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

[UFO]

Thought I'd throw the cat among the pigeons on a slow day


"The traditional chain scope calculation, using a simple multiplier, is not correct due to the curvature of the chain. 15m (50ft) plus double the depth is better calculation. But always put out more chain in challenging conditions."

https://www.youtube.com/watch?v=FOKVO3JBgDY

[Tin Tin]

So in 10ft of water we normally put out 100ft of chain and for us that equals 100/(10+6) = scope of 6.25


Your guy says 50+(2*10) = 70ft = scope of 70/16=4.3


If you were to use the 5 times rule of thumb that would be 5 * 16 = 80ft


It depends on whether you include the height of anchor above the water, which in our case was 6ft - makes quite a difference.


What he is saying is just common sense, "you need to edit the numbers to suit your boat" (and by implication the anchor)

[UFO]

Originally Posted by Tin Tin

So in 10ft of water we normally put out 100ft of chain and for us that equals 100/(10+6) = scope of 6.25


Your guy says 50+(2*10) = 70ft = scope of 70/16=4.3


If you were to use the 5 times rule of thumb that would be 5 * 16 = 80ft


It depends on whether you include the height of anchor above the water, which in our case was 6ft - makes quite a difference.


What he is saying is just common sense, "you need to edit the numbers to suit your boat" (and by implication the anchor)

Hey Less of the Your Guy, I'm just here for the show
But I normally go in benign conditions with 5:1 with the depth calculated from the bow roller

[Pete7]

Surely if there is a nice big curve in the chain, then conditions are calm and you could probably hold on nothing more than a car tyre.

I think using 4 or 5 times the depth is just easier to remember and use.

I note he was talking about a group of boats used for club racing I think. Were they carrying less than optimal anchors and chain perhaps?

[longjonsilver]

His formula puts into linear form something to approximate the caternary. Personally i think that this makes a lot of sense. He said exactly what i believe - that we need to upsize our anchors over the factory recommendations. Put your weight in the anchor. However what he didn't say is that the chain is the poorest use of the weight - lighter chain and heavier anchor is my belief....
jon

[boatman61]

Bugga all that malarkey... 3 x LOA + depth..

[Pegu Club]

As an example of an anchoring situation;

In the past week a front with strong winds for a considerable period of time that was forecasted well in advance by Chris Parker amongst others, for Florida and the Bahamas, it is now being stated on the webs, by some that it wasn’t forecasted..., this is an example of folk not accessing the best weather information that is commonly available, weather forecasts are very important tool/component of where to and how to anchor ones boat. When ever one can, getting to the best available anchorage a day or two in advance of a known and well forecasted front such as this one is very important, for obvious enough reasons, one being that ones anchor has the opportunity to become well set, reducing the odds of dragging noticeably, it appears in this example, some folk showed up just hours before the front hit limiting their anchoring location, and scope options, and some indeed dragged, and complained later that the front was not forecasted. Again this is brought up to emphasize that being in place well before a well forecasted front arrives is a big part of anchoring success, on top of the normal anchor and scope considerations. There are as we all know many theories on best practices when it comes to the act of anchoring ones boat, and circumstances can be such that one finds themselves in a less than ideal situation, but in this case much of the angst seen on the web pages was of folks own making...,

Fair winds,

[Mike OReilly]

Kinda amusing that he states: "But always put out more chain in challenging conditions." In unchallenging conditions most boats will sit on their chain. Certainly any decent anchor and chain will hold in unchallenging conditions.

To me, the whole point of anchoring correctly is to remain in place during challenging conditions.

Here's a simple graph showing the slopes of the different approaches. In the depths most of us anchor in most of the time the differences are not great. As one gets out into deeper waters the impacts become more pronounced.

This seems to mirror real-world experience and wisdom that deep-water anchoring requires less scope if using all-chain.

[longjonsilver]

Originally Posted by boatman61

Bugga all that malarkey... 3 x LOA + depth..

So here is the curve that you are recommending for a 40'boat (in green):



enjoy

jon

[longjonsilver]

Originally Posted by Mike OReilly

Here's a simple graph showing the slopes of the different approaches.

But you have neglected to show the horizontal part of the curve - 50 feet or 3x boat length - see my graph above

jon

[boatman61]

Originally Posted by longjonsilver

So here is the curve that you are recommending for a 40'boat (in green):



enjoy

jon

On a calm day yes, well it would be more vertical but, throw in a bit of wind and watch it change..
But.. a 40ft boat would be 120ft of chain plus depth.
However, I don't look for curve, I leave that to theoretical statisticians.. I just want my boat to stay put..
Enjoy.

[longjonsilver]

Originally Posted by boatman61

However, I don't look for curve, I leave that to theoretical statisticians.. I just want my boat to stay put..
Enjoy.

i just drew what you stated for a 40' boat. 3 times boat length plus depth. Just to show how it compares to that of MacFarlane.

jon

[boatman61]

Originally Posted by longjonsilver

i just drew what you stated for a 40' boat. 3 times boat length plus depth. Just to show how it compares to that of MacFarlane.

jon

I thought that was a freeze from a YouTube video..
Hard to make out detail on a mobile phone..

[Pete7]

Originally Posted by longjonsilver

He said exactly what i believe - that we need to upsize our anchors over the factory recommendations. Put your weight in the anchor.

I have been watching Steve Goodwin's videos on anchors setting as I suspect have many with interest. What I was interested in is not the absolute holding power, but the holding achieved in average conditions that he was able to replicate pull after pull. As he noted in one review of a 10kg Rocna that the holding power is approaching the load a 30ft yacht would see in a TS, if this was an appropriate size of anchor. Rocna size the anchor for 50 knots of wind, that will do for me, but happy to accept others might want larger for a particular reason, a cat for example.

Originally Posted by longjonsilver

However what he didn't say is that the chain is the poorest use of the weight - lighter chain and heavier anchor is my belief.... jon

Did he say he was alone at 4am on his boat with the crew ashore . Then followed it up with a statement that the wind never got over 25 knots and that most boats didn't drag. So what's the problem? A few race boats with too small an anchor or not enough scope ended up on the beach in 25 knots of wind. Oh dear, should have read the booklet that anchors like Rocna and Fortress come with.


Pete

[Mike OReilly]

Originally Posted by longjonsilver

But you have neglected to show the horizontal part of the curve - 50 feet or 3x boat length - see my graph above

jon

I wasn't trying to show how the rode will lay out, just the simple rode length result from the different approachs.

The horizontal component in each situation will vary based on the angle of the rode.