Stabilisers?

[burgundyben]

I was looking under a big displacement boat the other day that was up in the yard, it had a keel and main engine, plus a wing engine, and what looked like a pair of rudders where you'd find the outer keels on a triple keel sailing boat, I take it htese are stabilisers? How do they work?

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[tcm]

they wiggle a lot. martinwoolwichh apparently has some underwater camera on his and they are hammering away. He turned them off once and everyone fell around the boat. Hence utterly vital for big and (otherwise) rolly boats. The blades are turned to give steerage rudder effect up/down against the wave motion down/up AFAIK. Only works through the water tho...

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[jfm]

Yup. My brother has em on his trawler yacht. If you stand in the engine room underway you can see the hydraulic rams push/pulling the "tiller" arm that twists the stabilisers, and they do indeed flap about lots. Incidentally, going to the engine room to watch them in this way is much easier than rigging up an underwater camera Martin......!

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[Talbot]

some stabilisers can be rigged up to push the wrong way (thus aiding the roll) this is used by the engineers to prove the working of the stabs and give everyone else a heartattack!

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[ccscott49]

They work as ailerons, in the water, as opposed to on an airplane, reducing the roll factor. Englander needs them, she rolls on wet grass, "termed seakindliness"

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[martinwoolwich]

Sorry been away.

Certainly do have cameras on board but none that look at the stabilisers. However do have LCD screen that shows what they are doing. For blinkin great fins, running under hydraulic power, they don't half move quick!!"

The example TCM was talking about... Crossing Christchurch bay F4/5 wind against tide family were playing scrabble on the saloon table. Big brother says "what happens if you turn them off?" So I did. Big yelps from behind, scrabble tiles and board and players thrown all over the place. Turn them back on all peace restored with less than five seconds.

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[MapisM]

Careful with such experiments...

...besides the effects on the crew, you could damage the equipment.
At least, that is a clear warning on the owner's manual of my Naiad equipment.

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[Gludy]

Re: Careful with such experiments...

What does the warning say?

Surely you have to switch them on at some time ... so have you any idea why switching them off and on can damage them?

<hr width=100% size=1>Paul

 

[MapisM]

Here\'s why...

Just look at the following pages: 2.
Hope that helps.

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[Gludy]

Re: Here\'s why...

Thank you very much ... I understand it better now.

<hr width=100% size=1>Paul

 

[MapisM]

I\'m happy to understand...

...that it makes sense to you.
Must admit that I never completely understood what the effects of a "momentary list" would be.
Does the boat risk to take off, or what?.../forums/images/icons/crazy.gif

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[hlb]

My bike used to wiggle alot till I got stablisers on it!!

<hr width=100% size=1> No one can force me to come here. I'm a volunteer!!.

Haydn

 

[NorthernWave]

The stabilisers on modern boats vary. These days you even have Zero speed stablization for while at anchor. The type of system you looked at probably was the more basic type which works with a sensor mounted in the centre of the boat. Depending on the age of the system depends how well this sensor works, on the older systems the boat would need to do approx 1 to 1 half rolls for the sensor to correct, thus only really reducing roll bye about 60%. The newer systems of the fin type have much faster processors which actually correct the roll as it happens, reducing the roll upto 98%. The hydraulic system is simple with two rams controlled by two solinoids and a potentiometer.
The super systems these day have different types of stabilisation, fins are still used but a new system that works well is the azipod. These systems are so advanced that not only do you get stabilisation at anchor, you don't actually have to use an anchor any more. The azipod is exactly what it sounds like, it's a electric motor that hangs down under the boat with a big prop run by an electric motor. This is used on the QM2 I believe. Alot of tugs also use this system and if your yacht is fitted with a number of these they give you incredible manouverbility. The pod can spin on it's axis at 360 degrees and with links to the GPS the boat can hold itself in position and stabilised by just rotating and blasting in what ever direction stops the roll or keep the boat in position.

Chris

P.S. sorry if the spelling or grammer is poor, a bit rushed.

<hr width=100% size=1>In Ft Lauderdale

 

[hlb]

Still found the three wheeler better!!

<hr width=100% size=1> No one can force me to come here. I'm a volunteer!!.

Haydn

 

[jfm]

Re: Stabilisers? -other systems

While we're on the subject there are two other methods. Ferretti are now offering a new anti roll device on boats down to 50foot ish. Not sure but I think it's a box about the size of a genset with a spinning mass inside, spun by a lectric motor. Made by mitsubishi i think. There are no stabiliser fins. See website. Feadship use a ballast tank system where water slooshes very fast over a flume from one side of the boat to the other, in a massive internal tank, in antiphase with the roll of the boat while at anchor

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[BrendanS]

Re: Stabilisers? -other systems

Phew

Whole point of having a boat is that it feels liked a boat. Otherwise buy a condo somewhere warm <g>

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[NorthernWave]

Re: Stabilisers? -other systems

These are big floating condos.

Azimut and Ferretti are both working on very similar systems, the Azimut is like a big pendalom.

Chris

<hr width=100% size=1>In Ft Lauderdale