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Appendix E


The last Guppy submarine in the service of the USN was the GII > GIII USS Tiru 416, decommissioned and stricken 1 July 1975. She was the odd one out having had one engine removed at some point early in her service and only being extended in the GIII program by 12.5 feet while the rest were extended by 15 feet. She was also one of five Fleet Submarines laid up incomplete after WW2 and completed as Guppy GII in 1948.

The Guppy submarines served the USN well over a lengthy period of the Cold War, but obviously their roles changed as the SSN came into front line service and no more diesel-electric boats were built for the USN. However there was always the requirement for another submarine and the Guppy seemed to have filled the need.

Much the same situation applied in the Royal Navy with boats built in WWII still in service many years later.

Concluding this Appendix I is a more modern anecdote, that provides a brief but clear picture of diesel-electric operations, some two decades or more after the first Guppy appeared. The very quiet, post war British OBERON class played a significant role in the Cold War and the Falklands conflict.

Until fairly recently, improved 'O' class formed the RCN submarine fleet. see Appendix F

On Ron Martinis BBS, Bob T answered a query about the derating of the Fleet Submarine engines from 5400 bhp to 4610 bhp.

As best as I can recall there was an engine derating when snorkelling due to higher back pressure. Also, when snork was installed the compression ratio was reduced by replacing the pistons. The "old" pistons had profile called "pear shape" and the new pistons had a profile called "Mexican hat shape". The reduction in CR was to allow for higher exhaust back pressure. Not really sure, it was a long time ago.

Patrick Householder served as an Electrician's Mate between 1962 and 1963 aboard the USS Chopper (SS-342), a GIA Guppy boat (Fig 8)

On the surface the Guppy boats were somewhat slower than Fleet boats because the knife bow would either cut through or bury itself in the rollers, while the original clipper bow would rise over much of the wave action. Of course three engined Guppy boats were 3-4 slower on top due to less generated juice. While on the snorkel we could run two engines max (due to the volumes of air required to take and expel). The boat could run at 14 knots on a series bell, but we normally ran at about 7-9 knots and 5-6 snorkelling on battery charge. I suppose 16 knots on a series bell on a 4-battery boat might be doable. I don't recall that on the Diodon, however. Tactically, you'd sound like a full loaded trash truck travelling at high speed down a bumpy road to a sonar man within 50 miles

At higher underwater speeds, depth control became dicey and if you got a significant down angle, the flat surface of the deck would act as a diving plane, pushing you deep and at a severe angle if you were not on your toes.

This is what basically happened to Chopper when she made her last dive, which terminated at 1,011 feet with an 80 degree plus down angle.

Cheers Pat.

Note The USS Chopper was a constructive loss after this remarkable dive and recovery below crush depth.

From Ron Romer Oct 2003, re' USS DOGFISH (SS350), a GuppyII conversion

The forward battery (which was 1 and 2 batteries) were connected in parallel and the same for the after battery (3 and 4).

Normal operation was fwd group and after group in parallel. When we went into series, the fwd was put in series with the after battery. We had two discharge rates, one hour rate and the 1/2 hour rate. I believe the 1/2 hour rate was 6675 amps. The scanners were on auto and if individual cell voltages got to a certain low, the rate was decreased.

Note the figure of 6675 amps that Ron apparently stated from memory, see Appendix A.

From John Clear EMC (SS) USN ret'

It was the USS Threadfin SS-410 (GIIA) that had the split cubicle with series/parallel battery capabilities. I served aboard her from 5/67 to 6/69 stationed out of Key West, FL. I was what was known as the "senior controller man" (sat the starboard side), my "junior controller man handled the port half. When we would switch from parallel to series batteries (quite seldom), all "sticks" would have to be thrown to off (neutral) while the battery line-up was switched over (and all this VERY rapidly). If we had an engineman trying to cool off by sitting in our forward hatchway, the resultant "fireball" (collapsing motor fields etc.) jumping between cubicle halves would scare him back into the engine room.

99% of the time we ran in parallel BUT for extreme high speed runs we would shift into series.

From Don Pruitt’s Trumpetfish webpage (SS-425) GII

Don was a radioman second class on the Trumpetfish when this incident occurred and his battle station was sonar plot.

Once we got to experience the difference between old technology, diesel electric and new technology, nuclear. We were a couple of hundred miles east of Charleston providing ASW services. We received radio traffic that USS Triton would transit our area within the next couple of days and we should try to simulate a torpedo run on her. At that time the Triton was the largest submarine built and was on its initial voyage to Holy Loch, Scotland.

The navigation officer computed the most likely course from Charleston to Holy Loch and we straddled that line and waited. The next day we picked up the Triton as she boogied along at a good rate of speed. We went to battle station torpedo where my station was sonar plot. We got a good screw count and an estimate of her speed. From the bearing rate we computed the CPA (closest point of approach). We had to make a small adjustment in position to get into optimum firing position.

While moving to the new firing point, the Triton must have heard us and lit off their active sonar. She was suspicious of the situation and was trying to get more information. We then noticed her bearing rate change indicating a turn to the left and an increase in screw count as she started an end run around us well out of torpedo range. Immediately our CPA was heading off the paper and we tried to salvage the situation as best we could to try for a desperation shot.

The CO ordered the batteries in series and made the half hour rate. At about 16 knots the Trumpetfish (GII) was shaking and rattling like my old 40 Ford doing 60 down a bumpy dirt road. After a few minutes of this we gave up the chase and surfaced to ventilate the boat because of hydrogen gas and seriously low batteries.

We later played back the tapes and computed what speed Triton had to be making in order complete her manoeuvre. I believe that the speed of nuclear submarines is still classified, but the answer we derived caused everyone to just sit and stare with their mouths open. Unbelievable!

In a message to Don, after a request for more information about Series Battery operation, he replied -

That was the only time that I knew that we ever went in series on the battery. The term used to describe placing the batteries in series was to make the "half hour rate" Meaning that we could completely deplete a fully charged battery in 30 minutes. We very seldom ever went to full speed when submerged. The screws would cavitate like crazy and we would stir up the water and make noise that would last for a few minutes after we were gone. The boat would vibrate a good bit and the skins on the superstructure would rattle and bang about like someone beating on a tin tub. Going fast was not the Trumpetfish's cup of tea.

Note - the USS Triton (SSN 586) was built as the only nuclear powered radar picket, she also was the only twin reactor submarine built for the USN. As one might expect considering her purpose, she was reported as being very fast on the surface.

Rick Nilsson - USS CUBERA SS 347 (Fig 1)

We had a total of 504 cells. Each battery was 252 thin-plate Exide cells weighing about 1000 lb. a piece, so that's about 125 tons per battery, plus cables. They had just been installed at Portsmouth in 1963 and there were some problems like reversed polarity on some of the cells. Those had to be jumper-bypassed, and the same number in the other battery too, to balance the voltages for parallel operation under flank speed ops. If a cell failed in one battery, we had to jumper one in the other also to always keep them balanced.

Guppys in our squadron (Submarine Squadron Six - Task Force Alfa) were used as targets for antisubmarine warfare training of surface craft officers and crews. There were times we had discharged our batteries almost completely on long ASW training dives, and had to run all four engines for hours to get them up and ready for the next day's operations. That's 4400 kilowatts running through the boat. The single air conditioning plant could barely handle the heat load in summer. Once we were near Bermuda in the Sargasso sea, and had to steam north 150 miles to find cooler water.

Most of our ASW training mission profiles were planned well in advance of leaving port, but surface and submarine commanders had the freedom to modify or invent them. The scenarios included operating modes that enabled aircraft and surface ship communications, electronics, sonar and radar operators and officers ample opportunity to experience them. We dove and turned, used slow turns ("silent running"), made fast course changes, cavitated, fired torpedoes and countermeasures canisters, changed depths and ran with various auxiliary machinery operating, like the air compressors. I can only imagine the havoc aboard the cruisers as officers and operators rotated so they all got time on the equipment during each run.

The fast discharge rates were used sparingly for several reasons - including saving wear and tear on the electrical systems, air conditioners, and crew, as well as extending fuel and the number of dives we could make in a day. I can remember making up to a dozen submerged runs a day as a target for destroyer sonar attack training, before we had to "timeout" for battery charging. Sometimes we'd snorkel to charge, so radar operators could analyze our mast signatures at varying distances. My 63-year old knees, hips and ankles are suffering now from the many "Lookouts below!" crash landings I made at the bottom of the Control Room ladder when clearing the bridge for diving. The drain grill in the floor there was "dished" by our impacts; one trip we had to pound it straight twice. That's a prideful statement, not a complaint.


Comment from Rik after reviewing a draft of the article

"1. It was generally known that roughly 70-80% of the speed gain of the Guppy conversion was a result of superstructure streamlining modifications such as removal of the guns, deck mounted SONAR domes, lifelines, and old-style radio antennae. Naval architects of the period suggested that the hull shape and wetted surface determined the fleet sub's maximum theoretical speed. The speed I show in my PDF drawing of 20 knots submerged is often the subject of some argument, but I witnessed Cubera at 22-23 knots once when we ran fast just to see what she could really do, and how noisy we could be. Indeed, it was difficult to control at that speed due to latency effects of the control planes, and cavitation was severe, making us very noisy. That was shortly after a Brooklyn Naval Yard overhaul which meant we had fresh battery cells, a clean hull and new screws.

2. I don't know if it is important, but the Germans commonly referred to their WWII submarine types in roman numerals; so the type 21 would cross-reference to German Type XXI.


(I decided to follow the Type 21 used in the pdf copy of original US interrogation report rather than mix it with the more usual Roman numerals.

I can offer no useful comment about this remarkable speed observed by Rik, that is not already implicit in the article.)

More interesting comment from Rik responding to a further review of the article.

As you mention in your article, operation at high speeds submerged was done rarely due to noise and the discharge rate bringing about the risk of having to surface under less than safe tactical situations.

Fleet snorkel, radar picket and Guppy boats were used extensively for coastal patrol during the Cold War escalation of tensions between the east and west. SS-347 patrolled Cuban waters and tracked Soviet subs. I stood sonar and radar ECM watches, recording the passing of Russian subs and stalking radar-bearing trawlers to analyze their emissions. I remember hearing a submerged Russki go roaring by like a freight train, oblivious to our presence.

I believe the primary results of the U.S. Guppy program were two-fold: experimentation with state-of-the-art affordable upgrades in support of coastal defense efforts, and to provide NATO forces with targets for ASW training using existing hardware while new technology and designs were under development and construction. There were undoubtedly political positives as well, such as using up appropriation funds that otherwise would have been diverted to non-military budgetary items, thereby ensuring a larger appropriation in subsequent periods.


A final anecdote from Dave Perkins, very experienced submariner, who served in the RN and RCN. Submarine author. Sadly no longer with us.

I think that most boats prior to the O/P classes and the Skate class nuclear attack boats were noisy for a lot of reasons. Casing rattles, propellers, hull cavitation etc, so yes, over about 7 kts was noisy. Since then they have become very quiet, even at speed.

When we (a 1970s Canadian O-boat) used speed to gain a favourable attacking position, and it wasn't an unusual thing to do, we did it well beyond easy acoustic detection range. Usually we located the "enemy" using long range sonar, confirmed their presence using ECM etc, plotted their course, extrapolated a favourable attacking zone then went deep and fast (10-12 kts) to where we wanted to be. Our O-boats were very quiet in their day and had a decent battery (German VARTA). Sometimes it didn't work, but more often it worked very well. The big snag was that it left you with a badly depleted battery after the attack so if there was a well directed counter attack you were in for it. I remember once we struggled on for two days before finally giving up, we had no power and no air to breathe either. Bad scene all round.

The Yanks loved "playing" with us because we frequently penetrated their AS screen to attack the primary asset. We were pretty good at getting away too. Let's face it, a super-carrier was worth an O-boat any day. However, we also learned that a screen of experienced AS assets (Can, USN or RN) was almost impossible to penetrate and often "fatal".

Stern shots became unnecessary once it was possible to set a torpedo to run along any course on the compass. This was possible (with some limitations) even with Mk 8**.

Stern torpedo tubes then became simply another tube from which to eject a weapon. From Mk 20 onwards gyro angling was connected by the umbilical straight to fire control so was integral to the launching solution. The big snag was to protect the firing submarine from a circular run and from becoming a valid target to your own torpedo. These problems were easily solved and from then on the attitude of the launcher became irrelevant.

Nevertheless, I've personally experienced a circular running Mk.8 on Scythian and was hit by one of our own Mk.20s on Alliance. I ran a torpedo performance analysis service at CANSUBRON ONE for a while and analysed some really weird runs with the Mk.37-Mod NC O/1 torpedoes which taught me that things could, and would, go awry.



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Appendix DAppendix F