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At random: During their wartime operations submarines have engaged in some unusual maritime actions. One undersea craft slugged it out with the infantry and field artillery while other submarines destroyed a zeppelin, a bus, and a railroad train.
Periscope and mast wakes.
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Hairball
Posted 2009-11-17 12:22 PM (#32486)
Senior Crew

Posts: 168

Location: St. John's, Newfoundland.
Subject: Periscope and mast wakes.

On all the films I’ve seen of a submarine running at Periscope Depth the wake created stands out like a sore thumb.

Why didn’t someone design the masts so that they were, ‘streamlined?’ In other words a sharp leading and trailing edge.

I would suggest that it would be a simple engineering exercise to achieve this.


Cheers, Hairball
Chew
Posted 2009-11-19 5:57 AM (#32520 - in reply to #32486)


Mess cooking

Posts: 48

Location: No. CA
Subject: RE: Periscope and mast wakes.

Size matters for periscopes. The larger they get the easier it is for a lookout to spot them, even without the wake.

Bob
PatH
Posted 2009-11-19 12:02 PM (#32531 - in reply to #32486)


Great Sage of the Sea

Posts: 618

Location: Issaquah WA, USA
Subject: RE: Periscope and mast wakes.

The navy also designed 'teardrop' sleeves for the periscopes which helps to reduce the wake, and now they have gone to 'photonic' masts, basically a retractable platform on a pole with all sorts of gizmos and gadgets on it.  One huge advantage is it can take in a 360 view almost instantly and they retract below the surface, and the crew can then look at the digital data collected and review it at their convenience, over and over again if necessary.  Slower speeds also really cut the wake problem down as well.
SOB490
Posted 2009-12-16 5:39 AM (#33087 - in reply to #32486)


Old Salt

Posts: 489

Location: San Freakcisco CA area
Subject: RE: Periscope and mast wakes.

In all the exercises where we provided services to VP squadrons, the #1 detection device they used, according to the aviators, was the MK-1 eyeball and an extended periscope was the #1 cause of the wake they could detect.

Some of the GUPPY-II and GUPPY-III boats had a teardrop cross section mast called the "EDO Fairing" that could be raised to help streamline #1 scope - in those days, the main scope was a Kollmorgen 8B.

While the EDO Fairing did give a little bit more stability from hydrodynamic vibration, it really didn't do anything so far as the wake was concerned. It was intended to help prevent vibration because the GUPPY boats were capable of greater submerged speed and with 4 batterys instead of 2 (504 versus 252 cells), vibration was a problem.

The scope barrel may be a simple engineering problem - i.e. a 7-5/8" OD X lengths up to 60 feet depending upon Type. But it was a bitch to manufacture - at one point, only Inland Forge had the capability to manufacture those barrels to the tolerences necessary for submarine use. I don't know whether there are any more companies with that capability today, as Kollmorgen bought them when the Navy was developing the Type 18 in order to freeze out Itek and Sperry Marine Systems.

Plus - remember, the "conventional" scopes prior to the current electro-optic masts had to rotate 360 degrees in the bearing and seal/packing. Thus, the barrel had to be round.



Edited by SOB490 2009-12-16 5:44 AM
rover177
Posted 2010-02-23 2:19 PM (#35150 - in reply to #32486)
Master and Commander

Posts: 1241

Location: Wollongong, NSW
Subject: RE: Periscope and mast wakes.

A submarine transiting at PD with masts up will leave a substantial wake; a submarine in the middle of a PD attack will virtually leave no wake because of the correct use of the periscope. On a glass sea, speed has to be at almost stopped trim but with a slight chop, the attack periscope is very difficult to see, particularly from the ship being attacked.
When we conducted ASW training for aircraft we generally had to expose far more mast than we would in normal patrol operations; a quiet diesel is incredibly difficult to find. Back in the days of unguided weapons we had to get in close; the number of simulated submarine attacks against alerted forces where the target did not get a sniff of the attacking boat could fill volumes.
We got some very good close range photos of American carriers during Rimpacs etc; some good screw and rudder shots as well.
BlackBeard
Posted 2010-03-14 12:09 AM (#35661 - in reply to #32486)


Great Sage of the Sea

Posts: 566

Location: Inyokern, Ca.
Subject: RE: Periscope and mast wakes.

Periscope Mast detection has made advances tenfold in the last 20 years. Where I worked (China Lake), our sister branch worked wonders in it's advancement. I left there in the late 90's. Luckily, since we are a USN laboratory, the information is shared to the Naval Engineers so they can make improvements to our systems to compensate. But believe me, the systems recently deployed are extremely effective.
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