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Old 11-02-2015, 04:02 PM   #21
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Quote:
Originally Posted by markpierce View Post
Anchor rode scope is not an expression of an angle. It is the relationship of the distance between sea bottom and where the rode exits the boat versus the length of rode deployed . So, a vertical line is 1:1
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Originally Posted by manyboats View Post
But I disagree w you Mark. A vertical rode is not even a ratio. The anchor is just "X" feet deep.


I think Mark's right.

In 10' water depth and with a bow roller 5' off the water... 15' of rode would be a 1:1 relationship. Or actually 15:15, but then reduced to 1:1 with some whizzy math.

(With some discrepancy for the length of the anchor shank.)

So the "ratio" is "feet of rode" to "feet of depth." (Or meters, for our metric brethren around the world.)

-Chris
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Old 11-02-2015, 07:11 PM   #22
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Brian, Mark and Chris are indeed right.
And I am wrong.
And Mark's right it has nothing to do w degrees or rode angle.

From a standpoint of physics the angle of the rode is the operative element of scope performance as I see it but it's not true re the actual rode definition. In a perfect world I would see the scope number representing the angle of the rode. But it is the way it is to make it as easy as possible to consistantly anchor at a good rode angle re the performance of the anchor. Anchors vary .. Like the Claws having fairly low performance overall but what performance they do have is extended further into the short scope range. A good short scope anchor should then have fairly good performance at 2-1 as the rode will be flatter than it would at 45 degrees ... I think. What scope 45 degrees would be I don't know but think it would be too short or steep re the rode angle.

I also thought the scope was measured from the surface of the water .. not the bow roller. Again .. Makes it simple.
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Old 11-02-2015, 08:57 PM   #23
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Angles for Common Anchor Scopes

Quote:
Originally Posted by markpierce View Post
Anchor rode scope is not an expression of an angle. It is the relationship of the distance between sea bottom and where the rode exits the boat versus the length of rode deployed . So, a vertical line is 1:1
Exactly
So here are few common anchor scopes converted to the angle (theta) between the rode and vertical from the bow... (the pdf is a little crisper than the snapshot)
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Old 11-03-2015, 06:16 AM   #24
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WE much prefer a line to the crown to use for recovery , with ant anchor style..

In a crowded anchorage it also helps the next folks in to not foul your set,

We tie off to the crown with a 1/4 ir 3/8 line which is then run thru the loop of a small 6 - 8 inch ball and tie the end to a std lead sounding weight.

This automatically floats the ball directly above the anchor.

And should you need accurate soundings , the gear is already on the deck , ready for use.
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Old 11-03-2015, 08:33 AM   #25
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From decades of boating and anchoring nearly every night aboard boat (that's hundreds of times) I only experienced one of our anchors become irretrievable. That was in mid 1960's, Block Island, Big Bay. We worked on it for hours trying to get it loose... finally cut the rode and called it good. The 30 + lb Danforth must have been severely snagged on cable or other immovable object. Never have used a crown line. Doubt it would have helped in the "snagged" case sited above.


I also had to cut anchor line for boater in distress once. Due to circumstances, didn't have very much time to dick around trying to pull it up. Three of us in launches tried our best for fair amount of time - no luck!


Oh well - in five + decades of being an active hand or Captain aboard boats... that equals only two anchors lost that I experienced first hand and that were released via rode-cut by my hands! Not too bad, I guess!!
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Old 11-03-2015, 09:11 AM   #26
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As someone else mentioned here somewhere, you can fashion a retrieval system for badly snagged anchors with a length of chain and a couple of lines. Having a tender deployed is handy. Attach a line to each end of chain. Lacking a length of chain (which is best), a double chain plate snubber can be used if lines made long enough. Loop around anchor rode and let slide down all the way. Put some slack in anchor rode with big boat, say with 2:1 rode (but not so much that rode can reach running gear). Pull retrieval lines steadily with tender in opposite direction. The longer those lines can be the better to lower the angle. If you don't have a tender, same drill, but spin the big boat around with more scope and pull.. careful now!
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Old 11-09-2015, 06:31 AM   #27
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If X is feet and Y is anchor position then what is Z?
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Old 11-09-2015, 10:11 AM   #28
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If X is feet and Y is anchor position then what is Z?
Huh???
Draw us a diagram or restate.

The normal anchor ratios stated are Length of rode over distance from bow roller to bottom (water depth + HT of bow above water)

So... 1:1 = vertical
5:1 = L of rode = 5x (depth + HT of bow)

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Old 11-09-2015, 10:16 AM   #29
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Huh???
Draw us a diagram or restate.

The normal anchor ratios stated are Length of rode over distance from bow roller to bottom (water depth + HT of bow above water)

So... 1:1 = vertical
5:1 = L of rode = 5x (depth + HT of bow)

Don
To me - 1:1 represents some angle. Rode vertical (absolutely straight down; i.e 100% plumb) off bow to water/anchor position... I call 1:0
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Old 11-09-2015, 10:31 AM   #30
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Art I thought so too but that's not the case.

I was convinced of it but now can't get my head around it. If 3-1 is 90 feet out and 30' down. 1-1 is length of rode 30' and depth 30'. Straight up and down rode. You can't have 0 unless the boat is submerged up to it's bow roller in the sea bottom. My whole anchor scope concept is scrambled now.

It's the length of the rode and the depth. A vertical rode ready for weighing is 1-1. I had always thought 1-1 was 30' horizontal distance and 30' deep. The distance (horizontally) from the bow roller to the anchor is not considered at all. Horizontal distance is expereesd in the length of the rode deployed. I had always thought of 1-1 as 30' horizontal and 30' deep .. or a 45degree rode. Chapman describes it as 30' of rode and 30' deep. I don't like it either.
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Old 11-09-2015, 10:47 AM   #31
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Art I thought so too but that's not the case.

I was convinced of it but now can't get my head around it. If 3-1 is 90 feet out and 30' down. 1-1 is length of rode 30' and depth 30'. Straight up and down rode. You can't have 0 unless the boat is submerged up to it's bow roller in the sea bottom. My whole anchor scope concept is scrambled now.

It's the length of the rode and the depth. A vertical rode ready for weighing is 1-1. I had always thought 1-1 was 30' horizontal distance and 30' deep. The distance (horizontally) from the bow roller to the anchor is not considered at all. Horizontal distance is expereesd in the length of the rode deployed. I had always thought of 1-1 as 30' horizontal and 30' deep .. or a 45degree rode. Chapman describes it as 30' of rode and 30' deep. I don't like it either.
IMO - If one of the #'s 1 relates to scope... then for scope to exist there must be an angle of rode from bow to anchor. Otherwise... if rode is 100% plumb off bow to anchor there exists "Zero" scope. Thus 1:0!
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Old 11-09-2015, 10:50 AM   #32
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Anchor Rode / Scope

Art, Eric...

Maybe a picture will help. Right out of Chapmans.

This is why we mark the rode and it's easy to determine what the rode L is and you get D form depth finder + known ht of bow for your vessel.

Interesting how many folks get things stuck in their mind.
I've had folks explain to me that Red Right Return meant Keep Red to Port When return TO the sea.. and they were absolutely sure that's what it meant.
Surprised they haven't had some serious problems.
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Old 11-09-2015, 10:59 AM   #33
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Quote:
Originally Posted by Art View Post
IMO - If one of the #'s 1 relates to scope... then for scope to exist there must be an angle of rode from bow to anchor. Otherwise... if rode is 100% plumb off bow to anchor there exists "Zero" scope. Thus 1:0!
Art...

I think that's where folks get hung up...
The ratio of scope is not an angle - it can be converted to an angle - see post #23 above -

"Scope of the Rode" is also NOT rise over run as in "slope of a road"(no pun intended) or stairs.

It is the the hypotenuse (L of rode) over rise (depth to bow)
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Old 11-09-2015, 11:01 AM   #34
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Art, Eric...

Maybe a picture will help. Right out of Chapmans.

This is why we mark the rode and it's easy to determine what the rode L is and you get D form depth finder + known ht of bow for your vessel.

Interesting how many folks get things stuck in their mind.
I've had folks explain to me that Red Right Return meant Keep Red to Port When return TO the sea.. and they were absolutely sure that's what it meant.
Surprised they haven't had some serious problems.
Don - I feel that "0" rode angle = "0" scope. "0" angle simply can't = a scope of 1. To me 1:1 means there is some scope in play. At 100% plumb off bow there is NO scope in play... which means in that instance that scope does Not At All Exist... therefore it has to be 1:0 ;i.e., "0" scope.

But anyway - Nice of Chapman to put profile of my Tollycraft on the page!
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Old 11-09-2015, 11:33 AM   #35
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Don - I feel that "0" rode angle = "0" scope. "0" angle simply can't = a scope of 1. To me 1:1 means there is some scope in play. At 100% plumb off bow there is NO scope in play... which means in that instance that scope does Not At All Exist... therefore it has to be 1:0 ;i.e., "0" scope.

But anyway - Nice of Chapman to put profile of my Tollycraft on the page!
Art...
As with any discussion on TF you are certainly entitled your your opinion

I'm not sure if your interpretation of the ratio is Horiz run : Vertical depth?
If so per your interpretation "0" = 0:1 = vertical rode and 1:1 = 45* angle

and in reality it doesn't make that much difference when you are talking "normal" working scopes of 5:1 or 7:1 they differ greatly at the low end.

The difference in the angle between Chapmans (& others) and your interpretation are very small until you get to small scopes
Chapmans can never go below "1" where your interpretation goes to "0"
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Old 11-09-2015, 11:51 AM   #36
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Art...
As with any discussion on TF you are certainly entitled your your opinion

I'm not sure if your interpretation of the ratio is Horiz run : Vertical depth?
If so per your interpretation "0" = 0:1 = vertical rode and 1:1 = 45* angle

and in reality it doesn't make that much difference when you are talking "normal" working scopes of 5:1 or 7:1 they differ greatly at the low end.

The difference in the angle between Chapmans (& others) and your interpretation are very small until you get to small scopes
Chapmans can never go below "1" where your interpretation goes to "0"
Equally and
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Old 11-09-2015, 12:06 PM   #37
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Don I understood it weeks ago .. Just don't like it.
Dosn't matter .. it is what it is.
I went straight to Chapman and it's clear there. We are just trying to use the horizontal distance and not the length of the rode. At longer scopes there's little difference but at short scopes the "scope" of it all seems more clear to me using distance and not rode length in the function of relating to anchoring scope. But when talking to other people one muct use the language that is vogue or you won't comunicate well.

And I see why rode length is used in that it is much much more easily determined on the fly where one needs to know what his relative scope is. We all feed out "X" # of feet of line or chain but how are we to measure the distance from the bow to the anchor?
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Old 11-09-2015, 12:11 PM   #38
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Art, Eric...

Maybe a picture will help. Right out of Chapmans.
That is the way I have always heard scope defined, be it by the USCG Auxilliary boating course my wife and I took back in the 1980s to the conversations in the marine supply store in our harbor where we bought our new chain rode to discussions about anchoring in the boating club we belong to.

A scope of one to one would be thirty feet of rode out and thirty feet to the bottom. A scope of two to one would be sixty feet of rode out and thirty feet to the bottom, and so on. Very basic, very simple.
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Old 11-09-2015, 12:16 PM   #39
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Marin,
Yes simple in this case is an advantage in that it makes it more useable.
I'm fairly good at making things more complex than they are.
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Old 11-09-2015, 12:23 PM   #40
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Quote:
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We all feed out "X" # of feet of line or chain but how are we to measure the distance from the bow to the anchor?
Eric
Everyone can easily measure the bow ht from the water and file this away as a constant or leave a sticky at the helm. When getting ready to anchor it's easy to get the depth from a depth finder and simply add the constant bow ht.

Then all you have to do is multiply the sum by the "scope" you intend to use for anchoring...
5:1 (lunch hook) 7:1 "normal" conditions o'nite 10:1 storm anchoring...
rather straight forward - and deploy that L of rode.

I would ask... how do you calculate the L of rode to deploy if you want a horizontal distance of 7 x the depth? - you'd need a Trig table & calculator
Or how do you determine the horizontal distance from your bow to the anchor position?

But let's not use whatever works for you
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