Mystery Pictures

    Jesse Eaves found two of these objects in the sonar room storage closet.  The diameter is the same as a hedgehog spigot mortar. In fact, I thought that was what it was (with the nose highly modified). The orange paint is consistent with standard training coloring. The gray nose section is hollow. The silver piece in the nose is also hollow and the nut visible at the top appears to be a compression fitting. The fins are solid steel and not aerodynamically shaped on the leading edges. The tail section is a solid steel rod, not hollow like the hedgehog or mortar round. This example did not appear to screw apart like the second one we found. Part of the second one is visible in the next picture, as is the threaded seam.

    The second one was constructed of aluminum and screwed apart along the seam at the bottom. The entire body is hollow. 

    Overall, the machine work is well done and there are no visible welds that you would expect from a "home made" experiment.

    Any clues?  An experimental towed array? Would it work if we put a transducer in the nose/body and towed it behind the ship?

Response #1 from Jim Kennedy: I do not recall what the object that somewhat resembles a hedgehog might be. There were various attempts to make sonar transducers that could be lowered below thermal layers to improve detection of submarines which were going below these layers for stealth purposes. I doubt if that was this item's purpose.

Response #2 by Locke Wilde.  This is the towed body for the T-MK-6 Fanfare unit. This was the standard anti-torpedo decoy for decades. The control box is pictured in the sonar section of your web site. The control box sent cyclic on-off times and power to the 'fish'. The times were selected by the sonar operator, based upon doctrine. The fish was aluminum and steel and a real bear to work on. It occasionally failed and had to be replaced. Inside the fish was a spindle-rotor assembly that howled like a banshee when power was applied, causing the spindles to spin like crazy. The noise was very loud. Whenever we were in a potential torpedo danger zone, we streamed the Fanfare over the fantail.

Solved! 

This is the Mark 6 Decoy, called Fanfare. These noisemakers were post-WW2 replacements for the the Foxer and were towed behind the ship to decoy acoustic homing torpedoes like the German Naval Active Torpedo (GNAT). The Fanfare consisted of a winch and the two cable drums visible in the photo. Mounted on the fantail, the two noisemakers  were streamed much like the Foxer and towed behind the ship. The noisemakers were streamlined to reduce turbulence and were fitted with fins (visible in the top photo, but not in the black & white photo) to stabilize them in the water. Unlike Foxer, Fanfare was designed to emit sounds within the same frequencies as the ship's propellers, thus increasing the effectiveness of the system and making it harder for the enemy to use electronic filters on his torpedoes.

    Jesse also found three of these, all different dimensions, in the sonar pod area. Dimensionally, they are all within 3/4" of each other, but thought I'd mention it in case it was important. They each had about 100 feet of electrical cord attached. Although slightly corroded from salt water, the silver metal appears to be stainless steel. My pen is included to add a scale. Overall length is approximately 10 inches. Diameter is approximately 1-3/4".

A Transducer? 

Response #1 from Jim Kennedy: This object is most probably a unit of the ship's bathythermograph. We would lower this several times during each day to get a readout of just where the thermal layers were. It measured the temperature and the salinity of the water as it was lowered and produced a chart of its traverse of the depths. This aided in the search for submarines. 

Response #2 by Everett Schrader:  A bathythermograph is a device reeled over the side which measures temperature variation with depth. From this and related tables, sonar conditions could be determined. One of the interesting properties of a supersonic sound wave in sea water is it's ability to be bent or refracted when encountering a later of water of different temperature or salinity. This effect could be exploited by a submarine, allowing it to hide from a searching sonar beam.

Response #3 by Bill Ancker.  I was a sonarman 2nd class aboard the USS Francis M. Robinson (EDE-220). Its looks like a transducer for a sonar test set. The transducer was hung from the bow of the ship and lowered in the water and transmitted a test signal to the sonar set.

Response #4 by Phillip Carlton:  Bill Ancker is correct about your Mystery Picture #2. I also was a Sonarman 2nd class on the EDE 220 (1956 - 1959). I don't remember the name of the device, but it was used as a kind of a "field strength" meter. It is used to measure the output of the sonar and develop what kind of transmission pattern was being transmitted. This particular unit is the hydrophone. The hydrophone was connected to a volt meter which was capable of reading decibels. At that time we used a Fluke meter (Fluke is the manufacturer). The results of the device was plotted in strength vs. direction on a polar graph. This was not something we did every day. We were supposed to perform this test every 6 months. We were lucky if we did it once a year. 

Response #5 by Locke Wilde. The little mystery black cylinder in the stainless steel rig is in fact a sonar transducer used to tune up the sonar transmitter and receiver. We used to hang it over the bow through the bullnose chock until it hung midway down in front of the ship's hull sonar dome.