Anchor choices

[kmacdonald]

Originally Posted by rslifkin

You keep providing this potentially dangerous advice, but you fail to back it up with any facts. Please explain exactly what's wrong with oversizing? Yes, you carry extra weight around, but in the grand scheme of things, it's not all that much. And you can likely save more than that by switching to lighter, higher strength chain or other changes.

Plus, in some cases the manufacturer is conservative with their sizing, in other cases they're not at all. As an example, I'd expect the Delta sizing chart is based on a good bottom and very little wind. They seem to love the idea that a peanut will hold a supertanker in place, which just isn't the case.

IMHO. If a 35lb new gen anchor doesn't hold a 45lb one wouldn't hold either. Maybe a 75lb one would. You just cant reasonably upsize to make a difference. I've had many boats and anchors and none of them hold all the time in all conditions. Set an anchor alarm or put your wife on anchor watch!

[rslifkin]

Originally Posted by kmacdonald

IMHO. If a 35lb new gen anchor doesn't hold a 45lb one wouldn't hold either. Maybe a 75lb one would. You just cant reasonably upsize to make a difference. I've had many boats and anchors and none of them hold all the time in all conditions. Set an anchor alarm or put your wife on anchor watch!

That's not a reason for not oversizing. Yes, there will be situations where due to bottom conditions and weather, you just can't get enough holding power even with something a size or 2 bigger. But there are plenty of other situations where a 20% heavier anchor will work better (which will set more easily due to increased weight and also have more surface area for more holding power once set). And even if the smaller anchor holds well enough, you could use less scope if desired with a bigger one (less scope reduces holding power, but if you start with more holding power, you can reduce it further before it becomes inadequate).

[thinwater]

Originally Posted by rslifkin

You keep providing this potentially dangerous advice, but you fail to back it up with any facts....

And you have not provided facts either. Just sayin'. And that's OK, it's just a forum. What is true is that Rocna and Mantus have long stated that their sizing is conservative. It is also well known that pivoting fluke anchors are less stable in firm bottoms if oversized (although this latter observation is off topic). As for Delta sizing, I thought we were only discussing Mantus, Rocna, and Spade. Yeah, you'd need a big Delta (I had one).

[Rocna]
Our Anchor Sizing is Conservative

Unlike other manufacturers, our anchor sizing recommendations are intended to provide an anchor adequate for use in most all conditions. We base our calculations on 50 knots of wind, associated surge, and poor holding bottoms. For more on our philosophy and rationale, please consult our Knowledge Base article on our sizing recommendations.

---

I'd just leave it alone. Kmac only repeated what Rocna stated. He did not suggested down sizing the anchor, so calling his suggestion to follow manufacture advice dangerous is unfairly critical. You are obviously free to go big and I will not criticize that choice.

[Mike OReilly]

Most experienced cruisers opt for some version of going over-sized. My suggestion and approach is to go with the largest scoop-style (new-gen) anchor your boat and crew can reasonably manage.

I do think it's possible to go too big. If your bower is so large as to dissuade you from re-anchoring when need be, or if it becomes a significant burden just to haul up in difficult conditions, then your bower may be too big.

But if your boat's anchor system, and your crew, can manage a larger anchor without undue effort, then it makes no sense to go smaller.

[rslifkin]

There is definitely a point where you could go so big that you won't get the anchor to set properly in a firm bottom, particularly with something like a Danforth / Fortress that's at risk of pulling out in a shift or fouling the chain if it's not set deeply enough. But I don't think that's much of a concern unless you have a very underpowered boat. You're more likely to have an issue along those lines from not setting it well than from the anchor actually being too big.

In most cases, you'll hit the limit of what fits on the boat before that becomes a problem, as people like a64pilot have proven with his successful use of a 40kg Rocna on a 38 foot boat.

[noelex 77]

Originally Posted by kmacdonald

IMHO. If a 35lb new gen anchor doesn't hold a 45lb one wouldn't hold either. Maybe a 75lb one would. You just cant reasonably upsize to make a difference. I've had many boats and anchors and none of them hold all the time in all conditions. Set an anchor alarm or put your wife on anchor watch!

The relationship between anchor holding ability and size is reasonably well established. In most substrates it is roughly proportional to the weight (assuming identical design and construction materials).

So a 45lb anchor could be expected to have just under 30% more holding power than an otherwise identical 35lb model.

Especially in these days of electric anchor winches, it is a significant gain for a very small amount of extra weight, particularly considering the small percentage increase in total ground tackle weight including both the anchor and chain.

I agree, always use an anchor alarm, why not?

As a parting thought, perhaps that extra 10 lb incorporated into the anchor may allow you to spend a few more nights with your wife .

[GRIT]

Originally Posted by rslifkin

There is definitely a point where you could go so big that you won't get the anchor to set properly in a firm bottom, particularly with something like a Danforth / Fortress that's at risk of pulling out in a shift or fouling the chain if it's not set deeply enough. But I don't think that's much of a concern unless you have a very underpowered boat. You're more likely to have an issue along those lines from not setting it well than from the anchor actually being too big.

In most cases, you'll hit the limit of what fits on the boat before that becomes a problem, as people like a64pilot have proven with his successful use of a 40kg Rocna on a 38 foot boat.

I don't intend to pick on you, since I've heard many say this before you. But when, exactly, is an anchor too big? If your gear can handle it, and the boat can handle it, how can you be too big?

My logic is this:

A 2 tonne anchor will certainly hold a 50 foot cat, as will a 1 tonne anchor, as will a 100kg anchor, as will the recommended 30kg anchor (let's say we're talking about a spade anchor).

So, my guess is that those sharing your opinion on "too large" anchors will choose (from my list) the 100kg anchor, as the one that's reasonably "too big".

If I can't generate enough power to set the anchor, how much wind must blow to get the boat to drag said anchor?

What if you're engineless, or underpowered? If you are too underpowered to properly set the anchor, then by the same logic as your original post, a 30kg anchor is too large as well. Yet 30kg would be what's recommended by Spade anchors. Going to a 10kg would seem foolhardy, even if that's all your engine can "set".

If my engines can't set the anchor, and it takes 50 knots to generate enough "pull" to set that 100kg anchor, don't you think it'll set when the wind picks up? I mean, it's not as good as a controlled pull, but if it takes 50 knots to set it, it's likely you've had 50 knot gusts, long before you get the 80 knot gusts required to unsettle the "unset" anchor.

The 2 tonne, or 1 tonne anchors are exagerations, but can you possibly see a 50 foot cat dragging them? If you could move them at all, don't you think their sheer weight would set them enough to hold a 50 foot cat? Or if the wind shifts, can you imagine what it would take to drag them, even if "unset"?

Remembering, of course, that cruisers in the 1970's would often "set" the anchor with the wind, and let it slowly dig it's way down, using wave action and the gentle tugs associated with such.

So, after that ramble, could someone please tell me how big they consider too big? Assuming one can lift it, transport it, store it... how can it be too big to dig?

Cheers all.
Paul.

50 Foot cat, 60kg SPADE anchor, 1700w windlass, 10mm chain, and sleeping well at anchor.

[rslifkin]

Defining a size for "too big" probably requires testing and data that's not available to us. As far as the "too big" anchor setting properly once enough wind is applied, yes, I'd expect that to happen. The concern is more around what happens if you get a current or wind reversal before that, where it'll be easier for the chain to foul it and easier to pull it out on a reversal when it's not dug in well.

Personally, I figure that for most boats, you'd have to make some serious modifications to the roller assembly, etc. to actually carry and use an anchor that would prove too big, so it's generally not worth worrying about it much. I know that the 33kg Rocna Vulcan I just mounted on my bow won't be too big (one size above the recommended 25kg), and anything bigger won't fit without moving the roller and other significant modifications anyway.

[GRIT]

Fouling... Good point!

That's the best answer to that question I've heard yet.

Thanks.
Paul.

PS, I don't know how I did it, but I intended to quote KMacdonald... Regards "don't oversize, the manufacturer already did that for you".

Apologies to RSLIFKIN, who was rebutting the same post...

[kmacdonald]

Originally Posted by noelex 77

As a parting thought, perhaps that extra 10 lb incorporated into the anchor may allow you to spend a few more nights with your wife .

Not if you dont have a windlass and it's her job to pull it up. Heck, you know I have a heart condition. Save every ounce you can and take the advice of those that have done the most research, the new gen anchor manufacturers.

[Mike OReilly]

Originally Posted by kmacdonald

Not if you dont have a windlass and it's her job to pull it up. Heck, you know I have a heart condition. Save every ounce you can and take the advice of those that have done the most research, the new gen anchor manufacturers.

Given these requirements and limitations, it's also possible the recommended size from the manufacturers is going to be too big for your boat and crew. So logically the best you can do is get the largest anchor you can manage -- as per the recommendations.

[rslifkin]

Originally Posted by kmacdonald

Not if you dont have a windlass and it's her job to pull it up. Heck, you know I have a heart condition. Save every ounce you can and take the advice of those that have done the most research, the new gen anchor manufacturers.

Not having a windlass is a specific use case where you're absolutely limited in how much ground tackle weight you can manage. In that situation, you have to plan a bit differently and in some cases make some performance compromises to keep the system manageable. Personally, I'd be using G70 chain in that situation to keep chain weight to a minimum and things like that.

On the other hand, for a setup like the one I just put together where the windlass can drop the anchor without manual intervention and can safely pull it all the way in, an extra few pounds has no impact on anchor handling.

[noelex 77]

Originally Posted by kmacdonald

Not if you dont have a windlass and it's her job to pull it up. Heck, you know I have a heart condition. Save every ounce you can and take the advice of those that have done the most research, the new gen anchor manufacturers.

Yes, I agree if you do not have a windlass then reducing anchor and chain weight is critical. I have cruised for many years in smaller yachts without a windlass so I understand the issues.

However, it is important to realise the restrictions this sometimes imposes. That does not mean you cannot have great time, but if you have limited anchor size and chain length this places some extra constraints on where and/or what anchoring conditions can be safely utilised.

It is not sensible to impose these same limitations for boats that can manage heavier anchors with just the push of a button.

[kmacdonald]

Yes, we will all have unique requirement and considerations. One size wont fit everyone.

[Mike OReilly]

Originally Posted by kmacdonald

Yes, we will all have unique requirement and considerations. One size wont fit everyone.

Which is exactly what the recommendation: go with the largest your boat and crew can manage, does. It's specifically not a one-size-fits-all approach, unlike simply following the manufacture's recommendation.