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Old 03-04-2015, 05:37 PM   #221
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Yes, I regularly use an Anchor Buddy together with all chain rode. I think it is a great device and I have never dragged the anchor when using it.
Mike, one more question, any experience with wind changing direction 180 deg? Typically we go from an onshore to offshore breeze overnight and wake pointing in the opposite direction. I don`t dive and photograph the Sarca so can`t say if it resets. Do you think the Anchor Buddy has any effect or issue in that situation?
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Old 03-04-2015, 05:46 PM   #222
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Attention all newbies!!!


Walk up and down any dock full of full time cruisers and you will see a lot of consistency that is not expressed here. Not that they are the most knowledgeable, nor do they have the latest and greatest equipment, but they are out there slogging it out with the rest of us....without dragging anymore than most of us.

See what works locally, see if that is good for you and then practice and expand your equipment and practice when venturing further.
Excellent advice. No one knows better what anchors work nest in your cruising grounds than folks who have lots of expreience anchoring in your cruising grounds.
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Old 03-04-2015, 05:49 PM   #223
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Tie a 6 to 8lb weight to the line about 3 to 5' from the end on the ground..
You didn't say anthing about putting a weight on the line. Thye comment I was responding to was your incorrect claim that the chain in an all-chain rode next to the bow roller has no effect on the catenary between the bow roller and the farthest point--- I assumed you meant the anchor shank--- the chain was suspended from.

You want to hang a weight down the middle somewhere, sure, that's adding more weight to the already-there weight of the chain, so the overall catenary shape will be different.

But even then your claim is incorrect because the weight and length of the chain between the bow roller and the kellet or weight you've upt on the chain still has an effect on the curve the chain takes between the roller and the kellet.

This apparent notion you have that if you hang a weight on a chain it suddenly make the chain between the weight and the bow roller go away and so have no effect on the overal shape of the suspended chain is totally wrong. Weight's weight, and if it has a presence it has an effect.

That's one of those pesky facts again.
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Old 03-04-2015, 08:53 PM   #224
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Marin,
I went back and re read my post about the experiment. It was difficult to write w no mistakes and I made a point of getting it right as I knew you were going be critical if I dropped the ball. I got it right. Read it again please and think about it.
And I didn't say anything about putting weight in the middle of the line.
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Old 03-04-2015, 09:04 PM   #225
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A boat at anchor is not a static event......
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Old 03-04-2015, 09:42 PM   #226
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Mike, one more question, any experience with wind changing direction 180 deg? Typically we go from an onshore to offshore breeze overnight and wake pointing in the opposite direction. I don`t dive and photograph the Sarca so can`t say if it resets. Do you think the Anchor Buddy has any effect or issue in that situation?
Bruce,

I can't remember a 180 degree change while on the anchor, but that said there have a been a few ocasions when retrieving the anchor buddy that I have had to untwist the line from the anchor chain. Not sure if this was just swinging at anchor during the night, but it was still not really a drama to retrieve it.

So based on my experience to date I can't really help with your question.
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Old 03-04-2015, 09:44 PM   #227
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[QUOTE=manyboats;313621Read it again please and think about it.
And I didn't say anything about putting weight in the middle of the line.[/QUOTE]

Your point about putting a weight at an asymetrical point on the line and the line changing agnle between the weight and the two attach points is correct. I've no argument with that.

But there's nothing in the rule book that I know of that says that catenary is by definition symetrical. Catenary is the sag in the line, period. What I take issue with is your apparent claim that the portion of the line that is at a steeper angle is not contributing to the overall catenary (sag). This is not correct. Every inch of line between the two suspension points is having an effect on the shape of the catenary, whether you hang a weight on the line or not, and where you hang it if you do.

If you hang a weight on a rope rode down near the anchor, sure, it will reduce the angle of pull on the anchor. Depending on the amount of pull on the rode and the weight of the weight, there is an optimal place to put it to reduce the angle of pull on the anchor as much as possible. Go either side of that point and the angle of pull on the anchor shank will begin to increase again. I have no idea how to arrive at that point.

Because an all-chain rode is so much heavier than a rope rode, it helps eliminate the need for a separate weight to be hung from the rode. Not that a wieght hung from a chain rode won't help lower the angle of pull; weight's weight so making the rode heavier in the middle or wherever will encourage it not to be pulled up higher by the boat pulling on it.

But the point at which the angle of pull becomes high enough to be concerned about will be arrived at a lot later with an all-chain rode than with a rope rode with no supplimentary weight on it. Which is my sole reason for prefering an all-chain rode over a rope rode or mostly rope rode for our boat.

This catenary thing not some new secret. It's so obvious even my dog knows about it. I''m simply saying that the entire suspended length of a rode, rope or chain, weight hung on the rode or now weight, and regardless of where that weight is hung, has an effect on the overal catenary (sag, curve, pick your term) of the rode. Including the part that has a steeper angle than the rest of it.

It's at that angle for a reason and in the overall scheme of things, that reason is important to the rest of the equation.
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Old 03-04-2015, 09:52 PM   #228
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I have dived my anchor, and my conclusion is that under most circumstances even with normal tide and wind shifts (no current) the chain will lie on the bottom in the position that you laid it. AND that the anchored boat will not generate enough force on the rode to move the chain in any new angle of pull for more than the first couple of feet on the boat end. The chain weight replaces the anchor until enough force is applied to the rode to straighten the whole thing out. That often doesn't happen during a night in a decent anchorage.

Lots of really great topics being covered in this thread.
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Old 03-04-2015, 10:08 PM   #229
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I have dived my anchor, and my conclusion is that under most circumstances even with normal tide and wind shifts (no current) the chain will lie on the bottom in the position that you laid it..
I've never dived on an anchor, but my observation of what's going on based on the angle of pull on our long, V-bridle snubber which extends quite a ways under the water bears out the comments in your post. We all boat in pretty protected waters in this region and we anchor in pretty protected anchorages most of the time.

When the wind picks up the angle of the snubber out from our boat definitely gets shallower, but it has never pointed from the boat to the anchor. The closest it gets is when we set the anchor, but even then I suspect there is stil a lot of catenary (sag) in the all-chiain rode.

Now we have observed on windy days the combinatino rodes from boats that have them at a very shallow angles of departure from their bows and they DO seem to be pointing straight at their anchors, although even these rodes probably have some sag to them.

But I think your post is a good dash of reality in what tends to be a largely armchair theory discussion.
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Old 03-04-2015, 11:13 PM   #230
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Marin,
It does get complicated but not overly so. With the boat anchored place additional weight like a big Kellet close to but above the water on your anchored boat and I believe the angle of the rode near the anchor will actually increase rather than decrease. Chew on that one for awhile.
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Old 03-04-2015, 11:25 PM   #231
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A boat at anchor is not a static event......
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Old 03-04-2015, 11:51 PM   #232
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Marin,
With the boat anchored place additional weight like a big Kellet close to but above the water on your anchored boat and I believe the angle of the rode near the anchor will actually increase rather than decrease.
I agree. That's why I said in my previous post that the position of the extra weight, kellet,whatever, is important. Otherwise it will make matters worse.

It's got to be far enough down to lower the angle of pull on the anchor, but not so far down that the majority of the rode is being pulled up at a sharper angle again.

I don't know how to find that spot but there is one.

Which is a component of the reason we prefer an all-chain rode. It's natural catenary helps reduce the angle of pull at the anchor without the need to accurately position an extra weight as one has to do to lower the angle of pull on the anchor with a rope rode.

If it blew hard enough, and depending on the six zilliion variables like bottom composition, anchor type, how well the anchor had dug in, etc. a weight might be beneficial on an all-chain rode, too. But it would have to be blowing pretty hard and the boat surging pretty significantly for that to become necessary.
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Old 03-04-2015, 11:54 PM   #233
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If people anchoring in the PNW wonder if their boats swing around over night I can say that they definitely do and even without wind shift which is common in PNW overnight there is that 12 foot tide change you know water goes one way than the other.. When I use two anchors I almost always have a few wraps to undo in the morning and there is no way they can get there except by the boat turning around.
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Old 03-05-2015, 12:09 AM   #234
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Fairly sure the use instructions(googled them a while back) for the Anchor Buddy, are to slide it down, attached to the rode using the provision on the AB to do that, and position it just off the bottom at low tide.
Does that fit with using a catenary, I think it might be a little different in that it seeks to place weight on the rode straight down, with the rode lying virtually flat from AD to your choice of anchor. A wind loading could make it more a catenary, maybe temporarily. Must try my AB, it came with the boat.
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Old 03-05-2015, 12:24 AM   #235
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Since we're almost 1/4 of the way to 1000 posts on this subject, let's spice it up a bit

Nobody has mentioned polyester rodes yet.

Polyester has a higher breaking strength compared to manufacturers specifications for a given size, but...now wait for it...polyester doesn't lose up to 20% of its strength when wet like nylon does.

Found this bit in an abstract for a paper presented to a Civil Engineering conference;

Fiber Ropes For Ocean Engineering in the 21st Century http://www.tensiontech.com/papers/pa.../deep_mor.html

"Nylon, also known by its chemical name polyamide, has been widely used in marine mooring and towing lines since the 1950s. It has the lowest stiffness mod ulus, and thus it is favored where high extension is very important. It is the strongest of the common fibers when dry. However, wet nylon fiber loses about 10% of its strength, and wet nylon ropes can lose up to 20% of their strength. Wet nylon ropes also suffer strength loss due to creep and internal abrasion during tension cyclic loading.(Flory, 1982) The resulting short service life of large nylon ropes generally makes them unsuitable for permanent deep water moorings.

Polyester ropes are very durable in cyclic tensile fatigue loading.(Parsey, 1982, 1985) Very strong polyester rope with relatively high modulus can be made with the newer high-quality polyester fibers now available. They can be as strong as nylon when dry. Polyester ropes do not lose strength when wet and are generally stronger than nylon in wet condition. Thus polyester ropes are now supplanting nylon in many critical conventional marine applications and are good candidates for deep water mooring systems."


For north coast BC waters (similar to SE Alaska) I'm leaning towards 100 feet of chain followed by 500 feet of 8 strand polyester, probably with a nylon snubber/bridle using a soft shackle and Kleimheist knot.
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Old 03-05-2015, 12:49 AM   #236
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More on polyester: http://www.bethandevans.com/pdf/dashew-right-rode.pdf
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Old 03-05-2015, 12:56 AM   #237
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...and from MIT: http://pdos.csail.mit.edu/decouto/my...s/seagrant.pdf
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Old 03-05-2015, 02:14 AM   #238
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Murray,

If you really want to expand your education on anchoring, instead of repetitive opinion, google "drag enbedment anchor".

There is loads of scholarly papers out there about this topic.
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Old 03-05-2015, 03:35 AM   #239
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Part of the optimum scope, is also knowing (seeing) what's in your swinging room. We like anchoring at low tide. It gives you a better sense of what's under you. More than once, after coming in at high tide and then looking around at low tide...yikes! Then you see that rock pinnacle or shallow area that was missed or wasn't on the charts.

This Selene was anchored near Ketchikan in July 2010 when they missed judged the tides.
oops

Been there; Done that
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Old 03-05-2015, 03:44 AM   #240
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There are many reasons a mixed rode is useful. I have one and can make more. I'll use one for my stern anchor this summer.

But I am still perplexed, therefore I have a simple question.

For those of you who advocate mixed rodes as the primary, whether it's poly, wet or dry nylon, or cat's guts, you do understand that it is the weight of the chain which keeps the neck of the anchor on the seabed floor?

The more chain you put out, the heavier the weight, the more inclined your anchor is to stay imbedded.

A simple yes or no would suffice.

As unlike things like anchors, where the data is varied, this is simply physics.

Do they teach that in school nowadays?
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