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Old 08-01-2012, 10:45   #61
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Re: Chain versus rope scope?

I once read a book by a guy named.... Griffiths?...... He advocated using polypropolene anchor rode! Something like 1" diameter. Very lightweight and he made it work for him. Cant remember how often he had to replace it, but based on my experience with Poly used for little things after I went cruising... wow... that stuff turns to dust pretty fast if left in the sun. Cant remember, maybe he had a sun sleeve on it from the bow to the water or something. I do like it for a dingy painter; lightweight and it floats. You better change it now and then though! I guess any system can be made to work if you know YOUR system. For me, I like to sleep well and the all chain option just does that better for me.
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Old 08-01-2012, 10:46   #62
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Re: Chain versus rope scope?

Quote:
Originally Posted by Ex-Calif View Post
It is still not science...

I go from 30 lb anchor to 31 pound anchor and throw away 100 lbs of chain? I think not...

Rules of thumb are guesses by their very nature...
I think that Ex-Calif is correct here -- these ratios come out of thin air and we shouldn't get caught up in them.

On the other hand, Nick is right that weight of the chain is not as helpful as weight in the anchor. Actually, I think he understates his case -- the difference (speaking unscientifically now) is probably more than 100 to one. It approaches infinity as the last meter of chain is lifted off the seabed and the chain straightens out.

Weight in the anchor, on the other hand, is always exerting a force which tends to bury it in the seabed. It's true that actual holding force comes from fluke area, but it's the weight of the anchor which, to a large degree, keeps those flukes engaged in the seabed.

I would say actually that density of the anchor must also play a role, maybe more significant than weight -- it's the density relative to the material of the seabed which determines the extent to which the anchor tends to sink in it. Maybe that's why Spades work so well -- they have a good bit of lead in them. Makes me dream a bit of a tungsten anchor, but then again -- at adequate fluke area it would probably be too heavy to handle, not to mention cost . . .
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Old 08-01-2012, 11:03   #63
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Quote:
Originally Posted by Ex-Calif

It is still not science...

I go from 30 lb anchor to 31 pound anchor and throw away 100 lbs of chain? I think not...

Rules of thumb are guesses by their very nature...
No, you don't throw anything away. Please try to follow me. You keep the chain at the same length and strength. You only make it lighter by selecting a smaller diameter made from a stronger steel. The weight saved you put back in the anchor. This is not difficult to imagine I thought.

Now in real world example because I sense people don't understand this yet. Lets say we have 250' of 3/8" G43 chain which weighs 382.5 pounds and a 66 pound anchor, total weight is 448.5 pound so let's make that 450 pounds for easy math.

Now we anchor with all 250' of chain out and measure holding power. We call that number "x".

Next step is new anchoring gear. We take 250' of 5/16" G70 chain which weighs 250 pounds. 450-250=200 pounds. So we buy the same type of anchor we had before but now a 200 pound model instead of the 66 pound one used in the previous test. Our total weight is the same 450 pounds. Our total rode length is the same 250'

Now, my statement is that with this lighter chain and 200 pound anchor, your holding has increased to 10x - 100x.

Go try it out if you don't believe it

cheers,
Nick.
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Old 08-01-2012, 11:06   #64
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Originally Posted by Dockhead
Makes me dream a bit of a tungsten anchor, but then again -- at adequate fluke area it would probably be too heavy to handle, not to mention cost . . .
Take depleted uranium.. It's free to grab in Iraq :S

ciao!
Nick.
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Old 08-01-2012, 11:11   #65
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Re: Chain versus rope scope?

If you drag in low or medium wind strengths , you will notice a significant increase in performance is you put weight into the rode, but if your anchoring gear, and technique are sound the improvement in holding from a heaver rode will be very small, at higher wind strengths.
In both cases, but particularly in high wind strengths, weight taken out of the rode and put into the anchor will always be beneficial., and I think its hard to argue otherwise. For example with my boat and 100m of chain if I swap my 13mm chain for G7 10mm chain I save 155Kg in weight. Does anyone really think I would hold better with say a 30Kg anchor and 13mm chain or a 185Kg anchor (wow) and 10mm chain ? Do you own sums based on your circumstances.
The exact ratio of benefit is hard to estimate, and will probably be an educated guess, but the message is clear, put as much weight into the anchor and as little weight in the rode as possible, for best performance.
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Old 08-01-2012, 11:34   #66
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@Noelex,

Exactly. The thing I would add is that for light winds you should never drag and thus the whole discussion around that is irrelevant. The anchoring system must be designed for bad conditions and that makes it perfect for benign conditions automatically.

I believe that the "disbelieve" of this issue is largely driven by the higher cost of the better system. I would just say sonething like "it's way better but I don't have the cash to buy that" instead of trying to discredit it. Dashew has been on it for 20 years and still we get this turning and twisting to try to make it go away haha

I don't know the original author but the following quote comes to mind:

The three phases of Truth:

1. Ridicule
2. Attack
3. Acceptance

We are at least in phase 2 ecause I don't hear much Fisherman anchors with killets arguments anymore

ciao!
Nick.
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Old 08-01-2012, 11:37   #67
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Re: Chain versus rope scope?

You guys have no idea how much I am learning by this discussion.

Thanks, and please keep the comments coming. I am probably not the only neophyte who is wondering. Great links, BTW.
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Old 08-01-2012, 11:50   #68
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Re: Chain versus rope scope?

Ok so on my 34 ft 10,000 lb cataman what weight of anchor do I pick ?
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Old 08-01-2012, 11:52   #69
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Re: Chain versus rope scope?

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Ok so on my 34 ft 10,000 lb cataman what weight of anchor do I pick ?
hmmm... I'd probably go 35 lb, larger if a Bruce... but for world cruising might go up to 45.
The higher up you go in Chain grade to save weight, the more corrosion prone it becomes.... another trade off. I hear the Russians make Titanium chain... :>)
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Old 08-01-2012, 11:56   #70
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Re: Chain versus rope scope?

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Ok so on my 34 ft 10,000 lb cataman what weight of anchor do I pick ?
You need to start with deciding which type/brand of anchor as that makes huge differences on weight. Next you look up the manufacturer's guidance on weight for storm anchor. Now you need to understand that this is often for 30 knot winds which for us cruisers is just a nice breeze. So go 2 sizes larger and now you're getting close. Check measurements if you can fit a bigger anchor. If so, and budget allows, go to higher grade chain one size down and the bigger anchor. You normally even save a lot of weight in this step, compensating for the initial step up to a bigger size. Important for a cat.

cheers,
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Old 08-01-2012, 11:59   #71
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Re: Chain versus rope scope?

I bought an origional 35 lb CQR but don't know where to get data on sizeing, I just guessed when making our purchase. Should I melt lead and attach it to the anchor ?
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Old 08-01-2012, 12:02   #72
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Re: Chain versus rope scope?

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Very enlightning reading Makes me feel our cat is well set up with enough chain, rope, snubber line, along with a kettle if I need one Now all I need is about 400 ft of line to stearn tie to shore far some locaions in the Pacific North West and I'm sure other locations.
If you go on craigslist you can find climber's line fairly cheap, which works great for med mooring. I picked up two 200' lengths of 7/16" for $40 each.
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Old 08-01-2012, 12:06   #73
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Quote:
Originally Posted by webejammin
I bought an origional 35 lb CQR but don't know where to get data on sizeing, I just guessed when making our purchase. Should I melt lead and attach it to the anchor ?
The CQR .. I would try to sell it again. And no matter what anchor, you need to go at least to 50 pounds.

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Old 08-01-2012, 12:13   #74
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Re: Chain versus rope scope?

I'm afraid if I go to 50 lb my arthertic back can't lift it if my windless was to go out.
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Old 08-01-2012, 12:16   #75
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Re: Chain versus rope scope?

If you goto Second Wave here in Seattle you'll see they have CQR's up their ass. They're a dime a dozen They have a bad rep. and for good reason with the swivel pin falling out. You have to keep an eye on them.

Here in the PNW I use a bruce (Claw) for most areas and a Delta where I know there is sea grass. I'd like a Ronca but can't justify the cost since my others are doing just fine.
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