[REL] We Dive at Dawn

[keltos01]

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Originally Posted by joegrundman

Didn't the later war MkVIII have full variable gyro?

http://www.navweaps.com/Weapons/WTBR_WWII.htm

http://en.wikipedia.org/wiki/British...inch_Mark_VIII


keltos

[keltos01]

loading torp on a T








a rare view !

HMS/M Safari photo of destroyer hunting the sub by Capt Bryant



torpedoed tanker


http://adjunct.diodon349.com/photopoint/0025/0022.jpg

[joegrundman]

Originally Posted by keltos01

http://www.navweaps.com/Weapons/WTBR_WWII.htm

http://en.wikipedia.org/wiki/British...inch_Mark_VIII


keltos

sorry, i didn't see that those links referred to gyro angles at all

[keltos01]

that data on gyros is hard to find I read it in a book I'm currently re reading.

Merry Xmas

keltos

[keltos01]

Ben Bryant retired from active submarine duty in 43, so his book though very good, only goes so far.

p120 he uses the ninety bender to get a ship that is on a parallel course

"the column were 3 cables or 600 yards apart...the sights came on and we fired at the leading ship of the port column, angled 90° left."


he actually got this ship though at the time he thought hed' missed, but was already busy being depth charged.

nothing about the gyro going all the way like the american one. they were too close to one column to fire at 0° angle so they chose another target and set the torps at 90°.


they also used a slide rule to calculate the range, thus more prone to mistakes :

p 140 : " we steadied on the firing course and I passed the number of divisions on the periscope gradicule from which the attack team could calculate the range on a slide rule. The slide rule did not compete direct with such a small target as a U-Boat and you had to multiply or divide according to the technique employed. The slide-rule operator made a mistake, which was easy to do, and multiplied by two instead of dividing, and announced the range as about 3200 yards. I spotted the mistake but did not remark upon it as the sights were just coming on, I just mentally noted that hte range was 800 yards."

the trim officer then let the boat go under periscope depth as he thought he had time to trim the boat better, and they missed the firing opportunity on the U-Boat...

keltos

[joegrundman]

90 degree shots are not actually that difficult so long as you are competent at estimating target length and range -and with one of those you can calculate it all easily enough with a slide rule.

Torpedo parallax is much less of an issue at 90 degrees than at other large gyro solutions.

You already know, with a fixed 90 degree shot what the gyro is and that it is running perfectly perpendicular to your course, so all you need to know is the total forward distance the torpedo will travel from the position of the periscope before it settles on the 90 degree track.

Let's say the scope is exactly at the midpoint of the submarine, then the forward motion of the torpedo is half the length of the submarine, plus the straight run it makes to clear the submarine, and then the turning radius to get onto a 90 degree track.

So with a 100m sub, and a 10 m reach (the straight run) and a turning radius of 10 m, the total diference from the submarine point of view and the torp is 50+20=70m

So with the scope pointed at 90 degrees, the torp will hit a parallel point 70 m further forward.

So to setup your shot and add the 70 m at the target. For a 140m target, for example, to hit dead center you aim for a point at the bow/stern depending.

anyway it's how i used to do it when messing around with no tdc targetting

[Hitman]

I must sadly announce that I found a further problem with the british TDC mod, that complicates it even more

Apparently, the Gyro Angle needle on the TDC's own ship dial (Lower one) will only move as much as the torpedo can actually turn. Keltos, in your modified torpedoes (Maximum 15º Gyro Angle) the needle will lock at 15º either side of the bow, and I'm afraid that if the Gyro Angle is locked at zero, then again the needle will not move at all. This means that the needle is useless for indicating the necessary lead angle as it should do, and we are unable to replicate the way the british TDC worked. Either the torpedoes have more than zero GA, and then all will work as with the US TDC, or they have zero GA and then we are clueless about when to shoot them.

[keltos01]

Originally Posted by Hitman

I must sadly announce that I found a further problem with the british TDC mod, that complicates it even more

Apparently, the Gyro Angle needle on the TDC's own ship dial (Lower one) will only move as much as the torpedo can actually turn. Keltos, in your modified torpedoes (Maximum 15º Gyro Angle) the needle will lock at 15º either side of the bow, and I'm afraid that if the Gyro Angle is locked at zero, then again the needle will not move at all. This means that the needle is useless for indicating the necessary lead angle as it should do, and we are unable to replicate the way the british TDC worked. Either the torpedoes have more than zero GA, and then all will work as with the US TDC, or they have zero GA and then we are clueless about when to shoot them.

then set them in the .sim to 90° angle. it'll just be that skippers will only use either 0° or 90°, not trying to cheat by using other angles ?

would that do ?

keltos

[elanaiba]

Originally Posted by keltos01

that data on gyros is hard to find I read it in a book I'm currently re reading.

Merry Xmas

keltos

The British report on HMS Graph (U-570) - January 1943 - mentions it:

http://www.uboatarchive.net/U-570BritishReport.htm

Gyro Angling :
"Graph":
Any gyro angle between 0° and 90° R or L can be set automatically.

British Practice:
traight running or 90° angles only are used. The external angling gear on each tube must be set separately by hand.

Back to the problem at hand, which Keltos brought to my attention... I don't have more solutions than you guys. I should have thought about this one at some point and have the programmers ad some extra stuff to account for British practice, which was not completely unknown to me

I wonder if the firing button could be blocked when the gyro angle was different from a set of values?

[keltos01]

from hitman :


http://www.subsim.com/radioroom/newr...eply&p=1556698

It's actually very easy with the US TDC, even if you set the torpedoes to the correct zero degree Gyro Angle. Here's how to do it:

1.- Determine target course, approximately, either by eyeballing AOB (To start) or plotting (Visual or radar). Get on a course that is perpendicular or, at least, something between 45º and 90º of the enemy track (So that the torpedo has enough angel of impact and does not make a dud)

2.- Feed the TDC with all the data, and start the position keeper. Make regular corrections as you see fit, by entering new data (New estimates of speed, distance, AOB, etc, as usual)

3.- Your reference for knowing when to shoot is the Gyro Angle needle on the "own ship" dial (The lower dial in the TDC). When that needle points exactly to the bow of the ship silhouette in the dial, you must shoot the torpedo. Why? Because at that moment the necessary Gyro Angle to hit the target is zero, which is exactly the only thing your torpedo is capable of

That's more or less how the british TDC worked, only that when the GA was zero you also got an audible warning in the form of a bellring or buzz

Originally Posted by Hitman

Here's a graphical example:



The red arrow represents the direction your bow is pointing at. A torpedo that follows the same course as you, straight from your bow, is obviously a zero Gyro Angle torpedo, and it will follow the red arrow in its course -same as your ship's course.

Then the moving needle in the dial, highlighted in green represents what Gyro Angle must your torpedo do in order to hit the target that is shown in the upper dial.

Hence, when the needle matches the red arrow, that means that the torpedo must not turn at all to hit the target, i.e. it will be a Zero GA shot, and the moment of shooting has arrived.

Is it all understandable?

[Hitman]

Back to the problem at hand, which Keltos brought to my attention... I don't have more solutions than you guys. I should have thought about this one at some point and have the programmers ad some extra stuff to account for British practice, which was not completely unknown to me

I wonder if the firing button could be blocked when the gyro angle was different from a set of values?

Many thanks for taking some time to consider the problem Dan

Locking the fire button could be a solution, even if not a perfect one. If we can make it display the grayed-out graphic normally and highlight in red when the torpedo has a zero GA that would be somehow similar to the original buzzer and burning light in the Fruit Machine.

But I have no idea how to do that

Any suggestions on how to link the button graphic to the GA?

If the own ship dial was stationary, we could maybe solve it by converting the GA pointer into a circular dial with a hole that shows the button and makes it available only when the dial comes to zero. But since the own ship dial also rotates, the pointer shows the zero GA in any part of it, so we would need to have the fire button rotate all around with it, which would be confusing and probably also impossible to do.

Hmmmmm another alternative, since the own ship must somehow point close to the target line of sight (Top of own ship dial) could be to have the ownship dial be larger and hide the fire button until the own ship dial aims close to the line of sight ... say some 45º either side

But again we would stumble against the same problem, i.e. we would be free to shoot any moment with an instant-GA update on the fly insde those -/+ 45º

Not to mention that I absolutely lack the skills for modifying the menu.ini to do the trick with the dials

[keltos01]

side note :

isn't there a british sub in SH5 ? is it the U class ? maybe we could get its model and add it to WDAD ?

keltos