What Dissaray said: you'll take your fixed wire with the periscope at 180 instead of 000. It's the exact same process.

With the fixed line method you are sort of making a wall in the sea with your periscope line. Or something like a finnish-line, except [b]it doesn't matter when[b] the target crosses it, but how long it takes to cross it. You want this imaginary wall to be fixed in the world. Since a moving wall (sideways) is messing up the measurent.

This wall (the periscope line stretched into the distance) moves sideways when you are not looking along the bow-stern line and have a bit of speed yourself. If you are looking in the same direction as you are moving then your speed doesn't matter. You can go reverse or flank forward if you want and the target takes the same time to cross it. (well, flank speed is quite a bumpy ride and the bow starts to roll on the waves, so you better not exagerate)

If you are looking to the side of where you are going, some of your speed is directed along the periscope line, but some of it is also pointed away from it. This sideways component is messing up your speed measurement. Let's say you are traveling with a speed of 6 knots. And you have the periscope pointed at 10 degrees from the bow (010, or 350). This makes the imaginary wall from the periscope line move sideways with about 1 knot. And so too will the real target speed show 1 knot too low or too fast. (depending if the movement of the wall was against or with the movement of the target)

So the AOB is reversed for stern shots?

Steve

Only if you are attacking a convoy from in between the coloms of the convoy. In that case you would have, for example, if you have an AOB set to 90stb for your forward tubes you would have to switch it to 90port befor you switch from firing your forward tubes to your aft tubes. I forgot to do this one time and acsidentlaly hit the ship behind the one I was aming for.

Other than that you make an aft shot just like any other shot, with exception of having the back end of the boat facting the target and not the front end.

OK, yes, I can see if I were in the middle of a convoy obviously the AOB would change as you are on the starboard of some ships and port of others.

I was talking only about a single ship attack. So stern shooting is no different than bow shooting then. Good.

Steve

Thanks BillCar, very interesting method this fixed line, more simple and more accurate than the 3 mn 15.

Another important point for the manual targeting is the choice of the torp's proof. I had a lot of missed in bad weather conditions before I understood what happened.
Recently I fired two torps (impact, same proof) at a medium cargo in rough sea and wanted to take care of the proof, I fixed it 3 meters up as I would do in normal conditions. First torp, nothing, the second hit around the middle of the ship, means fired solution was perfect.
I used the external camera to see what happened : only one hit at the extrem limit off the hull !

I used the fixed wire method to make stern shots last night with no problem.

Fixed wire is great. The only drawback I see (of course, this is true for any method) is that you need reasonably good visibility in order to track your target far enough way to get its speed so you can turn and attack before they are right on top of you.

Steve

If they're far away and visibility is unsatisfactory for making an identification, you use the constant bearing method to get their speed (or you can do the 3m15 method, but constant bearing is equally accurate and takes less of your time up with plotting). Then when you're reading to make your attack run, you can do fixed line on your way in to reconfirm the speed reading you took from the constant bearing method. :up:

Hmmm.
Just got back from a patrol, and see I missed all kinds of fun on this thread.

With all the contributions, it realy turned out to be a great thread.

And more importantly, a highly productive one for Maillemaker.

Great job guys!