Anchor Scope

Kelly E, Lighter chain allows the anchor to set better - that's why oil rigs use wire or dyneema - the chain retards anchor setting. Same with any diving, 21st Century, leisure anchor - thinner rode, better setting. That's also why anchors have thin shanks, better setting. That's also why anchors have steamlined shanks (well some of them) better setting. The fluke needs to 'pull down' the shank and the chain - smaller + thinner = better diving anchor. And despite rumours to the contrary many people still think its the anchor that holds the yacht in position (not the chain).

So modern good, anchor, plus slightly (enough length) undersize chain, plus a really decent snubber (a small one and a big one) - way to go! Enough chain? 70m of undersize?

Jonathan
 
GHA said:
Or another route, same weight overall, go down to 100m of 8mm g70 hi tensile & 40m anchor. Would a 40kg anchor with chain about 4deg off seabed hold better than 20kg anchor with chain just touching?
I certainly hate having all the chain out and relying on just nylon. 100m would be nice. As would being able to afford it :)
Click to expand...

Depends whether the 20kg anchor is a Fortress.
Sometimes it's not the weight f the anchor that matters, so much as the weight of mud that has to move with it.
 
I think it a sensible suggestion that a thin, minimum resistance connection between the anchor and chain would help the anchor bury.

The greatest help would be in weed where the weed can lift up the chain and and prevent the anchor obtaining the right angle of attack. Effectively causing the rode angle to mimic a short scope.
A thin strop a few feet long would be beneficial.

Unfortunattly the practicalities make implementation difficult. A short link of titanium wire or dynema has been suggested, but not many are happy trusting their boat to such an untried system. Also few boats (except cats) have sufficient distance between the winch and anchor.

Perhaps the take home message is that the use of bulky swivels and shackles should be minimised where possible.
 
Last edited:
lw395 and Noelex,

Both spot on. A fat chain will discourage setting more than a thin chain. The differences will be greater in hard, pebbly or weedy seabeds. Not an issue with Delta and CQRs = they do not dive (so everything is on the seabed).

I posted the comment as there is a suggestion one wants a heavier rode. I'm not in favour. But the heavier chain in addition to not helping in stronger winds (when you need all the help you can get) is actually going to make it even more difficult for your anchor to set in weed, a hard or pebbly seabed.

And if you do not believe it, bury a bit of chain and a bit of wire in hard sand (firm up the sand). Guess which is easier to pull out.

For a well set anchor the chain is almost horizontal - its a lot of chain to bury, especially if its beefy.

I'm not suggesting a wire strop, or not yet, nor a short piece of G70 - but if you have a swivel (another thing I'm not keen on - but everyone to their own:) ) you have multiple connections and another fat thing hindering the setting of the anchor and you should have a spacer between anchor and swivel - seems that the spacer could be replaced with thinner G70 chain or a consumable wire strop (say replace annually).

And as Noelex says - do not forget the snubber (I find them notable by their absence in every anchorage).

Jonathan
 
>Lighter chain allows the anchor to set better - that's why oil rigs use wire or dyneema - the chain retards anchor setting. Same with any diving, 21st Century, leisure anchor - thinner rode, better setting. That's also why anchors have thin shanks, better setting. That's also why anchors have steamlined shanks (well some of them) better setting. The fluke needs to 'pull down' the shank and the chain - smaller + thinner = better diving anchor.

Well I'm anchoring a boat not an oil rig and I hope nobody ever anchors behind you.
 
pmyatt said:
Well guys, it's been interesting but I'm now thoroughly confused - so will stick with my 27 kg Manson and 75 m of 10 mm chain on our 38 ft boat.
Click to expand...

Plus a 10kg fortress and some string for an easy life when you're only stopping for lunch in the sunshine?
 
kelly, Luddites rule:)

Open your mind to new ideas, open your mind to developments in the real world. They might not all stand the test of time but some of them have proven to work.

Just think about the Bruce anchor?

But I am sure you are correct, we only sail about 2,000nm-3,000nm per year (for the last 12 years), and we only make such trips for part of the year maybe 3-5 months and sometimes we overnight sail, guessing around 100/150 night at anchor + the occasional day trips, - so possibly our anchoring skills might need your expertise.

Jonathan
 
Neeves said:
kelly, Luddites rule:)

Open your mind to new ideas, open your mind to developments in the real world. They might not all stand the test of time but some of them have proven to work.

Just think about the Bruce anchor?

But I am sure you are correct, we only sail about 2,000nm-3,000nm per year (for the last 12 years), and we only make such trips for part of the year maybe 3-5 months and sometimes we overnight sail, guessing around 100/150 night at anchor + the occasional day trips, - so possibly our anchoring skills might need your expertise.

Jonathan
Click to expand...

I think any perceived antagonism is because people don't like being preached at.

As far as your anchoring experience is concerned - don't get into a pissing competition - you will never win.

More seriously, you mention Bruce anchors. Is that because you think they are good, or bad? (It's what I mostly use).
 
NormanS said:
I think any perceived antagonism is because people don't like being preached at.

As far as your anchoring experience is concerned - don't get into a pissing competition - you will never win.

More seriously, you mention Bruce anchors. Is that because you think they are good, or bad? (It's what I mostly use).
Click to expand...

I should not react by provocation, I know, but I'm weak:) I never thought that I was in any way suited to religious fervour, obviously wrong!

I was not endorsing (or not) a Bruce anchor it was simply quoted as coming from the oil rig industry - seemed apt to include it.

But

I always thought a Bruce anchor to be a bit of a waste of time and then I actually used one (actually 2 - both copies, Lewmar's Claw and Manson's Ray), properly, and was suitably impressed. Its very good in soft sand and mud (probably as good as anything else) but it tends to have a blunt toe and if you try to use it in hard seabed or in a seabed with rocks or pebbles then its not quite as good (and other anchors have a more universal application). If I had one and anchored in sand and mud I would stick with it (and not be tempted by the hype). They swivel well when you change the direction of load (tide, wind) and if you force them to sommersault they seem to do so cleanly and reset (all by themselves). There is a suggestion that bigger ones work better (which might be logical for the hard seabeds) but as bigger was expressed as 50kg I have not tried! Peter Bruce knew what he was doing (as you can tell from the success of the company) - its a pity he moved out of the leisure anchor business, bigger fish to fry I guess, but our loss.

Jonathan

PS Thanks for the advise, but I'll probably forget:)
 
Last edited:
Mine is a real 20kg Bruce, not a copy, and I am very satisfied with it. Indeed, my boat is lying to it just now, in North Uist, and I'm not there, and it's probably blowing a hoolie. Actually I have rigged a Bahamian moor with the Bruce and a Fortress, in a well-sheltered sealoch, with good holding.

The real Bruce has quite a sharp toe. I have seen copies which were quite blunt. The only problem that I have ever had was a couple of times when I didn't think it was holding, and pulled it up, to find that it was clutching a large boulder to its bosom. That's what comes of anchoring in places which are definitely not recommended.
 
KellysEye said:
Well I'm anchoring a boat not an oil rig and I hope nobody ever anchors behind you.
Click to expand...

In the interests of science, and furthering our knowledge of anchoring, I want to see Neeves anchor in front of KellysEye sans anchor, relying on the holding power of his chain alone. :D
 
noelex said:
In the interests of science, and furthering our knowledge of anchoring, I want to see Neeves anchor in front of KellysEye sans anchor, relying on the holding power of his chain alone. :D
Click to expand...

I am planning to video ourselves lying to chain only in the next couple of weeks. At the moment my boat's windows are in Athens so we are marina-bound. I don't suppose that KE will be participating but he is most welcome to come and witness.
 
Neeves said:
Kelly E, Lighter chain allows the anchor to set better - that's why oil rigs use wire or dyneema -
Click to expand...

Are you sure about this? I thought that they used wire / dyneema for weight saving in deeper water because they cannot physically carry or haul long chain. The rope was brought in as seawater depths increased because of handling constraints due to weight of steel. I may be wrong, I have very little experience of this.
 
You must log in or register to reply here.

Other threads that may be of interest

B
Help to test new Anchor App on Android
Replies
1
Views
956
Brendan01
B
Y
The Seafarer 700 and NASA clipper sounders saga
Replies
10
Views
440
Dellquay13
Dellquay13

Share this page

Top