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April, 1909 7 oe 3 8 oO tt 5 <i zg 4 | Bey. i) | TAE Marine REVIEW Windlass -- _Anchors ete Scale for Length castle, have when loaded equally be- tween those two points, or throughout the waist of the ship, a natural tend- ency to sag, in other words to draw more water amidships than at the ends, due to the fact that there is an excess of: biioyancy over weight at both bow and stern, and particularly at the . bow where there is a long empty space, which. practically has no extra weight _ except that due to the windlass, chains and anchors, and throughout the cargo space there is an excess of weight over buoyancy, resulting ta an upward pressure at each end of the ship and a downward pressure amidships, all tending to distort the form of the ves- sel by sagging and causing straining of the hull materials, the lower parts being put into tension and the top sides and deck stringer into compres- sion, then when the vessel is unloaded the opposite conditions take place, there being an excess of buoyancy over weight amidships, the upper works are in tension and the bottom in compres- Sion. "This continued reversal in the _ direction of the straining forces on the hull is a very severe test on the Tivets and on the calking, not only be- cause of the direct action of the ten ion and- compression stresses 'but also cause of the action of the forces from the sagging of the hull 545/x 55x 31' 1's « « Wt.and Bey 1= 2.52 Tons Ft. LSM 2 | Las Goes MARINE REVIEW. « « Shearing Force 1'= 137.6 Tons « « Bending Moment 1 = 11254 Ft. Tons Mt.I.Section 3% 377,358 Sq. In. x Ft." ; * Displacement at 8/Aft, 346 Fd. 4128 Tons ; : Neut. Axis above Keel 6.7 Ft. «> « « Below Stringer 24.3 « poem "STRENGTH CURVES « a FOR Ge) eee NO. 340-1 bas Le 377 358 = 3.26 eee ae ea ; A.S.B.CO. « G. which tend to distort the form of the vessel or to alter the relations of depth and beam, the effects from the latter cause are mostly noticeable at the bilges because 'of the bellows-like ac- tion that takes place. The Distribution of Load. For purposes of illustration, I have taken two types of boats only, one 580 ft. long with 12 ft. center hatches, ASQ ft: lone with 24: Tf. hatches, as being _ typical and center -of lake craft engaged in the ore trade, as in similar vessels the distribution of the ore fore and aft will vary in the same proportion to the total load as is shown by the diagrams for the two types described, or to put it into figures, 'about 36 per cent of the load should be located in the forward third of the cargo hold, about 30 per cent in the midship third of the hold, and about 34 per cent in the after third of the hold, and this distribution will be found to give the minimum amount of strain on the hull, and at the same time give the vessel her proper: sailing trim, 3 to 6 in. by the. stern at the loading port. ES In the case where usual space between the hatches, as for instance, in some boats with 24 -t. center hatches, two of the hatches may be 36 ft. apart centers; and in other STILL WATER, LIGHT JUNE 5, 1905- : omitted, into alternate . the alternate, were is an un-_in the case of whalebacks, either steam ily 12 ft. centers, there is often one hatch making two of them 24 ft. the load that would other- | into this space should be dis- -- tributed in the two adjacent hatches so as to center it as nearly as possible where it belongs. - A point in connection with the A ft. center hatch boats is the fact that it is < not necesary to load each hatch with -- its allotted number of tons so long as the sum total in two adjoining hatches | is correct, for with this close spacing of hatches, when the ore is first loaded hatches it will run and under the hatch between | probably to a depth of from 4 to 6 ft, with the resale tiar there may be only half the amount of © ore that was put into the alternate hatches need be put into this interme- diate hatch, as it is, already has had the other half from the fate on either side of it. Similar Treatment ee Tow: Barges. In the case of tow barges of the usual form the loading ought to be similar to that given for steamers, the heaviest weights at the two ends, but centers, wise go meet together boats or tow barges, that have their . model very much cut away forward with a consequent loss of buoyancy at that point, the proportions for the di