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post #1 of 14 Old 09-30-2009 Thread Starter
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Anchor Chain

OK - Dumb question time:

On our first sailboat, the anchor rode was a length of chain (approx 20ft?) secured to about 300ft of nylon (?) anchor line. When we set the anchor, I simply cleated off the line to one of the bow cleats and that was that...

However, our current boat has about 200ft of chain. I haven't anchored out in her yet, but when I do, How do I go about securing the anchor chain to the boat? All I remember seeing up front is the anchor chocks and the bow cleats. I'm in the process of trying to see what's up with the SL Hyspeed winch, but I've read the owner's manual and picked up on the issue of NOT depending on the windlass to secure the chain to the boat. How then, DO you 'tie off' the chain?

V/R

Dave

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post #2 of 14 Old 09-30-2009
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Here's one way Dave. From reading I think this is the general idea most folks use.

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post #3 of 14 Old 09-30-2009
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Or you can buy a chain hook, and add your own rope. For the total of about $40 max?.......i2f
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post #4 of 14 Old 09-30-2009 Thread Starter
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Imagine: Is there a functional difference between the standard M1/A1 chain hook and the one found on the 'CPT Hook' commercial product?

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post #5 of 14 Old 09-30-2009
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Any boat using long lengths of chain should have a chain-stop installed between the roller and the windlass - see here:
www.rocna.com/kb/Chain_stops

Unfortunately many production boats skip them, although they are usually a fairly easy retrofit.

In addition to the chain stop a nylon snubber is usually advisable. Chain hooks have a number of drawbacks, see the mention in the below link, the line tied to the chain is preferable.
www.rocna.com/kb/Snubbers

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post #6 of 14 Old 09-30-2009
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kellets...

Adding a "Kellet" is another way to introduce sag into the rode and increase the horizontal tension. A Kellet is simply a lead weight that is attached somewhere along the rode. Letting the Kellet drop all the way to the chain gives the most increase in tension, but many sailors prefer a half way point, under the theory that it helps absorb shock loads better. The effects of a 20 pound Kellet, placed at 100 feet, is shown in Figure 3. The inflection point at 100 feet is clearly evident, and the maximum tension increases to 280 pounds, over three times more than the original all nylon rode.

any of u lads use a kellet? self made? knot used to tie it along the rode?
any other thoughts?
 
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post #7 of 14 Old 09-30-2009
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Kellets are a slight waste of time and a huge waste of weight. They do nothing to assist any reasonably sized anchor's ultimate holding power and similarly provide no real shock absorption. Where did you get that paragraph from stpetersburgsailor? - certainly there is no "increase in horizontal tension" - this is total rubbish.

Take a look at the cold hard facts here: www.petersmith.net.nz/boat-anchors/kellets.php

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post #8 of 14 Old 10-01-2009
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Craig thanks for the laugh amigo, u remind me of my English father with the "total rubbish" comment

surely though a weight between two points will increase tension... basic math/logic?

the source is this random link, enjoy
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post #9 of 14 Old 10-01-2009
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Yes most of that page misses the point and contains some basic inaccuracies as above.
The tension in the section of rode between the kellet and the boat is increased yes, but it comes from an increase in the vertical forces (from the kellet weight). The only horizontal forces acting on the rode are the boat (wind & current) and the reaction from the anchor! Obviously that extra vertical force is what lowers the angle of pull on the anchor, the tension in the rode between the kellet and the anchor staying the same... but the relative numbers are pretty weak, hence the above article pointing out the same; a 10 kg weight don't do much when there's a tonne of load in the system

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post #10 of 14 Old 10-01-2009
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I hope you aren't the engineer over there at Rocna, you seem to be missing some of your basic statics knowledge. Lets say:

Tsin(theta)+Tcos(theta)=T

Then if we can lower the angle of incidence (theta) by any means, we can greatly reduce the magnitude of T for a given horizontal force component.

"Obviously that extra vertical force is what lowers the angle of pull on the anchor, the tension in the rode between the kellet and the anchor staying the same..."

The tension in the rode between the kellet and the anchor will be lower in magnitude. This is simple trigonometry.

I don't know what you mean by the relative numbers being weak, but I do know that most anchor rodes are sized with an ultimate tensile strength greater than the force required to move an anchor. The implication being that sentinels, or kellets, are indeed a good idea, in that they can increase any anchors holding power. Of course anchor companies have a vested interest in discouraging their use, when they could sell a larger, read "more expensive" anchor as the alternative solution.

If you require a more rigorous mathematical model, I suggest you pm me.
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