Performance of Partially Submerged Propellers 



displacement ships to hydroplane boats, where a fixed-water surface existed at 

 the stern. Typical of these developments was a patent issued in 1914 to W. H. 

 Farber for a hydroplane boat having two large surface propellers, Fig. 2. Dur- 

 ing and immediately after World War I, Albert Hickman, of Sea Sled fame, em- 

 ployed "surface" propellers on a sea- sled torpedo boat and on a 55-mph sea- 

 sled airplane carrier he developed for the U.S. Navy. Throughout these 

 developments Hickman had the active support of Adm. D. W, Taylor. It was 

 at this time that the first known model tests [ij were run both in open water 

 and self-propelled on a propeller designed to operate in the partially sub- 

 merged condition for a high-speed vessel. The propeller used in these tests 

 was three-bladed, with semiogival sections having a flat pressure face and 

 sharp leading edge. The test results showed high efficiency, comparable to 

 those fully submerged, but significantly reduced thrust and torque. The self- 

 propulsion tests brought forth the prime design difficulty with this type of pro- 

 peller, that of developing adequate thrust at the "hump" resistance speed to 

 assure successful operation of the craft over the desired speed range. 



Among the list of subsequent inventions was a patent granted in 1927 to 

 Gebers of the Model Basin in Vienna, Austria. He recognized that the partially 

 submerged propeller was limited to a relatively narrow range of load variations. 

 Thus, for application to displacement vessels it was necessary to provide some 

 means for operating at low speed or during heavy loads by incorporating a com- 

 bination of small fully submerged propellers with minimal appendages and large 

 "semisubmerged" high-pitch propellers as shown in Fig. 3. 



Insofar as practical applications of the partially submerged propeller are 

 concerned, they have, so far, been limited to the racing high-speed hydroplane, 

 which evolved into the well known "prop riders." The key developments oc- 

 curred in the period just before and immediately after World War II and resulted, 

 in 1948, in the pace- setting hydroplane Slo-Mo which increased the unlimited 

 speed record from 141.7 to 183 mph. The propellers employed are two-bladed 

 with wedge-type sections and are high-pitched. Besides being highly efficient, 

 these propellers also provide a lift, thus, to a point, establishing the magnitude 

 of their submergence; hence, the name prop riders. 



Much of the development previously recounted was carried out without the 

 benefit of model or "scientific" investigation, but was largely the result of "cut 

 and try" in actual applications. Laboratory research work on partially sub- 

 merged propellers has largely been confined to the problem of air drawing of 

 the normal displacement ship- screw propeller when the ship is ballasted, so that 

 part of the propeller is partially out of water. Osborne Reynolds was one of the 

 first to study this problem in a paper entitled "On the Effects of Immersion on 

 Screw Propellers" [2] in Transactions Institute of Naval Architecture 1874. 

 Since then, the results of a number of investigations have been published. The 

 publication by H. Shiba of Japan [3] provided the most thorough analysis, using 

 the widest range of experiments, and gave the most complete bibliography. He 

 tested 28 propellers in which area ratio, pitch ratio, number of blades, section 

 form, plan form, pitch distribution, and skewback were varied. In his experi- 

 ments he varied the tip emergence from to 20% of the propeller diameter. 

 Most of the blade sections were of the airfoil type, but he did include a circular 

 arc section with a flat pressure face and sharp leading edge and noted the 



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