your ground tackle is rarely a mistake.
 
#12 ·
ok how about this - could I anchor off the stern, with a storm jib up front? which side is the storm stay sails trimmed to? Backed or "ready to go" like as if I were using it to provide propulsion?

Another thing I want to try is the bridle, anchored from the bow combined with a stay sail in the back, again same question, how should I trim it? (I do have a trysail I could use)
 
#13 ·
Those riding sails help substantially in reducing the over active swinging at anchor of some boat designs. They are designed to be dead flat, no camber and no drive - basically a weathercock. - not sure a storm jib would do the job.

The don't eliminate the swing, but they do reduce it and more importantly keep the surging at each end of the swing way down. Friends who winter in the Caribbean had a real problem with swinging, and the end of rode surge did in fact occasionally trip their substantial anchor in squalls.

We had a riding sail we never used and gave it to them. They report a reduced, but more importantly, a gentler swinging action and now use it every time they are on the hook.

Possible problems I can see with anchoring astern or on the quarter is you will tend to funnel the breeze into the boat - good on hot days but may be uncomfortable at times - and increased windage from a dodger.
 
#14 ·
In addition to the aerodynamic problem faster pointed out, most boats are not designed to deploy or retrieve an anchor effectively from the stern.

Your stern lacks an anchor pulpit and roller, there's no windlass and most likely improper cleat size/backers and chocks to carry the increased loads which created the swinging problem in the first place.
 
#21 ·
However, depending on the design of the boat, it may not swing if it is anchored from the stern. YMMV.
Your stern lacks an anchor pulpit and roller, there's no windlass and most likely improper cleat size/backers and chocks to carry the increased loads which created the swinging problem in the first place.
 
#23 ·
Already mentioned that back in post #3... ;)
ok so how about anchoring from the front with a line attached to the anchor rode on a block and I can attach to the aft of the boat and pull it in to "lean" the rode to one direction?

Will this help? See drawing.
 
#17 ·
Seems like a reasonable solution lancer. But, I wouldn't get as elaborate as using a block permanently connected to your rode. Seems like just another mechanical link which could fail.

A better design would be to simply use a chain hook, clipped to the anchor chain and attached to a 3-strand nylon rope. The bitter end of the rope would then be cleated, as shown in your drawing.
 
#18 ·
TB, I don't think he'll have chain to attach to at that point... it would be rope rode-to-rope.

Not sure I'd want to tie a knot along the rode for that. Better to prefab a bridle for the purpose and attach the rode to the mid point somehow.
 
#19 ·
I know his 10 feet of chain wouldn't work - he would need to increase it anyway. I first recommended that he add more chain and use a double bridle with a central chainhook.

We never swing at anchor, even while watching some boats around us acting like carnival rides. This could be due to our all-chain rode and double bridle . . . could also be we displace 9 tons. Either way, weight, bottom shape and rode triangulation all factor in preventing swing.
 
#20 ·
Lancer, you're describing an anchor bridle which is commonly used to point a boat into swells instead of wind. You got the right idea. Let out more scope than usual (about 25% more). Tie your bridle line on with a rolling hitch and lead back outside to a winch. Now adjust the rode and/or line to get the point you want. Don't worry about the rolling hitch - it will stay tight and still be easy to untie. Cheers.
 
#22 ·
I like Lancer28's solution.

I would tie a docking line to the anchor rode just outside the lifeline. Use a rolling hitch .http://www.animatedknots.com/rollinghitchboating/index.phpThen I would take the docking line back, outside the lifelines, and run it through a winch. I would then slowly let out some additional anchor rode, until the boat stops swinging. I imagine at this point it would look much like Lancer28's diagram.

Realize that you will have more aerodynamic drag, and therefore put more strain on your ground tackle. Make sure that it is up to the task.

When it comes time to depart, simply release the line through the winch, take in the anchor line to the knot. Untie and stow the dock line, then retreive the anchor.

Note that I have not tried this:eek: YMMV and all the usual disclaimers apply:rolleyes:

Ed
 
#24 ·
Ed-

While this will present more drag, it may actually put less strain on the ground tackle than your boat would if it was sailing from side-to-side as there isn't the shock loading that occurs when the boat gets to one ed of the swing... also, the force on the rode and anchor would be a steady constant force, rather than one varying and changing in direction constantly.
I like Lancer28's solution.

I would tie a docking line to the anchor rode just outside the lifeline. Use a rolling hitch .http://www.animatedknots.com/rollinghitchboating/index.phpThen I would take the docking line back, outside the lifelines, and run it through a winch. I would then slowly let out some additional anchor rode, until the boat stops swinging. I imagine at this point it would look much like Lancer28's diagram.

Realize that you will have more aerodynamic drag, and therefore put more strain on your ground tackle. Make sure that it is up to the task.

When it comes time to depart, simply release the line through the winch, take in the anchor line to the knot. Untie and stow the dock line, then retreive the anchor.

Note that I have not tried this:eek: YMMV and all the usual disclaimers apply:rolleyes:

Ed
 
#25 ·
'Dog - good point!
I forgot about the potential shock load from the swinging. It would seem that if the tackle can handle that, it should handle the increased drag.... But as you pointed out earlier;
Erring on the side of heavier with your ground tackle is rarely a mistake.
;)
 
#26 ·
I had a chance to re-measure my chain and nylon today when I was installing new distance markers.

I actually have 400' of nylon 3 strand and 12' of chain. This sounds like enough to handle this task.

I'm going to try the dock/mooring line with a rolling hitch on the rode and fed back to my winch. I will report back to let you know what happens.

I just discovered that my trysail is not properly hanked. It has some kind of track cars on it and not hanks for attaching to the backstay. I'll get that corrected this weekend and also report on that too. I am thinking that if I attach the trysail to the mast it will not be far enough back to act like the feathers on the arrow and provide some aerodynamic stability to the boat.

Thanks for all of everyone's advice, it sounds like I will start having some more comfortable nights sleeping in the bed and not in the cockpit waiting for an anchor alarm from the GPS. I will be back in a couple of days to let you know how it goes.
 
#27 ·
I had a chance to re-measure my chain and nylon today when I was installing new distance markers.

I actually have 400' of nylon 3 strand and 12' of chain. This sounds like enough to handle this task.
I would still recommend going up to 30' of chain.

I'm going to try the dock/mooring line with a rolling hitch on the rode and fed back to my winch. I will report back to let you know what happens.
Should be interesting...

I just discovered that my trysail is not properly hanked. It has some kind of track cars on it and not hanks for attaching to the backstay. I'll get that corrected this weekend and also report on that too. I am thinking that if I attach the trysail to the mast it will not be far enough back to act like the feathers on the arrow and provide some aerodynamic stability to the boat.
A storm trysail is designed to be used by going up the mast sail track...which is what the track cars are probably designed to fit. A riding sail is a totally different beast-with the best ones being effectively a diamond shaped sail with the luff of the sail along the center of the diamond and having two clews. This allows you to connect the two clews to the two aft corners of your boat and allow it to more effectively keep the boat headed into the wind.

Thanks for all of everyone's advice, it sounds like I will start having some more comfortable nights sleeping in the bed and not in the cockpit waiting for an anchor alarm from the GPS. I will be back in a couple of days to let you know how it goes.
Look forward for it.
 
#28 ·
We used that method to anchor alot when the wind didn't match the waves to stop rolling, but never to stop swinging, hadnt really needed to I guess. This was on a 65' 55ton sloop. Made it more comfortable for the creww when the divers where in the water.

It was also a method for gunships at anchor to change their feild of fire back in the day.
 
#29 ·
Here are the result from three of my tests this week: the anchoring from the stern wasn't kept all night, and I switched to the riding sail. There was too much wind coming in the boat, the rocking and rolling was as bad as just anchoring from the bow, but with an amount of reduced swinging.

The bridle was my favorite, it seemed quite stable. I used a mooring line, with a speed shackle through the eye splice and back to a winch to tighten it.

The Riding sail alone was't too impressive. The boat still skittered back and forth, just not as much. (Maybe 1/2 as much... it was dark and I couldn't tell too well.)

Sorry, I'm a Doctor, not an artist Jim... haha!

 
#30 ·
I'm hoping you weren't as close to being broadsides to the wind as your second illustration shows... should only be canted about 10-20˚, not much more than that, certainly not more than 45˚.
 
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