Anchors, Guns and Strippers!!!!

[Dockhead]

Originally Posted by rslifkin

This is almost certainly the case, at least with some designs. I was recently deciding between a 55lb and 73lb Rocna Vulcan for my boat (decided to go with the 73 in the end). The 73lb anchor has 20.2% more fluke area than the 55lb according to Rocna's numbers, but it's 32.7% heavier (and I'm sure not all of that difference is in the bigger shank).

OK, that makes sense.


So the bigger anchor will be denser and so will dive better and will penetrate better in difficult bottoms. That corresponds well to my experience.


It will have less fluke area per unit of weight so perhaps in excellent bottoms it will NOT indeed perform disproportionately better, but perhaps even worse. But that's not where we need the extra holding power, is it?

[GRIT]

Originally Posted by rslifkin

This is almost certainly the case, at least with some designs. I was recently deciding between a 55lb and 73lb Rocna Vulcan for my boat (decided to go with the 73 in the end). The 73lb anchor has 20.2% more fluke area than the 55lb according to Rocna's numbers, but it's 32.7% heavier (and I'm sure not all of that difference is in the bigger shank).

That's interesting. I just looked at spade anchor sizes and noticed the same thing. The spade s100 weighs 44 lbs, and the 200 weighs 120 lbs. Though it only has twice the area, it's nearly three times the weight!

Another data point.

Paul.

[rslifkin]

Originally Posted by Dockhead

OK, that makes sense.


So the bigger anchor will be denser and so will dive better and will penetrate better in difficult bottoms. That corresponds well to my experience.


It will have less fluke area per unit of weight so perhaps in excellent bottoms it will NOT indeed perform disproportionately better, but perhaps even worse. But that's not where we need the extra holding power, is it?

I'd expect the 20% bigger anchor to have about 20% more holding power in any bottom (related to size, not weight). But the increased weight vs size should make it easier to set in a hard to penetrate bottom.

[Lodesman]

Originally Posted by Mike OReilly

I base it on my experience, on the experience of most cruisers, and on basic physics.

You've polled most cruisers, then? Tell us about your experience. I'd love to read your take on the "basic physics" as well?
I honestly can't say that I would be able to tell difference in the set-ability of a larger Rocna over our much used 33 - that sucker digs in immediately, and I know that about 60% throttle in reverse does not bury it completely in hard sand.

Once again, weight is a factor for initial setting. But what really holds is the force generated by the buried flukes. This is a factor of design and surface area. A larger anchor of the same design produces more force than a smaller when buried to the same degree. Weight is a proxy for these factors.

No comment on Spade's position that weight is not a "proxy" for size and design?

You seem to want to fight.

Discussing an issue vigorously is not "wanting a fight" - and yes I will press for facts, data and even a decently-articulated pet theory. Opinions carry much less weight.

I keep stating that burying the anchor is key. And if you cannot get the anchor sufficiently buried, this could be a problem. This is why you need to size your anchor such that it can be managed by the crew, and the boat's systems, without undue effort.

See we have a point of agreement.

Boat systems could include engine size, although experience (mine, and most other cruisers) is that this latter factor is less of a concern.

Again you're speaking for most other cruisers, so I'll just ask what this means with regards to your boat(s)?

[Lodesman]

Originally Posted by GRIT

I have indeed had two of the same anchor. We cruised 6 years with a Bruce 15kg, and 8 years with a Bruce 30kg. The 30 kg certainly dug in much better in grass, and other difficult substrates. I did not test them side by side, but I hope you'll agree that 6 years experience with one anchor would give me enough insight to know if the second anchor sets better in different substrates.

.

Now that to me is a valuable opinion. Same boat? Same cruising grounds? Did you make a comparison of the amount the different anchors "penetrated" into the ground. How do you quantify the difference in setting characteristics?

It should be noted, a Bruce is an old-gen anchor, and not really in the same category as what we're discussing, but it adds to the conversation.

[Lodesman]

Originally Posted by Dockhead

Belay the chain with something as strong as the chain -- don't rely on the snubber for this.

.

I agree with this, but there is a practical limit to this without making major structural changes to the boat.

I'm certain I've seen pic's (possibly in this forum) of ripped-out bitts, and other damage done to anchor chain-securing structures.

[Mike OReilly]

Lode, if you want to discuss this rationally, I'm happy to do so. But you're just trying to score points. I've not interest in that game.

I've stated very clearly why a larger anchor is better than a smaller one. Most experienced cruisers appear to agree. I've not challenged you on your experience, but it certainly seems like yours is limited.

If you prefer a smaller anchor, then go for it. Let us know how it works out.

[Lodesman]

Originally Posted by Dockhead

So the bigger anchor will be denser and so will dive better and will penetrate better in difficult bottoms. That corresponds well to my experience.

I know what you're saying, but pedantically it's not denser, being made of the same material. The thickness of the plate and shank structure is that much greater in the larger anchors, so the weight is increasing at a volumetric rate, not per surface area.

[Mike OReilly]

Originally Posted by rslifkin

I'd expect the 20% bigger anchor to have about 20% more holding power in any bottom (related to size, not weight). But the increased weight vs size should make it easier to set in a hard to penetrate bottom.

Exactly. This is the bottom line for anyone wanting or willing to understand. Those with actual experience know bigger is better. Which is why it is best to get the largest scoop-style anchor that your crew, and boat systems, can manage without special effort.

It's important to emphasize that this refers to your bower anchor; the standard working anchor you use most of the time. I want my bower (and anchoring system) to be able to manage most conditions up to about Beaufort 9/10*. Beyond that we're talking major storm conditions which probably do require special effort. Storm anchors, multiple anchors, land tie-offs ... whatever.

(*this is not the only consideration, of course. Other factors come into play).

[jtsailjt]

The argument being made regarding the smaller anchor having greater holding power because it can more easily be fully buried seems to be leaving out a pretty important consideration. While I can see an oversized new gen anchor not fully burying as a result of only moderate backing down forces during the setting process, when the wind pipes up so more holding power is needed, the additional pulling force on the anchor that’s a result of the stronger wind will provide the force needed to more completely bury the larger anchor. So the additional holding power of the larger anchor will become available when you need it most. I think the argument that a smaller, fully buried anchor will be less likely to pull out and potentially drag a ways before resetting does have merit.

I don’t doubt the Viking test claims but they specify that they did all their testing off “the same beach.“ But there are many other types of bottom than sand that our anchors have to perform well in.

So I have to fall in the Dashew camp and my everyday anchor that lives on my bow roller is a slightly oversized (99# on 47’ heavy cruising sailboat) Spade and I’ve been very happy that so far it always digs into/through whatever the bottom consists of and has never dragged even a little bit (knock on wood). I’m sure my beefy windlass would have no problem retrieving an even heavier anchor but the moment arm of the longer shank would make pulling it over the bow roller difficult. So I think I’ve found the sweet spot regarding anchor size for cruising in my boat, and feel confident that if I ever go on the rocks it’s not going to be the fault of my anchor.

[Uncle Bob]

Originally Posted by jtsailjt

I don’t doubt the Viking test claims but they specify that they did all their testing off “the same beach.“ But there are many other types of bottom than sand that our anchors have to perform well in.

So I have to fall in the Dashew camp and my everyday anchor that lives on my bow roller is a slightly oversized (99# on 47’ heavy cruising sailboat) Spade and I’ve been very happy that so far it always digs into/through whatever the bottom consists of and has never dragged even a little bit (knock on wood). I’m sure my beefy windlass would have no problem retrieving an even heavier anchor but the moment arm of the longer shank would make pulling it over the bow roller difficult. So I think I’ve found the sweet spot regarding anchor size for cruising in my boat, and feel confident that if I ever go on the rocks it’s not going to be the fault of my anchor.

Have to agree with this and also chuckle at the Viking. It looks so very much like the Mantus, with the press out of the Excell and the holes that Steve of S/V Panope did to his manson (I think) that he modified, all topped off with the Viking knowledge base. Sound familiar?

[Lost Horizons]

Originally Posted by Mike OReilly

I base it on my experience, on the experience of most cruisers, and on basic physics.

Sorry, but there is a problem in your understanding Or interpretation of a “basic physics.” I have a hunch, you are not a physicist, are you, Mike? It is certainly easier to penetrate a substrate with a smaller object given an equal force. For this reason it is easier to drive a smaller nail into a wall than a large nail. For the same reason smaller caliber bullets have better penetrating capacity than larger caliber bullets given the same energy (e.g. 9mm v 45 ACP).

Anchor does not get buried by its weight, it is a tension of the rode that drives it into a bottom. Size is helpful for holding power, but has no advantage in setting the anchor and resetting it. The only advantage of a larger anchor with excessive holding power is when it is not properly set, which may occur in certain bottoms or with a short scope.

[Mike OReilly]

Originally Posted by Lost Horizons

Sorry, but there is a problem in your understanding Or interpretation of a “basic physics.” I have a hunch, you are not a physicist, are you, Mike? It is certainly easier to penetrate a substrate with a smaller object given an equal force. For this reason it is easier to drive a smaller nail into a wall than a large nail. For the same reason smaller caliber bullets have better penetrating capacity than larger caliber bullets given the same energy (e.g. 9mm v 45 ACP).

Anchor does not get buried by its weight, it is a tension of the rode that drives it into a bottom. Size is helpful for holding power, but has no advantage in setting the anchor and resetting it. The only advantage of a larger anchor with excessive holding power is when it is not properly set, which may occur in certain bottoms or with a short scope.

You're right. Not a physicist. I did study astro-physics in undergrad, up until turning to journalism where I then became a working science journalist for over 30 years. I'll let you decide if that gives me any credibility.

In your theoretical nail scenario, the force is concentrated in a much smaller area. This is why it penetrates easier. Same for the bullet. Same energy, conentrated in a smaller area.

But a light anchor sitting on the bottom does not create the same force on the tip that a smaller anchor does. You now, F=ma. The tip of a more massive anchor, where the force is concentrated, experiences a larger downward force compared to a smaller anchor.

This is partly why modern anchor designs use weighted points, sharp edges and roll bars. It's all about keeping the maximum force vector heading down.

In addition, as I (and others) have laid out, in the real world it's not simply a question of landing on a nice, flat sandy bottom. Often the anchor is penetrating weeds, debris and other gunk. Anyone with any experience knows a heavier anchor will do this easier than a smaller, lighter one.

[Lost Horizons]

Originally Posted by Mike OReilly

The tip of a more massive anchor, where the force is concentrated, experiences a larger downward force compared to a smaller anchor.

No, the force is the same and is determined only by the wind speed or engine’s RPM (for the sake of an argument, we will neglect water resistance). Smaller anchor will have smaller cross-section, just like a nail or a bullet, and therefore will be exerting higher pressure on the substrate. Consequently, it will go deeper with all other conditions being equal, including anchor design, off course.

[Lost Horizons]

Originally Posted by Mike OReilly

Anyone with any experience knows a heavier anchor will do this easier than a smaller, lighter one.

Citation is needed.