Advantage of tiller to one sidel when on mooring?

[Birdseye]

When the tide is flowing they will all veer the same way

Surprisingly, not true. Once had a mooring at Weir Quay and it was fascinating to see that the boats did when moored in any sort of breeze and of course river flow. You could put them into 3 groups - the oldy low freeboard long keeled who were very much tide driven, the modern fin keel Benny types who moved quite a bit and sometimes were driven forward over their buoy, and then the drop keelers that went almost anywhere in the breeze. Surprisingly my then Prout cat was quite well behaved

 

[James_Calvert]

What about wheel steering?

If I lash my wheel to port the boat swings the opposite way.

I just leave it in the middle.

I've always found wheel steering on yachts odd too...

 

[Daydream believer]

Surprisingly, not true. Once had a mooring at Weir Quay and it was fascinating to see that the boats did when moored in any sort of breeze and of course river flow. You could put them into 3 groups - the oldy low freeboard long keeled who were very much tide driven, the modern fin keel Benny types who moved quite a bit and sometimes were driven forward over their buoy, and then the drop keelers that went almost anywhere in the breeze. Surprisingly my then Prout cat was quite well behaved

Which is why any sensible person in charge of moorings tends to put boats of a similar nature in groups. I think that it is pretty obvious that a boat with a shallow draft & lifting keel is going to behave differently to a long keeled boat. One reason why we asked such lifting keelers to leave their keels down. Our club commodore did so with his Anderson 22 for the 30+ years he had a mooring & never had a problem. Then along came a bearded wonder with a Jeneau 2000 who insisted on raising keel & rudder. He did not stay on the moorings long, after his boat suffered £5k of damage when it hit 2 more boats one week. He was not the only one to suffer damage

 

[Daydream believer]

The real benefit is when the tide turns from slack to wind over tide. Boats with tiller to port will tend to turn together. If the tiller is central they can break shear and cause mahem.

Dan I believe that you had a Stella. Was it based at Burnham & was it in proximity with other Stellas, like mine? My one was in close proximity to the other Stellas when there was a bigger fleet. If it had NOT turned in unison with other boats it would have hit them. Bob Cole put them in quite tight.
Did you experience this? Seems to me that some on this forum seem intent on denying actual events as evidence that it does work. In which case the theory behind it is irrelevant really.

 

[LittleSister]

Surprisingly, not true. Once had a mooring at Weir Quay and it was fascinating to see that the boats did when moored in any sort of breeze and of course river flow. You could put them into 3 groups - the oldy low freeboard long keeled who were very much tide driven, the modern fin keel Benny types who moved quite a bit and sometimes were driven forward over their buoy, and then the drop keelers that went almost anywhere in the breeze. Surprisingly my then Prout cat was quite well behaved

I used to have a mooring at Weir Quay (and very nice it was, too). My boat at the time (long fin Hurley 22) was 'well behaved' . (Not so sure about the skipper though. )

In my recollection the boats at Weir Quay back then were well spaced (or maybe I was put on a mooring suitable for a larger boat than my own?). I've been on other moorings - no names, no pack drill - where the spacing was insufficient and boats could, and did, collide with one another on occasion.

 

[DanTribe]

Dan I believe that you had a Stella. Was it based at Burnham & was it in proximity with other Stellas, like mine? My one was in close proximity to the other Stellas when there was a bigger fleet. If it had NOT turned in unison with other boats it would have hit them. Bob Cole put them in quite tight.
Did you experience this? Seems to me that some on this forum seem intent on denying actual events as evidence that it does work. In which case the theory behind it is irrelevant really.

I bought Starfox from Tucker Brown but kept her a Fambridge for a few years on a trot with other Stella's. Then back to Priors. If Uncle Bob said tiller to port it was the right thing to do, no question.
Boats with different keel configurations and weights will act differently so similar types should be grouped together where possible.

 

[Chiara’s slave]

I’m sure it’s just for uniformity. If you’ve gone to the trouble of grouping similar boats, then they’ll all need to be similarly configured too. It may not always be perfect, just a case of covering as many bases as possible.

 

[Zagato]

Terrible memory but I think the advice given to me was to lash the tiller to port to keep the mooring buoy and chain away from the bobstay/whisker lines, hull but especially the anchor on one side or the bowsprit.

 

[LittleSister]

Seems to me that some on this forum seem intent on denying actual events as evidence that it does work. In which case the theory behind it is irrelevant really.

I have seen strong evidence that lashing the tiller to port stops boats being trampled by elephants , but none that proves lashing rudders to port (or starboard) keeps adjacent boats better aligned than lashing rudders centralised.

(I have no problem agreeing that neighbouring moored boats will be better aligned if they all have their rudders similarly aligned.)

No one has yet provided an explanation of how it would have such an effect superior to locking rudders centralised. I'm happy to be proved mistaken if anyone can provide one.

(I have no problem agreeing that neighbouring moored boats will be better aligned if they all have their rudders similarly aligned.)

I don't really care a great deal about the issue, as it happens (I'll conform to whatever is required wherever I may moor), but I think it's an interesting issue to puzzle over.

I'd assumed there was a reasoned explanation, and that's what I was looking for in starting this thread, but the longer it continues without one, the stronger my suspicion that it's an old wives' tale.

Zagato's suggestion of a benefit in relation to bobstays and bowsprits is, to my mind the most plausible so far.

Because it puts the boat into a stalled "hove too" position as the rudder sails the boat against its keel. It then sits in a "forced" position.
With the rudder centrally that does not happen & the boat can wander from side to side

What is it, this 'sitting in a 'forced' stalled position'? An aquafoil - the keel or the rudder - work most efficiently - i.e. produce greatest lift - when they are aligned at a small angle to the flow over them (the tide, or other current, for our mooring purposes). If the aquafoil is at a greater angle from the current it will produce less lift (and increase drag), and once the angle of attack is increased sufficiently it will stall and produce very little or no lift.

If there is a substantial angle between the rudder and the keel they cannot both be working at their most efficient. One, the other, or both, will be producing less lift than they are capable of.

Having keel and rudder both aligned along the boat's centreline will produce the greatest forces aligning the boat with the flow.

If boats best held a given angle against the flow over them by having the rudder at a significant angle to the keel we'd be recommended to use this as a sailing/motoring technique, and tiller pilot and wind vane manufacturers' shares would plummet. I've never heard of anyone doing it, let alone recommending it.

The example of hove to position is irrelevant, as far as I can see. The object of hoving to is to as near as possible stop making way through the water (not at all what a mooring does). Once you've done that you have to find some way to compensate for the loss of directional stability normally provided by the flow of water over the foils, in order to achieve an approximately constant angle to the wind.

To achieve this one sets both the foresail and aft sail to (a) produce as little lift as possible, and (b) work against one another when either starts to generate drag by facing the wind as a result of the boat turning one way or another, as it will, and also to set the keel (forward aquafoil) and rudder (aft aqua foil) to (a) produce as little lift (and as much drag) as possible, and (b) to work against one another when either start to get a flow over it. None of this will hold them in a forced position. It is merely the null to which it tends to revert between the two unstable positions either side of it.

A boat on a mooring with a tide or current running is effectively being dragged through the water by the mooring. In the absence of wind, with rudder angled to one side the boat will sit to one side of alignment to the current, and with the rudder centralised it will sit in alignment with the current. As the foils in the latter case are both better aligned to the water flow than with a rudder at a significant angle to the keel, they will inevitably generate more lift (when the current direction wanders or wind or some other force pushes the boat out of alignment with it), and hold the boat in better alignment with the current, than the 'tiller over' boat will be held to its angle to that flow.

Or to get back to the earlier claim, it's forced in its 'forced' position more, er, forcefully when rudders are centralised than when they are held to one side.

 

[KevinV]

If the aquafoil is at a greater angle from the current it will produce less lift (and increase drag), and once the angle of attack is increased sufficiently it will stall and produce very little or no lift.

Maybe you've hit the nail on the head right there? Increase drag at the stern, so the rudder works like a staysail?

Like you I'm just interested and would love to see a technical explanation - it's a curious thing. So many apparently obsolete old practices do serve a purpose, we've just been doing them so long we've forgotten how or why it's done.

 

[Buck Turgidson]

I have seen strong evidence that lashing the tiller to port stops boats being trampled by elephants , but none that proves lashing rudders to port (or starboard) keeps adjacent boats better aligned than lashing rudders centralised.

(I have no problem agreeing that neighbouring moored boats will be better aligned if they all have their rudders similarly aligned.)

No one has yet provided an explanation of how it would have such an effect superior to locking rudders centralised. I'm happy to be proved mistaken if anyone can provide one.

(I have no problem agreeing that neighbouring moored boats will be better aligned if they all have their rudders similarly aligned.)

I don't really care a great deal about the issue, as it happens (I'll conform to whatever is required wherever I may moor), but I think it's an interesting issue to puzzle over.

I'd assumed there was a reasoned explanation, and that's what I was looking for in starting this thread, but the longer it continues without one, the stronger my suspicion that it's an old wives' tale.

Zagato's suggestion of a benefit in relation to bobstays and bowsprits is, to my mind the most plausible so far.



What is it, this 'sitting in a 'forced' stalled position'? An aquafoil - the keel or the rudder - work most efficiently - i.e. produce greatest lift - when they are aligned at a small angle to the flow over them (the tide, or other current, for our mooring purposes). If the aquafoil is at a greater angle from the current it will produce less lift (and increase drag), and once the angle of attack is increased sufficiently it will stall and produce very little or no lift.

If there is a substantial angle between the rudder and the keel they cannot both be working at their most efficient. One, the other, or both, will be producing less lift than they are capable of.

Having keel and rudder both aligned along the boat's centreline will produce the greatest forces aligning the boat with the flow.

If boats best held a given angle against the flow over them by having the rudder at a significant angle to the keel we'd be recommended to use this as a sailing/motoring technique, and tiller pilot and wind vane manufacturers' shares would plummet. I've never heard of anyone doing it, let alone recommending it.

The example of hove to position is irrelevant, as far as I can see. The object of hoving to is to as near as possible stop making way through the water (not at all what a mooring does). Once you've done that you have to find some way to compensate for the loss of directional stability normally provided by the flow of water over the foils, in order to achieve an approximately constant angle to the wind.

To achieve this one sets both the foresail and aft sail to (a) produce as little lift as possible, and (b) work against one another when either starts to generate drag by facing the wind as a result of the boat turning one way or another, as it will, and also to set the keel (forward aquafoil) and rudder (aft aqua foil) to (a) produce as little lift (and as much drag) as possible, and (b) to work against one another when either start to get a flow over it. None of this will hold them in a forced position. It is merely the null to which it tends to revert between the two unstable positions either side of it.

A boat on a mooring with a tide or current running is effectively being dragged through the water by the mooring. In the absence of wind, with rudder angled to one side the boat will sit to one side of alignment to the current, and with the rudder centralised it will sit in alignment with the current. As the foils in the latter case are both better aligned to the water flow than with a rudder at a significant angle to the keel, they will inevitably generate more lift (when the current direction wanders or wind or some other force pushes the boat out of alignment with it), and hold the boat in better alignment with the current, than the 'tiller over' boat will be held to its angle to that flow.

Or to get back to the earlier claim, it's forced in its 'forced' position more, er, forcefully when rudders are centralised than when they are held to one side.

Google servo tab for aircraft flight controls. With the tiller over in a flow the boat is hinged around the mooring, the rudder hinge moment from that will swing the yacht until the hinge moment from the fin to the mooring is equal and opposite. The boat is then in equilibrium. If a gust of wind pushes the boat in either direction it will tend to return to its equilibrium. If the fin and rudder are aligned then any gust will cause them both to pull the same way. The boat will then make phugoid oscillations until eventually returning to in line with the flow.

edit to add: the above doesn't take into account windage. If the boat is lying to wind it will always oscillate.

 

[LittleSister]

Google servo tab for aircraft flight controls. With the tiller over in a flow the boat is hinged around the mooring, the rudder hinge moment from that will swing the yacht until the hinge moment from the fin to the mooring is equal and opposite. The boat is then in equilibrium. If a gust of wind pushes the boat in either direction it will tend to return to its equilibrium. If the fin and rudder are aligned then any gust will cause them both to pull the same way. The boat will then make phugoid oscillations until eventually returning to in line with the flow.

edit to add: the above doesn't take into account windage. If the boat is lying to wind it will always oscillate.

But you don't fly aircraft with the wings at a disadvantageous angle of attack to hold a level course!

You are correct, in your boat example, that when the gust of wind deflects the boat from its 'resting' - in equilibrium - position (at, say, 20 degrees to the current) it will tend to return to that position once the gust has passed. It will have returned to that position as a result of either the lift of the keel overcoming the contrary lift of the rudder, or vice versa. So the actual force involved in returning it to alignment with the current is the lift on one foil, minus the lift on the other. The total lift is less than the lift of either foil's potential.

By contrast, when a boat with its rudder locked centrally is deflected from alignment with the current - likewise its equilibrium position - both foils will generate lift in the same direction, back towards alignment (until alignment is reached). The lift of the two foils is additive, and inevitably greater than in the 'hinged', rudder locked to one side, previous example.

(The foils will also both generate more lift as they are closer to their optimal angle of attack, rather than in the near stalled example of a rudder locked at, say, 45 degrees, to one side.)

 

[Buck Turgidson]

But you don't fly aircraft with the wings at a disadvantageous angle of attack to hold a level course!

You are correct, in your boat example, that when the gust of wind deflects the boat from its 'resting' - in equilibrium - position (at, say, 20 degrees to the current) it will tend to return to that position once the gust has passed. It will have returned to that position as a result of either the lift of the keel overcoming the contrary lift of the rudder, or vice versa. So the actual force involved in returning it to alignment with the current is the lift on one foil, minus the lift on the other. The total lift is less than the lift of either foil's potential.

By contrast, when a boat with its rudder locked centrally is deflected from alignment with the current - likewise its equilibrium position - both foils will generate lift in the same direction, back towards alignment (until alignment is reached). The lift of the two foils is additive, and inevitably greater than in the 'hinged', rudder locked to one side, previous example.

(The foils will also both generate more lift as they are closer to their optimal angle of attack, rather than in the near stalled example of a rudder locked at, say, 45 degrees, to one side.)

No but for stable flight the vectors are in opposite directions. Also note that stalled does not mean no lift and as the boat swings the angle of attack on the rudder is reducing thus coefficient of lift increasing. This is stability 101. It is as previously mentioned why heaving to works. The boat is sitting in equilibrium.

 

[Daydream believer]

Having keel and rudder both aligned along the boat's centreline will produce the greatest forces aligning the boat with the flow.

I have not read all your post, because I just know that the mooring system works, However, as i scanned the thread I did see your comment & immediately thought to myself:-
There is your first mistake. It does not produce any force because it is not producing any side lift.
Correct that & see if it makes any difference to your theorising, I cannot be bothered.

 

[Stemar]

If you really want to align your boat with the flow, hang a bucket over the stern. It'll work far better than the rudder

 

[DanTribe]

If you really want to align your boat with the flow, hang a bucket over the stern. It'll work far better than the rudder

That's all very well in theory, but what sort of bucket and type of line and knot?

 

[LittleSister]

I have not read all your post, because I just know that the mooring system works,

I have never said it (i.e. rudders fixed to one side) does not work. I have suggested merely that rudders fixed centrally will, as far as I can see, achieve the same thing but better.

I have asked for an explanation of the mechanism by which offset rudders might provide an advantage, but have seen only assertions that it does so.

However, as i scanned the thread I did see your comment & immediately thought to myself:-
There is your first mistake. It does not produce any force because it is not producing any side lift.
Correct that & see if it makes any difference to your theorising, I cannot be bothered.

I am uncertain what it is you are saying is my first mistake, and what does not produce any side lift.

Side lift will be generated by a boat (by virtue of its shape, coracles excepted!) whether rudder fixed hard over, fixed centralised or with no rudder at all, as soon as it is out of alignment with the current (whether because the direction of the current has changed or the boat has been subject to wind or other force pushing it to one side). That lift is what brings boats back into alignment with the current (and hence, as far as practicable, its neighbours). Once it is back in alignment, there will be no side force, just drag, until the next time that stable position is disturbed.

I have simply argued that the side force bringing it back into alignment would be greater with rudder fixed centrally than rudder hard over (or no rudder at all).

There's no reason you should be bothered. I'm not asking you to be. What your club does works well enough for you.

 

[LittleSister]

If you really want to align your boat with the flow, hang a bucket over the stern. It'll work far better than the rudder

Sadly not, as anyone who has tried to use buckets to steer a boat that's lost its rudder will tell you.

It's one of the reasons why racing boats don't use buckets to steer.

 

[kacecar]

I moor my boat in a place where the lessor asks mooring holders to leave their boats with the steering set hard to starboard. Based on observation, and a bit of further consideration prompted by this thread, perhaps it's about what happens to boats moored in breezy wind-against-tide conditions - a frequent occurrence on a fairly exposed tidal river. Perhaps a boat that is reliably skewed across the current, even if only slightly, will tend to present a more consistent profile to the wind so is less likely to be blown this way and that.

In such conditions my own boat (deepish fin, separate aft rudder) does seem prone to veer about more with the steering locked straight than when the rudder is locked hard over, and if the rudder is left unlocked then the veering can get more pronounced. The most extreme veering I've seen was of a Halberg Rassy 31, on a neighbouring mooring, in breezy wind-against-tide conditions. It was "sailing" about so much I became concerned and alerted the owner . He came back out to his boat and discovered he had accidentally left the steering unlocked. As soon as he locked the rudder hard over, as he normally did, the veering about stopped.

 

[Daydream believer]

If you really want to align your boat with the flow, hang a bucket over the stern. It'll work far better than the rudder

Actually the owner of the Jeneau 2000 I mentioned earlier tried that with a plastic dustbin. As far as I recall It was not successful . Paricularly as the tide turned