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#51 Dtwo

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Posted 26 June 2019 - 10:44 PM

Tempting, but no. 8>)


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#52 wheels

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Posted 27 June 2019 - 05:02 AM

 

BUT

 

if a situation occurred were the chain was bar-tight

Completely impossible to do. That is assuming you the correct chain size for the boat has been selected. KM and I have proven this belief as impossible many times on the test bed. The load required to pull chain straight is huge. Which also, if one thinks about it, if the chain was straight, the anchor shank would lift and the anchor would pop out. This is why there is the rule of thumb that you use 1.5x length of Boat of chain when a rope rode is used. It is next to impossible to lift even that small length up from the bottom and have the anchor let go. Once again, providing the correct sizing is being used.
The Chain, when under load, seemingly bar tight and straight when viewed from the Bow is where this notion comes from. But further on down under the water, the Chain takes a big curve and eventually will run along the bottom to the anchor shank. That shank must remain down at all times so as it only digs down deeper as load applies.

And with that, it should also be a dead giveaway as to what loads KM's hypothetical load cells would "see".


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#53 Knot Me... maybe

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Posted 27 June 2019 - 11:00 AM

I can't find the last set of trial numbers so will have a wee play later if I get a moment.


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#54 Chrisc

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Posted 28 June 2019 - 09:09 AM

A lot of theory going on here.
I originated the discussion not because I stumbled upon the Rocna website and got seduced by their arguments - I first began to consider the chain cantenary thing well prior to my original post and that was during a cyclone which concentrated my thoughts as to the efficacy of my anchor and rode considerably.
To reiterate:
Anchored on a mud bottom in 4 metres of water by way of a 30lb Manson Supreme with 30 metres of 8mm chain, no snubber. Wind consistently well in excess of 60 knots for 12 hours. Sea conditions were flat. The boat was an H28.
I normally use a 16mm nylon snubber but was concerned about chafe. The chain was bar tight, and yes I accept that bar tight does not mean dead straight. In a previous post above I satisfied myself that whereas it is not possible to pull 10 metres of 8mm chain straight, it is quite easily possible to pull that amount of chain by hand to an 8cm deflection. Now that's not a lot of cantenary.
Back to the cyclone.
The boat was consistently snatching at the chain with such violence that I had serious concerns that I was going to loose the mast and the bits were going to be pulled out of the foredeck. So I put a rolling hitch around the chain of 16mm nylon, put a good few turns around the windlass drum and paid out a few metres. That is not something that you do lightly in those conditions with the risk of losing control of the boat and squishing a few fingers as well. So why would the boat snatch so viciously at the chain if there was a cantenary effect to dampen things down?
Secondly, with a bit of nylon in the rode the boat became much more mannerly, and that enabled me to lie on the foredeck and more or less sight along the bar tight but not really rope/chain rode by which I was able to see that it intersected just below my anchor float, possible parallax error and difficult conditions accepted.
And that is what I saw, and that is why I question.
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#55 wheels

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Posted 28 June 2019 - 12:33 PM

I originated the discussion not because I stumbled upon the Rocna website and got seduced by their arguments - I first began to consider the chain cantenary thing well prior to my original post and that was during a cyclone which concentrated my thoughts as to the efficacy of my anchor and rode considerably.

 

Don't rely too heavily on the info on that site.


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