Close quarters maneuvering with twin rudders?

[wingssail]

Generally a boat as you describe is also a fin keel boat. It will steer well going forward or in reverse. It will not require much speed because it will not require much turning thrust to make it turn.

The most important thing is to observe the wind and current you are dealing with. Look aloft and at the water and decide how to compensate for those effects. Do this well in advance.

In calm conditions you can proceed at a very slow speed, walking speed, just use the engine in and out of gear to keep some forward motion.

When weather or current is a factor you may need more speed, but not much.

You will never need to use prop wash or surges of power to bump the boat around. It will steer without that.

Leaving a slip when pointed bow out you may need to stop and reverse a bit. (Turn your rudders in coordination with the actual movement of the boat, watch the bow).

Again, go slow.

An exception to this is if your vessel has an extremely thin, high aspect keel (a blade with a bulb, for instance). This keel needs some speed to prevent leeway. You'll need to go faster.

[Tillsbury]

Originally Posted by requiem

1. Throttle up smartly, don't tiptoe out of the slip. (Always go back to neutral once moving.)
2. If a smaller boat, say under 12 m, reverse in. You'll have much more control and a better view of the slip. (It's also far easier to stop when you need to.)
3. For a larger boat you'll have more windage and so driving in forward may be preferred. (Here you don't need so much speed, because you have momentum.)

I disagree about the "smaller boat" thing. I wasn't too fussed which way I moored on a 41' boat, but on a 50 it's far far easier to come in to any tight space stern first, particularly if you have an aft cockpit. As well as more manoeuvrability, you can see exactly where the corners of the boat are at all times. Going forwards and trying to judge where your anchor is is much harder to do when it's so far away.

[Dr. D]

Originally Posted by requiem

1. Throttle up smartly, don't tiptoe out of the slip. (Always go back to neutral once moving.)
2. If a smaller boat, say under 12 m, reverse in. You'll have much more control and a better view of the slip. (It's also far easier to stop when you need to.)
3. For a larger boat you'll have more windage and so driving in forward may be preferred. (Here you don't need so much speed, because you have momentum.)

Not that I am seeking to pile on, but I have to disagree with requiem’s comment that backing into the slip is preferred due to easier to stop. I go bow first into my slip. At a hair over one knot it doesn’t take much aft throttle to stop the boat. In fact, I often stop the boat a couple of feet short of where I want to be before hooking dock lines, so I give it a short burst forward, drift to where I want to be, then hit a short burst astern to stop. The view thing is correct, though after a dozen times into the slip I understand the perspective relationship to the position of the anchor.

[wingssail]

Originally Posted by Dr. D

...At a hair over one knot it doesn’t take much aft throttle to stop the boat...

This works if you have a boat which can respond to steering inputs, and it's relatively calm.

But if you have a heavy cruiser with "good tracking", a barn door rudder, and a big fixed three bladed fixed prop, your better off anchoring out.

[requiem]

Originally Posted by Tillsbury

I disagree about the "smaller boat" thing. I wasn't too fussed which way I moored on a 41' boat, but on a 50 it's far far easier to come in to any tight space stern first, particularly if you have an aft cockpit.

It's not easier to fit the pointy end into the space first? For a random example, earlier this year I was out doing some basic docking and MOB practice. Our instruments said the wind was doing about 22 knots, and the wind generator on one of the nearby boats sounded like it was trying to take off. Note that this was actually inside the marina (near Sausalito); it was actually calmer once well into the bay. As you say, it's easier to align the stern, but will the bow follow it in with significant crosswind? My experience is mainly in the 30-42' range, and of course almost always the wind in the marina has been much gentler. I suppose a bow thruster might help, but I've yet to have such an aid.

Originally Posted by Dr. D

Not that I am seeking to pile on, but I have to disagree with requiem’s comment that backing into the slip is preferred due to easier to stop. I go bow first into my slip. At a hair over one knot it doesn’t take much aft throttle to stop the boat.

No worries! I haven't had issues stopping when going in bow first, but in tricky docking situations it can be easier to abort if you can "drive out" in forward and not have to worry about what prop walk, etc. might do to make the situation more interesting. (Which certainly should apply to much larger boats as well!)

[valhalla360]

Kind of tough with a charter but the best thing you can do is practice. Every configuration will handle different and even the same rudder/prop configuration on a different hull will have some differences.

Of course a lot of charters have you on moorings and send a guy out to bring it back into base, so you really don't need to be that good at it.

Go practice in open water for a bit to see what she does when you apply thrust and rudder in various ways at various speeds. Throw out a dingy anchor with a bumper attached and try to maneuver around it as a reference point.

[wingssail]

Originally Posted by requiem

It's not easier to fit the pointy end into the space first? For a random example, earlier this year I was out doing some basic docking and MOB practice. Our instruments said the wind was doing about 22 knots, and the wind generator on one of the nearby boats sounded like it was trying to take off. Note that this was actually inside the marina (near Sausalito); it was actually calmer once well into the bay. As you say, it's easier to align the stern, but will the bow follow it in with significant crosswind? My experience is mainly in the 30-42' range, and of course almost always the wind in the marina has been much gentler. I suppose a bow thruster might help, but I've yet to have such an aid.

No worries! I haven't had issues stopping when going in bow first, but in tricky docking situations it can be easier to abort if you can "drive out" in forward and not have to worry about what prop walk, etc. might do to make the situation more interesting. (Which certainly should apply to much larger boats as well!)

In the trickiest conditions I've ever seen, Cape Town, SA. In calm weather the sailors there do whatever they want but when the table cloth comes down black, they back in at quite daring speeds.

On Wed's nights when they are out racing, if the winds get strong they all come in after the race at full speed in reverse (often in the dark).

I don't have any photos of that but here you can see the conditions I'm talking about. Common in Cape Town.

[barnakiel]

There is no challenge with this - while there is little wind. Say up to 10 knts, no issues. 20knts and above, issues.



Once it gets windy, there is no such thing as slow speed maneuvering in these boats - you need some speed on the rudders to counteract wind drift.


Imagine this plus a lifting keel ... yes, such beasts exist too!


The less prop wash on the rudder, the more centered the prop (saildrives!) the faster is your 'slow' maneuvering.


Last thing: pre-visualise what the wind will be trying to do to you, then see if you can use this data to your advantage.



Cheers,
b.

[requiem]

Originally Posted by wingssail

In the trickiest conditions I've ever seen, Cape Town, SA. In calm weather the sailors there do whatever they want but when the table cloth comes down black, they back in at quite daring speeds.

On Wed's nights when they are out racing, if the winds get strong they all come in after the race at full speed in reverse (often in the dark).

I don't have any photos of that but here you can see the conditions I'm talking about. Common in Cape Town.

That's some wind speed! The topography looks similar; I assume katabatic winds where the clouds just pour down the mountains?

My fear with backing in at speed is, say you have a 14' beam and a 15' slip; if you're off just a tiny amount the impact could be a bit... jarring.

[wingssail]

Originally Posted by requiem

That's some wind speed! The topography looks similar; I assume katabatic winds where the clouds just pour down the mountains?

My fear with backing in at speed is, say you have a 14' beam and a 15' slip; if you're off just a tiny amount the impact could be a bit... jarring.

Yes to the katabatic, and yes they have to be skilled, but if you race in SA you get to be skilled or you find a different hobby. It's sort of a natural selection.

Hey, there are other places. Try Wellington. Sailors there keep their drogues rigged and on deck (but they don't use them in marinas, usually).

[Dr. D]

Full confession: My boat has sturdy rub rails, so I don't mind touching a piling. I know a sailor here whose boat has no rub rails and he will not let the hull touch anything. I could never do that....

[jmh2002]

Modern race boats suffer from the same problem (and often have a small 2 blade prop on a sail drive too). Even with a conventional single keel and rudder the foils are narrow so there is not a lot of 'grip' without some speed on.

And on these boats we often manoeuvred around in reverse if possible, and especially for docking, similar to what @wingssail described.

[GordMay]

Using rudder direction change, and thrust, to rotate the boat.

I start with the helm hard over to starboard (right hand prop’), with a thrust in forward. This shoves the stern to port.
The helm is then quickly switched to port and a shot in reverse is given. The stern torque, plus some rudder action jumps the stern to port, continuing the turn.
The process is repeated, forward and reverse, until the correct angle of turn is achieved.
Note: turning the helm back and forth only works with boats which have fast acting rudder ratios, and in relatively calm winds (so drift to leeward is not a problem).
The boat completes a 180 degree turn (clockwise, to starboard) in less than 2 boat lengths.

Cautions:
1. Keep power on in each direction only as long as lateral displacement is taking place. When the turning action becomes forward or aft motion, change the direction of propeller thrust (usually this is about two to three seconds tops).
2. Allow a second or two for the rpms on the diesel to drop back to idle before shifting. This is especially critical with Max props, which otherwise slam their blades back and forth putting a lot of stress on the transmission and engine pressure plate.
3. The above not withstanding, the faster the shifting takes place, the tighter will be the turning circle.
4. Do not try to fight the wind. If your bow is downwind, and there is more than four to six knots of breeze, it may be very difficult to get the boat to rotate against the wind. If you are heading upwind, set the bow off at an angle to the breeze so that it helps blow it to leeward while the prop is pulling to windward.
5. The higher the rpm (and the more horsepower going into the water) the more rotational energy there will be. However, it is best to finesse this maneuver with minimum necessary bursts of engine rather than using brute force (which is hard on the drive train).

[jmh2002]

What you describe above is the standard technique for most boats.

But these twin rudder boats can often be shallow draft (retractable keel too?), and or a performance design (with a very flat hull), and the problem can sometimes be that in anything more than about 10kn the boat just wants to go sideways because of the reduced grip in the water.

So the a above technique may indeed rotate the boat, but the boat may indeed also have slid considerably to leeward while you were trying to do this.

No flow over the foils means no grip, and this generally means going sideways - quickly...

[danstanford]

Originally Posted by jmh2002

What you describe above is the standard technique for most boats.

But these twin rudder boats can often be shallow draft (retractable keel too?), and or a performance design (with a very flat hull), and the problem can sometimes be that in anything more than about 10kn the boat just wants to go sideways because of the reduced grip in the water.

So the a above technique may indeed rotate the boat, but the boat may indeed also have slid considerably to leeward while you were trying to do this.

No flow over the foils means no grip, and this generally means going sideways - quickly...

From what I have seen, most of the dual rudder designs also have saildrives which lessens prop walk and puts the prop further from the rudders. So now you cannot get the conventional flow of water from the prop over the rudder and you don't have prop walk to aid in the standing turn described above. It seems to me, though I haven't any experience with dual rudders, that the standing turn I use and described here may not be possible.
Interested in feedback though. Dan