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Maritime Forum

TOPIC: Marine Engineer Officer (Naval Architechture)

Marine Engineer Officer (Naval Architechture) 12 Jan 2012 15:46 #229

(a) With reference to double plated hollow rudders:
(i) State the merits of this type of rudder compared to the single plate rudder.
(ii) State two methods of protecting the rudder from internal corrosion;
iii) Describe how the ship and its performance would be affected by a cracked rudder plate which allows the ingress of seawater.
(b) When the ship is in drydock:
(i) How would you inspect a rudder, and what all clearances you would check.
(ii) State the tests that should he carried out to ensure water tightness of the rudder after a repair to a cracked rudder plate.
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Re: Marine Engineer Officer (Naval Architechture) 09 Jun 2012 03:27 #4045

  • class 1 exam candidate
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i) increase in buoyancy.
reduced weight and load on the carrier bearing.
double plate with stiffeners inside gives better strength to withstand forces.
stiffeners inside the hollow rudder gives an outer smooth surface flow, reduce drag.
due to the aerofoil shape of the rudder, it has a higher stall angle.

ii) sacrificial anode attached.
volatile corrosion inhibitor sprayed into the rudder.

iii) flooded rudder increases weight on the aft end of the ship.
slower response to steering, which affects hunting on the steering gear, causes the ship to yaw, increases headway resistance, and thus increases fuel consumption.

b)
i) pintle clearance by feeler gauge - to check bronze liner wear down, port, stbd, centre position.
rudder carrier bearing wear down - check if excessive wear down of the weight carrying bearing.
anodes if fitted - to see if need replacement
corrosion, cracks or damage around the rudder and stock.
check to see if palm coupling nut and pintle nut is secured via hand holes or removal of inspection plate.
check water tightness of rudder by pressure test.

ii) holes and plugs are fitted on the rudder plate.
so can fill with water, and air pressurized to 1 bar.
or vacuum test monitoring pressure gauge.
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