Calling all swingers!

[Ancient_Mariner]

I found myself the subject of quizzical looks from other yachties recently while at anchor in Newtown River on the IoW. While the other boats clearly had their fair share of anchor swing, we were really "larging" it as far as swinging goes!

I have often wondered what the cause of anchor swing is, and I'm sure that there must be those of you out there who can cast some light on this. Questions that have really got me puzzled are : Do tide and wind directions and strengths interact to make it more pronounced at times? Does it help offsetting the rudder to point the boat into the wind? (It seems not). Anything that can be done to reduce the amount of swinging?

Really appreciate any thoughts.

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[dralex]

There will be loads of answers on this- windage is a big factor for variation in swinging and also amount of hull beneath the water to provide lateral resistance against the swinging. Compare a catamaran at anchor to a monohull- the cat will usually be running circles because of high windage and low resistance in the water.

Wind against tide causes interesting effects, especially in strong winds when the wind will overcome the tide, but also in gusty winds will produce rapidly changing forces on the boat, and therefore movement.

Is your boat significantly different to the ones that were settled.

IMO the lashed rudder just pushes you to one side of the tidal stream, which can sometimes be helpful, but will push you to the opposite side when the tide turns. One thing I tried in strong winds was letting out a small amount of genoa as a stabilising sail- it did work and kept the boat more into the wind.
Sometimes I've found lengthening or shortneing the scope can calm things down a bit as the swinging seems to have a resonant frequency. Another thing to try is hanging a bucket on a warp over the transom in the tidal flow- this will keep the boat more consistently in line with the tide and more settled.

Regards

Alex

<hr width=100% size=1>Just enjoy it.

 

[graham]

Agree with all the other advise ,also boats using chain and warp will wander about more than those with all chain.

If you have to use chain and warp try attatching a heavy weight to the warp so the boat has to drag this across the bottom whilst swinging about.

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[Twister_Ken]

If you can be bothered, use a Bahamaian moor which will kill swinging, although you'll still rotate.

In somewhere like Newtown creek, though, you won't half confuse the others!

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[Vara]

Explanation please,"Bahamaian moor"

<hr width=100% size=1>If it cant be fixed with a lump hammer don't fit it

 

[boatmike]

Depends on the boats characteristics largely. Talk to any catamaran owner who is used to being "wind rode" rather than "tide rode" and he will tell you that we are always pointing in the opposite direction to everyone else and very often describe an arc of destruction in a mooring where other long keeled heavyweights sit all neatly in a line.... All you can do is shorten up on the chain as much as possible without risk and smile sweetly at the neighbours as you career past......
My own boat, (bless her) always wants to sail over the chain and very often I end up sailing up tide to the chagrin of those lying tide rode in a river.... The most annoying habit people have is when I have deliberately sought out a deserted anchorage where I am no bother to anyone some pillock in a conventional monohull parks right on my tail and then complains when the tide turns and we end up in his lap.... PLEASE, PLEASE, when you see a large cat at anchor and you are a monohull GIVE ME ROOM..... ITS NOT MY FAULT!!!!!!

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[Twister_Ken]

Wotsa a Bahamian Moor?

1. Drop hook 1
2. Fall back down tide to twice normal scope
3. Drop hook 2 out of the back
4. Pull forward on hook 1 to normal scope, while paying out on hook 2.
5. Stop.
6. Bring warp for hook 2 to bow.
7. Make both warps fast

Variation on theme: join warp 2 to warp 1 with a shackle and drop 'join' to below keel depth. This will stop the boat tripping over one warp or t'other as she spins.

With this arrangement, the area of 'swing' can only be the area where the normal swinging circle of the two anchors overlaps.




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[Vara]

Re: Wotsa a Bahamian Moor?

Thanks,familiar with technique,now I know what its called/forums/images/icons/smile.gif
But must admit have only done it once as exercise,takes ages!

<hr width=100% size=1>If it cant be fixed with a lump hammer don't fit it

 

[steve_cronin]

Ken\'s pulling your leg!

Doing that in Newtown is like lighting your cigar from the candle at LAOB meeting!

I got a severe telling off from an old lady in a dark green Contessa one weekend for "not allowing my boat to swing with the rest" and "setting the conditions for midnight mayhem" for lying to two bridled anchors.

Problem with Newtown is that nobody will admit to when the place is full IMO

Steve Cronin



<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[webcraft]

On our recent charter I had the dubious pleasure of sailing a modern AWB for the first time - a Beneteau 403, fin keel & spade rudder.

She was the worst of all the charter boats we came across for swinging on a mooring or at anchor - but particularly on a mooring. Big cats on the other hand remained steady as a rock. No tide, so everyone was wind-rode.

It was not what I was expecting and not what is described here.

On another tack, I have a friend who uses a riding sail on the backstay and swears by it.

- Nick



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[TheBoatman]

On our club swinging moorings we insist on all tillers being lashed to stb (boat wants to turn to port) so that in theory all boats want to swing the same way. However if you have a Macgregor next to a Twister which is next to a benny 40 you'll end up with knitting/banging and thats from boats on mooring buoys.

The bottom line is every boat will swing differently and you have to make allowances for the different types and allow enough room. Talk to your neighbours before dropping anchor. Be a good seaman/neighbour?

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[Ancient_Mariner]

To all you swingers out there

Thanks for the ideas. Of the ideas put forward, the ones that appeal most are using a temporary sail on the backstay (the physics seem to suggest that that might be more effective than using a bit of the genoa) and a bucket trailed off the transom (which might be the most effective of all if the tide is strong enough).

Does anyone know just how the physics of the swing works? Seems to me that a small change in the boat orientation creates a high pressure on one side of the hull and low on the opposite side (whether this is because of wind or tide) which sets off the swing in the direction that the hull originally moved. So all that offsetting the rudder does is get the first swing going - after that it has no effect other than to damp one of the directions a bit. The more the tide the worse the offset will make the swing! The bucket idea is best because the distance between bucket and transom doesn't matter as the lever effect increases as the boat begins moving and always acts in the direction of the tide.

If wind and tide are in different directions - my brain hurts! Anyone without a hangover with ideas?

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[Twister_Ken]

Wind and tide in opp directions

The question is not insoluble but includes several variables, mainly

Underwater surface area, especially lateral surfaces
Windage
Strength of tide
Strength of wind
Gustiness

As a general rule the more of the boat there is underwater, the more likely it is to lie tide rode and vice versa. This won't hold good in high winds and small tides though.

Once had an older Swan on a mooring in Cowes Roads, with a strong westerly blowing over 2kts of west going tide and the boat wouldn't settle, I think because the wind/tide effects were close to balancing each other out, so a bit more or less wind, and off she went. When the tender came back ( a mini RIB with a meaty outboard) and was tied from the stern, things settled down a bit more.

If we'd been anchored rather than on a mooring, then there would have been a good chance of tripping the anchor.

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[Ancient_Mariner]

Re: Wind and tide in opp directions

I wonder whether the deep-keeled older boats swing more or less that the modern GRP's that tend to have shallower draughts and rounder hulls. I would hazzard a guess that the older boats swing more than the modern ones. I'm presuming that the tide effects are dominant so there would be a greater pressure difference (hence more swing) around the deeper keels than the flatter ones.

I would agree that wind over tide would tend to dampen things, but the wind would have to be pretty strong (>F5) over a reasonable tide.

Interesting comment about the effect of the rib - tends to bear out the thought that a bucket/rib off the back would be the best option while the tide is running.

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[steve_cronin]

Surprised that nobody\'s mentioned....

..than if you tie off the helm, then a boat with a largish rudder will behave significantly better than if the rudder is left to it's own devices.

High freeboard yachts are particularly vulnerable as the bow gets blown sideways and then tries to sail the anchor out until it points too high, following which it tacks and the momentum carries the other bow around until it too tries to sail off, stalls and it starts all over again. With a long keeler this ability to swing is greatly resisted by the keel and the boat just sinks back stretching it's rode to the fullest extent.

With a ketch, a hoisted mizzen sheeted tight also improves things no end.

Steve Cronin

<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[Twister_Ken]

Re: Wind and tide in opp directions

My boat is generally solid as a rock (long keel with keel hung rudder, 5' draft, 3' freeboard ) on the hook. It's the yoggie pots that charge about like spring lambs.

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[mirabriani]

Re: Wind and tide in opp directions

Well I hope it does not have an affinity with it's mates Ken
(Solid as a rock)
My spring lamb tends to sprint past long keelers.

Regards Briani

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[Twister_Ken]

Re: Wind and tide in opp directions

Spring lambs, no stamina.

Pass the mint sauce, Doris.

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[ChrisE]

Re: Wind and tide in opp directions

Ken,
I'd love to agree with you about yoghourt pots but I'm afraid to say that, ahem, our Rival38 is a bit frisky in a blow. High bow keeps us skying around a fair bit even with her 10 tons to shift. I'm sure, however, that her dance is done with more panache than a yp.
Chris

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[chuns]

If you\'ve been around this forum for a while....

... you could be forgiven for thinking Monty the Mounty was back!!! Or was that another forum?

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