[Rhodes22-list] Anchoring -- Phuzzy Physics

[Bill Effros]

Dave,

I, too, have read the "horizontal pulling force" theory of anchor rode 
chain.  As soon as you think about your mechanics and physics, you will 
know that it's rubbish.

When your boat pulls your anchor into the bottom, the anchor rode 
becomes taut.  The angle of the rode is exactly the same whether or not 
you have any chain between the anchor and the point on your boat where 
the rode is tied off.

The anchors we use dig in properly at an amazingly wide range of 
angles.  Horizontal is not one of them.  Vertical is also not one.  
That's what the whole notion of "scope" is about--putting the rode at 
the proper angle to cause the flukes to dig in. 

These anchors set properly despite the fact that people put chain in 
their rode, not because of it.

Bill Effros


DCLewis1 at aol.com wrote:

>Bill,
> 
>There’s no way I’m an expert at anchoring, but I do know a bit about  
>mechanics and physics. You’re certainly right about an anchor’s generally  sinking, 
>but the chain rode issue may be about  how the anchor engages the  bottom, 
>and stays engaged with the bottom -  not about sinking the  anchor.  Consider an 
>anchor on the bottom with sufficient chain rode, if  there is a pull from the 
>anchor line with any vertical component, the weight of  the rode can 
>counteract the effect of the vertical pull and ensure  that forces on the anchor are 
>horizontal (i.e. notionally  parallel with the bottom).  I believe anchors are 
>really made to deal with  horizontal forces; the anchoring effect is achieved 
>primarily by  flukes, plows, or other appurtenances optimally engaging the 
>bottom, and  that requires horizontal forces.  Without the rode, any substantial 
>pull on  the anchor line that has a vertical component may cause the anchor to 
>lift  vertically, in which case it may not engage properly, or at all, with 
>the  bottom.
> 
>Dave
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