JimC
Well-Known Member
I'm sure it would, 6 mm chain has a breaking load of around 2 tons depending on the grade, so you could hang your boat on it.
http://www.jimmygreen.co.uk/p/technical/chandlery-technical-articles/chain-strength-weight-guide
Anchors , Chain and Warp
- Thread starter jakeroyd
- Start date
I'm sure it would, 6 mm chain has a breaking load of around 2 tons depending on the grade, so you could hang your boat on it.
http://www.jimmygreen.co.uk/p/technical/chandlery-technical-articles/chain-strength-weight-guide
sarabande
Well-Known Member
There is much discussion on the snatch loads on chain for a yacht at anchor.
John Know's excellent site,
http://www.anchorwatch.co.uk/
is a good background and technical read.
Peter Smith from New Zealnd also put a load cell on a 40ft boat in Patagonia, and came up with figures of an 8 tonne momentary load.
I agree with hlb, whose view is that weight of chain on the ground is key to sleeping soundly with a properly dug in anchor.
8mm is not too large for a small boat. It weighs just under twice as much as 6mm, so the catenary effect is much more marked, giving a good snubbing function as an aid to mitigating snatch.
John Know's excellent site,
http://www.anchorwatch.co.uk/
is a good background and technical read.
Peter Smith from New Zealnd also put a load cell on a 40ft boat in Patagonia, and came up with figures of an 8 tonne momentary load.
I agree with hlb, whose view is that weight of chain on the ground is key to sleeping soundly with a properly dug in anchor.
8mm is not too large for a small boat. It weighs just under twice as much as 6mm, so the catenary effect is much more marked, giving a good snubbing function as an aid to mitigating snatch.
Highndry
Well-Known Member
Like most things it becomes a compromise though. My little Medina will sail much better with 35 kilos of chain, rode and anchor sitting on the nose than it would with 50 kilos.
Would it be practicable to join a 10m length of 6mm (often unused) to a length of 7mm chain at the anchor end as a compromise? Strength-wise it would only be as good as the weakest link but would improve the catenary effect. How would you go about connecting 6mm chain to 7mm chain most effectively?
JimC
Well-Known Member
I think you'd be fine with just the 10 metres of 6mm chain, backed up with ample rope of course. Personally I'm a bit sceptical about the value of the catenary effect with chain rodes. When you really need the shock-absorbing effect of the catenary in extreme coditions is just when the catenary doesn't exist because the chain is taut, as seen here http://www.youtube.com/watch?v=TXPC8RcOGeo . Follow this link for a more reasoned discussion on anchor rodes and the virtues of chain versus rope etc http://www.bluemoment.com/anchorrodes.html
doug748
Well-Known Member
I followed the link....
"The main and ONLY advantage of the chain is that it is the only and perfect mean to avoid chafing of the anchoring rode on agressive sea beds...
Except for this point, chain has all the disadvantages..: "
This opening shot did not fill me with confidence.
jakeroyd
Well-Known Member
Just picking up on the catenary effect.
My anchor was holding initially with my 6m of quarter inch chain and 15m of warp.
However , I noticed that the angle to the horizontal was maybe 30 deg.
All the other boats in the DH looked like more like 60 or 70.
Thinking back this I think was due to catenary if they were using all chain.
My initial 6m of quarter inch would only weight about 0.8kg per metre , say 5kg total. This would easily be lifted off the sea bed by the boat.
My new set up with 8mm chain at 1.35kg per metre would be more like 20kg , 4 times more.
My anchor was holding initially with my 6m of quarter inch chain and 15m of warp.
However , I noticed that the angle to the horizontal was maybe 30 deg.
All the other boats in the DH looked like more like 60 or 70.
Thinking back this I think was due to catenary if they were using all chain.
My initial 6m of quarter inch would only weight about 0.8kg per metre , say 5kg total. This would easily be lifted off the sea bed by the boat.
My new set up with 8mm chain at 1.35kg per metre would be more like 20kg , 4 times more.
vyv_cox
Well-Known Member
I suspect you are describing the situation in fairly light winds. Once it gets to about force 6 almost all rodes will be off the bottom. I have dived on our anchor in the Med in 30 knot winds, shallow water, only about 2.5 metres with 30 or 35 metres of 8 mm chain out. The whole lot was lifting off the bottom regularly.
In similar situations but where it has been very gusty we deploy the kedge at about 90 degrees from the bower. The bower is a Rocna, all chain. The kedge is a Fortress, 7 metres of chain and 16 mm octoplait. At the anchors there is virtually no difference in the appearance. As the boat yaws each rode goes bar tight.
In similar situations but where it has been very gusty we deploy the kedge at about 90 degrees from the bower. The bower is a Rocna, all chain. The kedge is a Fortress, 7 metres of chain and 16 mm octoplait. At the anchors there is virtually no difference in the appearance. As the boat yaws each rode goes bar tight.
vyv_cox
Well-Known Member
The late Alain (Hylas on these forums) did have quite a thing about this subject. Many did not share his opinion. Many of his objections are easily overcome by the use of a decent snubber, my two metres or so of 12 mm nylon easily cope with snatching loads.
In the Med, where stern-to berthing on anchor is so common, all the advantages are with chain. I have seen both rope and chain rodes wrapped around another boat's propeller. You can guess which came off worse.
KellysEye
Well-Known Member
>6m of chain with 15m of warp. We were in a range of 4-6m with all of the warp out.
I realise this is a bit light on scope.
Definitely lack of scope. The depth determines the scope the shallower it is the more scope you need. And if using rope and chain even more. The weight in the catenary is the most important thing. For example in 4 to 6 metres we would use a minimum of 7 X depth using all chain. 20 meters we use 3 x depth all chain. I haven't used rope and chain but I would guess you need 50% more + than the amount we use. My vote would be go all chain, then you can sleep well.
On the subject of CQR's we've seen many lying on ther side, they simply haven't been dragged to set them. We have one and it works well.
I realise this is a bit light on scope.
Definitely lack of scope. The depth determines the scope the shallower it is the more scope you need. And if using rope and chain even more. The weight in the catenary is the most important thing. For example in 4 to 6 metres we would use a minimum of 7 X depth using all chain. 20 meters we use 3 x depth all chain. I haven't used rope and chain but I would guess you need 50% more + than the amount we use. My vote would be go all chain, then you can sleep well.
On the subject of CQR's we've seen many lying on ther side, they simply haven't been dragged to set them. We have one and it works well.
John Barry
Well-Known Member
A good guide is to have 1mm chain width per m of boat length, and to have 2 boat lengths of chain. You should then have at least 5 more boat lengths of warp (2mm/m).
A 7.5m boat with 15m of chain and 15m of warp will have a horizontal pull on the anchor in 15Kn of wind and 7m depth (including freeboard). With that setup you'll get 5° of angulation at 19Kn of wind (most anchor can cope with 5° of angulation).
A 7.5m boat with 15m of chain and 15m of warp will have a horizontal pull on the anchor in 15Kn of wind and 7m depth (including freeboard). With that setup you'll get 5° of angulation at 19Kn of wind (most anchor can cope with 5° of angulation).
lw395
Well-Known Member
My personal experience suggests that CQR's work a lot better with a weight some way down the rode. For a 40ft boat I had about 10kg of lead far enough down the rode that is was always clear of the bottom.
I believe it helps the CQR re-set when the tide turns and also helps with snubbing.
Certainly if you are anchored in choppy water, it allows the bow to move up and down more easily.
It's cheap to try compared with a new anchor anyway.
I believe it helps the CQR re-set when the tide turns and also helps with snubbing.
Certainly if you are anchored in choppy water, it allows the bow to move up and down more easily.
It's cheap to try compared with a new anchor anyway.
Cloven
Well-Known Member
Last boat was a Hunter Horizon 272 which had a similar set-up to yours - CQR pattern anchor with 10m of 8mm chain and lots of warp.
Soon after getting the boat we changed to a genuine 10kg Bruce with 35m of 8mm chain. Never once had a problem with dragging after that and often anchored in mud. Delta lived in the bow roller OK.
Present boat, a Hunter Channel 323 came with a CQR pattern Harbourfast anchor & 10m chain + warp etc. We changed that to a 10kg Delta, again with about 35m of 8 mm chain spliced to 50m of warp "just in case". No problems to date.
One thing to think about, in popular muddy anchorages, the mud can get sort of liquefied where anchors are used a lot and holding seems to get less predictable. Fortunately with the Hunter being a twin keel we could (and still can) often go much shallower than other boats and so can anchor in the less favoured parts.
Hope this helps
Soon after getting the boat we changed to a genuine 10kg Bruce with 35m of 8mm chain. Never once had a problem with dragging after that and often anchored in mud. Delta lived in the bow roller OK.
Present boat, a Hunter Channel 323 came with a CQR pattern Harbourfast anchor & 10m chain + warp etc. We changed that to a 10kg Delta, again with about 35m of 8 mm chain spliced to 50m of warp "just in case". No problems to date.
One thing to think about, in popular muddy anchorages, the mud can get sort of liquefied where anchors are used a lot and holding seems to get less predictable. Fortunately with the Hunter being a twin keel we could (and still can) often go much shallower than other boats and so can anchor in the less favoured parts.
Hope this helps
jakeroyd
Well-Known Member
Hello again Dave W
Thanks for your feedback , I guess I could do the same (keep a new anchor in the roller/stem head) I would just have to cut a hole on the locker lid for the chain and possibly fix up a wear plate or guide to stop the chain chafing the fibreglass.
I'll see how I go with the new chain.
Thanks for your feedback , I guess I could do the same (keep a new anchor in the roller/stem head) I would just have to cut a hole on the locker lid for the chain and possibly fix up a wear plate or guide to stop the chain chafing the fibreglass.
I'll see how I go with the new chain.
Cloven
Well-Known Member
Channel 323 has a feed channel for the chain but on the Horizon 272 we just had a small cutout at the front of the anchor locker lid.
When at anchor the chain was always held with an anchor snubber with the rope end round one or other of the cleats so there was no chaffing on the GRP.
With the anchor on the roller, again there was no chaffing as the chain was under no load.
When at anchor the chain was always held with an anchor snubber with the rope end round one or other of the cleats so there was no chaffing on the GRP.
With the anchor on the roller, again there was no chaffing as the chain was under no load.
