Sec. 7).12 



FIXED-APPENnACE DESIGN 



687 



sections and cut-up profiles, the angle /? of the 

 bossing termination often works out as close to 

 90 deg. In other words, the bossing stands nearly 

 vertical. It is usually difficult to provide adequate 

 docking support for the sterns of these vessels. 

 A logical procedure is to use the vertical bossing 

 as a support keel, since a high degree of strength 

 and rigidity is required in it to support the shaft 

 and propeller. Fig. 36. E of Sec. 36.7 indicates that 

 little or nothing need be sacrificed in the way of 

 form to provide the necessary flat surface on the 

 bottom of such an appendage. A bossing designed 

 to act also as a docking keel should have a slope 

 such that the line of action of the support force 

 from the docking blocks, at midwidth of the flat 

 under surface of the bossing, remains ivithin the 

 bossing until it enters the main hull. 



The fact that the propeller blades project below 

 the docking support surface and that the blocks 

 under the bossing (s) have to be built up higher 

 than the remainder may be taken care of by 

 modern (1955) drydocking procedures. 



73.12 Design Notes on Fixed Screw-Propeller 

 Shrouding; The Kort Nozzle. Certain screw- 

 propeller installations involving fixed shrouding 

 are described in Sec. 32.5 and illustrated in Figs. 

 32. D and 32. E. Propeller nozzles in general and 

 Kort nozzles in particular are described in Sec. 

 36.19 and diagrammed in Fig. 36. P. 



The detail design of Kort and other fixed 

 nozzles is intricate and specialized, so much so 

 that it can not be described adequately in the 

 space available here. Instead, there are given 

 a number of recent references which contain the 

 best description of this procedure available in 

 the Hterature: 



(1) Gutsche, F., "Fortschritte in der Entwicklung des 



Binnensohiffs mit Eigenem Antrieb (Progress in the 

 Development of Self-Propelled Ships for Inland 

 Waters)," Zeit. des Ver. Deutsch. Ing., 1935, p. 

 1155 



(2) BiJohi, G., "Possibility di Reoupero Delia Scia ed 



Esperienze sul Mantello d'Elica (Possibility of 

 Exploiting the Wake and Experiments with 

 Propeller Shrouding)," Ann. Rep. Rome Model 

 Basin (in TMB library), 1936, Vol. VI, pp. 91-98 



(3) Gutsche, F., "Einflusz der Gitterstellung auf die 



Eigenschaften der in Schiffsschraubenentwurf 

 benutzten Blattsohnitte (Influence of the Cascade 

 Position on the Characteristics of the Blade 

 Sections Used in the Design of Ship Screws)," 

 Mitteilungen der Preuzisohen Versuchsanstalt fiir 

 Wasserbau und Schiffbau, Berlin, 1938, No. 34; 

 see also STG, 1938, p. 125 



(4) Roscher, E. K., "WirtachaftUche und wissenschaft- 



liche Bedeutung unmantelter Schiffaschrauben 



(Economic and Scientific Importance of Shrouded 

 Ship Propellers)," STG, 1939, pp. 150-167 



(5) Dickraann, H. E., "Grundlagen zur Theorie Ring- 



formiger Tragfliigel (Fundamentals of the Theory 

 of Ring-Shaped Airfoils)," Ing.-Archiv, 1940, p. 36 



(6) Riddell, A. M., "The Theory and Practice of the 



Kort Nozzle System of Propulsion," INA, 1942, 

 pp. 87-114 



(7) Some design notes given by W. P. A. van Lammeren, 



RPSS, 1948, p. 267 



(8) Amtsberg, H., "Entwurfs- und Berechnungsverfahren 



fiir Kortdusen (Design and Calculation Methods 

 for Kort Nozzles)," Arbeitsblatt 5/1950/01 der 

 KdT, Berlin, 1950 



(9) Horn, F., "Teil A (Part A)," "Thooretische Grund- 



lagen und grundsatzlicher Aufbau des Entwurfsver- 

 fahrens (Basic Theory and Design Fundamentals)," 

 STG, 1950, Vol. 44, pp. 141-169, with a list of 8 

 references on p. 169 (in German) 



(10) Amtsberg, H., "Teil B (Part B)," "Praktisches 



Auswahlverfahren fiir Optimale Diisensysteme 

 (Practical Selection Method to Determine 

 Optimum Nozzle Systems)," STG, 1950, Vol. 44, 

 pp. 170-206 (in German) 



(11) An excellent summary of these two papers is given 



(in German) and a most workable design pro- 

 cedure, with examples, is found in "Handbuch der 

 Werften (Construction Handbook)," published by 

 Hansa in Hamburg, 1952, pp. 67-88. On page 88 

 there is a bibliography of 14 items. 



(12) An NACA 4415 section is recommended for a Kort 



nozzle by F. Horn and H. Amtsberg; it is shown 

 by W. Henschke, in "Schiffbau Technisches 

 Handbuch (Shipbuilding and Ship Design Hand- 

 book)," 1952, pp. 165-166. The nozzle section and 

 the sketch of Fig. 73.1 is adapted from Fig. 44 on 

 p. 167 of the Henschke reference. 



(13) "Triple-Screw Ohio River Tugboat John J. Rowe," 



SBSR, 17 Nov 1955, p. 641. The three propellers of 

 this craft, 7.67 ft in diameter, are each enclosed 

 in Kort nozzles, with a steering rudder abaft each 



Direction of Inflow 

 When Goinqj Ahead 



Plane of Propeller Disc 

 Fig. 73.1 Definition-Design Sketch for Kort Nozzle 



