By simoncurrin - 29 Dec 2012
Does anyone have any experience of using high tensile g70 chain and trading down to a smaller guage? From what I have read on www.morganscloud.com etc. 8mm x g70 is as strong as 10mm x g40 which means that either we could carry more chain or carry less weight. I guess it comes at a cost (don 't know how much) but is there another snag? Obviously we would have to change the gypsy too.
Simon
|
By YACHTMATADOR - 30 Dec 2012
Interesting concept. Not sure about strength but I 'm sure you have researched that bit. The weight saving might be the bigger issue. The reason your anchor digs in is because of the catenary effect of the chain caused by it 's weight. So if you use a lighter chain you need more scope. Remember the difference if you anchor on warp. You will probably find the extra length you need amounts to the same weight you had on the shorter heavier chain, and you had to change the Gypsy. Also if you go to crowded anchorages you will for ever be telling others that they are too close as you have a longer scope than expected. I 'd stick with the heavyer stuff.
Stu
|
By David.Tyler - 30 Dec 2012
I 've heard that the higher tensile, higher carbon chains are more susceptible to corrosion.
I have a 10.5 metre boat, with 75m of 8mm chain, and I have to suffer a lot of tooth-sucking from my cruising friends who also go to wild places, who say it 's too light, I should be using 10mm. I know it 's strong enough. Once, when I got the anchor irretrievable jammed under boulders and had to cut the chain, it didn 't yield until I was halfway through the second half of the link, although it was snubbing heavily at the time. Strength is not the issue. Weight certainly is. The first duty of ground tackle is to be heavy. (Who was it who said "the first duty of wine is to be red"? One of the French philosophers, I think).
|
By simoncurrin - 30 Dec 2012
Thanks for your feedback. I have been digging a bit deeper and found a good review on the Rocna knowledgebase. Their comment on catenary is as follows, "Except in very deep water, chain and its catenary has very little effect on the ultimate performance of an adequately sized modern anchor. The chain 's effect on lowered pull angle and its shock absorption characteristics disappear in the rough weather when they are most required, and the anchor is best helped in other ways. More on this topic is found in the Rode optimizations and Scope vs catenary articles."
"It is not necessary to carry heavy chain merely for the sake of it. Rather, chain can and should be as light as possible, subject to strength requirements. Many boats could lose a large amount of weight by swapping to a lighter but stronger chain, and then investing part of that weight back into a larger anchor. Performance (holding power) of the system is thus substantially improved, while total weight is actually lowered. Find more, including recommendations for chain sizes, in the chain section".
Of course how much lf this is science and how much is gut feel is open to conjecture. i will keep researching for now.
The Rocna link is http://www.rocna.com/kb/Chain
And http://www.rocna.com/kb/Scope_vs_catenary
|
By David.Tyler - 30 Dec 2012
"It is not necessary to carry heavy chain merely for the sake of it. Rather, chain can and should be as light as possible, subject to strength requirements. Many boats could lose a large amount of weight by swapping to a lighter but stronger chain, and then investing part of that weight back into a larger anchor. "
I do actually agree with this. That 's why I have a 20kg Rocna, instead of the 15kg that they and other anchor manufacturers would recommend, and only 8mm chain, instead of the 10mm chain that my friends would recommend. But I do think that I 'm right at the top end of the size range, for the practical use of 8m chain.
Catenary might have little effect on the ultimate performance of an adequately sized modern anchor (I read that as meaning "Rocna or Manson Supreme"), but it certainly has a marked effect on the overall, day-to-day performance of any anchor. It remains true that "the chain anchors the boat, and the anchor anchors the end of the chain". A boat that roams around the anchorage, with too light a chain, or chain and warp, is not only a nuisance to others, but uncomfortable for the crew.
|
By cverlaque - 2 Jan 2013
Is there another snag? Yes, if the new chain, while having the same breaking point weighs less. The weight of the chain contribute to the holding power of your ground tackle and you may have to put more chain out to have the same holding power as with the heavier chain. The catanary effect of the chain was reduced. We experienced that in the Med when we traded our 3/8 chain for 5/16 high tensil. We came back to 3/8 and would habe bigger if I could manage it! Christian
|
By DariaBlackwell - 6 Jan 2013
Christian, what type of anchor did you use with the lighter chain?
|
By cverlaque - 6 Jan 2013
We used both a 45 lb CQR and a 33 lb Bruce with a catanary of 15 lb about (2 lead ingots tied together and hooked to a ring sliding along the chain. Very good holding with that system but you have to retrieve the ingots before bringing up the anchor. Spent 3 years in the Med with that system. We know have a 55 lb Rocna which we like very much. Christian
|
By simoncurrin - 6 Jan 2013
I think I am now clear that the chain weight will not reduce the absolute holding power of our over sized Manson Supreme though it may increase the amount of roaming around the anchorage. My next dilemma is how to find a shackle for an 8mm chain that matches that matches the strength of either high tensile 8mm or ordinary 10mm. It seems to me that this is going to be the weakest link by a significant margin.
Simon
|
By David.Tyler - 7 Jan 2013
You 'll need to use a 17-4PH high tensile stainless steel shackle. Here 's one source:
http://www.s3i.co.uk/lifting-shackle.php#axzz2HFLV6PCd
And I think Wichard make them, too.
|
By simoncurrin - 22 Oct 2014
Just thought I should update this thread. After all the research and comments I just bought 8mm x 100m of high tensile G70 chain along with a new gypsy. The chain comes with an over sized end link so the shackle should not be the weak point. Not sure I 've saved any weight though as I 'm so nervous about it we will probably still carry our old 10mm and 10mm gypsy but has dramatcally increased the length of chain we can carry in the anchor locker. Will report back how we get on next season.
Simon
|
By DariaBlackwell - 22 Oct 2014
Thanks Simon, we 're in the market for new chain, too, so we 'll be very interested to learn of your experience. How much chain do you have now? Also where did you buy your chain?
|
By simoncurrin - 22 Oct 2014
Daria,
Jimmy Green had an offer on though the price still makes me flinch. Add to that the new gipsy. The link is http://www.jimmygreen.co.uk/item/19660/8mm-din766-aqua-7-calibrated-galvanised-chain--discount-lengths
We have upgraded primarily because we are hopefully heading to the Greenland Fjords in the next year or two where the bottom can be a long way down (like it was in Pig Bay). So I think we now have the following:
Bower 100m of g70 8mm on 45kg Manson
2nd anchor 60m of g40 10mm on 25kg Delta (which I hate)
Kedge 30m of g40 8mm on 20kg Bruce
And 50m of 16mm nylon spliced to 20m of 10mm chain
Only hope the boat still floats and I am sure we will lose a knot or two because of the above.
Simon
|
By Dick - 9 Aug 2015
I know this is an old topic, but I will use this to suggest a way of thinking about choosing chain that flies in the face of some sailor 's common sense.
When it comes to choosing chain, I would suggest the only criteria be chain strength and not weight. I would go further and say that all observations of chain providing centenary effects and a better angle of attack (anchor to sea bottom) are entirely accurate for conditions where they are least important: Mild to moderate winds. When wind strength reach Near Gale forces or above, especially if sea state picks up, your chain is going to be frequently 2 blocked (bar tight link to link). It is then that your snubber and only your snubber will average out the forces and keep your anchor from being snatched from the bottom. As to the angle of attack anchor to sea bottom, scope is the primary determinant as in these more boisterous conditions, the chain will be regularly bar tight and dampening effects then will be provided by the snubber.
It is possible that you might delay the 2 blocking of the chain one force by going, say, from 8mm to 10mm chain, but in gale and storm conditions 2 blocking is inevitable and needs to be planned for.
So, I would suggest, buy chain for strength and take any extra weight and put it in an anchor, Spade or Rocna, where it will do far more good. Also be confident your snubber system is up to the task of averaging out forces.
Dick Stevenson, s/v Alchemy
|
By simoncurrin - 16 Aug 2015
Dick,
I hope you are right as I just switched from 60m of 10mm to 100m of 8mm keeping the former as a second anchor. Did this in readiness for the deep fjords of Greenland next year. Just back from a super trip around the north of Iceland and have left the boat in a very secure winter Reykjavik berth. Certainly the logic of the longer, stronger chain is very persuasive.
Simon
|
By Dick - 18 Aug 2015
Hi Simon,
Glad you had a great trip and a safe berth for your boat.
There is an easy way to confirm my observations. When next watching boats in breezes above 25-30kn watch the chain of the boats. At any reasonable scope, they will be close to 2 blocked fairly regularly. It gets worse quickly as the wind increases and especially if the seas become part of the load induced forces.
When 2 blocked the major contributing elements to keeping your boat attached to the bottom are anchor weight and design, length of scope and the averaging of forces capacity of your snubber. After that the strength of your weakest element is the next consideration. If there is a choice of where to put weight, put it in the anchor where it will do the most good and not in the chain where, in higher force winds, it will have a negligible effect.
Write back if you have a chance to observe the above and share your observations. (Or others if they wish.)
My best, Dick Stevenson, s/v Alchemy
|
By Alex_Blackwell - 18 Aug 2015
Dick
Thank you for stating that so clearly and emphatically. We have written about the uselessness of kellets and the lack of dampening with chain on many occasions. Our personal observation is that our chain rode (100m 12mm chain) goes bar taut at about 40 knots. Plenty of scope so the anchor does not pull out and a long stretchy snubbber to take up the chock loads are vital.
|
By Dick - 20 Aug 2015
Hi Alex, Agree completely. With regards to kellets/sentinels there is one reason to carry one. In squirrelly anchoring situations where you have 2 anchors out and one is primarily of nylon , I always use a kellet. This is not so much to decrease the angle of attack, anchor to sea bottom, but rather to keep the nylon rode from having the opportunity to foul on the keel, rudder or prop in these squirrelly situations.
My best, Dick Stevenson, s/v Alchemy
|
By Alex_Blackwell - 21 Aug 2015
I agree with you here Dick. only the kellet need only weigh in at a pound or three - enough to keep the rope weighed down. We use this for any time we anchor with a rope rode in light air conditions, where the boat may swing around and over the rode.
Your 'normal ' kellet will weigh 30-40 pounds....
[quote="Dick" post=2317]Hi Alex, Agree completely. With regards to kellets/sentinels there is one reason to carry one. In squirrelly anchoring situations where you have 2 anchors out and one is primarily of nylon , I always use a kellet. This is not so much to decrease the angle of attack, anchor to sea bottom, but rather to keep the nylon rode from having the opportunity to foul on the keel, rudder or prop in these squirrelly situations.
My best, Dick Stevenson, s/v Alchemy[/quote]
|
By H Holden - 30 Apr 2016
Does anyone know a source of Calibrated G70 5/16in chain - 8mm is metric equivalent which we know doesn 't fit but with an old imperial gypsy which we can 't change we are searching for the imperial size to fit the gypsy on our old SL windlass? Maybe somewhere in USA even though we are currently UK based?
|
By simoncurrin - 30 Apr 2016
Helen,
I don 't know where you can get calibated imperial chain from in the UK but I am sure either Dick, Daria or Alex will be able to point you in the right direction. We just used our new 8mm g70 chain for the first time and enjoyed having almost double the capacity of chain in our locker which is very handy in deep fjords.
Simon
|
By Alex_Blackwell - 2 May 2016
Hi Helen,
We had the same problem - our chain spec was 7/16th inch. I started with corresponding with the manufacturer - Ideal Windlass, who were, shall we say, somewhat ambiguous in their response. Their final response was a little longer is better than shorter
On the face of it, you are correct, that your spec should be 8mm:
5/16in = .3125in = 7.937500mm
However, the important measurement is the outside length of your chain link. We found that "calibrated" chains from different manufacturers do not necessarily have the same link length. our metric equivalent is 11.11250mm, and Ideal eventually said 12mm "should work".
I ordered 10m of 12mm chain to test from one manufacturer. It jammed on our windlass, as the links were too short. As an aside, our old chain also jammed on out Gypsy/wildcat. It had a 60mm link length. We finally found a 12mm chain with a 65 mm link length through a chandlery - incidentally at a very good price. Again I ordered a 10m test length and it ran through absolutely perfectly. The two 10m lengths are now attached to our backup rope rodes, and we have 100m of lovely new chain.
So, why the lengthy story? 8mm is the correct diameter for your Gypsy/wildcat. You just need to find a chain with the correct link length. Measure precisely what you have. Presuming that the old chain is working for you, specify that link length stating that a little longer may be acceptable. Then get a sample; it will never go to waste....
|
By Ginger - 3 May 2016
Hi Helen,
Try Maggi in Italy.
They will ship most anywhere in Europe and have a US distributor in Fort Lauderdale. For G4 they have duplicated the very popular US 5/16 G4 ACCO chain and may have done the same with the G70.
Let us know how your researches go.
My best, Dick Stevenson, s/v Alchemy
|
By Ginger - 3 May 2016
Hi Alex,
I was thinking the kellet for the conditions I was referring to: contrary currents and sometimes opposing wind (Bahamas being a prime example) needs more than a couple of pounds to keep the nylon rode from finding its way to trouble. Mine is home made from dive weights and I long ago forgot its weight, but I would say pushing 20 pounds/8 kilos. The 1-3 pounds you suggest would hardly make a dent in a nylon rode that has any real pressure on it.
My best, Dick Stevenson, s/v Alchemy
|
By H Holden - 3 May 2016
Alex, thanks for your reply. I 'm off to measure the exact sizes and then do some phone calls. Already got some samples as you 'd suggested but more effort obviously required in this direction. Will post update on any success I have. Thanks H
|
By H Holden - 3 May 2016
Thanks Dick, will follow this lead up also and keep you posted.
|