I am getting different advice on the recommended scope when anchoring.
Chapmans says 6-7 times the depth, whereas my Danish friend (Very
experienced sailor) says 3 times depth is sufficient, especially since I
have a heavy anchor and all-chain rode.

In the following hypothetical situation, what scope would the group
recommend:

38 foot sailboat
35 lbs anchor (Plow type)
all-chain galvanized steel rode (300')
mud bottom
sheltered anchorage - calm day - lots of other boats at anchor
High tide mark at 20 feet above bottom.

Appreciate any feedback!

cvj wrote:
I am getting different advice on the recommended scope when anchoring.
Chapmans says 6-7 times the depth, whereas my Danish friend (Very
experienced sailor) says 3 times depth is sufficient, especially since I
have a heavy anchor and all-chain rode.

In the following hypothetical situation, what scope would the group
recommend:

38 foot sailboat
35 lbs anchor (Plow type)
all-chain galvanized steel rode (300')
mud bottom
sheltered anchorage - calm day - lots of other boats at anchor
High tide mark at 20 feet above bottom.

Appreciate any feedback!



The Canadian Power & Sail Squadron seems to recommend what Chapman's does.
On a nice afternoon anchoring I might only put out 75-100 feet, but if
overnighting I'd sure as 'ell would drop the 175 feet.
note: 20 foot water depth + height from waterline to deck approx 25 feet

"cvj" wrote in message
. ..

38 foot sailboat
35 lbs anchor (Plow type)
all-chain galvanized steel rode (300')
mud bottom
sheltered anchorage - calm day - lots of other boats at anchor
High tide mark at 20 feet above bottom.

Whatever the boat, whatever the rode, the angle of pull at the
anchor should always be as horizontal as possible. If the angle
is greater than 10 degrees, you're increasing the risk of the
anchor pulling out. Whatever the rode, in windy conditions the
boat will ride from side to side, jerking that rode, lifting the
chain to almost straight from time to time. If you want a secure
dig, that lift must not go above 10 degrees. That implies six
times rode of your depth at waterline. At high water.

And if you're going to leave the boat, check the risk of the
wind/tide reversing. That may trip the anchor. In which case you
need to moor. Lay a second anchor and dig it to hold in the
opposite direction.

For a lunch stop in a calm, by all means drop twice or three times
your depth. That's not really anchoring - that's putting a weight
on the bottom. But it's easy, it's fun, and it's safe for a quick
stop when nothing's going to change.

Ignore people who talk catenaries, or who quote lesser amounts.
They're not talking dynamic conditions, which is what matters. Add
a nylon snubber to soften stress loads in waves - 10m metres
worth at least.

Some will differ from my views . . . some of those older books
also were written in the dark ages, when the science of anchoring
was passed on from generation to generation . . . and only applied
to their local waters.
--
JimB
http://www.jimbaerselman.f2s.com/
Describing some Greek and Spanish cruising areas

CVJ

must recommend another great anchoring text, Hinz, Earl R., "Anchoring
and Mooring." An absolute must have.

Go he

http://alain.fraysse.free.fr/sail/rode/rode.htm

Took me three minutes to search this group and find this info. Learn
how to learn.
Life long learner Bob

3 to 1 scope is on the marginal side. I've done it many times for lunch
anchoring where someone is always in the cockpit, but overnight I would
never use less than 5:1, usually I use 7:1.

In theory, with all chain you can get by with less, especially in deeper
water, but on small boats with no anchor watch, you want to be 100% secure,
95% just doesn't do it!

So what reason would you have to skimp? If the anchorage is tight, use two
anchors. If its too crowded for 5:1, go elsewhere. If you don't like
hauling the extra chain, buy an electric windlass. I shortened my chain
from 100 feet to 50 when I realized that my anchoring decisions were being
affected by a desire to avoid hauling a lot of chain. Nowadays I haul and
reset maybe half the time I anchor, making sure we're well and truly set
exactly where I want to be; with more chain I wouldn't be doing that.

BTW, if the mud is soft, a plow might not hold that well in a blow. I use a
Delta as the primary, but keep a Fortress on the bow to add in soft stuff.

One more thing, anyone who uses the word "catenary" doesn't really
understand anchoring.



"cvj" wrote in message
. ..
I am getting different advice on the recommended scope when anchoring.
Chapmans says 6-7 times the depth, whereas my Danish friend (Very
experienced sailor) says 3 times depth is sufficient, especially since I
have a heavy anchor and all-chain rode.

In the following hypothetical situation, what scope would the group
recommend:

38 foot sailboat
35 lbs anchor (Plow type)
all-chain galvanized steel rode (300')
mud bottom
sheltered anchorage - calm day - lots of other boats at anchor
High tide mark at 20 feet above bottom.

Appreciate any feedback!

On Wed, 19 Apr 2006 12:35:06 -0700, "cvj"
wrote:

I am getting different advice on the recommended scope when anchoring.
Chapmans says 6-7 times the depth, whereas my Danish friend (Very
experienced sailor) says 3 times depth is sufficient, especially since I
have a heavy anchor and all-chain rode.

In the following hypothetical situation, what scope would the group
recommend:

38 foot sailboat
35 lbs anchor (Plow type)
all-chain galvanized steel rode (300')
mud bottom
sheltered anchorage - calm day - lots of other boats at anchor
High tide mark at 20 feet above bottom.

Appreciate any feedback!


One other set of recommendations. After you have lower the anchor and
adrifted back, set the anchor:

1) In reverse, slowly increase your rpm to 1500.

2) Take bearings (transits) to make sure that you are set.

3) Feel the chain forward of the bow roller. Any vibration indicates
that the anchor is not set.

4) After 30 seconds, shut down the engine. The anchor is set.

5) Sleep well.

The advise about the snubber is excellent.

Jack

_________________________________________
Jack Dale
ISPA Yachtmaster Offshore Instructor
CYA Advanced Cruising Instructor
http://www.swiftsuresailing.com
_________________________________________

3:1 is fine for all chain rode for average / light conditions. As
always, more is usually better with wind, etc. Remember to count the
height of your anchor roller above the water in your calculations for
depth. Mine is 8' off the water. Make a real difference! As far as how
to anchor, usually do what everybody else in the anchorage is doing. If
they are Bahamian moored, you probably should to. If everybody is
single, stick with that. Hopefully everybody will swing together, and
if you anchor differently, there may be some "bumps in the night". Of
course, if everybody is stupid and anchoring wrong, get away from them
and do it right! :-)

Your hypothetical question is predicated on a false assumption:
i.e. "sheltered anchorage - calm day"

I think that one really needs to be solving this for the worst case
scenario, not the best case scenario. In calm, protected water anything
will hold you. The real issue is when the winds/waves pick up.

A better approach to this question might be to ask what the appropriate
anchor weight and rode for your boat weight should be, or the
appropriate anchor style to bottom type (this is a religious question)
and which direction the wind/waves are likely to force your vessel.

In some cases, the best solution might be putting out a second anchor,
running the motor to reduce strain on your ground tackle, and being
ready to head to deep water at a moment's notice. Thinking one can
simply lay out a magic amount of scope is perhaps wishful thinking; a
more prudent approach requires understanding the environment and how it
could potentially change, and then preparing for that.

I think the 3 to 1 ratio a bit chancy myself. I'd stick to 6 or 7, 10
if possible. More importantly, I'd put as heavy a primary anchor down
as I could possibly afford, and as beefy a chain as possible. Also,
using highly elastic snubber lines from your bow to the chain will
greatly reduce the shock loading on the ground tackle.

You might also consider setting your GPS or Radar alarm to sound if you
move position or get too close to something else.

Hope this helps.

Robb

cvj wrote:
I am getting different advice on the recommended scope when anchoring.
Chapmans says 6-7 times the depth, whereas my Danish friend (Very
experienced sailor) says 3 times depth is sufficient, especially since I
have a heavy anchor and all-chain rode.

In the following hypothetical situation, what scope would the group
recommend:

38 foot sailboat
35 lbs anchor (Plow type)
all-chain galvanized steel rode (300')
mud bottom
sheltered anchorage - calm day - lots of other boats at anchor
High tide mark at 20 feet above bottom.

Appreciate any feedback!

Not a false assumption, it happens all the time. Heck, if you plan for
the worst case scenario all the time, just stay home and sell the boat.
If you try to put out a 10:1 scope with all chain on a calm day, you're
going to have a pile of chain on the bottom, and that's all. Probably
piled up on top of your hurricane anchor. You can look up what people
have learned over the years / decades for all chain rode and 3:1 is
just fine. 6 or 7 to one or more is used in storms. I didn't say NEVER
use that scope, it's just not necessary most of the time. Since the
original poster was only asking about scope, I limited mine to that
discussion. As a matter of practice, I have two anchors and rodes set
up ready to go on the bow, with 6 more in inventory for all kinds of
conditions, including hurricanes. 95% of the time, I stick with my
primary anchor and 3:1 scope. Advising someone to get the biggest chain
and anchor they can doesn't recognize real world conditions.

"Jack Dale" wrote in message
...
On Wed, 19 Apr 2006 12:35:06 -0700, "cvj"
wrote:

snip

The advise about the snubber is excellent.

Jack
________________________________________
Jack Dale
ISPA Yachtmaster Offshore Instructor
CYA Advanced Cruising Instructor
http://www.swiftsuresailing.com
___________________

I'd be a little concerned that 10 M of snubber line would wrap itself around
the anchor chain making it very difficult to use a windlass for retrieval.
Happened to me. Sometimes fast retrieval is important. I have seen
recommendations for snubbers that suggest only letting out enough line to
reach the water surface. I think this may be a better idea.