65 lb. anchor on a Lagoon 400?

[roetter]

Originally Posted by 2Hulls

Wow. Absolutely? Are you serious? 125 lb Mantus? Is this because you're not using a chain rode?




2 Hulls Dave

That 125lb Mantus was supposed to be our absolute storm hook. So far we have no issues using it every day, so we are leaving it on for now.

Chain does not hold the boat nor does it increase the holding force of an anchor. It made sense in the old days with the fisherman type anchors that had next to no holding power. Once you come up to the holding force of your modern anchor your chain is bar tight and there is no catenary - well maybe 1" on 100'. It has no effect on the pulling angle of the chain on the anchor. I rather safe the weight of the chain for boat performance and use the extra stretch of the rope for absorbing/dampening wave and veering loads in storm force winds.


Rolf

[2Hulls]

I disagree, Rolf. But I'm not going to debate it as I don't want to waste my time on one so certain. 1" in 100'?

I wish you luck - especially when you have to retrieve that anchor without the benefit of a fully functioning windlass and rode.

2 Hulls Dave

[roetter]

You may want to check out this article Catenary & Scope In Anchor Rode



There is next to no catenary left in that all-chain anchor rode. Catenary is an ancient myth for todays anchors.

[tuskie]

Originally Posted by 2Hulls

Frankly, I disagree you need any more than about 25kgs on a 400.

Second that. I think the oversize anchor theory has gone a bit too far, but if it lets you sleep better.....

The anchor windlass will handle a heavier anchor alright, but there it increased wear and tear as well as extra amps to retrieve it every time. Perhaps keep the storm anchor for storms and use the "proper size" for everyday use?

Anchor weight is just one aspect of holding power. My lightweight Fortress FX37 holds better than the 25 kg Delta in mud and soft sand. So you don't necessarily need a heavy anchor for some bottom types.

Rolf is correct about chain catenary not assisting absolute holding power. He is spot on about rope rode saving weight as opposed to chain. Only problem is in very light wind the rope rode can find its way to the bottom and this can lead to a cut off on coral or oysters. Very disconcerting when the the boat starts drifting when you least expect it! That's not good for sleep!

[roetter]

I agree about the possibilty of chafe or cutting through the rope.

In the Bahamas all anchorages I have been so far have been
A - shallow water (up to 5m, 15') so I don't get to my rope. 30m chain (100 feet)
B - so far I have always been over sand, so no danger of cutting the rope.
C - our bridle is 3-strand and almost always on the bottom and dragging around. So far no bad chafe in about 150 anchor days

I expect to use the rope only in strong wind when the wind force will keep the rode tight and lif the chain off the bottom.

I never (I hope it stays that way) near coral as I don't want to damage it.

I aggree, it is not the weight that creates holding power, it is the blade area and geometry. I wish there was an allround aluminum anchor that withstands the daiy abuse.

The Mantus may go back into the locker again. A little nore testing is on the order.

[2Hulls]

Originally Posted by roetter

I agree about the possibilty of chafe or cutting through the rope.

In the Bahamas all anchorages I have been so far have been
A - shallow water (up to 5m, 15') so I don't get to my rope. 30m chain (100 feet)
B - so far I have always been over sand, so no danger of cutting the rope.
C - our bridle is 3-strand and almost always on the bottom and dragging around. So far no bad chafe in about 150 anchor days

I expect to use the rope only in strong wind when the wind force will keep the rode tight and lif the chain off the bottom.

I never (I hope it stays that way) near coral as I don't want to damage it.

I aggree, it is not the weight that creates holding power, it is the blade area and geometry. I wish there was an allround aluminum anchor that withstands the daiy abuse.

The Mantus may go back into the locker again. A little nore testing is on the order.

Yep, sounds like a good argument to go to a lighter anchor!

There's nothing like Bahamas grade sand. You can find it is some locations of the E Carib, but it's usually deeper. Drakes anchorage in Gorda Sound comes to mind, but it's nothing like 6' Bight of Acklins. Once you get "Acklinated"

But sooner or later you need to anchor deeper and need to worry about the coral. Preheat oven to a cold front with 180* shift and stir vigorously. Who's sleeping better? The folks with 30kg and all chain or the folks with 60kg and nylon? Why not 60kg AND chain? Where's the cut off? It's on the coral....

2 Hulls Dave

[meirriba]

Originally Posted by roetter

Chain does not hold the boat nor does it increase the holding force of an anchor. It made sense in the old days with the fisherman type anchors that had next to no holding power. Once you come up to the holding force of your modern anchor your chain is bar tight and there is no catenary - well maybe 1" on 100'. It has no effect on the pulling angle of the chain on the anchor. .....

Rolf

So you put out as short a rode as possible, (as it has no holding power anyway and no effect on the angle)?
I believe that you should rephrase your statements.
Good luck.

[tuskie]

Originally Posted by meirriba

So you put out as short a rode as possible, (as it has no holding power anyway and no effect on the angle)?
I believe that you should rephrase your statements.
Good luck.

No, methinks you've misunderstood Rolf's point regarding chain versus rope.

Modern anchors are capable of holding such force that before they break free a chain rode set at (say) 7 to 1 will be straining at such force that the catenary curve has disappeared and the angle from anchor to boat us a straight line. As such, rope of adequate breaking strain would function the same as chain. That is, a straight line. As Rolf points out, rope rode may even have the advantage of a bit of stretch as opposed to the inflexibility of chain. At such extreme conditions the ratio of ride to depth is most important as it is a straight line rather than a catenary curve that flattens towards the bottom. So more rode rather than less because that angle becomes more critical.

The Rocna anchor website that Rolf has linked has a excellent article on this subject.

[jaybird1111]

Forces

at the bottom of each page is a 'forward' arrow so you can read the articles progressively

[meirriba]

Hi Tuskie,
I have read Peter Smith's articles and have no argument with him as to his findings. They seem excellent material.
However, there will be a difference at lighter winds between the wind force at which rope and chain become bar-tight.
We do not anchor as a rule under 60 knots of wind with 48m rode.

Normal state is supposed to more benign and when I am preparing to anchor in 35-40kn and put out 70m of chain, I believe to be anchored better than with 70m of rope.

[Beach View]

Thanks everyone for your replies, great information here on anchors, scope, windless', chain, rope, etc., just as I expected from CF. In the end I compromised by purchasing a 45lb Mantus--10 lbs heavier than my plow, probably better design. I don't want to ignite the "my brand is better than your brand" war, Mantus just happens to work for me. If anyone is looking, I found the best price on the internet by $20-$60, plus free shipping ($30-$35 for me) at https://www.baconsails.biz. I'll disassemble the 65 lb Mantus and keep it for my original purpose (heavy duty storm anchor), which brings me to a new twist in an old thread...

Some of the information on this thread implies that at the point where your anchor chain/line is "bar tight" the chain may be doing relatively little to keep you from dragging, rather may depend more on the scope and the design and/or weight of the anchor. Does this mean in a SHTF situation (i.e. really windy!) I can simply tie an anchor line (no chain) on my 65 lb Mantus and let out a lot of scope, say 8-10:1? If that's so, it would make setting a storm anchor relatively easy--without chain you could simply toss a large anchor in the dinghy, tie off a long anchor line, motor the dinghy up wind and lower the anchor, which you could then set from the boat. Of course it's more complicated than that, but I hope you get the drift of my question....

Thanks,

Bill

[BigBeakie]

Bill,

Rope only rode has to be absolutely sure there is nothing, NOTHING, that can chafe the rode. No rocks, no little clumps of coral, no barnacle encrusted log on the bottom, etc etc.

When could you ever be that sure that there is nothing, in the radius of the rope rode, on the bottom that couldn't chafe the line. Under tension, it doesn't take much to lose your boat to chafe.

What therefore, is the most prudent tactic?