Book Research

[TorpX]

I am reading Spadefish , by Stephen L. Moore, and ran across some interesting bits of information in the chapter I just finished, and had to share.

#1 - TDC operation

The soundman would give a turn count on a target ship and this was somehow input into the TDC to obtain the speed:

p158

Then the gunnery officer, Lieutenant Laundy, would put this count right into the TDC and it would figure the speed of the enemy.

#2 - "decks awash"

We had an interesting discussion about this recently.

p159

Underwood ordered his boat flooded down to reduce her topside radar profile. Her decks were awash with just the bridge structure exposed.

[Enemy radar was a concern. The had the APR radar detector and could tell when they were being looked at.]



#3 - maximum speed

There was discussion about this too, awhile back, concerning Barb's max. speed and no real consensus as to how this was achieved. I don't recall the speed claimed for Barb, but Spadefish got itself into a very tense situation with multiple escorts chasing her on the surface in fairly shallow water.

p171

At maximum power, as the electricians put it ... attaining a shaft speed of 305 turns on a 1400 KW load from the motors for a pit log speed of 22.8 knots- the fastest that Spadefish was ever to be driven while fully loaded!

Anyway, I considered these to be very interesting details. If I find more in the rest of the book, I'll post them.

[merc4ulfate]

They are saying they got 22.8 knots out of the electrics not diesels? That is 26.2 mph. Or are they saying the diesels were driving the electric genterators and the boat as a whole was generating an electric load of 1400KW?

Clarify please?

By the way why does Commander Fluckey get a Medal of Honor for harbour raiding and we get critized for it.

I mean Truk and all you know??

[Sailor Steve]

Originally Posted by TorpX

The soundman would give a turn count on a target ship and this was somehow input into the TDC to obtain the speed:

That is indeed interesting. I would love to see how that worked.

#2 - "decks awash"
We had an interesting discussion about this recently.

Yes we did. I've heard accounts of attacking "decks awash", and it's my belief that it was used, and frequently. My only objection to it in the game is that the game allows you to run all over the ocean in that condition with no fuel use penalty, which must have been severe in real life.

#3 - maximum speed
There was discussion about this too, awhile back, concerning Barb's max. speed and no real consensus as to how this was achieved. I don't recall the speed claimed for Barb, but Spadefish got itself into a very tense situation with multiple escorts chasing her on the surface in fairly shallow water.

I remember that discussion. I was unable to figure out how the extra impetus from the motors could give enough horsepower to reach that speed, but Richard O'Kane said they did it so I was forced to accept the reference to someone who would certainly know.

Originally Posted by merc4ulfate

They are saying they got 22.8 knots out of the electrics not diesels? That is 26.2 mph. Or are they saying the diesels were driving the electric genterators and the boat as a whole was generating an electric load of 1400KW?

Clarify please?

Normally the Diesels drive the generators, which then drive the electric motors which drive the props. One or more generator can be used instead to charge the batteries. Submerged the batteries drive the motors, but you knew all that. What they are talking about is using the batteries while surfaced to give extra impetus to the motors, so both the diesels and the batteries are supplying power to the generators at the same time. While I accept it I still have a hard time understanding just how that much extra speed could be obtained.

But then I don't know anything. Seriously, I don't. That wasn't sarcasm.

By the way why does Commander Fluckey get a Medal of Honor for harbour raiding and we get critized for it.

I mean Truk and all you know??

Cmdr Fluckey attacked two convoys anchored off the China coast. Other commanders raided merchant ships at anchor in harbors. We criticize the concept that we get ordered to raid major naval bases like Yokosuka and Hiroshima, which never happened. The only attack on Truk I'm aware of was Operation Hailstone, which was a major air strike, with submarines and surface ships lying in wait out in deep water for escaping Japanese ships.

[TorpX]

Originally Posted by merc4ulfate

They are saying they got 22.8 knots out of the electrics not diesels? That is 26.2 mph. Or are they saying the diesels were driving the electric genterators and the boat as a whole was generating an electric load of 1400KW?

Clarify please?

It is just as SS said. The diesels were going full tilt to supply current to the electric motors.

It is also stated that the governors on the engines were disconnected. I didn't quote all the comments about this part, but just enough to give you the bottom line. The book has statements by the author, and statements that are direct quotes from the crew. There was obviously anxiety about whether the engines/motors would hold up, but it was a dire emergency, so they did what they had to do.




About the TDC:

That is indeed interesting. I would love to see how that worked.

Unfortunately, he didn't provide any more detail. I assume that they had to know what type of ship or class of ship and selected from a number of count-speed curves. Otherwise, I don't see how it would work.

He also didn't say what model of TDC they had. I know they had different models, but don't really know about the details. I know there was a "table top" model which had to be installed in the control room, and it was only the successors which could fit in the conning tower. I imagine there were other improvements as well.

I remember that discussion. I was unable to figure out how the extra impetus from the motors could give enough horsepower to reach that speed, but Richard O'Kane said they did it so I was forced to accept the reference to someone who would certainly know.

Yes, I can see why you found it hard to believe. It is hard to see how the diesels could produce 40 or 50% more power, just like that.

IMO, the only plausible explanation is that the "official" maximum speed was based on the boat running with four diesels on propulsion, period. The Barb and Spadefish, were running with four diesels (at higher RPM's) plus the battery, to provide the power. The Navy probably never contemplated this mode of operation, and, after all, it is not a sustainable speed. Even were there no danger of engine/motor failure, the battery would soon run down and the speed would decrease.

[merc4ulfate]

Removing the governors would have sure helped a great deal in getting more power. The governor on any engine simply keeps its RPM at a safer level so the engine itself does not over heat or destroy itself.

I could certainly see how removing the governors and adding the battery could increase to those speeds.

There is safe operating procedures then there are "I'M GIVING YOU ALL SHE'S GOT CAPTAIN"

When you have a high pucker factor ... you find the impossible very possible.

[Ghost Dog]

Its really not that surprising. Most internet sources available list the Balao Class top speed at 20.25 kts. So to manage 22.8, doesnt seem far-fetched at all. Official sources for those kind of things are always below the actual speeds anyways.

real-world first-hand example: My father captains ferries in and around British Columbia, Canada. In the Straights of Juan de Fuca, his GPS speed was 18 kts. (he was flat out), and he plotted the speed of a USN Arleigh Burke (Flight IIa) going past him (using his radar, plus GPS) at exactly 34.6 kts. The official listed speed of the Burke Class Flight IIa is "Greater than 30 kts", with other sources saying between 30 - 32 kts.

That DDG blew our doors off!

[Sailor Steve]

Originally Posted by Ghost Dog

So to manage 22.8, doesnt seem far-fetched at all.

It does to me, but with qualifications. The difficulty I've always encountered is that speed/horsepower calculations are never a straight line. The example I like to use is a car which can make 100 mph on 100 horsepower. The law of diminishing returns comes says that doubling the power will give half the return. If you double the horsepower to 200, the car will not go 200 mph. The drag will increase exponentially and the car will peak at around 150 mph. Double it again to 400 and your top speed will be around 175 mph. Double it again to 800 and you'll end up with 187.5 mph. Of course you can play with the gearing and trade acceleration and top speed, but not by a whole lot.

Back to ships. The power needed to overcome hydrodynamic drag increases as the cube of the speed. By the time you reach the indicated top speed you would have to double the available horsepower just to get that extra two knots, and that is simply not possible.

HOWEVER...

Official sources for those kind of things are always below the actual speeds anyways.

That's the qualification, and that could well be the answer I was missing before. "22.8 knots" might well have been closer to the actual top speed of the boat, and "20.25 knots" could have been the "do not exceed" safe speed. If that's the case then hydrodynamic calculations would have to be made from a basis of a 23-knot top speed, not 20 or 21.

And that, as you said, no longer seems far-fetched to me.

[Snarf]

I just read Thunder Below! By Eugene Fluckey(in 3 days I might add)
The Barb hit a speed of 23.5 knots while raiding Namkwan harbor. They achieved this by tying down all 4 diesels' governors and running at 150% I believe. Not good on the engines from a longevity standpoint, but doable.

It seemed that they had intermittent problems with the Mk 18's on the Barb too, a few erratic runs, I think one circular run, some deep runners. they also tried out Mk 28 homing torpedoes, they fired them too shallow and the torpedoes dove into their own noise bouncing off the sea floor. They did have a successful sinking with the Mk 27 'cutie' though.

I VERY highly recommend reading Thunder Below! though it is unbelievably fascinating. "Lucky" Fluckey is a great author and an epic skipper.

[TorpX]

Originally Posted by Snarf

I just read Thunder Below! By Eugene Fluckey(in 3 days I might add)

Yes, it is another very good book. It's been awhile, so I have forgotten a lot of the details.

they also tried out Mk 28 homing torpedoes, they fired them too shallow and the torpedoes dove into their own noise bouncing off the sea floor.

Did Fluckey actually say that, or is that you interpretation of what happened?

[Snarf]

Pg. 408

'Later I was informed that the Mark 28 torpedoes had not been tested in shallow water. Tests showed that ships propellers emitted both a direct sound path and a strong sound path that reflected or bounced off the bottom at lesser depths. Thus, those that we fired headed for the bottom to bury themselves in the mud or sand, or they failed to start.'

[TorpX]

Quoted by snarf:

'Later I was informed that the Mark 28 torpedoes had not been tested in shallow water. Tests showed that ships propellers emitted both a direct sound path and a strong sound path that reflected or bounced off the bottom at lesser depths. Thus, those that we fired headed for the bottom to bury themselves in the mud or sand, or they failed to start.'

Ok, I guess I had forgotten that, or assumed that they failed to start (like with trying to start your car when it is -30 F ??). In any case, that is a significant design problem as you have the potential for your torpedo exploding underneath your sub in shallow water - not good!

Sorry. I didn't mean to sound condescending. The truth is that I haven't read all that much about torpedoes myself, and sometimes when I come across something that seems obvious to me I tend to forget that it may or may not even be true, much less "obvious" to someone who may know more than I do.

It's ok. I probably annoy twice as many people as you do.



About the electric torps, I'm struck by the notion that the navy had the same pattern repeating. Defective torpedo design - inadequate testing - poor results in the field - redesign work. This book just seems to confirm it. The Germans had the same problem, but handled it much better. BuOrd let the Navy down, I'd say.

[Snarf]

I've just finished reading Wahoo and Clear the Bridge! also. An interesting tidbit with the screw count for knowing the enemy's speed. On Tang, they ended up bringing aboard a metronome. The sound man would match the metronome to the ships screws, and he could instantly tell if the ship was speeding up or slowing down before you would ever be able to tell by ear.

O'Kane had a bit of frustration with the Mk 18 torpedoes too (a bit of an understatement since one sunk Tang). Before the war torpedoes were made at one place and they were handcrafted, even though they had exploder and depth keeping problems, the rest of the torpedo functioned quite well. During the war, they had many contractors who bid bottom dollar to make the Mk 18's so the build quality really left a lot to be desired. O'Kane talks about this in Clear the Bridge!, after their problems getting hits with the Mk 18's he had his torpedomen take apart and test everything and fine tune the torpedos, and then he started getting hits with them. His last patrol, the whole lot were Mk 18's taken aboard from Tambor (as they were experiencing shortages at the time). Once again he had his men make sure the torpedoes were functioning in top shape, and they scored hits with nearly all of their torpedoes, save the last fateful circular run.

Regarding speed again, O'Kane said they were doing 22 knots when they were picking up downed aviators off Truk. I wonder now on the performance difference between the F-M and the GM Vinton engines, as Tang had F-M engines and Barb had GM Vinton's. From what I've read, Barb seems to have the speed record.

Another interesting thing, O'Kane mentioned using the turbos (the air compressors for the ballast tanks) to blow air out the bottom of the ballast tanks to keep the sub as high out of the water as possible with the added effect of creating a layer of air bubbles under the sub which reduced drag, and it made a difference of a knot or two.

[Sniper297]

One common misunderstanding is the difference between U-boats and US fleet subs. The U-boats all had direct drive - a clutch on the back of each diesel connected directly to the propeller shaft. The rotor for the motor/generator was wrapped around the propeller shaft, and was used as either a motor powered by batteries or a generator to charge the batteries.

A US fleet boat had no connection to the propellers at all - each engine was connected to a big generator, and nothing else. The traction motors propelled the sub both on the surface and underwater, there was no other means for turning the shafts.

If you think about the difference between reciprocating engines (especially diesels) and electric motors, the reciprocating engine has a lot of back and forth up and down movement of pistons and valves - over rev a piston engine enough and it will shake itself apart and/or explode before it overheats.

An electric motor is very simple in comparison and has only one moving part, the rotor. Traction motors back then normally used between 500 and 750 volts volts DC, but if you had a way to feed 3000 volts into one you could wind it up like a berserk alarm clock for quite a long time before the insulation would start to melt. Obviously you would need to short around the fuses and clamp down the contactors, but a traction motor would spin happily at 10,000 rpm for an hour or two if there was a way to feed enough power into it. You'd need to overhaul it after that type of abuse, but it would be unlikely to fail.

The real limitation would have been how much power the diesel generators could pump out, and of course the increased drag of the hull moving through the water. The trick with using the low pressure blower and leaving the Kingston valves open to make a stream of bubbles under the hull sounds viable, dunno how much it would decrease drag but it would decrease it.