Spread vs Own Boat Movement

[WhiskeyBravo]

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.

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.