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Old 08-01-2012, 22:05   #106
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Re: Chain versus rope scope?

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Originally Posted by Ex-Calif View Post
Here is an area Nick and I can totally agree on. Coral is extremely fragile. There are many many many dive sites all over Asia destroyed by anchoring and diving.

Please take care around coral reefs! Choose the sandy bits and definitely dont tie off on coral heads.

Totally agree, No intention of buggering up any Eco system. I live in a Provincial Park. Question was an honest one.
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Old 09-01-2012, 03:00   #107
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Re: Chain versus rope scope?

Look guys, all this nice talk about not anchoring in coral... you don't have to be on a pristine reef, or even a very ordinary one to encounter coral. A great many anchorages here in the South Pacific islands are primarily sand bottoms, nothing too precious, and thus quite reasonable to anchor in. But, sticking up out of that sand, here and there are little bits of coral, mostly dead. It is pretty easy to get your rode foul of one or more of these bits, and they will shred a rope rode in a very short time. And having a composite rode (some chain followed by rope) only helps to a degree, for the rope bit will likely get onto some coral in the fullness of time.

I simply can't understand how anyone could seriously go cruising in such areas with anything but chain. But then I'm kinda dense at times...

And for what it is worth, Jedi Nick is right on in advocating putting weight in the anchor rather than in chain... once you have satisfied the requirements of strength. We've chosen to use moderately large chain (10 mm) in G40 grade, but mostly for it's ability to absorb abuse and wear over years of cruising without compromising its strength significantly. I'd certainly be happy enough with 8 mm G-something better and an 80 lb Manson instead of our 60 lb one. I personally don't know how many angels can dance on the head of an anchor, but whether one achieves a 100x gain for a pound of anchor or only 10x or even 2x, there is an undeniable increment in holding power with bigger anchors, and only ancillary gains in holding power from heavier chain. Whats to argue?

Enough!

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Old 09-01-2012, 04:07   #108
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Re: Chain versus rope scope?

Well after all this I still feel I have a great setup for the Pacific NW I'm using my 35 lb CQR with 125 ft of 3/8 inch chain and 250 ft of 5/8 in rode. we usually anchor in 10 to 15 ft of water and rairly use any rope except for windy weather, I do use a snubber rope that hooks to the cleat beside my windless and it is long enough to use on our winch. I feel when hoisting our anchor we have plenty of chain to grab in the windless instead of rope that might not pull as good on a windless if the anchor is stuck under rocks or gunky mud bottoms which is typical. I also have 2 other second anchors with plenty of chain and rode on each.

I guess after our recession and rents go up I'll buy another modern anchor heavier too (50 lb ), but for now we've never dragged and our windless usually pulls our boat down several inches when hoisting our anchor out of the mud straight up which to me means it is holding ok.
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Old 09-01-2012, 04:24   #109
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Re: Chain versus rope scope?

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Originally Posted by s/v Jedi View Post
See how you completely ignore everything I wrote in my post and start with another angle where I would doubt ppropriateness to blindly add weight to anchors. Which has nothing to do with anything I just wrote. And I never said anything like that.

Why don't you reply to my post and explain where I go wronh with my math that shows holding improved 100x ?

ciao!
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OK, guys, let me try to help. Sorry if it turns out that I only make it worse!

I think that what Nick is saying is something like the following, and I think I might be able to express it in a way which is less frustrating to Ex.

Let's say we're at anchor with X amount of chain out with a good anchor that weighs Y.

Up to a certain force, say, what the hypothetical boat encounters in 15 knots of wind, for example, the holding is 100% from the chain and 0% from the anchor. Then as the force on the rode exceeds what the chain can hold by itself, the load is gradually transferred to the anchor. At some further point of increasing load, let's say for example at 30 knots, the chain becomes bar tight and ceases to add anything at all to holding. At that point 100% of the holding force comes from the anchor and 0% from the rode.

So at that point -- after 30 knots -- any weight at all which is subtracted from the rode and added to the anchor (and let's assume that weight and fluke area are directly proportional -- as is true in real life with a given anchor type) increases the holding.

So in my opinion you are both right and just not understanding each other. Ex is right that you can't express the advantage of shifting weight from rode to anchor with a single ratio.

Nick is right that the improvement in holding is extremely disproportional, which you get from shifting weight from rode to anchor. I think, however, that Nick understates his case -- the improvement is not 100x -- it becomes infinite (after our hypothetical 30 knots where the chain is doing nothing), because the denominator is zero. By "improvement", I mean the value in holding power of one kg in the anchor, versus one kg in the rode -- the way the problem was originally expressed.

And at the other end of the scale, the improvement in holding will be zero below a certain wind force. The lighter we make the chain, the sooner we transition to chain-only holding to holding both by chain and anchor. We will not start to get any improvement in holding until the chain goes bar tight.

Can we all agree on this? As Nick said, we assume that breaking or bending force is not part of the equation -- we don't propose to reduce the weight of the chain to 1 gram, or indeed to any number which would reduce its safe working load below what we need.

Another point: All of this is relevant only in conditions where the chain is bar tight. Many cruisers never ever anchor out in such conditions so the benefit may be hypothetical. However, since tough conditions is exactly where you care about ultimate holding power, it is still the right thing to do, if you want to maximize the efficiency of your ground tackle.
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Old 09-01-2012, 04:45   #110
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pirate Re: Chain versus rope scope?

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Anchoring in coral.

Chain and then rode or all chain?

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Old 09-01-2012, 05:07   #111
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Re: Chain versus rope scope?

1 anchor weight does seem important. a friend with a CQR welded a large shoe-plate to the bottom of it and filled it with lead. he has NEVER dragged, all round oz. also the round nose of the shoe does not cut thru coral. in any case, for chafe protection and comfort in normal conditions, the bottom one third should be chain, i believe

2 i know that rode: depth ratios are - chain = 3:1 rode, and if rope =5:1. However i have a further question:

3 what is the recommended breaking strain of any rode relative to displacement of vessel? my yacht is 15 T and has 8mm chain, no problems - but its hard to get a manufacturer to cough up the stats for chain! 10T to breaking?

also, presumably stretchiness of a rope rode is preferable, so one would choose nylon over pp over pe over dyneema, even if breaking strains are equal. 20mm nylon I have seen on yachts my size is manufacturer rated at 5-8T to breaking [at 30% stretch], which implies an answer to my question. any opinions or horror stories please?!

thnx

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Old 09-01-2012, 05:14   #112
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Re: Chain versus rope scope?

Quote:
Originally Posted by Shanaly View Post
1 anchor weight does seem important. a friend with a CQR welded a large shoe-plate to the bottom of it and filled it with lead. he has NEVER dragged, all round oz. also the round nose of the shoe does not cut thru coral. in any case, for chafe protection and comfort in normal conditions, the bottom one third should be chain, i believe

2 i know that rode: depth ratios are - chain = 3:1 rode, and if rope =5:1. However i have a further question:

3 what is the recommended breaking strain of any rode relative to displacement of vessel? my yacht is 15 T and has 8mm chain, no problems - but its hard to get a manufacturer to cough up the stats for chain! 10T to breaking?

also, presumably stretchiness of a rope rode is preferable, so one would choose nylon over pp over pe over dyneema, even if breaking strains are equal. 20mm nylon I have seen on yachts my size is manufacturer rated at 5-8T to breaking [at 30% stretch], which implies an answer to my question. any opinions or horror stories please?!

thnx

J
3:1 is a very skinny scope. It might hold you on heavy chain in moderate conditions and excellent holding. Unless there is some compelling reason, however, I always put out at least 5:1 and usually 6:1 even in benign conditions. In tough conditions I put out everything I've got and like to see 8:1.

As to breaking strength, I would follow the anchor maker's recommendations for the type of anchor you have. The required strength of the rode will follow more from the type of anchor, than from the type of yacht.
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Old 09-01-2012, 05:26   #113
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Re: Chain versus rope scope?

you shouldn't be using your winch for that, your yachts forward motion should break out the anchor.
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Old 09-01-2012, 05:51   #114
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Re: Chain versus rope scope?

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a friend with a CQR welded a large shoe-plate to the bottom of it and filled it with lead.
Sorry, but that's a poor substitute for a larger (and better) anchor. The recommendations about putting weight into your anchor assumes that the upgraded anchor possesses more mass and surface area.

Colin
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Old 09-01-2012, 06:08   #115
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Re: Chain versus rope scope?

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Originally Posted by Dockhead View Post
OK, guys, let me try to help. Sorry if it turns out that I only make it worse!
I completely agree with your assessment Dockhead... but I wouldn't dare to start with the infinite improvement of holding

p.s. ExCalif, I don't get mad at you; I get mad at myself for being unable to explain this to you or to zoom in on the precise part that isn't clear.

ciao!
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Old 09-01-2012, 06:15   #116
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Re: Chain versus rope scope?

The problem with using Spectra line to connect the chain hook, is that eye splice is going to be chafe... The Spectra line will eventually cut through the braided line.

You might consider splicing an eye into the braided line with a thumble and using a shackle to attach the chain hook...

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Originally Posted by noelex 77 View Post
Thanks. I have gone through a period of snapping snubbers (and they make a frightening bang when they go) so I am intersted in other peoples set up.
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Old 09-01-2012, 06:23   #117
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Re: Chain versus rope scope?

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The problem with using Spectra line to connect the chain hook, is that eye splice is going to be chafe... The Spectra line will eventually cut through the braided line.

You might consider splicing an eye into the braided line with a thumble and using a shackle to attach the chain hook...
Yes, I have considered that. However, after 10 years of using this kind of snubber, the eye splice was never chafed by the lashing. The snubber is 3-strand, not braided, but that wouldn't really matter I think.

The whole idea of this snubber is to NOT use metal hardware like thimbles and shackles which becomes a rusting mess. It turned out that this design works very good, better than any other design I've seen and tried, so I have put it on my blog years ago and keep referencing to it.

The thing that ends the life span of these snubbers is chafing where it touches the chain. The only way around that would be to use a bridle setup. I tried that and hated it, so now I always have a spare snubber and replace one after every 3 years of use.

ciao!
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Old 09-01-2012, 06:41   #118
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Re: Chain versus rope scope?

The question would be why would you let your anchor chain or line go "Bar Tight"?

Unless you are in a hurricane you probably have the option of letting out more scope...

More scope wth chain rode increases the cantanry to the anchor and provides less pull on the anchor itself, causing better holding...

This is the oposite with line, which is not heavy enough to provide cantanry in heavy seas/winds. In other words, it will pull tight to the anchor quicker than chain in the same distance.

Thus, if you have minimal chain and lots of line, you should go with a larger anchor, keeping within the limits of your windless.

If you have all or mostly chain rode a larger anchor is not needed as long as you have enough chain to provide proper scope for cantanry.

The other thing that many boaters don't think about is the windless when considering anchor size... I have seen several cruisers down here go with the bigger is better anchor theory. The problem being that their wndless didn't agree to the extra weight and fail, which can be a huge issue if you sporting an all chain rode and are in the middle of no where.










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Originally Posted by Dockhead View Post
OK, guys, let me try to help. Sorry if it turns out that I only make it worse!

I think that what Nick is saying is something like the following, and I think I might be able to express it in a way which is less frustrating to Ex.

Let's say we're at anchor with X amount of chain out with a good anchor that weighs Y.

Up to a certain force, say, what the hypothetical boat encounters in 15 knots of wind, for example, the holding is 100% from the chain and 0% from the anchor. Then as the force on the rode exceeds what the chain can hold by itself, the load is gradually transferred to the anchor. At some further point of increasing load, let's say for example at 30 knots, the chain becomes bar tight and ceases to add anything at all to holding. At that point 100% of the holding force comes from the anchor and 0% from the rode.

So at that point -- after 30 knots -- any weight at all which is subtracted from the rode and added to the anchor (and let's assume that weight and fluke area are directly proportional -- as is true in real life with a given anchor type) increases the holding.

So in my opinion you are both right and just not understanding each other. Ex is right that you can't express the advantage of shifting weight from rode to anchor with a single ratio.

Nick is right that the improvement in holding is extremely disproportional, which you get from shifting weight from rode to anchor. I think, however, that Nick understates his case -- the improvement is not 100x -- it becomes infinite (after our hypothetical 30 knots where the chain is doing nothing), because the denominator is zero. By "improvement", I mean the value in holding power of one kg in the anchor, versus one kg in the rode -- the way the problem was originally expressed.

And at the other end of the scale, the improvement in holding will be zero below a certain wind force. The lighter we make the chain, the sooner we transition to chain-only holding to holding both by chain and anchor. We will not start to get any improvement in holding until the chain goes bar tight.

Can we all agree on this? As Nick said, we assume that breaking or bending force is not part of the equation -- we don't propose to reduce the weight of the chain to 1 gram, or indeed to any number which would reduce its safe working load below what we need.

Another point: All of this is relevant only in conditions where the chain is bar tight. Many cruisers never ever anchor out in such conditions so the benefit may be hypothetical. However, since tough conditions is exactly where you care about ultimate holding power, it is still the right thing to do, if you want to maximize the efficiency of your ground tackle.
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Old 09-01-2012, 06:53   #119
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Re: Chain versus rope scope?

Quote:
Originally Posted by jeremiason View Post
The question would be why would you let your anchor chain or line go "Bar Tight"?

Unless you are in a hurricane you probably have the option of letting out more scope...

More scope wth chain rode increases the cantanry to the anchor and provides less pull on the anchor itself, causing better holding...

This is the oposite with line, which is not heavy enough to provide cantanry in heavy seas/winds. In other words, it will pull tight to the anchor quicker than chain in the same distance.

Thus, if you have minimal chain and lots of line, you should go with a larger anchor, keeping within the limits of your windless.

If you have all or mostly chain rode a larger anchor is not needed as long as you have enough chain to provide proper scope for cantanry.

The other thing that many boaters don't think about is the windless when considering anchor size... I have seen several cruisers down here go with the bigger is better anchor theory. The problem being that their wndless didn't agree to the extra weight and fail, which can be a huge issue if you sporting an all chain rode and are in the middle of no where.
Okay so how much scope would you set to prevent the chain becoming tight? How many anchorages have enough room to accommodate you like that between all the other boats anchored there?

So yes, of course if you set crazy enough chain you don't need an chore anymore. If I set 1,000' chain it might hold me using my dinghy anchor. But if that is practical? I think less chain and bigger anchor is more practical and much lighter to carry with the boat.

All the broken windlasses I've seen were broken because of operator error, never because of the anchor or chain being too heavy. Lack of snubber or chain stopper is #1 error. Using the windlass to break free the anchor is #2 error.

ciao!
Nick.
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Old 09-01-2012, 07:11   #120
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Re: Chain versus rope scope?

Your are right that a 1000 feet of chain is ridiculous!

Enough chain depends on the size of the vessel... My 37,000 lbs boat does not pull the chain tight at 5 to 1 scope in 40 knots of wind.

Depending on the water depth, that could be 250 feet of chain, before it starts pulling on the anchor...

So in regards to anchorage size, I carry 300 feet of chain, but rarely anchor in water exceeding 35 feet.

Using common sense, unless you are in some extreme water depths and absolutely have to anchor in deep water, you should never exceed the limits of your anchorage size in regards to chain length. If you did, you probably shouldn't be anchoring there to begin with, especially if your expecting heavy winds.

As far as owner error, you are right... Many times oners use the windless to pull the boat to the anchor and it will burn out the brushes. The other frequent cause, which does happen a lot, is the owners think bigger is better and purchase an oversized anchor, which in combination with the chain weight overloads the windlass and burns it out.

Many owners don't realize it until they are anchored in deeper water and the weight of the chain and anchor exceed the pulling power of the windless and subsequently the motor overheats. So yes, you could attribute that to owner error.


Quote:
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Okay so how much scope would you set to prevent the chain becoming tight? How many anchorages have enough room to accommodate you like that between all the other boats anchored there?

So yes, of course if you set crazy enough chain you don't need an chore anymore. If I set 1,000' chain it might hold me using my dinghy anchor. But if that is practical? I think less chain and bigger anchor is more practical and much lighter to carry with the boat.

All the broken windlasses I've seen were broken because of operator error, never because of the anchor or chain being too heavy. Lack of snubber or chain stopper is #1 error. Using the windlass to break free the anchor is #2 error.

ciao!
Nick.
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