ship construction- EKG -skeg rudders

EKG -ship construction 2016

12) With reference to twin skeg rudders

a)   Explain why a single rudder may not suitable for some vessels   (05 marks)

Twin propeller ship have a choice of installing two rudders directly behind the propeller or to install a single rudder at  the center of the ship.

Twin rudders are always more responsive than a single rudder

Single rudder will give very small response at slow speed therefore it is inevitable to have twin rudder in most ships

Some twin screw ship operate well with one screw in operation with the twin rudders operate in tandom

Currently in some twin propulsion ships rudder are used in and emergeny to act as retardant by turning the rudder at angle greater than ususal 35 dgrees this can be effectivelu used only in twin rudder ships

The  purpose of having twin propellers are to have increase power and to provide  greater safety factor to the propulsion system twin tudder alwas give a greater safty factor against a single rudder

    

b)   State the advantages of twin skreg installation in modern vessels with a large cargo carrying capacity  (05 marks)

The twin skeg concept is well proven with obvious advantages for the design of ships with full hull forms, restricted draft or highly loaded propellers fuller hul forms can be achived only when the vessels are large

In  designing for the optimum results following factors are important:

        I.            Distance between skegs

      II.            Longitudinal slope between skegs

    III.            Vertical skeg inclination

   IV.            Longitudinal skeg inclination

     V.            Skeg form

Above characteristics are difficult to achieve in small vessel with out disturbing the flow of water to the propeller therefore the benefit of twin skeg can be harnessed at appreciably lager vessels results has shown as much as 13% improvement in propeller efficiency have achieved in large vessels