As a practical application of the method given in the preceding section, the author investigates the effective breadths in the following cases of plates with parallel sitiffeners, corresponding to the most usual ship structures, such as decks, shells and bulkheads etc., i.e.
1. with a concentrated load on every stiffener, both ends being supported or fixed.
2. with a uniform pressure over the plate, both ends being supported or fixed.
3. with a uniformly increasing pressure over the plate, both ends being supported or fixed.
It is found that the statically indeterminate bending moment along the stiffener due to the pressure over the plate, can be practically substituted by the bending moment along a “beam” carrying the whole pressure as a direct load, provided that the scantlings of the plate and stiffener are of the usual proportions. As a result of this, the applications as well as the calculations of the effective breadths are much facilitated.
The results of the calculations are given in curves, by which the properties of the effective breadths are deduced as follows; the effective breadths (a) are not constant along the lengths of the stiffeners, (b) but vary with the end conditions, (c) with the distribution of the loads, (d) and with the spacing of the stiffeners, (e) and are much affected by s/l, (f) slightly by d/l, (g) and scarecely by t'/t, where t is the thikness of the plate, s, l and t' are the spacing, the length and the thickness of the stiffener respectively, and d is the depth of the flat bar stiffener or of any equivalent flat bar stiffener. For the purpose of calculating the deflections of the stiffeners, however, the effective breadths may safely be assumed to be constant throughout the lengths of the stiffeners and equal to their values at the point of application of a concentrated load (case 1), or at the centre of the stiffener carrying the uniform load (case 2 & 3).
As a standard for the practical use in shipbuilding, the author proposes to use thecurves of the effective breadths in the case of d/l=1/20, t'/t=1.

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The effect of fouling upon the resistance of ships was examined by the towing experiments with the ex-destroyer Yudachi at various stages of fouled surface after 4, 75, 140, 225 and 375 days out of dock; the speeds experimented with were up to 20 knots at each fouled condition.
After these experiments the author studied the effect of fouling on the propulsive efficiency applying the above-mentioned results of towing experiments to the trial results of first-class destroyer.
The chief conclusions drawn from these investigations are:
(1) Frictional resistance of ships having fouled bottoms can be expressed by the following formula:-
R_f=fSV^2•1,
where R_f=frictional resistance in kg.,
S=wetted surface area in m².,
V=speed of ship in knots,
f=coefficient of frictional resistance which varies with the weight of fouled substances per unit area as shown in Fig. 6.
(2) Propulsive efficiency is affected scarcely by the bottom fouling.

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When the rotation of a ship's screw is reversed in its forward motion, the blade elements are generally in stalled condition. In such a condition, the action of the screw propeller is analysed, and the thrust in the aftward direction is obtained.
Assuming the virtual mass to be one-fifth of that of the ship, and the resistance to be proportional to the square of the velocity, the formulae for the time and the distance in the decelerated motion are developed in this paper.

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Applying the new formula for calculating economic efficiency of Diesel freighters, which is introduced by the author, he investigated the economic efficiency of 24 Diesel freighters of different size and speed under four conditions of different load, runningbetween ports of four different mileage, i. e. economic efficiency for 384 cases altogether is calculated.
Drawing several diagrams by plotting the results of calculation, he obtained his general conclusion regarding the economical speed and size of cargo vessels.
The contents of the paper are as follows:-
Foreword.
Definition of economical speed and size, economic efficiency of Diesel freighters and the fundamental formula for calculation of such economic efficiency.
Limits of calculation of economic efficiency of Diesel freighters.
Principal particulars of Diesel freighters for which economic efficiency is calculated.
Process of calculating earning, expenditure and economic efficiency of Diesel freighters.

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