Storm Anchoring

[Mike OReilly]

Originally Posted by kmacdonald

You might want to consider a diet.

You been talking to my doctor?

[Simi 60]

Originally Posted by rslifkin

You're probably heavier relative to your windage. So your boat likely produces less shock load in gusts.

The 80 knot event deformed 13mm chain.
Admittedly then, it was a 25mm silver rope snubber, not nylon.

[kmacdonald]

Originally Posted by Mike OReilly

You been talking to my doctor?

We're in the same boat.

[kmacdonald]

Be sure to anchor off the stern in storm conditions. Sailboats only.

[Dockhead]

Originally Posted by Jim Cate

Actually, UHMWPE is ultra high molecular weight POLYETHYLENE, DH! If you are gonna flaunt high tech vocabulary, ya oughta get it right!
Jim

Right, of course. Thanks.

[Dockhead]

Originally Posted by SVRocinante

Quick question Dockhead and forgive me if it’s a stupid question, but any advice on how to tell that it’s time to replace?

We sail full time (USA East Coast) and anchor out the majority of the time - going on 4 yrs now and no snubber issues on our Hanse (40’ / 18,000 lb) plenty of “storms” but I must say, our anchorages are usually reasonably well protected, so not much in the way of constant coming up taught on the chain... perhaps 4’ swells at the worst.

I use regular 3 strand nylon from New England Ropes for the snubber(s), tubular nylon webbing for chafe guards and tie a rolling hitch onto the chain... no chafing that I can see, a bit “fuzzy” in sections where I tie, but no broken strands, etc.

Thanks for any help with this.

Not a stupid question at all. I wish someone would tell me!

I can't really tell, so just replace every year. Obviously replace if you see any signs of chafe. Nylon sometimes "work hardens" -- I think that's also a sign. But I've broken them without any of these signs, so this is not a guide.

I just recycle my snubbers as dock lines so I'm not throwing them away. They are a good length for spring lines.


And obviously try to anchor in a way that stresses the ground tackle as little as possible. In really bad weather (40+), assuming you have reasonable shelter, the biggest issue (besides chafe) is yawing, which can stress everything and also yank your anchor out. An anchor spring line or riding sail will tame that.

[Captn_Black]

Originally Posted by Simi 60

I often hear this and wonder how it is that we have not broken our 5 metre snubber (19mm nylon) on a 60fter weighing near 70 tonne?

Been through multiple 50+ and a more memorable 80+ blow without an issue apart from soiled pants.

Just because something works for you doesn't mean it is the right thing to do. 30' of the correct size is the length you need to have sufficient stretch to avoid overly stressing your ground tackle.

[Dockhead]

Originally Posted by Captn_Black

Just because something works for you doesn't mean it is the right thing to do. 30' of the correct size is the length you need to have sufficient stretch to avoid overly stressing your ground tackle.

You can get as much stretch as you want with any length of snubber, just by making it thinner. You don't need a long snubber for stretchiness, you need it long for strength


I would also avoid blanket statements applied to all different sizes and types of vessels. Heavier and larger vessels using heavier chain have less and less need for any snubber at all. On my boat with 1/2" chain, I don't need a snubber at all below about 30 knots of wind. This guy's 70 tonne boat might have little need for a snubber even in storms. It's smaller boats which bounce around a lot, where the snubber is critical. You've never seen a snubber on a ship, have you?

[Captn_Black]

Originally Posted by Dockhead

You can get as much stretch as you want with any length of snubber, just by making it thinner. You don't need a long snubber for stretchiness, you need it long for strength

Of course, but when you over stretch it then you are quickly going to work harden it. The idea of properly sizing it is to get just enough stretch without it breaking. Too big and ofc it will not stretch enough. Smarter people than me have worked out that 10m of the correct size nylon is optimal. It is not a blanket statement. For me that size is around 14-16mm. But that all depends on your ship. You could of course use a longer length of thicker nylon and get the same stretch, but then who would want a 20m snubber?

[Captn_Black]

Originally Posted by Dockhead

You've never seen a snubber on a ship, have you?

I assume you mean this as on a big ship? Rather than a general insult?
No, I have not seen a tanker with a snubber, but then the physics are different on larger scales. 3 meter waves are not the same for such a ship. Cantery alone would work fine. That said, I have worked on salvaging a broken chain and anchor from such a ship, that was lost in a storm. Just because the gear holds doesn't mean that the ground tackle set up is not being damaged.
You seem to have made a big u-turn on your previous statement s with the intent of attacking me, strange.

[Dockhead]

Originally Posted by Captn_Black

Of course, but when you over stretch it then you are quickly going to work harden it. The idea of properly sizing it is to get just enough stretch without it breaking. Too big and ofc it will not stretch enough. Smarter people than me have worked out that 10m of the correct size nylon is optimal. It is not a blanket statement. For me that size is around 14-16mm. But that all depends on your ship. You could of course use a longer length of thicker nylon and get the same stretch, but then who would want a 20m snubber?

Optimal for a boat your size, sure. The 70 tonne vessel has very, very different characteristics.


My snubbers are 10 and 15 meters. After a lot of experimentation I settled on one for lighter weather and one "storm" one. The long one is thicker.


You are right, of course, that for a given amount of stretchiness, a longer thicker snubber will be working at a lower percentage of its UBS, so will be less likely to fail. That's why too short and too thin snubbers are not a good idea. But I don't think 10m is any kind of magic number. It depends on how much stretch you need. Big boats need less stretch because they bounce around less.

[Captn_Black]

Originally Posted by Dockhead

Optimal for a boat your size, sure. The 70 tonne vessel has very, very different characteristics.


My snubbers are 10 and 15 meters. After a lot of experimentation I settled on one for lighter weather and one "storm" one. The long one is thicker.


You are right, of course, that for a given amount of stretchiness, a longer thicker snubber will be working at a lower percentage of its UBS, so will be less likely to fail. That's why too short and too thin snubbers are not a good idea. But I don't think 10m is any kind of magic number. It depends on how much stretch you need. Big boats need less stretch because they bounce around less.

I would also argue that too much stretch would increase horsing, which would increase the total amount of stress, especially if a wave were to strike beam on before the vessel had leveled out.

[Dockhead]

Originally Posted by Captn_Black

I assume you mean this as on a big ship? Rather than a general insult?
No, I have not seen a tanker with a snubber, but then the physics are different on larger scales. 3 meter waves are not the same for such a ship. Cantery alone would work fine. That said, I have worked on salvaging a broken chain and anchor from such a ship, that was lost in a storm. Just because the gear holds doesn't mean that the ground tackle set up is not being damaged.
You seem to have made a big u-turn on your previous statement s with the intent of attacking me, strange.

No insult at all was intended, and no kind of attack. Sorry for any misunderstanding.


I was trying simply to illustrate the point that as vessels get bigger, the need for snubbing the anchor chain lessens and eventually goes away.


You are right about the physics, and that is the point -- big ships don't bounce around, they are not affected like our boats are. Therefore they have no need at all for snubbers.


I grew up on 37' then 42' cruising boats. The 37' would snatch at anchor in the slightest wind or sea -- you could not anchor in any conditions without a snubber. That boat needed a lot of energy absorption.


My present boat, 54' and about 25 tonnes, has very little need for a snubber except in really bad conditions. Totally different ball game. Simi 60's boat is 70 tonnes. That's another thing yet again.

[Dockhead]

Originally Posted by Captn_Black

I would also argue that too much stretch would increase horsing, which would increase the total amount of stress, especially if a wave were to strike beam on before the vessel had leveled out.

Absolutely right. There is certainly too much as well as too little stretch. That's why it's a good idea to experiment with different sizes and lengths before you find what's right for your boat.

[Captn_Black]

Originally Posted by Dockhead

No insult at all was intended, and no kind of attack. Sorry for any misunderstanding.


I was trying simply to illustrate the point that as vessels get bigger, the need for snubbing the anchor chain lessens and eventually goes away.


You are right about the physics, and that is the point -- big ships don't bounce around, they are not affected like our boats are. Therefore they have no need at all for snubbers.


I grew up on 37' then 42' cruising boats. The 37' would snatch at anchor in the slightest wind or sea -- you could not anchor in any conditions without a snubber. That boat needed a lot of energy absorption.


My present boat, 54' and about 25 tonnes, has very little need for a snubber except in really bad conditions. Totally different ball game. Simi 60's boat is 70 tonnes. That's another thing yet again.

Yea, your following statement made that clear, thanks. Yes, I guess we cannot overly generalise here. The "blanket statements" are meant for those that don't want to work things out for themselves. In reality the situation is more complex. But unless your ship is over 60' or more, I think that the generalisations apply. Just like recommended scope ratios are generally true in most circumstances, but not in more extreme situations like very deep water.