SUBSIM Radio Room Forums - View Single Post

Spectator · 08-01-09, 01:16 PM

I know the 3 minute (/ metric 3:15) rule, I know the length of target divided by time needed to cross the centerline of the periscope trick, so ... yes i know how to get the speed of a target.

Now here's my problem. Let's assume the target has a speed of 9 kts. Using some simple vector math you will find out, that, using a 46 kts torpedo, you will need a lead angle of about 11 degrees. Just point your periscope 11° towards the target, leave the PK off, make sure gyro is 0° and hit it. That should work, but here it doesn't.

Here's how Rockin Robins explains it ( the last picture)

Now, my problem is, that i definately know that my target (Medium Old Split) is cruising at 9kts, I verified that many times with different methods. But the 11° angle doesn't work. I need to use the angle for 12kts (about 14°) to hit exactly where I aim. How can this be?

My own speed is 0, but that shouldn't be a factor anyway, distance to target is somewhere around 1200yds but again, that shouldn't be relevant and the AoB is near 90°, also no surprise there. What am I missing here?

//edit: and he's not getting faster after the launch, i checked that too. It's dark and he doesn't spot the fish.
//edit2: and just to put some weight on my claim, that his speed really is 9kts ... I marked him on the map, went 18nm ahead, and exactly 2 hours later he was at the correct spot, not much room for error in my 9kt observation.

08-01-09, 01:16 PM	#1
Spectator Seaman Join Date: Nov 2002 Location: Germany now, Australia soon Posts: 31 Downloads: 53 Uploads: 0	Target Speed / Solution Problem I know the 3 minute (/ metric 3:15) rule, I know the length of target divided by time needed to cross the centerline of the periscope trick, so ... yes i know how to get the speed of a target. Now here's my problem. Let's assume the target has a speed of 9 kts. Using some simple vector math you will find out, that, using a 46 kts torpedo, you will need a lead angle of about 11 degrees. Just point your periscope 11° towards the target, leave the PK off, make sure gyro is 0° and hit it. That should work, but here it doesn't. Here's how Rockin Robins explains it ( the last picture) Now, my problem is, that i definately know that my target (Medium Old Split) is cruising at 9kts, I verified that many times with different methods. But the 11° angle doesn't work. I need to use the angle for 12kts (about 14°) to hit exactly where I aim. How can this be? My own speed is 0, but that shouldn't be a factor anyway, distance to target is somewhere around 1200yds but again, that shouldn't be relevant and the AoB is near 90°, also no surprise there. What am I missing here? //edit: and he's not getting faster after the launch, i checked that too. It's dark and he doesn't spot the fish. //edit2: and just to put some weight on my claim, that his speed really is 9kts ... I marked him on the map, went 18nm ahead, and exactly 2 hours later he was at the correct spot, not much room for error in my 9kt observation. __________________ Running silent, running deep, we are your final prayer Warriors in secret sleep, a merchantman's nightmare A silent death lies waiting for all of you below Running silent, running deep, sink into your final sleep Last edited by Spectator; 08-01-09 at 01:38 PM.