I Will Pay The $$. Which Anchor Is Best?

[ranger58sb]

Two to Tandem: Maximizing Holding Power by Tandem Anchoring

Danforth types including the Fortress are shocking and are absolutely to be avoided. They are not general purpose anchors, and have no place in a tandem rig.

I see it's Peter Smith saying that. Don't understand why, though. In the sentence above, he rails on a bit about anchors that have trouble setting... and then switches to beating up Danforth-style anchors as not being "general purpose" anchors. Guess that might depend on where, and the typical substrate wherever there is. Anyway, we've never had any problem setting our Fortress anchors, and they seem to be reasonably well-suited to this area.

(Might not work all that well on the coast of Tasmania or wherever he cruises, but then I don't expect to be there anytime soon... which means anchors that work well off the coast of Tasmania or wherever don't necessarily hold any extra attraction for our current boating adventures.)

@Steve Bedford: Comment on tandem anchoring with the SuperMAX? Built in trip line hole, looks to positioned well enough, on casual inspection...

In any case, I think I can't get enthused about the extra work, unless serious weather threatens. I like the "get a bigger primary anchor" idea, although I'm already probably up near the limit of what I can lift manually if the windlass craps out. And my pulpit -- at least on this boat -- might not take anything much bigger anyway.

-Chris

 

[psneeld]

Here is yet another published "expert"...this guy totally reverses the danforth tandem concept....

Anchoring 201

*The tandem anchor rig is a quick, easy way to increase the holding power of a single anchor rode by deploying two anchors on the same rode.**Stock-stabilized, pivoting fluke anchors (like Danforths) work best in this application, particularly in mud – U.S. Navy tests show use of tandem anchors increases total holding power by as much as 30 percent over the same two anchors if deployed separately.**These tests also showed holding power in sand increased only slightly overall when setting tandem anchors, most likely because the anchors themselves were designed for use in sand – in other words, use of a tandem rig closed the holding gap a bit between sand and the poorer holding quality of mud.

Any wonder why more and more boaters are skeptical of "published" marine experts?

As to Peter Smiths comments on danforths..I have come to the same conclusion about danforth style anchors.... BEST of the best for high holding, especially the fortress..but NOT a general use, all around, every day anchor. Before the gangup...I have 2 anchors for sale on Craigslist so I can go buy a Fortress as a stern, storm, backup anchor....I believe every cruiser should have one...but along with all the anchoring experts...there is no right answer....

 

[ranger58sb]

Here is yet another published "expert"...this guy totally reverses the danforth tandem concept....

Anchoring 201

*The tandem anchor rig is a quick, easy way to increase the holding power of a single anchor rode by deploying two anchors on the same rode.**Stock-stabilized, pivoting fluke anchors (like Danforths) work best in this application, particularly in mud – U.S. Navy tests show use of tandem anchors increases total holding power by as much as 30 percent over the same two anchors if deployed separately

As to Peter Smiths comments on danforths..I have come to the same conclusion about danforth style anchors.... BEST of the best for high holding, especially the fortress..but NOT a general use, all around, every day anchor.

I saw the Sail article said almost the same thing about the Navy tests, although apparently without knowing the Danforth-style was used.

"How much tandem anchors increase holding power is dependent on many factors, but tests conducted by the U.S. Navy reveal that tandem anchors set in mud increase the holding power by 20 to 30 percent compared to the same two anchors deployed individually. The increase in holding power is less marked in harder bottoms, such as sand. (Note: we don’t know what type of anchors were used in this test.)"
​

Seems to me a good case to increase the size of the anchor, but then again I know there's a max limit to the sizes makers offer... and single larger anchors for Navy ships might well be over that limit.

I think I don't disagree with Peter Smith's opinion that Danforth-style anchors might not be "general purpose" tools... but modified by quibbling a bit over the words "general purpose." If I were sailing the seven seas, I think I'd want more anchors on board that were maybe better for non-mud bottoms. OTOH, here in the Chesapeake, "general purpose" actually means "mud/hard mud/soft mud/slime/ooze/thick mud/grassy mud/muddy abandoned oyster reef/etc." and the Danforth-style (at least the Fortress versions that I've used) are about as "general purpose" as they come.

I'm coming to think that if I had to anchor out for a hurricane, I might choose the tandem approach (or that "hammerlock" thing looks interesting, and easier), with SuperMAX 17 as primary and FX-37 as secondary... perhaps both (but at least the FX-37) adjusted to the mud setting... instead of a Bahamian-like deployment... perhaps influenced by that Navy wording (probably paraphrasing)... and certainly influenced by those being the two proven mud-capable anchors that I've already got.


OTOH, so far, my hurricane plan has been to a) move to better floating docks somewhere (twice) or b) haul-out, if possible) in the time frame and if predicted storm surge probably wouldn't float us off the blocks. I think I still like these plans better than anchoring out somewhere an abandoning the boat to its fate.

-Chris

 

[Nomad Willy]

PeterB,
Perhaps the Rocna just has'nt dragged. They are after all a very good anchor.

 

[Pgitug]

As I stated earlier. The sole reason for using a tandem anchoring system is for the off chance that your Rocna type anchor fouls on a round piece of coral or picks up a crab trap while trying to reset. And yes, I do think there are a few lost crab traps out there. So if you have an oversized anchor for insurance, you still have the one off chance of having that big heavy anchor picking up a crab trap when the wind shifts and the anchor begins it's new direction reset. I can guarantee you that if the pointy end of your anchor snags a half buried crab trap it is not going to set. And your boat is now a drift while you slumber. What are the chances of that ever happening??? It happened to my friend as previously stated. I just want to know that I have done everything to insure that it does not happen to me. Everybody for their own reasons have different anchoring methods. Tandem anchoring is mine.

 

[ranger58sb]

As I stated earlier. The sole reason for using a tandem anchoring system is for the off chance that your Rocna type anchor fouls on a round piece of coral or picks up a crab trap while trying to reset.

Fair point. We picked up what looked like a 3' x 3' piece of roof shingle a couple weeks ago, and we did drift a bit overnight, I think about 40' or so.

(Believe it didn't happen when we originally set the anchor, but during some maneuvers we tried to make while still anchored in order to aim our loudhailer at the 18-boat raft behind us, with their music turned up loud enough so everyone in the county could enjoy it. Local water police eventually solved that, probably in response to calls from everyone anchored in the creek and especially the local homeowners.)

Anyway, it was wrapped over the middle fluke and one of the outside flukes. Looked like the effect was to create a big round ball of mud, two out of the three sharp points blunted. And it seemed like we brought up about twice as much mud as usual when we weighed anchor.

I had to futz with a boathook to get the shingle (or whatever it was) to come loose.

I could see where a second anchor could have mitigated that...

-Chris

 

[ranger58sb]

Here is yet another published "expert"...this guy totally reverses the danforth tandem concept....

Anchoring 201

Ummm... that ref includes this:

When preparing a tandem rig be sure to attach the second or aft anchor rode to the forward anchor’s crown rather than its ring...
​

Which do we think is "aft"?

Why be attaching a secondary anchor rode directly to another anchor? Instead of to the other anchor's rode? (Except perhaps in the Rocna example, where that seems to be quite appropriate.)

??

-Chris

 

[psneeld]

Ummm... that ref includes this:

When preparing a tandem rig be sure to attach the second or aft anchor rode to the forward anchor’s crown rather than its ring...
​

Which do we think is "aft"?

Why be attaching a secondary anchor rode directly to another anchor? Instead of to the other anchor's rode? (Except perhaps in the Rocna example, where that seems to be quite appropriate.)

??

-Chris

Who knows...half of these guys are probably better writers than boaters.

I can understand the one reference that unless the manufacturer supplies a recommended hole on the anchor to attach another anchor to....then best add it to the rode.

I surmise that is so when the lead anchor digs, it doesn't change the angle of the anchor closer to the boat.

 

[Nomad Willy]

Weight affects a lot of elements of performance beyond fuel burn.

Weight can have a profound effect on trim that can have positive or very negative effect on turning and ultimately boat control can be lost in certian circumstances.

Weight as an excess is always bad.

 

[Steve Bedford]

"@Steve Bedford: Comment on tandem anchoring with the SuperMax? Built in trip line hole, looks to positioned well enough, on casual inspection..."

There is a "trip line" hole on the opposite end from the rode hole that could indeed be used in a tandem arrangement with the Super Max Anchor. However, tandem anchoring is just one option for arrangement when the decision is to use multiple anchors. If using more than one anchored and each anchor has its one rode terminating on th vessel, you are actually considered to be moored.

Rudy and Jill Sechez, in their excellent book (no affiliation), Anchoring, A Ground Tackler's Appentice advocate, and I agree, state that the ground tackle for each anchor should be based on the "Big 5." These are size of the anchor, the design of the anchor for its intended purpose, the strength of the components, the desired scope, and chaife protection.

Whatever method of multiple anchors the captain chooses, one should not "assume" that two anchors with marginal specs regarding the "Big 5" will be sufficient. Instead, each anchor and its accompanying ground tackle should be sized sufficiently to safely hold the vessel under normal conditions. Remember, if one anchor gives way, you are on that one remaining anchor. If it is undersized, you may have a serious issue.

Steve Bedford

 

[ranger58sb]

I hadn't really paid much attention to the "tandem" idea, even though I'd heard a bit about it over the years. Did have to do a modified Bahamian once, years ago, odd circumstances... I couldn't that it worked any better than a single anchor, and it took some work.


Having read over the last few references here.... I'm beginning to better appreciate that "Hammerlock" thing mentioned in the "Anchoring 201" ref.


I think if I were to have to do that, I could, relatively easily, deploy our FX-37, back down and set that properly... then move the boat back up that rode and deploy the SuperMax 17 in the same line as we used to set the Fortress (using track on plotter?), back down and set that properly but on slightly shorter scope.


Both anchors are properly sized for our boat: Fortress actually one size larger than maker recommendation, and the Max size also appropriate as a storm anchor.


Still thinking about it, though. Seems like high potential for fouling rodes, if the boat does any 360°s. Just attaching the Fortress via the Max trip-line hole -- in an actual tandem rig -- would maybe better deal with that fouling potential...


-Chris

 

[psneeld]

I think the hammer lock is only when your boat is sailing back and forth on an already tight rode.

It is not much more than using it as dead weight to slow the zig zagging. It you actually tried to set it on a short scope in bad conditions it would probably pull out anyway. And if set on a longer scope, might as well just set 2 anchors at 60 to 90 degrees normally.

 

[ranger58sb]

I think the hammer lock is only when your boat is sailing back and forth on an already tight rode.

It is not much more than using it as dead weight to slow the zig zagging. It you actually tried to set it on a short scope in bad conditions it would probably pull out anyway. And if set on a longer scope, might as well just set 2 anchors at 60 to 90 degrees normally.

Ah. Hadn't realized it was mostly about that. Thanks.

With no keel to speak of, we do tend to sail a bit under some conditions...

-Chris

 

[Nomad Willy]

Steve Bedford wrote;
"Remember, if one anchor gives way, you are on that one remaining anchor. If it is undersized, you may have a serious issue."

Steve it's kinda like the twin engine question. When my 40hp engine fails I'd rather have a 5hp engine to take over powering the boat. When the 40hp engine quit I'd consider a spare 5hp a blessing .. not an issue. And if I had a secondary anchor it would be much like (but not like) the secondary engine. The anchor question is less black and white but in most situations it would be preferable to have a small anchor dragging than nothing.

But if the holding power of the secondary anchor was far less than the primary ... why bother? As I always say use one big anchor instead of two small ones for better results. But reducing the shock loads w two anchors may increase the probablity of one anchor being always set or dragging slowly while the other resets.

So as I see it tandam anchoring has three advantages:

1. The ability to deploy much more holding power when you're deploying anchors by hand. Two 20lb anchors set well is better than one 20lb anchor. And deploying a 40lb anchor may be too difficult physically. This obviously dos'nt have wide appeal here as most on TF have a winch.

2. Absorbing shock loads that may cause a breakout. There are several different riggs that reduce the shock loads and likely would arrest a breakout. So a secondary anchor can not only add holding power but can act as a Big Kellet hugely reducing shock loads and increasing catenary.

3. As earlier presented in post # a trailing anchor like a small Fortress could keep a big Bruce down in the seafloor by not permitting the back end of the Bruce to pop up and out .. Like it does as evidenced by Steve's (Panope) tests. The Bruce/Claw could possibly go from a questionable anchor to a top performer. I'd like to see a test of this. A lot of skippers could add a tag Fortress to another anchor greatly increasing it's performance. Kinda like a farmer pushing down on the plow handles to keep the plow business end in the ground.

 

[psneeld]

My understanding of tandem anchoring depends on forces acting simultsneously on the 2 buried snchors.

If not, none of it is remotely predictable and as soon as on breaks free you are really only depending on the other anchor...and that cycle continues. Especially if the setup at ALL causes on anchor to lessen the others ability to stay put.

 

[Nomad Willy]

Now after posting and thinking I like Ptitug's post #201.

I'm wondering if it will work better closser hauled .. say 2-3'. With a Claw the trip line attach hole is at the top of the anchor where tension woul tend to hold the Back of the Claw down. With the business end held down it can't help but hold. So if I said anything critical about Ptitug's system I take it back. But now I'm thinking it could interfere w the main anchor setting. Probably would'nt help the Rocna any w it's trip line low. May insure it will stay upside down. Hmmmm

 

[ranger58sb]

But if the holding power of the secondary anchor was far less than the primary ... why bother? As I always say use one big anchor instead of two small ones for better results. But reducing the shock loads w two anchors may increase the probablity of one anchor being always set or dragging slowly while the other resets.

So as I see it tandam anchoring has three advantages:

1. The ability to deploy much more holding power when you're deploying anchors by hand. Two 20lb anchors set well is better than one 20lb anchor. And deploying a 40lb anchor may be too difficult physically. This obviously dos'nt have wide appeal here as most on TF have a winch.

Just to keep stirring this pot...

There's a third option: two BIG anchors.

The point about being able to manually lift an anchor of X weight is I think important... even for those of us with powered windlasses... as in cases where the lift mechanism maybe craps out.

But aside from that, or maybe "within those dead-lift limits," I doubt I'd get all that enthused -- especially given the extra work involved -- about two small anchors, or one large and one small anchor, deployed in tandem.

I reckon if I need extra holding power, and it's gonna take some work to get there from here... I'd just as soon get a as much extra holing power as possible from that second anchor. Which suggest BIG. (At least within the same dead-lift limits that are already impacting my choice of primary.)

-Chris

 

[Nomad Willy]

Ranger,
Yes of course big is good and for years I've supported combining the two anchor weights and get one big anchor.
But in certian circumstances the tandem makes sense to me. Especially the Ptitug rig w the smaller Fortress.
The well known two anchors w their own rodes system looks troublesome and vulnerable to me. Tangled rodes is not something I'd want to deal with.
Personally I'm betting on a modified anchor w better penetration for better performance from a 15lb anchor.
A combination of two anchors w a different stack up of strong and weak points could possibly work together better than singularly. And Ptitug seems to have a system that would be one to adopt or one to try as a jumping off point to something even better. A fortress for example, w it's extreme holding power coupled w an anchor that has ultra dependable setting ability (perhaps a Claw) may make a great combination. Pick and choose.

 

[Nomad Willy]

I think that was my point Eric. If they have never fouled in all that time, when in the normal course of events, one anchor would have to be being dragged past the other as they re-set after a current/tide/significant wind shift, and during which you would surely expect the Rocna to pick up the line to the Fortress across its fluke once in a while at least, does sort of beg the question...is the Rocna, the second anchor, and therefore the one that would have to be dragged past the Fortress in that re-set, ever in fact doing so..?

Or, is it staying set, twisting round, or breaking out but re-setting so quickly it is in effect rendering the Fortress at the end of the connecting line, basically redundant..? One would never know. You can't see. But never fouling one on the other in all those years might be the only evidence that might be the case.

My respectful suggestion therefore to PgiTug, is to just leave the Fortress off a few times and see how that goes. What's to lose..? Psneeld does that all the time. Marin also. In fact everyone else that uses a Rocna I know of does just that. He may be going to that extra effort for nothing, even if he has it down to a fine art. Just sayin'



Peter,
Finally getting back to this.

Yes the Fortress may be a waste of time. Would be a waste of time if it never dragged. And if it's that big and well deployed the Fortress is just extra baggage. Also the Rocna has it's tandem anchor or trip line hole very low on the Shank so the front end of the rode to the Fortress may impede penetration of the Rocna because the short rode would need to be dragged down through the bottom to fully set the Rocna. The drag on that short rode would tend to hold up the back of the Rocna.

But you're right ... if there's no advantage why do it? But how are you going to know that? I anchored in 50 knot gales twice, once w a 13lb anchor and once w an 18lb anchor. Would I have been better off w a tag anchor or a bigger anchor? Obviously not as we didn't drag.
I see the tandem anchoring as a good way to extend the conditions and/or bottom types that one's "gear" can successfully operate in. One can have a Fortress and operate in rocky bottoms or have a Rocna and operate in mud. You having a Super Sarca probably wouldn't benefit (or not very much) from a tandem arrangement since the SS operates gracefully and dependably on essentially all bottoms.

My respectful suggestion therefore to PgiTug, is to just leave the Fortress off a few times and see how that goes. What's to lose..? Psneeld does that all the time. Marin also. In fact everyone else that uses a Rocna I know of does just that. He may be going to that extra effort for nothing, even if he has it down to a fine art. Just say'in'[/QUOTE]

 

[psneeld]

I have a 60 pound Manson Supreme....

 

[Peter B]

PeterB,
Perhaps the Rocna just has'nt dragged. They are after all a very good anchor.

Exactly...that was my entire point Eric. Quite possibly allowing PgiTug to think his tandem system was working fine, when actually the Rocna was rendering the Fortress redundant anyway.

 

[BruceK]

The 2 anchor set up seems to me to present the complexity of a triple backwards somersault Olympic Games dive, with pike. IMO, better off selecting a good multipurpose anchor, or 2 if you prefer to select anchor design based on the bottom type, and go with that.
But if you find you can routinely anchor using a 2 anchor set up,and you can make it work without arguments between the 2 anchors and rodes, it works for you so go with it. Anchoring is something of a black art, if anchor whispering works, that`s your method, have faith in it.

 

[Peter B]

I have a 60 pound Manson Supreme....

Sorry, but same difference essentially...

 

[ranger58sb]

I have a 60 pound Manson Supreme....

You're younger and stronger than I am. I chose to stop at the 50-lb MAX.

The 2 anchor set up seems to me to present the complexity of a triple backwards somersault Olympic Games dive, with pike.

Sounds about right, to me.

After more thought, I suspect I could deploy and set our Fortress with some slightly different rode connections than our normal... then move back up that rode, remove part of that modified rode, and shackle the rest to our SuperMAX at a useful distance... then deploy and set the MAX in the same line...

Both of our anchors are (said to be) suitable for storm conditions for our boat.

Would I need to or want to do this routinely? Absolutely not. Would I want to do this occasionally, if heavy weather threatens? Wouldn't be my first choice; I still like my existing hurricane plan. But then I usually have the luxury (?) of working that kind of plan.

So I think what I could do -- with tandems and modified rodes and setting two anchors and all that -- isn't really high on my list of what I would do.

Mostly due to that complexity thing.

-Chris

 

[Steve Bedford]

"Steve it's kinda like the twin engine question. When my 40hp engine fails I'd rather have a 5hp engine to take over powering the boat. When the 40hp engine quit I'd consider a spare 5hp a blessing .. not an issue."

Sorry, I have a different opinion. You would never use your 40hp and your 5hp together. Having a 5lb anchor as a back up to your primary anchor is quite different than using them in tandem. If the 40lb breaks free in the middle of the night, you of course can not expect the 5lb to hold.

"But if the holding power of the secondary anchor was far less than the primary ... why bother? As I always say use one big anchor instead of two small ones for better results."

Agree.

Steve Bedford

 

[Anchor Brian]

I have referenced Bob Taylor in past discussions for his extensive scientific anchoring knowledge that he acquired during 45+ years with the US Navy and offshore industry.

Our late company founder kept a small library of his US Navy work and here's a download to a report that Bob did on multiple anchor use:

NCEL Tech Data Sheet 83-05.pdf


On page 4 ( image below) of this report is a brief summary of different anchoring set ups. When I questioned him recently on using our anchor in a tandem (or piggyback) combination, his comment was:

"The best way to use Fortress and most other anchors with this configuration in tandem is to use option 4 in table 2 of the Tech data Sheet. This allows each anchor to function properly. In reality the rear-most anchor will eventually move into the trough created by the front anchor and dig deeper than it normally could resulting in more than twice single anchor capacity."

gif uploader

 

[ranger58sb]

I
"The best way to use Fortress and most other anchors with this configuration in tandem is to use option 4 in table 2 of the Tech data Sheet. This allows each anchor to function properly. In reality the rear-most anchor will eventually move into the trough created by the front anchor and dig deeper than it normally could resulting in more than twice single anchor capacity."

How would one actually deploy that (option 4) set-up? Shackle the two anchors (anchor chains) to the main rode, dump it all overboard, back down?

If one anchor sets first (which might it be?), how would one get the other to set? How would one know that had been accomplished?

-Chris

 

[Anchor Brian]

I think this is a narrow variation of a Bahamian mooring where each anchor is on its own rode. I will check to make sure.

I found this animated Gif for setting two anchors on a sailing site awhile back.


image upload with preview

 

[Nomad Willy]

But if the wind even changes 20 degrees the load is almost all on one anchor.

One anchor 20% bigger would be better.

Love your graphics Brian. Especially the propwash.

 

[Nomad Willy]

I have a 60 pound Manson Supreme....

I have a 15lb Supreme. Well it was a Supreme.