Two Anchors In-Line vs In a 'V' Pattern for Storm Anchoring

[AnchorageGuy]

Originally Posted by capngeo

Nope, you are not! The ONLY advantage is that you reduce your swing circle HOWEVER (IMHO) that advantage is negated as soon as you are 90° to the “line” and tear both anchors free! A Bahamian mooring is only effective if the loading is parallel to the set of the anchors as in a tidal situation.

Not true, once you are 90 degrees to the anchors you are now on two anchors. We road out two hurricanes this way, Floyd in the Chesapeake and another Irene in Belhaven. In both cases had the 180 degree wind shift broken out two anchors during the storm there is no way we would have retrieved them and reset them. As the wind shifts around, and it does not switch suddenly, you lay on two anchors, as in a very wide V, and then the opposite anchor as the wind continues to comes around. You are never in a position where any one of the anchors have to re-set. Speaking theoretically is one thing, but being there and seeing the results is a lot different. Being 90 degrees on both anchors will not pull them out, at least not in our first hand experience. We have been on the same anchors in sudden squalls with 50 to 60 knot winds and they have never come loose. But we have seen several brake out with sudden wind shifts on the V and believe me it ain't pretty. Chuck

[capngeo]

Originally Posted by Waterwayguy

Not true, once you are 90 degrees to the anchors you are now on two anchors. We road out two hurricanes this way, Floyd in the Chesapeake and another Irene in Belhaven. In both cases had the 180 degree wind shift broken out two anchors during the storm there is no way we would have retrieved them and reset them. As the wind shifts around, and it does not switch suddenly, you lay on two anchors, as in a very wide V, and then the opposite anchor as the wind continues to comes around. You are never in a position where any one of the anchors have to re-set. Speaking theoretically is one thing, but being there and seeing the results is a lot different. Being 90 degrees on both anchors will not pull them out, at least not in our first hand experience. We have been on the same anchors in sudden squalls with 50 to 60 knot winds and they have never come loose. But we have seen several brake out with sudden wind shifts on the V and believe me it ain't pretty. Chuck

I am not a mechanical engineer ( I'm sure there's one here that can explain this better) BUT when you string a line between two points (the anchors at 180°) and then apply force at 90°, the force applied to the anchors is exponential.... In other words, if you hang a hammock between your mast and backstay, the resulting additional tension to the stay will be extremely more than the load supported by the hammock.

Transfer that physics experiment to a Bahamian Mooring, when the wind is blowing hurricane force @90° to the line of your anchors, the force applied to those anchors is many times more than a single anchor would see if it were in line with the keel.

I am no proponent of the "V" in storm conditions either! For me it is either ONE OR THREE!

[Loquat]

Well, this is my decision if I have to leave the dock to weather the storm- The one or three idea seems make good sense.
45# cqr on 150' 3/8"chain, with 50' of nylon snubber. 45# danforth on 150' rode ready to go as standby.
This will be in 10' of water with mud bottom.
It looks like only tropical storm force winds here in Charleston, or less so we will probably stay at the dock and tie up well.

Thanks for all the input

[GordMay]

Originally Posted by Waterwayguy

... In every anchoring situation in storm force winds and seas that we have been in we have use the Bahamian moor with lots and lots of scope. In several occasions in hurricane force winds we had three anchors out in a Y pattern for want of a better explanation. That worked best for us and we felt the most secure. Good luck ...

Indeed.

[unbusted67]

Originally Posted by svcattales

We have weathered several hurricanes/tropical storms in Florida and we rode out hurricane Isabel in the Chesapeake. Here are the basic principles we use in our preps:

- Since you must start your preps long before the storm arrives you don't know which direction the wind will come from and it may come from all different directions. (Don't bet on the track or intensity of the storm... things change fast.)

- Look for a hurricane hole that gives you wind & sea protection from as many directions as possible, but leaves enough swinging room to swing 360 degrees. Hills all around is the best situation. Think about how much protection you will have if the storm surge puts you 15ft higher. (Another alternative is a very narrow creek without swinging room. In this case I would use a bow anchor, a stern anchor, and I would spider web lines to trees or mangroves to keep the boat in the middle of the creek. In this situation the boat will not swing at all so you need very good protection on both beams.)

- Decide which direction is the most exposed to wind and seas. Set your best anchor and your bow in that direction.

- Set two or three more anchors at 120 degrees or 90 degrees. (We used 4 anchors for Isabel set 90 degrees apart.)

- Secure all your anchor lines at the bow with enough slack so your boat can rotate 360 degrees without fouling on the keel. Put kellets on each rode so as the strain transfers from one anchor to the next, the kellet will hold the "lazy rodes" below the keel and not foul.

During Isabel, our boat made a 360 rotation without any fouling and we had no damage during that 100yr storm.

Whaaaaaat? Draw me a picture. Everyone draw me a picture!

[svcattales]

Originally Posted by unbusted67

Whaaaaaat? Draw me a picture. Everyone draw me a picture!

I don't have any pics, but think of it this way. We were in a creek with hills all around and the entrance of the creek was to our south. The best anchor and the bow was facing south towards the highest potential winds and seas, there is one anchor to the west, another to the north, and another to the east. There is a 90 degree angle between each anchor. As the storm passes, the wind changes direction and the boat swings thru 360 degrees. Each anchor takes its turn holding the boat and at times two anchors are holding equally.

Each anchor rode has quite a bit of slack in it to allow for tidal rise and to avoid the keel "tripping" on the rodes as boat started to swing. The kellets (weights) on each rode sinks the rodes with no strain so the keel will pass over the rode when boat swings from one anchor to next. We used lead dive belts, dingy anchors, dumbells etc for kellets... anything with some weight to it.

The difficult part was finding enough bow cleats to secure 3 extra rodes. I now keep a 12" diameter iron ring on board so i can tie all the rodes to the ring and tie the ring to my bridle.

Hope this helps.

[mr-canada]

Anchoring diagram in my situation.

It's pretty rudimentary as a drawing.

The V is directed towards the biggest waves (lots of fetch) and also to reduce swinging due to the nearby rock. Good holding because it's sand and mud, anchors setting first time even without reversing. Both coming off the bow.

If the storm winds or huge commercial wakes hit they will tug against the V. The ferry wake from behind is somewhat sheltered by the point by the public dock so I'm not as worried about that. Deep V hulls cross all the time but I'm sheltered by the islands.

This isn't the best configuration for every situation, but this is set up for a long term hold as I'm sitting on a waitlist for a marina about 20 minutes away and it could take a while (ie. months). Have a lemon of a motor on the foredeck I might drop with a buoy in between the V for extra holding power if I'm stuck there when the storms start to come more frequently, just one more thing to tug against and maybe reduce the strain on the anchors.

Its all about reading the lay of the land, current and weather. No one configuration is going to work everywhere. If I had more swinging room (there's lots of boats because it's summer) I might have just gone deeper in the cove and payed out a ton of chain and rode and left it with a single and dropped the motor as a buoy as a safety.

Boat is holding, despite some shipping traffic deep waves that are bad enough to wake you up at 3am at night making the boat creak. Anchors are Danforths, they both grabbed first try, one twice because I picked the wrong spot for the main anchor and had to make an adjustment to avoid that rock

[Dave_S]

Originally Posted by capngeo

I am not a mechanical engineer ( I'm sure there's one here that can explain this better) BUT when you string a line between two points (the anchors at 180°) and then apply force at 90°, the force applied to the anchors is exponential.... In other words, if you hang a hammock between your mast and backstay, the resulting additional tension to the stay will be extremely more than the load supported by the hammock.

Transfer that physics experiment to a Bahamian Mooring, when the wind is blowing hurricane force @90° to the line of your anchors, the force applied to those anchors is many times more than a single anchor would see if it were in line with the keel.

I am no proponent of the "V" in storm conditions either! For me it is either ONE OR THREE!

Everyone's right :-). Never been anchored in a big storm but the physics of it is....

With the anchors on the same line apposing each other and a load is applied at right angles at the mid point between anchors, before the angle of the load moves from 90* the anchors provide no resistance. As soon as the boat moves and changes the load from 90* to more than 90* the anchors provide increasing resistance with increasing angle. It is not until both anchors are in-line with the load that they each provide there maximum resistance.

At some point during the drag they will pass through both the 120* and 90* settings to get to in-line.

If one anchor the load will pull in line with the resistance, if the boat swings and the anchor has an arm ((they all do) distance between where the anchor bites and where the chain attaches) it will wiggle the anchor as the load moves from side to side. In the 2 anchor system the swinging load will transfer from one anchor to the other as the boat swings and the pull will initially be in direct line with the resistance.

In summary. if the load will always be from one direction or only 180* swing, 2 anchors in line will be best. If the load is going to swing a V anchor set up would be better. The more swing the wider the V.

[Pelagic]

Your main anchor, ground tackle should be typhoon rated and I see the spare as more of a back up rather than an add on

For the frequent Typhoons in the Philippines, I am more a believer in one strong anchor and heavy tackle well set in a hole so that when the west bound eye passes either north or south of you, the force is always pulling uphill when anchor pivots .

Lots of swing room, maximum scope and good heavy mud/sand holding with a gradual slope to a soft muddy beach describes my favorite Typhoon Shelter.

[Mischief_Inc]

I would think that setting them in a V would reduce your shearing (sailing back & forth) at anchor, since there's a lot less room for the boat to move around due to the anchor locations.

Also, there have been a few good discussions on dual anchoring/tandem anchoring of late. Including a lot of feedback by some experts on the topic. And instructions on how to do it correctly. Particularly as some of the posters in the thread spent a good bit of time where tandem anchoring was all but a necessity, due to the violence of the winds. Such as in some of the fjiords in Chile.

[mr-canada]

Originally Posted by Dave_S

With the anchors on the same line apposing each other and a load is applied at right angles at the mid point between anchors, before the angle of the load moves from 90* the anchors provide no resistance. As soon as the boat moves and changes the load from 90* to more than 90* the anchors provide increasing resistance with increasing angle. It is not until both anchors are in-line with the load that they each provide there maximum resistance.

At some point during the drag they will pass through both the 120* and 90* settings to get to in-line.

If one anchor the load will pull in line with the resistance, if the boat swings and the anchor has an arm ((they all do) distance between where the anchor bites and where the chain attaches) it will wiggle the anchor as the load moves from side to side. In the 2 anchor system the swinging load will transfer from one anchor to the other as the boat swings and the pull will initially be in direct line with the resistance.

I'm no engineer either. But I do know that things move to the path of least resistance. In a blow or with deep swells/waves, once one anchor is holding the path of least resistance is swinging until the other anchor is grabbing, bringing you to the path of maximum resistance because there is no path of least resistance left.

I guess the path of least resistance would be for the boat to move forwards into the V; but that's where reading the lay of the land, tides and current comes in. In my own configuration (diagram above) I'm not going to get wind, current, or big waves or wake from behind, and I'm not going to get that bouncy wake from the deep V displacement hulls from the side coming from the other side of those islands.

I read a thousand pages of wave theory, and the worst waves I'll get is coming from the direction I placed the V; mostly because of the long fetch, but also because of heavy shipping traffic out there in the straight. Current isn't such a huge issue in this location as there are lots of places for the current to enter/exit the sound (this is just one of six islands in the mouth of this sound, farther north there's a vortex where the current and wind gets nuts because there are no other points of entry). The tides in this location are more of a "rising tide floats all boats" variety rather than a strong inflow and outflow; plus there are three ways for the tide to enter and exit this cove.

Again; I'll stress that this is not the right configuration for everyone in every anchorage. In anchorages with a lot of swinging room and good holding, cranking out the scope and using one anchor is not only simpler but has less chance to foul (by twisting the chain/rode), with more tensile elasticity to handle the waves. Unfortunately, in this area most good anchorages are pretty busy and you're always going to have a lot of boats because everywhere else is just steep drops of rocks - so you get long stretches with no good anchorages and then encounter busy good ones and this one is one of the better ones.

Plus given I am here for the long haul waiting around for a slip, you never know when some dude in a charter decides to try out anchoring and lays out 7:1 scope like it says in the books for good measure and is swinging around like a battering ram hitting everyone who is just dropping a hook at 3:1 for the night. Better to stay stationary as possible and minimize swing. Plus with Danforths wide swings can dislodge the anchor so it's better to minimize swing.

Just read your terrain, check your charts for the current flow, double check your holding, and assess what anchoring type is good for you.

I'm surprised at how many tandem anchoring fans are crapping on different anchoring methods online. Tandem has it's place but if you drag one anchor is not going to hold onto anything that the anchor ahead of it dredged.

[Zven]

Different types of anchor tend to excel at different bottom conditions ... For example, a Danforth is said to be great in sand but less so among rocks. Also, in many places the bottom conditions will be somewhat varied. Isn't that an argument for tandem anchoring with two different styles of anchor? Especially if bad conditions are expected, of course.

[mr-canada]

Originally Posted by Zven

Different types of anchor tend to excel at different bottom conditions ... For example, a Danforth is said to be great in sand but less so among rocks. Also, in many places the bottom conditions will be somewhat varied. Isn't that an argument for tandem anchoring with two different styles of anchor? Especially if bad conditions are expected, of course.

I haven't heard of tandem anchoring with two multiple different anchor types, but I'm sure there's a condition where it might be worth a try. In a brutal blow where you need holding power bad, people toss every anchor they have in the kitchen sink all around the boat and even tie off to trees at the same time.

I have an old lemon of an outboard engine, I'm thinking of dropping it and making a makeshift buoy out of it. In a blow it wouldnt be sufficient alone because it would probably drag, but in calm weather it would probably hold just due to it's weight. Sucker was found by the guy I bought the boat from at the bottom of the ocean... and I think it's going to return after all the trouble it's given me. Lower leg is chewed up and there is no replacement lower leg unit for it anywhere. Just sitting on the deck.

Honestly you can use just about anything and try anything, its all about reading the land features, any hazards, prevailing wind patterns, typical currents and using a configuration that best suits with whatever you happen to have.

[UNCIVILIZED]

You guys have seen rigging plates for combining multiple anchors, right? They're much like the plates used to connect multiple static belay anchor points when climbing.
Hurricane Mooring System — Colligo Marine®

[Palarran]

Originally Posted by Pelagic

Your main anchor, ground tackle should be typhoon rated and I see the spare as more of a back up rather than an add on

For the frequent Typhoons in the Philippines, I am more a believer in one strong anchor and heavy tackle well set in a hole so that when the west bound eye passes either north or south of you, the force is always pulling uphill when anchor pivots .

Lots of swing room, maximum scope and good heavy mud/sand holding with a gradual slope to a soft muddy beach describes my favorite Typhoon Shelter.

+1

To the OP's direct question, I don't personally like either the inline or v pattern. The chance of tangling my anchors and creating a huge problem in the height of a storm isn't worth the possible extra holding, IMO.