[Rhodes22-list] Did I wrote that??

[Bill Effros]

Alain,

As you also noted, many of the standard formulas make no sense.  People 
read formulas, with safety margins built in for huge boats, and try to 
apply them directly to much smaller boats.

When I started  to learn about anchoring last summer, a lot of what I 
read made no sense, and didn't work when tried.

I came to believe that fluke surface and the ability to drive those 
flukes into the bottom were the most important factors where I sail.

Our 22 foot boats have 8 to 9.9 hp motors.  In reverse, these motors 
lack the power to drive anchor flukes deeply into the bottom.  Adding 
chain is a hindrance--add enough chain and we can't even drag the chain 
across the bottom when there is no wind on the surface, much less drive 
the flukes into the bottom.  Then the wind picks up, and the boat starts 
moving.  In most cases it is "dragging chain" not "dragging anchor".  
The anchor was never set in the first place, and is just lying somewhere 
on the bottom.

I use floating anchor rode.  I use little or no chain.  I can see when I 
am driving the flukes into the bottom because all of the line disappears 
from the surface.  I can use a sextant to determine scope--by applying 
sufficient force at the proper angle I can drive any properly sized 
anchor into the bottom where it will hold until I free it.  The harder 
the wind blows, the more deeply my anchor sets.  My line never sits on 
the bottom, so it is never damaged by an "aggressive" bottom.  I can 
anchor better without chain than with it.

Bill Effros




Alain POIRAUD wrote:
> Hi Bill, 
>
> We have done tests with only chain and no anchor, we have found that (on
> sand) the force needed to start dragging the chain was approximately twice
> the chain weight (the part lying on the bottom). A meter of 10 mm chain,
> weight 2.25 kg  - this means for 30 meters, 67.5 kg.. or nearly nothing..
> (if the chain is not rounded around a big boulder!) 
>
> What is important is not really the weight of the rode, but the scope.. 
>
> Table 6: Estimated Percent of Maximum Holding Power as a function of the
> scope to water depth ratio
>
>                 Scope to water depth ratio	2/1	   4/1	    6/1	    8/1	   
> 10/1	   ∞/1
> Percentage of maximum holding power	10 %	55 %	70 %	80 %	85 %	100 %
>
>
> and you are fully right , with strong wind, that anchor chain section will
> be lifted off the bottom at the “NEARLY”  the same angle as the rope
> section?
> And when you are launching your anchor, if the anchor chain section lying on
> the bottom weighs more than the force of the wind on the boat, that anchor
> chain section will perfectly  hold the boat so that the boat cannot drive
> the flukes of the anchor into the bottom. That’s the reason why, after you
> launch the anchor and pay out enough scope, you should always go backward ;
> first slowly and then when the anchor hold (and stop the boat) at full RPM. 
>
> This will drive the flukes of the anchor into the bottom and tell you if
> your anchor hold well. 
>
> Alain, 
>
> --
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