Mirelle
N/A
Has there been a fundamental change, brought on by beamier boats with narrow bows, equipped with light ground tackle and electric windlasses?
anchor scope
- Thread starter Talbot
- Start date
Krusty
New member
Re: RYA (long)
I've read the posts: after all the tantrums, at last I see some discussion on the practical application of physics! The results of 'tests' of holding power of anchors depend as much the test method and nature of the bottom as on the anchors, and the only results that matter are thousands of real-life events.
I once used my own 35lb CQR to arrest, just off the Culbin Sands in the Moray Firth, a 40-ton pontoon which had broken its massive mooring in a December storm: a second anchor was laid for security. More harsh weather followed, and it was a week later, at Springs, before it could be salvaged: it was taken in tow, leaving both anchors. At low water, we found the rodes. The second anchor had taken no load. We dug a trench along the first: the CQR was four feet down, and clearly would have broken the rode or shackle rather than break out.
On 13th June 2000, I lay in E.Weddel Sound, Orkney, on my twin 25lb CQRs through a day of winds gusting 90 knots (Orkney Hr. Radio reported that it never fell below 64kn Hurricane force, for 5 hours) . I became quite twitchy about strength of shackles, but transits confirmed that after the first few feet during the rising wind the anchors never moved in that 5 hours.
It is true: 'It's the chain that holds the boat! -- the anchor just holds the end of the chain! The chain needs weight, and it needs scope: within limits you can trade one for the other. The (12 x square root of Depth) formula is close to the chain catenary, and over the depths in which yachts anchor a practical rule is to pay out (Twice Depth plus 20) --feet or fathoms or metres! Try the sums for depths 4m, 9m, 16m, 25m, 36m! I have used it over a thousand times (literally) and dragged 3 times: each time by my own (identified) fault.
Hope this adds something useful to the sum total of this thread.
I've read the posts: after all the tantrums, at last I see some discussion on the practical application of physics! The results of 'tests' of holding power of anchors depend as much the test method and nature of the bottom as on the anchors, and the only results that matter are thousands of real-life events.
I once used my own 35lb CQR to arrest, just off the Culbin Sands in the Moray Firth, a 40-ton pontoon which had broken its massive mooring in a December storm: a second anchor was laid for security. More harsh weather followed, and it was a week later, at Springs, before it could be salvaged: it was taken in tow, leaving both anchors. At low water, we found the rodes. The second anchor had taken no load. We dug a trench along the first: the CQR was four feet down, and clearly would have broken the rode or shackle rather than break out.
On 13th June 2000, I lay in E.Weddel Sound, Orkney, on my twin 25lb CQRs through a day of winds gusting 90 knots (Orkney Hr. Radio reported that it never fell below 64kn Hurricane force, for 5 hours) . I became quite twitchy about strength of shackles, but transits confirmed that after the first few feet during the rising wind the anchors never moved in that 5 hours.
It is true: 'It's the chain that holds the boat! -- the anchor just holds the end of the chain! The chain needs weight, and it needs scope: within limits you can trade one for the other. The (12 x square root of Depth) formula is close to the chain catenary, and over the depths in which yachts anchor a practical rule is to pay out (Twice Depth plus 20) --feet or fathoms or metres! Try the sums for depths 4m, 9m, 16m, 25m, 36m! I have used it over a thousand times (literally) and dragged 3 times: each time by my own (identified) fault.
Hope this adds something useful to the sum total of this thread.
Ships_Cat
New member
Re: Er, yes...
Many thanks for that Mirelle. I will try some experimenting when we get away later this week as many of our anchorages have heavy, swirling gusty winds - that is if I get away as some work is starting to get in the way (a fast cat, 350 pax new build to look after so not too burdensome, I wonder how we will anchor it /forums/images/graemlins/smile.gif).
Seems like the cat haters are out in force so am abandoning this thread /forums/images/graemlins/crazy.gif.
John
Many thanks for that Mirelle. I will try some experimenting when we get away later this week as many of our anchorages have heavy, swirling gusty winds - that is if I get away as some work is starting to get in the way (a fast cat, 350 pax new build to look after so not too burdensome, I wonder how we will anchor it /forums/images/graemlins/smile.gif).
Seems like the cat haters are out in force so am abandoning this thread /forums/images/graemlins/crazy.gif.
John
Ships_Cat
New member
Re: Disagree. Completely.
Looks like we agree then Micheal, errr well, except for the cat hating bit but that seems to be an affliction you have (I like cats).
For the benefit of others what I set out saying was We would only very rarely use more than 3:1 scope. which led to me being told that it was only luck that I had never dragged ranging on to posts the sense of which were that I did not know what I was talking about, and did I disagree with every other "expert" posters could find quotes from /forums/images/graemlins/crazy.gif. I must be real lucky 'cos we anchor on average more than a 100 times a year in exposed anchorages on bottoms of sand, mud, gravels and rock - perhaps I should take up gambling /forums/images/graemlins/smile.gif.
There has been some challenge in the thread as to my credentials so with the risk of upsetting a few perhaps I can satisfy the challengers with a very tiresome response.
I have sailed and power boated all my life (sailed since around 7-8 years and my earliest memories, maybe at 3 or 4 yrs, are in non sailing boats). Jumping alot of time to more recently, I for many years ran a company which provided safe management services to around 2, 000 vessels (vessels of all sizes up to around 150 foot, but including inshore/coastal passenger, charter yachts/mobos, fishing vessels, big game fishing, etc) and that included reviewing their designs if new, and their in service and construction surveys so employed 35 surveyors for that.
On top of that the company did both non exclusive big ship surveys for some classification societies and also for several flags. I have also done alot of work in aviation (mainly radars, air traffic management, both civil and military) and in telecommunications (the later has proved of much upset to Michael who is convinced that I don't know anything about it /forums/images/graemlins/crazy.gif). I have worked in Europe and N. America (both of those quite frequently off and on), Asia, and, of course Australia and NZ.
I can afford to do pretty much what I want these days by picking and choosing, so as well as some land work (mainly consulting in change management, recovering failing companies and assessment of new business opportunities) on the marine side I do some management of the international design, build and commissioning of high quality vessels, mainly for fleet operators (but also stuff to do with the odd superyacht, etc) for clients as far away as the Atlantic coast of N. America - I am in NZ. Several forumites have seen vessels I have been involved with or have (through their own work in the marine industry) discovered that we know common people.
Strangely, regarding the MainlySteam username, which some also had a hate session over above, it has come back to me from one cat hating forumite that he reckoned that Kim ordered me to reform and change usernames /forums/images/graemlins/crazy.gif. Just goes to show how wild some imaginations are when driven by hate. The reasons were quite different and were set out in the sounding of MainlySteam's Last Post along the lines of being a waste of time giving professionally based advice and comment (as this thread again shows) but in the end a number of forumites actually asked me to continue doing so /forums/images/graemlins/blush.gif.
We currently own a 40 foot cruising sloop that was a custom build for us. It is based on one of the designer's existing and proven designs (to be safe)but in discussions with him, the builder (who also is a repected cruising boat designer) and myself some considerable changes were made to the hydrodynamics and the structure (the structure to reduce weight). It was specified by myself and the builder who is a very experienced yachtsman. Unhappily, and very sadly at the time, the designer never saw it completed. He and his wife were killed in a car crash on their way to see it.
So there you are, that is me, upsetting to some I am sure and they will probably tell me so, but some did challenge my credentials in this thread. If they don't like me perhaps they can find the little button that hides my posts from them. People can discard or take note of of my advice and opinions on boaty matters as they wish but I will point out that they don't know what they are talking about if they set out to mislead others when they are clearly wrong or alternative approaches exist.
In the end my very picky clients pay me quite alot of money for boaty advice so if some forumite thinks I know nothing and my advice is of no value, you will understand that I think it rather a joke.
Whew, that was long. Maybe this thread will become a blog /forums/images/graemlins/smile.gif. You now know more about me than I know about almost all of you (apart from Michael, who I concede, does have a very open and interesting internet site, as do a few other forumites).
As I said above, I won't be around on this thread - don't squabble and fight will you /forums/images/graemlins/smile.gif
John
Looks like we agree then Micheal, errr well, except for the cat hating bit but that seems to be an affliction you have (I like cats).
For the benefit of others what I set out saying was We would only very rarely use more than 3:1 scope. which led to me being told that it was only luck that I had never dragged ranging on to posts the sense of which were that I did not know what I was talking about, and did I disagree with every other "expert" posters could find quotes from /forums/images/graemlins/crazy.gif. I must be real lucky 'cos we anchor on average more than a 100 times a year in exposed anchorages on bottoms of sand, mud, gravels and rock - perhaps I should take up gambling /forums/images/graemlins/smile.gif.
There has been some challenge in the thread as to my credentials so with the risk of upsetting a few perhaps I can satisfy the challengers with a very tiresome response.
I have sailed and power boated all my life (sailed since around 7-8 years and my earliest memories, maybe at 3 or 4 yrs, are in non sailing boats). Jumping alot of time to more recently, I for many years ran a company which provided safe management services to around 2, 000 vessels (vessels of all sizes up to around 150 foot, but including inshore/coastal passenger, charter yachts/mobos, fishing vessels, big game fishing, etc) and that included reviewing their designs if new, and their in service and construction surveys so employed 35 surveyors for that.
On top of that the company did both non exclusive big ship surveys for some classification societies and also for several flags. I have also done alot of work in aviation (mainly radars, air traffic management, both civil and military) and in telecommunications (the later has proved of much upset to Michael who is convinced that I don't know anything about it /forums/images/graemlins/crazy.gif). I have worked in Europe and N. America (both of those quite frequently off and on), Asia, and, of course Australia and NZ.
I can afford to do pretty much what I want these days by picking and choosing, so as well as some land work (mainly consulting in change management, recovering failing companies and assessment of new business opportunities) on the marine side I do some management of the international design, build and commissioning of high quality vessels, mainly for fleet operators (but also stuff to do with the odd superyacht, etc) for clients as far away as the Atlantic coast of N. America - I am in NZ. Several forumites have seen vessels I have been involved with or have (through their own work in the marine industry) discovered that we know common people.
Strangely, regarding the MainlySteam username, which some also had a hate session over above, it has come back to me from one cat hating forumite that he reckoned that Kim ordered me to reform and change usernames /forums/images/graemlins/crazy.gif. Just goes to show how wild some imaginations are when driven by hate. The reasons were quite different and were set out in the sounding of MainlySteam's Last Post along the lines of being a waste of time giving professionally based advice and comment (as this thread again shows) but in the end a number of forumites actually asked me to continue doing so /forums/images/graemlins/blush.gif.
We currently own a 40 foot cruising sloop that was a custom build for us. It is based on one of the designer's existing and proven designs (to be safe)but in discussions with him, the builder (who also is a repected cruising boat designer) and myself some considerable changes were made to the hydrodynamics and the structure (the structure to reduce weight). It was specified by myself and the builder who is a very experienced yachtsman. Unhappily, and very sadly at the time, the designer never saw it completed. He and his wife were killed in a car crash on their way to see it.
So there you are, that is me, upsetting to some I am sure and they will probably tell me so, but some did challenge my credentials in this thread. If they don't like me perhaps they can find the little button that hides my posts from them. People can discard or take note of of my advice and opinions on boaty matters as they wish but I will point out that they don't know what they are talking about if they set out to mislead others when they are clearly wrong or alternative approaches exist.
In the end my very picky clients pay me quite alot of money for boaty advice so if some forumite thinks I know nothing and my advice is of no value, you will understand that I think it rather a joke.
Whew, that was long. Maybe this thread will become a blog /forums/images/graemlins/smile.gif. You now know more about me than I know about almost all of you (apart from Michael, who I concede, does have a very open and interesting internet site, as do a few other forumites).
As I said above, I won't be around on this thread - don't squabble and fight will you /forums/images/graemlins/smile.gif
John
Mirelle
N/A
Yes, it does,
add to the useful part of the discussion, but I don't entirely agree with it!
To save others the trouble of digging out calculators, here are the numbers. I have done them in metres and again in fathoms for people like me who think that way:
4metres - 24 metres of chain. Call that 2.1 fathoms and 13 fathoms of chain /forums/images/graemlins/confused.gif
5 metres - 27 metres of chain / 2.7 fathoms and 15 fathoms of chain
7 metres - 31 metres of chain / 3.8 fathoms and 17 fathoms of chain
9 metres - 36 metres of chain / 5 fathoms and 20 fathoms of chain
10 metres - 38 metres of chain / 5.5 fathoms and 21 fathoms of chain
12 metres - 42 metres of chain / 6.5 fathoms and 23 fathoms of chain
15 metres - 47 metres of chain / 8.2 fathoms and 25 fathoms of chain /forums/images/graemlins/smile.gif
18 metres - 51 metres of chain / 10 fathoms and 28 fathoms of chain
20 metres - 54 metres of chain / 11 fathoms and 30 fathoms of chain
25 metres - 60 metres of chain / 14 fathoms and 32 fathoms of chain
30 metres - 65 metres of chain / 16 fathoms and 36 fathoms of chain.
36 metres - 72 metres of chain
The "shallow" end of the table gives absurd results but then if I were to anchor in 2 fathoms at HW almost anywhere on the UK coast I would dry out at LW!
I do quite often anchor in 4 or 5 fathoms. To pay out 20 fathoms of chain seems excessive, where on the 3:1 formula I would be using 12 or 15. I am of course measuring from the waterline - adding the 5ft (in my case) of sheer to the figure, so that the cable mark is "in the water".
I don't dispute that I would veer another 5 fathoms, and maybe 10, if anchored in 5 in a blow. But in fair weather I see no need to. To veer 15 fathoms in 2.7 fathoms of water is recipe for wandering all over the place and, in the case of many East Coast UK anchorages, drying out on a bank to leeward!
I do have heavy chain. So do the barges and smacks that I have mentioned earlier....
add to the useful part of the discussion, but I don't entirely agree with it!
To save others the trouble of digging out calculators, here are the numbers. I have done them in metres and again in fathoms for people like me who think that way:
4metres - 24 metres of chain. Call that 2.1 fathoms and 13 fathoms of chain /forums/images/graemlins/confused.gif
5 metres - 27 metres of chain / 2.7 fathoms and 15 fathoms of chain
7 metres - 31 metres of chain / 3.8 fathoms and 17 fathoms of chain
9 metres - 36 metres of chain / 5 fathoms and 20 fathoms of chain
10 metres - 38 metres of chain / 5.5 fathoms and 21 fathoms of chain
12 metres - 42 metres of chain / 6.5 fathoms and 23 fathoms of chain
15 metres - 47 metres of chain / 8.2 fathoms and 25 fathoms of chain /forums/images/graemlins/smile.gif
18 metres - 51 metres of chain / 10 fathoms and 28 fathoms of chain
20 metres - 54 metres of chain / 11 fathoms and 30 fathoms of chain
25 metres - 60 metres of chain / 14 fathoms and 32 fathoms of chain
30 metres - 65 metres of chain / 16 fathoms and 36 fathoms of chain.
36 metres - 72 metres of chain
The "shallow" end of the table gives absurd results but then if I were to anchor in 2 fathoms at HW almost anywhere on the UK coast I would dry out at LW!
I do quite often anchor in 4 or 5 fathoms. To pay out 20 fathoms of chain seems excessive, where on the 3:1 formula I would be using 12 or 15. I am of course measuring from the waterline - adding the 5ft (in my case) of sheer to the figure, so that the cable mark is "in the water".
I don't dispute that I would veer another 5 fathoms, and maybe 10, if anchored in 5 in a blow. But in fair weather I see no need to. To veer 15 fathoms in 2.7 fathoms of water is recipe for wandering all over the place and, in the case of many East Coast UK anchorages, drying out on a bank to leeward!
I do have heavy chain. So do the barges and smacks that I have mentioned earlier....
tcm
...
Re: med anchoring
yep, i think that's fine, and do about the same.
yep, i think that's fine, and do about the same.
Das_Boot
New member
Re: Yes, it does,
For my pennys worth all the hoo ha is just that. You have to start somewhere when first anchoring and the rya equation is as good a place as any. From there on it is trial and error.
I would never presume to give anyone advise on anchoring unless they had exactly the same boat as mine with exactly the same anchor and thickness of chain and were anchoring in exactly the same place. Oh and I would never take advice from anyone in this matter.
What works for you might be disaster for someone else.
For my pennys worth all the hoo ha is just that. You have to start somewhere when first anchoring and the rya equation is as good a place as any. From there on it is trial and error.
I would never presume to give anyone advise on anchoring unless they had exactly the same boat as mine with exactly the same anchor and thickness of chain and were anchoring in exactly the same place. Oh and I would never take advice from anyone in this matter.
What works for you might be disaster for someone else.
Mirelle
N/A
Over-complication and the KISS principle...
My point was that the RYA equation gives about the same results as the old 3:1 calculation at the depths that most people anchor their boats in; it gives rather odd results for shallow water and I don't make a habit of anchoring in very deep water!
Trying to think in square roots is gratuitous overcomplication, like the tidal depth sums the RYA seem so keen on.
"Three times the depth at HW, veer some more if the weather is bad" is good enough to remember easily, just as the "rule of twelths" will give you an accurate enough height of tide for a yacht.
My point was that the RYA equation gives about the same results as the old 3:1 calculation at the depths that most people anchor their boats in; it gives rather odd results for shallow water and I don't make a habit of anchoring in very deep water!
Trying to think in square roots is gratuitous overcomplication, like the tidal depth sums the RYA seem so keen on.
"Three times the depth at HW, veer some more if the weather is bad" is good enough to remember easily, just as the "rule of twelths" will give you an accurate enough height of tide for a yacht.
Das_Boot
New member
Re: Over-complication and the KISS principle...
Well if you start at the 3:1 plus 10 or somewhere arround there. It is as good a place as any.
From there on you are on your own. (Trial and error)
Any advice etc is irrelevent no matter from whome it comes. Great sage or dinghy sailor does not matter it will just be hot air.
Well if you start at the 3:1 plus 10 or somewhere arround there. It is as good a place as any.
From there on you are on your own. (Trial and error)
Any advice etc is irrelevent no matter from whome it comes. Great sage or dinghy sailor does not matter it will just be hot air.
Mirelle
N/A
I think you go a little far, there!
I don't think all advice is useless, but I do agree that people can be dogmatic about this subject.
I don't think all advice is useless, but I do agree that people can be dogmatic about this subject.
Krusty
New member
Re: Yes, it does,
Thanks, Mirelle: I see your figures are for the (12 x square root of depth) formula. I have seen that described as the 'Admiralty Formula' (for ships of course) so it is clearly absurd for stranding depths. The 'Twice depth plus 20' (metres) scope I use is simple and practical for small vessels with (say) 27m chain spliced to 60m rope. It seems we all have a grave suspicion of any 'formula' and downright rejection of any 'rule', but we do adopt some guideline for our own use in our own vessel, as a starting point for the exercise of informed judgement. In my view, that is as it should be, but those with little experience often want to learn from those with more. That too is as it should be, especially when a bad decision can result in serious damage, possibly loss of life. I believe we should offer our experience, recognising that it is inevitably limited, and never ram it at anyone.
Thanks, Mirelle: I see your figures are for the (12 x square root of depth) formula. I have seen that described as the 'Admiralty Formula' (for ships of course) so it is clearly absurd for stranding depths. The 'Twice depth plus 20' (metres) scope I use is simple and practical for small vessels with (say) 27m chain spliced to 60m rope. It seems we all have a grave suspicion of any 'formula' and downright rejection of any 'rule', but we do adopt some guideline for our own use in our own vessel, as a starting point for the exercise of informed judgement. In my view, that is as it should be, but those with little experience often want to learn from those with more. That too is as it should be, especially when a bad decision can result in serious damage, possibly loss of life. I believe we should offer our experience, recognising that it is inevitably limited, and never ram it at anyone.
Mirelle
N/A
Agreed.
And thanks for a useful couple of formulae!
And thanks for a useful couple of formulae!
peterb
New member
Not so far out?
[ QUOTE ]
[ QUOTE ]
I looked at the results of various tests on anchors and found that most good anchors (in reasonable holding ground such as mud or sand) were able to take loads of about 10 to 20 times the anchor weight before they dragged.
[/ QUOTE ]I think this is out by an order of magnitude and maybe the reason why you got strange figures? I would hope that my 33kg Bruce wouldn't drag at between 1/3 and 1/2 tonne load. Of course on some bottoms it might, but they wouldn't be regarded as very good holding.
[/ QUOTE ]
For a 33kg Bruce, 10 to 20 times the weight of the anchor equates to a load of between 0.33 tonne and 0.66 tonne. Not so far out? Or are you saying that you think that your breakout loading would be significantly higher?
There are two possible ways to set the problem. I can either work from the maximum pull likely to be exerted by windage etc. on the boat, or I can work from the maximum loading that the anchor can withstand. I can find fairly consistent figures for anchor loadings, taken from a number of published teats, but windage figures vary widely. That's why I started from the bottom of the chain, rather than from the top!
I had a go yesterday at confirming the figures experimentally, by setting up a loaded catenary and measuring the scope necessary for various depths and loads. As might be expected, the theoretical answers were confirmed.
If the measure of 'sufficient' scope is that at the breakout point the pull should still be horizontal, then with typical anchors and weights of chain the RYA "12 times the root" formula needs to be modified to about 20 times the root. My calculation was for a 20 kg (44 lb) CQR type anchor, using 8 mm (5/16") chain weighing (in water) 14 N/m (about 1.4 kg/m) and capable of a breakout load of 2500 N (about 250 kg). Most people use much smaller scopes than that, so that at breakout there would be a vertical component tending to lift the head of the anchor. That's why I suggested that some anchor tests with non-horizontal pulls would be interesting.
PS: Whacko!!! That makes my thousandth post!
[ QUOTE ]
[ QUOTE ]
I looked at the results of various tests on anchors and found that most good anchors (in reasonable holding ground such as mud or sand) were able to take loads of about 10 to 20 times the anchor weight before they dragged.
[/ QUOTE ]I think this is out by an order of magnitude and maybe the reason why you got strange figures? I would hope that my 33kg Bruce wouldn't drag at between 1/3 and 1/2 tonne load. Of course on some bottoms it might, but they wouldn't be regarded as very good holding.
[/ QUOTE ]
For a 33kg Bruce, 10 to 20 times the weight of the anchor equates to a load of between 0.33 tonne and 0.66 tonne. Not so far out? Or are you saying that you think that your breakout loading would be significantly higher?
There are two possible ways to set the problem. I can either work from the maximum pull likely to be exerted by windage etc. on the boat, or I can work from the maximum loading that the anchor can withstand. I can find fairly consistent figures for anchor loadings, taken from a number of published teats, but windage figures vary widely. That's why I started from the bottom of the chain, rather than from the top!
I had a go yesterday at confirming the figures experimentally, by setting up a loaded catenary and measuring the scope necessary for various depths and loads. As might be expected, the theoretical answers were confirmed.
If the measure of 'sufficient' scope is that at the breakout point the pull should still be horizontal, then with typical anchors and weights of chain the RYA "12 times the root" formula needs to be modified to about 20 times the root. My calculation was for a 20 kg (44 lb) CQR type anchor, using 8 mm (5/16") chain weighing (in water) 14 N/m (about 1.4 kg/m) and capable of a breakout load of 2500 N (about 250 kg). Most people use much smaller scopes than that, so that at breakout there would be a vertical component tending to lift the head of the anchor. That's why I suggested that some anchor tests with non-horizontal pulls would be interesting.
PS: Whacko!!! That makes my thousandth post!
BrendanS
Well-known member
Re: med anchoring
As do I.
However, when analysis and forthright comments start flying, I look at the credentials of the people involved. (not bio's!)
Mirelle has been posting for a long while, usually on specific topics and comments, and has gained a huge deal of trust for only posting in areas in which he is competent. ShipsCat (aka Mainly Steam) has posted an amazing amount of very relevant and useful information on many subjects, many of which are controversial, and always has a professional comment on them.
When it comes down to a deciding vote on who is talking sense, I'd back the people who talk sense on a variety of boating issues. I'm not saying they are always correct, but I'd 'listen' first to people who can talk boating and radio and a bunch of issues correctly, then when it gets into areas of contention, I'd listen hardest to those who have proven their credentials here, through previous knowledgeable posts.
As do I.
However, when analysis and forthright comments start flying, I look at the credentials of the people involved. (not bio's!)
Mirelle has been posting for a long while, usually on specific topics and comments, and has gained a huge deal of trust for only posting in areas in which he is competent. ShipsCat (aka Mainly Steam) has posted an amazing amount of very relevant and useful information on many subjects, many of which are controversial, and always has a professional comment on them.
When it comes down to a deciding vote on who is talking sense, I'd back the people who talk sense on a variety of boating issues. I'm not saying they are always correct, but I'd 'listen' first to people who can talk boating and radio and a bunch of issues correctly, then when it gets into areas of contention, I'd listen hardest to those who have proven their credentials here, through previous knowledgeable posts.
Grehan
Well-known member
Tail ender?
Just caught up on this . . very interesting for me, I have never dragged - much - (except through obvious blunder) but moving into the Med and anchoring more than I used to, made me nervous and I'm proud to admit it!
I'm also a bit nervous of dipping my toe in these troubled anchoring waters, but could I ask a technical-ish question, please?
Grehan's 11m, about 11 tons and has a 35HP motor. We set an Oceane spade anchor or a 15kg Bruce, mainly on all-chain (30m) but also often using chain and nylon rope, and we'll usually pay out up to and including some nylon, give some pull, and then retrieve to 4x or so. We're usually anchoring fairly shallowly.
So, the hook seems to be in, and we put on some reverse revs, to set it further and test its hold. Don't we? Do we?
What constitutes a proper test? For gale conditions, say. Full speed reverse, half speed, what?
What is the relationship between loads in more extreme conditions - including those significant snatch loads as has been pointed out hereabove - and this 'testing' engine action?
Sorry you experts if this a daft question, but I ask myself it every time I pay out the scope, stop the cable, and then motion to the wheelhouse superintendent to 'put some revs on'.
---------------------
And on a slightly different tack . . .
What is the technique for using - together - the rope and the chain gypsy on the windlass? I mean how d'ye switch from one to the other as the last of the rope disappears down the hawse hole and the chain comes to the windlass? Seems like a recipe for potential cock-up and panic station. I've got to admit, I use the chain thingy for the rope as well, but I can't believe that's right, and I'll get found out one day.
----------------------
Just caught up on this . . very interesting for me, I have never dragged - much - (except through obvious blunder) but moving into the Med and anchoring more than I used to, made me nervous and I'm proud to admit it!
I'm also a bit nervous of dipping my toe in these troubled anchoring waters, but could I ask a technical-ish question, please?
Grehan's 11m, about 11 tons and has a 35HP motor. We set an Oceane spade anchor or a 15kg Bruce, mainly on all-chain (30m) but also often using chain and nylon rope, and we'll usually pay out up to and including some nylon, give some pull, and then retrieve to 4x or so. We're usually anchoring fairly shallowly.
So, the hook seems to be in, and we put on some reverse revs, to set it further and test its hold. Don't we? Do we?
What constitutes a proper test? For gale conditions, say. Full speed reverse, half speed, what?
What is the relationship between loads in more extreme conditions - including those significant snatch loads as has been pointed out hereabove - and this 'testing' engine action?
Sorry you experts if this a daft question, but I ask myself it every time I pay out the scope, stop the cable, and then motion to the wheelhouse superintendent to 'put some revs on'.
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And on a slightly different tack . . .
What is the technique for using - together - the rope and the chain gypsy on the windlass? I mean how d'ye switch from one to the other as the last of the rope disappears down the hawse hole and the chain comes to the windlass? Seems like a recipe for potential cock-up and panic station. I've got to admit, I use the chain thingy for the rope as well, but I can't believe that's right, and I'll get found out one day.
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snowleopard
Active member
Re: Tail ender?
firstly power-setting. it's best to let the weight come on the anchor gently. the worst thing you can do is dump the anchor and cable over the bow then whack it in reverse, as the chain comes tight the anchor may be jerked free and will merrily skip over the sea bed. the technique i have developed through hard experience is to lower the anchor and cable then have a drink while wind and tide stretch the chain and set the anchor. i only then put some reverse on. if the anchor won't take full astern (built up gradually) i wouldn't trust it to hold while i sleep.
as regards combined rope/chain with a power windlass, the rope is spliced into the end of the chain and a special combination gypsy is used which grips both rope and chain. it is essential to use the type and size of rope specified by the makers of the windlass and to adhere to their advice on type of splice.
firstly power-setting. it's best to let the weight come on the anchor gently. the worst thing you can do is dump the anchor and cable over the bow then whack it in reverse, as the chain comes tight the anchor may be jerked free and will merrily skip over the sea bed. the technique i have developed through hard experience is to lower the anchor and cable then have a drink while wind and tide stretch the chain and set the anchor. i only then put some reverse on. if the anchor won't take full astern (built up gradually) i wouldn't trust it to hold while i sleep.
as regards combined rope/chain with a power windlass, the rope is spliced into the end of the chain and a special combination gypsy is used which grips both rope and chain. it is essential to use the type and size of rope specified by the makers of the windlass and to adhere to their advice on type of splice.
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