80# Manson Supreme Surprise!

[noelex 77]

Originally Posted by foggysail

The GPS is located about 25 ft from the bow.
And yes the movement was slow. I noted that the boat seemed to slip right after the wind change. I first checked the GPS around midnight, we moved the boat sometime around 8-8:30AM. The wind change looking at the GPS was about 180 degrees.

I think if the wind shift was 180 degrees the anchor did not drag at all. The boat just swung around the stationary anchor.

With a 180 degree wind shift (and a gps 25 feet from the bow) you should have moved almost (60+25)x2=170 feet on the GPS from your initial position with no dragging of the anchor.

The movement you saw was just the chain slowly moving through the weed, which is what I would expect with 25k average and a weedy anchorage.

[Jim Cate]

Originally Posted by noelex 77

I think if the wind shift was 180 degrees the anchor did not drag at all. The boat just swung around the stationary anchor.

With a 180 degree wind shift (and a gps 25 feet from the bow) you should have moved almost (60+25)x2=170 feet on the GPS from your initial position with no dragging of the anchor.

The movement you saw was just the chain slowly moving through the weed, which is what I would expect with about 25k and a weedy anchorage.

This sounds about right to me. Really hard to believe dragging under such mild conditions.

Cheers,

Jim

[foggysail]

Originally Posted by noelex 77

I think if the wind shift was 180 degrees the anchor did not drag at all. The boat just swung around the stationary anchor.

With a 180 degree wind shift (and a gps 25 feet from the bow) you should have moved almost (60+25)x2=170 feet on the GPS from your initial position with no dragging of the anchor.

The movement you saw was just the chain slowly moving through the weed, which is what I would expect with 25k average and a weedy anchorage.

Come on Noelex, that is nonsense! No way would I have moved if I felt safe. As I mentioned above, I will try to post a picture of hte GPS later tonight after I get home.

[cheoah]

Goes to show that equipment is only part of the picture. A properly set anchor will beat any other brand in a blow.

Those conditions sound tough for any anchor and easy enough to go light on the scope. I think that is pretty common for people to aim for 4 or 5:1 but forget to add some for all the aforementioned factors. I just shoot for 7:1 and don't worry my pretty little head over all that complicated math. My iPhone does my thinking for me when I'm on vacay

[noelex 77]

Originally Posted by foggysail

Come on Noelex, that is nonsense! No way would I have moved if I felt safe. As I mentioned above, I will try to post a picture of hte GPS later tonight after I get home.

In 180 degree wind shift the GPS will move almost 170 feet with the parameters you have described without any input from you.

Anchoring does not fix you in one position.

With 25k of wind in a weedy anchorage this will happen slowly, as you have described.

The GPS trace would help decide if you did really drag. If I understand your description of the events correctly I suspect that is not the case.

The moored sailboat and fishing box will move far less in a wind shift. Swinging too close to them does not indicate you dragged. Just that you moved and they did not (much). As I would expect.
It is a common problem when anchoring with moored boats nearby.

Surely it is good news if your anchor was doing what it should do under these conditions

[Cheechako]

Originally Posted by cheoah

Goes to show that equipment is only part of the picture. A properly set anchor will beat any other brand in a blow.

Those conditions sound tough for any anchor and easy enough to go light on the scope. I think that is pretty common for people to aim for 4 or 5:1 but forget to add some for all the aforementioned factors. I just shoot for 7:1 and don't worry my pretty little head over all that complicated math. My iPhone does my thinking for me when I'm on vacay

Yeah, In the Bahamas I usually just put chain out to the 90 ft mark.... even though most often in 13 ft of water or so. some where between 5 and 10:1 works!

[foggysail]

I will not be able to post a picture...if I can at all .. until later tonight. But this is for thoughts--

The slip was towards SW but consider just GPS latitude change for example. The position when I noticed the boat had slipped after a latitude start of 41 25 597N and the reading when I decided to move the boat was 41 25 585N.

1 second = 1 nautical mile
1 nautical mile= 6076 feet

The delta between my two lat readings is |585-597| = 0.012 seconds.

The change in position (slip) between the 8AM and the midnight reading is:
6076 X 0.012 = 73 feet.

Now granted, there was also some small change in the longitude which I ignored. And sure, 73 feet of slip might not mean much in most cases. My situation commanded that I move the boat.

And finally I accept the fault of not forcing that anchor deeper when it first set along with not increasing the scope later. I dared not increase the scope after all the slipping occurred. These two factors could have impacted the slippage.

Foggy

[Tim R.]

Foggy, if you feel you cannot lie at the proper scope, at least set the anchor with the proper scope just to be sure it is set. Then reduce scope to your comfort level.

[foggysail]

Noelex--

This is my first try attaching a photo so it could flop. If the picture of my GPS posts, notice that it resembles a sickle. The top of the blade part is where I roamed after the anchor first set.

The handle part of the sickle is where the boat slipped, gradually but slipped never the less.

My other pictures with the location arrow moved to the higher latitude at the top of the handle is blurred. In any case, those two points, the handle top latitude reading and teh handle bottom reading are the numbers in my above post where I calculated the slip via the delta latitude. This should help understand where he numbers came from.

Notice the bottom of the blade section in the attachment. This is where the wind was changing from out of the SW to the NE. In the attachment, north is at the top.

Foggy

[sailorchic34]

Does look like a little slippage right at the start of the blow and then the boat pivoted more or less around that reset point with just a bit more movement.

Hum. isn't it 1 minute per NM, not 1 second.

So what sort of snubber were you using?

[foggysail]

Originally Posted by sailorchic34

Does look like a little slippage right at the start of the blow and then the boat pivoted more or less around that reset point with just a bit more movement.

Hum. isn't it 1 minute per NM, not 1 second.

So what sort of snubber were you using?

Yeah, of course 1 minute is a NM, typo. Consider this partial quote from above

"The delta between my two lat readings is |585-597| = 0.012 seconds."

I use a chain hook attached to about 10' of 1/2" nylon three strand. But a snubber in this has questionable value with the wind holding constant 25 plus. The chain looked like a rod.

And yes, there could have been slippage at the very start of the blow, I first thought there was. After the boat stabilized... at the sickle handle, that was where my concern became acute. There is no doubting that slippage which I measured via the lat readings at both ends of the handle.

Bottom line, I will never short change setting in the future regardless of weather reports, Second I will reach for as much scope as the particular situation will allow me. Heck, it slipped some 70 or so feet over an 8 hour period. More scope alone might have been the answer.

One gets spoiled using short scopes over and over with never a problem with a well set anchor.

[jigray3]

Originally Posted by Tim R.

Actually less than 5:1 at high. What is the distance from the surface to the anchor roller? Let's assume 5' and 60' of chain. That would be 4:1. Gets a little more scary if only 50' of chain and 6' at the roller; just over 3:1.

how much was your bow moving vertically in that 2' chop? I bet the chain was taught so the weight of it was useless and the bow at it's highest reduced your scope even more. The bow bobbing up and down at a potential 3:1 scope or even 4:1 scope would be too much for most any anchor in that blow and your high windage. Your anchor was probably set below the grass bed but never bit into the mud because of the limited scope.

The simplest answer is usually correct. If the OP did not have out enough scope, that's the first place I'd look. You never give the anchor a chance in those conditions without adequate scope, no matter how good the anchor. I always look for 7:1 or greater. Always. That's one of the things I can control when there are so many other aspects I can't, why on earth risk it.

[Bash]

Originally Posted by Tim R.

Foggy, if you feel you cannot lie at the proper scope, at least set the anchor with the proper scope just to be sure it is set. Then reduce scope to your comfort level.

In other words, always start with a proper set.

(The key word here is "always.")

[foggysail]

I believe we all learned something from my thread. Unfortunately there ARE times when proper scope is impossible to apply in crowded anchorages. This time, it was my fault. There were obstacles such as moorings to avoid but I could have and looking back should have employed greater scope.

I still believe had I set the anchor properly during me initial setting, that may have helped avoid the situation that later followed. Got to chin up, poop does happen. It was worth my sharing this event in any case!

Foggy

[CarlF]

While more scope and a good set are great answers, I'd have also used a snubber with more stretch.

"Bar taught" chain means that snubber is the only thing taking the shock load off the anchor as the boat moves at anchor. Each wave is a shock. And a boat that "tacks" at anchor will briefly double the load on the anchor rode at the end of each tack.

A longer and smaller diameter snubber (maybe 25ft of 3/8" or 7/16" nylon) would have stretched much more and might have prevented the dragging.