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Light. Sufficient light must be provided for the proper tending of animals at all times.

Ventilation for horses. Under deck canvas bags should be fitted to ventilators, provided with iron rings at bottom, and reaching within 18 inches of the deck under foot.

In estimating the weight of cattle fittings, comprising cement, cattle pillars, footlocks, head and rumpboards, castings, etc., the following will be found reliable:

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In estimating for displacement purposes, the weight of a ship's hull is usually divided broadly into two parts, viz.: (1) finished steel and (2) weight of wood and outfit.

There are various methods by which the steel may be estimated approximately, but where great accuracy is required the weights of the structure should be calculated in detail systematically, and the results summarized in convenient form for future reference.

The arrangement shown in the table will be found useful when the cost estimate is being figured, as the parts of structure itemized are those which generally show variations in labor prices. The summary of material is given for a similar reason, and also for the variation in scrap between the different items.

Of course the structural parts considered in the table must each be dealt with in detail, but by having some such form as that here presented the chances of omission will be minimized, the weights put in a convenient form for prime cost, and also usefully arranged if the centre of gravity should afterwards require calculating.

The most common method to approximate the weights of hull steel when there is insufficient time to figure in detail, is to take the ratio between the weight and the cubic number of a known

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vessel of similar type and degree of fineness and use the coefficient so obtained on the proposed ship. For example, a known ship of length 330 feet, breadth 41′ 9′′, and depth moulded 28′ 3′′, has a total steel weight of 1,680 tons, then

LX BX D 330 x 41.75 × 28.25

SX 100

1680 × 100

.431 coefficient.

The proposed steamer is 320 × 42 × 291 and the coefficient of steel weight being .431, we get

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This rough method requires good judgment and practice, as it is obvious from the example given that although 1,709 tons is a fair approximation it is still too heavy.

Recognizing this fact and the necessity for a quick approximative rule which would give fairly close results, Mr. J. Johnson (vide Trans. Inst. Nav. Arch. Vol. 39) devised a method based on Lloyd's longitudinal number (modified for some types) and by plotting down known steel weights opposite their numeral, drawing curves through the mean values of each type, he analyzed them and found their equations. By means of curves prepared in this way from actual weights, the amount of steel is easily read off and the increase or decrease due to an alteration in the numeral is readily seen. Johnson's formula is as under,

where

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W= Finished weight in tons of iron or steel used in hull construc

tion.

N = Lloyd's longitudinal number modified as follows: In 3 decked vessels the girths and depths are measured to the upper deck without deduction. In spar and awning decked vessels the girths and depths are measured to the spar or awning decks respectively.

In one, two or well decked vessels the girths and depths are taken to the main deck in the usual way.

c and K are coefficients varying with different types.

x is an exponent, also varying with different types.

Table Giving the Mean Values for c, K, and x for Vessels Built to Lloyd's or Veritas' Highest Class.

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The twisting moment T would then be

T=AV2X sin 35° × 3.19 × 1 = inch-pounds,

and equivalent diameter of stock "d" in inches with a fibre stress k of 5,000 lbs.,

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The subjoined table gives torsional moments with their equivalent diameters calculated as above, with * 5,000 lbs. per square inch, being a sufficiently high fibre stress to allow for a twisting stress, alternating between right and left, for wrought iron.

In a rudder of rectangular form the centre of pressure from the leading edge is equal to

b (.195+.305 sin a) = bc,

where b is the mean breadth of rudder, and c a coefficient, as under.

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Rudder Stocks per Lloyd's Rule.

The following is the formula prescribed by Lloyd's Register for estimating diameters of rudder stocks, but in no case must the result be less than the tabulated rule size, which see. It should not, however, be used unless the ship is intended for classification in that society's register, as for very high speed vessels the results obtained would be too weak. One of the factors is draught of water, which has little or no value in computing the strength of rudder stock for a rudder of ordinary type hung on a post. Of course, in a rudder with no bottom bearing, as in destroyers and such craft, the case would be entirely different, as then the stock would be figured for bending, the moment for such being much in excess of the torsional one.

* Take 7,000 lbs, for steel.

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NOTE.-Diameters are calculated to nearest eighths of an inch with a

fibre stress of 5,000 lbs.

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