Anchor chum

[wizard]

I was thinking of the bucket idea with it about 10-12ft below the surface.

The idea of a lump of chain on the end of a rope dragging around on the bottom appeals. But it might not find favour with the enviromentalists /forums/images/graemlins/smile.gif

 

[Danny Jo]

My existing tackle (35 m of 10mm chain, 35 m of 20 mm nylon, 15 kg Bruce) is perfectly adequate for most applications, and I've not so far been tempted to faff around with a chum. My attempts to upgrade are founded purely on my conviction that this tackle is likely to fail in severe conditions. OK, so it's unlikely I'll be drifting shorewards, dismasted, and engineless, but it would be nice to have the confidence that my anchor would hold.

Changing to a 8 mm chain would mean changing the capstan.

Mark

 

[duncan]

without provoking a 'which anchor' etc etc I would up it to 25kg and leave the chain - increase of 10 kg to stow and holding in extreme by some reasonable %.

alternatively a new generation anchor of 25kg, together with your 35m 10mm and 20mm rope should hold in anything you meet (with sufficient scope of course).

all I am really saying is that if I was looking to 'upgrade' your rode that's where I would start.

happy cruising

 

[bilbobaggins]

[ QUOTE ]
But it might not find favour with the enviromentalists

[/ QUOTE ]

There's not a lot that pleases them.

And if you're prepared to anchor there, with chain, then a steel ( or lead ) weight hanging off the back is unlikely to make any further difference.

If it's a choice between me and my lady-luv, and a dozen or so molluscs, I'll have the 'plateau des fruits de mer', thank you, and the chilled Muscadet.....

/forums/images/graemlins/wink.gif

 

[GMac]

A drogue, not massive, hung about 4-6ft under the water but on your anchor rode. Slide it down on a bow shackle or similar a bit like a chum.

Stop the rode a bit and the boat hangs nicer?

I've never tried it but was sitting on my bow a week or 2 back thinking it may work. Tried with a bucket but I think I suffered from no water flow 'through' it. It 'sort of' was trying to do something. I've just dug out a drogue (approx 500mm opening big end) and will try next time.

Just a thought. Anyone tried anything along these lines?

What's your boat there Freestyle? Even though I think Duncan is right with most of what is said, 25kg is a hell of a jump from 15kg.

 

[peterb]

[ QUOTE ]
I'd be interested to hear of anyone having used a 'chum' or somesuch lowered from the stern onto the bottom, and acting as a 'drudge' in reducing sheering about.

[/ QUOTE ]

Just a thought. In the days when people used rigid dinghies as tenders, it was recommended that a bucket be towed from the dinghy to prevent it from nuzzling up to the parent craft when at anchor. But the suggestion was that the bucket be towed from the bow of the dinghy, not the stern.

I wonder what would be the effect of a similar drag being applied to the bow of an anchored boat? If the bow starts to move sideways then it would provide a damping force tending to stop the swing. If you trailed a bucket from the stern then the force would tend to cause the swing of the stern to lag behind that of the bow, thus amplifying the angle of swing. Has anyone tried some form of damping at the bow?

 

[Danny Jo]

[ QUOTE ]
What's your boat there Freestyle?

[/ QUOTE ]
I thought you'd never ask!

Yes, I know about the cat's cradle of the lazy jacks - I'll get it right this year.

And looking at the pictures reminds me that adding 70 kg to the bow doesn't have much effect on her, in fair weather at least . . .

Mark

 

[craigsmith]

[ QUOTE ]
At the moment I have a 35lb CQR plus 45m of chain and 45m of Octoplait. I dont mind carrying the extra weight for the chum as for the one time you really needed it you would be eternally grateful.

So it looks like the weight has to be close to or more than the existing weight of the anchor to be useful ?

[/ QUOTE ]No, quite a bit more really.

Here are some sample cases of Fraysse's simulation as linked to already by Freestyle.

You do not say what chain you have. For your anchor 8 or 10 mm would be appropriate; I have been conservative and assumed 10mm. Here is the situation with a force on the rode of 300daN (1daN ~= 1Kg):

Even at this very low force, you can see the kellet is not doing much. Any small effect it is having, you don't care about - it's hard to say exactly, but this would represent the static situation of about 30 knots wind on your boat.

Look what happens when you really load up the line:

This is with 1000daN (over a tonne) force on the line. Equating roughly to 50 knots plus. Your CQR may or may not hold that depending on the holding, but anchors of the same size recently held much more than this in the SAIL and Yachting Monthly testing (the Rocna 15 @ over 2 tonnes on average, for example).

It should be obvious the kellet is a waste of time, even at this weight.

The only practical way to reduce the angle of pull on the anchor is to use good amounts of scope. One point Poiraud (Hylas) and I can agree on.

Now consider how much extra holding one would acheive by simply having a larger anchor.

[ QUOTE ]
I would have thought that lengths of chain dragged around and dropped in different positions with every wind shift and wave would damage a greater area of the seabed than a single chum (although of course there is also some chain movement with this as well). I don’t know whether you (Craig) are right or not but I think you have been a bit unfair condemning alandee so roundly.

[/ QUOTE ]The kellet is a single concentrated weight, by Alandee's definition the same as the anchor - or similar. It is intended to drag around, so minimizing sailing.

Such a heavy object dredging the seafloor is likely to do much more damage than chain alone. Furthermore, it will in fact work in typical (relatively light) conditions, keeping both it and the chain on the seafloor, whereas on average regular chain will spend more time suspended above the seabed.

 

[GMac]

Nice boat there freestyle.

I would have thought your rode would be sweet on that. Many down this way anchored on a lot less. No way would I go to a 25kg anchor on that. If I was really twitchy about that system, without starting that dreaded debate again, I might swap to another type of anchor of the same weight and if the boat was in no stress maybe lengthen the chain 15mts odd. I would down size the warp though, you need a fair bit of grunt to get 20mm Octi stretching nicely and I don't think you would have that. I think I would snore the nights away with the utmost of ease. In real extreme weather the mantra is 'scope, scope, scope'.

You're not that much bigger than me and I'm only on 15mts x 7mm, 12mm wrap and a 10kg anchor (cruising) or a 4.5kg (racing). As yet to spend a sleepless nite. Yes mine is a lite set-up and I would not recommend it to anyone but I know the products very well and will be happy until 35-40kts odd. After that 8mm chain and 16mm warp, same anchors but just for the extra peace of mind. Had 35knts and 25+ in a biggish sea on this system and she felt fine in both, no snatching or nasty stuff except the warp did start to look a bit small. Actually I must remeasure the warp (polyester Octi) , I'm sure it must be a bit longer now /forums/images/graemlins/smile.gif

The minimum break load of that rode is over 2000kg so strength is not an issue. The anchors will hold over 1000kg even just in packed sand. I think I'd start losing bits off the boat before that /forums/images/graemlins/smile.gif

 

[Danny Jo]

[ QUOTE ]
I would down size the warp though, you need a fair bit of grunt to get 20mm Octi stretching nicely and I don't think you would have that.

[/ QUOTE ]

Thanks GMac. I discovered too late that I have oversized the Octi. Has anybody got a handy link to breaking strain and stretch characteristics of the different sizes? Google has let me down this time.

Regards

Mark

 

[Sea Devil]

[ QUOTE ]
The kellet is a single concentrated weight, by Alandee's definition the same as the anchor - or similar. It is intended to drag around, so minimizing sailing.


[/ QUOTE ]
I used a chum - kellet on a daily bases for around 7 years - no marinas only anchorages.
Different strokes for different folks but it is not intended to 'drag around'. It's purpose is to keep the centenary of the chain low so the anchor does not pull out upwards. It should not touch the sea bed rather be just above it.
I started using a Chum/Kellet when observing in the Bahamas my 8mm chain 'jump' out of the water in some dodgy conditions on a shallow anchorage.

By keeping the chain low in the water the anchor is less likely to break out - it also enables the boat to lay to the wind or current.... I think the New Zealand version is brilliant - fast and simple to use.

In the Marquesas and sometimes in the Caribbean there was a requirement to keep the boat on anchorage pointing in a certain direction.. I have an alloy 'Fortress' anchor with a little chain on it and lots of relatively light warp and would just row it out as a Stern anchor. Using warp is better really because if in more extreme conditions you want to get rid of it - I would tie a fender to the warp and sort it out later.. keeping the stern anchor light and using rode rather than chain makes setting and recovery easy.

 

[craigsmith]

[ QUOTE ]
...it is not intended to 'drag around'. It's purpose is to keep the centenary of the chain low so the anchor does not pull out upwards. It should not touch the sea bed rather be just above it.

[/ QUOTE ]Suggest you read Alandee's first post and then the rest of the thread that pertains to it.

[ QUOTE ]
...By keeping the chain low in the water the anchor is less likely to break out

[/ QUOTE ]See Fraysse's work already linked to - and the graphs in my post above.

 

[GMac]

Nylon 8 Braid (Octiplait, Brait, that platted stuff, Squarebraid and more)
12mm break 3200kg
14mm 4500kg
16mm 5900kg
18mm 6700kg
20mm 9200kg
Standard WLL is 20%. These are a good braid and most good braids would have very similar loads. Stretches sooner and more evenly than laid ropes hence better on rodes.

Polyester numbers are about 10% less but then Nylon loses 10% when wet so they are basically the same when in use.

DON'T use Polyester on a Auto Rope to Chain Winch. Even though a few manufacturer say you can, most users can't get it too when on the boat. We have not had big success and we can do upwards of a 100 R2C rodes a week.

 

[duncan]

[ QUOTE ]
No way would I go to a 25kg anchor on that

[/ QUOTE ] neither would I but the gentleman seemed desperate to do something - and was proposing to add about 30kg but concerned at adding 70 odd...........

10 seemed cheap - and 25 seemed to match 10mm chain and 20mm rope better than that 15 too.

on balance I think you have explained it better though

it is a pretty boat /forums/images/graemlins/smile.gif

 

[Danny Jo]

Thanks again, and apologies for hijacking the chum thread. I have also looked at Hylas's web page on the subject of anchor rodes - this generally supports the advice already given.

My conclusions are:

1. A chum or chums might be handy for a restricted anchorage in light to moderate winds, but setting one is a bit of a palaver (what with: heaving it/them out of the bilges; shuffling along the deck without dropping it on your toes, on the deck, or in the sea; fastening it to the rode and lowering it as far down the rode as it will go), and more or less useless in strong winds, when what is needed is lots of scope and lots of stretchy nylon.

2. In attempting to equip myself for anchoring in strong wind, I acquired a Fortress anchor two sizes larger than recommended for my boat, but made a mistake in thinking that I must have a longer chain. Increasing the total rode length from 70 to 100 m would certainly help. In heavy weather conditions there is little if any catenary whatever rode you have, chums and all, particularly when the force peaks as the boat pitches, etc. A longer rode is necessary to keep the angle between the rode and the sea bed as small as possible, and the pull on the anchor as near to horizontal as possible. In these conditions having plenty of nylon in the rode helps reduce the snatch loads.

3. So my existing rode will get a wash, rusty bits touched up with cold galvanizing paint, and move aft as a spare. The working rode will be 35 m 10 mm chain plus 65 m 16 mm nylon, and I'll have 25 m spare chain - a £145 mistake. I think I'll need a stiff whisky before I cut into that 60 m length.

Mark

 

[Mirelle]

Before you cut it...

...since you can obviously accomodate the weight, why not just rolling hitch the nylon to the chain? For 98% of the time you can anchor on chain alone.

For the remaining 2% you can then pay out say 20 metres of nylon and have 5 metres of chain in hand to allow for stretch in the nylon. This covers you for 99.9% of the time and you will sleep the better for having the chain as well as the nylon.

You are only going to need the whole lot on the thousandth occasion and in that case surely it is better to veer 60 metres of chain and 65 metres of nylon?

 

[Danny Jo]

Good point. Might try loading the chain into the anchor locker to see whether it makes any difference in a sea.

Mark

 

[Sea Devil]

[ QUOTE ]
[ QUOTE ]
...it is not intended to 'drag around'. It's purpose is to keep the centenary of the chain low so the anchor does not pull out upwards. It should not touch the sea bed rather be just above it.

[/ QUOTE ]Suggest you read Alandee's first post and then the rest of the thread that pertains to it.

[ QUOTE ]
...By keeping the chain low in the water the anchor is less likely to break out

[/ QUOTE ]See Fraysse's work already linked to - and the graphs in my post above.

[/ QUOTE ]

I know I am really old fashioned but the theory frequently does not match the reality on a daily basis over 7 years.. I assure you that you do not want it dragging over coral - rocks snags et al.. which is the reason for not allowing it actually onto the sea bed - rather just above..

It is a most useful tool and an essential part of the kit if you anchor on a daily bases in lots of different places. The new zealand version is easy to link onto the anchor chain, runs on rollers down the chain and is easy to recover. Recovery is important when you need to get out of the anchorage when conditions deteriorate and you need to put to sea.. That's frequently why its better than setting two anchors... These are practical reasons - not theory.

 

[duncan]

couldn't agree more - if you've got it then at least check out how it fits and see how it affects the boats handling / response to short swells etc

I think we all agree that in extremes a long (10/12:1) rode is one of the first insurances you can use.

The only other small consideration would be the weight to be lifted - but as long as you avoid anchoring in 65m of water ............. /forums/images/graemlins/crazy.gif

I might suggest a dedicated snubber line of 12mm if he sticks to the full chain length. 5m length with a chain hook at one end and I have a spliced loop at the other. this will rig easily and soften any snatch at all esp in shallow anchorages.

Freestyle - 16mm sounds a lot better; I am sure you will notice the difference when you need it.

 

[Mirelle]

Very much agree with that.