Angel weight

[noelex]

The diagram shows what happens to the rode in light wind.
In light wind you should not be worried about dragging.

In winds where the holding power of the anchor becomes of concern the benefits of the angel are very marginal.

 

[[2574]]

The diagram shows what happens to the rode in light wind.
In light wind you should not be worried about dragging.

In winds where the holding power of the anchor becomes of concern the benefits of the angel are very marginal.

Succinctly put; I rather wish I could have been so concise!

 

[Rigger Mortice]

A 30kg chum is roughly the same weight as 20 metres of 8mm chain. I know that they are not the same thing, but I doubt that anyone would say there is no difference if you replace 20metres of chain with 20metres of rope.

FWIW I doubt that many of us have anchored in conditions in which our lines have been bar tight (ie. effectively straight) all the way down to the sea bed.

 

[[2574]]

A 30kg chum is roughly the same weight as 20 metres of 8mm chain. I know that they are not the same thing, but I doubt that anyone would say there is no difference if you replace 20metres of chain with 20metres of rope.

FWIW I doubt that many of us have anchored in conditions in which our lines have been bar tight (ie. effectively straight) all the way down to the sea bed.

There is no difference in 30kts of wind; there is a significant difference in 10kts of wind; that's the point that I'm trying (badly!) to make. (Aside from the other benefits of chain over rope i.e. abrasion resistance etc)

 

[Deleted member 36384]

... In winds where the holding power of the anchor becomes of concern the benefits of the angel are very marginal.

I can conclude that from reading the article.

 

[vyv_cox]

FWIW I doubt that many of us have anchored in conditions in which our lines have been bar tight (ie. effectively straight) all the way down to the sea bed.

Not bar tight, which as has been said earlier, is virtually impossible. But in winds of 30+ knots I have seen all of my chain off the bottom, in a shallow curve, load acting directly on the anchor shank which was clearly moving vertically by a small amount. This was in a very shallow anchorage, depth around 2 - 2.5 metres, with about 35 metres of 8 mm chain out.

 

[jdc]

A little hard?

Any mathematician will tell you it has to be infinitely windy for the rode to be actually straight.
This is Practical boat odour.
I tried it, it helped.
If you prefer the flawed theoretical thoughts of a purveyor of flawed anchors.....

I think you're being a little hard on Peter Smith! In my opinion he has offered us one of the few genuinely novel perspectives on what counts when anchoring. I don't actually agree with him entirely, but it is a thought provoking perspective.

The maths offered by Peter and Alain F (and in a not-too-well received piece by me some time ago) is all the same, as it jolly well should be; all being based on the established physics of catenaries. The conclusion from Peter S is that the geometric effect of the catenary - ie that the pull at the anchor is horizontal - is nugatory for small yachts once winds get really strong. And he does have supporters, including Vyv, who have made direct observation of this. On the other hand there are equally experienced people who argue that a catenary must help make the angle at the anchor ('angulation' in Alain Freysse's articles) more nearly horizontal, and if one lets out enough it will be horizontal even in v. strong winds.

I have concluded that both are right! It's yet another example of how things do not scale linearly(1). Imho Peter S is indubitably correct that the chain's weight does little for small boats and you are better off with an anchor which can tolerate a pull which is not that horizontal (an excellent example of which he designed), plus some stretch in the rode.

However as he himself acknowledges big ships do rely on the catenary. Why is this? It's because the weight of the chain a boat can carry is more or less proportional to the weight of the boat, so length cubed, whereas the forces go with the cross sectional area, so length squared. This means that as a boat gets bigger the force rises slower than the weight of chain it can carry. Where is the cross-over? Around 40' or 15 tons displacement I think - right in the middle of members of this forum's experiences!

Back to the OP's boat, it's in the domain when the weight it's practical to carry will make only a modest difference to ultimate anchoring security, although of course it does have the other advantages several have described above.

(1) the 'square-cube' law is of extraordinary importance in our world. It explains why beetles can't be the size of elephants, and why mice can fall from tall buildings with impunity but horses would smash to pulp. It applies to anchoring, and to engine HP...

 

[lw395]

I think you're being a little hard on Peter Smith! In my opinion he has offered us one of the few genuinely novel perspectives on what counts when anchoring. I don't actually agree with him entirely, but it is a thought provoking perspective.

The maths offered by Peter and Alain F (and in a not-too-well received piece by me some time ago) is all the same, as it jolly well should be; all being based on the established physics of catenaries. The conclusion from Peter S is that the geometric effect of the catenary - ie that the pull at the anchor is horizontal - is nugatory for small yachts once winds get really strong. And he does have supporters, including Vyv, who have made direct observation of this. On the other hand there are equally experienced people who argue that a catenary must help make the angle at the anchor ('angulation' in Alain Freysse's articles) more nearly horizontal, and if one lets out enough it will be horizontal even in v. strong winds.

I have concluded that both are right! It's yet another example of how things do not scale linearly. Imho Peter S is indubitably correct that the chain's weight does little for small boats and you are better off with an anchor which can tolerate a pull which is not that horizontal (an excellent example of which he designed), plus some stretch in the rode.

However as he himself acknowledges big ships do rely on the catenary. Why is this? It's because the weight of the chain a boat can carry is more or less proportional to the weight of the boat, so length cubed, whereas the forces go with the cross sectional area, so length squared. This means that as a boat gets bigger the force rises slower than the weight of chain it can carry. Where is the cross-over? Around 40' or 15 tons displacement I think - right in the middle of members of this forum's experiences!

Back to the OP's boat, it's in the domain when the weight it's practical to carry will make only a modest difference to ultimate anchoring security, although of course it does have the other advantages several have described above.

Some fair comment in there, but most of the maths and graphs etc I've seen published relate to a steady state condition, with no waves.
Put some waves into the system and a weight near the boat end of the rode does a great deal to keep the load on the anchor more constant.

Ships also operate in a different regime, they generally anchor where they are longer than the waves they are anchored in.

In my circumstances, it was much cheaper and easier to gather 10 or 15 kgs of scrap lead and see what happen than upgrade the 'minimum RORC' anchor to one I couldn't lift...
Also being an occasional racer, I don't like carrying vast amounts of chain in the bow.
It's something I'm very glad I tried, and I find simplistic explanations of why it can never work a little tiresome, as I know it can be very useful in many common situations.

 

[Rigger Mortice]

I think that that Peter Smith article is just his usual flannel.
He talks about the maths, but he never shows his calculations.
He makes a case for not using all chain warps, recommends chain and rope, but appears to use all chain himself.

 

[PabloPicasso]

The conclusion from Peter S is that the geometric effect of the catenary - ie that the pull at the anchor is horizontal - is nugatory for small yachts once winds get really strong. And he does have supporters, including Vyv, who have made direct observation of this.

I have concluded that both are right! It's yet another example of how things do not scale linearly(1). Imho Peter S is indubitably correct that the chain's weight does little for small boats and you are better off with an anchor which can tolerate a pull which is not that horizontal (an excellent example of which he designed), plus some stretch in the rode.

However as he himself acknowledges big ships do rely on the catenary. Why is this? It's because the weight of the chain a boat can carry is more or less proportional to the weight of the boat, so length cubed, whereas the forces go with the cross sectional area, so length squared. This means that as a boat gets bigger the force rises slower than the weight of chain it can carry. Where is the cross-over? Around 40' or 15 tons displacement I think - right in the middle of members of this forum's experiences!

[/QUOTE]

So I could forget about an anchor chum/angel/weight on my 26footer then?

 

[noelex]

He makes a case for not using all chain warps, recommends chain and rope, but appears to use all chain himself.

Chain has other advantages. The primary one is abrasion resistance.
Many serious cruising sailors feel it essential for this feature alone.

Dashew who was an early supporter of the view that rode weight makes little difference (or at least the weight is better applied to the anchor) use as light weight chain as possible (G7), but stay with chain for its other attributes. I suspect (but don't know) that Peter Smith does the same.

 

[lw395]

So I could forget about an anchor chum/angel/weight on my 26footer then?

You're free to forget about if you like, but sometimes it's a handy tool to have in the box.
A lump of lead that lives under the cabin sole 360-odd days of the year may make your life easier one day.
But I don't claim t will let you ride out a hurricane on a counterfeit Danforth and a short scope.
I tried it because both my boats were ex-racers with 'light' anchors and short chains, and both had issues with behaviour compared to other yachts in an anchorage, and on occasion, dragging.
If you don't have the problem, you're free to ignore solutions to it.

 

[vyv_cox]

Chain has other advantages. The primary one is abrasion resistance.
Many serious cruising sailors feel it essential for this feature alone.

Dashew who was an early supporter of the view that rode weight makes little difference (or at least the weight is better applied to the anchor) use as light weight chain as possible (G7), but stay with chain for its other attributes. I suspect (but don't know) that Peter Smith does the same.

Alain Poireaud (inventor of the Spade) was one who wrote strongly supporting the Alain Fraysse calcs showing that chain weight contributed very little. He did as he wrote - had 20 metres of chain for its abrasion resistance but all the rest of the rode was rope, 8-plait I believe. He sailed a Hylas 46 to some very inhospitable places, e.g. anchoring for long periods in the Magellan Strait.