Consequences of a too big Anchor - Rocna

[Snowpetrel]

I used to pull up a 20kg plow with 3/8 chain by hand. Doable but was made much much easier and safer with a homemade chain pawl on the bow roller. If your not going to get a windlass consider fitting one to save fingers and back.

You can weld one up easily from stainless plate and hinge from the bolt that prevents the chain jumping off the roller.

Cheers

Ben

[GordMay]

Originally Posted by Mike OReilly

... Bigger is generally better when it comes to setting and holding, but too big and it will inhibit proper technique. You never want to be dissuaded from re-trying when the set is not right...

And, at some point (not in this case), an anchor becomes too large for you ('re engine) to actually set at all.

[noelex 77]

Originally Posted by GordMay

And, at some point (not in this case), an anchor becomes too large for you ('re engine) to actually set at all.

Gord you are right of course, but I don't think this issue, which is often raised, is a practical problem.

Have a look at the video of my Mantus setting:

Underwater Video of the Mantus Anchor Setting - Cruisers & Sailing Forums

This anchor is +2 sizes over recomended and my engine horsepower is average. A Maxiprop (but only two bladed) helps a bit with reverse thrust.
This set is in firm sand with virtually no wind.

In other words this is about as bad as it can get in terms of the setting force verses anchor size, but the anchor still sets beautifully. (And this sort of set is typical for the Mantus) I know an anchor this set will have no trouble rotating to a new wind direction.

if I did want some more I could use the boats momentum (this is how some people set normally) or simply leave the reverse on longer. This is not necessary when the anchor sets this well.

I don't believe setting a large anchor is a practical problem even with a model that is well oversized. The only exception I can see is a boat without an engine, or some of the outboard equipped yachts.

The stats are 57kg (125lb) anchor on a 47 foot boat with a 54hp motor.

[Blue Crab]

Originally Posted by GordMay

And, at some point (not in this case), an anchor becomes too large for you ('re engine) to actually set at all.

I did an anchor swap for this reason back when I had my 4,000# boat.

Now, having doubled my boat size more or less, that trade looks pretty bad.



Hint .. hint.

[sailorboy1]

Originally Posted by noelex 77

I don't believe setting a large anchor is a practical problem even with a model that is well oversized.

It would seem to me that an anchor would set to match the force applied, regardless of it being oversize.

[noelex 77]

Originally Posted by sailorboy1

It would seem to me that an anchor would set to match the force applied, regardless of it being oversize.

That is right.

The argument often used to discourage larger anchors is that even with the boats maximum setting force a large anchor will still be unset, or poorly set.
If this was true in most cases if extra wind arrived this would provide the motive force to set the anchor. In fact some cruisers deliberately do this and never set their anchor.

To set, and particuarly to start to bury, an anchor, ideally, needs a slow steady increase in force.

Wind naturally tends to provide this steady force, especially with some dampening from the chain and snubber, but with an unset anchor the sudden arrival of lot of wind does not provide the ideal conditions to start to bury an unset anchor. Once dragging anchors rarely set.

There is also no test of the substrate with an unset anchor.

However, the premise that a large anchor cannot be set by the yachts engine is incorrect. I do not accept a poorly set anchor for overnight stay and my experience with an oversized Rocna and now an oversized Mantus is that there is plenty of engine power to set an oversized anchor. So as long as limit the discussion to anchors that are practically possible (rather than the theoretical large ships anchor on a pleasure yacht) I believe the fear of not being able to set an oversized anchor is unfounded.

[Mike OReilly]

Originally Posted by noelex 77

...However, the premise that a large anchor cannot be set by the yachts engine is incorrect. I do not accept a poorly set anchor for overnight stay and my experience with an oversized Rocna and now an oversized Mantus is that there is plenty of engine power to set an oversized anchor. So as long as limit the discussion to anchors that are practically possible (rather than the theoretical large ships anchor on a pleasure yacht) I believe the fear of not being able to set an oversized anchor is unfounded.

I tend to agree Nolex. While I can see Gord's point, I think the practical reality is that an anchor that can be reasonably carried and deployed is one which the engine will also be able to at least begin to set. Size of boat tends to dictate size of gear, so a larger boat tends to have larger anchor capacity, larger windlass & rollers, and larger engine. There would be exceptions, of course, but as a general rule these things tend to be connected.

I suppose location matters though. In places such as up here on the Great Lakes, our wind patterns are pretty erratic, and summer months produce lots of sever and sometimes sudden thunderstorms. A poorly set anchor can easily be popped out in these cases, so one could argue that being able to set properly should prioritized higher than having a big beast.

[forsailbyowner]

[QUOTE=Mike OReilly;1553586

I suppose location matters though. In places such as up here on the Great Lakes, our wind patterns are pretty erratic, and summer months produce lots of sever and sometimes sudden thunderstorms. A poorly set anchor can easily be popped out in these cases, so one could argue that being able to set properly should prioritized higher than having a big beast.[/QUOTE]


I second that. Most places I anchor the current changes direction 4 times a day. Every time the anchor must reset.

[gtunison]

Originally Posted by Cavalier

Quite simply: regardless of windlass, don't buy an anchor which is equal to or larger than the displacement of your vessel! #sillywaystosink

Good one!

[Jim Cate]

I too fail to believe that a Very Large Anchor (VLA) is a danger.

1. I think we mostly agree that heavier anchors have higher tip loading due to their higher weight. This expedites penetration of the top layer(s) of the seabed and helps initiate the setting process.

2. If lack of thrust prevents further burying of the anchor it will just sit there... until greater pull on the rode occurs. IF the wind then increases and puts more load on the anchor, this seems very much like having greater engine pull, and the anchor will continue to bury. If the wind changes the direction of the pull, the anchor will either dig in anyway, or will pivot around the partly buried tip and then continue to bury.

This idea that there is something different about loads from wind/sea and from engine thrust doesn't make sense to me. And even in sudden gusts, the anchor loads build up gradually, due both to the dampening effects of catenary and the inertia of the boat.

So, I gotta agree with all the others who have said, in effect, if the boat can usefully carry and deploy the anchor, it ain't too big!

Cheers,

Jim

[Adventurebound]

What does one define as an oversized anchor? Is it one larger than recommended by the manufacurer or one larger than required to hold the boat in the strongest recorded wind in the softest muddy bottom? It would probably be some where in between and that will the the right size anchor for you.

[Mike OReilly]

Originally Posted by Jim Cate

2. If lack of thrust prevents further burying of the anchor it will just sit there... until greater pull on the rode occurs. IF the wind then increases and puts more load on the anchor, this seems very much like having greater engine pull, and the anchor will continue to bury. If the wind changes the direction of the pull, the anchor will either dig in anyway, or will pivot around the partly buried tip and then continue to bury.

OK... But doesn't this suggest that we don't really have to worry so much about setting the anchor? If the wind will set it just fine most of the time, then why bother with all the effort of digging it in and getting a solid set? Why not just pay it out so as not to foul the anchor, get the tip digging with a little tug, and crack open the beers.

[Nicholson58]

I think maybe we screwed up.

[Jim Cate]

Originally Posted by Mike OReilly

OK... But doesn't this suggest that we don't really have to worry so much about setting the anchor? If the wind will set it just fine most of the time, then why bother with all the effort of digging it in and getting a solid set? Why not just pay it out so as not to foul the anchor, get the tip digging with a little tug, and crack open the beers.

Mike, IMO the long steady pull both sets the anchor (whatever size) and establishes that there is not some unexpected phenomenon at work interfering with the set. IE, very loose silt, hardpan, or debris. We've hooked lots of odd things over the years -- a pair of board shorts, many plastic bags, a kitchen sink (really!), tires, bottles (over the tip of the anchor) and of course the sort of thing that won't let your anchor go -- old mooring blocks, cables, chains, bommies... gaahhhh, the crap that sits on the bottom!

The first category becomes obvious when you pull on the anchor and it just slides along. The second category is not noted until you try to weigh anchor, often at an inconvenient time!

Cheers,

Jim

[Mike OReilly]

Originally Posted by Jim Cate

Mike, IMO the long steady pull both sets the anchor (whatever size) and establishes that there is not some unexpected phenomenon at work interfering with the set. IE, very loose silt, hardpan, or debris. We've hooked lots of odd things over the years -- a pair of board shorts, many plastic bags, a kitchen sink (really!), tires, bottles (over the tip of the anchor) and of course the sort of thing that won't let your anchor go -- old mooring blocks, cables, chains, bommies... gaahhhh, the crap that sits on the bottom!

The first category becomes obvious when you pull on the anchor and it just slides along. The second category is not noted until you try to weigh anchor, often at an inconvenient time!

I've always thought it important to ensure I have a good set with my anchor. I spend time digging it in, and ensuring it will hold at maximum reverse. I can usually get the anchor set such that the flukes are completely buried. This takes time, and fuel. What you're suggesting is that this is unnecessary. Once I feel the anchor grabbing, that's enough?

When I anchor under sail (which happens occasionally) we usually can't get the same set as with the engine. So far so good ... so maybe I should be less anal about getting the perfect set all the time.

A kitchen sink? Worst we've hooked onto are trees, logging slash and deadheads. I've seen old massive chain used to create log booms, but that's the worst of it up here ... man, I love Superior .