[Rhodes22-list] anchoring

[ben]

Yeah, Bill is wrong on this one.  Think about it.  45 degrees is essentially
putting out 1.5 times as much rode as the depth you're anchoring in.  (Draw
it -- it's a right triangle with the anchor rode as the hypotenuse).

I've never seen any article or source recommend less than 5:1 scope.  

But more importantly, I use the standard issue R22 danforth in mud all the
time.  I overnight in gunkholes or bayous regularly in the spring and fall,
and in summer, I drop the hook mid-lake so I have the boat as a big swim
platform.  Everything you read is right.  The more rode I put out, the
better it holds.  If I put out 10:1 or 12:1 -- which I sometimes do
overnight if there's current or wind -- it's darn tough to pull out the
anchor, even once I'm directly above it.  Many times, I've had to use the
winch to break it out of the mud.

Maybe other anchors and bottoms are different, but I'll go with the
literature on this one, because I know it's correct.

Ben S.
R22 Velvet Elvis


-----Original Message-----
From: rhodes22-list-bounces at rhodes22.org
[mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of John Lock
Sent: Wednesday, September 17, 2008 9:02 AM
To: The Rhodes 22 Email List
Subject: Re: [Rhodes22-list] anchoring

At 11:52 PM 9/16/2008 -0400, Bill Effros wrote:
>The point is that the anchor most of us use is designed to set by being
>pulled at a 45 degree angle from the bottom.  If you pull it parallel to
>the bottom it just stubs its flukes along and never sets properly.  And
>if you have too much chain, you can never pull it at a 45 degree angle,
>so it will never set at all.

Let me jump in and say I have to disagree with Bill here.  As I 
understand the physics of the Danforth-style anchors, they actually 
depend on a certain amount of horizontal (or parallell) movement to 
get the points of the flukes to dig in.  Here's why...

With the flukes hinged at the back of the anchor and free to rotate 
about that axis, their mass, pulled downward by gravity, will have a 
natural tendency to rest directly on the points.  Consequently, an 
initial horizontal movement will naturally force the points downward 
and into the mud.  Pulling up on the rode at a 45-degree angle will, 
in fact, help defeat the design by not allowing the mass of the 
flukes to perform their downward deflection.

The main reason a few feet of chain helps an anchor set is that the 
extra weight helps keep the initial movement of the anchor more 
horizontal, because the rode will begin to rise before the chain 
does.  This helps the flukes get their initial "traction".  Once the 
points dig in and force continues to be applied the rode and chain 
can rise and increase to the 45 degree angle that is ideal to finish 
and maintain the set.  It's those first few inches of movement that 
are critical to the set of the anchor.

Cheers!

John Lock
~~~~~~~~~~~~~~~~~~
s/v Pandion - '79 Rhodes 22
Lake Sinclair, GA
~~~~~~~~~~~~~~~~~~

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