Skip to main content

Propeller slip

  • When the vessel is moving ahead the propeller exerts pressure on the water to create the forward motion. 
  • Propeller slip occurs because water is not a solid medium and there is some slip related to it.
  • Slip may be considered as the difference between the speed of the vessel and the speed of the engine. 
  • It is always expressed as a percentage.
Propeller Slip = Actual forward speed/ Theoretical forward speed.
  • The calculated value of slip will be increased when the wind and sea are ahead and if the vessel has a fouled bottom. 
  • The differing values of slip are especially noticeable after a vessel has been cleaned in drydock.
  • Theoretically a vessel should never have negative slip, but this may occur in one or more of the following conditions:--  A strong following sea.
                                                                         A following current or a strong following wind

How to find the Propeller Slip
Mean Apparent slip = Distance run by propeller - distance run by ship per day
                                                             Distance run by propeller

Distance run by propeller in nautical miles = Pitch(m) x total engine revolution per day
                                                                                       1852

Comments

  1. Hey what a brilliant post I have come across and believe me I have been searching out for this similar kind of post for past a week and hardly came across this. Thank you very much and will look for more postings from you Best Used Outboard Motors for sale Craigslist service provider.

    ReplyDelete
  2. You have shared a lot of information in this article. I would like to express my gratitude to everyone who contributed to this useful article. Keep posting. marine suppliers

    ReplyDelete

Post a Comment

If you have any doubts.Please let me know

Popular posts from this blog

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.