Marine Propellers

Marine Propellers

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1887 edition. Excerpt: ...placed. As the boat has only 12 inches draught of water one-fourth of the diameter of the propeller is above the water level. As soon as the propeller starts, however, water is drawn up into this tunnel and the air is expelled, after which the tunnel remains full of water and the propeller works completely submerged. There is no loss of power involved in lifting the water this 4 inches, because in falling it gives out the work employed in raising it. There is an incidental convenience in this arrangement. An air-tight door is placed at the summit of the tunnel, which can be taken off from inside the boat. As soon as air is admitted the water falls to the level of that outside and the propeller is partially emerged, thus offering peculiar facilities for examination and for allowing it to be cleared if fouled. In the case of twin screws this operation can be performed upon one propeller while the other is still kept going slowly. Five large steamers, 140 feet by 21 feet, and i foot 9 inches draught of water, are being built upon this principle by Messrs. Thornycroft & Co. for the Nile expedition. They will be propelled by two screw-turbines of 32 inches diameter, raised in tunnels in the manner described. A launch built in 1884, 56 feet long and 15 inches draught of water, attained a speed of l6 knots with one screw-turbine 20 inches diameter. Since the delivery of these lectures, one of these vessels has been tried upon the measured mile, and obtained a speed of i si knots an hour. APPENDIX. NOTE A. When a propeller is not immersed sufficiently to prevent it from drawing down air, it is probable that centrifugal action takes place, and that the column of water driven astern takes the form of a cone with the screw for an apex. more

Product details

  • Paperback | 28 pages
  • 189 x 246 x 2mm | 68g
  • United States
  • English
  • black & white illustrations
  • 1236884434
  • 9781236884435