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So what to do, if I want torpedo with mathemathic method?

The TDC helps you with your target solution.

You have to find the distance to target, as the angle on bow (AOB) and the speed of the target.
This data is/was necessary to make the TDC calculate the correct turning angle for the eel after leaving the tube.

If you want to shoot straight and hit the target perpendicular, you have to position yourself correctly and translate the speed of your torpedo into range and accordingly the speed of the target into its range/traveling distance to meet the torpedo and the ship at the impact point.

You have to calculate the bearing showing in your periscope matching the position of the target in relation to the position of your U-Boot/your torpedo in relation to the speed of both objects.

Assuming the ship moves at 10 Kts and your torpedo runs at 30 Kts.
The ship moves 300 meters while your torpedo moves 900 meters.
What is the correct angle in your periscope to release the torpedo?

:)

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Hmmmm, but first i need to know from which angle i am looking

Hmmm, it is not stupid what u said. I should count it reverse to mathemtaic trygonometry??

I have distances and from it i have to designate angle?

What you should do is what was actually done historically. The calculation included a fixed speed which was preset for the torpedo. (Some had three speed settings, others only one speed.) Based on this torpedo speed, the target speed, torpedo reach, torpedo turning radius, and torpedo track angle at impact, you calculate the torpedo gyro angle setting, which is programmed into the torpedo, and a lead angle, which is the bearing of the target from the submarine when the torpedo must be fired. Then wait for the target to reach this bearing and fire. That is how it was actually done. The TDC (TVR) in SH3 will do most of the calculation for you. You have to enter the target speed, target angle on the bow, and range, and the TDC will do the rest. (Especially the German TVR, which will calculate the lead angle for you!)

The Submarine Torpedo Fire Control Manual http://www.hnsa.org/doc/attack/index.htm is the actual training manual used by the US Navy. It describes in detail all the calculations, as well as attack tactics. Same physical situation applied in U-boats. The KM's Submarine Commander's Handbook can also be found here http://www.maritime.org/doc/uboat/index.htm. It's lees mathematical than the US version, but does describe KM tactical doctrine in detail..

I start understanding and thinking how to count this angle.

But how i can check distance to enemy ship???

If you shoot perpendicular this greek guy Pythagoras says distance is irrelevant.

For all other scenarios you may want to use the stadimeter in your periscope (for now, as a newbie).

Watch this: https://www.youtube.com/watch?v=87ga-Jmef7k

Several ways:

1. Some versions of SH3 use a stadimeter (split image device) to measure the range.

2. Hitman's Optics and Hitman's GUI use the angle measurement reticle built into the scopes.

3. You can get a range estimate from your Weps Officer or hydrophone operator.

4. You can use the "God's-eye view" on the nav map.

Method 2 is historically accurate. 3 and 4 were used, but the game version is just too good and never makes a mistake. And real U-boat periscopes didn't have a stadimeter.

The fifth way is using maneuvering board techniques:

https://archive.org/details/maneuveringboard00unit

Let's keep it simple, my dotcomrades.

He's on vanilla 1.4 and just startet to play.
Let him do the basics and then he will find all the other sophisticated stuff out of interest.

The basic lead angle intercept formula:

torpedo speed*sin(lead angle)= target speed*sin( AOB)

In math this relationship is based on the law of sines (Wiki).

Consider your targeting triangle in terms of speeds and angles only. Not distances! That is only important to predict the time of the impact. If the speeds and angles of the triangle are correctly determined, then the impact is virtually guaranteed. (ignoring the target trying to avoid the torpedo)

The TDC already works this formula out, based on target speed dial, torpedo speed setting and AOB dial. (if you didn't know, on the F6 page) It then adds this to the current periscope bearing and tells the torpedo to turn to there. But a further correction is added to account for the forward position of the tubes and the straight section and turn of the torpedo track when launched. But it's effect is minimal unless at really close range with large gyro angles (large torpedo turn from the bow).

You want to know the distance and the bearing to help with plotting. And know when not to shoot because the target is too close. Plotting helps to determine the target speed. But there are also other ways to determine that. So, for aiming, distance by itself isn't the driving factor.

No, not because of perpendicularity. It is because the targeting geometry can be reduced to a triangle of a specific shape (doesn't have to contain a right angle), but arbitrary size. So it doesn't matter how far away the target is. If the target is further away, it is also further away from it's point of doom by the same proportion, and the torpedo has to travel a longer distance to that also by the same proportion. The shape of the triangle won't change if you make every side bigger by the same ratio.
The torpedo can impact the target hull at any angle. It's just that perpendicular hits allow for the best margin of error on the target speed.