Cruise Talk: Fin Stabilizers

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»	Cruise Talk » Technically Speaking » Fin Stabilizers

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Topic: Fin Stabilizers

petede
First Class Passenger
Member # 3459

posted 04-10-2003 11:11 PM

I remember reading a comparison about different types of stabilizers used in ships. In the article it stated that fin stabilizers were only effective when the ship was traveling at over 19 knots, since they are like airplane wings and need "flow" to make them work. This was not much of a problem when oceanliners routinely traveled at over 26 knots, but since modern cruise ships travel much slower I wonder if the same limitations still apply, or did they find a way around it? Does anyone know?

Posts: 146 | From: New York, USA | Registered: Nov 2002 | IP: Logged

petede
First Class Passenger
Member # 3459

posted 05-10-2003 04:57 PM

Wow, I have everyone stumped?

Posts: 146 | From: New York, USA | Registered: Nov 2002 | IP: Logged

PamM
First Class Passenger
Member # 2127

posted 05-10-2003 05:24 PM

There must be a minimum speed whereby they become ineffective, but no idea of the details. A quick search reveals in the specs for Mercury that
" installed stabilizers are capable of reducing the ship's rolling motion by 90 per cent at a speed of 18 knots."
Pam

Posts: 12176 | From: Cambridge, UK | Registered: Jun 2001 | IP: Logged

petede
First Class Passenger
Member # 3459

posted 05-11-2003 12:34 PM

Thank you Pam. The 18 to 19 knot range seems to be the minimum speed need for effective roll prevention with fin stabilizes. I wonder if they were to move the Azipods to the end of the stabilizes would they function like airplane wings and help at lower speeds. Just what-if thinking.

Posts: 146 | From: New York, USA | Registered: Nov 2002 | IP: Logged

PamM
First Class Passenger
Member # 2127

posted 05-11-2003 01:52 PM

That conjures up an amusing picture

Read this page for lots of techie stuff re tilts and speed etc.
Pam

Posts: 12176 | From: Cambridge, UK | Registered: Jun 2001 | IP: Logged

peterscooter
Just Boarded
Member # 3801

posted 05-21-2003 07:31 AM

With my experience as a navigational officer when operating stabilizers, it depends on the design, manufactures, ship hull and more importantly weather conditions !

The effectiveness of the fins does relate alot to the speed through the water, and indeed the sea conditions in relation to the ships heading.

Whilst serving onboard Sun Cruises 'Sunbird' (ex Sonf of America), the effective speed at which the fins would become effective with a beam sea was about 13 knots with both fins out. With only one fin out was about 15 knots. The system onboard was made by Sperry.

When serving onboard the Sundream (ex Song of Norway) it was slightly different due to different manufacturer. A lot of our cruises in the med were very short overnight trips, therefore resulting in slow speeds. This caused a few problems with the fins working over time and resulted in the starboard side packing in for a month !!! (quite a few green faces that trip when we encountered a storm later !)

A friend who is the first officer onboard P&O's Oceana informs me that the fins onboard are effective at speeds of as low as 10 knots !

Posts: 7 | From: Southampton, United Kingdom | Registered: Apr 2003 | IP: Logged

cncservo
First Class Passenger
Member # 532

posted 06-28-2003 04:59 PM

What are the conditions or rules that determine when the Fins are deployed.

Posts: 170 | Registered: May 99 | IP: Logged

Brian_O
First Class Passenger
Member # 3910

posted 06-28-2003 06:20 PM

quote:
Originally posted by cncservo:
What are the conditions or rules that determine when the Fins are deployed.

Captain's judgement.

Posts: 2698 | From: Pointe-Claire, QC Canada | Registered: Jun 2003 | IP: Logged

gohaze
First Class Passenger
Member # 586

posted 06-29-2003 10:37 AM

AMOI...the MEDIA was the first Atlantic liner to be fitted with Denny-Brown fin type stabilizers in 1953.
The AQUITANIA, Blt 1914, had Frahm rolling tanks.
And here's an interesting one. The CONTE Di SAVOIA,Blt. 1931, had 3 100ton gyros, made by Sperry fitted in a tank that were supposed to counteract the roll. Not much said about them so probably not successful.
Lastly there is the oldest of all, the steadying sail, still used by the likes of small fishing vessels today.

...peter

Posts: 1909 | From: Vancouver.BC | Registered: Sep 99 | IP: Logged

cruise man
First Class Passenger
Member # 3976

posted 07-03-2003 07:28 PM

this is a area that i know oh so much about. you are right that a ship has to be traveling at a certain speed for the stablizers to be affective but with today's technology that speed is reduced by 6 or 7 knots or somewhere in the 14 or 15 knot range for the stablizers to be affective. also now some ships are built with horizontal stablizers which can work at pretty much all speeds.

Posts: 27 | From: florida | Registered: Jul 2003 | IP: Logged

petede
First Class Passenger
Member # 3459

posted 07-03-2003 09:37 PM

quote:
also now some ships are built with horizontal stablizers which can work at pretty much all speeds.[/QB]

Can you please explain about horizontal stabilizers? I am very intrigued about this!

Posts: 146 | From: New York, USA | Registered: Nov 2002 | IP: Logged

cruise man
First Class Passenger
Member # 3976

posted 07-03-2003 09:54 PM

petede,
horizontal stablizers and vertical stablizers do the same job but are very different.
vertical stablizers have to be deployed, have to flow with the water to work and the ship has to be moving in a certain range of speed.
now to your question, horizontal stablizers are usually placed at the stern and mainly the ships with azipods have horizontal stablizers although some ships without azipods do have horizontal stablizers too. now, the way horizontal stablizers work is that they are always deployed and they work at basically any speed. if you dont understand this compare horizontal stablizers to the keel of a sailboat, they basically function the same way. i hope this answers your question.

Posts: 27 | From: florida | Registered: Jul 2003 | IP: Logged

gohaze
First Class Passenger
Member # 586

posted 07-03-2003 10:54 PM

I'm afraid you've got me again. Horizontal means flat to the surface the same as an aircraft wing. The leading edge of the fin moves up and down to counteract the roll and to have the maximum effect they are usually placed close to midships.

Horizontal stabilizers aft? Do you mean vertical skegs?

....peter

Posts: 1909 | From: Vancouver.BC | Registered: Sep 99 | IP: Logged

cruise man
First Class Passenger
Member # 3976

posted 07-03-2003 11:01 PM

oh god i'm sorry
i mixed up horizontal and vertical, take everything i said about the stablizers and switch horizontal and vertical.
sorry for the mix up
cruise man

Posts: 27 | From: florida | Registered: Jul 2003 | IP: Logged

Vaccaro
First Class Passenger
Member # 465

posted 07-04-2003 01:54 AM

Cruise Man,

First, welcome aboard this message board.

The vertical stabs you're speaking about are there for counteract the yaw before all and not the roll (or quite marginally in fact), to simplify, the same way a vertical fin of a plane does (yaw and/or azimutal drift, both for Z axis passive/active stability and heading's control of course).
Where I follow you is that these vertical fins are usually efficient at lower speed compared to anti-roll fins.

Posts: 1193 | From: France ...where the greatest liners ever are born, ...by far! | Registered: Feb 99 | IP: Logged

cruise man
First Class Passenger
Member # 3976

posted 07-04-2003 07:53 AM

quote from vaccaro,

Where I follow you is that these vertical fins are usually efficient at lower speed compared to anti-roll fins.

yes, this is exactly the point i'm trying to get across about vertical stablizers
thanks

Posts: 27 | From: florida | Registered: Jul 2003 | IP: Logged

petede
First Class Passenger
Member # 3459

posted 07-04-2003 04:40 PM

Here is a picture of the QM2 pods. Am I correct in assuming that the long object in the middle that looks like a rudder is a vertical stabilizers? And am I also correct in assuming that if the Vertical stabilizers aide in yaw, then the horizontal (fin) stabilizers are still need for roll.

Posts: 146 | From: New York, USA | Registered: Nov 2002 | IP: Logged

cruise man
First Class Passenger
Member # 3976

posted 07-04-2003 05:24 PM

petede,

yes you are right the object in the middle is or does look like a vertical stablizer, but i dont understand your secind question. i cant elaborate very much now because i'm at work but explain your second question a little better and i will read and answer it tonight.

thanks,- cruise man

Posts: 27 | From: florida | Registered: Jul 2003 | IP: Logged

Captain Rhone
First Class Passenger
Member # 3498

posted 07-04-2003 05:27 PM

If you look here and go to to pic taken on May 28 you will find that the cut out objects by the keel are actually the stabilizers and the center object at the stern is not.

Posts: 686 | From: New York,USA | Registered: Nov 2002 | IP: Logged

cruise man
First Class Passenger
Member # 3976

posted 07-04-2003 05:33 PM

captain rhone,

this is cruise man and i saw all of the pics on that site but i cant see ehat you are talking about
if you can, can you tell which pic it is

thanks,- cruise man

Posts: 27 | From: florida | Registered: Jul 2003 | IP: Logged

cruise man
First Class Passenger
Member # 3976

posted 07-04-2003 05:36 PM

captain rhone,

this is cruise man again, ehat on my last message is suppost to be what

Posts: 27 | From: florida | Registered: Jul 2003 | IP: Logged

Captain Rhone
First Class Passenger
Member # 3498

posted 07-04-2003 07:01 PM

Anyway...if you are confused about where the stabilizer are then look at the middle of the ship at the area that would be underwater,then near by you see curved things sticking off the sides in three spots and if you go up farther you should see tiny rectangular slots of which the stabilizer's are in.

Posts: 686 | From: New York,USA | Registered: Nov 2002 | IP: Logged

cruise man
First Class Passenger
Member # 3976

posted 07-04-2003 10:51 PM

thanks for the pic captain rhone, i see what you are talking about now-
......cruise man

Posts: 27 | From: florida | Registered: Jul 2003 | IP: Logged

petede
First Class Passenger
Member # 3459

posted 07-04-2003 10:56 PM

Yes Rhone, I know where the fin stabilizers are located. I was asking about vertical stabilizers that cruise man was talking about in a post that is above. I wanted clarification because I became confused about his post and understood it to mean that fin stabilizers are being replace with vertical stabilizers (which is not the case.) I was also asking if the object in the center is a vertical (yaw control) stabilizer.

Posts: 146 | From: New York, USA | Registered: Nov 2002 | IP: Logged

Captain Rhone
First Class Passenger
Member # 3498

posted 07-04-2003 11:00 PM

What is a Yaw Control Stabilizer?I never heard of that before.

Posts: 686 | From: New York,USA | Registered: Nov 2002 | IP: Logged

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