"Note that the MicroMir kit does not feature the prominent under bow bulge to house the BQR-4 passive sonar. This sonar was useless above 8 knots due to self-noise from the submarine. It was moved up to the top of the bow on Seawolf (SSN 575).
You can see the BQR-4 installation here:
http://navsource.org/archives/08/571/0857133.jpg and here:
http://imgur.com/9QIo0guSome more bow shots from an R/C model project on 571 by Matt Thor:
http://s264.photobucket.com/user/mdthor ... 3.jpg.html
http://s264.photobucket.com/user/mdthor ... 4.jpg.html
http://s264.photobucket.com/user/mdthor ... 3.jpg.html
http://s264.photobucket.com/user/mdthor ... 8.jpg.html"
The lower chin mount dome you're referring to is for the AN/BQR-2, installed on both the Nautilus and Seawolf. The BQR-2 had 48 phones in a circular array, which even though it was circular and hung level with the keel, still had about a 60 degree baffle area. The BQR-4 was also installed on both boats; it had 58 hydrophones in a conformal array which was housed inside the superstructure above the torpedo room. The BQR-4 had a lower frequency response than the BQR-2, so it was the primary passive long range search sonar when conducting narrowband searches. It was basically an upgraded German WWII design, with 58 tube-based pre-amps mounted in little trays in the upper section of the (single) console. The compensator switch (which connects the hydrophones to the audio processing circuits) was manual - the steering wheel had the comp switch attached directly to it, whereas the BQR-2 was electrically turned and housed in a cabinet in another compartment. Very simple and effective system, though an antique even in the early 70's.
The analog BQR-2 was later replaced by the digital BQR-21, (built by Honeywell in West Covina) which used virtually the same style 48-phone circular array. All of the old boomers got it --except for the 598 class.
As a projects boat, the Seawolf had its BQR-2 upgraded to the 21 during its final overhaul. Likewise, Parche had one mounted above the engine room. It was a great little system; easy to operate, decent digital trackers, and very reliable. If it did fail, it was easy to troubleshoot, unlike the BQR-2 which required a heavy background in synchro theory. Nautilus also carried the BQS-4 active sonar, with it's 'ducer mounted in the chin mount. The BQS-4 was part of the BQR-2 suite. In the case of the Seawolf, in her final configuration, she had a surface ship SQS-51 active sonar (mounted upside down because of the active beam lobe offset) in a topside dome mounted on the bow. Like the BQS-4, it was basically useless unless you wanted to give away your position. It was ALWAYS tagged out with the transmitter cabinet fuses removed prior to a mission.
The BQH-2E was installed on both Nautilus and Seawolf. It was a single-channel LOFAR gram display/processor. Pretty grim compared to the 3-foot wide BQQ-3 Gram-makers the big-boy SSNs' carried, but the ozone output caused by the stylus burning the paper on each update pass was considerably less on the BQH-2. And sometimes, less is good! (Hey, it was bad enough being trapped in a space the size of a master closet with a watch section of chain-smokers for six hours at a stretch!)
I live in CT and always enjoy taking friends and family aboard the Nautilus for tours, especially for a peek inside the sonar shack.
CCC