228 SELECTION OF THE BEST KIND OF PROPELLING MACHINERY. 
sonnel, so that, assuming the same price, whether the owner will run the ship as a motor 
ship or as a steamship, the conversion is not justifiable except for the long voyages; but if 
these ships can be bought for conversion purposes at $30 a ton less than would be paid to 
continue as steamships, the fixed charges are reduced on a 10,000-ton ship to $37,000, and 
for almost any trade this change would be justifiable. 
For conversion purposes under the Shipping Board plan, where new Diesel machinery 
must be had, it would appear that the larger boats offer the best possibilities. 
Before closing I should like to say that, while I have taken 200 days at sea and 165 
days in port per year for all the types except the tanker, this figure must, of course, depend 
on the trade the vessel is employed in. There are some trades where a ship is in port almost 
half the time, and it must be remembered that while a ship is in port it is not earning any- 
thing while the fixed charges are still going on. Therefore the more costly propelling ma- 
chinery is at a disadvantage as compared to a cheaper type running only a small portion 
of the time. 
While I consider the table (Plate 63) a good guide, the only way the best type can be 
selected is by a careful comparison of the different types in the particular trade an owner 
wishes to engage in along the lines given in the table, taking into account the character of 
the freight, length of voyage, freight rates, cost of fuel oil at ports of call, etc. 
DISCUSSION. 
Tue CHAIRMAN :—This paper, No. 12, entitled “The Selection of the Best Kind of 
Propelling Machinery,” by Mr. James L. Ackerson, Member, is now open for discussion. 
Mr. James C. SHaw, Member:—Mr. Ackerson is to be commended on his interesting 
paper, although it is open to controversy. It is regretted that he has failed to give us more 
basic data from which he draws his general conclusions. It would have been more illumina- 
ting, for instance, had he given more particulars in regard to the hulls for the size of ships 
he has under consideration. It would also have been of particular interest had he carried 
out his figures for the net earning capacity, both on deadweight and bulk cargo carried for 
the particular lengths of routes chosen. He refers to the unfavorable higher revolutions of 
the motor ship compared with the steamer as affecting propeller efficiency, which he states 
is in the ratio of 110 to 75. This proportion of revolutions, however, only holds good for 
a twin-screw motor ship and a single-screw steamer, and not for a single-screw motor 
ship and steamer, as is to. be implied. 
It should be pointed out, in this connection, that Messrs. Burmeister & Wain eight 
years ago ran trials on a twin-screw motor ship and a single-screw steamer for determining 
this point now raised by Mr. Ackerson. This was the motor ship Suecia, having a length 
between perpendiculars of 362 feet, a beam of 51 feet 3 inches, and a draught of 23 feet 
1% inches, corresponding to a displacement of 9,625 tons. The steamer was the Prinsessan 
Ingeborg, with a length of 360 feet, a beam of 48 feet 9 inches, and a draught of 21 
feet 10 inches, corresponding to 8,660 tons displacement.. The engines in the Suecia were 
of the earlier design of Diesel engines in which the high-pressure stage of the injection air 
