The naval constructor
THE NAVAL CONSTRUCTOR
A vade mecum of ship design for students, naval architects, shipbuilders and owners, marine superintendents, engineers and draughtsmen.
BY GEORGE SIMPSON
NEW YORK, D. VAN NOSTRAND COMPANY, 1918
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PREFACE TO FIRST EDITION
This handbook has been prepared with the object of supplying a ready reference for those engaged in the design, construction, or maintenance of ships, - such a work as should give simply and concisely, information on most of the points usually dealt with in the theory and practice of marine architecture, and in addition much that is new and original. Under the latter heading should be included the chapter on Design and many of the tables of standardized fitting details, etc.
The Freeboard tables have been explained and their application simplified by working out examples embracing the various types to which freeboards are assigned, including the modern shelter decker, for which rules have recently been issued.
While it would have been possible to enlarge greatly on what the author has attempted, it has been deemed prudent at present to restrict somewhat the scope of the book, although at that, it will be found much more comprehensive in its character than existing works on naval architecture.
It has been the author's aim to eliminate all obsolete matter and antiquated data, and to bring the book right in line with present day requirements.
How nearly he has come to this ideal will be shown by the reception accorded by the profession.
CONTENTS
- Ship Calculations
- Strength of Materials
- Fittings and Details
- Rigging and Ropes
- Equipment
- Miscellaneous
- Tables
FRAMING
In ships having ordinary floors the frames are invariably run in one piece from centre line to gunwale, and where channel bars or bulb angles are employed with this construction, the floor plates may be reduced in consideration of the excess strength given in their wake. Vessels having a double bottom on the cellular system need only have angle frames on the deep floors with flanges sufficient to take the size of riveting required. Forward in the flat of bottom in full vessels these should be doubled inside tank and in addition local fore and aft stiffening fitted to reinforce against "pounding." Where vessels are classed, as they mostly are, the scantlings of the frames are obtained from the rules of the classification bureau. The angle bars of which they are made is always one with unequal legs, the larger flange standing vertically to the shell plating to obtain the greatest section modulus in the direction of the pressure.
Where frames are cut at margin plates of inner bottoms or at water tight flats, efficient bracket plates of such dimensions as will permit of riveting to develop the strength of frame bars would be fitted. See Fig. 163 and 169. In wake of flats where bracket knees are objected to on account of the broken stowage created, or their interference with cabin arrangements, the framing may be continuous and smithed angle collars or preyed plate chocks fitted around them to ensure water tightness as in Fig. 160. For simplicity In forming collars, frame and reverse has flange, may be cut off and the frame bar doubled for a short distance above and below the flat as compensation as in Fig. 151.
Where main frames are stopped at weather deck when the bridge house or superstructure requires a bar of smaller section, the connection between weather deck stringer and frame may be completed with a spirketting plate in lieu of the ordinary bracket knee where the latter would encroach on the berthing space, as shown at Figs. 162 and 163.
The inboard member of a ship's framing, called the re verse bar, whose functions are to provide a flange where on to fasten the ceiling, or lining, and to give the necessary section modulus by adding area at a point subjected to corrosion and rough treatment, is commonly made of angle section or by the employment of channel bar for the framing. Id steamers, however, under about 100 feet besides being good construction to omit the reverse bar altogether and increase the sided flange of frame angle to give an equivalent I. A saving in material, riveting and bending will thus be effected.
The practice in vogue for many years of placing the frame and reverse bars back to back has given place to that of fitting them bosom to bosom where deep framing is adopted, as by this method the beam knees can be fitted without linering in wake of reverse frames.
FLOORS
The deep plates riveted to the bottom framing of ships and known as the floors, are placed there to resist the transverse stresses to which the bottom plating is subjected, due to the great water pressure externally applied, and the inside forces created by the weight of the structure and cargo.
Ordinarily in ships without an inner bottom these are of a size based upon the breadth and depth of the vessel and carried in a fair line up the bilge to a height equal to twice the centre line dimension as in Fig. 165. It will be seen that this contour at the bilge necessitates furnacing the tail ends to bend them to the required curve, a costly and therefore an objectionable feature. For this reason ordinary floors should be increased in their sided areas and carried straight across, striking the bilge at a point somewhat lower down than with the curved floor. This method permits of the floor being flanged across top in lieu of fitting a reverse bar, although some of the classification bureau penalize flanging plates to the extent of adding one-twentieth to their thickness; this need not, however, be made unless where specifically required and for that reason cheaper, lighter, and equally efficient construction will be obtained.
In small freight steamers and barges a strong and inexpensive floor is obtained by using structural channel section thus eliminating the riveting to frame and reverse bar altogether.
Floors in inner bottoms are almost entirely fitted as deep solid plates in one piece from centre vertical keel to margin plate, lightened with large manholes to cut out superfluous material and provide access to the various compartments into which the bottom is sub-divided by the floors and intercostal girders. Deep floors should be lapped to the bottom frames just sufficient to take the riveting. In wake of watertight bulkheads or at ends of ballast tanks where the floors are watertight, no holes whatever must be cut in them. The margin plate of inner bottom being continuous, is connected to the main frame by a large bracket plate or tail piece, and by double angles having a specified number of rivets and a gusset plate at top, or in the largest vessels a continuous stringer. The connection to the siding flange of main frame is by lap of sufficient width to take the riveting. See Figs. 167 and 158.
At the ends of the vessel where the waterline at top of floor would necessarily be comparatively narrow, increased depth must be given to provide compensatory area and also ensure sufficient width to clip the centre keelson to floors. In the fore peak this additional depth is required to resist buckling and panting, and generally to give local stiffening at a part subjected to unusual stresses. It is also necessary to increase the floors considerably in depth in after-peak, owing to the severe stresses encountered when the propeller “races” and the stem is in. air.
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Where frames are cut at margin plates of inner bottoms or at water tight flats, efficient bracket plates of such dimensions as will permit of riveting to develop the strength of frame bars would be fitted. See Fig. 163 and 169. In wake of flats where bracket knees are objected to on account of the broken stowage created, or their interference with cabin arrangements, the framing may be continuous and smithed angle collars or preyed plate chocks fitted around them to ensure water tightness as in Fig. 160. For simplicity In forming collars, frame and reverse has flange, may be cut off and the frame bar doubled for a short distance above and below the flat as compensation as in Fig. 151.
Where main frames are stopped at weather deck when the bridge house or superstructure requires a bar of smaller section, the connection between weather deck stringer and frame may be completed with a spirketting plate in lieu of the ordinary bracket knee where the latter would encroach on the berthing space, as shown at Figs. 162 and 163.
The inboard member of a ship's framing, called the re verse bar, whose functions are to provide a flange where on to fasten the ceiling, or lining, and to give the necessary section modulus by adding area at a point subjected to corrosion and rough treatment, is commonly made of angle section or by the employment of channel bar for the framing. Id steamers, however, under about 100 feet besides being good construction to omit the reverse bar altogether and increase the sided flange of frame angle to give an equivalent I. A saving in material, riveting and bending will thus be effected.
The practice in vogue for many years of placing the frame and reverse bars back to back has given place to that of fitting them bosom to bosom where deep framing is adopted, as by this method the beam knees can be fitted without linering in wake of reverse frames.
FLOORS
The deep plates riveted to the bottom framing of ships and known as the floors, are placed there to resist the transverse stresses to which the bottom plating is subjected, due to the great water pressure externally applied, and the inside forces created by the weight of the structure and cargo.
Ordinarily in ships without an inner bottom these are of a size based upon the breadth and depth of the vessel and carried in a fair line up the bilge to a height equal to twice the centre line dimension as in Fig. 165. It will be seen that this contour at the bilge necessitates furnacing the tail ends to bend them to the required curve, a costly and therefore an objectionable feature. For this reason ordinary floors should be increased in their sided areas and carried straight across, striking the bilge at a point somewhat lower down than with the curved floor. This method permits of the floor being flanged across top in lieu of fitting a reverse bar, although some of the classification bureau penalize flanging plates to the extent of adding one-twentieth to their thickness; this need not, however, be made unless where specifically required and for that reason cheaper, lighter, and equally efficient construction will be obtained.
In small freight steamers and barges a strong and inexpensive floor is obtained by using structural channel section thus eliminating the riveting to frame and reverse bar altogether.
Floors in inner bottoms are almost entirely fitted as deep solid plates in one piece from centre vertical keel to margin plate, lightened with large manholes to cut out superfluous material and provide access to the various compartments into which the bottom is sub-divided by the floors and intercostal girders. Deep floors should be lapped to the bottom frames just sufficient to take the riveting. In wake of watertight bulkheads or at ends of ballast tanks where the floors are watertight, no holes whatever must be cut in them. The margin plate of inner bottom being continuous, is connected to the main frame by a large bracket plate or tail piece, and by double angles having a specified number of rivets and a gusset plate at top, or in the largest vessels a continuous stringer. The connection to the siding flange of main frame is by lap of sufficient width to take the riveting. See Figs. 167 and 158.
At the ends of the vessel where the waterline at top of floor would necessarily be comparatively narrow, increased depth must be given to provide compensatory area and also ensure sufficient width to clip the centre keelson to floors. In the fore peak this additional depth is required to resist buckling and panting, and generally to give local stiffening at a part subjected to unusual stresses. It is also necessary to increase the floors considerably in depth in after-peak, owing to the severe stresses encountered when the propeller “races” and the stem is in. air.
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