how to re-set the tdc

[Joe S]

I had a great shot at a large merchant right in front of me at about 500 yds but for some reason the TDC was aimed at a target off my stern. I tried re-entering the bearing and range and even hit the button to shut the tdc off and start over but it would not re-set. two torpedoes were wasted. What is the fix or correct procedure? Thanks! Joe S

[Rockin Robbins]

Entering new data replaces the old. In order to switch to a new target you have to enter info in this order (the first two can be reversed without bad effects): speed of new target, AoB of new target, and last (that is important!) the range/bearing of the new target. It is not necessary to turn off the position keeper at all. Make sure you didn't forget anything by switching to the attack screen to ensure that your target is properly entered before you fire. Always verify that you have a good solution before firing, as the real boats also did.

If you do not have time for that, can you afford to waste a torpedo? If not, start over with a new setup. Patience, grasshopper!:hmm:

[Joe S]

Thanks for the help rockin robbins! I had the target locked in the scope when I re-set with the new bearing and aob,does it make any difference if the target is locked or not? Thanks! Joe S

[Powerthighs]

No, it doesn't make any difference. When you click the "send range" button the bearing the periscope is currently pointing to is sent as well. Having the target locked just makes sure the scope stays pointed at the middle of the ship whlie you move the mouse to click the button.

[Torpex752]

Make sure you didnt have a stern tube selected for a forward shot.

Frank

[Rockin Robbins]

No, the "is the lock necessary" question was the first step in my development of the Dick O'Kane targeting technique, where I turn the @#$@# PK off, throw target range out the window, sight the TDC at a presently empty spot in the ocean and aim so accurately that I can hit 5 yards aft of the bow crane.

The periscope lock has nothing to do with targeting other than holding the periscope's crosshairs on the middle of the target. For conventional targeting this is a great thing because you're doing so much input all at once.

Also, the PK must be on to show the impact point on the target. With the PK off, you can see the torpedo track on the attack screen but not the impact point. With the Dick O'Kane you never see the "x" on the target and you won't miss it either.

[Joe S]

I assume you got the Dick o'Kane method from one of his books, both of which I have read , but not recently. If you did get the method from his books, can you tell me which one and approx where so I can re-read that section?

You probably already know this but maybe some people do not: once you establish the amount of lead in degrees for a given target speed, that angle of lead is good no matter what the range. In the example you gave in the above referenced post, a lead of 9 deg was used based on the speed of the target. If you have an accurate target speed calculation, all you have to do is aim the torpedoes the given amount of degrees ahead of your desired point of impact and you should get hits.
I believe your method is sound, but have not tried it. After I try it I may have a few more questions. Thanks for your help. Joe S

[Munchausen]

When you use the stadimeter to insert range, you also insert bearing. The TDC then uses your crosshairs to determine the hit point (white "x" on the attack map when PK is engaged). If the target is locked, the crosshairs will be centered on the midsection of the ship ... but, if you take a stadimeter reading with the crosshairs centered fore or aft (no lock) then your computed hit point will also be fore or aft of the target's midsection.

[Rockin Robbins]

Originally Posted by Joe S

I assume you got the Dick o'Kane method from one of his books, both of which I have read , but not recently. If you did get the method from his books, can you tell me which one and approx where so I can re-read that section?

You probably already know this but maybe some people do not: once you establish the amount of lead in degrees for a given target speed, that angle of lead is good no matter what the range. In the example you gave in the above referenced post, a lead of 9 deg was used based on the speed of the target. If you have an accurate target speed calculation, all you have to do is aim the torpedoes the given amount of degrees ahead of your desired point of impact and you should get hits.
I believe your method is sound, but have not tried it. After I try it I may have a few more questions. Thanks for your help. Joe S

In his books, O'Kane tells how he dispenses with the necessity of knowing the precise range and turns off the position keeper during some attacks. With the help of aaronblood and gutted, we reasoned out that the most likely type of attack which met those characteristics was a modified Fast-90 attack from the U-Boats. Gutted had made a chart showing the lead angles for German torpedoes, which he modified for fast and slow Mark 14's.

For the fast-90 attack to work, you look up the lead angle for the target speed. First you set the torpedo to run up the zero bearing. Then you point the periscope at that angle before 0º, 360 minus the angle for targets moving left to right and the angle for targets moving right to left. As juicy parts of the ship cross the crosshairs, shoot.

Then it was left to me to figure out how to use the blasted thing. At the time we were all under the impression (the manual said so) that in order to work the stadimeter the periscope had to be locked on a target. This was bad. So I loaded up WernerSobe's Natural Sinking Mechanics test mission and went to work. After much trial and terror, I found that the periscope didn't have to be locked on anything to send a bearing. You didn't even have to use the stadimeter when you sent a bearing. You could set the torp track across empty water by pointing the periscope at a bearing and pressing the send range/bearing button. Then you sent a bearing without a range. Perfect!

So I set up for a fast-90 with gutted's chart. 9 knots = 11º, blah, blah, blah, shoot! And the torpedo passed well in front of the target. @#$@#$%@#$$!!!! I analyzed the attack and found that I had used the column for slow torpedoes on a fast torpedo. And I realized that you would have to have a separate column for Mark 18s and cuties and... This is so complicated nobody will be able to hit anything. What now?

There was only one option: find a way to toss gutted's chart. And then I realized that we already had a chart that picked its own column: the TDC! As long as the PK was off, all the TDC did was calculate the lead angle for a target moving at a certain speed for a selected torpedo. So the Dick O'Kane technique was born. No more chart!

Now, you measure the speed of the target and enter it into the TDC. Doesn't matter which direction it's moving in, you set that with the AoB. Now you set the AoB for 90º minus the number of degrees from zero you're going to shoot! If you're going to shoot at 350, your AoB will be 90 - 10 = 80º. Your target is moving left to right so your AoB will be starboard (right) 80º. Lastly we'll select a forward torpedo tube, point the periscope at 350º and press the send range/bearing button. OK, now maybe 15 minutes before you shoot we're all set up and all we have to do is wait. You can look all around with the scope and not mess up the shot.

OK, here comes the boat. You don't even have to keep the scope up, just look at the sonar bearing and take a peek now and then to make sure he hasn't changed course. You're a hole in the water here. When the sonar bearing gets to about 340, raise the scope and point it at 350. Open up a couple of tubes. As the front crane passes the crosshairs, shoot. Cycle to the second tube and shoot it as the aft crane is in the crosshairs. Two booms will follow and the ship goes down. You had the whole shot set up 15 minutes before the ship got there!

Is that as easy as it gets? I think so.

[Joe S]

I was just about to post another message when I saw your recent post. In the course of trying this out, I discovered, I think, that you need to set the range to something in order for it to work, so I set it at 1500. First, of course, you set the target speed. Then set aob 90 left or right depending on the setup. Then set range to 1500. THEN, pick a target. Aim the scope where you want to hit, click the send bearing button and shoot. Move the scope a few degrees to the next spot on the target and shoot agian. Pick another target. Aim at a spot on the target, click the range button and shoot. Pick another spot on the target and shoot again. (too bad the game doesnt automatically select the next tube) so far, in my limited testing, you need to click the send range button for each target but not each shot. I havent tried it in an ideal setup, with two or three targets between 350 and 20 degrees and under 2500 yds but so far in the Borneo mission I have been getting hits on multiple targets, not 100%, but definately worth pursuing. Thanks! JOe S

[jazman]

It's funny, but I'm pretty bad at everything except for the O'Kane method. Somehow that method has "taken", I even figured out all the trigonometry.

I've tried with the PK all sorts of ways, and I just can't get range right. I hate the Stadimeter and all its works.

[Joe S]

Jazman,

forget about the range, it means nothing. The reason is, once you know the amount of lead, the angle of lead stays the same no matter what the range. I normally set the range with the rangefinder, but I use averages for the type of ship. for example, I enter 98 feet for the mastheight of all large freighters. Then I estimate the range with the split image, etc, but I do it mainly to replicate what the original captain or fire control officer did. Since most of my shooting is done under 1500 yds, I manually adjust the range once the target gets in close so that I get an accurate representation of the setup on the attack map to confirm the solution. If range is your main problem, you are in good shape. I hope you find this helpful. Joe S

[Rockin Robbins]

Originally Posted by jazman

I've tried with the PK all sorts of ways, and I just can't get range right. I hate the Stadimeter and all its works.

Yes, hating the stadimeter is a healthy American thing to do. I'll bet there was some cursing of the stadimeter going on aboard the real subs too.

[jazman]

Originally Posted by Joe S

Jazman,

forget about the range, it means nothing. The reason is, once you know the amount of lead, the angle of lead stays the same no matter what the range. I normally set the range with the rangefinder, but I use averages for the type of ship. for example, I enter 98 feet for the mastheight of all large freighters. Then I estimate the range with the split image, etc, but I do it mainly to replicate what the original captain or fire control officer did. Since most of my shooting is done under 1500 yds, I manually adjust the range once the target gets in close so that I get an accurate representation of the setup on the attack map to confirm the solution. If range is your main problem, you are in good shape. I hope you find this helpful. Joe S

Thanks for the advice, I have the O'Kane method down cold. And I worked the trigonometry so I understand why the range doesn't matter. It's when I use the PK for non-O'Kane shooting that I have problems with range.

[Joe S]

Jazman:

Range doesn't matter with either method. If you want, you can pre-set the range for the distance to the target's track at the point of firing. If you are off by a little or a lot it makes no difference. Test the theory in the training mission and let me know what you find. Joe