Leaving boat at anchor - worried?

[Dockhead]

Originally Posted by msponer

I don't worry at all about dragging, but that's because my setting ritual is ridiculously over the top. My wife is too polite to say anything, but I'm sure I annoy her. However, this ritual has kept me from the little kind of insanity I sometimes develop while sailing, of thinking something over and over again "are we going to drag?" or "what is that knocking sound coming from the engine?" or etc.

My ritual is to gradually back down and set the anchor while feeling the chain with my hand or bare foot and watching the boat relative to landmarks on shore. My wife gradually increases throttle to about half or three quarters, we even have hand signals for where to set the throttle since she can't tell from the cockpit when the anchor is dragging across the bottom, starting to dig in, or is buried up to the shank. And this is the ridiculous part -- once I can feel that the anchor is buried, we leave it at high throttle in reverse for five or ten minutes, pulling several feet of the chain straight out of the water and making little tidal overfalls in the wind waves from our reverse thrust while I continue feeling the chain for the scraping or skipping thing it does when the anchor pulls out. It's common for it to set and then start dragging again at 1800 or 2000 RPM, and my idea (unless the waves are up and adding load) is usually something around 2500 RPM. If it holds at 2500 RPM for ~5 minutes, I know it's usually completely buried (so that only the chain is visible when we snorkel on it), and that it'll hold up to pretty rare conditions in the anchorage.

Anyways, we do that -- take the setting and checking the set to a ridiculous extreme -- and then don't worry about it again. If I don't follow this ritual it's always in the back of my mind.

I don't think it's over the top, much less "ridiculously over the top".

I don't think you need 10 full minutes at full power backing down, but otherwise what you describe is what I consider to be good practice, and what I do myself.

Hint: a chart plotter set to read SOG and with track on will be more accurate than visual transits to shore landmarks. You can see very, very well on the plotter whether the anchor has really set or not -- the boat will swing around a bit, SOG will be only in the direction of swing, and when the boat stops swinging, SOG will hit 0.00 knots and you know for sure you're stuck to the seabed. If you're dragging even the slightest bit, you immediately see it.

After reaching that point, I use full power for maybe 2 or 3 minutes, which I think is plenty after 10 minutes or so of gradually increasing the force as the anchor sets. This is good for your engine -- a little full power run to blow the carbon out. Just make sure to let idle without load for a while to let turbo bearings cool off afterwards, if your engine is turbocharged like mine is.

[cat man do]

I used to worry a lot on my last cat
I am hoping the setup on the new one will take those worries away.

8700kg displ cat with:
100lb supreme
70m of 10mm chain
and a big Maxwell HWC 2200 (2200lb lift) to get it all back

[msponer]

Originally Posted by Dockhead

I don't think it's over the top, much less "ridiculously over the top".

Thanks -- well I can't be that weird if someone else does it.

Watching other people anchor is usually boring, and feels a bit curmudgeonly -- like the only thing that could possibly come out of it is me talking to myself like I'm on a sailing forum, or worse, pontificating to my wife and kids about someone else's technique -- so I don't have a good sample, but I've never seen someone else back down for more than a quick tug, or anywhere near the long sustained backwards pull that I do: thus I am just assuming it's rare. And evidently ridiculous, since the 'quick tug' folks do not drag often enough to start setting their anchor better.

Though I remember in Tahiti lots of folks let their guard down after weeks of mellow weather inside a well protected harbor, and then there was a mass dragging when a rare squall blew through. So that's our accompanying evolution, that this seamanship stuff is easy to learn, but the hard part is making yourself always do it (anchor well, clip on, mouse shackles, check the fuel filter, whatever).

[Matt Johnson]

Dockhead,

You're just paranoid from reading all the threads on this site. After way too much reading on the subject myself, I was so paranoid that I sold my 35lb Manson for a 55lb Rocna. I'm sure I would have been fine with the 35lb, but all the horror stories started keeping my up at night. Sure, I never worry about the boat dragging now with the 55lb, but if my windlass ever fails, I'll really regret that choice.

Enjoy the sites and your cruising grounds. The boat will be there when you get back!

[noelex 77]

Originally Posted by msponer

Watching other people anchor is usually boring, and feels a bit curmudgeonly --

It's great free entertainment

It does have a practical purpose. If you have good gear and technique the most common problem is other boats dragging into you. It worth knowing how the boats around you are anchored.

[noelex 77]

Originally Posted by funjohnson

Sure, I never worry about the boat dragging now with the 55lb, but if my windlass ever fails, I'll really regret that choice.

With most boats it is possible to rig a system to raise the anchor with sheet or halyard winches, but its worth at least thinking about the system beforehand if your anchor is too heavy to manage by hand.

Know how to bypass the anchor winch solenoid and you will be able to temporally fix 80% of anchor winch failures.

Also think about how you would ditch all the chain and anchor, with a buoy for later retrieval, in the event of an emergency.

[rebel heart]

It is worth pointing out that most people have no f'n clue what they're doing and make it by just fine a lot of the time.

Sort of like scuba diving. I'm amazed there aren't more fatalities.

[noelex 77]

I think it depends what part of the world you are in. Some locations with good holding and light winds are very forgiving, but I see far far more damage from boats dragging anchor than any other cause.
Fortunately fatalities or serious injury are rare, but lots of accidents and damage to boats.

People don't manage just fine in my experience. They get into trouble and often.

[rebel heart]

Originally Posted by noelex 77

I think it depends what part of the world you are in. Some locations with good holding and light winds are very forgiving, but I see far far more damage from boats dragging anchor than any other cause.
Fortunately fatalities or serious injury are rare, but lots of accidents and damage to boats.

People don't manage just fine in my experience. They get into trouble and often.

Yikes.

I'm in the horse latitudes around here. Minus low pressure systems rolling through, this area is pretty simple.

What kind of bottom surface are you normally in? Is it just general not enough scope problems, not setting the anchor, etc?

[donradcliffe]

Originally Posted by msponer

I like the Pardey quote.

No, I don't do the full ritual if it's just a quick stop. But then I do have that 'could drag' awareness that is not as condusive to just completely relax: I still feel a bit at sea, in that mindspace, and would not, for example, drink a lot of beer or go ashore out of sight of the boat.

I back down with the chain on the windlass, so that I can feel the vibrations in the chain. It's somewhat bad for the windlass, the one on our last boat was a bit warbly after a few years (though it still worked fine, the capstan did not rotate in a straight line). If there's a short chop the loads are a lot higher, so I tie the snubber just in front of the windlass, leaving the chain under load where it passes through the bow roller. Then I can still feel what the anchor is doing through the chain while we set it, and then once we are done I let the rest of the length of the snubber out through the bow roller.

I use a chain stopper and back down first, then set the snubber. I agree that backing down with your foot on the chain gives you a lot of information that you lose when you put the snubbber on--the rumbling of chain on rock, the little jump when the chain gets tight, feeling the chain get bar tight when the anchor is well set, and more.

If I put my current engines in full reverse, I'd probably break something. I calculate the bollard pull at over 10,000 pounds with 400 hp and two 26" props. If I backed down the sailboat with a single 20" prop, its bollard pull calculates about 2000 lbs at full 55 hp. Interestingly, that's about what Practical Sailor measured as the peak snatch load on a 35 ft cat or 45 ft mono at 60 knots.

[noelex 77]

Originally Posted by rebel heart

Yikes.

I'm in the horse latitudes around here. Minus low pressure systems rolling through, this area is pretty simple.

What kind of bottom surface are you normally in? Is it just general not enough scope problems, not setting the anchor, etc?

I think a lot has to do with the bottom conditions. Mud, or soft sand is very forgiving. In these conditions most anchor designs set well and will usually set on there own if they are not set properly when dropped. This does not happen in hard sand or weed.
The other factor is wind strength. Below 20-25K very few boats get into trouble. A poorly or even un-set anchor will generally hold in these conditions with the drag of the chain and anchor.

A simple statistic that has held true for the last 5 years of cruising in mostly difficult anchoring conditions is that if the wind once the wind strength reaches 25k (average) 50% of the yachts in the anchorage will drag.
About 50% of those that drag are due to just bad technique. The other 50% are due to inadequate anchoring gear.

[noelex 77]

Originally Posted by donradcliffe

If I backed down the sailboat with a single 20" prop, its bollard pull calculates about 2000 lbs at full 55 hp. Interestingly, that's about what Practical Sailor measured as the peak snatch load on a 35 ft cat or 45 ft mono at 60 knots.

There is a lot of dispute about anchoring loads. The figures are widely disparate from different sources
I Snorkel most days over the warmish months and the anchor generally starts to bury deeper if the average windspeed has been over 30k. I set with gradually more power finishing at full reverse.
The anchors behaviour sugests to me the peak loads on the anchor in wind above 30k is higher than I can generate with the motor alone.

[Dockhead]

Originally Posted by funjohnson

Dockhead,

You're just paranoid from reading all the threads on this site. After way too much reading on the subject myself, I was so paranoid that I sold my 35lb Manson for a 55lb Rocna. I'm sure I would have been fine with the 35lb, but all the horror stories started keeping my up at night. Sure, I never worry about the boat dragging now with the 55lb, but if my windlass ever fails, I'll really regret that choice.

Enjoy the sites and your cruising grounds. The boat will be there when you get back!

LOL. I'm not paranoid from reading CF. I'm paranoid from 15 years of cruising with a CQR

I do think that backing down for a while at full power - AFTER the A
anchor is set - is essential basic practice. A quick tug is not enough, no matter how good your anchor is.

[conachair]

I've never quite understood why so much time and effort is spent on anchoring technique. Most of the time you won't be there or will be asleep during a tide change or wind shift. Why not spend lots of time and energy once on making sure your set-up can look after itself rather than coaxing it into the seabed every time you drop the hook?

In a 5 month period in a tidal anchorage mine reset itself about 600 times without any outside help Makes leaving the boat a bit less stressy knowing it can look after itself.

[noelex 77]

Modern anchors stay set with a change in direction of pull. They often develop a slight list but remain buried as they rotate around. (Assuming the force is great enough to rotate the anchor. Often a tide shift is not enough force on its own to rotate the anchor )

The key is once its set it will generally stay set even with a 180 degree change.


If not set in the first place this is a very different situation.