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Old 29-01-2012, 15:13   #31
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pirate Re: Anchor Chain Length Versus Weight

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Originally Posted by Lagoon4us View Post
I've always calculated depth + height of bow-roller to water times scope required for situation. e.g. 3 x d+h for safe stop staying on board and up to 7 x d+h for maximum hold. Works for me....Cheers
Damn.... and I've always thought that 'depth + height of Bow-roller to water' was the Drop...
You know... drop it of the bow... till it hits the bottom...
split hairs or what...
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Old 29-01-2012, 15:28   #32
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Re: Anchor Chain Length Versus Weight

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Damn.... and I've always thought that 'depth + height of Bow-roller to water' was the Drop...
You know... drop it of the bow... till it hits the bottom...
split hairs or what...
Not splitting hairs, not looking at or for arguments on various yachts i've owned it represents a further 20 plus feet.

I think when people post anchoring guidelines related to the length of the boat as patently dangerous should a newcomer follow that advice....
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Old 29-01-2012, 15:40   #33
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Re: Anchor Chain Length Versus Weight

Sorry also forgot to multiply the scope by the expected tide rise (if any)... Don't know how many times if seen tide rise bring unmanned boats adrift, here ours is 6 metres so could be 42 metres more needed if we anchored at low water... But that also may be judged as splitting hairs?
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Old 29-01-2012, 15:47   #34
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pirate Re: Anchor Chain Length Versus Weight

Quote:
Originally Posted by Lagoon4us View Post
Not splitting hairs, not looking at or for arguments on various yachts i've owned it represents a further 20 plus feet.

I think when people post anchoring guidelines related to the length of the boat as patently dangerous should a newcomer follow that advice....
Hmmmmm.... sorry to hear you feel I dish dangerous advice....
I merely state what I do... and do as I state...
if you choose to view that as advice its your decision...
and if folk read on it says... I lay out more if it starts to blow a bit.
That would be in the 30ft... in the 10ft I would not bother...
but will say this... you guys would be altering your rode's every 6hrs in the Channel ports...
Note to self.... no more answering anchor posts
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Old 29-01-2012, 15:55   #35
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pirate Re: Anchor Chain Length Versus Weight

Quote:
Originally Posted by Lagoon4us View Post
Sorry also forgot to multiply the scope by the expected tide rise (if any)... Don't know how many times if seen tide rise bring unmanned boats adrift, here ours is 6 metres so could be 42 metres more needed if we anchored at low water... But that also may be judged as splitting hairs?
See post number 10
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Old 29-01-2012, 15:59   #36
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Re: Anchor Chain Length Versus Weight

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Ok... let me try and simplify for you.....
I like to anchor normally with 3.5 times my boat length + drop to bottom....
When it blows I like to be able to put out at least another coupla boat lengths of chain... despite the catenary crap... its how I've anchored for 40plus years and I aint changing for something where folks watch me go past backwards rather than my current practice... watching them go backwards...
Also its nice to be able to drop in 15m occasionally if needed.....
Hence on my 21ft I carry 170ft of chain..
so... so's you understand...
me 21foot...
depth 30foot
Chain out = 30ft(depth) + 75foot(3.5xboat length) = total 105foot...
If thats to complicated let me know...
Not complicated. Just as I suspected -- it's voodoo science.

The rest of the world understands proper scope as a ratio of length of rode to depth+height above water for rode attachment. This can range from 3:1 in mild conditions to 7:1 (or greater) for storm conditions. None of that has anything to do with boat length.
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Old 29-01-2012, 16:08   #37
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pirate Re: Anchor Chain Length Versus Weight

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Originally Posted by SailFastTri View Post
Not complicated. Just as I suspected -- it's voodoo science.

The rest of the world understands proper scope as a ratio of length of rode to depth+height above water for rode attachment. This can range from 3:1 in mild conditions to 7:1 (or greater) for storm conditions. None of that has anything to do with boat length.
You calculate your way dude... and I'll use my way of measuring...
The guy asked for how much chain he should carry...
I said the equivilent of 7 boat lengths of the 5/16th.... thats all...
But shoot... what do I know...
Oh yeah I do... this is a secret gun thread... thats why everyones got a scope...
I just love that word... Proper... its like Expert... gotta sorta ring to it...
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Old 29-01-2012, 16:48   #38
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Re: Anchor Chain Length Versus Weight

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Sigh....
Funny... never swung into anyone yet... and rarely (except thick weed) dragged...
remember.... you guys also call a torch a flashlight... which I call an Aldis lamp...
and a spanner a wrench... which is someting that pulls my shoulder out...
You go your way and I'll stay on mine...
Save's buying a ROCNA to hold me...
PS; drop to water from roller is 3ft....ish
This isn't even remotely related to semantics. You are calculating the amount of rode required to safely hold your boat. It doesn't matter what you call it, length is length. And the way that you calculate it will come out with a vastly different length than you need in some conditions, and more than you need in others.

This really isn't a personal preference thing like what you put on your toast in the morning, and it doesn't matter if you use different words for the same thing, either. What matters is that your boat doesn't drag.

There might be a reason that every boating book, website, and sailing instructor all give the exact same answer. This isn't something that is even remotely debated by anyone. It's not a gun or anchor brand debate. This is simple geometry and basic understanding that anchors need to be pulled "along" the seabed to work, not up out of the seabed.

It can be a shock to discover that the way you've been doing things for years isn't right and that there's a better way. But don't let stubborness get in the way of learning something from your friends here. I've learned plenty. As a group we're pretty smart.

I think the reason that you haven't had serious problems yet is the statement that if the wind picks up, you put out more scope if you're in deep water and it starts to blow a bit. It's in deep water where your scope is seriously lacking using your formula. If you had put enough out to begin with, you'd be fine. Instead, you put out more and come up to a decent scope in the end anyways. Wouldn't it be nice to understand why that is and just do it right from the start?
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Old 29-01-2012, 16:56   #39
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Re: Anchor Chain Length Versus Weight

I use 3/8 chain because it was free, but I agree heavier anchor and high test chain (still being strong enough) is probably better use of weight. Of course the heavier chain will last longer and the low test chain can be re-galvanized a lot more times, so if cost is a concern, high test chain might not be the best choice.

Yes the heavier chain gives a better ride, but once it is tight it doesn't matter which weight you use. I think it would be more effective to just put a heavy weight halfway along the chain when needed than have really heavy chain.

Maybe if you really care about weight and cost, you could use galvanized steel cable instead of chain, but then you would need a drum.
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Old 29-01-2012, 16:59   #40
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pirate Re: Anchor Chain Length Versus Weight

Quote:
Originally Posted by cwyckham View Post
This isn't even remotely related to semantics. You are calculating the amount of rode required to safely hold your boat. It doesn't matter what you call it, length is length. And the way that you calculate it will come out with a vastly different length than you need in some conditions, and more than you need in others.

This really isn't a personal preference thing like what you put on your toast in the morning, and it doesn't matter if you use different words for the same thing, either. What matters is that your boat doesn't drag.

There might be a reason that every boating book, website, and sailing instructor all give the exact same answer. This isn't something that is even remotely debated by anyone. It's not a gun or anchor brand debate. This is simple geometry and basic understanding that anchors need to be pulled "along" the seabed to work, not up out of the seabed.

It can be a shock to discover that the way you've been doing things for years isn't right and that there's a better way. But don't let stubborness get in the way of learning something from your friends here. I've learned plenty. As a group we're pretty smart.

I think the reason that you haven't had serious problems yet is the statement that if the wind picks up, you put out more scope if you're in deep water and it starts to blow a bit. It's in deep water where your scope is seriously lacking using your formula. If you had put enough out to begin with, you'd be fine. Instead, you put out more and come up to a decent scope in the end anyways. Wouldn't it be nice to understand why that is and just do it right from the start?
I do understand.... honest... and I never anchor in more than 5metres... only done it once and that was Cherbourg...
I know if using chain a scope of 4xmax depth is the norm... well according to the RYA anyway... but I first learnt in '63... no RYA...
But a sage old seaman told me this and I'm happy with it... its held me in places all over... appreciate your trying to put me right but you know what they say....
"Ain't no fool like an old fool..."
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Old 29-01-2012, 17:07   #41
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Re: Anchor Chain Length Versus Weight

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I do understand.... honest... and I never anchor in more than 5metres... only done it once and that was Cherbourg...
I know if using chain a scope of 4xmax depth is the norm... well according to the RYA anyway... but I first learnt in '63... no RYA...
But a sage old seaman told me this and I'm happy with it... its held me in places all over... appreciate your trying to put me right but you know what they say....
"Ain't no fool like an old fool..."
Aha!!! Mystery solved. In your particular circumstances, your deepest anchorage is 5 meters = 15', plus 3' for the fall from the bow roller to the surface. Call it 20'. Your formula gives 20+75= 95' of chain, which just happens to be about 5:1 scope. So your worst case scenario is just about right. You usually have too much chain out, not too little because you happen to anchor in shallow places. This is only a problem if you're also in crowded anchorages.

So maybe we can compromise a bit. We all promise to stop harassing you, and you promise to remember that your rule only works in shallow places. That way you might resist the urge to pass it on to some young sailor or to keep using it when you decide to anchor somewhere deep.
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Old 29-01-2012, 17:22   #42
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pirate Re: Anchor Chain Length Versus Weight

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Originally Posted by cwyckham View Post
Aha!!! Mystery solved. In your particular circumstances, your deepest anchorage is 5 meters = 15', plus 3' for the fall from the bow roller to the surface. Call it 20'. Your formula gives 20+75= 95' of chain, which just happens to be about 5:1 scope. So your worst case scenario is just about right. You usually have too much chain out, not too little because you happen to anchor in shallow places. This is only a problem if you're also in crowded anchorages.

So maybe we can compromise a bit. We all promise to stop harassing you, and you promise to remember that your rule only works in shallow places. That way you might resist the urge to pass it on to some young sailor or to keep using it when you decide to anchor somewhere deep.
I don't anchor deep... full stop... in the Carib, the Med or the W Europe seaboard...
I'd rather keep sailing... or go in the marina...
if you think I'm hauling 30ft+ drop of chain plus an anchor by hand your nuts... but thanks for the flowers anyway...
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Old 29-01-2012, 18:55   #43
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Re: Anchor Chain Length Versus Weight

Okay you only anchor shallow! The discussion here is to some extent rule of thumb anchoring.
Thanks cwyckham you are a genius!!!!

Boatman we finally got there, no hairs split! cheers frank
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Old 29-01-2012, 19:16   #44
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pirate Re: Anchor Chain Length Versus Weight

Great.... I can now abandon anchor threads....
forever...
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Old 30-01-2012, 04:56   #45
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Re: Anchor Chain Length Versus Weight

I always wonder why people on anchor threads are so interested in proving they are right and others are wrong!

I also note that the math experts like to do battle on them.
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