Anchoring

[MontyMariner]

We noted transits and - something nobody has mentioned yet - we used our ears. The sound the chain makes if an anchor is dragging is different to the sound it makes if the chain is being re-arranged on the bottom.

Your situation must be a bit different to mine.
No night vision bins so I can't see the transit at 3 in the morning.
I use a snubber so the chain noise is attenuated.
And I sleep (soundly) in the aft cabin so I can't hear it anyway!

 

[Snowgoose-1]

Saving this one for something special
https://www.wavsource.com/snds_2020...03/tv/simpsons/homer/run_for_your_lives_x.wav

Brilliant !

 

[john_morris_uk]

Ouch I was taught (in cars, planes & boats) to be a bit more mechanically sympathetic. Presumably you've got a windlass bolted to cast iron metalwork in your boat

Indeed. I’d also be worried about the windlass bearings.

 

[GHA]

Indeed. I’d also be worried about the windlass bearings.

Would you really prefer not to know if your anchoring system was strong enough or not? Go cruising one day it might have to save your boat in extreme conditions, far better imho to have enough confidence that it's up to the task, if your scared it might break it's not strong enough.

Not a good idea to put extreme loads on the windlass, it's not designed for that.
Anchoring

 

[Chiara’s slave]

I’ve just bought some 10mm stainless chain to replace the rusty 8mm 2 metre length on my Spade. I will probably still not use an alarm.

 

[john_morris_uk]

Would you really prefer not to know if your anchoring system was strong enough or not? Go cruising one day it might have to save your boat in extreme conditions, far better imho to have enough confidence that it's up to the task, if your scared it might break it's not strong enough.

Not a good idea to put extreme loads on the windlass, it's not designed for that.
Anchoring

We live the vast majority of our time on our anchor. I’m very confident in our anchoring system. (Spade anchor on 95 metres of 10mm chain.)

We have a chain hook on a length of nylon three strand rather than leave the load on the windlass.

I invariably reverse at half power to check the anchor is dug in. It very rarely doesn’t stick first time.

I’m not going to start putting shock loads as you describe on our windlass. I value our windlass bearings too highly.

Each to their own I guess.

 

[GHA]

We live the vast majority of our time on our anchor. I’m very confident in our anchoring system. (Spade anchor on 95 metres of 10mm chain.)

We have a chain hook on a length of nylon three strand rather than leave the load on the windlass.

I invariably reverse at half power to check the anchor is dug in. It very rarely doesn’t stick first time.

I’m not going to start putting shock loads as you describe on our windlass. I value our windlass bearings too highly.

Each to their own I guess.

Have a read of post 96 given in the link. The load is not on the windlass. It takes just a moment and a tap on the chain with a toe to slot it into a substantial chain grab welded to the deck & take any load off the windlass. Really useful, living on the hook the windlass is a pretty vital piece of kit & treated with care. Handy if the chain ever jams on the windlass as well.
Similar to one of these but with the slot fixed & pointing upwards. And far, far stronger. And cheaper, cost nothing using 12mm stainless flat bar offcuts.

Do you have a secondary connection to take the load when the snubber breaks? Worth considering, go cruising long enough it will, in a 60Kt gust at 3am.....

 

[john_morris_uk]

Have a read of post 96 given in the link. The load is not on the windlass. It takes just a moment and a tap on the chain with a toe to slot it into a substantial chain grab welded to the deck & take any load off the windlass. Really useful, living on the hook the windlass is a pretty vital piece of kit & treated with care. Handy if the chain ever jams on the windlass as well.
Similar to one of these but with the slot fixed & pointing upwards. And far, far stronger. And cheaper, cost nothing using 12mm stainless flat bar offcuts.

Do you have a secondary connection to take the load when the snubber breaks? Worth considering, go cruising long enough it will, in a 60Kt gust at 3am.....

Understood re dropping the chain into a slot as described.
Yes we have a secondary connector. We have one of those exactly as pictured in your post.

I’m still not convinced re your slightly bizarre technique of setting the anchor and checking its hold with a snatch from the boat driving backwards. Each to their own.

 

[GHA]

I’m still not convinced re your slightly bizarre technique of setting the anchor and checking its hold with a snatch from the boat driving backwards. Each to their own.

Not bizarre at all, just creating the loads which can happen if some unforecasted nasty weather comes through to confirm the holding is actually sufficient. Very reassuring knowing it's available. Half revs won't tell you much, why treat your anchor with kid gloves?

Wouldn't trust that chain grab tbh, 2 M5 or 6 fasteners in shear? Too scary for me

 

[john_morris_uk]

Not bizarre at all, just creating the loads which can happen if some unforecasted nasty weather comes through to confirm the holding is actually sufficient. Very reassuring knowing it's available. Half revs won't tell you much, why treat your anchor with kid gloves?

Wouldn't trust that chain grab tbh, 2 M5 or 6 fasteners in shear? Too scary for me

I think you’re seeing ghosts where there are none.

So if conditions spring a surprise on us and if my snubber breaks and if I then rely on my chain lock on deck the 6mm bolts might shear.

Firstly they’re not in pure shear. Draw the vector of forces and you’ll see it’s a mixture of shear and tensile. A quick google shows the tensile strength of two M6 to be over 2 tonnes. Difficult to accurately assess the actual breaking strain in the situation as you can’t tell how much the leading edge of the device will dig in and act as a pivot.
Another quick google shows that’s far in excess of the max pull of our Spade anchor in a decent bottom.

I think I’ll stick with reality. I’m confident my snubber is unlikely to break and even if it did, the Spade anchor would be slowly ploughing its way backwards before breaking two 6mm bolts.

 

[GHA]

I think you’re seeing ghosts where there are none.

So if conditions spring a surprise on us and if my snubber breaks and if I then rely on my chain lock on deck the 6mm bolts might shear.

Firstly they’re not in pure shear. Draw the vector of forces and you’ll see it’s a mixture of shear and tensile. A quick google shows the tensile strength of two M6 to be over 2 tonnes. Difficult to accurately assess the actual breaking strain in the situation as you can’t tell how much the leading edge of the device will dig in and act as a pivot.
Another quick google shows that’s far in excess of the max pull of our Spade anchor in a decent bottom.

I think I’ll stick with reality. I’m confident my snubber is unlikely to break and even if it did, the Spade anchor would be slowly ploughing its way backwards before breaking two 6mm bolts.

Down to you. I like a huge factor of safety, the universe doesn't always act like you expect or want it to.

Draw the vector force analysis & you'll see the horizontal component will all be taken in single sheer by the 2 fasteners - your "but the leading edge will dig in & hold the boat" is 100% conformation bias & 0% structural analysis. from memory rule of thumb for single sheer is about 60% of tensile?. Add the factor of safety for structural fasteners again from memory commonly something like 8.5:1? & suddenly it's not that great @ 70Kg each....
Suspect I may well be much more risk averse when it comes to the boat staying off the beach than others. Checking things actually work under extreme loads really isn't bizarre to me. Just reassuring
Our boats, our decisions. Pretty unlikely your snubber will go, pretty likely the chain grab will hold so hope it never gets tested.

Edit: Yum yum, this humble pie is tasty Checked on force 4, 2 X M10 fasteners for 8/10mm chain. Much more like it.

Size: 85mm (W) x 79mm (L) x 61mm (H)
Fixings: M10 x 2
Chain size: 8 - 10mm

 

[Humblebee]

Pete Smith designed and made (in the early days) the Rocna anchor.

You may find this and his other thoughts on anchoring use and design helpful
petersmith.net.nz/boat-anchors/catenary.php

Interesting, thanks for the link.

 

[GHA]

Not bizarre at all, just creating the loads which can happen if some unforecasted nasty weather comes through to confirm the holding is actually sufficient. Very reassuring knowing it's available. Half revs won't tell you much, why treat your anchor with kid gloves?

For anyone heading off cruising - just came across this which is why the experienced full time cruisers do what they can to get some evidence that anchor is well dug in & can keep the boat where it is before going ashore. Half revs might actually be worse than nothing at all by giving a false sense of security..

 

[Stemar]

Half revs might actually be worse than nothing at all by giving a false sense of security..

That's what caught me out the one time I dragged; the boat stopped smartly as the chain went tight, so I thought I was well dug in. Now I give it plenty of welly.

 

[westernman]

When the norm for us might be half the distance from shore that ypu deep keel people are, you don’t need to use a bearing compass. It’s bloody obvious if you’re dragging. My favoutie kind pf anchorage is to bury the hook myself on the beach.

How does that work when the wind turns?

 

[GHA]

I think I’ll stick with reality. I’m confident my snubber is unlikely to break and even if it did, the Spade anchor would be slowly ploughing its way backwards before breaking two 6mm bolts.

Can't let that one lie
It is 100% NOT reality but 100% your conformation bias. (not you, it's everybody, it's what our oversize monkey brains do, evolutionary benefits)
Rather than feel the discomfort of having your belief in the strength of the snubber challenged you ran round the house to find something, anything, to make that discomfort go away rather than keep an open mind and have a really good look at reality.
And you were 100% wrong, M6 is too small. They use M10. Every day's a school day, keep an open mind and look deep.

 

[lustyd]

just came across this which is why the experienced full time cruisers do what they can to get some evidence that anchor is well dug in & can keep the boat where it is before going ashore

You’re implying that these guys aren’t experienced cruisers?

 

[GHA]

You’re implying that these guys aren’t experienced cruisers?

anchoring like that then "experienced full time cruisers" - no. Or maybe just lucky.
Certainly not worth listening to when it comes to anchoring. Lets not beat about the bush imho.

 

[lustyd]

anchoring like that then "experienced full time cruisers" - no. Or maybe just lucky.
Certainly not worth listening to when it comes to anchoring. Lets not beat about the bush imho.

They’ve lived aboard for 7 years or so and crossed the Atlantic a few times. They’re in a completely new boat in a new location and got unlucky, no need to be a git about it. They’d been there two full days before dragging so didn’t just jump off and go to the pub as you imply.
All real experienced sailors have dragged. If you have not the. You’re either lying about dragging or lying about your experience.

 

[capnsensible]

They’ve lived aboard for 7 years or so and crossed the Atlantic a few times. They’re in a completely new boat in a new location and got unlucky, no need to be a git about it. They’d been there two full days before dragging so didn’t just jump off and go to the pub as you imply.
All real experienced sailors have dragged. If you have not the. You’re either lying about dragging or lying about your experience.

Dunno really why people get their knickers in a knot so much anbout anchoring. Seems to have been a common theme on here for decades!

It's generally very easy. Few people drag under normal circumstances. Lots like to talk about impending doom though....