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Old 07-30-2013, 05:21 PM   #1
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Anchor Scope Illustrated

Good link from Compass Marine to help visualize (for those of us that need it) what's going on way down there in the briny deep whilst anchoring;

Anchor Scope Illustrated Photo Gallery by Compass Marine at pbase.com
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Old 07-30-2013, 05:47 PM   #2
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Good link from Compass Marine to help visualize (for those of us that need it) what's going on way down there in the briny deep whilst anchoring;

Anchor Scope Illustrated Photo Gallery by Compass Marine at pbase.com
Thanks for the link BUT I hope its does not start another long ANCHOR DISCUSSION!
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Old 07-30-2013, 05:52 PM   #3
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Thanks for the link BUT I hope its does not start another long ANCHOR DISCUSSION!
Why, the possibility never once entered my mind
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Old 07-30-2013, 05:57 PM   #4
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Good link from Compass Marine to help visualize (for those of us that need it) whDt's going on way down there in the briny deep whilst anchoring;
Damn good post! It really illustrates the folly of too short a scope.
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Old 07-30-2013, 06:05 PM   #5
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I thought a 5-1 scope was a 10' depth (bow roller to the bottom) and 50' horizontally from directly below the bow roller to the anchor. I'll bet Chapman spells that out.

Also I thought somebody established that under extreme conditions a chain rode would loose all the catenary. I tend to agree w the OP here. I think Marin got that straight out chain rode stuff from that Rocna guy Smith. That should discredit it right off the bow for me. Wouldn't be hard to prove or disprove though.
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Old 07-31-2013, 05:54 AM   #6
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Thanks for the link BUT I hope its does not start another long ANCHOR DISCUSSION!
Ooohhh...don't be a party pooper Phil. We haven't had a rigorous anchor stousch for ages.
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Old 07-31-2013, 06:55 AM   #7
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I thought a 5-1 scope was a 10' depth (bow roller to the bottom) and 50' horizontally from directly below the bow roller to the anchor. I'll bet Chapman spells that out.

Also I thought somebody established that under extreme conditions a chain rode would loose all the catenary. I tend to agree w the OP here. I think Marin got that straight out chain rode stuff from that Rocna guy Smith. That should discredit it right off the bow for me. Wouldn't be hard to prove or disprove though.
My Chapman's...pretty old now...shows scope as a ratio between rode length against water depth plus height to attachment point. That's because you can't really measure the distance from the anchor to a vertical under your bow along the bottom....

As far as the chain going "bar" tight...there are some reasonable thoughts on that...but none ever seem to stay above the roar of the "mindless internet crowd"...some of us "add" our own anchoring adaptations that never seem to get heard and absorbed into "others" thoughts on the subject.

I'm an all chain guy like many experienced cruisers. I have my reasons and "tweaks" to make it work for me.

About the OP and link...great job in showing "disbelievers" in living color the effects of scope. Granted, in the dynamic world that doesn't exist in his pictures, there are many more concerns with anchoring that hopefully cruisers study and overcome them through experience and sound judgement.
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Old 07-31-2013, 09:41 AM   #8
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"My Chapman's...pretty old now...shows scope as a ratio between rode length against water depth plus height to attachment point. That's because you can't really measure the distance from the anchor to a vertical under your bow along the bottom...."

Chapman is good enough for me and like you say much easier to deal with. The difference is fly stuff anyway. Not the substance of a decent argument.

Excess chain (more than 25-40') is better spent on the anchor .. go figure.

Experience probably tells one how much they need or don't need.

And if experience = chain I'd probably have quite a chunk of it and my experience is that I've never dragged an anchor. Hmmmmmm
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Old 07-31-2013, 09:57 AM   #9
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The majority of all chain cruisers don't think the weight of the chain is all that big of a deal in deciding for all chain...it's been said thousands of times.

Most cruisers have a size, two sizes or even bigger anchors than recommended so arguing the chain is best placed elsewhere pretty much explains the point I made in my last post...here it is again...

"there are some reasonable thoughts on that...but none ever seem to stay above the roar of the "mindless internet crowd"...some of us "add" our own anchoring adaptations that never seem to get heard and absorbed into "others" thoughts on the subject."
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Old 07-31-2013, 10:26 AM   #10
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We can all argue the deatails of the perfect anchoring system until the cows come home. There are so many variables in the sea bottom, anchor design, weather conditions, etc.

But if someone needs an internet link with pictures to understand the fundamental concept of why more scope is better, then it makes me wonder........
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Old 07-31-2013, 10:38 AM   #11
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HaHa and there's no sign of cows on the horizon.

And I'll never argue that more scope is not better for maximizing holding power.

But if you had 300lbs of chain and a 40lb anchor isn't it obvious that a 100lb anchor and 200lbs of chain would deliver far better performance?
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Old 07-31-2013, 10:44 AM   #12
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The illustration show that a rode more than 5 does not change the angle much. At 5 its 10 degrees and at 8 its 6 degrees. So if weight is a concern then having a bigger/heavier anchor might be better than more rode. However, the bottom type and condition are important factors which will be a factor as to the type and size of the anchor. The best illustration I have found is

Synthesis

So did I open the can or worms again!
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Old 07-31-2013, 10:45 AM   #13
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HaHa and there's no sign of cows on the horizon.

And I'll never argue that more scope is not better for maximizing holding power.

But if you had 300lbs of chain and a 40lb anchor isn't it obvious that a 100lb anchor and 200lbs of chain would deliver far better performance?
Taken to an extreme...no...both would be overkill for a dingy...and especially for a dingy owner that watches the weather closely and ties to a secure dock when practical.

Thus the eternal discussion...no one is ever on the same sheet of music in these internet debates on anchoring.....so defend what you prefer ...but saying one setup is better than another (in principle not necessarily a side by side comparison for a specific vessel) is what it always is.....
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Old 07-31-2013, 10:45 AM   #14
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But if you had 300lbs of chain and a 40lb anchor isn't it obvious that a 100lb anchor and 200lbs of chain would deliver far better performance?
Why must it be either or?

Take 300lbs of chain and 100lbs of anchor if it helps you sleep better at night. My little boat is perhaps the only boat on the forum that would feel the extra 100lbs of weight anyway.

Edit: Sorry, 60lbs.
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Old 07-31-2013, 10:46 AM   #15
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But if someone needs an internet link with pictures to understand the fundamental concept of why more scope is better, then it makes me wonder........
Fundamental concept was understood...found it interesting to actually see the diminishing returns as scope was increased. Hard day at work or something?
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Old 07-31-2013, 12:02 PM   #16
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Why must it be either or?

Take 300lbs of chain and 100lbs of anchor if it helps you sleep better at night. My little boat is perhaps the only boat on the forum that would feel the extra 100lbs of weight anyway.

Edit: Sorry, 60lbs.
My comment wasn't a recommendation but an example to prove my point. I have a friend w a Willard 30 that has a 65# Forfjord so a 100# anchor on a 40' trawler isn't "extreme". And it's doing some good.

The only reason for all chain is to reduce radius swinging at anchor, you don't trust the required splice for the combination rode or the REEL winch is not yachty enough for you.
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Old 07-31-2013, 12:57 PM   #17
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My comment wasn't a recommendation but an example to prove my point. I have a friend w a Willard 30 that has a 65# Forfjord so a 100# anchor on a 40' trawler isn't "extreme". And it's doing some good.

The only reason for all chain is to reduce radius swinging at anchor, you don't trust the required splice for the combination rode or the REEL winch is not yachty enough for you.

If you feel that is THE ONLY REASON for all chain...WOW!!!!!
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Old 07-31-2013, 03:34 PM   #18
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The main reason is probably just to help the anchor set. Once it's set and if the rode gets straightened out in a big blow loosing it's catenary there's not any reason or benefit for having chain in your rode as far as holding power is concerned. But of course there is swinging room, convenience ect ect.
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Old 07-31-2013, 06:03 PM   #19
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Maybe benefits beyond just holdng? Like almost no chafe to worry about, easy retrieval (if that what you are set up for), short scope in moderate to light conditions, etc..etc...I bet people have posted dozens of advantages (at least to them)...that's what I mean when I say sometimes facts are lost in the din of internet posting.....

Sure FF has a point that having coiled nylon on deck is light and easy to take care of and doesn't smell...but if you are going to stow your gear in an anchor locker...I'll take chain every time...

I could go on forever...but that what these threads do anyway...so I'll make dinner instead.

But to say there's only one reason for chain is just an unbelievable statement.
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Old 07-31-2013, 06:57 PM   #20
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