Anchoring technique

[itsonlymoney]

My mate was talking to some old seadog at the show who explained a technique using a "Weight" shackled to the anchor rope to keep it on the bed and the anchor set /forums/images/graemlins/confused.gif Can anyone explain in more detail and or a link with a diagram etc. How heavy a weight, how far from anchor, how deep etc etc etc.
We may be able to use this on the lake as we woke one morning last year about 200yds from were we anchored. There was three of us rafted one of which was a yacht, I wasnt concerned cos the yachts keel would have hit the ground first therefore saving our two mobo's /forums/images/graemlins/grin.gif

 

[omega2]

cannot see how that would work, ok it would hold down the rope but what about recovery? it would be a nightmare, if the "weight" was running on the rope it would end up at the anchor and destroy the anchors design, and then add more weight to heave. The answer is to have enough chain before the rope is fitted, this is what makes the hook work, make sure it is heavy enough to do the job, we hold 33ft in a tide run with a 17kg Delta and only 20 feet of chain. Did you each deploy an anchor or rely on just one?

 

[adrianb]

I'm assuming it' an "Anchor Chum" do a search on here for more..........


Adrian

 

[itsonlymoney]

I think you have a seperate rope on it. Yes we all deploy.

 

[itsonlymoney]

Thats the thing I remember now what he caled it "a chum"

 

[Nick_H]

Anchors work properly when the pull is mostly horizontal, hence the need to put out lots more chain than the depth, so you get what's called a catenary effect, which is basically a bow in the chain to achieve the horizontal pull.

If you shackle a weight to the chain a few feet in front of it it will cause the length of chain between the weight and the anchor to lie completely horizontal, then when there is a pull on the chain the pull on the anchor will be horizontal and it will work to its optimum effectiveness.

Its sounds like a fair bit of hassle though, and it is probably easier to upgrade the chain diameter if you are having slipping problems.

 

[Deleted User YDKXO]

There was a neat demonstration of this at LIBS recently (sponsored by Yachting Monthly?). The purpose of the weight is twofold, firstly as houghn says, it reduces the engle of the anchor chain/rope so that the pull on the anchor is as near the horizontal as possible but also the weight absorbs some of the shock loading on the anchor chain caused by the boat shearing around which could cause the anchor to break out
One point the LIBS demo made was that in a crowded anchorage where you could'nt let out too much chain because the boat might collide with others, you can increase the holding power of the anchor with a weight
The weight used at LIBS was a bag of sand attached to a shackle with a recovery rope fixed to it. To launch the weight, the shackle was opened and attached around the anchor chain and then the bag simply slid down the anchor chain to the required length which I seem to remember was recommended to be about 2/3 down the chain. To recover the weight you simply pulled on the recovery rope and removed the shackle
As has already been said, you can achieve the same effect by increasing the anchor chain size but on a boat which has a mix of rope and chain and where maybe its not practical to increase the size of the anchor chain , an anchor weight could be useful

 

[itsonlymoney]

Thank you sounds like this technique may be beneficial to us.

 

[Nautorius]

Cheers Mike,

Saw people doing this around Menorca and thought they were keeping their beer cool! That explains a lot,

Cheers

Paul /forums/images/graemlins/laugh.gif

 

[alandee]

If you search "anchor chum" you will find a discussion that went on for days on the forum during the LIBS a week or so back. Remember however, that what works for one person on one type of boat/yacht might not apply to another.

 

[itsonlymoney]

Thanks just had a look, some interesting reading.

 

[Searush]

Main benefit in my view is in busy anchorages. An Angel or Chum has the effect of reducing the scope of chain needed for given conditions. I have also used mine to increase the holding power of my full chain in adverse conditions.

The final benefit is that, in the event of short steep waves, the weight dampens out the jerks and minimises the risk of snatching. Note that the angel or chum does not need to be on the sea bed - and may work better if it isn't as the catenary fro weight to boat will be vertical.

How it works. Consider the normal chain catenary under load. It is a long steady curve from the anchor to the bow of the boat. Then slide a heavy weight down the chain. You will have a steep catenary from the boat to the weight and a shallow catenary from the weight to the anchor. The key is in the shallow catenary from the weight to the anchor; there is very little lift in the pull on the anchor so it is far less likely to be broken out.

 

[craigsmith]

Anchor kellets/chums are a waste of time for improving the performance of the anchor. They do not increase the ultimate holding power of the anchor.

The recent thread that others have mentioned is here:
www.ybw.com/forums/showflat.php/Cat/0/Number/1306711/page/0/fpart/1/vc/1
No need to repeat it all.

Searush's comments are correct in that there are some other uses. For benefiting the angle of pull on the anchor, the weight needs to be as close as possible to the anchor itself. Moving it halfway up the rode halves its benefit in this context (however, considering this benefit is so trivial as to be useless in the first place, don't worry about it).

It offers the maximum shock absorbing capabilities at a halfway distance. However, as per the performance argument, be aware that the rode will be next to straight regardless in strong conditions, i.e. the situations you are likely to care about, and the kellet will again offer little or no actual benefit.

It offers the best reduction of swing radius at a distance down the rode equal to the water depth, but this technique can be a false security - in strong conditions again your rode will be straightened, as the kellet will not be able to help, and your swing radius will suddenly be more than it was in light winds - and, in those light conditions, your swing radius will be different to other boats using more sensible rodes, which can cause problems.

 

[itsonlymoney]

I know this threads a bit old now but we (three of us) have now got, curtousy of our yachty friend a chum each. Excellent job he had em made of 6" approx steal rod with an eyelet welded to the top and then galvanised, wish I had a picture cos they are a great job, even got the weight stamped on em. Two cruisers 28' and 27' have 10kg and the 34' yacht's got a 20kg.
Anyway to the question............seems to be a difference of opinion as to wether the chum should be on the bed or a couple of feet above and how far away from the anchor it should be ?
Ian

 

[duncan]

[ QUOTE ]
Anyway to the question............seems to be a difference of opinion as to wether the chum should be on the bed or a couple of feet above and how far away from the anchor it should be ?


[/ QUOTE ]

that's because it achieves different things 'best' at different points.

ultimate holding, assuming the rode has sufficent damping elsewhere - stick it right down at the anchor.

reducing the swinging circle in restricted anchorages (but of course meaning you will go your own way in company) overdepth by an amount consistent with the wind or current such that it's on the ground

reducing snatching by damping the rodes vertical movement - underdepth in light conditions, about 2/3rd along the rode in more extreme conditions (but you should have other elasticity in the rode too ideally)

the above from memory of the various threads so correct me if I have fallen foul of old age..........

 

[itsonlymoney]

So really theres no hard rule in fact this technique could be used for a number of reasons Yes ?

 

[Deleted User YDKXO]

Not sure I agree with that. I thought the point of an anchor weight was 2 fold, firstly to reduce snatching of the anchor chain by increasing the catenary effect of the chain and secondly to reduce the vertical component of the pull on the anchor ie. make the chain pull more horizontally. It's the snatching and the vertical component of the chain angle which reduces the anchor holding capacity
I'm happy to be flamed on this by the experts but I don't see any point in putting the weight right down near the anchor where it will have little or no effect on the angle of the chain or snatching. According to the YM demo at LIBS, the weight should be about 2/3 along the chain from the boat

 

[duncan]

firstly we are agreeing about snatching and the recommended compromise position as far as I can see..........

with reference to the best position for ultimate holding again we agree it should be the one that keeps the pull horizontal - and then we disagree...........

think about a long pole - say a scafold pole - you hold one end and now where do you put the weight to deliver the maximum force preventing the other lifting? whilst the horizontal is only a vector component of the pull on the rode I believe this is mathematically correct BUT assumes that snatching has been taken care of in some other way.

I too am happy to be torn apart by the rabid wolves of anchor experts!

 

[hlb]

Umm. Well for a start, the more weight you get down there, the better. Others have said. Umm well ropes crap anyway, but much better if pulling horizontal, so add a weight. Maybe ten foot from anchor. Best weight would be a couple of V8 engines, but compromise a bit. Better still is loads of chain. You soon get fed up with lifting it. As will the sea. It sort of saps the stregth out. Ummph. /forums/images/graemlins/crazy.gif

 

[itsonlymoney]

Just to clarify........got about 10' of chain then rope. (no windlass so dont fancy pulling 30' of chain up)