Why is a straight shot assumed to be the perfect firing angle?

[fireship4]

Why is it that a straight shot is assumed to be the perfect firing angle?

I used to believe that this was because if a torpedo has to turn this will add an error but im not 100 percent sure now - isnt the "torpedo reach" or "torpedo advance" as it's called taken into account? I'm sure you can see it on the attack map.

Would it not be a better solution to have yourself on the target's course and fire when the range is smallest and the track is close to 90 degrees off his bow? This way you can use bow and stern tubes almost simultaneously - maybe bow shots wait a few more seconds until track reaches 90 degrees on the map, i don't know - better than turning around.

Maybe there is some mixup between AOB and gyroangle. I was about to call this thread "why is 90 degrees assumed to be the best shot" but i guess thats because the ship presents his full side to you and you have more chance of hitting. But this doesn't mean you have to shoot straight aswell...

Or maybe im wrong and having a gyroangle causes error.

UPDATE I tried it from 1000 yards at a stationary target with 8 tubes simultaneously. All hit. Text in below picture that is unclear says "20 deg off perfect angle".

Next I will try a moving target...

[tedhealy]

The best firing angle is the one that hits.

Also don't forget you are more likely to get duds early in the war when the torpedo hits at 90 degrees.

[tedhealy]

Here's a bit of advice from an actual sub manual

http://www.hnsa.org/doc/attack/index.htm

(d) The optimum torpedo track angle for a 16 knot target for a 46 knot torpedo is about 110 degrees and for a 29 knot torpedo about 125 degrees.
(e) The greatest advantage of straight fire (small gyro angles) is that errors in torpedo run have no appreciable effect on the solution. Therefore, when the range is inaccurate, as in stadimeter and telemeter scale approaches, the submarine must maneuver for a small gyro angle shot.




If I have the time, I set up for a near perpendicular approach, but offset it by about 10 to 20 degrees to avoid the higher chance of duds.


If I don't have time for a long setup or the ships are escorted, I take what I can get.

[fireship4]

I was reading through the manual (infact i had posted a link to those sections of it onto the board just before) to confirm this when i realised that you will still get the shot you want with this method. I'll post a couple of annotated screenshots as I test it.

UPDATE Here is a snippit of the relevent part of it:

810. ANALYSIS OF TORPEDO FIRING:
(a) Straight Fire
Torpedo firing in which small gyro angles (less than 30 degrees) are used is considered to be "Straight Fire". The curves plotted on plates XVII and XVIII for 46 and 29 knot torpedoes were developed by plotting the deflection angle against the torpedo track angle for different target speeds. It should be noted that in all cases the gyro angle was zero.
(b) The slope of these curves at any point is the instantaneous rate of change of deflection angle with torpedo track angle. The optimum torpedo track angle for any given target speed is the torpedo track angle for which the rate of change of deflection angle is the least. This is indicated on the curves by the shaded areas.

8-8

[fireship4]

Yes it seems to work with a moving target no problem. And seeing as the gyro angles im using are considered "straight fire" and the track angle is within the guidelines (i think) then im going to try it out more on patrol (when i get out of my lovely s-boat) - I advise other captains to give it a go aswell. The red text above is wrong

Heres some more from the manual:

(c) It is within this range of torpedo track angles that the greatest amount of course error can be absorbed. From a study of the curves it is evident that the maximum deflection angle is obtained when firing on the optimum torpedo track angle and that the optimum torpedo track angle has a value equal to 90 degrees plus the maximum deflection angle. It is also evident that as the target speed increases for any given torpedo speed the slope of the curves becomes sharper. This means that the higher the target speed the greater the rate of change of deflection angle with torpedo track angle. It is therefore true that the optimum torpedo track angle is more effective for absorbing errors in course when the ratio of torpedo speed to target speed is large. It therefore may be stated that the optimum torpedo track angle is a good mean torpedo track angle for firing a salvo of torpedoes if the target speed is less than one-half of the torpedo speed. (d) The optimum torpedo track angle for a 16 knot target for a 46 knot torpedo is about 110 degrees and for a 29 knot torpedo about 125 degrees.
(e) The greatest advantage of straight fire (small gyro angles) is that errors in torpedo run have no appreciable effect on the solution. Therefore, when the range is inaccurate, as in stadimeter and telemeter scale approaches, the submarine must maneuver for a small gyro angle shot.




Actually, from this (correct me if im wrong) 90 is not the perfect track angle (degrees from bow torpedo hits on i think) for our torps. Its more like 115 degrees (with mark 10s)?

[joegrundman]

The specific reason why straight shots are more accurate than curved fire is torpedo tube parallax. it's all there in the manual that you are discussing.

the manual also says that if you have radar range finding, there is no appreciable difference in accuracy with curved fire, but regrettable, radar rangfinding is incompletely modelled in SH4