Anchors - Bigger is Better ?

[barnakiel]

OK.

So since the mass is related to the area (unless we spread very finely, which is often not the case with anchors), and we know the mass grows proportionately to volume, which in turn grows proportionately to the third power of size (linear size).

Then ensues the area grows with the ^2 of the linear size while the mass grows with the ^3. Roughly this can be expressed as:

For twice heavier an anchor = twice the mass = (1.26 linear growth requirement, because 1.26^3=2) = 1.58 x the area (because 1.26 linear growth entails 1.26x1.26 area growth) = 1.58 the holding power (all other things equal).

Twice heavier = 59% higher holding power.

50% heavier anchor gives 31% holding power gain.

Etc..

And someone above claimed we cannot calculate such things?

b.

[s/v Jedi]

Originally Posted by barnakiel

And someone above claimed we cannot calculate such things?

We have everything on CF. I personally know ex FBI, CIA, MI6, black ops (like pilots, they all seem to go sailing ), nuclear scientist, pharmaceutical scientists, brain surgeon, loads of public notaries, and many things I won't even mention. I'm just a wandering soul who remembers school, and rock star, gigolo etc.

[zeehag]

watched a guy try to set a rocna into a rock i was anchored on the other side of--lol..
he scraped my chain off that flat ish rock and couldnt figure out why his fancy 3000 usd anchor wouldnt set--he really didnt like my answer--to which he replied that he thought the bottom was all sand....when in reality the bottom here in west coast usa and mexico and canada is rocks with whatever around em..is still a young region, as compared with the east coast---we are sailing in a mountain range, much of which i sunder water.
some folks here use 2 anchors on one rode. some use 2 anchors, one bow and one stern...some use kellets
some stick just fine n dandy with their old stuff. no problem.

too heavy? if you can lug a 100 pound anchor onto your deck and your 28 ft boat doesnt sink under the load of that and chain, mebbe is ok, but i would think that could be too much ....
i use a 30 kg(64 pound) bruce with 194 ft chain for a 28000 pound displacement 41 ft boat. right now i have 165 ft on bottom, is 24 ft deep here with rocks and some silt vs sand and mud. good swell action--can be surfed just a few yards/meters from me...
my 45 pound cqr dragged anchor in mazatlan when i felt my chain fall off a ledge in a good breeze (25 kts) in silt over some mud allegedly sand and hardpan vs granite.
i love my bruce anchor.
what i learned from anchoring here is that i want 3 more 33 kg bruce anchors and a bunch more chain so i can anchor like an oil rig....

everything is able to be calculated by someone who plays with numbers....there is even mathematics for this...

[onestepcsy37]

cruising couple friends who did a rtw for eight years told me -

"you can always tell how long a boats' been out there by the size and number of their anchors; the longer they've been out, the bigger the anchors and the longer the chain"

i wonder how many of these 'classification societies' have actually done an rtw on a mid sized sailboat.....

[foggysail]

Originally Posted by barnakiel

OK.

So since the mass is related to the area (unless we spread very finely, which is often not the case with anchors), and we know the mass grows proportionately to volume, which in turn grows proportionately to the third power of size (linear size).

Then ensues the area grows with the ^2 of the linear size while the mass grows with the ^3. Roughly this can be expressed as:

For twice heavier an anchor = twice the mass = (1.26 linear growth requirement, because 1.26^3=2) = 1.58 x the area (because 1.26 linear growth entails 1.26x1.26 area growth) = 1.58 the holding power (all other things equal).

Twice heavier = 59% higher holding power.

50% heavier anchor gives 31% holding power gain.

Etc..

And someone above claimed we cannot calculate such things?

b.

I could not follow this. Mass = density X volume not related to surface area. And twice the weight does not have twice the holding power.

[DumnMad]

I follow you Barny and I agree with your ratios but holding power to area only applies to anchors at the same depth.
Shallow sand on hardpan you are right.
However in deep sand, double the depth = 4 times the holding power.
Therefore in sand or mud the diggier the better.

[JonJo]

Holding capacity will have much to do with how the anchor 'works' as to its surface area.

If the anchor simply digs in, with the shank basically near the surface the holding capacity will be much different to an anchor with the same surface area that has dived, say, 2' deep.

So a Fortress that might have the same surface area as a monster Bruce has the ability to develop a much higher holding capacity, becuase the Fortress will dive and the Bruce might not.

Equally a CQR, or Delta that does not, or seldom, dives but has a large mass for its surface area will never develop the same holding capacity as an Excel (which does dive).

[JonJo]

It is interesting that none of the respondents have any experience of 'recommended' sized smaller anchors. It seems as if they got rid of their old gen anchors, CQRs, Deltas, Bruces and immediately bought anchors much bigger, often 2 sizes bigger. No-one seems to have gone the intermediate step.

This might explain why everyone, well nearly, who has posted has no experience of smaller new gen anchors dragging - they have never tried them in anger. Which begs the question, how do they know that correctly sized new gen anchors would not hold?

The second interesting facet is that all the respondents are using concave anchors - obviously because they have no easy access to new gen convex anchors. And as far as I can make out no-one, who has posted, uses Fortress or Danforth either.

Its a pity we did not have some responses from convex (and Fortress) owners - but they are probably worried that if they become vociferous the thread will be closed

[JonJo]

Jedi,

Great images of Hurricanes.

But I'm not sure they prove that big is better. Multis flipping seems to be a function of multis, not anchors. The fact that yachts are destroyed is not necessarily proof that big is better, it might underline however that new (anchors) are better then old and that caution is better than blind faith in one anchor (no matter how good). I wonder how many of the destroyed yachts were sitting on one anchor, correctly sized, what happened to the owners who put out a web of correctly sized anchors and how many dared brave the hurricane(s) sitting only on one correctly or even over-sized anchor.

Your images and experience suggests - common sense and preparation is much of the key.

[Kenomac]

Originally Posted by JonJo

It is interesting that none of the respondents have any experience of 'recommended' sized smaller anchors. It seems as if they got rid of their old gen anchors, CQRs, Deltas, Bruces and immediately bought anchors much bigger, often 2 sizes bigger. No-one seems to have gone the intermediate step.

This might explain why everyone, well nearly, who has posted has no experience of smaller new gen anchors dragging - they have never tried them in anger. Which begs the question, how do they know that correctly sized new gen anchors would not hold?

The second interesting facet is that all the respondents are using concave anchors - obviously because they have no easy access to new gen convex anchors. And as far as I can make out no-one, who has posted, uses Fortress or Danforth either.

Its a pity we did not have some responses from convex (and Fortress) owners - but they are probably worried that if they become vociferous the thread will be closed

I started out using a manufacturers recommended Danforth on my Hunter, then moved up to a Rocna which was sized up X1. Used the Rocna for two years in various bottoms except for rock; only dragged once. I returned the Rocna because of the recall. I now use a 75 lb CQR on the Oyster (50,000 lb boat) and plan to add the 99 lb Ultra Anchor soon to compliment the CQR and Fortress 55. All 1/2 chain on 300 ft rode with snubber.

I seem to meet your qualifications. Used old and new, large and small at anchor 6 months/year. The bottom line, no anchor is perfect for every bottom; the Rocna didn't like grass or weed and would get clogged up with weed or not dig into grass, the CQR doesn't like grass, both were fine in mud and sand. Hopefully, the Ultra will perform better and dig faster in grass and weed.

I'm keeping my fingers crossed and also hanging on to all three anchors (Ultra, CQR and Fortress).

[s/v Jedi]

I surely hope nobody is using a Danforth or Fortress as their primary anchor while cruising away from the marina. So I find it not strange at all that nobody with these posted.

(yes, I have Fortress anchors but not as primary)

cheers,
Nick.

[JonJo]

Originally Posted by onestepcsy37

cruising couple friends who did a rtw for eight years told me -

"you can always tell how long a boats' been out there by the size and number of their anchors; the longer they've been out, the bigger the anchors and the longer the chain"

i wonder how many of these 'classification societies' have actually done an rtw on a mid sized sailboat.....

If you go into the visitors moorings in marinas in La Reunion, Seychelles and/or Mauritius you will see the world girdling yachts (just check the country of origin flags), yes they have lots of anchors, well 2 (on the bow rollers) but you will be lucky, ever, to see a single new gen anchor!

[JonJo]

Kenomac,

You obviously are smitten by the Ultra. Can I suggest you re-consider, quickly. Someone else has questioned your choice, but if you need stainless there is an option.

Spade make their bigger stainless anchors from a better stainless (I think from 2205 grade, you need to check, and also check when they start, ie size, to use the better grade). They will also sell the stainless models, maybe all of them, welded (if you do not like the jointed shank).

2205 has a yield strength of 450 MPa vs 205 MPa for 316. Doubling shank strength looks a no-brainer to me

[JonJo]

Jedi

Fortress are not aggressive in Oz, from your personal experience what's wrong with them?

[conachair]

Originally Posted by JonJo

It seems as if they got rid of their old gen anchors, CQRs, Deltas, Bruces and immediately bought anchors much bigger, often 2 sizes bigger.

Haven't cruisers always been using oversized anchors? With very little research apart from an occasional bar chat (remembering that cruisers only usually only talk about maintenance, nothing to do with sailing ) I get the impression a lot of people have got rid of their oversized old gen and replaced with an oversized new gen. I ditched the oversize cqr for an oversize rocna, having spent a lot of time at anchor since then I wouldn't hesitate going up another 5Kg were the clocks to go back, despite never having dragged, but in a tight short scope anchorage or a nasty squall coming out o nowhere it might just come in handy. Bering in mind we're talking about long distance cruising boats here which have to fend for themselves in a huge variety of circumstances possibly with nowhere to run to.