Cerebus
N/A
missed the quote
How long anchor rope/rode for UK inshore wandering?
- Thread starter mikefleetwood
- Start date
Cerebus
N/A
I use the formula 12 x the square root of the depth. If you needed to anchor in 25 m then the square root is 5, then times 12 equals 60 m. That is the amount of chain I carry.
Often good to be over cautious, but what happened to 1:4 ratio for chain (although Google states 1:5)?
Never heard of the square root method but there is a lot I am daft about.
Dockhead
Well-Known Member
You don't need more than 7:1 with all chain; there is very little to gain going any further than that. 5:1 is enough if you have a good anchor and conditions are not terrible. Bit more scope with chain/rope is better. It also depends on your anchor; with a bigger anchor you can use somewhat less scope. To anchor in 15m of water, you will certainly want at least 100m total rode length if it's chain/rope.
To answer your original question, I have 100m of 12mm chain, but I'm a 54' boat drawing 2.35m (also a Moody BTW), so I'm often in deep water. In a boat like yours, I would think 100m of rope and 20m of chain would be plenty.
I would not advise using nylon for the rope part. I suggest reading what Dashew says about that: https://www.petersmith.net.nz/boat-anchors/docs/dashew-right-rode.pdf. You want octoplait, not three-strand, and polyester, not nylon, in my opinion.
Sumara of Weymouth
Well-Known Member
The necessary ratio alters with the depth, you need a higher ratio in shallow waters less in deep water. The square root formula sorts that out.
webcraft
Well-Known Member
When people talk about 'anchoring in 5m' (for example) are they talking about charted depth? High water depth? Indicated depth?
You need to know the actual depth at HW before you can apply a formula.
I am not convinced everyone is talking about the same thing.
I usually look for 4x HW depth (all chain) so if I anchor in 2m indicated depth at LW Springs on the W coast I typivally calculate 2m + 1.3m keel offset plus 3.5m tidal range + a bit for luck, so although I am only in 2m indicated depth when I drop the hook I pay out 30m of chain.
- W
You need to know the actual depth at HW before you can apply a formula.
I am not convinced everyone is talking about the same thing.
I usually look for 4x HW depth (all chain) so if I anchor in 2m indicated depth at LW Springs on the W coast I typivally calculate 2m + 1.3m keel offset plus 3.5m tidal range + a bit for luck, so although I am only in 2m indicated depth when I drop the hook I pay out 30m of chain.
- W
mikefleetwood
Well-Known Member
Many thanks for all your replies - much food for thought here! Pretty much each person with a different experience/solution (but all useful).
To address some comments:
Yes, when I talked about "5-15m", I was thinking of charted depths. Round here, the tidal height varies from about 4m neap (such as today) to 6m spring. So, if anchoring in 15m (charted), I would need to allow for about 19-21m at high tide.
The nylon vs polyester point was interesting. The examples cited were extreme conditions, the like of which I have no intention of being anywhere near! I understood that Nylon was supposed to be better because of it's elasticity and because it sinks, rather than floats like many synthetic ropes - does polyester sink or float?
I'm a bit wary of octoplait or braided ropes, because I don't see how to successfully splice to the anchor chain (which is quite straightforward with 3-strand).
Someone said that 16mm was heavier than needed for a 29 foot boat, but in view of the reported problem with nylon under repeated loads - maybe better to err on the side of caution?
I don't have a winch, so it will all have to be hauled by hand
I think my options are:
100+20m - 120m, so maximum about 30m at 4:1 - so OK for pretty much anywhere I might want to anchor
I'm sure there are others!
To address some comments:
Yes, when I talked about "5-15m", I was thinking of charted depths. Round here, the tidal height varies from about 4m neap (such as today) to 6m spring. So, if anchoring in 15m (charted), I would need to allow for about 19-21m at high tide.
The nylon vs polyester point was interesting. The examples cited were extreme conditions, the like of which I have no intention of being anywhere near! I understood that Nylon was supposed to be better because of it's elasticity and because it sinks, rather than floats like many synthetic ropes - does polyester sink or float?
I'm a bit wary of octoplait or braided ropes, because I don't see how to successfully splice to the anchor chain (which is quite straightforward with 3-strand).
Someone said that 16mm was heavier than needed for a 29 foot boat, but in view of the reported problem with nylon under repeated loads - maybe better to err on the side of caution?
I don't have a winch, so it will all have to be hauled by hand
I think my options are:
- Add the 40m length of 16mm nylon to the existing 20m chain (by far the cheapest/simplest option).
- Buy 100m of 16/14mm? nylon and add to the 20m chain.
- Buy 100m of something else (polyester) and add it to the chain.
- Relegate the chain to "spare" and buy 100m of new chain.
100+20m - 120m, so maximum about 30m at 4:1 - so OK for pretty much anywhere I might want to anchor
I'm sure there are others!
Cerebus
N/A
Go for option 4 in my opinion.
Get a windlass if you can too, unless young and fit as I w once was.
Tranona
Well-Known Member
You don't say what size chain you have, but splicing anchorplait onto the correct size chain/rope is not difficult - the rope was designed for just that. 6mm chain is what you need for your size boat if you have all chain but for mixed rode you could go up to 8mm to get the advantage of the greater catenary in shallow water. Rope should be 12mm (definitely not 16mm) 3 strand polyester or anchorplait definitely not nylon. The advantage of nylon is that it stretches to absorb snatch loads, but in continual use it hardens and loses strength - worse when full of salt. So best used as a snubber rather than a permanent rode. If you do go mixed rode then 20m of 8mm and 50m of 12mm rope is a good balance. As others have suggested around the UK you rarely need more than 40 or in some areas such as the CIs 50 or 60 If you do not have a windlass there is no need to splice but use a shackle and eye or the rope. The downside of splices is that they do not like sitting in the wet bottom of the locker with a pile of chain on top so may need redoing every couple of years because of a build up of rust in the terminal links.
dunedin
Well-Known Member
I am sure your option 4 was somewhat tongue in cheek - but you need a much bigger scope with rope than chain, so 60m of chain would probably be more effective than 20mm chain plus 80m rope.
A better option 4 might be replacing the 20m of chain with 30 to 40m. Moderate lengths of chain like these are often available secondhand - I sold 35m almost new chain earlier this year, for example,
Dockhead
Well-Known Member
My experience agrees with you, and I personally use more scope in shallower water. But I'm not sure whether that formula reflects the physics and geometry.
If the wind is strong enough to pull all the catenary out of the chain, then the same scope ratio gives the same chain angle at the anchor at any depth. The only difference is catenary, and the effect of that (and limits of that!) depend on weight of the chain, and how much force is being put on it. So I don't think any single formula is possible.
In deeper water, the catenary in my chain (12mm, weighing 3.3kg/m, so 330kg for the whole length) is so powerful, that I don't even need a snubber, even in quite lively conditions. In water over 15m deep, I don't know and can't imagine how much wind would be required to pull the catenary out.
But this will look very, very different with lighter chain.
Dockhead
Well-Known Member
I personally wouldn't want 100m of chain in the bow of a 29' boat. YMMV.
30m is enough for 6:1 in 5m of water (well, 5m of water plus height of the bow roller), which should allow the OP to anchor on all chain in most cases. Another 100m or 60m of rope will be enough for any unusual situation. Or 40m maybe.
Cerebus
N/A
Fair enough.
Boats can have the chain go through the forward locker and then delve a bit deeper towards the hull.
Anchoring in 5m is great, but what if the only option is deeper water?
I know a skipper that had to anchor in a deep location and had to add every length of line they could acquire including the job sheets!
Not ideal. But not common either.
Porthandbuoy
Well-Known Member
Sheolin carries 50m 3/8" chain attached to a 30+lb Griff CQR lookalike anchor. The chain is spliced to at least another 50m of nylon rope 'just in case'. I've never deployed any rope. Most times I anchor in 5~10m deploying 20m to 40m chain. I will admit it does occasionaly take a couple of goes to set the anchor, usually due to weed, but once set it's pretty solid.
Cerebus
N/A
What areas or locations are you anchoring in with that equipment?
Porthandbuoy
Well-Known Member
Firth of Clyde and Inner Hebrides mostly. Should add I've not yet had the 'pleasure' of riding out a storm at anchor on this boat.
Edit: And I always use a 12mm climbing rope as a snubber. Usually made off on a stern cleat but long enough to go right round the boat and back to the bow using snatch blocks (I do worry the snatch blocks, hefty, tufnol jobs, may be the weakest link).
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Cerebus
N/A
Areas I don’t know so your experiences are trump. Also, kudos in my humble opinion for sailing in areas at latitudes that I and maybe many other consider high.
zoidberg
Well-Known Member
I've had a look at several of the 'night stop' anchorages down South-West that you're likely to consider. There's Starehole Bay outside Salcombe, just north and west a bit from Start Point, behind Mullion Island, Cawsand Bay, and outside Mousehole Harbour... and I can't see you'd have a problem - provided your anchor is 'set' - with your 20m. of chain and, say, 50 m. of rope rode.
You wouldn't choose to hang on at anchor in such pleasant places if the wind and weather deteriorated - and each of those has really good shelter quite close at hand.
As is clear from the many different 'belief systems' above, there are multiple satisfactory ways. Several of those making recommendations have very much larger, heavier boats. Consider whether their choices are likely to be optimum for you and your boat. I'd encourage you to have more than one anchor, more than one chain-and-rope rode, and avoid nylon as it swiftly grows hard, loses strength, and is much heavier/harder to handle once saturated than polyester rope.
Should you buy some octoplait, every chandler I've met in the SW would be pleased to splice in an eye with/without a thimble. I'd prefer to have a length of antichafe slipped onto such an eye/loop and be quite content.
You wouldn't choose to hang on at anchor in such pleasant places if the wind and weather deteriorated - and each of those has really good shelter quite close at hand.
As is clear from the many different 'belief systems' above, there are multiple satisfactory ways. Several of those making recommendations have very much larger, heavier boats. Consider whether their choices are likely to be optimum for you and your boat. I'd encourage you to have more than one anchor, more than one chain-and-rope rode, and avoid nylon as it swiftly grows hard, loses strength, and is much heavier/harder to handle once saturated than polyester rope.
Should you buy some octoplait, every chandler I've met in the SW would be pleased to splice in an eye with/without a thimble. I'd prefer to have a length of antichafe slipped onto such an eye/loop and be quite content.
Cerebus
N/A
What a good post.
Whilst I always carry 3 anchors, as a complete fool I never carried 3 rodes as you have pointed out; how dumb I have been.
I feel a fool.
zoidberg
Well-Known Member
Niet, tovarich!
You'd only be a fool if you didn't respond to the little light bulb.
We all learn stuff from other people. That's what this place - and waterside inns - is for......
Sumara of Weymouth
Well-Known Member
You are probably right regarding the physics and geometry but somehow it does seem to work!