Conference unifix::sailing

    Good article Alan (calling it a note seems a dis-service)!
    
    I just wish the clown who came in after I retired last Saturday
    nite, dropped his anchor on top of mine, put out 3:1 scope and left
    a red streak down my port side when he drug past me at 4AM, could
    (were capable of and inclined to) read this.
    
    Walt

     How would you describe the proper technique for setting an anchor???

    This is basically how I do it. I have about a 95% sets-first-time
    success rate.   Oh, I also let the anchor go and weigh from near
    the stern, but only beacuse I keep my anchors and coated chain in 
    a locker in the cockpit and its easier to bring the rhode aft than 
    than anchor forward. I can also steer, etc while doing this.
    
    
    Danforth Type:
    
    layout at least 5X scope on deck
    
    stop over spot where anchor is to be dropped with bow to wind or
    current (whichever is dominate)
    
    ease anchor to bottom (dont drop or toss it in)
    
    allow boat to drift down wind/stream while letting line pay itself
    out.  you got to keep the boat from turning more than 180 degrees
    as it is blown off or you might wrap around the keel/etc.
    
    let the boat steady up at end of line then back down with the engine
    to check the set.
    
    adjust the scope according to conditions.
    
    
    
    the time it takes to drift back, and the the slow increase in tension
    at the end of the drift allows the Danforth to align itself and
    pull in.   tossing the anchor in and backing up in a hurry will
    often cause a Danforth to skip along the bottom instead of digging
    in.

    
    Walt

     Well i tried that technique. The anchor did skip along the bottom
    a couple of times and then set. I had the convience of having some
    diving gear on board so i went over the side to see what the anchor
    actually looked like (my first time diving, an interesting and strange
    sensation). Although the anchor did hold the boat through some fairly
    gusty winds and some rather large wake from motor boats, i was very
    surprised at how little of the anchor was actually in the ground...
    Is this normal,,,or should that anchor be really burried???

    This is my first season suing a 22# Bruce anchor and I am very pleased
    with its performance.  I have read most of the surveys and write-ups
    comparing different anchors and have seen the same thing each time.
    Most coastal cruisers have Danforths, off shore cruisers have CQR's
    and very few people (if any in some surveys) have Bruce anchors.
     The surveys always favor CQR's and show them to be the best.
    
    Being a pesimist, I did some calling around.  The importer for Bruce
    anchors is IMTRA Marine products in Medford, MA. and they will give
    you a number of reference to talk with.  Each person I talked with
    gave glowing reports on the performance and most had used the same
    weight CQR's in the past.  IMTRA also sent me a number of reports
    from England on the effectiveness of the Bruce design.  I was impressed
    and purchased one.  As I said I have had only one season on it,
    but have weather several squalls and a thunderstorm with 7X scope
    without dragging.  Setting it is a breeze.  It sets first-time,
    everytime.  And resets immediately when the wind or current swings
    around.  CQR's have a swivel that is a potential breaking point
    that I'd like to avoid. 
    
    Storage of the Bruce is a problem.  It is one piece and has sharp
    flukes that scratch everything.  SWING-LINE make an excellent bow
    roller (it's more expensive than the anchor!) that fits it well
    and if mount with enough over hang you won't scratch your bow when
    pulling it up.
    
    I have had limited experience with CQR's, but I am converted to
    a Bruce fan.
    
    

re .3: 

We back down at full power for a least a minute to be sure the anchor 
won't drag. It will sometimes hold at part throttle but not at full 
throttle. 

I would be cautious about laying out a long anchor rode on deck -- too 
easy to get it caught on something like your foot. We have one rode in 
an anchor lock and two others in large bags. All three rodes are just 
stuffed in, not coiled. The rodes have always paid out smoothly and 
without problem. You might want to try it. 

re .5:

The two times I have dived to look at my anchor it wasn't deeply buried 
-- this was with a sand bottom shortly after anchoring. My suspicion is 
that long term load on the rode slowly causes the anchor to bury deeper. 
We've never had any trouble breaking out a recently set anchor, but have 
had some difficulty on occasion with an anchor that has been down a day 
or two. 

    I'm a member of the "lower it to the bottom when stopped" school also.
    When backing down (slowly under motor or sail) i will snub the rode
    when I've got out a 3-4 scope and let the line tighten up. If the
    tension increases steadily I figure that the flukes are holding. I'll
    then release the tension and back down to a 6-8 scope. At this point
    the line is snubbed and we back down HARD under power for a minute or
    two. The line will stretch and we watch for any major changes in
    position. If none, we assume we're hooked and go into position
    monitoring mode. If we get a major change we assume we're dragging
    and go back and do it all again.
    
    All my experience is with a Danforth with a chain amd nylon rode.
    One thing that I found very helpful was marking the rode at 10 ft
    intervals. I always knew how much I had out and never had to guess
    about scope. Oh yeah, we also had a depthfinder.
          
    Ed
    

    Re: .3, .6   (the rhode on deck)
    
    I bring the amount I want up on deck because I cleat it off and
    go aft to drop the anchor.  I fake the line out on deck the way
    I was taught in the Navy to do for hawse and havent snagged anything
    yet. 
    
    To draw it VT100 style:
    
                                                           Storage
        -------------------------------------------------     O---
       |                                                 |        |
        -----------------------------------------------   --------X
                                                       |        Cleat
        -----------------------------------------------
       |                                                      Chock
        -------------------------------------------------------(_)-
                                                                   |
                           To stern and anchor <-------------------

    
    The line marked is with those cute yellow markers (a very worthwhile
    thing to do).
    
    Also, I never find it necessary to back down with more than about
    half throttle, but I would say this is more a function of the boat
    than any universal rule-of-thumb. By monitoring the line tension
    (it vibrates when skipping across the bottom) and position relative
    to nearby boats or landmarks I can tell when it sets (the dingy
    trailed astern can help too - when it stops bashing your stern and
    drifts to the end of the painter you are in).
    
    Finally, I take some precautions that I didnt mention before. When
    the anchor feels secure, I take some bearings on fixed objects and
    relative bearings between fixed objects other boats abeam and myself.
    I also have the anchor watch capability on the Loran but you really
    need to enter the position of the anchor itself, which means bringing
    the stern (where the L/C antenna is located) up over the anchor.
    I am not fond of doing that so I dont use it much (not to mention
    the fact that the alarm will go off at 3AM anyway when they take
    one of your slaves off the air for PM).

    
    Incidently, a friend with a Oyster 41 spent 5 days last week (remember
    last week? -rain,etc) dragging a 45lb CQR and 100' chain around
    the grassy bottom of Cuttyhunk. He said it would set right away
    but the wind on the boat pulled it thru the bottom almost constantly.
    
    Walt

I forget where I got this idea, so I don't know if it's common knowledge
or practice.  Instead of purchasing at exhorbitant expense the pre-marked
anchor rode markers, go to a hardware store and buy the shortest roll of
surveyor's tape.  It's the nylon-y bright orange stuff you see tied to trees,
etc.

Cut off 6" or so long strips and use a permanent marker write 10, 20, 30
or 30, 60, 90 or whatever, and thread them through your rode at the appropriate
places.  Mine have been on for 3 seasons and are starting to need re-marking.
One roll will do an entire yacht club.

     Travis

Don't be so extravagent! Go beg some spinnaker cloth scraps from your
sailmaker or go look in the trash bin out back (which is where I got my
scraps). I use single strips of red, white, blue, and yellow to mark
25', 50', 75', 100', double strips to mark 125', etc. This way you don't 
have to read anything unless you're color blind.

    I have tried, successfully, the "Hal-Roth-anchor-down-wind" method,
    using a fisherman anchor. Basically you lower sail to slow you up
    then head down wind till you get to the spot close to where you
    want the anchor to endup. Drop the anchor, let out rode to say ~4-5
    scope, snub to check, then continue down wind. Then snup up fully,
    the boat will head into the wind and you'll know immediatelly if
    the anchor is holding.

    RE: .11
    
    That would probably work well for a quick setting anchor like the
    Herreshoff/fisherman/plow.   Unless you moved real slow though,
    a Danforth type would probably pull out as often as it set. It
    needs time and very gradual increased loads to bury. Because the
    flukes are not at a fixed angle to the shank (or whatever its called)
    the flukes can plane along the surface of the bottom untill they
    snag something.
    
    To give you an idea of what I mean.   We recover our Danforth at
    the stern and tow it from a stern cleat for a while to clean it
    off before stowing.  The anchor planes on the surface just like
    a skier at 4 kts.  My guess is a similar boundry phenominon (sp?)
    might occur at the bottom/water boundry at a lower speed.
    
    Walt

    Put out anchors like so for Charley...

        8 lb dan.           / \                          12 lb dan.
         \/\/                |                            \/\/
           \               NE|                             /
            \                                             /
             \            200 lb                         /
             \/          mushroom                      \ /
                            |
                           \ /

    Would it have been better use of Danforths to have done somethiing
    like this???  I can't recall where I've seen this technique but
    I know I've seen it somewhere before.
    
    
    
     8 lb.              12 lb
    
     \___________________\_________________Boat
     /                   /
 
    This would be done by rowing out and dropping the first anchor. Then
    dropping the second anchor along the way as you rowed back into
    the bow. The first anchor rode would be shackled into the rode of the of
    the first at, let's say, the swivel between the chain and 1/2" nylon on
    the second rode.
    
    Biggest potential problem would be first rode fouling second anchor
    Do you think you'd get a synergistic hold because the second anchor
    is going to keep the rode on the first anchor horizontal??
    
    Comments please!!

Use of two anchors in tandem is recommended, as I recall, by the 
Hiscocks among others. Putting out two anchors, one to each side, is 
only effective as long as the wind blows from the direction bisecting 
the angle between the anchors. As soon as the wind shifts (and not very 
much either) all of the load goes onto one anchor. 

I've never tried the tandem arrangement. A couple of problems come to 
mind. 

Which anchor should be nearest the boat? If the smaller, then it is
likely to be broken out (assuming that conditions are so bad that you
need more holding power than your largest anchor has) and it may or may
not reset since setting implies at least a short dragging distance. If
the second anchor doesn't drag, you then have effectively a weight on
your anchor rode as was described in earlier. This is still a good
situation. If the (large) main anchor is nearest the boat and breaks
out, then the (small) secondary anchor may drag slowly without breaking
out. This would give the main anchor a chance to reset. If the main 
anchor merely drags, the secondary anchor will be effective and increase 
the holding power.

How do you set both anchors? This could be quite difficult and tricky.
If I were to try this, I would use the main anchor closest to the boat,
I would set the secondary anchor first on short scope (2:1 maybe) by
backing down gently. I would then lower the main anchor while backing
down, keeping the rode as tight at possible so that there is little or
no slack between the two anchors. At say 7:1 scope I'd back down as hard
as possible to set the main anchor. Finally I'd use as much scope as
possible (at least 10:1). 

Obviously, the tandem arrangement depends on knowing what the wind 
direction will be fairly accurately, too. 

Another idea (not mine -- I'll steal ideas from anybody): Anchor 
normally with the main anchor and large scope. After you've settled into 
place, lower your secondary anchor to the bottom and leave the same 
length rode as on the main anchor on deck and free to run. Lightly lash 
(with whipping twine maybe) the secondary rode to a cleat. Now if the 
main anchor starts to drag, the secondary anchor will drag too, breaking 
the lashing and paying out the rode. If all goes well, both anchors will 
eventually set with the boat pointing into the wind. (Believing this 
requires an act of faith.) We actually tried this once when anchored on 
the rocky bottom at Matinicus Island. Round 'bout dawn the lashing parted 
with a loud twang. We shortly thereafter recovered both anchors and the 
anchor buoy and surfed off to Tenants Harbor in a near gale (Tenants has 
excellent holding with a mud bottom in 20 to 30 feet). 

    I like the idea of the tandem approach.  Some thoughts on the
    advantages (many already voiced).  Shock loads would be absorbed
    by the first anchor. The scope on the second anchor would be 20
    or 30:1 easily. Tendency to drag would be reduced by being spread
    out over a large area of the bottom. Sensitivity to small wind shifts
    should be much less than with the Vee anchoring approach.
    
    Problem: If the wind shifts a lot (like >90 degrees) you could end
    up with a rats nest on the bottom, with anchors fouling each other.
    
    Incidently, you may have seen an article in a recent sailing mag
    about a sea anchor/drogue that uses lots of small drogues in tandem
    across a couple hundred feet of warp. The idea was to reduce shock
    and surge usually seen when dragging a large drogue in big seas.
    Sort of the same spread-the-load idea on the other end of the boat.
    
    Walt

    but with a little help. The wife and I were anchored in the lee
    of Bassetts Island in the Pocasset Harbor area (along with many
    other water craft!), and were below having lunch. One of the many
    motor boats had crossed my bow and fouled my anchor line with his
    rudder, and was drifting down on me. He shut down his engine (to
    my relief!) and we fended off each other. To free us, I let out
    about 50' more of rode, and drifted down. This allowed the rode
    to move more towards his bow, and I told him to start up and
    move in reverse. This worked to free him, and I pulled in the rest
    of the anchor rode and could tell we were not hooked anymore. I
    started up the engine and pulled in the anchor which was fouled
    with grass and mud. It never could have reset again.  It is only
    a lunch hook, a 13S with 15' of 1/4" chain, and in 12' of water
    I let out about 60' (good enough for lunch, and the calm water).
    This winter I'm going to purchase a 25lb CQR plough, and only use
    the lunch hook when were alone!!
    
    Great weather for sailing this weekend, and hope the fall is the
    same!!!

    
    	I would like someone knowledgeable on the subject to extend
    this note, specifically I would like to know about sea anchors.
    Is there a good article anywhere on their design ?, I know they
    just look like a cone of sail, but there has to be some relationships
    between length and diameters at each end.  Where are the stresses in
    these things and what should I reinforce if I decide to make my own ? 
    Oh yes, all the usual assumptions about boat size (area to the wind)
    and weight, wind forces, etc.

    	Reg
    

    Let me put on my moderator hat here...
    
    This is a good topic and I'm glad to see it come up. In order to
    keep issues clear, I'd suggest that you set this up as a separate
    topic and delete this reply. 
    
    Ed

    
    Since this is the not-quite-dead of Winter, I hope you won't mind
    if I disinter this old but good (and not quite dead) note.  Here's
    some data related to wave sizes that may be interesting:
    
       o  as a first approximation, reducing the depth by 50% reduces
          wave height by about 40%
    
       o  the average wave height of the largest 10% of all waves is
          2x the average wave height, and 2.4x the most common wave
          height.  This allows you to eyeball it & estimate the top
          10% if conditions don't worsen.
    
       o  In general, a 5 knot increase in wind speed increases
          wave height by about 10%.  This allows you to estimate how
          bad it might get if conditions do worsen.
    
    Here's a segment of a table for predicting "significant wave height"
    as a function of wind speed and water depth.  The significant wave
    height is the average height of the largest 1/3 of all waves:
    
                               water depth
    
       kts      6     8     10     15     20     25     30
       30      1.8   2.2    2.5    3.3    4.1    4.8    5.4
       25      1.6   2.0    2.2    3.0    3.7    4.2    4.9
    
    
        o  The effective holding power table in .0 is fit well by the
           equation:
    
    		E = 105.43 * (1 - 1/e(r/2.96))^1.53
    
           where:
    		E is a percent of the optimum holding power
    		e is the exponential function
    		r is the ratio of the rode length to the depth from
    		  the bow roller to the bottom (2 <= r <= 10)
    
        o  There's an interplay between wave height and r, since if
           the boat rides up the wave (assumption), then r is effectively
           reduced.  In small depths the waves are smaller, but so is
           the rode (for the same r), so given the assumption above,
           the effective holding power equation, and the wave height
           function, is it better to anchor in deep or shallow water?
    
           Assume for the sake of the example that r was chosen to be
           5:1, and you could choose any water depth between 7' and
           20'.  The following table determines the effective holding
           power under various conditions:
    
    	   Knots	depth	wave height	r-eff	%
    	   35		7	3.9		3.85	65
    			14	6.4		3.79	64
    			20	7.6		3.87	65
    
    	   30		7	2.0		4.33	70
    			14	3.5		4.25	70
    			20	4.3		4.29	70
    
    	   25		7	1.7		4.42	71
    			14	2.8		4.39	71
    			20	3.7		4.38	71
    
    
        Some patterns can be identified from this data:  the penalty
        from increased wave height and the benefit of increased rode
        length cancel each other.  Riding it out with smaller wave
        heights would be more comfortable with no affect on effective
        holding power (at the same r).  It's actually marginally worse
        at intermediate depths rather than deep or shallow, although
        the effect is really negligible.  The effective holding power
        is not linear with increased wind speed; it degrades more
        rapidly as wind speed increases.
    
    o  These values also assume that the rode is taught.  If a weight
       is placed somewhere along it as suggested in .0 and it is not
       already raised, then the effective holding power would be greater.
       Unfortunately, the waves generally come with the wind, so the
       worst waves will probably come when the rode is extended.
    
    - Jim
    

    Re. 16  In the wave height table, what assumptions are made about
    "reach"? With an offshore reach the shallows would have even smaller
    wave than dictated by the water depth and further offshore the
    increased reach would drive the wave heights up. And vise-versa?
    
    Jerry
    

One additional complication: Yes, the waves will be smaller in shallower
water -- if the waves are produced by the wind blowing across the
shallow water. But, and this is more often the case than not, the waves
in a shallow anchorage are waves that are coming in from deeper water.
When a deep water waves comes into shallow water, it becomes higher and
the wavelength becomes less (ie, the wave becomes steeper). This is why 
waves break against the shore. This would imply that anchoring in 
shallower water is may be preferable only if deep water waves cannot 
reach that shallower water. Also, remember that waves refract (bend) 
going around headlands and islands. Waves going around a small island 
will refract so that they collide behind the island, resulting in very 
rough water. Basically, my strategy is to anchor where there is the best 
possible protection from any waves, regardless of how deep the water is.

Alan

    My last should be     Re. 19     not Re. 16   Sorry
    Jerry
    

    
    re: 20 & 21
    
    that's correct, the table doesn't factor in the effects of "reach",
    which as I understand it is the distance over which the wind has
    blown without obstructions (e.g. over sea), also called "fetch".
    Therefore the effects of deep water waves is not considered, and
    I'd follow Alan's advice and anchor wherever the protection from
    waves is greatest.
    
       - Jim
    

	The effect of current also does not seem to be included in the table.
   Anyone who's seen the south end of the cape cod canal when the current is
   hard southwest and the wind is howling out of the southwest in the late
   afternoon at 15-25 can attest that current makes for higher, steeper waves.
   This is also true in offshore currents such as the gulf stream. 

   Btw, what is the source of the info in the previous notes?

   (also, i'll never understand why a southwest current flows TOWARDS the
   southwest, while a southwest wind blows FROM the southwest...)

    
    The information about waves comes from:
    
        Weather For Outdoorsmen, A Complete Guide to Understanding
        and Predicting Weather in Mountains and Valleys, on the
        Water, and in the Woods.
    
    by Walter F. Dabberdt
    
    This book was recommended to me by a meteorologist friend of
    mine, and has a great deal of interesting factual information
    about both water and land.  I'd recommend it too.
    
    There is an error in the table heading: it should be in mph, not
    knots.
    
       - Jim
    

re .24:

>>>   (also, i'll never understand why a southwest current flows TOWARDS the
>>>   southwest, while a southwest wind blows FROM the southwest...)

The Coast Guard has several new 270' cutters which have a very 
sophisticated computer system. The Search and Rescue software didn't 
work very well -- until it was discovered that whoever had done the 
programming thought wind direction was the direction toward which the 
wind was blowing. 

By the way, in one test the 76mm cannon scored 110 hits in 110 shots at 
10000 yards and the cutters have a speed of some 19 knots. But don't 
think you can outrun them -- they also carry helicopters.

We have been using a 35 lb CQR with 40 feet of 5/16 inch chain and a 
1/2 inch 3-strand nylon rode for many years with no problems -- except 
once. That time we dragged in a squall while anchored in very soft mud 
(where CQR anchors are least successful). After that experience we 
bought a Fortress FX-37 (very much like a Danforth only aluminum).

Last week I was anchored in a Maine cove with a soft mud bottom, and, as 
the NOAA forecast was predicting strong winds that night, I decided to 
use the Fortress for the first time. I unshackled the CQR, shackled 
the Fortress to the end of our 40' of chain, and tried to anchor. 
Fortress does, by the way, recommend only 6' of chain, but more can't 
hurt, right? And besides, I didn't have a 6' length. With 5:1 scope and 
full reverse throttle I was dragging the anchor merrily through the mud
and toward shore at nice rate. Not good, I thought. 

I retrieved everything and removed all the chain, shackling the nylon 
rode directly to the Fortress. This time the Fortress dug in quickly and 
held at full reverse throttle and later in 20 to 30 knot winds. 
Interesting. My assumption is that the weight of 40' of chain kept the 
stock of the Fortress nearly parallel to the bottom, which in turn did 
not force the flukes into the bottom. With just a nylon rode, the stock 
lifted enough to force the flukes into the bottom. Fortress claims that 
the holding power of a FX-37 in soft mud is around 1200 pounds. Well, I 
did need my windlass to break it free the next morning. 

My experience here agrees with that of some liveaboard friends who spend 
several months at anchor every year. They've found that no chain works 
best when using a Danforth-type anchor. 

Alan

    I don't understand why no chain works best with Danforth style anchors.
    Supposedly more scope is better (read stock 'more' parallel with the
    bottom is better), chain being heavier than nylon would tend to hold
    the stock down parallel with the bottom therefore its 'better'.  I
    know, can't argue with experience, and your experience tends to prove
    that the no chain approach is better.  But it doesn't make sense to me.
    The flukes would tend to be lifted up with just nylon which is
    apparently just what is needed?  The flukes lifted clear so they can't
    dig in?  No.  Obviously just lifted enough so they can dig into the 
    bottom, but they would dig into the bottom anyway, with chain wouldn't
    they?  Well, your experience says thats not the case. 
    I don't get it.
    
    Jeff

    Anybody have a Navy Anchor?  I have a 10 pounder which is about 40
    years old.  It works well!  The style is the same as would be found
    on a large ship, just smaller, alot smaller.  Does anybody know if they
    are still available, and if so where?   I have never seen the Navy
    Anchor drag, but my danforths have dragged. I do have chain on the
    danforths as well as the navy anchor, but as the prior noter says the
    chain doesn't seem to help with Danforth anchors... maybe the chain is
    more suitable for navy anchors?  

re .28:

My guess as to what is happening is this:

The flukes on Danforth and Fortress anchors pivot a limited extent 
around the stock. Imagine one of these anchors lying flat on a smooth
surface with a rode attached. Now pull on the rode parallel to the 
surface. The anchor will simply slide along the surface with very little 
resistance. 

Now imagine that the surface is slightly bumpy. When the flukes hit a 
bump, they will either try to dig in, simply go through the bump (soft 
mud in the situation I experienced) or ride over the bump (since the
flukes are hinged about the stock). They might just sort of flutter
slowly like a luffing sail. 

With the chain removed and just a nylon rode at 3:1 scope (about what I
used to set the anchor) or more, the stock is lifted off the bottom and
the flukes hang down with the ends on the bottom. The weight of the
anchor on the thin, fairly sharp and pointed ends of the flukes will
push them into the bottom, allowing the anchor to dig in. 

Once I got my anchor set, I increased the scope to around 6:1 with a 
12 pound rider about 25' from the boat.

It is interesting to note that the length of chain recommended by 
Fortress and Danforth is short (6' or less as I recall) and the weight 
of this chain is much less than the weight of the anchor. My 40' of chain 
weighs about twice as much as my Fortress FX-37. 


re .29:

Navy anchors are similar to Danforth anchors, I think, but their flukes 
are relatively much thicker (and also therefore stronger). This means
that they are much more dependent on their weight for digging in than is
a Danforth. As a result, in small sizes they are less effective than a 
Danforth or Fortress. The weight of the sizes used on large ships is 
enough to get them to set.

All in all, it seems that anchoring isn't so simple, and some 
experimentation (trial and error) is helpful, as is some good fortune.

Alan

re .28 again:

As long as the scope is greater than 1:1, you cannot lift the anchor off 
the bottom. All that pulling on the rode will do is lift the stock until 
it hits the limit of the pivot motion, and then the anchor is resting on 
the bottom on the pointed ends of the flukes. Further pulling on the 
rode will simply slide the anchor along the bottom until it sets 
(assuming it ever does). 

    The doo-hickey that activates a Danforth is the wedge shaped cam that's
    welded between the flukes at their base.  This is the point at which
    the stock is attached to the round shaft.  The cam is shaped so that, as
    it lies flat, the flukes are forced down.
    
    My guess is that, with a heavy chain and long scope, the chain plows a
    furrow into which the cam drops.  With nothing to activate the cam,
    there's nothing to force the flukes down.  As a result, they'll just
    scitter along the bottom.  On a hard bottom, I would expect a Danforth
    to work about the same with or without a heavy chain.
    
    I did try setting a Danforth in the soft sand shoals on the North side
    of Martha's Vineyard when the wind died and the tide turned foul. 
    There was no chain on the rode for reasons I don't remember.  But it
    didn't want to set.  This was a 12 lb. standard Danforth.  Probably not
    enough surface area.  
    
    The Fortress anchors have a "mud" mode wherein the flukes hang down at
    something like a 45 deg. angle.  Was this feature enabled during your
    successful set?
                   

re .32:

No, I used the standard setting. One reason I bought the FX-37 is to 
have sufficient holding in soft bottoms without having to use the mud 
setting (which requires using a wrench to loosen/tighten two bolts). 
Fortress explicitly warns against using the mud setting (increased angle 
between the flukes and the stock) in hard bottoms. Doing so is likely to 
bend the anchor. 

One disadvantage of light anchors is their minimal ability to penetrate 
hard bottoms. Maybe even soft sand is too hard for only a 12 pound 
anchor. (Gee, I'd like to anchor in sand someday. I do get tired of 
washing mud off my ground tackle and deck, even with a deck wash pump.)

    .30  Whether the stock on a Danforth is held slightly off the bottom
    or not shouldn't matter because the flukes will attempt to lie flat
    on the bottom with the angle plate thing tending to make the flukes
    dig in.  UNLESS the stock is raised enough so that it 'hinges out'
    against the flukes and forces them up off the bottom I would think
    the angle of the stock would have little effect on the anchor setting.
    
    I too have noticed that Danforths seem to set better if allowed to take
    their time and are gently set with GRADUALLY increasing power.  Fast
    pulls hard pulls skitter them across the bottom. 
    
    My Navy anchor (lunch hook) has never dragged on me in reasonably hard
    currents (3 knots) and winds 15 20 knots.  This is with a 17 foot boat
    which grosses about 1000 lbs.  It seems to set MUCH more quickly than
    my 9 lb Danforth under similiar conditions.  The Navy anchor also has
    a hook up on the crown for a 2nd line so one can drag it clear of snags
    without losing the anchor.  The Danforth can't be cleared with a 2nd
    line.
    
    I have never used a CQR.  Hal Roth uses them alot and he got wrecked
    on an island off Cape Horn when his CQR failed to set in heavy kelp.
    But then he hardly sails in typical conditions either.  
    
    NO anchor works best under all conditions, just like a boat one has to
    pick the best compromise.
    
    
    Jeff

Alan,
	Re .30

	Could you describe this device. Did you build or buy it?

	Mike

re .35:

Well, sure. My anchor rode rider is simply a 12 lb mushroom anchor tied 
to my anchor rode with a short length of 1/4" line (I used to use an 
eight pound mushroom). 

A fancier way to do it is use a shackle through the eye of the anchor 
and around the rode. Tie a long length of 1/4" line to eye of the 
anchor. The mushroom anchor will now slide along the rode and its 
position can be adjusted with the 1/4" line. 

On a very calm night you can let the mushroom sit on the bottom with 
very little scope and your boat will lie to the mushrom rather than the 
main anchor. See also note 69 more information.

Alan

re:   .31  Short rodes and all

>>>As long as the scope is greater than 1:1, you cannot lift the anchor off 
>>>the bottom. All that pulling on the rode will do is lift the stock until 


Alan, careful with this. If by "scope greater 1:1" you mean a rode set for 
just over the water's depth, its quite possible to "fly" your anchor on a 
short rode as you try to set it in reverse. The water drag at just a couple of 
knots is plenty powerful enough to set an inverted catenary in a light rode 
at maybe 40 degrees off the vertical (as it leaves the boat), thus "using up" 
the little slack you have. That could mean the hook never even touches the 
bottom with sternway on. 

I know you only meant this exageration as an example but diving in the clear 
waters of the Med you see too many anchors resting on the crown, stock vertical. 

Maybe part of the mechanics behind putting the power on slow relates to 
shorter/lighter rodes too.

I personally prefer plenty of chain and a good scope, so the pull is more
parallel to the sea-bed. I have CQR (and what I think is Navy anchor, called 
a Stockless anchor) They both set the same, full power in reverse and use 
the boat's momentum to set the anchor. When it fetches up sharp the pick is 
definitely *IN* solid.  If it skips I try again.


 

re .37:

You are quite right. Good points. I was assuming no current and no 
boat speed.

The problem with Danforths (and similar anchors such as the Fortress) 
"flying" and the frequent difficulty in getting them to set is why we 
use a 35 lb CQR with 40' of chain almost exclusively. It sets firmly 
almost immediately and I am reasonably confident it will reset within a 
few feet if broken out by a shift of wind or tide. I don't have the same 
confidence in a Danforth.

Alan

    What does the small boat owner do (17 footer) when needing to reliably
    anchor?  I ask this because putting a 45 lb CQR on my boat is sort of
    obserd.  It seems that the small boat is pretty much limited to the
    Danforth (or equivalents) or the Navy Anchor.  Are there small CQR's
    available?  I havn't seen any in catalogs.  
    
    It may be that the CQR's work better than Danforth types is because
    the CQR is by definition a relatively heavy anchor.  How would a 45 lb
    Danforth compare to a 45 Lb CQR for example?
    
    During the Summer I moor my boat on the ocean.  The area is sheltered
    but not completely so.  Many use a mooring stone.  I havn't been
    comfortable with deadweight 'anchors'.  I wonder how heavy a mushroom
    I would need to be reasonably secure.  I suspect 75 to 100 lbs.  Whats
    the bottom?  Maine mud and sand with occasional stones.
    
    Does anybody know where I can buy a Navy anchor,  10 to 20 lb range.
    
    Jeff

re .39  Here's my $0.02

	There's 2 things here. Something you carry around on your 
	boat to temporarily anchor, say over night and something you 
	moor-up to when you leave the boat un-attended for a long time
	(let's call that a mooring). They are usually 2 completely 
	different things.

	Most people choose a sinker/mushroom etc as a mooring because it
	essentially non-direction, low loading and low tech so it doesn't 
	break-out, break-up, foul  etc. That's very important since you 
	are not around to "fix" whatever the problem is. They are also cheap.

	Mushrooms/sinkers work well in soft bottoms where they sink in. 
	Then the weight of the mud over the sinker and the suction 
	created (if you try to pull it out) greatly increases the 
	load-carrying ability. ie you are no longer sitting to a 100 lbs 
	dead-weight. Maybe you had some bad experience. Care to tell?

	An anchor *HAS* to be portable so its relatively light, higher tech, 
	higher loading etc which gives rise to all the short-comings (like 
	not re-setting, fouling, bottom-type preference). For a long-term 
	mooring I'd take your 100 lbs mushroom over the 40 lbs anchor anyday.  

	Yep, carrying a 40 lb hook on a 17 foot boat would be absurd (and a 
	big liability)
 
	I remember the "one pound per foot" rule, but I get the impression 
	that this is used for boats > 28 foot. Most smaller boats tend to 
	use less than a pound per foot, mostly I guess they don't expect 
	to be anchored 40 miles from a safe haven in bad weather.
 
       	You can get smaller CQRs. I have a 15 lbs and a 10 lbs (and some 
	other types). Mine hooks over the pullpit rail.

	My boat is small too. I find chain stows easier than bigger anchors 
	and its possible to put the bulk of chain low down mid-ships. 
	Steve
 

    re: .39,  another $.02 (you're up to $.04 now....)
    
    .40's comments on the mushroom strategy are sensible, and consistent
    with my family's experience over 40 years of riding out even hurricanes
    with 12-16' skiffs and sailboats on 50-100lb mushrooms *set in mud*. 
    The secret to to a good mooring --and anchoring, for that matter -- 
    is to match the bottom with the right design.
    
    For a mooring, it's simple, since you meet one set of conditions and 
    just leave it.  Best advice definitely is to ask the locals what they
    do, and pick your favorite or the cheapest of the options in use there. 
    Doing it another way (such as using a mushroom where everyone else uses
    a big block) probably invites trouble.  If in doubt, just match
    whatever the best-maintained similar-type boat to yours in the harbor 
    which has a length around 25% longer than yours.  You'll be as sure as 
    safe asmakes sense then. 
    
    Anchoring is trickier because conditions vary, but here's another
    opinion to add to your pile:
    
    1) (assuming 16' outboard skiff)  12-lb Danforth Standard.  This will
    cover >80% of your anchoring needs, is big enough for some confidence
    but small enough to handle and stow easily.  I'd add 6' of 1/4" chain
    mostly for chafe protection where the rode meets the bottom most often.
    
    2) 15-lb Yachtsman type, a.k.a. Herreshoff type or stock anchor.  While
    these names mean slightly different things to different people, and I
    personally favor the Herreshoff sub-species, their working principle is
    the same.  They have curving pointy ends at one end of a shank set at
    right angles to a stock at the other end, where the rod atttaches.  For
    ease in stowing, the stock usually has a key near the middle which can
    be removed so the stock slides and turns to lies parallel to the shank
    when not in use.
    
    These anchors are great for weeds, and as good as you're likely to get
    if forced to anchor on rocks.  *Before setting this anchor*, the wise
    sailor who prefers not to buy a new one at regular intervals will tie a
    light line (1/8-3/16" polypropylene is best) to the head of the anchor
    where it meets the shank, and a small buoy or float to the other end.  
    By their design, these anchors will easily drag until solid resistance 
    is met, and will easily snag all kinds of things from cables to logs to 
    rock outcroppings.  The polypro tripline floats up from the anchor 
    (figure your depth and coil the extra line close to the buoy end), and
    will make retrieval simple and reliable.
    
    Together, these two anchors will suffice for your small boat.  Bigger 
    boats require more strategizing and coordination with handling
    technique preferences and boat type.
    
    J.                    

    careless edits left one sentence unclear:
    
    If you use the same mooring system as a similar-type boat to yours, but
    one which is 25% bigger, you'll do just fine.  The locals don't survive
    storms or spend more money than they have to without having worked out
    the best ways over time.
    
    J.
    

    No bad experiences with mushrooms/sinkers personally Steve.  The
    'book' recommends a 175 lb mushroom for an ocean open coast mooring for
    a 17 ft powerboat.  When I was a kid I had no problem holding my
    17 foot skiff/outboard with a 25 lb mushroom on semi-open ocean
    coast. 
    
    I have noticed that without fail I have always been able to break
    loose a 13 lb Danforth on 'average' bottom conditions with a 6 hp
    outboard (auxilliary power) on a 22 foot sailboat with 7 to 1
    scope.  I always figured that if a 6 hp outboard could break loose
    the anchor what would a small storm do?  Set the anchor with power,
    hell, its more like pull it out.  
    
    Jeff 

This reply concerns recent discussion about Danforth anchors and the problem
that they do not dig in under some conditions. The following relates my 
experience but you must of course adapt it to your own size of boat etc.

In Maine, the wind often becomes light in the early evening. I approach the
place I want to anchor under sail in a downwind direction. As I pass over it
I drop the anchor over the side from the cockpit. In say 20 feet of water,
I have an extra 50 feet of rode flaked out on the bow. The rode streams overboard
and when it is fully out, I push the tiller over sharply so the boat will
turn, then I go forward and drop the sails.

When the anchor is dropped into the water and then dragged, the shaft is fairly 
horizontal and the flukes are folded down - ready to bite. The anchor seems 
to dig in deep and the next day is often hard to pull out of the mud.

The anchor is a 15lb Danforth and the boat is 4000lb.

Mike

    .44  What are the most severe conditions you have had your Danforth 15
    hold WITHOUT DRAGGING in?  And, what was the bottom.
    
    Jeff

    An earlier note said CQR's are available in small sizes.... say 10 to
    15 lbs.  WHERE can you find them for sale?  I have looked through
    3 or 4 marine catalogs and find nothing (in CQR's) lighter than 
    30 lbs.
    
    Tx.  Jeff

    My 1991 Defender catalog lists CQRs ranging from 15# (for boats 20 to 30
    feet) 20# (for 30 to 40 feet), up to 75# (for 60 to 85 feet).
    
    My new West catalog starts at 25#.  Last year's Boats/r US starts at
    20#.
    
    djc

    Do you have an address or phone number for Defender?  I have no idea
    where they are located to look up a phone number.
    
    Tx.  Jeff

    The order # for Defender is 1-800-628-8225.  NY residents are told to
    call 914-632-3001.
    
    For information and all inquiries the number is also 914-632-3001.
    
    Before committing to purchase from Defender, peruse the notes in here
    dealing with mail order companies.  If memory serves me correctly,
    either some noters, or some magazines have reported some instances
    where customers were not 100% satisfied.  I have purchased from
    Defender once or twice and have had no problems.
    
    Cheers,
    
    djc 

A certain amount of caution is advised in doing business with Defender. 
Boat/US will match any lower advertised price. They weren't too happy 
when I showed them Defender's price for the Fortress FX-37 (maybe $30 to 
$50 less), but they sold me one at Defender's price. 

>>    .44  What are the most severe conditions you have had your Danforth 15
>>    hold WITHOUT DRAGGING in?  And, what was the bottom.
    
>>  Jeff

	(Sorry for the delay, just returned from vacation)

	It never dragged, but then I was always in places with a
	short fetch and therefore hardly any waves. My guess was the
	worst conditions was say 25 knots but I had no means of measuring this.
	The bottom was always black mud which seems to hold very well
	but stinks!

	Mike

    This summer I have been using a 10 lb Navy Anchor.  Just like a a large
    ships anchor, but mini.  I have compared it to an 8 lb Danforth which
    I used last summer.  I do notice one big difference, the Navy Anchor
    sets virtually instantly, really, it does... with the slightest load
    its into the bottom just like that.  The Danforth required careful
    setting and a gruadually increased load to set it.  This is under
    'average' bottom conditions..... sand, mud, small stones. Don't know
    why the Navy's don't seem to be available in small sizes anymore,
    it works great.  Probably too expensive for its' size.
    
    Jeff

I just finished reading the latest comments about anchoring and 
want to share some of my experiences. I have found myself in 
situations where my old Danforth (an odd ball that had a sliding 
ring in the stock that  weighed about 16#) would either not set or 
if set, would slip under strains of wind and current conditions. 
Note, my boat is a 30' Hunter, 1979 vintage.
Those of you who don't spend many nights on anchor probably don't 
know what its like to constantly check to see if your slipping. 


Because I always anchor when I'm out for a week end or a week, I 
want to sleep without worrying about banging into someone or 
worse. The things that allow me to sleep peacefully are large anchors.  
I carry a Bruce 44# on my bow roller, a 22# Danforth in the anchor 
locker and each have 20 feet of 3/8 chain plus 150' of 5/8 three 
strand nylon. In addition, I also have a Bruce 33# stored in a 
compartment for emergency use but the primary anchor is the 44#. 
If I had room, I would carry all chain for each anchor and I 
would have a windless. Incidentally, I often set 2 anchors when 
either the wind/current conditions are strong or if the anchoring 
area is limited. When I set an anchor, it is by powering my 20 HP
Kubota diesel in reverse at full throttle. If I can 
move the boat, the anchor is not set.

The message is:

If you intend to do overnight anchoring and you want to have 
confidence that your anchor will hold, use over sized anchors! 
Many of you will argue that "your 12# Danforth has never failed" 
in your 28-32' whatever. But--- if you anchor often enough, you 
may have  very unpleasant surprises. 

Joe

re .53:

I am also a firm believer in big anchors and sleeping well. However, 
I disagree somewhat with your choice of rode.

An anchor rode should stretch under load. A large rode (eg, 5/8") may 
not be sufficiently elastic for a light boat (eg, a Hunter 30). The 
elasticity of the rode reduces shock loads on both the anchor and the 
deck fittings. This is why three-strand nylon is preferable to nylon 
braid for anchor rodes. The advantage of a large(r) diameter rode is 
that it will take longer to chafe through. The usual recommendation 
is that the working load on a nylon rope should not exceed 20% of its 
breaking strength, which for a 1/2" rope is about 1660 pounds. It would 
take quite a breeze or a moderate sea to generate that much load. 
Using the wind load formula from Practical Sailor, a 110 knot wind 
would be needed to create a 1660 pound anchor rode load for my 32' boat.
We've been using 1/2" nylon rodes for years (in Maine mud) with no
problem or chafe. 

If you frequently use an all-chain rode and have only a manual windlass,
you'll soon develop strong arms and much patience. Cranking in chain is 
slow. I'd probably grit my teeth firmly and buy an electric windlass. 

Alan

It  is  my  understanding  that  anchor  rode  needs  to  provide  two

functions:



     1.  hold the boat fast to, a fixed point, anchor or mooring.



     2.  be sufficiently elastic as to soften the  shock  of  drifting

         boats, wind and and wave.





It is my understanding that with a  sag  in  a  line  it  can  survive

tension  in excess of its rated strength.  Pull a line out straight as

an arrow and you are in deep do-do with the next shock load.



Therefore it is my belief that you can trade off between:



     1.  a heavier line (or chain) , which will create a greater  sag,

         and lifting the sag will provide a shock reducing effect and



     2.  a lighter line that is more elastic.





You can also place a weight on the anchor rode to increase the sag  as

in option 1 above.



Therefore it would be my choice if I felt comfortable with  5/8"  line

or  greater  for my Drascombe long boat (800 lbs).  I would use it for

piece of mind and hand a sash weight along the  rode.   I  would  also

play out a lot of line to provide a gentle curve for shock absorption.



'course I might have a weight of rode equal to the weight of the  boat

with 5/8 line %)



/doug

    Good advice in .53 Joe.  I have spent many nights wondering if the
    anchor would hold.... until I started going with oversize anchors
    too.
    
    Jeff

    Rule of thumb I use for chain are 3 times max depth at high water in
    slight to moderate conditions anything greater than moderate 5times
    plus. on a 33.5ft Moody I use a 35lb CQR as my main anchor, 200ft of
    chain carried plus an extra 150ft of octoplait line. All nylon road
    100ft for my kedge achor which is a 25lb Danforth. Seems to work but
    all sea areas , bottoms etc are different.
    
    
    Pete

    For another anecdote... for @ten years I sailed my 22' boat all over
    the east coast (Penobscott to Elizabeth to Naragnsett) with a 12 lb
    "Viking" anchor... it was a fluke type but the flukes were horned out
    like a viking's helmet.  It too had a slip ring.  I never have seen
    another one of these.  In all that time, I have never dragged after
    carefully setting the anchor.  In problem areas, current, long fetch,
    tough holding ground (read Boston harbor) I would put down a 10 lb
    mushroom sentinal on a clip to the anchor rode @2/3 of the way down and 
    re drive the anchor.  My only problem during the original tall ships
    was that I was holding while the daysail fleet were bearing down on me.
    
    I'm so convinced about the sentinal that I have been known to bring it
    along when crewing (do a lot of that now). I bring my own essentials
    for sailing. (rigging knife, first aid kit, sentinal, and clove of
    garlic.)
    
    Bob

re .55:

>> It  is  my  understanding  that  anchor  rode  needs  to  provide  two
>> functions:
>>
>>   1.  hold the boat fast to, a fixed point, anchor or mooring.
>>
>>   2.  be sufficiently elastic as to soften the  shock  of  drifting
>>       boats, wind and and wave.

I agree so far.

>> It is my understanding that with a  sag  in  a  line  it  can  survive
>> tension  in excess of its rated strength.  

Uh, here I would disagree. The tension in a rope is simply the load 
applied to the rope, which has to be along its length. Once the applied 
load exceeds the strength of the rope, the rope will break. 

Nylon rope is quite light for its length (100' of 1/2" rope weighs about
8 pounds in air) and it isn't very dense (it almost floats). In my
experience it doesn't take much load on a nylon anchor rode to pull it
straight (at least that which is visible from the deck). Maybe 10 knots
of wind will do it for my 32', 12000 lb boat. Once a nylon rode is
straight, it must stretch (and does) with additional load, shock or
otherwise. 

Chain is much heavier for its length (my 5/16' chain weighs about 100
pounds per 100' in air) and much denser (so you'd need well over 12.5'
of 1/2" nylon rope to have the same effective weight in water as 1 foot
of 5/16" chain). It takes considerable load to pull an all-chain rode
straight, which compensates for shock load, but only until the rode is
straight. After that, the loads on the rode, deck fittings and anchor
are horrendous. Which is why all of the anchoring texts I've read
recommend a nylon shock absorber (maybe 50' of 1/2" or so of
three-strand rope) connecting the chain to the deck fittings. 

The big advantage of chain is its resistance to chafe and that in light 
winds and/or little current your swing about the anchor is much less. 

>> You can also place a weight on the anchor rode to increase the sag .....

Yes, but a big weight is needed. Not much wind and the 12 lb mushroom 
anchor I use for this purpose doesn't create any visible sag. The main 
reason I use the weight to keep the nylon rode from fouling on the keel 
and propeller.

Alan

I have been doing annual to semi-annual multi-week trips to the St. Martin,
St. Lucia, and Grenada and definitely like to get good night sleeps.  Most of
the boats have an oversized CQR as the main anchor and a Bruce for the secondary
or other half a twin scheme.

I have never gotten "real good" and getting the CQR to hold where I have not had
the same problem with the Bruce (in the same bottom condition: medium to firm
sand).  The technique we have used it to lay the anchor on the bottom and making
"sure" the chain and rode playout without rapping with the anchor. Once the 
scope is 5:1 or better, letting the boat "hang" on the anchor for a few minutes
to let the anchor naturally work into the bottom, and then power back on the 
engine for several minutes while checking for dragging. And its holding...

Later, we noticed we have moved and then we dove on the anchor (CQR) and
found that it is laying on its side without the plow down.  (Sure help the 
sleep that night).

On the same bottom, I used the same technique to set the Bruce, and if it sets
under power, it stays put.

I forget the chain length: 15-25' and 5/8 rode.

Any good techniques to make it stink?

>> Any good techniques to make it stink?

This requires the proper grade of Naragansett Mud. The trick is to pull as much
as possible up with your anchor, and liberally spread it across the foredeck :-)

--RS

Re: .54 & .59

I have no qualms about the holding strength of 1/2" nylon rodes 
for boats such as my 10,000 lb+,  30' Hunter.
I use 5/8" 3 strand because I once had a mooring line chafe almost 
through during a storm. The thing that saved the boat was the 
strength of one remaining strand in the 3/4" mooring line. 
The purpose of the 20' 3/8" chain is to form a heavy catenary to 
absorb shock. This size chain weighs in at 164#/100' which 
equates to 32# in my case. I'm not going to go through the 
numbers but it will take considerable force to "straighten" the 
catenary of 20' of chain and enormous force to straighten a catenary 
if the entire rode was chain. Note, those forces relate to wind speed 
and I prefer not being on my boat in a hurricane. The chain also  
provides help to keep the forces on the anchor parallel with the 
bottom.

I was also concerned about the boat's deck strength and that led me 
to made modifications  some years ago. For example, I replaced 
the fiberglas "plate" that was mounted under the cleat and chocks 
with a custom designed and fabricated plate made from 1/8" 
stainless steel. I also added a large bow roller for the anchor/rode 
with additional under deck support. 


Joe

    re: .59, 
    
    "...need well over 12.5' of 1/2" nylon rope to have the same
    effective weight in water as one foot of 5/16" chain."
    
    Given that the weight-per-foot comparison is based on atmospheric
    density, doesn't putting them in water change the the basis to water 
    density?  An inelastic 20 lbs-per-foot rode (weight out of water) of 
    roughly the same density as water would not outperform the 5/16" chain 
    mentioned.
    
    As Alan was pointing out, and adding another alternative, you need one of 
    three things to last at anchor:
    	1)  A catenary with lifting resistance scaled to possible loads,
    	2)  An elastic rode scaled to absorb, not over-resist, linear shock 
    	    loads,
    	3)  Stem/cleat/bollard fittings and mega-load rode all engineered
    	    to withstand very brief but virtually infinite stresses. 
    And I wouldn't trust #3.  
    
    ;-),  J.
                                                                    

re .63:

I think we're thinking along the same lines. A rode with a specific 
gravity equal to that of the water in which it is immersed will neither
sink nor float, it will just sort of be there (how's that for a precise
technical description?). Virtually no force will be required to pull such
a rode straight.  A rode made from a material with a high specific
gravity (high density) will sink and require much force to lift off the
bottom (which is why windlasses are so popular with chain rodes) and
pull straight. Clearly, many, many feet of nylon rode will be needed to
have the same immersed weight (?) or negative bouyancy (?) as a foot of
chain. 

Now, anyone for complicating matters? At least one author (Griffith) has 
suggested connecting the anchor rode (chain or rope) to a large float
(eg, one of those big roundish orange fenders) and thence to the boat.
The idea is that the float will make a great shock load absorber since
it must be pulled well under water before the chain/rope rode can be
pulled straight. I once tried to work out the mathematics of this but
gave up due to the messiness of the vectors involved. 

Someone (Griffith again maybe) also suggests using a combination chain
and rope rode in rocky/coral bottoms. Chafe is simply avoided by using a
small float at the chain/rope junction. The float has sufficient
bouyancy to lift the chain/rope junction some feet off the bottom.
Someone (Griffith for sure this time) also recommends using a
polypropylene (floating) rope rode with the chain so that the rope will
not sink to the bottom in calm conditions. Not exactly a great idea in a
crowded anchorage, but Griffith was cruising in out of the way places
like Patagonia and Antarctica. Anyone ever tried these ideas? I rather 
like the float idea. One of those roundish orange fenders with a 
diameter of about 24" has 300 pounds of bouyancy. 

    I carry 150' of chain and a half inch nylon rode.  The downside is
    pulling all of that chain in ...... but that is not too much of a price
    to pay, I believe.
    
    Three or four weeks ago there were 6 boats cruising together and we
    stopped at lunchtime one day for a birthday party.  All 6 boats rafted
    together with  boats number 1 and 6 (me being 6) having their anchors
    out.  There was little or no wind to start but by the time the cake was
    being passed around, we have a stiff breeze coming in the bay.  Boat
    number 1's Danforth (probably 20 lbs) dragged as the boats came
    bow-to-wind and so we held on just mine.
    
    We had: 
    	Bayfield 32
    	#$%#@@$  27 (norwegian motor sailer)
    	Victorie 34
    	C & C 27
    	C & C 30
    	Rival 32 (me)
    
    Once I had the chain up, the anchor broke out of the gravally bottom
    quite nicely and off we went.
    
    I look at it as a welcome opportunity to exercise those muscles that
    otherwise dont see too much work on a boat.

    Heard on the VHF in Annapolis from a charterer to the place where they
    chartered the boat;  "we are returning because there are not enough
    anchors on board".  The company replyed, "there are three anchors
    aboard".  "Yes, but we have already used those".
    
    

re 1045.62:

Just because something is published in Cruising World doesn't 
necessarily make it true (said with a small grin). 

There are some mistakes and wrong conclusions in an article about
anchoring in the July 1993 issue of Cruising World ("Let the Force Be
With You" by Rodney Glover, pp 26 & 28).

It would be helpful if you have the article to refer to.

A catenary curve is the curve formed by a ideal string hanging 
vertically under its own weight. An ideal string is one in which only 
tensile forces tangent to the string are possible (no bending, shearing,
or compressive forces). Thg string has a uniform mass per unit length.
An anchor chain or nylon rode closely approximates an ideal string. 

Glover: "The force at any point in the rode is the same as at any other 
point ....."

This is true only in one, idealized (ie, not practical) case. That is,
it is true only for a massless string pulled in a straight line.

In general, the statement is simply wrong, for two reasons. As Glover 
mentions, force is a vector (ie, it has both magnitude and direction).
Since a real anchor rode hangs in a catenary curve, and since only tensile
forces are possible, and since tensile forces can only be tangent to the
curve, it follows that the force is not constant. Rather, it is
constantly changing direction (and magnitude). 

That the force changes in magnitude also should be obvious. Imagine a 
chain hanging vertically. The bottom link supports no weight, the top 
link supports the weight of all the links below it. 

Mathematically, the total force on the string is an integral of the 
force per unit length along the string.

Glover argues, correctly, that more horizontal the pull on the anchor 
rode, at the anchor, the better (see also Note 373.0). Any upward pull 
will tend to pull the anchor out of the bottom.

Since I can't draw diagrams on a character cell terminal, you'll have to 
draw them youself.

Using X-Y coordinates with the X-axis horizontal and the Y-axis 
vertical, assume that the anchor end of the rode is at (0,0) and the
boat end at (X,Y). Further assume that the anchor rode has zero mass. 
Any non-zero horizontal force F (ie, from wind) applied to the boat will
pull the anchor rode into a straight line. 

The length L of the rode is 

	L = sq_root(X**2 + Y**2)


The horizonal load Ha on the anchor is also F (required by static 
equilibrium). The vertical load Va on the anchor from the tension in the 
anchor rode is:

	Va = F*(Y/X)
	   = F*tan(a)  where a is the angle between the rode and the bottom

Clearly, Va becomes less as X increases, or, alternatively, as L (scope) 
increases. 

Note that this assumption of a zero mass rode is a limiting case. With a 
sufficiently large force applied to the boat, even a rode with non-zero
mass will be pulled into essentially a straight line. Thus, the vertical
force pulling the anchor out of the bottom  will not exceed the value
calculated above when a horizontal force is applied to the boat.
Vertical forces applied to the boat, ie, waves, are another matter
entirely. For now, I'm only considering horizontal forces. 

Now, a bit of practical experience. When you anchor with a nylon rode, 
in calm or very light winds, the rode hangs in a downward curve. It 
takes only a little wind (a very few knots) to pull the rode into a
(nearly) straight line. For wind speeds above these few knots, the 
vertical load on the anchor is approximated by the above equation.

Since nylon rode sinks very slowly, I always tie a small weight (an 8 or
15 lb mushroom anchor) to our nylon rode at a distance from the bow chock a
little less than the water depth at low tide to keep the rode of fouling
on the keel, rudder, or propeller as the boat swings about the rode in a
calm. In gentle wind, I can see the rode to below the position of the
weight. The angle between the bottom and rode from the weight to the
anchor is clearly less than angle between the bottom and the rode from
the weight to the boat. That is, this additional weight reduces the
vertical pull on the anchor for any wind speed less than the wind speed
necessary to pull the rode straight. The use of the weight never
increases the vertical pull on the anchor over what it would be without
the weight. Note especially that the wind speed needed to pull the rode 
straight is higher than the wind speed required to do so without the 
weight.

Now, what of a chain rode? In a calm, the chain hangs straight down with 
most of it is on the bottom. There is zero vertical and horizontal load 
on the anchor.

As the wind increases, the boat moves away from the anchor and little by 
little the chain comes off the bottom. Eventually, all the chain is 
suspended in a catenary curve between the boat and the anchor. This 
curve can be described mathematically by:

	y = B + [C/W]*cosh[(W*x/C) + A]

	where A, B, and C are constants
	      W is the weight of the chain per unit length (eg, pounds 
              per foot)
	      and (x,y) are the coordinates of the chain curve

One end of the chain is at the anchor (0,0) and the other end at the 
boat (X,Y). 

The constants A, B, and C are determined from the above equation and the 
requirement that the length L of the chain between the end points (0,0) 
and (X,Y) be:

	L = (C/W)[sinh((W*X/C)+A) - sinh(A)]

That is, the constants are different for every (X,Y), which makes 
numerical calculations tedious at best. (cosh and sinh are hyberbolic 
cosine and sine.)

Messy? Right! (If you want to plow through the physics behind this, see, 
for example, "Mechanics" by Keith R Symon, Addison-Wesley, 1960. This is 
a second year college physics text.)

The tangent to this curve at (x,y) is 

	sinh[(W*x/c)+A]

which at the anchor reduces to sinh(A).

Glover (remember the article?) makes a major mistake about this point. 
He argues that the force on the anchor is minimized by increasing scope 
(correct) but not by increasing catenary, meaning increasing rode weight 
(incorrect). The weight of the rode reduces the angle between the rode 
and the anchor at the anchor for any wind speed less than that required
to pull the rode straight. The more weight in the rode, the better.
Sure, the weight of the rode causes the rode to be more vertical at the
boat, but so what? The bow just sinks a little to support the weight. 
The extra load on the deck fittings from a couple hundred feet of chain 
isn't particularly significant compared to the load the deck fittings 
must carry.

The sketch in the article (figure 3 on page 28) is misleading. An all-chain
rode of length L has a smaller angle at the anchor than a chain-nylon
rode combination of length L for any specific wind speed. With the
all-chain rode the boat will be closer to the anchor than it will be 
with the chain-nylon rode, not equidistant as shown in figure 3.

Glover is correct that the all-chain rode puts a higher load on the deck 
fittings than a nylon or nylon-chain rode, but this is something that 
can be managed. What is important is that an all-chain rode minimizes 
the vertical load on the anchor. The horizontal forces on the anchor are 
the same whether an all-chain rode or a nylon rode is used.

Of course, when an all-chain rode does become taut (as, say, from waves 
or very high winds), the shock loads are high and a length of nylon rope 
used as a shock absorber becomes essential. For any conditions less
severe than this, an all-chain rode is less likely to drag. Moreover, a 
boat anchored on an all-chain rode will swing in a smaller circle, which 
is nice in a crowded anchorage. 

However, the difficulties of handling an all-chain rode are such that
from a practical viewpoint in benign to moderate conditions a
chain-nylon rode is preferable. Our working rode is 40' of 5/16"
high-test chain and 300' of 1/2" three-strand nylon attached to a 35 lb
CQR. We have yet to need our storm rode of 200' of 5/16" chain and 300'
of 1/2" three-strand nylon attached to either a 45 lb CQR or a Fortress
FX-37.

I wonder if Cruising World would print my rebuttal to Glover's article?

Alan

    Alan, 
    
    Thanks for reinforcing my long held fear of math.....
    
    signed,
    
    John (who is always looking for a mooring rather than anchoring)
    

I finally got around to reading the article in question.  A quick glance told me
that it was not correct.  However, I did not invest the effort to examine why.

Considering the confusion caused in this notes file, I am certain that there are
many out there who could use enlightenment.  While trig may scare some off, the
point is that mathematics is designed to remove ambiguities, so I would send the
reply as is.  

The formal proof is left as an exercise for the reader.

Doug Claflin (whose search for the perfect cruiser is on hold until he returns
		from visiting brothers in Austrailia, and friends in Fiji,
		tough life )

re .67:

Below is a revision of reply .67 that I have sent to Cruising World 
magazine. There are some quite interesting (I think) numerical results
at the end of this revision. Actually, I have taken the analysis much
further, and I think I have found a way to generalize the numerical
results into widely useful simple tables. I have written a very
preliminary draft of an article describing my analysis and results that
I intend to submit to Ocean Navigator magazine. 

================================================================================

Editor
Cruising World Magazine
5 John Clarke Road
Newport, RI 02840


					4 August 1993


Dear Cruising World,

I think that there are some significant mistakes and quite wrong
conclusions in the article about anchoring by Rodney Glover in the July
1993 issue of Cruising World ("Let the Force Be With You", pp 26 & 28).
In the discussion below, I'll try to explain what I believe to be
correct. 

Some of physics and mathematics that follow is taken from "Mechanics" by
Keith R Symon, Addison-Wesley, 1960. This was the text for a university
second year physics course that I took many years ago. I have enclosed
copies of the two relevant pages. 

In physics, an ideal flexible string is one in which only tensile forces
tangent to the string are possible. An ideal string will not support
shearing or compressive forces nor bending moments. A chain or nylon
anchor rode closely approximates an ideal string. 

A catenary curve is the curve formed by a ideal flexible string with 
uniform mass per unit length hanging vertically under its own weight 
with no other applied forces other than the supporting forces at the 
ends of the string.

Mr. Glover is both unclear and contradictory in his use of the term
force. The forces acting on an anchor rode are the forces applied at the
ends of the rode by the anchor and the boat and the gravitational force
acting on the mass of the rode. 

The resulting tension in the rode is a vector. Mr. Glover says "the force 
[presumably meaning tension] at any point in the rode is the same as at 
any other point, and has a direction tangent to the curve; thus the 
direction of force [tension] is different at the boat, at the anchor 
and in the middle of the rode ....."

Here Mr. Glover contradicts himself. Since the direction of the tension 
vector changes along the rode, the tension (a vector) is NOT constant 
(ie, it is not the same). A constant vector is one whose direction AND
magnitude do not change. 

Mr. Glover further says "..... however the magnitude of the force [tension]
remains uniform throughout." This is simply wrong. A very simple example
shows the error. Imagine a chain hanging vertically. The bottom link
supports no weight, the top link supports the weight of all the chain
below it. Thus the tension at the bottom of the chain is zero and at the
top of the chain the tension equals the weight of the chain. Whether the
chain hangs vertically or in a catenary, the magnitude of the tension in
the chain (or rode) will vary continously along the chain (or rode).

Mr. Glover next says that because "chain outweighs rope, a chain rode
will develop a deeper catenary than a rope rode." This statement is
misleading at best. Equal lengths of rope and chain hung between the
same fixed supports will have the SAME catenary curve.  However, the
forces required to support the chain will be much higher due to the
greater weight of the chain. When a boat is anchored, the chain rode has
a deeper catenary because the boat is closer to the anchor with a chain
rode than with a rope rode for the same length rodes and the same wind
pressure on the boat. 

"The more vertical the line at the boat, the greater the required force in 
the line, and the greater the force on the anchor." This statement is 
also not correct, in general.

When a system is in equilibrium, the sum of the horizontal and vertical 
forces must be zero. Specifically, when a boat is anchored, the 
horizontal wind force on the boat is balanced by the horizontal force of 
the bottom acting on the anchor. The gravitational forces acting on the 
anchor rode are VERTICAL. The bouyancy of the boat counteracts the 
downward gravitational force on the anchor rode. The horizontal load on 
the anchor must be the same for both rope and chain rodes.

Mr. Glover is correct in saying that any upward pull on the anchor will tend 
to pull the anchor out of the bottom and that, therefore, the load on 
the anchor should be as nearly horizontal as possible. Hereafter, 
though, Mr. Glover goes astray again.

Looking at the physics and mathematics of catenary curves applied to an
anchored boat is most illuminating and instructive. 

Assume that the anchor rode is hanging in the XY-plane with the X-axis
horizontal and the Y-axis vertical. The catenary curve of the anchor rode
is described mathematically by: 

	y = B + (C/W)*cosh[(W*x/C) + A]			(eq. 1)

	where A, B, and C are constants
	      W is the weight of the rode per unit length 
		(eg, pounds per foot)
	      and (x,y) are the coordinates of the catenary curve

The slope of the tangent to the curve is:

	slope = dy/dx = sinh[(W*x)/C + A]		(eq. 2)

The tension at any point along the rode is a vector whose horizontal 
component is constant:

	C = T*cos(theta)				(eq. 3)

	where T is the magnitude of the tension
	      and theta is the angle between the tension vector 
                and the X-axis

The constants A, B, and C are such that x and y have the proper
values at the ends of the rode and such that the total length L of the
rode has the proper value. Length L is given by: 

	L = (C/W)*[sinh((W*X1/C) + A) - sinh((W*X0/C) + A)]	(eq. 4)

	where (X1,Y1) and (X0,Y0) are the end points of the rode

So much for abstract physics. What does all this mean in real life? 
Here practical experience provides useful initial insight.

Assume that there is no wind, and thus no horizontal force on the boat. 
The anchor rode will hang vertically with most of the rode lying on 
the bottom. There will be zero vertical and horizontal load on the anchor.

As the wind increases, the boat moves away from the anchor and little by 
little the rode comes off the bottom. The rode suspended between the 
boat and the bottom will hang in a catenary curve. Eventually, all the rode 
is off the bottom and hanging in a catenary curve.

Let's examine more closely the situation where the anchor end of the 
rode is just barely lying on the bottom -- that is, the anchor rode is 
still just horizontal at the anchor and thus can apply only a horizontal 
load on the anchor.

Let the (x,y) position of the anchor be (0,0) and the upper end of the
chain be at (X,Y). Since the chain is horizontal at (0,0), the slope of
the catenary curve must be zero at (0,0). Equation 2 then reduces
to: 

	0 = sinh(A)

This implies that the constant A = 0. 

At (0,0) equation 1 becomes:

	0 = B + C/W				(eq. 5)

At (X,Y) equation 1 becomes:

	Y = B + (C/W)*cosh(W*X/C)		(eq. 6)

Subtracting equation 5 from equation 6 gives

	Y = (C/W)*[cosh(W*X/C) - 1]		(eq. 7)

Equation 4 becomes:

	L = (C/W)*sinh(W*X/C)			(eq. 8)

Equations 7 and 8 are two equations in two unknowns (C and X) for a 
given values of L (rode length) and Y (the vertical distance from the 
bottom to the bow chock of the boat). 

Unfortunately, there is no simple solution to these equations, and the
unique values of C and X  that satisfy both equations 7 and 8 must by
found by guessing. Fortunately, repetitive guessing is easy with a 
simple computer program or a programmable calculator. 

From equation 3, as long as part of the rode is lying on the 
bottom, the horizontal load on the anchor is C. 

Also from equation 3, the horizontal force at the top of the anchor 
chain can be calculated by:

	Fh = C/cos(theta)
	   = C/cos(arctan(sinh(W*X/C)))			(eq. 9)

This horizontal force is equal to the wind pressure on the boat
(ignoring currents and wave action). An empirical formula for the
horizontal force Fh on a boat headed into the wind is: 

	Fh = .000134 * LOA * LOA * S * S		(eq. 10)
	where Fh is in pounds
	      length overall LOA is in feet
              and wind speed S is in knots

So as to have some specific numbers to work with, let's assume that a 
32' boat is to be anchored in about 40' of water (Y = 40') with either a 1/2" 
diameter nylon rode or a 5/16" chain rode, and that both rodes are 200' long. 

With corrections for bouyancy, the approximate values of W for these two 
rodes are:

  0.015 pounds per foot for 1/2 inch diameter 3-strand nylon rope
  0.91 pounds per foot for 5/16 inch hi-test chain

Using equations 7, 8, 9, and 10, it is found that:

                    C        Fh       S        X
                  pounds   pounds   knots    feet

  nylon            7.20     7.80     7.5    194.63
  chain          436.8    473.2     58.7    194.63

What these results say, quite simply, is that once the wind speed 
exceeds 7.5 knots, the nylon rode will begin to pull upward on the
anchor. By comparison, the chain rode won't begin to pull upward until 
the wind speed is over 58.7 knots. Clearly, then, the additional weight 
of a chain rode keeps the pull on the anchor horizontal at significantly 
higher wind speeds than does a nylon rode. In fact, under the assumed 
conditions, the nylon rode must be about 1588 feet long (40:1 scope) to 
keep the pull on the anchor horizontal at a wind speed of 58.7 knots. This 
further demonstrates the value of a chain (ie, heavy) rode.

A final comment. Figure 3 in Mr. Glover's article is also incorrect.
Rode A, the chain rode, will lie below Rode B, the chain/rope rode, at
any wind speed below that required to stretch the rodes taut. 

In summary: 

What is important is to keep the pull on the anchor as horizontal as
possible. The mathematics above shows that this done more effectively by
increasing rode weight than by increasing scope. Yes, certainly a
heavier rode increases the tension in the rode at the boat (and hence
load on deck fittings) but the horizontal load on the anchor (as
discussed above) remains the same whether a light or a heavy rode is
used. 

Respectfully yours,

    Neat math Alan !
    
    I'll take all of the formulae at face value ..... there is no way I
    would try to follow the logic given my math skills, however your
    analysis covers both ends of the situation but not the middle ....
    
    How does your analysis stack up for say 20% chain and 80% rode,
    similarly putting a rider on a nylon rode ...presumably your analysis
    can tell where and what weight to put there ?
    
    given a set of variables such as weight to carry, cost etc. presumably
    you can plug in certain values and get the optimum rode for any boat ?

re .70:

It might be interesting to extend your analysis to the case where a section
of chain is used at the anchor end of the rode. A relatively short section of
chain will develop a sufficient catenary. This is the basis for the common
recommendation of 6-12' of chain at the anchor end of a nylon rode.

For a full understanding, it's necessary to extend the analysis to cover the
tradeoff between the catenary effect of a chain, and the stretching ability of a
nylon rode. In a real anchoring environment, the anchor would break free during
a brief interval of maximum rode tension, typically when a wave hits the bow. In
the case of chain rode, the full wave force will be applied directly to flatten
the catenary. In the case of a nylon rode, more of the wave force will be
applied to acceleration of the boat mass, because of the substantial stretch of
the nylon rode. The average tension on the rode will be similar in both cases,
but the peak rode tension will be much higher for an all-chain rode.

--RS

re .71:

>>>    How does your analysis stack up for say 20% chain and 80% [nylon] rode

I haven't tried to work out the mathematics/physics of such a rode. The 
boundary conditions (ie, the slope of the chain catenary and the rope 
catenary at the chain/rode junction must be the same) might get messy 
and result in rather a lot of constants to guess. It would be an 
excellent extension to my analysis, however. I'm sorta motivated to 
investigate since this is just the rode we use.

>>>    similarly putting a rider on a nylon rode ...presumably your analysis
>>>    can tell where and what weight to put there ?

Now you're making life really difficult! The use of a rider is more 
solvable, I'd guess, if you assume only a nylon rode and ignore the 
catenary. 
    
>>>    given a set of variables such as weight to carry, cost etc. presumably
>>>    you can plug in certain values and get the optimum rode for any boat ?

Optimum rode? Probably not, just a good choice.


re .72:

You are of course right that the peak rode tension when a chain rode 
goes taut is very, very high and a length of shock-absorbing nylon is an 
excellent idea, in general.

However, it is interesting to look at more results given by the physics 
and mathematics.

Assume I anchor my 32' boat in 40' of water and lay out 200' (5:1 scope) 
of 5/16 inch chain. Assume that a 20 knot wind is blowing. Do I have 
adequate scope?

Solving the equations shows that some 140 feet [!] of chain will still be
lying on the bottom. The chain will not go nearly taut until the wind 
exceeds 58 knots or so. With only the 20 knot wind, it would take a 
rather unusually large wave (in the usual protected anchorage) to take
the slack out of the chain. 

This type of result would tend to indicate that a nylon shock absorber
is only necessary when anchoring with marginally small scope using
chain. One point to keep in mind is that once the rode (chain or nylon)
goes taut, there is an upward pull on the anchor, which will tend to
cause the anchor to break out of the bottom (definitely not what you
want to happen). The tension needed to stretch a nylon rode will
further increase the upward pull, but of course not as much as will
forcing the bow down into a wave with a chain rode. 

The general analysis I'm hoping to do will take into account wind, 
waves, and the boat veering about the rode and will predict what scope 
with what rode will likely be safe, where safe is no upward pull on the 
anchor. This, though, begs the question as to how strong the bottom is 
and how much resistance there is to the anchor dragging horizontally.

When all is said and done, there are/will be many uncertainties in 
anchoring and good judgment and good fortune will still be a factor. 

Alan

    Alan,
    
    I believe you are using the term "physics" incorrectly. Physics is
    the study of matter, energy, and their interactions. Anchoring a 
    boat has little to do w/ the theory of relativity.
    
    I think you'd be better off using the term "dynamics" - the study of
    energy, force, and motion. I say this even though your analysis is based
    on statics. 
    
    Although I haven't read the article in Cruising World, I don't quite
    agree with your criticism of the excerpts around the word "tension". 
    I feel it is proper to define a chain or rope as being in tension. This
    means the chain or rope is subject to tensile forces. "Tension" should
    not be considered a vector. Tension desribes the effect of forces on
    the structure or mechanical system. A tensile force produces a tensile
    stress and a compressive force produces a compressive stress. This
    should not be confused with a vector or the two properties of vectors:
    magnitude and direction.
    
    Paul 

re .74:

Well, physics is a quite broad discipline that includes mechanics --
the study of forces acting on bodies, both statically and dynamically. I
took mechanics courses both as an undergraduate and as a graduate
physics student. The textbook I referred to was the text for one of my 
undergraduate physics courses in mechanics. I rather thought that 
"physics" would be more meaningful to most people than "mechanics". 

As to whether or not tension is a vector ..... it is. All forces and
loads, be they compressive, tensile, shearing, or bending, have both
direction and magnitude. Much or most of the time the vector nature of
forces is conveniently ignored because doing so makes the mathematics
much, much simpler. It is easier to understand magnitudes alone than
magnitudes and directions (vectors). Differential and integral vector
equations are considerably less fun to play with than scalar equations. 
(Besides, my textbook says tension is a vector.) Indeed, in the physics 
texts I have boldface type is used to denote vectors and non-boldface 
type is used for the magnitude of vectors and for other non-vector 
quantities to eliminate ambiguity.

Any introductory mechanical engineering or physics (mechanics) text that
discusses static equilibrium of systems (an anchored boat, for example)
of necessity begins with a discussion of vectors. A system will be in
static equilibrium (ie, nothing moves) only if the vector sum of all
applied forces is zero. And I am not about to venture into any 
discussion of the dynamics of an anchored boat. The mathematical
complexity of that is vastly more than I care to (or perhaps can) 
understand.

Alan

    Alan, your mathematical analysis of anchor rodes etc. was interesting.
    I think the 'catch' in attempting to do a precise mathematical analysis
    of a complex situation is accurately figuring the constants.  In this
    case, the resistance of the bottom to the anchor dragging.  Of course
    the bottom is not going to be uniform... even a mud bottom will have
    occasional stones in it for the anchor to drag into.  I am not
    implying that you didn't take the variability of bottom condtions 
    into account, I am just expanding on that aspect a bit.
    
    Jeff

re .76:

Oh yes, absolutely, the bottom is a critical part of anchoring puzzle and the 
perhaps the one least under our control. If the bottom won't withstand 
the force of the anchor ..... well, let's just say it'll be a drag. 

My hope is that looking at some of the physics and mathematics will 
confirm that the empirical rules are right (eg, use 7:1 scope) and will 
show their assumptions and limitations and maybe where they go astray.
It is the catenary in a chain rode that provides shock absorption,
right? Well, not really. Note to follow. 

Alan 

    The boat we sailed last week had an interesting anchor arrangement.
    I have not seen it before.  She had three anchors, a hefty CQR, a big
    fisherman, and a little Danforth lunch hook.  
    
    All had nylon rode with chain at the anchor end, but the "everyday"
    anchor, the CQR, was arranged to have a long chain catenary:
    
    	(-|=ooooo------------------oooooooooooooooooo-----------------------
    
     anchor  6' chain    80' nylon	20' chain	100' nylon
    
    Worked well, though we didn't put a lot of stress on it. Things were
    pretty quiet except for one night of thundersqualls and wind shifts.
    No wave action to speak of.  We had it all out that  night but - as
    usual - were more worried about our 15 neighbors' arrangements than our
    own.
    
    Lois

    Hmmm. Sounds as if whoever set that boat up knew what they were doing.
    Big CQR and big fisherman sound appropriate for crusing given varied
    bottom conditions.
    
    Alan:  How is it that straigntening the chain anchor rode out doesn't
    supply shock protection?  Once the chain is taught, then, yes, NO
    shock protection, but with a catenary it takes force (uh oh, vectors
    and math again) to straighten that chain out.
    
    Yes, I did read your earlier note that went into the math of it, but
    if the explanation is in there I missed it.
    
    Jeff

The catenary of a chain rode, everyone says, provides shock absorption. 
In a sense, everyone is wrong. Except me, of course, he says with an 
engaging grin. 

Please refer back to the mathematics in Note 373.70.

Assume that the anchor is at (0,0) in the XY-plane with the X-axis 
horizontal and the Y-axis vertical. Assume that the Y distance from the 
bottom to the bow roller is 40' and that 200' of anchor chain have been 
veered. If the chain is pulled taut (ie, into a straight line), the 
X-coordinate of the bow roller is 195.96' (by simple trigonometry).

Now assume that all 200' of chain are hanging in a catenary curve with 
the anchor end of the chain just horizontal. Solving the catenary 
equations 7 and 9 in Note 373.70 gives 194.62' [!] as the X-coordinate 
of the bow roller. Clearly, the boat need move only 1.34' further from 
the anchor to pull the chain taut. If you plot the catenary curve for
the conditions given, you'll find that at its center the chain hangs a bit
over 10' below the straight line from the anchor to the bow roller, 
which does seem like a lot. 

What is really happening seems to be this: Most of the chain is actually
lying on the bottom. As the waves roll past and as the wind gusts, more
chain is lifted off the bottom momentarily and then falls back onto the
bottom as the load on the rode decreases again. It is this excess chain
lying on the bottom that provides the shock absorbing, not the chain off
the bottom hanging in a catenary. Yes, this result surprised me, too.
So, it is strictly speaking not correct to say that the chain in the
catenary provides shock absorption. 

More surprising results when I have time. 

Alan

    Alan, I have drawn a diagram out to be better able to picture what
    your saying.  But there 'IS' 1.34' feet of shock absorption there in
    the catenary because thats the actual slack in the catenary in your
    example.  Do you agree?  1.34' feet of shock absorption in this case,
    PLUS the lifting the chain off the bottom prior to the chain forming
    a catenary.
    
    If there was NO slack in the chain at ALL then there would be essently
    no shock absorption assuming that no other materials such as nylon was
    being used in the mooring setup.
    
    Using nylon would provide shock aborption MOSTLY in the stretch of the
    nylon after its catenary slack was taken up which would be the SAME
    amount of slack given the same example, right?
    
    So it sounds to me that if the chain is HEAVY enough relative to the
    weight of the boat and weather conditions then the chain EFFECTIVELY
    provides shock absorption as its lifted off the bottom into a catenary.
    
    The nylon on the other hand provides shock absorption primary by
    stretching.
    
    
    Jeff

                      <<< Note 373.81 by SALEM::GILMAN >>>
                                   -< Slack >-

    Alan, I have drawn a diagram out to be better able to picture what
    your saying.  But there 'IS' 1.34' feet of shock absorption there in
    the catenary because thats the actual slack in the catenary in your
    example.  Do you agree?  1.34' feet of shock absorption in this case,
    PLUS the lifting the chain off the bottom prior to the chain forming
    a catenary.

>>> No plus. My calculation was for ALL of the chain hanging in the 
>>> catenary -- none on the bottom.
    
    If there was NO slack in the chain at ALL then there would be essently
    no shock absorption assuming that no other materials such as nylon was
    being used in the mooring setup.

>>> Right. 

    Using nylon would provide shock aborption MOSTLY in the stretch of the
    nylon after its catenary slack was taken up which would be the SAME
    amount of slack given the same example, right?
    
    So it sounds to me that if the chain is HEAVY enough relative to the
    weight of the boat and weather conditions then the chain EFFECTIVELY
    provides shock absorption as its lifted off the bottom into a catenary.

>>> My point exactly. It is the chain lying on the bottom that provides 
>>> the shock absorption, not the chain actually hanging in the 
>>> catenary, which is what all the literature says (incorrectly).
    
    The nylon on the other hand provides shock absorption primary by
    stretching.

>>> Right.    
    
    Jeff

    One more thing.....
    
    The chain is 'TRYING' to fall back to the bottom which is pulling on
    the bow of the boat resisting the boats pull.  Of course the chain is
    also pulling equally on the anchor trying to drag IT horizontally.
    
    
    "But that is a VERTICAL pull on the boat" not horizontal which is what
    counts as far as resisting the boats pull to drift away.  Yes but the
    chain weighs far more than the nylon and when the chain is pulled into
    a catenary a COMPONENT of that pull is NOT vertical, but horizontal.
    
    But the net result is an increased pull on the anchor (equal and
    opposite) to the pull on the boat so we gain nothing as far as helping
    the anchor resist dragging because the chain weight tries to drag the
    anchor as the boat lifts the chain into a catenary.  So, actually the
    chain doesn't buy us a thing over nylon except chafe resistance.
    
    Does my argument make any sense?
    
    Jeff

    Oh, yes we do gain one more thing with chain.  The weight of the chain
    tends to keep the pull on the anchor more horizontal until its lifted
    into a catenary.
    
    So we gain a more horizontal pull on the anchor in the early stages of
    increasing strain on the mooring, and chafe resistance.
    
    Agreed?
    
    Jeff

    It seems to me that what happens is that any initial shock is
    transmitted to the catenary, putting a wave of additional tightness
    into it. Then,  when the shock wave gets to the chain on the bottom, it
    lifts up whatever is needed to absorb the additional load. In addition,
    the movement of the line and chain through the water (vertially) acts as a
    damper, so there is probably a good chance that the wave never gets
    down to the chain anyway. Analyzing this would certainly move it out of
    the "statics" case into the "dynamics" case.
    
    WRT the complicated arrangements of line-chain-line-chain-anchor, I
    would say that at this point it's probably worth it to move away from
    an analytical approach and over to a simulation based on iteration.
    After the initial work of getting it set up, this would allow you to
    handle any complicated (static) case.
    
    Doug.

The horizontal pull on the boat and on the anchor is exactly the force applied
to the boat by the weather. Some of this force may actually be applied to the
bottom through the chain laying on the bottom, so the anchor doesn't necessarily
see 100% of this force.

The vertical pull on the bow of the boat is exactly the net weight of the chain
in the catenary. (This follows from conservation of force. There is no downward
force except gravity acting on the rode.) The vertical pull cannot exceed the
weight of the rode until the rode has all lifted off the bottom and a vertical
force component is applied to the anchor.

A nylon rode has very little net weight in the water. If there is no chain at
the anchor end, the scope must be high to give the anchor a low enough attack
angle to set. (Even a modest length of chain helps *a lot*.)

--RS

    As Alan indicated there is 1.34' of slack in the chain catenary in the
    example he used.
    
    That 1.34' WOULD be available for shock absorption (I believe) in
    addition to the damping effect of the weight of the chain.
    
    Jeff

re .87

Uh, the slack in the catenary really is very little. Referring back to .80:

  Assume that the anchor is at (0,0) in the XY-plane with the X-axis 
  horizontal and the Y-axis vertical. Assume that the Y distance from the 
  bottom to the bow roller is 40' and that 200' of anchor chain have been 
  veered. If the chain is pulled taut (ie, into a straight line), the 
  X-coordinate of the bow roller is 195.96' (by simple trigonometry).

  Now assume that all 200' of chain are hanging in a catenary curve with 
  the anchor end of the chain just horizontal. Solving the catenary 
  equations 7 and 9 in Note 373.70 gives 194.62' [!] as the X-coordinate 
  of the bow roller. Clearly, the boat need move only 1.34' further from 
  the anchor to pull the chain taut. 

The horizontal force required to pull the 200' of rode into this 
catenary depends on the weight per foot of the rode. For 5/16" chain, 
the horizontal force is some 473 pounds. The force required to pull the 
chain into a straight line (ie, completely taut) is mathematically 
infinite. That is, the horizontal load rises from somewhat less than 500 
pounds to an extremely high value as the boat moves less than a foot and a 
half. This is precisely why a stretchy length of nylon rode is needed.

Because the specific gravity of nylon rope is close to that of sea 
water, the effective weight of a nylon rode is very low. The horizontal 
force required to pull 200' of 1/2" nylon rode into a catenary is less 
than 10 pounds.

    Yup, I understand.  My point is that there is still SOME slack there,
    granted, its not much, but its THERE (1.34' in your example).  So what?
    its not enough to matter.... right, understood but there is some there.
    
    The vast majority of the shock absorption is coming from lifting the
    chain off the bottom into a catenary.  Right, understood.
    
    Jeff

    I still think that most of the shock is absorbed by the movement of the
    rope in the water. Say the rope moves an average of 1" vertically.
    That's a lot of drag. Simple first cut: say the rope is .5" in diameter.
    Total area is 2400" x .5" = 1200 sq in or about 8 square feet...

    I would agree with your statement if the word INITIAL is put into the
    statement: "most of the INITIAL shock is absorbed by the movement of
    the rope through the water".
    
    Jeff

    I thought I'd recommend a book that discusses storm anchoring, forces,
    chain vs. nylon, etc.  It's Oceanography and Seamanship by William
    Van Dorn.  It is a bit mathematical in places.  The author has
    provided many graphs which help visualize trends and relationships.
    
    He also discusses the advantages of anchoring with relatively short
    scope (<4:1) in deep water during major storms, what's wrong with
    all chain rodes in most practical situations, the relative lack of
    elasticity in chain despite the catenary, and many other topics.
    One of his claims is that a major cause of anchoring failure is not
    surge, but swinging (combined yaw and sway).
    
    Toward the end of the chapter on anchoring, he also analyzes 
    requirements for light, medium, and heavy vessels and recommends 
    the use of special non-metallic thimbles that totally the nylon rode.
    He provides a diagram of his thimble design since I don't believe
    they are available commercially.  Surprisingly, although he shows a
    swivel link joining the nylon and chain, he doesn't discuss this 
    potential weak point.
    
    Is anyone else familiar with this book?  I'd be interested in 
    reactions/opinions.

    Has the following experiment been tried?
    
    Proposition: The bulk of the impulse load on the anchor system is from
    yaw and pitch, which is maximized by hooking the line to the boat at
    the bow. This can be minimized by hooking the line on as near to the
    center of motion (whatever that's officially called), either by say an
    attachment to the middle of the keel or by having two lines, one on
    each side at the middle, that meet below the keel (say maybe 50' long)
    and then attach to the anchor line. A small line would also be needed
    to the bow to keep the boat pointed into the wind, but this would not
    carry the bulk of the load so it could have a lot more stretch.
    
    Doug.

    Doug, thats an interesting idea but has some major drawbacks:
    
        I don't think your light line would be ABLE to keep the bow into 
    the wind/waves because the storm/waves/wind are TRYING to push the boat
    broadside.  The second the bow got pushed at an angle to the wind the load
    on the light bow line would increase tremendously.... to the point
    where the load on the mooring would be the same as if it wern't a light
    line (in which case you might as well moor the boat via a heavy line to
    the bow in the first place) or the light line would part and the boat
    would immediately be pushed broadside to the wind/waves and the load on
    the mooring would now soar because of the increased surface are of the
    boat to the wind..... as well as risking the boat being swamped by
    being broadside to the wind/seas.
    
      The fact that boats yaw/pitch in severe winds/waves when on moorings
    illustates the fact that the boat 'wants' to go beam to the wind/seas
    and that the mooring system is whats stopping it via a line to the bow.
    Its a full circle... the place to tie the boat to stop it from going
    beam to the wind/seas is at the bow, which puts a load on the mooring
    due to yaw and pitch.............
    
      How about a riding sail at the stern similiar to the type lobster
    boats or some commercial fishing boats use?  The riding sail sails the
    boat bow on to the wind... even when anchored or moored.  The riding
    sail would help with the yaw but not the pitch.  
    
     Obviously there are no panaceas' here short of pulling the boat from
    the water during poor weather.
    
    Jeff

re .94 and riding sails:

See Note 146 (and perhaps other notes) for some discussion of riding
sails. Our riding sail has kept our bow into the wind plus/minus maybe 5
degrees in 30 knot winds. Not having the boat constantly heeling from
the wind as the boat swings back and forth is very nice. 

re .70:

Well, no reply from the editors of Cruising World. They did, however, 
forward my letter to Rodney Glover, who in turn sent me a long letter.

The gist of Mr Glover's reply was:

  The editors reduced the length of the article by about two-thirds and 
  deleted about half the diagrams.

  The article was written for the non-technical reader, and hence the 
  less than precise and accurate use of technical terms (I think that
  the technical terms should have been either used properly or not used 
  at all).

  That because the article was for the non-technical reader, many 
  simplifications were made (I think that these should have been noted).

  That the conclusions presented in the article are basically correct
  and will not mislead anyone (well, maybe).

All of this reinforces my feeling of skepticism when reading "technical" 
articles in magazines such as Cruising World. First, it is unclear that the 
authors are experts (Mr Glover does seem to be credible in his letter to 
me), and, even if they are, the editting of the articles may result in 
inaccuracies or misleading information. 

Alan

    Glad you at least got a resposne to your long letter Alan.  I am not
    sure whether he is twisting and squirming or simply citing the facts
    as to why the article wasn't technically correct.
    
    Interesting
    
    Jeff

I am in the market for a new anchor, #20 CQR doesn't make for me.

I am considering a #25 CQR, #22 Bruce and the Max anchor.

The Max is made in Natches Mis.  It looks similar to a Bruce.

West Marine does not like, Practical Sailor does.  The recent anchor
tests I have seen, indicate that this might be a good anhor for around
here, sand and mud type conditions.  Like the Bruce they are willing to
claim very short scopes.  While this is not something I want to test, the
ability to set a short scope may come in handy.

Does anyone have any opinions and information.

Forinstance 
	What is a comparable sized Max to the other two anchors?
	What is the price?
	Does anyone have a contact number?
	Anyone use one? or for that matter see one?
	Is it any harder of easier to store than a Bruce?
	How easily does it break free?
	What is your opinion between the three anchors?

I am going to duck now as the mud begins to fly.

Doug
dtn 381-6355
	 

re .98:

In my opinion, any claim of effectiveness with short scope should be 
viewed with great skepticism and even total disbelief.

The force required to pull an anchor through the bottom depends on the 
cohesiveness or strength of the bottom and the area of the anchor 
perpendicular to the direction of the pull or applied load. 

The upward pull on an anchor increases rapidly as scope decreases. See 
Note 373.0. An anchor with larger fluke area will be more likely to hold 
on short scope than an anchor with smaller fluke area, but ......

But the holding ability will depend on how deeply buried the anchor is, the 
nature of the bottom, the strength of the anchor, the scope, etc. Using 
minimal scope is unnecessarily risky. Why do it? (True, I tend to anchor 
in relatively uncrowded anchorages down East.)

Another consideration. If there is significant upward pull on the 
anchor, it will be much less likely to reset if it does break out. With 
short scope, the upward pull can easily exceed the weight of the anchor, 
This implies that if it does break out, it will NOT reset. A thought not 
conducive to restful sleep.

Alan

From:   (a long-time liveaboard friend who know vastly much about anchoring)
To:	Alan Berens Digital UNIX Support  08-May-1996 1057 <unifix::berens>
CC:	
Subj:	Re: MAX anchors

>Hi Ed,
>
>Know anything about MAX anchors? Any opinions? An acquaintance at DEC is 
>considering buying one. All I know about them is what I've read in 
>Practical Sailor, which is mixed.
>
>Cheerio,
>
>Alan

Alan,

You know more than I (or is it me?) Just looking at them I'd expect them to
come up pretty dirty. Is this good? They look awful to stow (I understand
they come with a SS plate to go over your bow?) Unless they had some
attractive feature I'd wait for a friend to buy one first! Volunteers?? (I
guess we should encourage this fellow!)

I tend to agree.

So far there has been only two times where I felt tempt to anchor on a short
scope.  Strangely enough, both were on my trip to Maine last year.

Once was in Cape Porpise.  The mess of lobster pots made it unclear as to where
the anchorage was, and boats were close together.  I headed to the edge, put the
anchor down with about 6:1 at high tide.  We ate dinner as the tide started to
ebb.  I spent the night laying to about 8:1 rode.  The lobsterme kindly woke me
up at 4:30 to check on my rode.

The second time was in Jewell Island.  We got in fairly late.  The anchorage was
pretty full.  We went up towards the head of the cove.  Laying out 7:1 rode on
the CQR put us uncomfortably close to a neighbor.  I Shortened scope to about
5:1.  I did not feel good about that.  So I rowed a danforth out over the shoal
area.  Probably got about 180' of line out (nominally 7.5:1 at high tide).  I
lowered the danforth and then set it in anticipation of a wind shift.  The rode
for the danforth lay slack.  In the morning, there was ocassional tension on the
danforth rode.  It looked as though we rode on the plaw through the night.

Logic aside, the purist in me likes one anchor, my wife and sleep like multiple
anchors.

From a practical standpoint, claim of short scope are sort of like top end on
cars.  More than something you might use, it implies a level of performance in
more normal situations; i.e. a short scope anchor may do well in soft bottom
conditions which are heck on a danforth style design.  It may also be more
tolerant of my wife laying out a short rode during anchoring.  For a number of
reasons, she needs to be at the helm more, and I on the deck (she is better at
most deck work2, I am a better helmsman).

A sailors should have a competent SO to cruise with.

Doug
dtn 381-6355

	Wow, 7:1, 8:1, 5:1!! I wish we had the space. Most commonly we are on
about 3:1 scope in the places we anchor. 4:1 feels good, but I also don't count
the 10' of chain on the anchor end. Spending time in Hadley's Harbor we can
rarely get out mor than 3:1 there without risking swinging in to someone. 
	I do seek out the best protection we can find as the lightweight boat
will bounce around a lot on the slightest waves. We also can hit some very
shallow water and have been in less that 5' at Cuttyhunk (that was actually
somehting like 6:1 at low water). 
	Actually, most of the time in Maine we picked up a mooring. We did
anchor in the Basin and there was noone there to swing into. We use a Delta
primarily on the Trimaran and also cary a Fortress. I used the fortress on the
S2 exclusively and it held stron in at least 1 very challenging anchorage (I may
have gotten out a lot of scope on that one). 

	I guess I do cheat myself into believing my scope is less than it really
is. We normally set in 10-15 feet of water and I don't count that 10' of chain.
(I have my rode marked and note the depth when the anchor is let down. 


	Geoff

To start with, I do consider my 16' of chain part of the scope.  From your note,
I would consider the anchoring that you do to be more typically 4:1, and often
5:1.  On nice nights, especailly in a place I have been to before, I can see
doing that.  In new places, I am chicken.

I have never tried to anchor in Hadleys on the weekend.  Well OK friday night.
I try to avoid the peak times.  Tarpaulin Cove on Saturday can be crowded, either
Friday or Sunday night will see just a few boats.  It also helps that I draw less
than 4'.  One of the advantages of a full keel.

I was wondering, can you anchor up the "east part of Hadley's (i.e. go left where
the ferry goes right.  Also how close can you go to Bass Island (the dingy dock)?

The one time I was in Cuttyhunk, we were way over by the edge of the anchor area.
The result was more space, and shallower water.  Sort of go together.

In general I look for shallow water.  Less rode is required.  You often can sneak
behind a little corner of land, making the ride at night even better.  There is
usually more space around the edges.  Most newer boats have deeper fin keels and
want alot of space under it.

When I have anchored at Vinyard Haven, there is space outside the breakwall, but
it is a looonng row into shore.  I must confess to using a little less scope. 
The holding ground is excellent, and about 25 feet down.  I usually let out about
5:1 there.  

I also pay attention to the anticipated wind and current.  Thus I often cheat a
little as to where I drop the hook, into the prevailing wind and current.  Then
out goes a second anchor on a short scope with lots of slack.  If bad things
happen and I swing the wrong way, the second anchor is supposed to keep things
from going bump in the night.

When we anchored in Maine (just a couple of times), it was in non crowded places.
Aside from the fact that holding at Isle of Shoals is miserable, it is crowded. 
We snagged a mooring there, and South Freeport.  Jewell Island gets crowded, so
we arranged our vacation for a week night.  Probably could not even get in on the
weekend.

Holiday II should be at Woods Hole in July.  Keep in touch.

Doug,

I love my 10Kg Bruce!  I have had trouble setting it on leafy bottoms but
on sandy and muddy bottoms it has worked very well.

I have no experience with New England anchorages ... all my sailing is on
the Chesapeake Bay.  My boat is a Hunter 34'.  I use 20' of chain and like
a 7:1 scope if there is room.  In flat water I have successfully used 4:1.
As previously noted, however, this is not recommended.

I'd vote for the Bruce.  It's simple, strong, sets easily (except as 
indicated above), and plucks out nicely.

Keith

I replaced a CQR anchor with a Bruce and was very happy with the results.
A Bruce has more holding power than a CQR of the same weight. I believe it
was originally developed for anchoring oil rigs.

As an aside, if you guys think you have problems with scope, try anchoring in
the Channel Islands, which have a tidal range of more than 10 metres (33 feet)
at springs!

Dave

    Has anyone read (or experienced) comparisons of the Delta anchor to the
    Bruce, CQR, etc. There may have been a note in here somewhere about
    that but I couldn't find it. I am planning to add another anchor to
    Viking Rose and would like diversity. We currently carry light weight
    and plow styles.
    
    	Howard