[Rhodes22-list] Anchoring -- Phuzzy Physics

[pawyrick at peoplepc.com]

Hi all,
Great fun watching the debate. I know nothing about physics and just 
learning about sailboats. I know from experience that with a Danforth style 
anchor, they can be set in even strong current, with or without chain, if 
the bottom is right. Being a long time powerboat guy, from 10 to 42 feet, I 
prefer the chain, particularly if I'm going to be on the hook for an 
overnight. If I'm just fishing, it doesn't matter much to me. Without the 
right bottom, plan to drag all over the place, even when the physics is 
right.
Phil
----- Original Message ----- 
From: "Bill Effros" <bill at effros.com>
To: "The Rhodes 22 mail list" <rhodes22-list at rhodes22.org>
Sent: Thursday, January 12, 2006 11:43 AM
Subject: Re: [Rhodes22-list] Anchoring -- Phuzzy Physics


> 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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