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Old 01-20-2011, 10:32 AM   #1
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Anchor slot/hole

For years I've noticed most anchors have a hole in the end of the shank for the shackle and many others have a slot and Ive been curious what the reason would be for a slot. I've always attached the shackle w the pin through the hole/slot of the shank*** ..seemingly the only logical way to do it but now it occurs to me that one could probably put the ear on the horseshoe part of the shackle through*the slot. I like to put the biggest pin through the shank hole that will fit so the shackle won't move sideways and try to bend the shank. I like to have a fairly close fit shackle pin to shank hole. I notice there is a "anchor shackle" that has a larger dia "horseshoe" that appears to be designed to take sideways pull from the rode. Could it be that the slot is there to pass the "ear" of the shackle horseshoe end through the shank? Would that reduce bending forces on the shank? *If not WHY do some anchors provide the slot? In view of the fact that it's more trouble to make a slot there must be a reason for it.
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Old 01-20-2011, 11:50 AM   #2
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RE: Anchor slot/hole

The Rocna has a slot. While I have not talked to them about the reasoning for this, their illustrated manner of attaching the rode is to put the closed end of a shackle through the slot with the pin through the chain. The only way to feed a shackle through the shank is with a wider hole, or slot.

The benefit of putting the closed end of the shackle through the shank rather than the pin is that if the closed end is in the shank the shackle is free to rotate in any direction and align the shackle pin with the load. In other words, with the closed end of the shackle attached to the anchor shank there are no sideways loads on any component of the rode. The pull is always going straight through the shackle as opposed to a sideways load being applied to the pin, which could be the case if the shackle was attached to the anchor with the pin.

In reality it's probably a pretty subtle point since I would think it would take a heck of a side load to damage the pin of a properly-sized shackle.

That's the only reason I can think of. You can always call Rocna in New Zealand and ask them. It's been a number of years since we acquired ours, but at the time the folks at Rocna were quite helpful when I had questions.
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Old 01-20-2011, 12:01 PM   #3
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RE: Anchor slot/hole

I don't see the functional difference between the shackle rotating on the shank or the anchor*chain rotating on the shackle.* I still think it is a marketing ploy.
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Old 01-20-2011, 12:14 PM   #4
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Anchor slot/hole

Quote:
markpierce wrote:

I don't see the functional difference between the shackle rotating on the shank or the anchor*chain rotating on the shackle.* I still think it is a marketing ploy.
If the shackle rotates or pivots on the shank, the load on the pin will always be at right angles to the pin.* There will be no shear load on the pin.* If the pin is in the shank and the load shifts out of line with the shank, which it invariably does, the chain will be angled off to the side of the anchor but the shackle will remained lined up with the shank because of the straight pin through the hole.* So the load on the pin will now be a shearing load as opposed to a straight load.

I don't see any marketing advantage to providing a slot vs a hole.* I think it's more to do with what the anchor designer felt provides the optimum setup.* I don't think it has anything to do with new generation anchor vs old generation anchor, eiher. Our POS Bruce which is now propping open a door in our garage is a very old design by today's standards and it has a slot, too, just like the Rocna.

How susceptible a shackle pin would be to damage with a shearing load is something I cannot hazard a guess on.* But it's the only reason I can think of for providing a way to attach the closed end of a shackle to an anchor as opposed to attaching the open end with a pin.


-- Edited by Marin on Thursday 20th of January 2011 01:56:00 PM
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Old 01-20-2011, 12:26 PM   #5
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RE: Anchor slot/hole

Thanks, Marin.* I see it now.*
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Old 01-20-2011, 01:07 PM   #6
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RE: Anchor slot/hole

Quote:
Marin wrote:I don't see any marketing advantage to providing a slot vs a hole.* --*
*It has little to do with marketing. The slot is there so that a single shackle can be used to connect the chain to the shank rather than having to use two shackles because the lugs won't pass through the link, especially if it is studded chain.
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Old 01-20-2011, 01:29 PM   #7
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RE: Anchor slot/hole

Rick,
What's a "lug" and what's a "studded chain"?
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Old 01-20-2011, 01:33 PM   #8
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RE: Anchor slot/hole

Quote:
RickB wrote:The slot is there so that a single shackle can be used to connect the chain to the shank rather than having to use two shackles because the lugs won't pass through the link, especially if it is studded chain.
I had forgotten this advantage even though we took advantage of it.* In the first photo below you will see that the Rocna is connected to the rode with two shackles.* Then I read the directions that came with the anchor and realized that by putting the closed end of one shackle through the anchor shank I could elminate the second shackle.* The fewer components in an anchor system the better in my opinion.* So that's the way it's set up now. (second photo).

The bungee is there due to my lack of observational powers.* For all the years we've had the Rocna I believed (and said in posts) that the Rocna sits this way, with the shank up in the air.* Wrongo.* The* ass-in-the-air attitude makes it a breeze to deploy--- I just start letting out rode and off it goes.* But I just recently realized it's being held in this position by the bail or keeper over the front of the shank. It's too short to let the anchor lie back properly with its shank down in the pulpit channel.* So I've made a new, taller bail and once I put it on--- hopefully this weekend--- the Rocna will sit solidly into the pulpit channel and behave itself and I can dispense with the bungee.

*
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Old 01-20-2011, 01:36 PM   #9
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RE: Anchor slot/hole

Quote:
nomadwilly wrote:

Rick,
What's a "lug" and what's a "studded chain"?
I believe the lug is the wider portion of the shackle legs that the pin goes through on one side and threads into on the other side.

*
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Old 01-20-2011, 01:56 PM   #10
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Anchor slot/hole

Quote:
nomadwilly wrote:What's a "lug" and what's a "studded chain"?
Marin got the "lug" correctly. A "studded chain" is what you sometimes need on your tires to drive the Columbia Gorge in winter.

Not really, it is the type of chain that has the cross piece in the center of a link to help stiffen the links and it also helps prevent tangling by limiting the amount of travel between links.

*


-- Edited by RickB on Thursday 20th of January 2011 03:01:21 PM
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Old 01-20-2011, 03:22 PM   #11
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RE: Anchor slot/hole

Ya Know,I just learn a lot from you all,thanks, little things add up and it all helps. BB
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Old 01-21-2011, 04:29 AM   #12
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RE: Anchor slot/hole

Quote:
belizebill wrote:
Ya Know,I just learn a lot from you all,thanks, little things add up and it all helps. BB
Now BB, just when you thought it all worked out re these slots, I havdatellya, there are slots, and then there are SLOTS...........now what do you think this slot is for......?
Sorry Marin, Eric et al, but I couldn't resist......



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Old 01-21-2011, 05:16 AM   #13
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RE: Anchor slot/hole

More to the point, what do you think it is for?
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Old 01-21-2011, 08:47 AM   #14
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RE: Anchor slot/hole

Perhaps one could hook a bouy in that slot.BB
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Old 01-21-2011, 09:25 AM   #15
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RE: Anchor slot/hole

So PB has the BIGGEST SLOT! I'll find something on my boat that is the biggest, if I look hard enough.

I note he also has two shackles and a swivel, so he gets the prize for the most complicated setup.

I think the jury is still out on whether the slot is of any benefit. Sure, you can raise a fouled anchor, if you are skilled in the operation of that type of slot, but can't you also trip an otherwise well secured anchor accidentally, just by drifting to around 180 degrees and pulling gently?
I'll stick to a short slot and one shackle for my system, thanks.
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Old 01-21-2011, 12:06 PM   #16
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RE: Anchor slot/hole

"just by drifting to around 180 degrees"

As in when the current reverses OR when you are about to get whacked by a T storm?
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Old 01-23-2011, 05:11 AM   #17
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Anchor slot/hole

The slot is for tripping a fouled or heavily embedded anchor, and does it very well, with no extra floaty contraptions needed to complicate things, merely by taking up nearly all the slack and while chain is vertical motoring slowly forwards over it. Not to mention the fact most never think to set their anchor trip line & buoy up until they are fouled, by which time, about all you can say is....bugger...I should have rigged my anchor trip line and float, but I thought the bottom here would be ok.
As to the theoretical loss of set of the anchor....yawn...an endlessly repeated mantra by those who don't have an anchor with this system, but in my experience, never encountered in real life, as in real life the anchor chain never traverses an exact straight line back over the anchor shank, (and even in the freakish situation it did it would set again in no time), so it just pulls the end of the shank around as the boat reverses direction with tide or current just like every other anchor, perhaps momentarily disturbing the set a tad, but it beds in that damn quick again, it's irreverent....yawn.* See for yourselves, don't take my word for it....
http://www.anchorright.com.au/products/sarca-anchors


-- Edited by Peter B on Sunday 23rd of January 2011 06:14:50 AM
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Old 01-23-2011, 02:31 PM   #18
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RE: Anchor slot/hole

I just came back from the boat and see that my Manson Supreme has a slotted hole below the long slot. What I may do is bolt a 12lb split round of lead on the end of the shank to boost short scope performance. I think if I regularly used a trip line I'd have to have two lines*** ...one about 50' and one about 90'. I've only deployed a trip line once but it didn't seem like much trouble. Our big tides here don't help. Peter, I still don't know any source for those Sarca anchors in the US.
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Old 01-23-2011, 09:46 PM   #19
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RE: Anchor slot/hole

Quote:
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I've only deployed a trip line once but it didn't seem like much trouble
We use a trip line with our anchor fairly often (we did with the Bruce, too).* We've never had a fouling problem with it at all.

PeterB--- All the posts and comments in magazines about the problem of the "trip slot" in the* Manson Supreme were from people who had the anchor and had it un-set when the wind or current moved the boat out to the side or around behind it.* The comments weren't from people speculating on what might happen, they were from people who had it happen.*

Perhaps the Sarca's geometry is such that this is not a problem with that anchor.* All the accounts I've read were from Manson owners.* I've never seen anyone comment on this problem or non-problem in reference to a Sarca.

*
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Old 01-23-2011, 10:18 PM   #20
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RE: Anchor slot/hole

Marin, Peter B,
Very few anchors don't break out in a 180 degree turnabout. And those that don't break out probably only not do so in certain bottoms. So basically if you do a 180 your going to break out so what's the difference if you break out w or w/o the slot?

"We use a trip line with our anchor fairly often"
On what occasions do you not use the trip line?
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