Boats that behave at anchor?

[macd]

The Rival shears about until it's blowing a hoolie and then takes up dead straight, until the wind drops or gust passes and the she starts wandering about. It has never really bothered me it is what boats do.

My take on this is that most boats only sheer if there's slack in the rode. If winds are constant (no gusts), the catenary maintains the same curve, pulling the bow to wind with little sheering. (We had this just the other night with winds varying by only a couple of knots: no significant sheering). In gusty conditions, the catenary alternately increases and decreases, pulling the boat forward in the lulls. The resulting slack in the catenary allows the boat to fall away and sheer on the next gust.

Most boats will try to go broadside to the wind when falling away. Boats with pronounced sheer, like your Rival and my old R32, will do so in a more exaggerated fashion.

In strong winds without pronounced lulls the catenary remains straight enough in the (relative) lulls to permit only a little slack when the next gusts comes, just as you describe.

In other words, the catenary acts as both a helpful shock absorber at the end of a sheer, and as a cause of the very sheer it's protecting. (A long snubber is a better shock-absorber, anyway, but carries the same penalty of pulling the boat forward when the wind-load decreases and encouraging sheer).

The Meltemi, here in Greece, is notorious for its gustiness in supposedly 'sheltered' anchorages. The wind will frequently gust to 30-odd knots, then die to a zephyr. The only practical ways to reduce sheering then are a riding sail, or V-anchors (and the latter is often not practicable in a crowded anchorage).

I'm not presenting this as gospel but it seems to fit with my experience. I'd be interested in what others think. Of course, even if true, it doesn't help very much: no-one's likely to fit a rod rode. But maybe a kedge to hold the rode tighter might help? Anyone tried it?

 

[RupertW]

My take on this is that most boats only sheer if there's slack in the rode. If winds are constant (no gusts), the catenary maintains the same curve, pulling the bow to wind with little sheering. (We had this just the other night with winds varying by only a couple of knots: no significant sheering). In gusty conditions, the catenary alternately increases and decreases, pulling the boat forward in the lulls. The resulting slack in the catenary allows the boat to fall away and sheer on the next gust.

Most boats will try to go broadside to the wind when falling away. Boats with pronounced sheer, like your Rival and my old R32, will do so in a more exaggerated fashion.

In strong winds without pronounced lulls the catenary remains straight enough in the (relative) lulls to permit only a little slack when the next gusts comes, just as you describe.

In other words, the catenary acts as both a helpful shock absorber at the end of a sheer, and as a cause of the very sheer it's protecting. (A long snubber is a better shock-absorber, anyway, but carries the same penalty of pulling the boat forward when the wind-load decreases and encouraging sheer).

The Meltemi, here in Greece, is notorious for its gustiness in supposedly 'sheltered' anchorages. The wind will frequently gust to 30-odd knots, then die to a zephyr. The only practical ways to reduce sheering then are a riding sail, or V-anchors (and the latter is often not practicable in a crowded anchorage).

I'm not presenting this as gospel but it seems to fit with my experience. I'd be interested in what others think. Of course, even if true, it doesn't help very much: no-one's likely to fit a rod rode. But maybe a kedge to hold the rode tighter might help? Anyone tried it?

I find that sheer happens even when the rode is very taut and as we know even heavy chain removes almost all catenary in even medium winds, say 20 knots. The slack that you see in the rode when sheering is (I think) caused by the boat sailing up towards the anchor slightly as it moves sideways, the slams very taut at the end of each swing. I use a rubber snubber and nylon to minimise that shock but the better solution is stopping the sheer. Boras in Croatia and meltemis in Greece have been very testing and a bit nerve wracking although in the end we have never dragged at all (so far) after being sure the anchor is set.

 

[Tranona]

I've always thought that was a duff idea. When the wind goes round, instead of the boat quietly swinging round with it, and staying head to wind, you get the wind and any waves on the beam. No thanks.

Remember that poster is in the med and his method is quite common because of the lack of tides, usually no wind at night and steep drops close to shore. So very different conditions from where you sail so different techniques needed.

 

[jbweston]

In the size you mention, I would be looking at something like a Malo, among current boats. The other thing that would help would be to remove the foresail, but doing without a furling jib is not an attractive option for most of us.

Penguin is a Malo 37 and she sheers about at anchor. One of the few things (perhaps the only thing) about her that irritate me. I've measured up for a riding sail but haven't yet got round to having it made.

 

[JumbleDuck]

I'm not going back to a 27 footer so am looking for advice on something around 35- 45 foot that behaves.

The owner of a set of moorings where I spent a couple of days earlier in the summer said "The old Nicholsons and Westerlies stay rock steady when it blows, but the modern Bavarias and the like sheer around all over the place." Sure enough it blew the second night we were there and the Bavaria on the mooring in front of us was veering around wildly. We, like the other heavy stuff, stayed put.

 

[geem]

We have a 44ft ketch and we don't sheer. I assume this is due to the windage of the mizzen mast acting like a tail fin on a plane. The windage aft keeps us pointing into the wind. We are also a heavy boat with 7ft 2in draft so there is a plenty of keel in the water. She sits very comfortably at anchor.

 

[wully1]

We have a 44ft ketch and we don't sheer. I assume this is due to the windage of the mizzen mast acting like a tail fin on a plane. The windage aft keeps us pointing into the wind. We are also a heavy boat with 7ft 2in draft so there is a plenty of keel in the water. She sits very comfortably at anchor.

ive always liked the look of a ketch and noticed they generally sit still at anchor but will probably end up with a riding sail contraption on some flavour of ( older ) AWB as mentioned above.

Most likely another Moody as in my limited experience they are far, far better built than a continental equivalent.

 

[geem]

ive always liked the look of a ketch and noticed they generally sit still at anchor but will probably end up with a riding sail contraption on some flavour of ( older ) AWB as mentioned above.

Most likely another Moody as in my limited experience they are far, far better built than a continental equivalent.

I am inclined to agree with you. You are unlikely to go far wrong with a Moody. Our ketch is a Trintella. 37 years old and still turns heads. A very capable yacht from an era when quality was standard not optional

 

[Zing]

It happens because the centre of effort is forward of the keel and the boat wants to spin away from the wind. It can't because of the anchor chain, so drifts sideways until the pull of the anchor is the greater force, then it reverses. Ketches anchor-sail less because they have more windage aft of the centre of effort. Some people put the mizzen sail out a bit to improve this. On a sloop/cutter, the most effective solution is an anchor riding sail.