Upsizing anchor - suggestions?

[Dockhead]

Originally Posted by thomm225

6:1 ?

Why not let out more scope? Or was your rode not long enough?

I like 8 or 10:1 for my 20 lbs CQR which has held my boat (6600 lb displacement) the last 10 years in waves and winds to 30 knots. Gust to 45.

A decent anchor doesn't need much more than 5:1. Last time I was at anchor, I was on 2.5:1, and I've been through storms on less than 2:1 (in VERY deep water).

If you're going to use an old concrete block, or a CQR, as an anchor, however, 10:1 might improve your odds.

In the right bottom, an old concrete block may do just fine. It's in less than perfect conditions that a good anchor pays its way.

[Cheechako]

My take on chain is that it DOES produce a catenary much of the time. Remarkably so, beyond what I suspected. I concluded this by observing it, snorkeling while anchored in strong wind.
One example in the Tobago Keys; The wind was blowing very hard an average of probably 30 mph, gusting to 37 or so. Our Lagoon 42 catamaran was anchored in less than 15 ft of water but had no wave action at all as we were encircled in the anchorage by protection. We had 75 feet of chain out.
Snorkeling the anchor, we observed that it had pulled deeply into the coarse sand bottom. There was a short furrow where the Delta had plowed for maybe 5-6 ft over a few hours of this wind. The entire anchor was buried shank and all. While I was in the water the chain had probably about 8"+ of catenary in it the entire time, even during the gusts.

That catenary is a like a spring or a cushion. Plain strong wind in a good bottom normally will not pull an anchor out. A bow bouncing up and down heavily will jerk an anchor out when the chain snubs up bar tight if your snubber is strong! It's the water action that has the force.

We snorkeled the anchor many times, there was always catenary.

The other advantage is the angle with which long chain presents the anchor to the bottom. Similar to using a kellet. Thus helping to keep the anchor shank parallel to the bottom rather than angled up toward the surface.

[250224]

Originally Posted by soopad00pa

I guess my current plan, based on what I've read and being cheap, is to start with the chain. If that doesn't do it, it doesn't seem like more chain will be a waste of cash.

It's perfectly adequate imho. I had a 10 kg Rocna (and before Bruce) in tidal waters and they worked fine. I'd go with more chain (100 feet) and a y-nylon-snubber. Who knows one day a nice second hand anchor might appear and 12 or 15 kg is certainly more save (triple jabs...). The mark? I don't think that matters (too) much. Rocna is certainly nice.

The good thing is that your anchor alarm worked and you acted on it. And from your post it doesn't seem that you will be out on really really bad weather.

[thomm225]

Originally Posted by Dockhead

A decent anchor doesn't need much more than 5:1. Last time I was at anchor, I was on 2.5:1, and I've been through storms on less than 2:1 (in VERY deep water).

If you're going to use an old concrete block, or a CQR, as an anchor, however, 10:1 might improve your odds.

In the right bottom, an old concrete block may do just fine. It's in less than perfect conditions that a good anchor pays its way.

Yeah, my good anchor has paid it's way many, many times, and I got it with the boat and it's other 4 anchors for the boat's $2,000 purchase price.

The boat also came with a new spare 40' heavy chain and 300' of nylon rode which I just hooked up to the CQR after 10 years using it's original chain and nylon rode.

As for the amount of scope, that's just an old habit when I have enough rode.

Some of my boats in the past though only had 2'-5' of chain and 50'-75' of some old rope rode which worked out because we usually fished in 35' or so depth.

We didn't have depth finder so if we misjudged we'd be in the 80' channel and knew we had to move out a bit more towards Watts Island.

http://coastmariner.com/bin/chart2.p...941&locId=2223

[soopad00pa]

I really wanted that 30:1 scope on a 5# mushroom, but there were other things to consider in the area.

Like I said, I'm a noob and it's 90% likely that it held for the 12h or so before the drag in spite of me screwing up.

I agree wholeheartedly with better technique and anchorage selection, but as an American I believe in buying a quick fix!

[thinwater]

Originally Posted by Dockhead

... Dashew is a great expert, with more experience than all the rest of us combined....

Yes, and at the same time, a resounding no.

Dashew has more experience in big boats than most of us. In 30-foot AWBs, not so much, or at least that is not what he is reporting on lately.

The anchoring dynamics of a 30-foot AWB, a 60- 80-foot yacht, and a ship are three different things. The first is influenced heavily by waves, the last not at all by waves. This makes a big difference in rode dynamics and in what is practical to handle.

Each of us is limited to the boats we have either owned or cruised on extensively. The OPs boat is small and he has no windlass.


---


My advise for the OP at this time is more practice.

* 6:1 scope is not enough for rope, since there is no catenary. Holding will be only about 50%.
* Power set. Some will argue this is not always needed, but that is after gaining experience. Power setting is a great way for a beginner to learn about the bottom. With rope rode, ALWAYS power set at 10:1 scope, because the chain will lift. Then shorten up a little if you need to, but not less than 7:1 with rope. The peanut gallery may disagree. Ignore them, because they are using chain.
* Yup, chain is a good idea around coral, but it is a pain without a windlass. You won't need chain in the Chesapeake, but in Florida it's smart. But you only need 100 feet of chain, because the water is not that deep, and if it is deep, the rest can be rope (it won't be on the bottom).


Practice, Practice, Practice. 10kg Rocna is enough for a lightish 30-foot mono. Hell, I have a 12-pound aluminum Excel with 6-feet of chain on my 24-foot tri, but I've been doing this a long time. I have a 35-pound Manson on the 34-foot cat with 100-feet of chain, but it has a LOT more windage then a 30-foot mono, and it has a windlass to handle the chain.

[rslifkin]

Originally Posted by thinwater

Yes, and at the same time, a resounding no.

Dashew has more experience in big boats than most of us. In 30-foot AWBs, not so much, or at least that is not what he is reporting on lately.

The anchoring dynamics of a 30-foot AWB, a 60- 80-foot yacht, and a ship are three different things. The first is influenced heavily by waves, the last not at all by waves. This makes a big difference in rode dynamics and in what is practical to handle.

Each of us is limited to the boats we have either owned or cruised on extensively. The OPs boat is small and he has no windlass.

Another big factor is that boats gain weight (and weight capacity) faster than windage as size increases. Hence the reduced effect of waves. But that also means that you can't just down-size the same gear and expect it to work.

The concepts still apply, but a 30 footer with half the windage of a 40 footer may need more than half the holding power. Yet the 30 footer may only be able to comfortably carry 1/3 the weight in ground tackle that the 40 footer can. That makes picking a really solid setup for a smaller boat challenging at times.

[seandepagnier]

Originally Posted by Dockhead

A decent anchor doesn't need much more than 5:1. Last time I was at anchor, I was on 2.5:1, and I've been through storms on less than 2:1 (in VERY deep water).

This is interesting feedback but what type of anchor? How deep? Did the chain pull tight?

I dragged with a 15kg rocna with only 5:1 scope (maybe it was 4:1) when there was a strong gust (spray flying so I figure above 40 knots)

There are a lot of factors. Pulling chain tight from wind allows waves to break it loose.

The obvious option is more scope. If this is not an option a cheap way is to put weight along the chain, or even run two anchors in series. The best option is a larger anchor. The 15kg rocna has I recall about twice the holding power of the 10kg?

The 15kg is a lot harder to pull up if its well set, however, it is generally easy to break loose just by pulling it tight and raising the sails. If there is not much wind , surprisingly I could break it loose using the sculling oar a lot easier than manually pulling on the chain. It is also not that difficult to walk back to a sheet winch and crank it a few times.

The rocna type anchors are not scaled up equally, each is a new design, so the holding power is not linear with weight or even related to an exponential power based on mass but had to be determined from tests.

What about an aluminum rocna design? This would allow us to double the size of the anchor for the same weight....

[rslifkin]

Originally Posted by seandepagnier

This is interesting feedback but what type of anchor? How deep? Did the chain pull tight?

I dragged with a 15kg rocna with only 5:1 scope (maybe it was 4:1) when there was a strong gust (spray flying so I figure above 40 knots)

There are a lot of factors. Pulling chain tight from wind allows waves to break it loose.

The obvious option is more scope. If this is not an option a cheap way is to put weight along the chain, or even run two anchors in series. The best option is a larger anchor. The 15kg rocna has I recall about twice the holding power of the 10kg?

The 15kg is a lot harder to pull up if its well set, however, it is generally easy to break loose just by pulling it tight and raising the sails. If there is not much wind , surprisingly I could break it loose using the sculling oar a lot easier than manually pulling on the chain. It is also not that difficult to walk back to a sheet winch and crank it a few times.

The rocna type anchors are not scaled up equally, each is a new design, so the holding power is not linear with weight or even related to an exponential power based on mass but had to be determined from tests.

What about an aluminum rocna design? This would allow us to double the size of the anchor for the same weight....

Very deep water changes the game. An equal length / weight of chain deployed is much harder to pull tight in 100 feet of water than in 15 feet of water. In deep water, catenary provides a significant benefit. In shallower water, not so much (hence the need for big anchors to resist the higher angle of pull, good snubbers to add stretch, etc.). Dockhead is also running moderately heavy chain relative to the size of his boat. I think he's using 1/2", while I would probably go for high strength 3/8" on that size boat.

[seandepagnier]

Originally Posted by rslifkin

Another big factor is that boats gain weight (and weight capacity) faster than windage as size increases. Hence the reduced effect of waves. But that also means that you can't just down-size the same gear and expect it to work.

So what you are saying is true of smaller waves given two sizes of boat, but as the wavelength approaches the boats length the forces l get larger relative to the larger boat (resonant frequency) Generally this is bad to have waves this size at anchor but it happens.

The concepts still apply, but a 30 footer with half the windage of a 40 footer may need more than half the holding power. Yet the 30 footer may only be able to comfortably carry 1/3 the weight in ground tackle that the 40 footer can. That makes picking a really solid setup for a smaller boat challenging at times.

Also consider it is much easier to deal with 30 foot boat on the beach than 40 foot boat so better the larger boats dont drag as much.

[seandepagnier]

Originally Posted by rslifkin

Very deep water changes the game. An equal length / weight of chain deployed is much harder to pull tight in 100 feet of water than in 15 feet of water. In deep water, catenary provides a significant benefit. In shallower water, not so much (hence the need for big anchors to resist the higher angle of pull, good snubbers to add stretch, etc.). Dockhead is also running moderately heavy chain relative to the size of his boat. I think he's using 1/2", while I would probably go for high strength 3/8" on that size boat.

I used to use 3/8" on my 27 ft boat so I understand this, however.. anchoring in wellington new zealand, in 30ft of water, it would just pull the chain tight and the waves would break it loose. There were times the wind was very strong and also 4-5ft waves at anchor and the boat would 'submarine' and even then it usually held anchor.

In any case.. I think it's well proven that the money and weight is best spent in the anchor, not the chain. I have never paid money for anchor chain though.

[Panope]

Originally Posted by soopad00pa

Wind wasn't high at all. Maybe 15 with occasional gusts to 20.

In my opinion, this is poor performance, even considering the short chain and 6;1 scope.

Assuming the anchor was not obstructed by a foreign object, then I say your best course of action is to get a different anchor model.

Not a heavier anchor. Not more chain.

Others have suggested using more chain, but this will only double holding power at best.

Others have suggested increasing the size of the anchor from 10 to 15 kgs., but this will only increase holding by about 50%.

What is needed, is an increase in holding power of many times. Correct me if I am wrong, but your area receives frequent T-storms/squalls with winds of 40+ knots). 40 knots winds exert 4X as much force as 20 knots winds. In some seabeds, I have found Rollbar Rocna anchors to have (strait line) holding power several times less than many other types.

On the other hand, It is equally possible that your dragging event was caused by the anchor becoming clogged with seabed and not resetting. Again, I believe this is a problem that is best solved by getting an anchor that is less susceptible fouling.

Longer chain does have the effect of anchors tending to ROTATE and remain engaged (a good thing), while short chain rodes tend to result in anchors that RELEASE from the seabed during direction of pull reversals.

Your dragging event could have been caused by: Poor straight line holding, inability to reset, foreign object interference, or some other calamity. We will likely never know which is the real culprit, so take all advice with a grain of salt.

Steve

[Scottindo]

It’s length of chain that holds anchor in place good practice always put out at least 30 metres chain with a decent size anchor if it blows up over 30 knots then put out 40 metres chain or more as wind increases
Good ground tackle is most important part over wise you could lose your boat
Also make sure anchor is set correctly with reversing back on anchor boat and make sure you have enough swing room from other boats and shore etc
I personally carry on my 40 ft mono 80 metres 10mm
Chain and 35 kg Sarca XL anchor
That gives me good peace of mind
Always better to overkill as elements are brutal !!!

[Don C L]

Take mine with a grain of salt too, because I don't use any of those anchors, but given what I have seen in Steve's videos, I am not surprised the 10kg Rocna dragged. It certainly could be it was fouled on debris, that happened to me the only time I dragged (so far) with a CQR. If it were me, given what I have seen in Steve's videos, and given the choices you mention, I'd go with the 15kg Spade and 100' of 1/4" G4 chain (that is what I am using for my 8K lb boat.) I think you can still hand pull that, at least I do and I ain't no Andre the Giant.

edit: oops I see you said Vulcan not Spade. I believe the Vulcan showed better performance than Rocna in the videos.

[Uncle Bob]

Hi, I would take a long hard look at an excel on Steve's videos, I have found that it solved my Rocna dragging problems nicely.