Swing on the hook

Hi All,


We are just starting to anchor and I'm reading all I can about the subject. We've practiced and know our equipment (300' 5/16 chain) with a Bruce.
I found this big algebraic formula for calculating "swing". What do you do to calculate, guesstimate etc. for swing when you go into an anchorage that has other boats? We're going out this weekend for our first overnight on the hook... which will include 2 tides changes or more depending on how long we stay.


Thanks - Dave

All boats swing differently, but the pattern is the same. Tide and wind will in general keep all boats down current/wind including the other ones in your anchorage.

My rule of thumb is to stay away from others. Few things are as irritating than being in a anchorage and looking out to find another boat 50’ away.

Read the book by Earl Hinz; Complete Book of Anchoring and Mooring.

Definitive bible on the subject of anchoring.

In steady winds with no current, boats will swing back and forth roughly 30 degrees side to side of the wind.

But with moderate winds and a tide change building to a fairly strong current, boats can go anywhere. I have gently bumped into boats several times over the years and it was always in that situation- most recently at the anchorage in front of Fernandina Beach and twice at the anchorage off of the CG station in Cape May.

David

syjos said:

Read the book by Earl Hinz; Complete Book of Anchoring and Mooring.

Definitive bible on the subject of anchoring.

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Sailboats with deep keels are pushed around by currents and powerboats more so by wind, so they can swing differently.

A large sailboat anchored near us after dark once, and woke us up later by knocking on our hull. They suggested we should move. I said no. It was a stalemate, so we both shortened our rodes (it was a calm night).

The Hinz book confirmed my suspicions: if there are any issues, the last boat in is the first one out.

Check out handheld rangefinders...better at estimating distance over water than I'll ever be!

Be aware of the currents where you will be anchoring. I eyeball everything which means I'm about right half the time. Try to get a sense of where your anchor is relative to your boat. That will tell you where you are likely to be when the tide changes.


Keep in mind that not everyone around you will have the same amount and type of rode out. This means you will swing differently. Try to account for that.


Where are you headed this weekend?

You can always set your radar to .25 rings and keep other anchored boats outside if that if you can.

Some people drop a stern anchor in crowded anchorages.

Also , depending on the boat, some people nudge up onto the shore. Run an anchor line up to a tree or a rock and you won't go anywhere. (watch for tides)

But the best solution is to find a less used anchorage.

pete

We are really lousy at estimating distances. I start out by assuming everyone is on 7-1 scope; on our boat, 5-1 was usually ample in non-storm conditions. If at all possible we try to anchor away from (outside of) the crowd that exists when we arrive. As Menzies suggests, we double checked using radar, and monitoring the motion of the group as current / wind shifted. Sometimes we might go around to the surrounding boats just to say hi and invite them to cocktail hour on our boat, and while we were at it ask how much scope they had out. We've made some very good friends over the years that way.

Keep your distance from others until you learn how your boat behaves. Your boat may (probably) tack back and forth. It may not and stay arrow straight, but others may tack into you. In very light winds your boat may swing around the anchor in the opposite rotation than the other boats. Current can affect your boat different than the others.
Read your windlass manual to see if you must use a snubber, bridle, or chain locking device to unload the windlass.

Some suggestions. Get a range finder. Inexpensive and they give accurate distances with no fuss or muss. You could use your radar, but the range finder will tell you quickly within a foot or so.
The worst time to anchor in a crowded anchorage is in "no wind or current". You can't tell where anyone's anchor is located or how they are lying to it. Give extra space under these conditions if possible.

So assuming a decent wind or current, the boats' anchors will be in front of them somewhere. Once you know what depth you will be anchoring in, you can figure out your swing room from your scope. So for example, in 10 feet of water with a scope of 5 to 1, you will swing approx. 50 feet in any direction from your anchor (50 foot radius plus your boat length). Ideally then, don't drop your anchor any closer than 50 feet (plus your boat length) (better 100 feet so in theory your circles don't overlap) to another boat. This is a starting point, but often people will come in after you and anchor in between you and another boat, taking up some of the "room" you left.

As Murray stated, the last boat in is the one that is supposed to move if a problem is expected or develops. When a boat comes in and anchors too close, I take photos, note the time and distance measurements and put it into my log, where I have already noted my time of arrival, depth, scope, etc. just in case of an insurance claim (never needed it yet) . In most cases, people coming in after you will move if asked, especially when told how far away they actually are (how close).
Lay your anchor down at the spot you have determined is good, and when the anchor is on the bottom, slowly back up while laying out your rode. Once your have reached the necessary scope, "set your anchor" by applying reverse throttle to ensure it will hold. Depending on your boat and HP, idle may be enough or part throttle. I am usually happy when my chain rode goes totally taunt and judging by our surroundings we are no longer moving. When the boat is put into neutral, it will move forward, which is another good indicator that you are adequately set.
Don't forget to use a bridle or "snubber" to take the load off the windlass even when "setting".
In a windy crowded anchorage, motor up behind a boat, keeping the correct distance side to side from other boats, and drop your anchor at least "half your scope" back. The boat you are behind should be at or near the end of their scope under those conditions. You will need a minimum of 2.5 times your scope between boats (fore and aft) of where you want to anchor when windy (more would be better).
Better yet, find an anchorage with lots of room.
Some good info from others already. We try for a 5 to 1 scope (unless big winds are expected) but sometimes have to settle for less (never less than 3 to1 for my comfort).
Edit: Always calculate scope for high tide and never anchor in a spot that has less than your boat's draft at low tide We can have some large tidal swings in our area.

Pete Meisinger said:

Some people drop a stern anchor in crowded anchorages.

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While this is true, some people also park across multiple parking spaces and in handicapped spots without tags.

Unless everyone else is also anchoring with a stern anchor, or you are against the shore, this becomes an issue. When you do this in the middle of an anchorage and nobody else is using a stern anchor, then when the wind and tide shifts, they stay in place and everyone else around them swings around their radius.

this causes a lot of issues and forces everyone else around them to toss out stern anchors. Now none of us get the breeze in our hatches.....THANKS!!!

The best thing to do is do what everyone else is doing. Ask the boat behind you how much line they have out, and make sure to drop behind the transom of the boat in front of you. This will ensure that when everyone swings, there is room.

The below photo shows the ideal separation distance.

You'll get a feel for it. One of the most difficult things is that local customs often dictate how this will play out. For example, it is rare here in the PNW for boaters to put out as much scope as many wish. My standard is 5:1 in normal weather and normal holding conditions, but that will get me into trouble swinging into the neighbors in many anchorages, where 3:1 or even 2:1 seem to be most common. We've learned that adjustments may be needed, up to and including weighing anchor and moving farther away from folks who don't seem to understand what's going on. I'd rather do that than be fending off other boats at 2 am. It does get uncomfortable at times when you're just distanced perfectly from the neighbors and some lunkhead plops down right in the middle, but I'd rather call their attention to the concern and risk prickly feelings than feel the big CLUNK in the middle of the night.

Having an anchor watch app on your phone or tablet is a wonderful way to really learn how your boat swings and what scope and tidal range do to influence the boat's excursions. Have a good spotlight or flashlight at the ready to help you sort out what's happening after dark when the tide turns.

Read up on the Bahama Mooring method of anchoring , no real swing perfect for a crowded anchorage.

I found it better to snub off one side only and a bit back from the bow. That way there was asymmetric loading from the wind and I didn’t sail around as much. But my boat was an aft pilot house style so it tended to ride better anyway.

FF said:

Read up on the Bahama Mooring method of anchoring , no real swing perfect for a crowded anchorage.

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This is a recipe for disaster if you are the only one who isn’t swinging with the current. Everyone else will swing and you won’t and they will swing into you.
Also having two widely separated anchors and rodes will almost guarantee that some one will lay their rode across yours. What happens if you want to leave before them?

Woodland Hills said:

This is a recipe for disaster if you are the only one who isn’t swinging with the current. Everyone else will swing and you won’t and they will swing into you.

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Agreed!! This is just about as bad as using a stern anchor in the middle of an anchorage. The reason I'm vehemently pushing back is you guys are giving advise to a new boater, who will accept this as standard practice, as will anyone else who finds this post for years to come.

The golden rule is 'Do as Everyone Else is Doing'. If everyone is Bahama moored, then Bahama moor. If everyone is using stern anchors, then use a stern anchor. If everyone is on a single bower, then PLEASE do that!!

Ina tight anchorage, it is very likely that as you rotate around 180 degrees, you will be in the spot of the boat previously in front of you, and the boat behind you will not be in front of you. If you don't move, one of them will now be feet away if not hitting you.

Doing contrary to what everyone else is doing, or what is commonly practiced in that area is obnoxious. If you don't know gues (HINT: single bow anchor only is the most common unless swinging over a shoal, shallow, shore or channel will occur).

Shrew said:

Agreed!! This is just about as bad as using a stern anchor in the middle of an anchorage. The reason I'm vehemently pushing back is you guys are giving advise to a new boater, who will accept this as standard practice, as will anyone else who finds this post for years to come.

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I couldn't agree more but don't limit that remark to just anchoring! There are numerous posts from time to time on various topics that are wrong in my opinion.

Can I also add: don’t waste your time getting the gear and learning to Bahamian moor. Just get a modern anchor that will reset as the tide or current changes. The Bahamian moor was just a kludgy work-around due to the fact that older anchors really sucked.

Pete Meisinger said:

Some people drop a stern anchor in crowded anchorages.

Also , depending on the boat, some people nudge up onto the shore. Run an anchor line up to a tree or a rock and you won't go anywhere. (watch for tides)

But the best solution is to find a less used anchorage.

pete

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That creates more problems than it solves most of the time.

Anchorages can accommodate a maximum number of boats if everybody anchors the same way. Everyone say at 4-1 w 150’ of rode out. Or if more room is needed 3-1 and less rode out. Then they all swing the same and there will be only very small differences in boat positions.
The in comes a sailboat and anchors in the middle of the bay at 7-1 and 300’ of nylon rode out. Next comes a big troller w a huge ForFjord, some studded chain and a whole lot of lesser chain (still heavy).
The fishboat basically dosn’t move all night and the sailboat is “all over the place”. It’s not a question of who’s right (the sailboat) but how all can spend the night safely.
The sailboat can shorten scope considerably if it’s good weather and the fishboat can add scope but that still won’t get the fishboat to move w the other boats.

But if someone comes in and anchors using a stern anchor it will almost gaurentee that boats will bump and rodes possibly tangle.

The name of the game is to anchor as much as possible like the other boats. Safety is the bottom line .. not correctness. Stern anchoring will only work if everybody else stern anchors too.

Just want to thank Post #12 by firehoser75, great starting guidelines.

Again, our preference is always to be outside of the pack if anyway possible. Then as others come in around you, if you are on the boat, let them know what scope you have out. Or do so if you can as you return to the boat. In general, boaters are very good at cooperating for everyone's sake.

"Again, our preference is always to be outside of the pack if anyway possible."
'
When I started sail cruising in New England circa '58 there were far more yacht clubs , each claimed the closest water in front of the club as their! mooring field.

This usually left the far away frequently crappy holding ground for others.

I soon learned to observe the mooring field very closely , and noted that the further out a mooring was the larger spaces were. At the side or end of the moorings there was always space for another boat.

The YC launch drivers were happy to pick one up , unhappy with the folks in the middle of the bay that needed 1/4 mile of clear space per boat.

I did get in the habit of using an anchor ball , as old mooring areas can be foul with old anchor gear.

Yacht Clubs are mostly a long gone breed , but towns were happy to decide they control all the water they can see and charge for a "town"mooring. (Sag Harbor LI)

Even if the town has no moorings they will petition the Coasties for a special anchorage area , and no you can't anchor there , come to their dock for $3 to $5 a foot

I have found the Bahamas type moor to easily fit in most anchorages , and easy to live with.

3-1 scope that others seem to enjoy scares the heck out of me as most thunder storms can have blustery winds..

FF said:

3-1 scope scares the heck out of me that others seem to enjoy.

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To me, it depends on where I am, how long I'm staying, how protected, weather, etc. Also depends on the anchor design in use. Some handle short scope better than others. And if going to extremes, you can take the Dashew theory of using a far bigger anchor than otherwise needed, allowing you to use very short scope and throw away half of your holding power while still having plenty left. It also depends on water depth. I'm comfortable with less scope in 50 feet of water than I am in 8 feet.

This is like an anchor discussion--lot of ways to achieve a good outcome.


Large good anchor (Rocna-or others), lot of chain, good conditions--3-1 scope works and will help you fit into some of the ridiculously crowded anchorages in the summer. Of course, more is better especially if the conditions are less than ideal.


I 2nd the idea of a range finder--I would take a few readings to other boats and different places on the shore and check & recheck to make sure I wasn't dragging or someone wasn't getting uncomfortably close.

Dropping and setting the anchor IMHO is relatively easy as compared to predicting swing and proximity in a crowded harbor.
I highly recommend another great book resource that explains it all so clearly: Happy Hooking - The Art of Anchoring by Blackwell; lots of diagrams, lessons learned and well written.

And lest we overlook what is often overlooked by “newbies”, don’t forget to add the height of your anchor roller/bow/etc Above the water line to the indicated water depth when calculating scope. Same advice if your transducer is actually a few feet below the surface. That 4+ feet in height becomes 12-20 feet of rode or more needed to maintain the scope ratio. In our case I need to add five feet to the depth shown on our depth finder in order to calculate the amount of chain to deploy.

Sometimes you also need to consider the length of your boat when calculating swinging circle. In 8’ of water @ 3:1 I have just about 60’ of chain out, but the boat is 70’ LOA for a total of 130’ of length. My bow is 10’ above the water so my calculation would begin with 18’ times 3:1 or more usually, times 5:1. Anchor is a 121lb Rocna Vulcan.

Don’t forget to add in the tide if you are anchoring at low water.....@ 5:1 a six foot tide is another 30’ of chain.

My advise is to listen to the people who anchor in the area that you will anchor. A 7 to 1 scope in the PNW ain't gonna happen very often, nor is a Bahamian moor or a stern anchor. In the PNW get a good oversized anchor, all chain if possible, and try for 3 to 1 with a GOOD SET. ALWAYS set your anchor! You will do fine if you do.