[Rhodes22-list] anchoring
ben
benonvelvetelvis at theskinnyonbenny.com
Thu Sep 18 09:39:36 EDT 2008
Yeah, 12 feet is as deep as I usually have to deal with. I only have a few
feet of chain, and probably 100 feet of nylon rode, so it's easy to manage.
But if I were anchoring in 60 ft water, I would definitely put out 400 feet
of rode, give or take. Maybe not to have lunch, but if I were going to
leave the boat and go ashore, or go in the cabin for a night of sleep, then
yes.
Note that I only use the one anchor. Don't you usually set more than one?
Maybe it makes more sense to me in that case.
-----Original Message-----
From: rhodes22-list-bounces at rhodes22.org
[mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of Bill Effros
Sent: Thursday, September 18, 2008 7:07 AM
To: The Rhodes 22 Email List
Subject: Re: [Rhodes22-list] anchoring
Ben,
If you are right you will be able to convince me.
You sail on Lake Pontchartrain? Average depth 12 feet?
So you can carry 100 feet of anchor rode and have enough to anchor at
7:1 pretty much anywhere you go.
I sail on Long Island Sound -- average depth 63 feet, so you think I
should carry over 400 feet of anchor rode -- which I actually do carry.
However, the Sound is more than 200 feet deep in many parts, and reaches
more than 350 feet deep in some. You can't seriously suggest that
people with big anchors should be carrying more than a ton of chain, or
that I should carry more than a quarter mile of anchor rode.
There must be some other answer.
And the answer is that some types of anchors are just as effective with
less scope. Excellent Danforth anchors like the Fortress are designed
to be used at a 45 degree angle or less, down to 35 degrees or something
like that. If maintained at that angle they won't pull out. The angle
at which the rode enters the water will vary with the freeboard, the
distance from the top of the water to the bottom, the height of the
attachment point of the anchor to the bottom, and the distance you move
your boat from dead over the anchor.
If you have 100 feet of chain, and drop it and the anchor into 12 feet
of water without moving your boat, you can put all your chain into the
water at a 90 degree angle and be unable to set your anchor despite the
fact that you have 7:1 scope.
I am suggesting a rule of thumb for people learning to anchor, and that
rule of thumb, for a Fortress Anchor, would be to set the anchor when a
taut rode enters the water at a 45 degree angle or less. This will
"tip" the anchor in such a way that the pull of the rode forces the
tines into the bottom at an optimal angle that will hold securely, but
that you will still be able to release by getting directly above the anchor.
You cannot determine scope from the single angle of the rode entering
the water. You are constructing Isosceles triangles because you insist
on two 45 degree angles when I have recommended just one as the maximum
angle for setting a specific type of anchor.
Bill Effros
ben wrote:
> I know I'm not going to convince you, but if you put out more than 1.5:1
> scope, you're making your angle lower than 45 degrees. If the rode is
taut
> and you have 6:1, the rode is going to pull up at about a 10 degree angle.
> That's what you want for holding.
>
> True, it's probably overkill in lots of situations, but tides rise, wind
and
> currents change, etc. Chain keeps that angle lower, so you get more
holding
> power from less rode.
>
> Ben
>
> -----Original Message-----
> From: rhodes22-list-bounces at rhodes22.org
> [mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of Bill Effros
> Sent: Wednesday, September 17, 2008 10:12 AM
> To: The Rhodes 22 Email List
> Subject: Re: [Rhodes22-list] anchoring
>
> Ben,
>
> Setting anchors has nothing to do with triangles -- I made reference to
> a single angle.
>
> I am not suggesting short scope. I set with very long scope utilizing a
> 45 degree angle or less. Because the surface of the water is
> essentially parallel to the bottom, you can look at the angle at the
> surface to understand the approximate angle of pull on the bottom.
>
> Like you, I have discovered the problem with properly set Danforth
> anchors is releasing them, even when you are almost directly above them,
> once they are properly set.
>
> Bill Effros
>
> PS -- The Standard Issue R-22 Anchor looks pretty, but is a lousy
> anchor. The cladding defeats the purpose of the flukes. A Fortress
> will exactly fit, but it rattles. I always anchor from the stern,
> anyhow, so I just leave my pretty blue anchor in place hoping someone
> will steal it someday. So far, no luck.
>
>
>
>
>
> ben wrote:
>
>> 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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