Author Topic: Can we talk rudders?  (Read 4619 times)

Offline Paul Bradshaw

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Can we talk rudders?
« on: May 25, 2013, 11:25:43 PM »
How is the rudder size for a vessel determined? Dimensions? Mass? For example an 18.5 GT vessel with dimensions 10.06 x 3.17 x 1.40.

Offline Paul Bradshaw

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Re: Can we talk rudders?
« Reply #1 on: May 25, 2013, 11:34:06 PM »
Does this sound right? Calculate the lateral under water area, and take between 1~2% of this, and that is rough guide for a rudder size.

   

Offline Paul Bradshaw

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Re: Can we talk rudders?
« Reply #2 on: May 25, 2013, 11:36:28 PM »
Or is this theory more applicable? It is very similar to the Tail Volume Coefficient used in aircraft design, defined as:

    Vh = (Sh x Lh) / (Sw x MAC)

where:

    Sh = horizontal tail area
    Lh = distance from tail's aerodynamic center to the airplane's CG
    Sw = wing area
    MAC = the mean aerodynamic chord of the wing.
« Last Edit: May 25, 2013, 11:38:12 PM by Paul Bradshaw »

Offline JohnMcNeely

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Re: Can we talk rudders?
« Reply #3 on: May 27, 2013, 10:07:18 AM »
I'm with the same question as how practical this theory is ??..

Offline Paul Bradshaw

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Re: Can we talk rudders?
« Reply #4 on: May 27, 2013, 08:57:15 PM »
1-2% of the lateral underwater area sounds simpler and more relevant to what the rudder is acting on. Although I wonder if it applies to a vessel such as the new E class vessels? Not to mention a submarine!!

Offline N3lsoN

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Re: Can we talk rudders?
« Reply #5 on: May 27, 2013, 09:40:10 PM »
Paul,

as i remember several "long time ago lessions" for slower ones like bulkers, tankers and cargo ships you can use following calculation: 1/50 * length * draught

e.g. Aframax tankers have an average rudder area of 50 m2 to 60 m2. the  Nippon Princess is an Aframax tanker. L=229; D=12.8 => 1/50 * 229 * 12.8 = 58,62 m2 rudder size

Your example: L=10.06; D=1.40 => 1/50 * 10.06 * 1.4 = 0,28 m2 rudder size

regards
N3lson

Offline Paul Bradshaw

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Re: Can we talk rudders?
« Reply #6 on: May 28, 2013, 08:28:44 PM »
Thanks N3lsoN, much obliged.

 

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