Effect of rudder position on stability whilst moored.

[Cardinal]

What is the forum’s experience of the effect on the stability of a 12.24 m yacht of the position in which the rudder has been locked whilst moored in a gale or storm.
Some yachts seem to “sail” about quite wildly and others seem stable. Does rudder angle have a marked effect?

 

[Concerto]

Are you in Ardfern marina or on a mooring buoy?

If on a mooring buoy, then it is usual for about 20 degrees of helm (check other boats to see if port or starboard) as when the tide changes, boats will swing the same way to avoid collisions. On the Medway when I had a singing mooring, the helm was lashed to starboard. I know Ardfern is not as tidal, but it will still help if all boats swing the same way with wind or tide.

 

[Seashoreman]

I have always lashed the tiller on my swinging mooring. It does seem to steady the boat which is smaller than yours. It obviously depends on a number of factors and will no doubt be a conversational debate. I will kick this off by saying it depends where you are moored. Most of our moorings are on a bend in a deepish wideish exposed river on the east coast, it can be fast flowing at times but with sheltered eddies. Some boats have a lot of 'windage' and deeper keels. All I can say is I never leave the boat without putting a couple of turns on the rudder. (please don't pick holes in my response, mid Sunday Roast cooking and just my ideas).

 

[dunedin]

What is the forum’s experience of the effect on the stability of a 12.24 m yacht of the position in which the rudder has been locked whilst moored in a gale or storm.
Some yachts seem to “sail” about quite wildly and others seem stable. Does rudder angle have a marked effect?

I would very much doubt that there is enough water flow speed past a boat at Ardfern for rudder position to make any material difference (though certainly worth keeping wheel locked as you already do).
Suspect that some aspects of windage and underwater shape make more of a difference to how moves in a wind - top hamper like multiple jibs on furlers, large sprayhood etc.

 

[NormanS]

I always leave my helm lashed admidships.

 

[Cardinal]

Thanks for the interest. I am on a swinging mooring during the season but go to the pontoon in Winter. I’ve never had any suspicion that there was any severe swinging till the recent storm when one cheek of my bow fitting was badly bent and the mooring chain came out.
I usually lock the rudder amidships but the last time out a friend was on the helm and I suspect it was locked on full lock.
Maybe that caused swinging in the storm.

 

[dunedin]

Thanks for the interest. I am on a swinging mooring during the season but go to the pontoon in Winter. I’ve never had any suspicion that there was any severe swinging till the recent storm when one cheek of my bow fitting was badly bent and the mooring chain came out.
I usually lock the rudder amidships but the last time out a friend was on the helm and I suspect it was locked on full lock.
Maybe that caused swinging in the storm.

I strongly suspect that ALL the boats were sheering about wildly in Storm Amy. It was a very serious weather event.

 

[ducked]

Are you in Ardfern marina or on a mooring buoy?

If on a mooring buoy, then it is usual for about 20 degrees of helm (check other boats to see if port or starboard) as when the tide changes, boats will swing the same way to avoid collisions. On the Medway when I had a singing mooring, the helm was lashed to starboard. I know Ardfern is not as tidal, but it will still help if all boats swing the same way with wind or tide.

Cant see how that would work on a tide change. Rudder effect requires relative movement between the hull and the water. At the turn of the tide there isnt any,

There is only relative movement when the boat is held in place by the mooring in the tidal stream, when an offset rudder will cause the mooring line to angle-off straight downstream. As the tide slackens, the angle will reduce until the mooring goes slack, then drift about at slack water until carried forward (with no relative movement and so no rudder effect) until brought up against the mooring again.

I THINK, but of course practical beats "thought experiment" every time.

 

[Chiara’s slave]

The thought experiment simply says look at the other boats/ask… you’d think there’s a greater chance of the line of boats swinging the same way at the same time if they all do the same thing with their rudders. Except the silly trimarans of course. Hopefully there’s enough space between swinging moorings to avoid a clash, but, it has happened to me personally, and it caused major grief. And no, not with the tri, with a XOD, 20ft long keel boat.

 

[ducked]

The thought experiment simply says look at the other boats/ask… you’d think there’s a greater chance of the line of boats swinging the same way at the same time if they all do the same thing with their rudders. Except the silly trimarans of course. Hopefully there’s enough space between swinging moorings to avoid a clash, but, it has happened to me personally, and it caused major grief. And no, not with the tri, with a XOD, 20ft long keel boat.

If you look at what the other boats are doing thats a practical test

If you ask yourself if "there’s a greater chance of the line of boats swinging the same way at the same time if they all do the same thing with their rudders." that was the thought experiment I did, and I concluded what they did with their rudders wouldnt make any difference, for the reasons stated.

Could be wrong, of course. If, for example, there is never truly slack water, then the rudders could have an effect. I dunno if this could happen but tides are peculiar things and there are riverine and wind driven currents,

Plus I hadn't considered that there's also perhaps the weight of the mooring pulling forward against the slackening tide perhaps introducing a very little relative movement so maybe...

 

[ylop]

I strongly suspect that ALL the boats were sheering about wildly in Storm Amy. It was a very serious weather event.

I didn’t see footage from that particular location but I did see footage from the general area. Every boat got a proper pounding. In normal weather though I can see we veer around more that older lower wind age, long keeled boats - I have wondered if the answer is to rig long lines with rubber “snubbers” in them to remove some of the snatching, leaving the normal pennant as a “back up”. Usually that thought comes to me about 3am just as the rain arrives!

 

[zoidberg]

I recall an 'olde worlde' trick for taming the wild sheering about - or 'sailing' - some boats, and dogs, tend to do while tethered on a rode.

The trick involved lowering a used tyre on a stout rope, a foot or two immersed, off the stern. This didn't prevent sheering; it reduced the violent 'charge' that is the cause of damage.

 

[ducked]

Builders bag, or part of a series drogue, might be alternatives. I;d thoght of rigging off the bows but I suppose off the stern might be better, and would reduce entanglement with the main rode risk.

OTOH it wont resist the boat being driven backwards and could forse it sideways. and perhaps damage the rudder, so perhaps up-front is best

One of the dual anchor techniques involves setting a second anchor on a short scope which is espected to drag around and resist sheering from side to side. Special name for it that I cant remember. Hammerlock? Hammerhead? Something like that

Hammerlock apparently. Number 3 on the linked site below.

Advanced Anchoring Techniques

 

[zoidberg]

I'd thought of rigging off the bows but I suppose off the stern might be better, and would reduce entanglement with the main rode risk.

One of the dual anchor techniques involves setting a second anchor on a short scope which is espected to drag around and resist sheering from side to side. Special name for it that I cant remember.

Like 'ducked' I'd considered rigging off the bow, for it's the bow that has the strong tendency to 'blow off' when gust-struck. I s'pose one could rig such a tyre on a pair of lines P&S via a pair of cleats NEAR the bow.... like a bridle, but immersed.

While setting a second anchor in a V-pattern is a time-honoured sailing master's technique in some circumstances - it was much used by cargo vessels in the Schelde estuary, for example - and the knowhow is 'good to have', here's another time-honoured technique from the days of working sail....

Drudging.*

On making entry to a narrow port with a following breeze, trawl a kedge anchor or another heavy weight on short scope, just bumping over the bottom without 'setting', to keep the boat speed down and keep the course straight. Haul in off the bottom to pick up some way and steerage again.

* Just noticed this mentioned in the USBoat article referenced above, where some 'Murricain has invented a new name for an age-old practice. Me, I prefer 'Seamanship In The Age Of Sail' by Harland which is full of techniques used by the ancients and Tom Cunliffe, to solve common boaty/shippy problems. Having some of these old ideas up my sleeve has got me out of a few scrapes. Sadly, they don't seem to help keep me from getting into them.

 

[Chiara’s slave]

I can’t imagine trailing the kedge off the back of our boat in any conceivable circumstances. 2 crew, everything happens very quickly heading into modern yacht moorings, hence my banging about how vital it is to be able to stop yourself on your engine no matter what. I can see the technique could help slow you, and possibly keep the stern in line. Coping with depth variations, and the speed variations you need to make when in a line of boats heading into or out, not so much.

 

[zoidberg]

I can’t imagine trailing the kedge off the back of our boat in any conceivable circumstances. 2 crew, everything happens very quickly heading into modern yacht moorings, hence my banging about how vital it is to be able to stop yourself on your engine no matter what. I can see the technique could help slow you, and possibly keep the stern in line. Coping with depth variations, and the speed variations you need to make when in a line of boats heading into or out, not so much.

Being old ( more so some mornings ) I'm kind of 'old school'. Over the decades I've learned to do a lot of 'What If-ing' and, believe you me, nothing but nothing happens as quickly as in the cockpit of a twin-jet f'bomber when the engines stop and it suddenly goes quiet! And I count all-carbon racing trimarans in that lengthy collection of 'WTF's.

Far be it for me.... but I rather prefer making the approach speed into/onto moorings 'manageable' - what airy-pilots would call a Stabilised Approach rather than a fighter's high-speed Run-Break-Land - and I use others' accumulated painful experience and resultant wisdom to help me avoid learning their lessons all over again the hard way.

One way to avoid dangling a hefty kedge - which in Chiara's locker is likely to be an old tin of beans or a 1kg dinghy grapnel - is to use a sturdy steel bucket on a rope.... or two, if you have 'em.

Or really large oversized superyacht inflatable fenders, of which I have a few.

 

[ducked]

Like 'ducked' I'd considered rigging off the bow, for it's the bow that has the strong tendency to 'blow off' when gust-struck. I s'pose one could rig such a tyre on a pair of lines P&S via a pair of cleats NEAR the bow.... like a bridle, but immersed.

While setting a second anchor in a V-pattern is a time-honoured sailing master's technique in some circumstances - it was much used by cargo vessels in the Schelde estuary, for example - and the knowhow is 'good to have', here's another time-honoured technique from the days of working sail....

Drudging.*

On making entry to a narrow port with a following breeze, trawl a kedge anchor or another heavy weight on short scope, just bumping over the bottom without 'setting', to keep the boat speed down and keep the course straight. Haul in off the bottom to pick up some way and steerage again.

* Just noticed this mentioned in the USBoat article referenced above, where some 'Murricain has invented a new name for an age-old practice. Me, I prefer 'Seamanship In The Age Of Sail' by Harland which is full of techniques used by the ancients and Tom Cunliffe, to solve common boaty/shippy problems. Having some of these old ideas up my sleeve has got me out of a few scrapes. Sadly, they don't seem to help keep me from getting into them.

The USBoat article mentions drudging as well as the hammerlock anchoring technique, though I've seen the name used elsewhere.

I think I've read of Thames barges using a drudging technique to obtain steerage when they would otherwise be drifting out of control in the tidal current, look no engines stylee. I THINK they had a special disk-shaped "anchor" for this, something like, or perhaps an actual, railway wheel, or perhaps a filled mushroom, because a standard fluked anchor might grab and stick unpredictably rather than skidding, giving less control, but I might have invented that.

They might use this technique when there was no wind, or when shooting bridges that they had to drop the rig for. I THINK I have also read of them dropping the rig and, once through a bridge "sailing" the rig back up with the pressure of the wind, windsurfer stylee, though that seems barely credible, given how big and heavy it is

 

[zoidberg]

'Hammerlock'....

Vague recollection of the term being used in wrestling, and of a specific design of chain connector used in pro lifting.
Never before heard it used in the USBoat sense. Probably just another simple Yank malaproprianism.

 

[NormanS]

When my boat is on its mooring, it's left to its own devices with the helm lashed amidships. If it wants to yaw about, so be it. We're seldom aboard on the mooring.
At anchor, when it's windy, and the boat wants to yaw about, I rig my riding sail. This dramatically reduces any tendency to yaw. It's easy for me, with a ketch rig, but with some imagination and ingenuity, perfectly possible with a sloop.
It seems to me, to be better to reduce the tendency to yaw, rather than to try to deal with the consequences.