Anchoring Protocol revised

[skipmac]

Originally Posted by foggysail

Thanks Skip-

This year is over for harbor hunting and on top of that, we didn’t even make it to Tashmo this season. I can think...next year for sure and for sure, there are limited number of years left that things and trips can be put off. Tashmo is a beautiful harbor so enjoy!

Maybe lucky you didn't make it here. Immediately after the dredging problem there was as 3 1/2' MLW bump in the entrance channel. By August tide and traffic had leveled that off a little and by following the correct zig zag through the entrance you could get 5' at MLW. Real fiasco. Supposed to be corrected and the channel (re)dredged to 10' "soon".

If I'm not off somewhere cruising I'll be here next summer. Drop me a line if you're in the area.

[Mike OReilly]

Jim, my process is roughly to begin digging in the anchor around 4:1 scope. It depends, of course, but once I feel the anchor bite (which I refer to as the set), I’ll then start to dig her in with reverse thrust on the engine.

I don’t use snubbers during this process at all. The chain is hooked to a well backed point on deck. Reverse is slowly increased till the chain I can see is fully lifted, and it is “bone hard” to the touch. I believe you can tell a lot by feeling the rode. If it’s not fully taut it will transmit that feeling through the rode as it lifts or moves under load. You can also observe the chain/water interface. If it ‘bumps’ around (for lack of a better term), it is not fully taut.

So a sustained reverse pull with a fully taut chain will look and feel quite different than one that is not — at least in shallow waters. In deeper anchorages (over, say 30’) this technique doesn’t works very well. Here the catenary becomes a much stronger effect, and I agree, you’d be hard-pressed to sustain a fully taut chain.

For some reason we actually like anchoring close to shore. So most of the time we’re under 15’. This past summer we anchored for a long time (almost 8 weeks), at times swinging within 20’ of shore, in less than 7’ of water at low tide. My boat draws 6’. That’s a whole foot more than I need , even when weathering a few Newfoundland gales that was pushing us towards the lee shore. (OK, on those night I admit I didn’t get a lot of sleep ).

[danielamartindm]

Originally Posted by Mike OReilly

Jim, my process is roughly to begin digging in the anchor around 4:1 scope. It depends, of course, but once I feel the anchor bite (which I refer to as the set), I’ll then start to dig her in with reverse thrust on the engine.

I don’t use snubbers during this process at all. The chain is hooked to a well backed point on deck. Reverse is slowly increased till the chain I can see is fully lifted, and it is “bone hard” to the touch. I believe you can tell a lot by feeling the rode. If it’s not fully taut it will transmit that feeling through the rode as it lifts or moves under load. You can also observe the chain/water interface. If it ‘bumps’ around (for lack of a better term), it is not fully taut.

So a sustained reverse pull with a fully taut chain will look and feel quite different than one that is not — at least in shallow waters. In deeper anchorages (over, say 30’) this technique doesn’t works very well. Here the catenary becomes a much stronger effect, and I agree, you’d be hard-pressed to sustain a fully taut chain.

For some reason we actually like anchoring close to shore. So most of the time we’re under 15’. This past summer we anchored for a long time (almost 8 weeks), at times swinging within 20’ of shore, in less than 7’ of water at low tide. My boat draws 6’. That’s a whole foot more than I need , even when weathering a few Newfoundland gales that was pushing us towards the lee shore. (OK, on those night I admit I didn’t get a lot of sleep ).

I hope the next world is one where the set of the wind never changes once you drop anchor . What you say about "feeling" the set of the anchor by touching the rode and seeing its emergence angle from the water is great advice.

[thinwater]

Originally Posted by Don C L

In 6' of water I'd be saying "yikes!" and if it is high tide, double "yikes!"

LW, obviously.


Not to say I've never dried out on purpose. But that is a whole nuther' thread. ZERO wave action is a requirement.

[foggysail]

Originally Posted by skipmac

Maybe lucky you didn't make it here. Immediately after the dredging problem there was as 3 1/2' MLW bump in the entrance channel. By August tide and traffic had leveled that off a little and by following the correct zig zag through the entrance you could get 5' at MLW. Real fiasco. Supposed to be corrected and the channel (re)dredged to 10' "soon".

If I'm not off somewhere cruising I'll be here next summer. Drop me a line if you're in the area.

That is interesting! And I will make a note to let you know if I am in the harbor. It is an easy trip for me to make from our dock in Fairhaven. Summers just seem to be getting shorter and shorter. I need to do a better job of time management and get my boat out more often.....next year for sure.....maybe

[thinwater]

Originally Posted by Jim Cate

...What I was commenting on is the assertion(s) of folks that their chain was "bar taught" whilst only observing the upper end of it, and in fairly low wind speeds.

Jim

I've always thought an important number to have in your head is "what windspeed is my reverse thrust equivalent to?" With my outboard powered cat, only about 25-30 knots. With most inboard powered monohulls, more like 30-40 knots, depending on the prop. As you imply, few boats have the power to really stretch the rode.


The most wind I ever dove on an anchor was a sustain 35-40 knots with a lot of fetch. The power is impressive and I don't recommend it, though in a twisted way, it was fun. I've worked with a load cell on deck over 60 knots and caution is required. I had one explode on me due to a freak wave (large boat wake in shallow water). But for the most part, if you measure the load at 15 knots, to a very good approximation it goes up with windspeed ^2.

[noelex 77]

This is an example of the chain underwater while the anchor was set under full reverse.

It was at 3:1 in 5m of water. The vessel was slightly smaller than average, but otherwise a typical cruising yacht. They had a Brunton Autoprop which does develop a little more reverse power than a typical fixed prop, but not quite as much as some of the feathering props. The chain was 8mm, which a little on the thin side for this sized boat. I know the skipper, but cannot remember the engine size but it was nothing out of the ordinary for the vessel size.

Mathematically, catenary cannot disappear completely but there was very little visible in this case (but you can judge the catenary for yourself).

In the early stage of the setting process before full reverse is applied there is more effect from the catenary and obviously in deeper water and with greater scopes the catenary will increase, but hopefully the photo gives some idea of what is occurring at the anchor at the depths and scope mentioned.

[Dockhead]

Originally Posted by Mike OReilly

.. . .

My only comment regarding the OP’s situation is that if there is one boat out of the group that is moving significantly differently so as to risk damaging others, then it is common courtesy and common sense, that THEY should do something, regardless of who was first. Of course, not everyone accepts their responsibilities. And in the end, it is everyone’s responsibility to avoid collision.

I agree with this, and I think it's an extremely important point.


Thin is also right.


But one thing which is never good at sea -- that's "standing on your rights", in this or that situation, whether it's some erroneously conceived "right of way" in a risk of collision situation, or your "rights" as first in the anchorage. Good seamanship requires awareness of risks and flexibility -- it sometimes requires adapting to the way others have anchored, and it not rarely demands moving if we don't like the way someone else has anchored, or if someone doesn't like how we anchored.



As Mike said -- everyone should always be ready to do something, which is necessary or desirable to make a situation safer or work better -- that's good seamanship.