Target Speed / Solution Problem

[Spectator]

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.

[I'm goin' down]

Accroding to Old Tex's chart on entitled Cromwell Method of Torpedo Attack with Torpedo Speed at 46 kts, target speed of 8.9 kts, AoB set to 38 degrees, ship run of 900 yds from firing to impact, your periscope aiming angle is 7 degrees.

The chart is based upon target speeds from 1 to 35.6 kts and has a column for 31, 36 and 46 kt. torpedo speeds.

Does this help?

[magic452]

I shoot vector shots all the time and never miss the way you describe.
If I understand you right, if you shoot on the 11° bearing you are missing aft of the target. Two things can cause this.

First are the doors open, I sure they are as your not new to the game.

Second If the TDC has old data in it you must set your scope to 0° and than pull down the range thingie all the way down, should give you a range of about 1400 yds. make sure you have selected the proper tube and than click the send range button TWICE. You can see the PK line up right with the second click. Use 180° for a stern shot, select a stern tube first.

Just setting the AoB to 0° is not enough. Also double check that speed is exactly 0 and the gyro angle offset on the PK is at 0.
I've miss one or two on the gyro offset thing.

I just dropped a 9000 ton troop ship at 3100+ yards and a 7000 freighter at 4200+ yards. All torps hit right on the numbers.

Another though, a good target course line helps but a 1200 yds that shouldn't be to critical but at longer ranges it is.

You sometimes have to allow for the target to change speed when she see the torp wake.
In good conditions this can be quit a bit of change, either speeding up or slowing down.
I usually force them to slow down by shooting right at or in front of the bow.

Hope this helps

Magic

[Spectator]

Thanks for taking the time to answer.

I tried it again today, and guess what. The first try, every shot was a hit ... I didn't change anything in my routine, so I was confused and tried again. Same result ... now I was really confused ... after about an hour I finally figured it out ...

... I found the thing I was missing: Yesterday I kept loading a savegame, where apparently my boat was not properly aligned and therefore the lead angle didn't fit When I returned to try it again today, the savegame I loaded was a different one, which was saved a few minutes earlier, where the boat wasn't in final position yet. Without thinking about it I aligned the Boat and my solution worked like it should ...

I actually made a video (kind of a tutorial) to trace my steps, the align-error isn't in it though ...





//edit: just to clarify: not properly aligned might be a bit too vague ... what happened was, that my rudder wasn't centered and the boat still moved a bit

[I'm goin' down]

After losing three drafts of my detailed reply post, I give up. He is the short version. See the Sticky in the Mod Forum re Easy AoB. It solves all of the attack issues re the Dick O'Kane and Cromwell attacks, is a technolgicial break through and a game changer. Its discovery was disclosed on June 20, 2009 in a post by Niclolas, who, in conjuntion with ddgrn, expanded it to encompass changes to the initial data settings for Speed and Range, in addtion to original modifications to AoB data settings. It can be downloaded and applied via JGSME. The Easy AoB thread has had 5,503 views as of this post since the date of Nicolas' initial post. Seasoned, well regarded skippers such as Rockin Robbins have noted the brilliance of its application. It will expand your appreciation of the game if you are not already familiar with it.

Sheesh, my long versions were well written, but this will have to suffice.

[Rockin Robbins]

Yes, the one thing that can change the lead angle if you have the target speed and course nailed down is your own course. The sharper angle toward the target you take, the smaller the lead angle gets. If you're not on the course you think you are, you are almost certain to miss astern.

But you already figured that out for yourself!

[I'm goin' down]

Here is what I forgot to post in my reply. The Easy AoB mod permits attacks at various angles without the computations and detailed graphing required in a John Cromwell attack. This morning (or was it last night) I played the single mission Guadalcanal Reinforcements with the Easy AoB mod. I fired one fast and one slow torpedo at a light cruiser at approximately 5,500 yards. I do not know the yardage at impact but the fast torpedo hit. The course of the light cruiser was 156 degrees (a steep angle). The sea was calm with unlimited visitibily, making getting the range easy. The difficulty is getting the range and aspect ratio at night when you cannot see the target well enough to lock in the range and aspect ratio. When that situation occurs, I fall back to the Dick O'Kane attack, or in rare cases, plot an attack by sonar (Werner Sobe style).

[magic452]

Spectstor VERY nice video. Excellent method for setting up a vector analysis attack.

Glad you found your problem, I should have though of that last night as I have done the same thing. Once! But fortunately I found the problem right away. I learned to check out ALL of the set up.

Magic

[Rockin Robbins]

Spectator: beautiful video! Perfect technique there. Nisgeis would be proud of you! It would be great if you'd drop by the Sub Skipper's Bag of Tricks thread and post a link and short recap of your vector analysis attack. Good show!

[Spectator]

Thanks for the help, hints and comments.

I left some notes in the Bag of Tricks