Skip to main content

What is bulbuous bow ? Discuss its advantages and disadvantages.

  • A bulbous bow is a feature of many modern ship hulls
  • It is characterized by a protruding bulb at the bow (or front) of the ship below the waterline. Due to this, a bulbous bow is usually only visible when a ship is in drydock.
  • The presence of this bulb modifies how water flows around the hull, thereby reducing drag and affording an increase in speed, range, and fuel efficiency.
  • In ships that have had bulbous bows fitted, gains in fuel efficiency of between 12-15% are standard. As these factors are particularly important for almost all applications of maritime vessels, bulbous bows have seen widespread adoption since their development.
  • Despite their advantages, bulbous bows only achieve maximum effect at a narrow range of speeds, and at speeds exclusively over 6 knots .
  • At other speeds outside the range for which they were designed, bulbous bows can have the opposite effect and actually increase the drag. 
  • Finally, bulbous bows have the greatest effect when applied to large ships such as freighters, cruise ships, and navy vessels. 
  • Bulbous bows are rare on recreational boats as these vessels have wide speed ranges and are often designed to plane over the water at high speed.

Comments

Popular posts from this blog

Differences between MC/MC-C and ME/ME-C engines

The electrohydraulic control mechanisms of the ME engine replace the following components of the conventional MC engine: Chain drive for camshaft Camshaft with fuel cams, exhaust cams and indicator cams Fuel pump actuating gear, including roller guides and reversing mechanism Conventional fuel pressure booster and VIT system Exhaust valve actuating gear and roller guides Engine driven starting air distributor Electronic governor with actuator Regulating shaft Engine side control console Mechanical cylinder lubricators. The Engine Control System of the ME engine comprises: Control units Hydraulic power supply unit Hydraulic cylinder units, including: Electronically controlled fuel injection, and Electronically controlled exhaust valve activation Electronically controlled starting air valves Electronically controlled auxiliary blowers Integrated electronic governor functions Tacho system Electronically controlled Alpha lubricators

Why is a man hole door elliptical in shape?

Any opening in a pressure vessel is kept to a minimum and for a man entry an elliptical hole  is lesser in size than the corresponding circular hole. More over it is prime concern to have a  smoothed generous radius at the corners to eliminate stress concentration. Hence other  geometrical shapes like rectangle and square are ruled out.  To compensate for the loss of material in the shell due to opening, a doubler ring has to be  provided around the opening. The thickness of the ring depends on the axis length along the  dirrection in which the stresses are maximum and the thickness of the shell. It is important to  align the minor axis along the length of the vessel, as the stress in this direction is  maximum. Longitudinal stress: Pd/2t where P= pressure inside the vessel, d= diameter of the arc, t=  thickness of the shell plating  Circumferential stress: Pd/4t  More over a considerable material and weight saving is achieved as minor is along the  direction of maximum stress.

Shell Expansion Plan

It is a two dimensional drawing of a three dimensional surface of the ship’s hull form. This plan is very useful for the following information:It is used for marking the location of a hull Damage on this plan by identifying the strake number , letter and frame number so that the exact location of the damage and also suggested repairs are marked in a localised copy. The shell expansion can be used for finding areas of painting surfaces such as topside, boot topping and bottom areas by applying Simpsons rules directly.  In the shell expansion the vertical scale used is different from the horizontal scale and a suitable adjustment has to be made when calculating areas. This becomes useful in solving disputes concerning areas of preparation and painting. It gives information on the thickness of the original strake which is indicated by the number in the circle shown in the strake.  The quality of steel used is also shown by letters A,B,D E and AH, BH,DH, EH.