No TDC on Suger Boats

[don1reed]

Just sank a 19k ton escorted Euro Liner NW of PI. As we know, Sugar boats didn't have a TDC so I used the horizontal reticules on the objective lens of the scope.

In high power, each small mark = 15' MOA; each large mark = 1°.Top to bottom and side to side, lens face = 8°.
In Low power, each small mark = 1°; each large mark = 4°. Top to bottom and side to side, lens face = 32°.

Acquired first range and bearing, down scope...made plot, 3 min. later, acquired second range and bearing, down scope...made plot. Dist. travelled converted to 13 kn.

Computed OAC via ASIN (( 13 tgt speed / 31 torp speed ) x SIN 80 aob ) = 24°. Therefore, I fired a spread of 4 at the liner as she passed in front of 336° travelling left to right. All hit and she sank within 1 min. leaving 4 liferafts (RB-15's) braving the sea.

edit: btw, I might add that the escorts paid little attention to the proximity of the liferafts as they attempted to do me in. Interesting.

[PeriscopeDepth]

Most are not as hardcore and skilled as yourself, though to get firing solutions without a TDC. Good job!

PD

[RickC Sniper]

WTG Don,

:up:

[don1reed]

Hey, hey...its the, Frank Kulick, method from SH1:D .

[Jungman]

That works well, nice information. But in WWII they did not have a calculator to compute those fun conversions, arcsin, sin, even divide? I thought that is what they use the TDC for (as a calculator).

Though I do admit, I also make the same manual calculation without the TDC...except I stick into the TDC just for fun.

I think they would have had to use that nomograph, wizwheels and stuff (no TDC ). How did they do it without the power of a modern calculator, or a TDC? BTY what is a Sugar boat? the S-class?

[nattydread]

I assume they had spread-sheets for the trig computations. I have one. They also had a another guy or two doing the computations and map plotting other then the guy looking through the scope to make it efficient time wise considering they couldnt pause real life:D

[WFGood]

Absolutely, there would be someone to make the calculations while the captain made the observations. Slide rules and charts would have to suffice to make the calculations. I have a copy of the Submarine Torpedo Fire Control Manual, circa 1950, and it does have quite a few "plates" in the back which contain angles, slopes, etc. It also provides things such as "lead angle for target beyond critical range" and SINa = target speed/torpedo speed. I haven't had a chance to read through it entirely, but I have a lot of respect for someone who can do that and hit a target. BZ!

[John Channing]

I believe they had a circular slide rule called an "Is/Was" or "Banjo".

JCC

[Jungman]

Thanks for the info. You know, it maybe cool to try to reproduce those tables and banjo thingy to do it the old fasion way, no modern calculator. :cool:

One other question, in SH3 someone did have a way to determine speed by listing to the number of revolution of the screws via hydrophone. It was bit hard to use depending on what ship you were listening too. iRL you did not know this ship's ID.

If the hydrophone does not work at PD, you can still get range via an active sonar ping to the target. I am surprised that a warship's passive sonar guy did not hear that. Is that realistic> pinging the target to get range via active sonar at PD? without spooking the warship.

Modern ships/subs would hear that immediately. I guess in the old days, it was hard to hear that one or two pings unless they got real lucky.

[WFGood]

I have the files. They may not reproduce very well, but I can try and post it to my personal webpage and let people look at it and take what they will.

[Sailor Steve]

Aw, man, I read the title and thought "Really? They don't have them in the game? COOL!"

It isn't even April first anymore; it wasn't even a joke...but it got me anyway!:damn: :rotfl:

[Jungman]

I have the files. They may not reproduce very well, but I can try and post it to my personal webpage and let people look at it and take what they will.

Sure. It would be neat for a reference, a real life mod sort of.

It would be nice to reproduce what they really used, if it can be used in game. As the one poster said, they use to count screws to get speed. We cannot do that in game, reliabley.

The equation above, for a specific torpedo type (let say Mark 14 slow at 31 knots) could have a circle wheel were one turns it to the calculated target speed, to match up the calculated AOB, then read off toward the center the given degree offset you would need to fire from your present given target bearing you are observing. OP method.

This does not need the range...it is taken into account when determining the speed/plot method, which I like to do.

[MadMike]

I believe "War in the Boats" by Ruhe mentions using the "banjo" (S-class). Will check in the local library tomorrow...

Yours, Mike

[don1reed]

Doubting Thomas' :D

I posted this in June 2006 on the SHIII forum:

http://www.subsim.com/radioroom/showthread.php?t=94608


Yes, those WWII sub/uboat skippers (all nationalities, btw) were smarter than we give them credit for. Some of those guys became scientists, architects, & engineers after the war, I'm told :)

...and would you believe, the entire USA Lunar project of placing men on the moon (1969) was completed before the era of pocket calculators...hmmmm.

...someone must have been using a sliderule.:|\\

Cheers,

[don1reed]

Here is how the Arcsin (( 13/31 ) sin 80° ) is completed using a dimestore sliderule.

http://img58.imageshack.us/img58/9359/picket1jz0.th.jpg (http://img58.imageshack.us/my.php?image=picket1jz0.jpg)
http://img64.imageshack.us/img64/8248/picket2ev6.th.jpg (http://img64.imageshack.us/my.php?image=picket2ev6.jpg)
http://img64.imageshack.us/img64/7688/picket3xe1.th.jpg (http://img64.imageshack.us/my.php?image=picket3xe1.jpg)

[Charos]

Thanks for the headsup on the fact that S-Class didnt REALLY have a TDC - Being somewhat ignorant of US WW2 Submarines, I didnt know this fact. :oops:

Being a fan of Type II and type XXIII German U-boats I love the smaller more "Clunky" variety - it makes things all the more rewarding.
especially now I know I dont have a TDC I love the S-Class even more.

Other than the stadiometer I do everything manual anyways so Im looking forward to getting rid of that as well.

Im off to start a fresh S-Class 100% Full difficulty Campaign - we should start the 100% NO TDC WW1 Sub club. :arrgh!:

In anycase I found a great link for anybody wanting to tread these dangerous waters the old fashioned way,.

http://www.valoratsea.com/notdc.htm


Im still trying to figure out why my SIMULATED S-Class has a TDC though. :huh:

[DeePsix501]

From what I gather/have read, the earliest boats to get the TDCs we see and use in the game (TDC Mk III) was first installed in the USS Tambor and all later subs till the MKIV came out which was adapted for the new torpedoes and the use of SJ radar. In the book i'm reading "Take Her Deep" Galantin described the USS Sculpin, a Sargo class sub as having an older, bulky, table top TDC in her control room.

Very brave of you to not use the TDC and input all of it by hand. Huzzah for Trigonometry! :know:

[Jungman]

:p Good info and links! I like to make a chart ruler just for those torps I will use. Since we know if using the Mark 14 at slow is 31 knots, A simple look up, just as a back up reference. From that other link

Any submarine during the war that had its TDC go down from damage, or technical problems, would have to resort to this method, as it’s primary solution. Believe it or not, it is still in use today as a backup to all that multimillion-dollar fire control system!

Yep, one Electromagnetic Pulse Blast (EMP) from a nuclear detenation, we will all be pulling out our old slide rules, once all the electronics are fried. :dead:

It would be neat to have the TDC be able to get damaged also in game, so you would have to use the old fasion method. I guess you could roll a dice for whatever damage and role play it that way, if took you serious damage from a DC, and are brave.

[jmr]

Doubting Thomas' :D

I posted this in June 2006 on the SHIII forum:

http://www.subsim.com/radioroom/showthread.php?t=94608



don1reed, are you whiz wheel files still available for download? Unfortunately the download links in that thread you listed are dead.

Thanks!

[don1reed]

jmr, send me your email via pm

[Torpex752]

No TDC is really rewarding, and now with the tools they have in SH4 its even better. I use to use a board with a blank sheet of paper to do some of the tracking! LOL

Frank
:cool:

[Charos]

OK I have just completed some testing as I thought something was amiss with the TBT and Attack periscope Graticules (Observation scope is probably affected as well but I didnt test.

Can someone else verify my tests.?

I made a simple mission with my S class perpendicular to a Kongo Battleship and a small old tanker.

Both ships were stationary throughout test.

I varied the distance to get accurate full Graticule distances rather than partial marks as it makes things more accurate.


I used the Kongo and this tanker because they represent both rather tall and short masts

IE: 42M for Kongo and 19.7M for tanker.

The Game manual states

Periscope on high range is 0.25 Deg for small graticule marks and 1 Deg for Large.

TBT is 0.2 Deg for small and 1 Deg for large graticule marks.

BTW: Its impossible to have 0.2 Deg for small Graticule markers on the TBT if the main markers are 1 Deg as there is only 4 spacings not 5 between large marks. :yep:


Here is my results :


Attack periscope: Small graticule spacings = 0.29 Deg
Attack periscope: Large graticule spacings = 1.16 Deg

TBT : Small graticule spacings = 0.16 Deg
TBT : Large graticule spacings = 0.64 Deg


In other words there is an error 0.04 Deg per graticle marker on both instruments, one larger the other smaller.

The error compounds if you were tracking on the surface with the TBT and then use the attack periscope for the final measurements.


The error may not sound like much but consider a Kongo at 1000M range useing the attack periscope.


Mast = 42M
Angle = 2.4 DEG

On your 0.25 Deg per graticule attack scope you see this as 9.6 markers.
Calculate 9.6*0.25 Deg = 2.4 Deg
Range to target = 1002 Meters.


But as we know the Markers are REALLY 0.29 Deg so 9.6*0.29 = 2.8 Deg.

An arror of 0.4 Deg or a more importantly a range calculation of 859 Meters.

A difference of 141 Meters or approx 60% the length of the Kongo Target.

A MK10 Torpedo travelling at 36Knots would take 8 Seconds to get 141 Meters.

Or alternately a Kongo can move 82 Meters in 8 Seconds at 20 Knots.