56 APPLICATION OF BUOYANCY BOXES TO THE STEAMSHIP 



all decks and bulkheads which are nominally watertight should be really and in fact water- 

 tight. 



If it be desired to adopt some method such as that proposed in this paper for render- 

 ing ships more difficult to sink, I personally am of the opinion that there are far more effec- 

 tive methods than that advocated by Mr. Donnelly. I say this because I have seen a ship 

 which was fitted with protection against torpedo attack safely docked after being struck 

 by three torpedoes : and it would not be a difficult matter, in my opinion, to construct mer- 

 chant ships so that on the outbreak of war they could be provided with some such system 

 of protection which is markedly superior to that described in this paper. In conclusion, how- 

 ever, I desire to repeat and emphasize that it would be far better that all our ingenuity 

 and energy should be directed towards the provision of an effective means of sinking the 

 submarine rather than an effective means of keeping a ship afloat after it has been struck 

 by a torpedo. 



The President: — We are certainly very much obliged to Commander Goodall for 

 the discussion of this paper. May I ask if it would be proper for him to describe the 

 methods of protection to which he referred? 



Commander S. V. Goodall : — I am afraid, sir, I could not do that. 



Captain W. Hovgaard, Member (Communicated) : — As Mr. Donnelly refers to my 

 methods of determining the trim of a ship in the damaged condition, and as his explana- 

 tion of that method on some points is not quite complete, I wish to make a few additional 

 remarks to it. 



I use the so-called "lost-buoyancy" method according to which the water that enters 

 the ship is regarded as part of the sea, and not as a weight added to^ the displacement. By 

 this method the displacement remains unaltered, and the center of gravity remains in the 

 same position as before bilging. 



The formula which I use for calculating the trim (total) when the flooded compart- 

 ments are in free communication with the sea, is : — 



pwrL 

 t = 



W.GM' 



where p is the factor of permeability, and pw is the weight of water which has entered the 

 ship up to the original water-line. This weight, of course, is a known quantity, r is the 

 distance of the center of gravity of that water from a vertical through the center of gravity 

 of the reduced water-line (obtained by deducting the flooded area from the original water- 

 line area). L is the length of the ship. W is the displacement to the original water-line. 

 GM' is the longitudinal metacentric height found by first determining the metacentric 

 radius BM' , and subtracting from BG, the distance between the center of buoyancy and 

 the center of gravity. The change in the vertical position of the center of buoyancy is 

 neglected. 



r. 



BM' =^— - 

 V 



where /'2 is the longitudinal moment of inertia of the reduced water plane about a trans- 

 verse axis through its center of gravity and V is volume of the original displacement. 



