Video of My Anchor Setting Technique

[noelex 77]

I took this video while setting the Mantus anchor. The fundamental procedure I use is to lay the chain out slowly in a straight line. Then when the full scope is out, the force on the anchor is gradually increased by upping the revs in reverse. I end with full reverse for about 30 seconds. Some maintain the reverse for longer (like Dockhead) for several minutes. There is nothing wrong with that.

I edited out the laying out of the chain in this video because it was a bit boring.

Notice how the nylon snubber stretches as the force increases.

The video ends with some still shots of the resulting set underwater and the location.

Some people balk at applying this much force, but it is the only way to be sure the anchor will hold in moderate wind.

It is important to monitor carefully that you are not moving backwards while the force is applied. The video also demonstrates the illusion of the prop wash which creates the impression of moving backwards.

A good anchor will grab very reliably with this sort of treatment. I use this every time I anchor and although it is early days, so far the Mantus still has an unblemished record of setting and holding on the first drop.


This is my typical setting procedure with a slow build up to full reverse which is held for 30s.
Notice the creaking of nylon snubber and how much it stretches under the strain.
The voice is my wife (we use radio communication between the bow and helm.).

If you want to see what happens underwater.see here:
http://www.cruisersforum.com/forums/...ng-127014.html

Mantus Anchor drop and Set - YouTube

[FranklinGray]

4:1 ratio is good if you are anchoring in deep water but not shallow water. Why is it that so many cruisers seem to think 3:1 or 4:1 when using chain is the same as 7:1 with rope?

When using chain, the depth of the water determines what scope you can get away with. In 10 feet of water with a 4:1 scope your chain rode will be pulled tight in 30 knots of wind, so that weight advantage that you thought you had by using chain is gone.

Now when anchoring in 40 feet of water and you put out a 4:1 scope, then you have a lot more chain and also a lot more weight, so that will still keep the chain down in 40 knots of wind.

So for those of you who say "you only need a 4:1 scope with chain", please keep this in mind and don't anchor near me.

Franklin
s/v Dreamboat

[noelex 77]

Thanks for your comments Franklin.
I agree 4:1 with chain is nowhere near as good as 7:1 with rope.

However, I think you are putting too much faith in chain catenary. In 40 feet of water anchored @ 4:1 the chain will not stay on the seabed at 40 knots.


There is no need to worry about boats with good anchoring gear using around 4:1 in moderate wind conditions. While more scope is always better for holding it is not always possible, or desirable.

If you have a look at the underwater video of the Mantus it sets beautifully at 3:1 in 4.4m of water. The setting force I use is equivalent to about 25-30 knots of wind, so the video simulates, roughly, what will happen at this wind level. There is every indication that the anchor would just continue to bury with more wind force.

Note that the anchor buries well despite the chain lifting off the seabed.

Despite the good performance @ 3:1 in 4.4m water, 30 knots of wind would start to make me nervous and it would be prudent to increase the scope then if this is possible.

Chain in the anchor locker does no good and it is silly to use short scopes in deserted anchorages with loads of swinging room, but it is also to unnecessary to be nervous (or to reject anchorages) when only a short scope is possible providing the wind remains light to moderate.

[S/V Alchemy]

Originally Posted by noelex 77

Thanks for your comments Franklin.
I agree 4:1 with chain is nowhere near as good as 7:1 with rope.

However, I think you are putting too much faith in chain catenary. In 40 feet of water anchored @ 4:1 the chain will not stay on the seabed at 40 knots.


There is no need to worry about boats with good anchoring gear using around 4:1 in moderate wind conditions. While more scope is always better for holding it is not always possible, or desirable.

If you have a look at the underwater video of the Mantus it sets beautifully at 3:1 in 4.4m of water. The setting force I use is equivalent to about 25-30 knots of wind, so the video simulates, roughly, what will happen at this wind level. There is every indication that the anchor would just continue to bury with more wind force.

Note that the anchor buries well despite the chain lifting off the seabed.

Despite the good performance @ 3:1 in 4.4m water, 30 knots of wind would start to make me nervous and it would be prudent to increase the scope then if this is possible.

Chain in the anchor locker does no good and it is silly to use short scopes in deserted anchorages with loads of swinging room, but it is also to unnecessary to be nervous (or to reject anchorages) when only a short scope is possible providing the wind remains light to moderate.

A good video (it turned up in my Facebook feed, btw) and a good technique, but apart from "lunch hook/light air" use, as you've specified, I see no reason NOT to put out greater scope with ANY anchor. I freely admit that my attitude comes from seeing and hearing of short-scopers who dragged with a wind change, or, more commonly, break out their anchors and fail to reset. An anchorage so crowded as to not permit adequate scope (apart from, literally, an hour for lunch) is not in my view an anchorage in which I want to stay.

My opinion is also informed by having a 16 tonne pilothouse cutter in steel with both more windage and more inertia for which we must compensate. On our other 1970s racer-cruiser, a sloop with low freeboard, a 22 lb. Danforth with a 1/2 inch rode and a chain leader is the lunch hook, and a upsized Fortress (the model made for 40 footers) with 5/8" rode is the main. I can't recall when I've ever gone below 5:1, and have done 10:1 in a blow.

Have you used a bridle with this Mantus, or do you find to this point that the snubber is sufficient to purpose?

[gcaptain]

Originally Posted by noelex 77

It is important to monitor carefully that you are not moving backwards while the force is applied. The video also demonstrates the illusion of the prop wash which creates the impression of moving backwards.

Experienced ship handlers use this illusion to their advantage. Once a ship is in position to drop anchor the captain will reverse the engine and watch the forward edge of the prop wash... once the leading edge of the prop wash is abeam you know the ship is dead in the water and it's safe to drop the anchor.

You can also get a rough idea of the difference between your SOG, speed over ground (where you set the anchor), and your speed over water (how much astern propulsion you need) by getting a feel for the differing between what the GPS is telling you (SOG) and how fast you are moving through the water.

This is especially important if single-handing or the person on the bow isn't providing great feedback re the tension and position of the chain.

[noelex 77]

I am fully supportive of the view that increased scope = increased holding power.

A longer scope makes me happier, but unfortunately in many of the anchorages I visit this is just not possible. The restriction is not usually from other boats, but from hazards in the anchorage such as rocks. Much of the shoreline gets deep very rapidly so anchoring further out is not a viable option.

It is also a matter of risk management. For example tonight the forecast is for a 10-12 knots northerly wind. 4:1 in these sort of conditions is perfectly safe. It also gives me a 360 degree swing circle. 7:1 would give better holding, but if the wind swings around to south (unlikely, but not impossible) we would run out of water and ground.

So 4:1 is safer, for the conditions than 7:1.

If the forecast becomes a strong Meltemi (northerly) wind, as it was a few days ago, I can let out more scope. With a strong Meltemi the risk of south wind becomes non existent.

Of course some would express the view that the anchorage is unsafe. There alternative anchorages available where these restrictions don't apply, but one of the incentives to employ the best anchoring gear and techniques is to enjoy these out of the way spots in near solitude.

[S/V Alchemy]

Originally Posted by noelex 77

I am fully supportive of the view that increased scope = increased holding power.

A longer scope makes me happier, but unfortunately in many of the anchorages I visit this is just not possible. The restriction is not usually from other boats, but from hazards in the anchorage such as rocks. Much of the shoreline gets deep very rapidly so anchoring further out is not a viable option.

It is also a matter of risk management. For example tonight the forecast is for a 10-12 knots northerly wind. 4:1 in these sort of conditions is perfectly safe. It also gives me a 360 degree swing circle. 7:1 would give better holding, but if the wind swings around to south (unlikely, but not impossible) we would run out of water and ground.

So 4:1 is safer, for the conditions than 7:1.

If the forecast becomes a strong Meltemi (northerly) wind, as it was a few days ago, I can let out more scope. With a strong Meltemi the risk of south wind becomes non existent.

Of course some would express the view that the anchorage is unsafe. There alternative anchorages available where these restrictions don't apply, but one of the incentives to employ the best anchoring gear and techniques is to enjoy these out of the way spots in near solitude.

Your reply is far more nuanced (and therefore reasonable, in my view) than "4:1 is OK, it says so on the box!"

I suppose I will have to judge for myself once we get to unfamiliar anchorages. Experience will no doubt influence the risk evaluation that comes when figuring out how much scope will do the job predictably.

Do you also use a bridle with this Mantus, or just the snubber? Thanks.

[noelex 77]

Originally Posted by S/V Alchemy

Do you also use a bridle with this Mantus, or just the snubber? Thanks.

Just a snubber.

[S/V Alchemy]

Originally Posted by noelex 77

Just a snubber.

Because in your experience a snubber is enough, or because you don't like a bridle? I'm asking because I also have a metal boat and the builder was clever enough to include very beefy deck bollards AND a nice waterline 1/2 inch steel tab with two handy holes; the top hole is for the bobstay...and I'm trying to determine the "either/or/both" setup. As one does.

[noelex 77]

A bridle is supposed to reduce sheering, but I have not found it makes much difference on my monohull, but other designs will be different. Bridles are of course essential on a cat.

The steel tab you have on the waterline has the advantage that it increases the scope (or decreases the swing circle for the same scope) so it would get my vote. I presume it would would also reduce chafe.

I think you need to do some experimentation. The effect of the increased scope when using the steel tab is easily predicted just by measuring the freeboard and some simple maths. The effect of using bridle can only be found out by trial and error as the effect will vary from boat to boat.

[cwyckham]

Originally Posted by noelex 77

A bridle is supposed to reduce sheering, but I have not found it makes much difference on my monohull, but other designs will be different. Bridles are of course essential on a cat.

The steel tab you have on the waterline has the advantage that it increases the scope (or decreases the swing circle for the same scope) so it would get my vote. I presume it would would also reduce chafe.

I think you need to do some experimentation. The effect of the increased scope when using the steel tab is easily predicted just by measuring the freeboard and some simple maths. The effect of using bridle can only be found out by trial and error as it will. Vary from boat to boat.

The tab on the waterline will also keep the chain from rubbing on the bobstay and echoing throughout the boat!

[S/V Alchemy]

Originally Posted by noelex 77

A bridle is supposed to reduce sheering, but I have not found it makes much difference on my monohull, but other designs will be different. Bridles are of course essential on a cat.

The steel tab you have on the waterline has the advantage that it increases the scope (or decreases the swing circle for the same scope) so it would get my vote. I presume it would would also reduce chafe.

I think you need to do some experimentation. The effect of the increased scope when using the steel tab is easily predicted just by measuring the freeboard and some simple maths. The effect of using bridle can only be found out by trial and error as it will. Vary from boat to boat.

I intend to test both, but real-life reports are helpful. I sometimes get asked "well, what will you do all day while cruising?" I reply: "Well, besides the log-keeping and the general maintenance, I get to prove or disprove for myself all the theories about sail-handling, drogues, ground tackle and provisioning I heard in the ten-year run-up to actual cruising".

I didn't even mention getting my kid to learn math by taking noon sights.

[S/V Alchemy]

Originally Posted by cwyckham

The tab on the waterline will also keep the chain from rubbing on the bobstay and echoing throughout the boat!

No fear! I have insulation only to the waterline, as is typical on steel boats that don't mean to rust internally. The whole forepeak is a workshop and the collision bulkhead will be soundproofed, but there's a limit to how quiet you can make a steel hull.