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.

[TorpX]

I'm on Spadefish's third patrol. They spent the winter of '44-'45 in the Yellow sea. Ice accumulation was a significant problem, slowing their dive times. The only solution was to periodically submerge to melt it off. Interesting, I didn't know the Yellow Sea area got that cold.

Also, they didn't have too much confidence in the Mk. 18 electric torpedo. Capt. Underwood passed on a 2,000 yd. shot because they considered the torpedo would slow in the cold water.

[merc4ulfate]

Average January temperatures are −10 °C (14 °F) in the north and 3 °C (37 °F) in the south Yellow Sea area. The water temperature is close to freezing in the northern part in winter, so drift ice patches and continuous ice fields form and hinder navigation between November and March.

http://en.wikipedia.org/wiki/Yellow_Sea



Batteries are less efficient in the cold. All batteries deliver their power via a chemical reaction inside the battery that releases electrons. When the temperature drops, the chemical reactions happen more slowly and the battery cannot produce the same current that it can at room temperature. A change of ten degrees can sap 50 percent of a battery's output. In some situations, the chemical reactions will happen so slowly and give so little power that the battery will appear to be dead when, in fact, if it is warmed up, it will go right back to normal output.

[Snarf]

I know that the Navy's listed speeds are not what the vessel can really do. Take for example the T-AKE ships, they are listed at 20 knots max speed. I was on one while being followed by pirates (the kind who carry arrrrRPG's), they poured the coals to it to outrun it (ROE for supply ships dictates evading at all costs and engaging only as a last resort). Anyway, I took a peek at the speed in the helicopter control tower and we were making 24+ knots. I know it's not a submarine but the propulsion is very similar, 4 (HUGE) diesels turning generators which in turn supply power to an electric motor turning the screw. It seems that it would be very likely that a fleet boat could make similar speeds, especially since it is a fraction of the weight of a T-AKE supply ship.

[TorpX]

Originally Posted by merc4ulfate

Batteries are less efficient in the cold. ...

Yes, I understand the chemistry well enough. However, this was late in the war, and I was under the impression that pre-heating the batteries and insulation, had more or less eliminated the problem. If that was not the case, why issue the Mk. 18? They knew where they were going, and as you pointed out, cold temps. there were not exceptional.

It makes me wonder if the Mk. 18's were used by choice, or if they were forced upon the crews. A torpedo that can't reliably make a 2,000 yd. run, isn't much of a torpedo.

[Sailor Steve]

Google is your friend.
http://en.wikipedia.org/wiki/Mark_18_torpedo

The Mk 18 was based on the German G7e. They wanted a wakeless electric torpedo. They accepted that there would be problems, but the wakeless torpedo was needed. Apparently it was popular because the potential problems were unknown and the benefits were believed at the time to outweigh any negatives.
http://www.hnsa.org/doc/torpedomk18/index.htm

[TorpX]

Ok, I don't know why people are assuming my comments about the Mk. 18 are based on ignorance, and that I've never read anything about torpedoes before. I'll just state that that is not the case.

They wanted a wakeless electric torpedo. They accepted that there would be problems, but the wakeless torpedo was needed.

I'm not sure who wanted the wakeless torpedo. Certainly, many liked the idea, but it is not clear to me that there was any pre-existing yearning, much less need, for such. The problems written about, seemed to come as a rude surprise, and I question whether either the Navy or it's skippers, would have accepted the electric torpedo, if they had known of the disadvantages that came with it.

I think most of the impetus for the Mk. 18 came from the extraordinary frustration with the Mk. 14, and perhaps, a certain amount of German-envy. (I'm talking about the common, prejudiced idea that any German weapon/technology was superior to the Allied counterpart.) If you have been stuck depending on a defective tool (whatever the reasons), you would naturally be looking around for something else to try.

Of course, that is just my opinion. I'm sure others will disagree.

[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?