Spread vs Own Boat Movement
 

As a relative newcomer to the SH4 series I'm getting on quite well with the full 'real' settings. I've got manual targetting with the TDC sorted and I can cause mayhem and destruction when I get in amongst a convoy. :lol:

One things puzzles me a little though. Why input a spread into a slavo when the relative movement of your own sub and that of the target introduce a 'natural' spread? ie by the time a second torp has been launched both sub and target have moved a little.

Conversely, if I wanted to get 3 torps to hit in exactly the same place I suppose I could use spread to counteract the natural spread mentioned above?

I know that spread was used to make it harder for a ship to avoid an incoming salvo but, again, surely the relative movement of sub and target would build in some spread.

Any skippers out there with a good explanation of spread?

Cheers all,

WB.

Also what about simply aiming your periscope centre line at different points of a ship...? (probably only useful in full auto mode).

In SHIII you could choose a group of torpedos to be fired and the spread angle was automatic. I'm not sure in SHIV if it is possible to group torps, but certainly adding a spread lets you alter the path of torps without altering the TDC data.

Dave

If you're on full manual targetting your torps will go to x on the position keeper regardless of where you fire them from. So when setting the spread angle you are aiming to the left or right of the white x on your attack map.

Basically the TDC keeps altering the firing solution over time and takes your sub's movement into account, so each torpedo is fired to that solution despite the delay between shots. In theory, if you knew that your solution data was 100% accurate, you would never fire a spread - you would fire each torpedo in sequence at a zero degree angle to your solution.

However, it is highly likely that your target speed, AOB, or even target ID (and hence range) may all be a bit off. This means your solution will be WRONG, so if each torpedo is fired at the native TDC solution they will all miss.

A spread is an insurance policy against small errors in your TDC data input. As an example, let's say you have estimated the target's speed at 5 knots, and it is moving from left to right.. Fire one torpedo as per normal - let's call that the "5 knots target speed" torpedo. For your next shot dial in 1 degree to port- that will be your "4 knots target speed" torpedo. Then for your third torpedo dial in 1 degree to starboard, and that is your "6 knot target speed" torpedo. There is virtually no chance that they will all hit, but at least one probably will... This is the way to go if you think it is unlikely you will get the chance to set up for a second attack if the first one fails.

Obviously the exact degree of spread deviation is a bit of a guess. I always use 1 degree simply because from reading actual patrol logs that seemed like a pretty standard approach... I find it works quite well. Plus it's realistic!