Rn vs IJN

[MIflyer]

While the 7 astronauts lost don't compare to the hundreds estimated lost due to shitty Mk 14s, in terms of both money and institutional stupidity the loss was the equal of the torpedo imbroglio.

17 people killed by Shuttle.

In 1977 NASA knew that a Space Shuttle launch would cost $14 to conduct and would bring in at least $18M and as much as $36M from payload charges. And they had claimed they would launch up to 50 missions a year.

An outfit did a cost per launch estimate of the Shuttle missions, and it came out to $1.5 Billion a launch. And that almost had to be too low; they did not know where to look for all the costs. Income from payloads all but ended after the loss of the Challenger. The most number of launches they attained was 9, attained in only one year, most years it was a maximum of 8 and some years it was zero.

If the Torpedo Debacle had been handled the same as Shuttle, they would have had Goat Island keep right on making their defective torpedoes, even if they had competent firms make better ones. As it turned out, the USN decreased the RI Torpedo Factory workforce by the end of the war and sold the whole place off soon after the war.

 

[Thumpalumpacus]

17 people killed by Shuttle.

I was speaking only of the Challenger's crew, as that was the only mission I KNEW of when bureaucracy killed people in that program.

In 1977 NASA knew that a Space Shuttle launch would cost $14 to conduct and would bring in at least $18M and as much as $36M from payload charges. And they had claimed they would launch up to 50 missions a year.

An outfit did a cost per launch estimate of the Shuttle missions, and it came out to $1.5 Billion a launch. And that almost had to be too low; they did not know where to look for all the costs. Income from payloads all but ended after the loss of the Challenger. The most number of launches they attained was 9, attained in only one year, most years it was a maximum of 8 and some years it was zero.

If the Torpedo Debacle had been handled the same as Shuttle, they would have had Goat Island keep right on making their defective torpedoes, even if they had competent firms make better ones. As it turned out, the USN decreased the RI Torpedo Factory workforce by the end of the war and sold the whole place off soon after the war.

Yep.

 

[WARSPITER]

Interesting side note.

A Japanese investigation was held after the 1942 battles involving Type 93 torpedoes. It was found that around one third of
those launched had detonated after running to arming distance or while crossing a wake.

The cause was found to be that a sensitivity adjuster was fitted to the fuse on the type. Torpedo crews were physically
setting them to a lower setting to ensure they would detonate. With the higher factory setting they would have worked anyway.
As it was a large number were wasted.

 

[MIflyer]

With the early US torpedoes they found that the depth settings had been based on tests WITHOUT a warhead or even a simulated weight. The reason was that they had wanted to recover the test specimens to save money. So the torps ran deeper than they were supposed to.

After finally setting them at a depth to impact rather than go under the target they found that sometimes the torps did not detonate. The sub people in HI decided ta'hell with what they were being told and shot some with dummy warheads. The first thing they found was the depth problem. The second thing was that the firing pin was too flimsy, given that for some reason it had been designed to work through a 90 degree angle. The result was that a straight on perfect hit usually would not result in a detonation but an angled hit sometimes would. They wanted to replace the firing pins with stronger ones and the only material they access in HI was the propeller blades from the IJN aircraft shot down on 7 Dec 1941. The new firing pins machined from the tougher aluminum worked.

 

[Greg Boeser]

With the early US torpedoes they found that the depth settings had been based on tests WITHOUT a warhead or even a simulated weight. The reason was that they had wanted to recover the test specimens to save money. So the torps ran deeper than they were supposed to.

After finally setting them at a depth to impact rather than go under the target they found that sometimes the torps did not detonate. The sub people in HI decided ta'hell with what they were being told and shot some with dummy warheads. The first thing they found was the depth problem. The second thing was that the firing pin was too flimsy, given that for some reason it had been designed to work through a 90 degree angle. The result was that a straight on perfect hit usually would not result in a detonation but an angled hit sometimes would. They wanted to replace the firing pins with stronger ones and the only material they access in HI was the propeller blades from the IJN aircraft shot down on 7 Dec 1941. The new firing pins machined from the tougher aluminum worked.

Unauthorized work voided the warranty, of course.

 

[Shortround6]

I am not saying that the British torpedoes were flawless but they had over two years to sort problems out by Dec 1941.


Surface torpedoes
Wild_Bill_Kelso In another thread did the work of sorting through 13 Naval engagements in in 1942-43 involving the Japanese torpedoes.
They never got any hits at over 20,000yds and than one may have been iffy (or hit different target?) 17,000 yds may have been the longest on record?
By his count only 4 of these engagements were actually at "long range". He didn't define it (or I missed it) but we may be talking about 10-15,000yds.

The British torpedoes worked.
They were faster at the same ranges at the American torpedoes, not as fast as the Japanese.
British torpedoes would do 41kts to 11,000yds.
The Japanese torpedoes had heavier warheads.
Japanese ships carried more torpedoes.
British cruisers carried at least 6 torpedoes (except for some of the counties) but may destroyers had one bank taken out so a near useless AA gun (except for moral) could be fitted.

Aerial torpedoes.
Both sides had torpedoes that worked.
Warheads changed a bit but at the same time they were often within 10-15% of each other.
Speeds and ranges were also close even if not identical.

Submarine torpedoes.
Both sides worked.
Japanese had heavier warheads.
Japanese torpedoes were about 10% faster and started with longer range, as the war went on they swapped heavier warheads for shorter range. (6000yds)
Neither side really carried a large amount of torpedoes per sub although the Japanese often carried 18. The US carried 24 on most of the new boats, The German total of 22 on the type IX is part illusion, 10 of them were carried in under deck tubes that required a number of hours on the surface, in calm waters, to get through the loading hatches into the torpedo rooms.
A sub operating at periscope depth has very little visual range. Long range doesn't do a lot of good.

 

[RCAFson]

17 people killed by Shuttle.

In 1977 NASA knew that a Space Shuttle launch would cost $14 to conduct and would bring in at least $18M and as much as $36M from payload charges. And they had claimed they would launch up to 50 missions a year.

An outfit did a cost per launch estimate of the Shuttle missions, and it came out to $1.5 Billion a launch. And that almost had to be too low; they did not know where to look for all the costs. Income from payloads all but ended after the loss of the Challenger. The most number of launches they attained was 9, attained in only one year, most years it was a maximum of 8 and some years it was zero.

If the Torpedo Debacle had been handled the same as Shuttle, they would have had Goat Island keep right on making their defective torpedoes, even if they had competent firms make better ones. As it turned out, the USN decreased the RI Torpedo Factory workforce by the end of the war and sold the whole place off soon after the war.

It's not really fair to exclusively blame NASA for the shuttle disasters, as the design was basically reworked by Congress for political reasons. Similarly BuOrd had a lot of political interference/influence on weapon design and development due to the reporting structure of the USN's Bureaus.

 

[Wild_Bill_Kelso]

With the early US torpedoes they found that the depth settings had been based on tests WITHOUT a warhead or even a simulated weight. The reason was that they had wanted to recover the test specimens to save money. So the torps ran deeper than they were supposed to.

After finally setting them at a depth to impact rather than go under the target they found that sometimes the torps did not detonate. The sub people in HI decided ta'hell with what they were being told and shot some with dummy warheads. The first thing they found was the depth problem. The second thing was that the firing pin was too flimsy, given that for some reason it had been designed to work through a 90 degree angle. The result was that a straight on perfect hit usually would not result in a detonation but an angled hit sometimes would. They wanted to replace the firing pins with stronger ones and the only material they access in HI was the propeller blades from the IJN aircraft shot down on 7 Dec 1941. The new firing pins machined from the tougher aluminum worked.

Wow that is amazing!

 

[Wild_Bill_Kelso]

A lot of this true. However The Japanese carriers launched very few (any?) long range torpedo strikes, as in much over 200-240nm?
Swordfish book range was 452NM with torpedo, B5N2 range with Torpedo was 528NM? Range as a recon plane was 1075NM?
Swordfish actually had better defensive armament, as in crappy beats none out the front and bad beats truly crappy out the back. A Lewis gun in 1942 Japanese yype 92 was a Lewis gun.
British were putting Vickers K guns on Swordfish.

Granted the B5M2 cruised around 25-35kts faster than the Swordfish.

We are not really comparing the Swordfish to the Avenger here. And even with radar the TBF didn't have a working torpedo until well into 1943.

Again lets compare the actual performance of the B5N2 to the Swordfish.
The B5N2 was not 2 times faster over distance with a torpedo. It may have been 33% faster which is good advantage but not resulting in the Swordfish taking 2 to 3 times to conduct a strike. Talking 1942- early 43 here. The B6N didn't show up until mid 1943 and that was the version with the Mamoru engine which was not really suitable for operations.

The B5N suffered rather similar losses at the Battle of the Eastern Solomons. None the 1942 Japanese attack aircraft were very survivable in the face of decent (sufficient numbers) of fighters.
I would note that the TBD is sort of a red herring. They only built 129-130 of them (fewer than Skuas) and by Dec 1941 there were only about 100 left due to attrition. They had been out of production for over two years and there were never going to be any more. The replacement by the TBF was part of plan that had started in 1939.

This is an interesting comparison, but your comparisons are made on the basis of isolating specific elements. If you look at IJN vs. FAA, the disparity becomes much more stark.

The biggest hole in your argument is that the Swordfish was not just competing with the B5N, which I agree may only be about 20% - 30% better (that may be enough mind you, but it's really just the start). Lets compare from circa 1941-1943, just focusing on the range.

IJN
Fighters: A5M [range 750 miles], A6M2 [range 1,100 miles], then A6M3 [900, later 1,000 miles]
Seaplane Fighters: F1M* [460 miles], A6M2-N [range 700 miles]
Carrier Dive Bombers: D3A [900 miles]
Carrier Torpedo Bombers: B5N [600 miles], B6N (late 1943) [1,000 miles]
Carrier Scout: D3A, D4Y [900 miles]
Seaplane Scouts: E7*, E8* [550 miles] E13 [1,200 miles]
Flying Boats: H6K [2,900 miles], H8K [3,000 miles]
Land Based Torpedo Bombers: G3M [2,700 miles], G4M [1,700 miles]

FAA / RN
Fighters: Sea Gladiator* [430 miles], Fulmar [780 miles], Sea Hurricane [460 miles], (early) Seafire [500 miles]
Seaplane Fighters: None
Carrier Dive Bombers: Skua [760 miles], Swordfish* [520 miles], Albacore* [710 miles]
Carrier Torpedo Bombers: Swordfish*, Albacore*
Carrier Scout: Fulmar
Seaplane Scouts: Walrus* [range 600 miles], Sea Otter* [range 700 miles]
Flying Boats: Sunderland [1,780 miles]
Land Based Torpedo Bombers: Beaufort [1,600 miles], later Beaufighter / Torbeau [1,450 miles]

* = biplane

Range is estimated based on the maximum, operational range is less than half indicated for land based, about 1/3 for carrier. Range for bombers is given with a bomb load, for scouting they could go further.

Swordfish is the most capable strike plane for the British. It has the demonstrated ability to achieve hits and sink ships, and has the ability early on to carry radar and thus operate in bad weather and at night. But it must compete directly with not just the B5N, but also the very capable D3A which has almost twice the range.
D3A had a very good combat record and was outstanding at achieving hits and sinking ships, while better than you would assume at evading Allied fighters, due to it's considerable agility.
B5N is about 20 or 30% better than the Swordfish in a daylight strike, but also has a proven ability to sink ships.
IJN Recon assets (not just flying boats but also the E13 seaplane) have more than twice the range too. So the Japanese would probably detect the British first (on average, most of the time).
IJN fighters are not only an order of magnitude more effective in combat, they have twice the range. They can escort the Japanese strike planes and are markedly superior in combat to the FAA fighters, with the probable exception of the Seafire that arrives toward the end of this time frame. But even with the Seafire, the IJN could attack in daylight while remaining out of range.
IJN land based bombers have twice the range as British, and I would say with the exception of the Torbeau which came a bit later in the game, they were clearly more effective.

RN's only chance here would be to fight at night (the way IJN did in surface actions during the Pacific War vs the USN) and get pretty lucky. They are clearly at a severe disadvantage in the air war.

A bit like the Buffalo which engaged in two combats in US colors, the total record of the TBD was several raids on Japanese Islands that had no aircraft and the Battle of the Coral Sea and the Battle of Midway. Not a large number of battles to draw conclusions from. given the defective torpedoes and the crappy US tactics (not enough escort fighters for even TBFs) the TBD gets a lot of blame for things that were not it's fault. It was obsolete, there is no question.

I agree TBD wasn't used that much, I was just replying to other posts about it. Having looked into it earlier in the thread, I don't think it was better than the Swordfish, to the contrary. With viable torpedos it still probably would have been a fairly dangerous strike aircraft, but it had an enormous number of flaws.


By the way, I have to double check this but I believe the B5N had a higher dropping hight and drop-speed for torpedoes even early on in the war. This increased for all navies though with the adaption of the wood bits, so I have to review timelines.

 

[Wild_Bill_Kelso]

It's not really fair to exclusively blame NASA for the shuttle disasters, as the design was basically reworked by Congress for political reasons. Similarly BuOrd had a lot of political interference/influence on weapon design and development due to the reporting structure of the USN's Bureaus.

yeah it's the nexus of different political and corporate elements. Power + profit.

 

[MIflyer]

It's not really fair to exclusively blame NASA for the shuttle disasters, as the design was basically reworked by Congress for political reasons.

While at the Pentagon I was given the task of creating a "Sand Chart" so named because it looked like layers of sand, showing the funding for US Govt space launch capabilities from 1988 through 1999. This was a bit of a challenge, since it went past the current budget and thus had t be estimated. The chart showed that the Space Shuttle program, even years after the loss of the Challenger, still consumed the vast majority of US Govt space launch funding. Imagine what a similar chart would have looked like BEFORE we lost Challenger!

The USAF generals who had demanded the chart took one look at it and decided not to show it to anyone. They did not want to go after NASA, but just provide a DoD overall perspective.

The Shuttle Program consumed the vast majority of US Govt space launch funding from the early 1970's to well into the 21st Century. Admittedly, NASA was always quite P.Oed that they did not get ALL of the funding; I still hear claims that the Shuttle cost so much because we did not spend enough money on it. Heh.

 

[swampyankee]

It's not really fair to exclusively blame NASA for the shuttle disasters, as the design was basically reworked by Congress for political reasons. Similarly BuOrd had a lot of political interference/influence on weapon design and development due to the reporting structure of the USN's Bureaus.

MIT's OCW has a course on the design history of the STS, Aircraft Systems Engineering | Aeronautics and Astronautics | MIT OpenCourseWare

Let's just say there are a lot of groups that caused the Shuttle to turn out the way it did: DoD, Nixon, Congress, NASA, Thiokol ....

 

[Greg Boeser]

I still hear claims that the Shuttle cost so much because we did not spend enough money on it. Heh.

That's the mantra for every government program.

 

[Wild_Bill_Kelso]

I am not saying that the British torpedoes were flawless but they had over two years to sort problems out by Dec 1941.


Surface torpedoes
Wild_Bill_Kelso In another thread did the work of sorting through 13 Naval engagements in in 1942-43 involving the Japanese torpedoes.
They never got any hits at over 20,000yds and than one may have been iffy (or hit different target?) 17,000 yds may have been the longest on record?
By his count only 4 of these engagements were actually at "long range". He didn't define it (or I missed it) but we may be talking about 10-15,000yds.

The longest on record, allegedly, was Kula Gulf which was probably ~20km. But this list of naval engagements aren't the whole war, and we have to keep in mind, as good as type 93 torpedo was by WW2 standards, they are still unguided, and they got about a 2-3% hit ratio with them, largely by shooting into patterns. They sank ships by shooting lots of torpedoes. The Japanese were launching torpedoes at ranges up to 28km in the examples I posted. They may not have gotten hits at that range but that doesn't mean they couldn't. The odds were just a bit lower.

I'd say they were clearly getting hits in the 15-20km ranges, and they could fairly well count on that. Even in 1943, post Guadalcanal, the USN was underestimating the effective range of the type 93. Sometimes when they got hit at that range they assumed it was by a submarine (which was sometimes the case).

This is a long video but it is very well done. It includes air battles, land battles, and several naval engagements which demonstrate pretty well what I'm referring to. It's also interesting to see that the IJA was also making somewhat effective air strikes in some of these engagements.


View: https://www.youtube.com/watch?v=wdcntM5MDK8

There isn't any doubt in my mind the IJN would (at least in most cases) out-range the RN with their torpedoes, and we have also forgotten their major advantage in optics. The IJN seaplane scouts also used flares at night to assist in spotting in several engagements.

The British torpedoes worked.
They were faster at the same ranges at the American torpedoes, not as fast as the Japanese.
British torpedoes would do 41kts to 11,000yds.
The Japanese torpedoes had heavier warheads.
Japanese ships carried more torpedoes.
British cruisers carried at least 6 torpedoes (except for some of the counties) but may destroyers had one bank taken out so a near useless AA gun (except for moral) could be fitted.

You have a point in that the RN torpedoes worked, while the USN ones basically didn't until late 1943 at the earliest, and I agree that the RN would gain advantage from that in naval combat, but I IJN still has an advantage of 5-10km effective range, and maybe double that in maximum possible range. Plus the optics which I suspect will help more than radar in the early battles, as we know it took a while to get the hang of using radar in naval combat.

Aerial torpedoes.
Both sides had torpedoes that worked.
Warheads changed a bit but at the same time they were often within 10-15% of each other.
Speeds and ranges were also close even if not identical.

But the IJN air forces, as I've noted, will be much better and more deadly, with double the range and vastly superior daytime fighter cover.

Submarine torpedoes.
Both sides worked.
Japanese had heavier warheads.
Japanese torpedoes were about 10% faster and started with longer range, as the war went on they swapped heavier warheads for shorter range. (6000yds)
Neither side really carried a large amount of torpedoes per sub although the Japanese often carried 18. The US carried 24 on most of the new boats, The German total of 22 on the type IX is part illusion, 10 of them were carried in under deck tubes that required a number of hours on the surface, in calm waters, to get through the loading hatches into the torpedo rooms.
A sub operating at periscope depth has very little visual range. Long range doesn't do a lot of good.

I'll concede RN probably has an overall advantage in both submarine and ASW warfare. But I don't think that is necessarily enough to account for all the other IJN advantages. But maybe, who knows.

 

[Shortround6]

There isn't any doubt in my mind the IJN would (at least in most cases) out-range the RN with their torpedoes, and we have also forgotten their major advantage in optics. The IJN seaplane scouts also used flares at night to assist in spotting in several engagements.

You have a point in that the RN torpedoes worked, while the USN ones basically didn't until late 1943 at the earliest, and I agree that the RN would gain advantage from that in naval combat, but I IJN still has an advantage of 5-10km effective range, and maybe double that in maximum possible range. Plus the optics which I suspect will help more than radar in the early battles, as we know it took a while to get the hang of using radar in naval combat.

The effective range have have been 5-8km longer but the max range was very dubious advantage. And compared to the US, the British advantage is there but harder to figure out. The British torpedoes had a high speed setting that was 4kts slower than the Americans but was 5000yds further. Or it offered same range as the US medium speed but was about 6kts faster.
You are betting an awful lot on Japanese optics, which didn't work so well at times. Like at the Battle of Cape Esperance where the Japanese got within 5000yds or closer to the US forces without spotting them. yes, due to lack of practice/experience the US did not take full advantage of this advantage, more because of poor communications to and from the US Flagship than actual faults in the Radar. The Force commander had used the San Francisco instead of one of the light Cruisers which had radar one generation newer. The Helena had tracked the Japanese from 30,000yds out with the newer radar.
Expecting the British to make either the same mistakes or not have radar as good or better than the US is stretching things.
In fact at the first Battle of Salvo the Hobart which was in the eastern blocking force and totally out of the battle, was able to track most of the participants on radar from the other side of the transport groups.
Radar was not a cure all, it was far from fool proof although in some of these cases it was the fools operating/interpreting it. The British had a lot more practice in trusting the radar or at least investigating things instead of blowing off reports.
Some rain squalls could block/degrade radar and ships in close proximity to land were often masked, often not on purpose.

At least the British could use radar to get the look-outs at least looking the right direction even if they didn't have the ability to blind fire.

But the IJN air forces, as I've noted, will be much better and more deadly, with double the range and vastly superior daytime fighter cover.

The range advantage is there but the double the range is dubious.

I'll concede RN probably has an overall advantage in both submarine and ASW warfare. But I don't think that is necessarily enough to account for all the other IJN advantages. But maybe, who knows.

British are not going to win a major carrier vs carrier fleet battle. Even if they had enough planes to fill all the hangers, they don't have enough hanger space. And that assumes the planes were equal, which they were not. However the Japanese are not good enough to deal with larger than historical amounts of land aircraft either.

 

[Shortround6]

Historically the Dutch were responsible for the the Non US submarine effort and this helps show what some of the problems were.

Both sides (Japanese and Allied) seem to have been somewhat contemptuous of the other. The Allies (don't know about the Dutch but they were trying to gear up, just a bit late) had a poor opinion of the Japanese and Churchill seemed to think he could bluff them with one Battleship and one old battlecruiser and not much else. Americans were trying to send a couple of hundred airplanes (not all made it) and train the native troops (too late). Japanese sent dribs and drabs of troops all over the place got very, very lucky hitting poorly prepared, equipped areas.

The British had two subs in the entire theater (Austrian?), The Dutch got their subs to sea and 7 of the 15 in area were stationed in the South China sea under British control, 3 were off Borneo under Dutch control, the K-XVIII was at Surabaya undergoing refit. The K-VIII, K-IX, and K-X were being re-commissioned as was the K-VII. They never got the K-VII operational.
The 7 boats under British command reverted back to Dutch command in Jan 1942.
The K-VII through K-X were 1920-23 boats of under 521 tons, 17.7in torpedo tubes (some only 4) and top speeds of 13-15kts (when new). They also had a diving depth of 40 meters.
The K-XI, K-XII, K-XIII were 611 ton boats, 1924-25, 15kts and had two 21 tubes, with 4 torpedoes, and 4 17.7 tubes with 8 torpedoes. dive depth 60 meters.
All of these boats were good for about 3500 miles at 12kts, Please note that it is about 1300 miles from Surabaya to the North tip of Borneo so long patrols were not going to happen.

That left 8 boats from 1932-33 on. of 771 tons (5 boats) 896 tons (1 boat) and 998 tons (2 boats), diving depth 81 meters or better. Eight 21 tubes with 14 torpedoes.

These are the boats that sunk/damaged 10-12 Japanese ships in Dec and other 2-3 in Jan-March during the retreats.

If the US had done 1/2 as well they should have sunk 15 or more ships instead 6.
If the British had 15 subs at Singapore, letting the Dutch deploy to the east of Borneo, total Japanese losses could have been much higher in the first few weeks of the war.

 

[EwenS]

On 7 Dec 1941 Britain had no submarines east of Suez. 2 T class were despatched from Alexandria on 26 Dec 1941 & 4 Jan 1942. Trusty arrived at Singapore on 20 Jan 1942 and carried out patrols in the Gulf of Siam and the DEI. Truant arrived at Batavia on 8 Feb 1942. The RAN had no submarines in 1941.

All the pre-war subs based at Singapore & Hong Kong and their supporting depot ship, Medway, had been withdrawn by mid-1940.

 

[Shortround6]

I will note the disproportionate amount of damage the US "S" boats caused compared to the later boats and the Fleet boats, early in the war.
These used the old Mark 10 torpedoes of 1918. These were about 4ft shorter than the later Mark 14s.
By the mod 3 version they held about 497lbs of TNT and were good for 3500yds at 36 kts.

the story of the S-44 makes for interesting reading.
USS S-44 - Wikipedia

She sank 3 ships in her first 3 war patrols including the Kako returning from Salvo Island.
However the problems of operating submarines, especially old ones, are all too apparent.
The "S" boats with their old but mostly functional torpedoes in 1942 may have partially hidden how bad the Mark 14s really were.
17 S boats claimed 42 ships sunk with most of them in 1942.
There were 37 S boats out of the 112 US boats in service in Dec 1941, there were 27 older boats. Those were not used in the Pacific, most were used for training although a handful were loaned to the British and small group were used for anti-U boat work.

I think we are entitled to think about what 15-20 British subs with working torpedoes could do to Japanese invasion convoys. Not outright elimination but enough losses to slow down the ground advances. That and several divisions of well supplied, experienced troops and about 3 times the number of historical aircraft might turn the SE Asia campaign into slow motion attack that gives the British more time to reinforce and turn things into a battle of attrition.

 

[EwenS]

R3, R17, R19, S1, S21, S22, S24, S25 and S29 were transferred to the RN in late 1941/42. 2 were accidentally sunk in May/June 1942 and rest returned to USN control from mid-1944. Most of their time in RN hands was spent in training roles.

In Sept 1939 there were 14 O,P,R class subs (some refitting) in 4th Sub flotilla based at Singapore and Hong Kong along with 2 Porpoise class minelayers (with another en route which reversed course to return to Britain). 4 O class were sent to Colombo in Oct 1939 to form the 8th Sub flotilla.

 

[Shortround6]

in 1939 there were 4 of the "O" boats in Singapore.

1927-29, 1784 tons, 17.5 kts, 5,000-7,000 miles (depending on speed) 6 bow/2 stern tubes/16 torpedoes. 230-300ft?

6 P class and 4 R class were pretty much repeats of the O with minor changes. These boats were not satisfactory in some regards.

The Porpoise class were minelayers of similar size but almost 2kts slower and the stern tubes replaced by an under deck mine mine rail.

They could carry 50 standard RN mines. In 1940-41 the RN developed mines that could be laid using the torpedo tubes although this was not often done.
there were 6 of this class and it is doubtful than they would have been left in Singapore if there was not actual combat going on as their minelaying ability and cargo capacity was useful other places.

A number of these boats were sunk in Med in 1940-41 and if The British had decided to reinforce Singapore in 1941 6-8 of the S and T classes would be needed to bring the numbers back up with survivors of the O,P,R classes.