Anchor weights and connectors

purplerobbie

purplerobbie

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I have just got another anchor for my boat (good swap eh?) the make is unimportant. It is about 45lb and its on 70 meters of 10mm chain

When i stuck it on the front of the boat yesterday i thought it looked a bit big.
Is there any problem with having an anchor thats a bit big?
I have a lofrans windlass for getting it all up.

Connecting it to the chain.
Should i use a swivel or just a shackle? and if a shackle should i use stainless or galv one?
does a swivel make any difference?

The boat is 34ft and about 12tonne

Rob
 
I don't think a swivel is necessary, it's just a weak link. In fact they can prevent you rotating the anchor to the best posn for entry into the bow roller. The shackle is enough and a galvanised shackle is a better match with galvanised chain. However I use a stainless one, and one with a countersunk pin head (tightened with an allen key, not a screwdriver).
 
You can't have an anchor that's too big.

The only issues are whether it can be safely raised, properly secured and whether you are putting too much weight on the bows.

I do meet some boats with large anchors/lots of chain on the bows and heavy dinghies on their davits who wonder why they turn into rocking horses when going into weather.

A lot depends on hull shape, but as your boat is 12 tonnes I would have thought you were fine. Enjoy a better night's sleep!
 
The anchor is fine if you can handle it with your windlass and stow it securely.

I'd use a galvanised bow shackle. The bow shackle means that the shackle pin doesn't protrude beyond the overall width of the shackle as is the case with a dee shackle. Ideally the shackle will fit through the bow roller. If it doesn't you need to stop hauling before the anchor gets to the roller and then lift it over the cheeks of the roller.
 
I agree that you cant really go to big...unless...the increase in weight adversely effects your boats trim. You may find you hobby horse more with a lot of weight on the bow!
 
"However I use a stainless one, and one with a countersunk pin head (tightened with an allen key, not a screwdriver). "

That's what I use as well, and never had a problem during many anchorings.

FWIW I think that Evening Star shouldn't go any smaller with his anchor - it may look a bit big on a 34' boat, but it is 12 tons after all /forums/images/graemlins/smile.gif
 
I'm in the same boat as you (ha! ha!) having just put another 45lbs up front. I could have gone a size down and it would have fitted better but I'm happy enough. Just a new learning curve on which one to raise and lower now as I'm going to be doing some bahamian mooring.

If I ever get out of this bloody marina that is!

As to the weight thing do what I do. Keep buying more stuff to put at the back like a bigger dinghy and outboard. /forums/images/graemlins/blush.gif

Another reason I have to get out of here is so I stop buying stuff. Watermaker arrives on monday. /forums/images/graemlins/blush.gif

[/ramble]
 
[ QUOTE ]


FWIW I think that Evening Star shouldn't go any smaller with his anchor - it may look a bit big on a 34' boat, but it is 12 tons after all /forums/images/graemlins/smile.gif

[/ QUOTE ]

Is it boat weight or size or how much is under the water or how much is above the water or all of these things that matter?

You could have a 34ft bav that weighs only 4 tone could you get away with a 25lb anchor?

Rob
 
No.... Different boats characteristics have different influences when at anchor... a lighter boat will have greater windage and may sail around on the anchor more giving snatch loads from undesirable angles while a heaver boat may need more stopping when it accelerates backwards in strong gusts so all things being unequal they need the same size of anchor!!!
 
Yes, I did the testing and wrote the article. Kong connectors came out well, more to do with the design than the materials of construction.

For shackles, stainless is a lot better than galvanised, use a size bigger than the chain. Wichard 17/4PH shackles are about the best, they do one with a countersunk pin that avoids snagging problems.

I have since tested Loctite for holding the pin in place as an alternative to mousing, following comments on here that it is not waterproof. I found it to be perfectly OK after a season's immersion.
 
Vyv is spot on and here is some more detail
The YM Chain and Links test was in their Centenary Edition May 2006. The results were quite worrying.
A useful starting point is that 8mm chain has a breaking point of 4.93 tons. The weakest swivel was a Plastimo one from the Marine Superstore which had a breaking load of 1.87T. A mooring type eye/eye swivel had a breaking load of 2.76T.The Kong ones were better at around 4 tons.
A regular galvanised D-shackle fractured at 2.38T but a 10mm stainless shackle from Wichard with a countersunk Allen screw pin and rated for 4.3T was good for 5.36T.
Thats what I have got...NOW.
Personally I have never seen much point in swivel at the anchor. I think it actually makes it more difficult to stow. There is a role for swivel on a tidal mooring but that can be near the surface where it can be inspected.
Back to the Test. The components which were stamped or rated with a working load generally exceeded that rating. If you buy a cheap unmarked , unrated shackle or swivel of unknown origin you are taking a terrible chance with your boat and your life!!!
 
To put it into perspective, however, the load on a 36' cruising boat with sails furled is estimated to be around 550kg, in 60 knot winds.
The Working Load Limit on 8mm chain, recommended for a boat this size, is about 1000kg.
Unless there is a weak or faulty link in the connection system, such as a dodgy swivel or shackle, loose shackle pin or the like, the part of the system that will fail first is the anchor to bottom connection. And by some considerable distance in most normal anchoring situations. A 30' boat in a 40 knot gust will put little more than a 150 kg load on the anchor system.
So, whilst none of us wants to risk our boat to badly made componants, we should also be aware of the safety factor built into the typical anchoring system.
 
[ QUOTE ]
I have just got another anchor for my boat (good swap eh?) the make is unimportant. It is about 45lb and its on 70 meters of 10mm chain

When i stuck it on the front of the boat yesterday i thought it looked a bit big.
Is there any problem with having an anchor thats a bit big?
I have a lofrans windlass for getting it all up.

Connecting it to the chain.
Should i use a swivel or just a shackle? and if a shackle should i use stainless or galv one?
does a swivel make any difference?

The boat is 34ft and about 12tonne

Rob

[/ QUOTE ]
Certainly not too big Rob, chain sounds right, I don,t like swivels, not needed and don,t always work anyway, use a galv shackle, a s/s one will go with the galvanising on the chain, mouse it with galv soft iron wire, not monel, for the same reason. Bill.
 
Yes, there are several sources for these load figures. The figures I use were to some extent verified by work done quite recently, and published in at least one of the magazines, by load cell tests during a gale.
Anyway, the point is that the holding capability of most anchoring systems depends on getting the anchor set right.
Clearly it isn't wise to have a weak link in the system that would drop its capability close to that required to hold the boat. If the anchor drags you can re-anchor, if a shackle breaks you lose the anchor.
 
Thanks for that site, silver_fox. interesting. I found this as well for calculating catinary swag ratios, http://www.spaceagecontrol.com/calccabl.htm
Probably not exact for anchor chain as the attachment points aren't horizontal but fun to play around with. Must find ut how much my anchor chain weights per foot /forums/images/graemlins/ooo.gif I once tried this in a workshop in london, some guys downstairs with a loadcell, 100' of steel wire rope and a tapemeasure, me upstairs on tinternet, istr results were within a few percent of each other. Fun afternoon.


edit: Having nothing better to do i just did a quick cad drawing with figures from that web site, 30m chain at 2.1kg per metre with 500kg force in 8m water- angle of pull=10deg, same but with 40m chain, angle of pull=6.5deg. (obviously this a computer, not the real world) Now who's up for a bit of diving with a protractor next time there's 60Kn winds? /forums/images/graemlins/ooo.gif

Another edit:
This is what it looks like
catinary2.jpg

Which won't be correct as I think the webs site calculater presumes both points of attachment to be horizontal. And anyway is pretty much as any old seadog has been saying for hundreds of years "arr, that chain be doin' no good jus' sittin in the locker.." And nothing to do with the original question either - sorry.

And evening star
[ QUOTE ]
I have just got another anchor ..... the make is unimportant

[/ QUOTE ]
So glad you added that!!!! /forums/images/graemlins/grin.gif
 
[ QUOTE ]
Must find ut how much my anchor chain weights per foot /forums/images/graemlins/ooo.gif

[/ QUOTE ]
I looked into this when i was looking for chain and for 10mm its 2.1kg per meter


Rob
 
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