An unlucky Vulcan

[s/v Jedi]

Originally Posted by Sonosailor

This idea of setting the anchor with 3:1 or less (from the roller): Draw it out to scale, and then look at the angle at the anchor. You are still pulling up on the anchor shaft and thereby pulling the fluke(s) in at a more shallow angle. It will be an inferior set! Then, leaving it at 3:1 while gusts pull and waves lift the bow may cause the anchor to ratchet back. This is what I mean by visualizing what you are doing.

The Bruce anchor was designed for 3:1 scope. We sit comfortably at 3:1 scope with 60+ knots of wind.

[rslifkin]

Originally Posted by Sonosailor

This idea of setting the anchor with 3:1 or less (from the roller): Draw it out to scale, and then look at the angle at the anchor. You are still pulling up on the anchor shaft and thereby pulling the fluke(s) in at a more shallow angle. It will be an inferior set! Then, leaving it at 3:1 while gusts pull and waves lift the bow may cause the anchor to ratchet back. This is what I mean by visualizing what you are doing.

Yes, and that is why there's less holding power at shorter scopes. But if you start the set gently and aren't in really shallow water (where such as short scope would be inadequate), it's not all that big an issue for many anchor designs. During the initial part of the set, the angle the anchor sees to the chain is lower, as there's significant sag in the chain. It's only as you pull harder later in the set that the angle increases significantly and by that point the anchor is hopefully embedded enough in the bottom to continue digging in and setting (although maybe not as deeply as it would with more scope).

In addition, different anchor designs will have more or less tolerance for high angles during setting.

[Lodesman]

Originally Posted by s/v Jedi

The Bruce anchor was designed for 3:1 scope. We sit comfortably at 3:1 scope with 60+ knots of wind.

Wasn't the Bruce designed for oil rigs?

[Panope]

Originally Posted by Sonosailor

This idea of setting the anchor with 3:1 or less (from the roller): Draw it out to scale, and then look at the angle at the anchor. You are still pulling up on the anchor shaft and thereby pulling the fluke(s) in at a more shallow angle. It will be an inferior set! Then, leaving it at 3:1 while gusts pull and waves lift the bow may cause the anchor to ratchet back. This is what I mean by visualizing what you are doing.

Sonosailor,

Your comment is accurate when in shallow water OR when using a mostly rope rode.

However, many boaters anchor in deeper water and with longer chains.

In this photo, 105 feet of 3/8" BBB Chain is set at 3.5:1 scope (30' "depth"). With 300 pounds of force, the angle of pull at the anchor is ZERO DEGREES above horizonal.

In this situation, most 35ft auxiliary sailboats lack sufficient reverse thrust to be able to lift the chain above horizonal, at the anchor.

(a steel chain in salt water will weight about 13% less than in the air. Error acknowledged)

[noelex 77]

Originally Posted by Sonosailor

This idea of setting the anchor with 3:1 or less (from the roller): Draw it out to scale, and then look at the angle at the anchor. You are still pulling up on the anchor shaft and thereby pulling the fluke(s) in at a more shallow angle. It will be an inferior set! Then, leaving it at 3:1 while gusts pull and waves lift the bow may cause the anchor to ratchet back. This is what I mean by visualizing what you are doing.

It should not be an issue for a good modern anchor in a reasonable water depth and substrate to set well at 3:1 as can be seen on this video I filmed many years ago of a Mantus M1 setting at 3:1 in 4.4m (14 feet).

https://www.youtube.com/watch?v=Ykoc7UyDezA

[Sonosailor]

Folks: I am sitting in my little boat, in Grand Anse D’Arlet, watching one boat after another come in between the snorkelling turtle watchers, drop 3:1 or less, and drag their anchor hundreds of feet back out to sea, ripping up the turtle grass that brings them all here in the first place. They try again and again, plowing long cuts; each time varying only where they start. Why do we think we can do the same thing and get different results? Why are we so closed to advice? What a stupid species we are. They each do it until they either grab some random coral or end up in another anchorage, or get so close to shore their method works. Then we watch out for them - sometimes picking our anchors up from behind them and move. No sense talking to them. Where are you in this?

[Panope]

How deep is the water?

How much chain are they using?

[Sonosailor]

Originally Posted by Panope

How deep is the water?

How much chain are they using?

It is all reasonably shallow. They start in 16’, drag it to 30’, then come back. They typically have 3:1 or less, but not too much less.

I’ll tell you this if you are willing to listen: Using less than 5:1 can cut into your drinking time!!!

What the **** is all that chain in your locker for?

[Panope]

Originally Posted by Sonosailor

It is all reasonably shallow. They start in 16’, drag it to 30’, then come back. They typically have 3:1 or less, but not too much less.

I’ll tell you this if you are willing to listen: Using less than 5:1 can cut into your drinking time!!!

What the **** is all that chain in your locker for?

I agree that 16' is too shallow for 3:1 scope. It would have been very helpful if you had mentioned the water depth sooner.

I am listening to every word that you are saying. I believe that the disagreement that you and I may be having is due to your not understanding or at least acknowledging the fact that the needed scope varies tremendously by the water depth and amount of chain.

I use a long chain rode for chafe protection and the ability to anchor in confined spaces with deep water.

Steve

[Sonosailor]

Panope: Your image and description are interesting, but I’ve been in the water when friends back up. The chain lifts a lot easier than you think. The angle of a 3:1 triangle is 18 degrees. Yes, the weight of the chain decreases that, but why start with 18 degrees? I’d love a little more honesty in this thread about how often the 3:1 people have to make a second or third attempt. By the way, the regular williwaws coming down the hills here are close to 30 knots and send the boats back with a hard jerk.

[Factor]

Originally Posted by noelex 77

Snip ....
The Mantus M1 is an excellent anchor (I have not evaluated the M2) and will set in even a shorter distance than the Rocna, probably due to its combination of high tip weight and very aggressive setting position due to the large roll bar. .

How would have a large roll bar change in any way the setting position?

[noelex 77]

I suspect much of the difference in the views expressed in this thread are based on the very different types of boats we sail.

Lightweight catamarans demand lightweight anchoring gear. This is entirely sensible. Ground tackle should always be comfortable to manage. Lightweight anchoring gear means a generous scope is needed to ensure adequate holding ability so I can understand the desire to always use long scopes.

[noelex 77]

Originally Posted by Factor

How would have a large roll bar change in any way the setting position?

The large roll bar of the Mantus presents the tip at a more aggressive angle to the seabed than the Rocna. This aids the penetration in difficult seabeds. I have owned and extensively used both of these models.

The Mantus roll bar is significantly larger than the Rocna roll bar. The first photo shows a Rocna anchor with an identical weight Mantus roll bar placed on top. The difference is significant and more than people realise simply viewing most photos of these two models.

The second photo shows the initial setting position and aggressive attitude of the Mantus. This sharp downforce helps the anchor initially penetrate difficult substrates such as weed and hard sand. The thin tapered fluke also helps. The smaller roll bar of the Rocna makes the anchor less wide and therefore the setting angle is less. The tip is presented at a shallower angle and therefore is less likely to penetrate.

The advantage of the Rocna is that it significantly less wide than the Mantus therefore it is easier to fit on many yachts, an important factor, but the setting angle and therefore the performance is poorer. The Rocna is still an excellent anchor but the Mantus M1 is better in my view.

[rslifkin]

Originally Posted by Sonosailor

Panope: Your image and description are interesting, but I’ve been in the water when friends back up. The chain lifts a lot easier than you think. The angle of a 3:1 triangle is 18 degrees. Yes, the weight of the chain decreases that, but why start with 18 degrees? I’d love a little more honesty in this thread about how often the 3:1 people have to make a second or third attempt. By the way, the regular williwaws coming down the hills here are close to 30 knots and send the boats back with a hard jerk.

Personally I've only had 1 failed set at 3:1 and that was due to a cobblestone bottom. But I've never tried to anchor at 3:1 in less than 20 feet of water (plus 6 feet to the bow roller, so that's still almost 80 feet of chain) and I've only done it that shallow a couple of times.

I think short scope makes things more sensitive to technique, so depending on someone's technique they may have more or less trouble getting a good set at short scope.

And as previously mentioned, anchor choice is a factor. Some designs lose performance faster than others as you shorten the scope.

Anchor size will have an effect as well. If the anchor is oversized you can use a shorter scope under the same conditions. By conventional wisdom, 3:1 scope has you down to about 40 percent of optimal holding power. Anchor size and conditions will determine if that's enough. 5:1 isn't enough for maximum holding either. With most anchors that'll require somewhere between 7 and 10:1, although the amount will be lower in deep water with an all chain rode.

[Panope]

Originally Posted by Sonosailor

Panope: Your image and description are interesting, but I’ve been in the water when friends back up. The chain lifts a lot easier than you think. The angle of a 3:1 triangle is 18 degrees. Yes, the weight of the chain decreases that, but why start with 18 degrees? I’d love a little more honesty in this thread about how often the 3:1 people have to make a second or third attempt. By the way, the regular williwaws coming down the hills here are close to 30 knots and send the boats back with a hard jerk.

It appears that we will have to agree to disagree.

Farewell,

Steve