Advice on ground tackle

[Dockhead]

Originally Posted by smj

So what is the limit in size? Why have a 178lb Bruce instead of a 250lb Bruce?
And can you state with certainty that your large Bruce will hold you better in your 64’ monohull than our 45lb Mantus on our 6700lb 40’ cat? I don’t think so. . .

I think we can say with great certainty that Jedi's boat will be held better by 178 pounds of Bruce, than your boat is held by only 45 pounds of Mantus, even though the Mantus is definitely a better design and more effective, pound for pound, than the Bruce.


One thing just about everyone with the experience will confirm, is that anchors for some reason become disproportionately more effective with increasing size, and at about 100 pounds, start to behave in an apparently different and much better way.



Steve Dashew, with a huge amount of experience and knowledge, writes about this is some detail. With neither my previous 121 pounds Rocna nor my present 100 pound Spade, have I ever been unable to set the anchor with full power in reverse (100 hp Yanmar).



If I could handle a 250 pound anchor, I'm absolutely sure that this would be even another big leap better. Have you noticed how small big ships' anchors are compared to their displacement?



I'm sure a competent soil mechanics engineer could explain it, but anchor holding, and especially setting, doesn't scale linearly. I would never want another anchor under 100 pounds again on any boat. I downsized from 121 pounds only because the Rocna was unbalanced and awkward to handle. Probably a Spade that size would be have been ok, and maybe I will try one size bigger in the Spade later.



But 100 pounds has been very good. I once rode out a storm in 40+ meters of water on nearly 2:1 scope with it. In Greenland where there was almost no shelter and extremely steep-to bottom.

[smj]

Nice article by John Kettlewell.

https://oceannavigator.com/new-gen-anchors-are-now-gen/
Pretty much holds true from my experience. If you go old school then definitely go big to get decent holding. Of course if your windlass craps out…….

[Izikalvo]

https://www.practical-sailor.com/sai...anchor-holding

[Dockhead]

Originally Posted by Izikalvo

https://www.practical-sailor.com/sai...anchor-holding

Good article. I thought this was particularly interesting:

"During testing for a future report, we observed that anchors increase holding capacity over time, particularly if provided with resting periods of 20 minutes or more between hard pulls. The obvious a corollary is that an anchor that moves every few minutes is resting in weak, liquefied, churned up soil."

This could be one explanation for why larger/heavier anchors seem to hold disproportionately much better - this dynamic soil mechanics phenomenon .

[Izikalvo]

Originally Posted by Dockhead

Good article. I thought this was particularly interesting:

"During testing for a future report, we observed that anchors increase holding capacity over time, particularly if provided with resting periods of 20 minutes or more between hard pulls. The obvious a corollary is that an anchor that moves every few minutes is resting in weak, liquefied, churned up soil."

This could be one explanation for why larger/heavier anchors seem to hold disproportionately much better - this dynamic soil mechanics phenomenon .

"anchors increase holding capacity over time"
Indeed, no matter what size they are, a well-buried anchor performs better than a half-buried anchor.

I define 2 mechanisms that negate the idea that a large anchor is better than a small one. Larger anchors are more prone to tripping in a change of wind/tide and large anchors do not resist yawing as well as smaller anchors.
As the wind increases it is the windage of the yacht that determines the tension and that tension will be the same for a large or small anchor (for the same yacht). If the tension increases beyond the ultimate hold of too small of anchor then it will drag. However, as long as the anchor is not ridiculously small you will never exceed the hold of a sensibly sized small anchor (the size the manufacturer recommends). A 15kg efficient anchor, Spade, Viking (add whatever anchors you want) will develop hold in a clean sand seabed of about 2,000kg (Viking, even more). You will never experience a 2t tension in your rode - an 8mm G30 chain will begin to stretch at about 1,500kg. An anchor larger than the anchor maker's recommendation will have a higher ultimate hold - but your wife will sue for divorce long before you drag the small anchor and stretch the chain. Measurement suggests that at 35 knots the tension in the rode for a 45 Ft production yacht, actually, a Bavaria, will be about 650kg - a long long way from the ultimate hold of a good modern 15kg anchor of 2,000kg. It is unlikely many people will be anchored subject to the full fury of 35 knots (but possible). There is simply no need to increase the size of your anchor beyond the manufacturer's recommendation - and if you do go large possible self-inflicted harm might occur.

[SailFastTri]

Originally Posted by Izikalvo

"anchors increase holding capacity over time"
Indeed, no matter what size they are, a well-buried anchor performs better than a half-buried anchor.

I define 2 mechanisms that negate the idea that a large anchor is better than a small one. Larger anchors are more prone to tripping in a change of wind/tide and large anchors do not resist yawing as well as smaller anchors.
As the wind increases it is the windage of the yacht that determines the tension and that tension will be the same for a large or small anchor (for the same yacht). If the tension increases beyond the ultimate hold of too small of anchor then it will drag. However, as long as the anchor is not ridiculously small you will never exceed the hold of a sensibly sized small anchor (the size the manufacturer recommends). A 15kg efficient anchor, Spade, Viking (add whatever anchors you want) will develop hold in a clean sand seabed of about 2,000kg (Viking, even more). You will never experience a 2t tension in your rode - an 8mm G30 chain will begin to stretch at about 1,500kg. An anchor larger than the anchor maker's recommendation will have a higher ultimate hold - but your wife will sue for divorce long before you drag the small anchor and stretch the chain. Measurement suggests that at 35 knots the tension in the rode for a 45 Ft production yacht, actually, a Bavaria, will be about 650kg - a long long way from the ultimate hold of a good modern 15kg anchor of 2,000kg. It is unlikely many people will be anchored subject to the full fury of 35 knots (but possible). There is simply no need to increase the size of your anchor beyond the manufacturer's recommendation - and if you do go large possible self-inflicted harm might occur.

Are you just trying to stir the pot? In the real world it’s not like you describe. Yes, people do anchor over all kinds of bottoms in less than ideal circumstances in “the full fury” of storms, and no - small anchors do not resist better than their larger counterparts. In the real world, cruisers choose the best and largest anchors they can for good reasons.

[smj]

Originally Posted by SailFastTri

Are you just trying to stir the pot? In the real world it’s not like you describe. Yes, people do anchor over all kinds of bottoms in less than ideal circumstances in “the full fury” of storms, and no - small anchors do not resist better than their larger counterparts. In the real world, cruisers choose the best and largest anchors they can for good reasons.

Pretty much agree with you, but I think “largest” depends on the boat and the crew. I don’t want an anchor that is to heavy to be able to be handled manually by myself or my wife, in case the windlass craps out. We also have a performance lightweight catamaran so my focus is more on a better performing anchor rather than a heavy anchor. You will never see a CQR or Bruce hanging of our crossbeam no matter what weight.

[Muaddib1116]

On larger boats, that's sometimes not possible, even if the anchor is "only" the manufacturer's recommended size. Not a lot of people can manually haul up tens of meters of 10mm chain with a 30kg anchor at the end. So for some boats, you're looking at using deck winches as emergency backups, which you hope you'll never need to use. And if that's the case, it's barely any difference to go up to a 40 or 50kg anchor or something like that, since "manual" isn't really a factor.

[smj]

Originally Posted by Muaddib1116

On larger boats, that's sometimes not possible, even if the anchor is "only" the manufacturer's recommended size. Not a lot of people can manually haul up tens of meters of 10mm chain with a 30kg anchor at the end. So for some boats, you're looking at using deck winches as emergency backups, which you hope you'll never need to use. And if that's the case, it's barely any difference to go up to a 40 or 50kg anchor or something like that, since "manual" isn't really a factor.

Absolutely, and that’s part of our decision making process when we purchase a catamaran.

[s/v Jedi]

Originally Posted by Izikalvo

"anchors increase holding capacity over time"
Indeed, no matter what size they are, a well-buried anchor performs better than a half-buried anchor.

I define 2 mechanisms that negate the idea that a large anchor is better than a small one. Larger anchors are more prone to tripping in a change of wind/tide and large anchors do not resist yawing as well as smaller anchors.
As the wind increases it is the windage of the yacht that determines the tension and that tension will be the same for a large or small anchor (for the same yacht). If the tension increases beyond the ultimate hold of too small of anchor then it will drag. However, as long as the anchor is not ridiculously small you will never exceed the hold of a sensibly sized small anchor (the size the manufacturer recommends). A 15kg efficient anchor, Spade, Viking (add whatever anchors you want) will develop hold in a clean sand seabed of about 2,000kg (Viking, even more). You will never experience a 2t tension in your rode - an 8mm G30 chain will begin to stretch at about 1,500kg. An anchor larger than the anchor maker's recommendation will have a higher ultimate hold - but your wife will sue for divorce long before you drag the small anchor and stretch the chain. Measurement suggests that at 35 knots the tension in the rode for a 45 Ft production yacht, actually, a Bavaria, will be about 650kg - a long long way from the ultimate hold of a good modern 15kg anchor of 2,000kg. It is unlikely many people will be anchored subject to the full fury of 35 knots (but possible). There is simply no need to increase the size of your anchor beyond the manufacturer's recommendation - and if you do go large possible self-inflicted harm might occur.

In the best possible anchoring seabed, you are correct. But the real world isn’t like that, you will find soft mud more often than perfect sand. And the big anchor performs in soft mud like the small anchor would in much firmer bottom types, yet just gets pulled through the soft mud, letting you down.

I live with the negatives of a large anchor in a good sandy sea bed all the time. It means that when a blow is forecast after changing wind directions, I will pickup my anchor and re-set it in the direction of the expected blow. It takes me 15 minutes unless I also choose to anchor in another part of the bay that will be more protected, in which case it takes me 30 minutes.
The boats with small anchors take many times as long to pickup their anchors and move to mooring balls in inner harbors or even go into marinas, paying big dollars for slips to “ride out the storm”. Apparently they don’t have much faith in their anchor

[Muaddib1116]

Originally Posted by Izikalvo

It is unlikely many people will be anchored subject to the full fury of 35 knots (but possible).

This doesn't seem like an incredibly unlikely event.

[s/v Jedi]

Originally Posted by Muaddib1116

This doesn't seem like an incredibly unlikely event.

Indeed, we have 60+ kts every year. Last time we had 2 big fronts, the first one gusting to 74kts, the second 65kts.

All but one power boat that stayed at anchor were just fine. Boats that moved to moorings dragged them around, hitting each other and even boats in marinas reported damage.

We all just sat at anchor and an hour or so later, as the storm had passed, enjoyed nature while adding more experience

[rslifkin]

Originally Posted by Muaddib1116

This doesn't seem like an incredibly unlikely event.

Agreed. I've anchored for the night in 25 gusting to 35 instead of being at the dock quite willingly. And I sized my gear for sitting out a solid 50-60 kt thunderstorm somewhere with sub optimal holding. That's far from an impossible scenario around here.

[Anders]

Originally Posted by Izikalvo

"anchors increase holding capacity over time"
Indeed, no matter what size they are, a well-buried anchor performs better than a half-buried anchor.

I define 2 mechanisms that negate the idea that a large anchor is better than a small one. Larger anchors are more prone to tripping in a change of wind/tide and large anchors do not resist yawing as well as smaller anchors.
As the wind increases it is the windage of the yacht that determines the tension and that tension will be the same for a large or small anchor (for the same yacht). If the tension increases beyond the ultimate hold of too small of anchor then it will drag. However, as long as the anchor is not ridiculously small you will never exceed the hold of a sensibly sized small anchor (the size the manufacturer recommends). A 15kg efficient anchor, Spade, Viking (add whatever anchors you want) will develop hold in a clean sand seabed of about 2,000kg (Viking, even more). You will never experience a 2t tension in your rode - an 8mm G30 chain will begin to stretch at about 1,500kg. An anchor larger than the anchor maker's recommendation will have a higher ultimate hold - but your wife will sue for divorce long before you drag the small anchor and stretch the chain. Measurement suggests that at 35 knots the tension in the rode for a 45 Ft production yacht, actually, a Bavaria, will be about 650kg - a long long way from the ultimate hold of a good modern 15kg anchor of 2,000kg. It is unlikely many people will be anchored subject to the full fury of 35 knots (but possible). There is simply no need to increase the size of your anchor beyond the manufacturer's recommendation - and if you do go large possible self-inflicted harm might occur.

35 knots is not that much and I would expect most here to have or will experience a lot more.
A small anchor will hold in good bottoms, even my old small CQR held during an extremely nasty winter storm but we were anchored in very thick mud.
Marginal bottoms like soft mud is a different story and thats when I want a big new gen anchor.

[Dockhead]

Originally Posted by Izikalvo

"anchors increase holding capacity over time"
Indeed, no matter what size they are, a well-buried anchor performs better than a half-buried anchor.

I define 2 mechanisms that negate the idea that a large anchor is better than a small one. Larger anchors are more prone to tripping in a change of wind/tide and large anchors do not resist yawing as well as smaller anchors.
As the wind increases it is the windage of the yacht that determines the tension and that tension will be the same for a large or small anchor (for the same yacht). If the tension increases beyond the ultimate hold of too small of anchor then it will drag. However, as long as the anchor is not ridiculously small you will never exceed the hold of a sensibly sized small anchor (the size the manufacturer recommends). A 15kg efficient anchor, Spade, Viking (add whatever anchors you want) will develop hold in a clean sand seabed of about 2,000kg (Viking, even more). You will never experience a 2t tension in your rode - an 8mm G30 chain will begin to stretch at about 1,500kg. An anchor larger than the anchor maker's recommendation will have a higher ultimate hold - but your wife will sue for divorce long before you drag the small anchor and stretch the chain. Measurement suggests that at 35 knots the tension in the rode for a 45 Ft production yacht, actually, a Bavaria, will be about 650kg - a long long way from the ultimate hold of a good modern 15kg anchor of 2,000kg. It is unlikely many people will be anchored subject to the full fury of 35 knots (but possible). There is simply no need to increase the size of your anchor beyond the manufacturer's recommendation - and if you do go large possible self-inflicted harm might occur.

"It is unlikely many people will be anchored subject to the full fury of 35 knots (but possible)" What?! Where do you get this? I was just two days ago subject to 40+ knots of wind overnight at anchor. I've been through nights at anchor in hurricane force winds, and this is not an exceptional experience for long-term cruisers.

And why would larger anchors be "more prone to tripping in a change of wind/tide and large anchors do not resist yawing as well as smaller anchors." This is utter nonsense.

The very article you cited says why. The bigger the anchor, the less it will move around in the seabed, and the better the soil will retain its integrity and therefore holding.

Every cruiser with a modicum of experience knows that bigger is better, and disproportionately so. When people start to laugh at the size of the anchor in your roller, is when you know you are approaching the optimum size. I think it was Dashew who said that, and no one knows more about anchoring.


The manufacturers' recommendations are only good up to a certain wind force and in optimal holding -- will that be enough? If you are a weekend sailor who anchors rarely, and is never far from a safe harbour, then sure. But that is not the use case of many of us. The rest of us need to be ready for dealing with strong conditions and less than optimal holding. To be sure that you can manage in that, you really want the biggest anchor you can carry.