346 NICHOLLS'S SEAMANSHlr AND NAUTICAL KNOWLEDGE
MISCELLANEOUS SHIP WEIGHTS AND MEASUREMENTS
Metals. Woods.
Steel 489 Ibs per cubic foot Oak 34 Ibs. per cubic ft.
Copper 550 „ Pitch pine 40 „
Zinc 445 „ Elm 45
Lead 712 „ Teak 50 „
SHIP LIFE-BOATS.
LxBxDxCoefficient = cubic capacity. Average coefficient = '6
Cubic capacity -f- ] 0 = maximum number of persons to carry
„ = volume of buoyancy tanks in feet
CARGO SHIPS MUST CARRY—
Life-boats under davits on each side to accommodate all hands.
Life-buoys.—Six painted white and red, at least 3 fitted with seJf-
ignition lights, one buoy to be carried on each side of the
*. bridge and one on each side of the ship with a 15-fathom
life-line attached to it.
Tests.—Life-buoy to float 32 Ibs. of iron in F.W. for 24 tours.
Life-belt to float 16J Ibs. of iron in F.W. for 24 hours.
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MATERIALS.
Chain.—Breaking strength about 30D2 where D is the diameter.
Proof load „ 12D2
Safe working load „ 6D2
Wire.—Breaking strength about 2C2 for 12 wires per strand.
„ 30* 24
„ 3J02 37
Working load about one-sixth the breaking strength,
Manila.—Ultimate strength about JC2 and one-sixth ultimate strength
is a safe working load; yC2 for occasional lifts.
nW
Purchases .—General equation. SxP=W-\----where S is the pull on
hauling part, P the theoretical power of the purchase,
W the weight to be lifted, n the number of sheaves in tbs
purchase.