Who is Richard Macfarlane? Here is his anchoring advice...

[Lodesman]

Originally Posted by Chotu

“No wind or current” is a relative term in my post. Not an absolute term.

"Relative" to what? As opposed to there being a component of horizontal force acting on the anchored vessel? If you write something that is absolute nonsense, expect to be called on it.

[rslifkin]

The light chain / heavy anchor thing is definitely better for a given total weight of ground tackle. If you step down a lighter, higher grade chain, you still have plenty of strength, but have saved enough weight to fit a much bigger anchor and still add more length of chain in the locker. Going from 3/8" BBB to 5/16" G43 reduces the chain from about 1.5 lbs / foot to just over 1 lb / foot, as an example.



The lighter chain will run out of catenary sooner, but unless you're in deep water with a lot of fairly heavy chain (such as 300+ feet in 80+ feet of water), you're going to pull the useful catenary out of the chain in high winds either way. The lighter chain just might need a slightly longer / stretchier snubber to account for the reduced catenary.



The bigger anchor will always hold better. Basically, 20 lbs of larger anchor is worth a lot more than 20 lbs of extra chain in terms of holding power. Of course, if weight is a complete non-issue for the boat in question, having both won't hurt.

[longjonsilver]

Originally Posted by Lodesman

What do you base this on? Empirical testing? Pet theory? I'd like to hear the logic behind this.

Would you rather hold your boat in a gale with an anchor and no chain or chain and no anchor? Pound for pound an anchor is a better use of weight than chain.

jon

[boatman61]

Originally Posted by longjonsilver

Would you rather hold your boat in a gale with an anchor and no chain or chain and no anchor? Pound for pound an anchor is a better use of weight than chain.

jon

Neither.. Chain and anchor every time..
Anchor and rope sucks.
That's assuming your not saying just chuck the unattached anchor over the bow..

[Lodesman]

Originally Posted by longjonsilver

Would you rather hold your boat in a gale with an anchor and no chain or chain and no anchor? Pound for pound an anchor is a better use of weight than chain.

jon

What boatie said. The anchor and chain work together as a system - one really doesn't work without t'other. But if I had to choose, I'd take chain without the anchor - if I lay out enough it will do the job.

[Lodesman]

Originally Posted by Kim Klaka

There is also a Youtube video of a joint presentation Richard and I did last year,

Thanks for posting that - very interesting. Curious that you showed for most of our anchoring chain is the better performer, yet you're advocating all-rope rode? How do you envision joining the different ropes?

[hpeer]

I am in the heavy anchor school. I think about this piece wize.

First what is the max pull you want to be able to withstand? Assume your chain is attached to a huge mooring, what pull is generated based upon max wind and wave conditions. This gives the minimum chain breaking strength and size.

Then look at the holding power of the anchor. Can you get an anchor that can develop sufficient resistance to break the chain? If not then get the biggest anchor you can.

Last get as much of the above defined chain as you can and if still not 200’ the add rode to get to 200’. Even 200’ may not be enough so adjust upwards if your depth requires.

Every time I anchor I put down the best anchor I can. All the extra chain does me no good if stored. The worst anchoring situation is in a tight anchorage where your scope is limited by swing room, long chain does no good, big anchor does.

[barnakiel]

I think at a point he says his x times oversized Rocna did not stop his boat from placing her tail into rocks???


How come. Was it because it was a Rocna, or rather because it was oversized?


;-)
b.

[waterman46]

Originally Posted by DocHolliday

As a practical matter, the chain / cable / wire / rope becomes roughly "straight", but according to the math and physics, a flexible horizontal element always follows a catenary, however flat. That's because gravity always is pulling the element downward....there are equations to calc a cathenary with applied linear force.

Exactly. You simply cannot pull any anchor chain "straight", it's physically impossible and the chain will break before you get there. Now back to reality, any small improvement in angle of pull on the anchor shank, is very important to increasing the holding capability of the anchor. So even if you don't get any chain lying on the bottom horizontally, the heavier chain will be helpful in keeping a lower angle of pull.

[waterman46]

Originally Posted by Chotu

Including the catenary is a mistake.

Catenary is at maximum with no wind or current.

When you need the anchor to really work, the catenary is almost zero.

But that "almost" is quite important because it reduces the angle of pull on the anchor - I believe most anchors are quite sensitive to the angle of pull applied at the shank. Even a few degrees must make a difference.

[OneKoolCat]

Kim,

Thanks for posting the talk. I was able to better see the points being made.

Near my area is a town on a peninsula called Marblehead, MA, USA. As my dad used to say when I finally got something he was trying to explain. "Light dawns on Marble head."

Cheers,
Peter

[Pete7]

Originally Posted by boatman61

.. Anchor and rope sucks. That's assuming your not saying just chuck the unattached anchor over the bow..

Like you might equip a race boat with then use if you have been racing all day and just want to go ashore and have a quiet night cap drinking past 4am perhaps?

I would suggest he is lecturing to the converted if members of CF are the target audience. Still brave to put your head above the parapet and make a video on anchoring

[jo_sail]

I perfectly agree: In the peak load situation,

When you need the anchor to really work, the catenary is almost zero.

It‘s the movement which puts dynamic peak loads via a straight chain on the anchor and the ground in front of it.

Thus these are my thoughts, when I anchor:

• limit peak loads by
  • limiting especially vertical movement. It has the highest potential for dynamic peak loads, proportional to the displacement of the heavy boat by water, therefore seek shelter from swell and waves,
  • limiting horizontal movements, decrease wind resistance in the front of the boat, use second anchor in the back, some canvas in the back, avoid gusty spots, etc.
  • limiting peak load on anchor by elasticity of the conection from boat to anchor, nylon rope section, snubber, (the weight of the chain and putting additional weight on the chain has quite limited effect in dynamic peak load situations, although the effect increases with larger hight difference and chain length)

• maximise ground holding by

• • selecting good holding ground and careful (at best very slow) digging in of the anchor,
  • maximise ground holding by small angle between anchor shaft and seaflore, I think of this like this:
    "Mmaximise the amount of ground in front of the fluke of your anchor" and
    "An angle of perhaps 40 degree between fluke and anchor shaft means that a about 33 degree of it are effectivly backed by ground material. Then already a lift of the anchor shaft by 10 degree (= scope 6:1 in case of flat seafloor) causes a loss of 30% of the holding capacity of the anchor"
    
  • avoid inclined seafloor or use it so that floor is rising towards the boat by reversing the boat with a fixed landline
    
  • use large scope chain length/depth to limit the angle between anchor shaft and seafloor in case of a streight chain, best < 10 degree, scope > 6:1
    
• wind energy and forces increase with the square of wind speed, so at least some scaling with the wind speed should be accounted
• the forces of the boat movement work on the chain as a lever, which is related to the boat length and the turning point of movements, which is somewhere close to the mast and keel. We can limit the effect of the lever of the boat length by a minimum scope between boat length and chain length.
  Let's say the turning point is 40% of the boat length from the bow. Then a minimum of two boat length of chain forward from the bow makes up for a reasonable scope of 6:1.
  

The last three bullet points lead me to following rules of thumb:

• minimum chain lenght = 2 x boat length
• scale scope with the wind speed:
  depth of anchor from bow (in meters) x max. windforce (in beaufort)

These are useful and very simple for the usual case of smal boat anchoring.



Significan depth of ancoring and length of chain allow for some additional relaxation. With chain length larger then 4 x boat length the scope could slowly approximate 3:1, which is stated in literature for large ships and depth


In conclusion, the following picture can be drawn, to illustrate this thinking for the case of a flat seaflore:

https://www.skipperguide.de/mediawik...9_10_20_EN.pdf


Additionally, if the seaflor is inclined towards the boat, the scope should be increased proportionally, i.e.

• increase scope by 1 for about 1.5 degree of inclination at the position of the anchor

For me this little story in the head allows to find a very reasonable solution for my decision on how to anchor and a good night sleeping with addition of some automated position alarm, set to limits not around the anchor position but around the current boat position. Thus I get an alarm, when the wind, current or swell is significantly changing direction.



The biggest unknown is the ground property for holding the anchor, i.e. for passing the load from the fluke into the ground in front of it. This can be tested to some degree after the anchor has set properly with the motor in reverse.


Additional explanation and discussion in German is available in the wiki skipperguide.



I hope this storyline is helpful for the discussion an I'm happy to discuss it with you.


Cheers Jo

[boatman61]

Originally Posted by Pete7

Like you might equip a race boat with then use if you have been racing all day and just want to go ashore and have a quiet night cap drinking past 4am perhaps?

I would suggest he is lecturing to the converted if members of CF are the target audience. Still brave to put your head above the parapet and make a video on anchoring

Longjonsilver made the video.???
As for racing boats.. most I knew stripped everything outa the boat the night before race day including anchors..

[Lodesman]

Originally Posted by boatman61

Longjonsilver made the video.???
As for racing boats.. most I knew stripped everything outa the boat the night before race day including anchors..

Actually he took a still from the video and superimposed a graphic representation of your anchoring formula. I quite like your method as it ensures a sufficient amount of the anchor system regardless of water depth. If you look at MikeO's graphic it should be obvious that all the other methods tend to under-scope in shallow water and over-scope in deep. From Longjohn's pic, you can see that your line (bright green) has loads of potential energy-absorption in the chain that is lying on the seabed. The inappropriately named "ideal catenary" (red line) should be called "minimum effective catenary for the conditions" as any further applied force will lift the anchor shank from the horizontal.