Tactics to intercept a convoy

[von faust]

Once you receive the radio position, speed and direction of a convoy, which is you tactic to intercept it ?
I calculate based on data available to me the point of interception and.....

- You decrease the speed and start to listen whith Hydrophone ?
- You set a route in a determined area ?
- What ??? :D

[Ablemaster]

1/ I draw line from caontact to give approx course.
2/ Use compass to draw FOC's [furthest on circles] at whatever target speed is eg: 12 nm intervals, for 12kt's
3/ This will give approx position at a given time.
4/ I use imperial as its what im used to and is easier for me.
5/ Just plot a course for your boat to intercept contact/convoy, hover mouse over position of WP to see ETA.

Simple and very effefctive method, hey why complicate things :)

[convoy hunter]

I just go a little more ahead if I am close and when I take position to the ahead of the convoy I listen to it by hydrophone to see if it is close to me

[kylania]

I'm not entirely happy with the intercept image, but since I made it at 5am I won't worry too much about it, but here's how I intercepted a convoy last night. This is with map contacts off, so no ghost to follow for me.

http://img126.imageshack.us/img126/2127/firstreport.jpg

Here you see the first contact report, at 05:26 about a large convoy 614km away, moving towards me at 13kts. What you don't see is that at the time I started this plot it was already 05:45, so I should have taken that into account.

Next comes the big messy picture!

http://img176.imageshack.us/img176/9128/interceptpoints.jpg

Step 1: I use the protractor to draw from my u-boat to the contact, then out along it's path of travel. When I did this, I made three mistakes. First was waiting so long to start it, second was not bringing the line out far enough and third was not getting the angle of travel perfect.

Step 2: I draw a line from the contact out along it's direction of travel according to it's speed. Since it's traveling at 13kts and was 600km+ away, I picked a multiplier of 20, meaning the line I drew was 260 (13 x 20) km long. If we were closer I might have picked a multiplier of .5 or 2 or something to plot a line 6.5 or 26km long, depending.

Step 3: I use the compass to draw a circle from the end point of the line I drew in step 2 which is equal to my speed (13.6) times the multiplier I used before, which would be a circle with a radius of 272 km.

Step 4: I find the point where the circle crosses the original bearing to the contact, the first protractor line I drew. I measure the angle from the end point of step 2 to the meeting point of bearing and circle then towards the contact. In this case you can kinda see it's 32 degrees.

Step 5: I now take that 32 degrees angle and measuring from the line towards the contact, to my u-boat, then towards the path of travel of the contact and draw out the 32 angle line till it crosses the travel line. This is where I made another mistake, since the original protractor I hadn't drawn out long enough, so I had to use a ruler to make it longer. That's the extra 170km line there.

Step 6: The point where the step 5 angle and the step 2 course lines meet is where I'll intercept. I'll place my waypoint at that point and head towards it at my current speed. It's Mark 1 in that image.

So now I'm chugging along towards the intercept point. I draw a 30km circle around the point to represent basically the hydrophone range around the spot where I should be able to hear the convoy.

http://img69.imageshack.us/img69/7811/earlyarrival.jpg

What's this!? At 17:28 I get a hydrophone contact from my sonarman saying he hears something coming from the general direction of where the convoy should be. But as you can see I'm still some 80km or so away from the intercept point!

In order to cheat a little I draw out a 50 degree angle from the front of my boat to the left (360 - 310 contact bearing = 50 degrees port) and send my external camera to see what's there. :oops::cool:;)

http://img412.imageshack.us/img412/3103/thereitis.jpg

And there it is! The beautiful, battleship escorted giant convoy! Turns out it was only traveling at 9kts by the time I reached it (which is why I met it ahead and past it rather than right on) and also changed course a bit too I think. It's changes like that which can cause you to miss convoys a lot, especially at ranges of 600km+ like this one was.

So, took me 12 hours or so to intercept it, and I almost missed it, but I got close enough to be able to intercept and sink 4 ships from it!

[walsh2509]

I've done most of that in SH3 SH4 , but now in SH5 I still use it but with Map Contacts On ... As you draw out your course a "ghost" contact comes out from the main contact. And as your speed increases the "ghost" contact recedes back towards the Main contact. Now I have done this a few times and its worked but other times, I've done the exact same thing and sailed up to the Main contact on the map and as I get closer, the distance on the contact goes down and down until I am 1km from this map contact and they are NOT there ?

As I go past this contact the distance increases, go back again and it goes down as it should be , but there is no ship there ?

[Westbroek]

I haven't noticed any kind of consistency with those odd "ghost" contacts in the map during course plotting. Honestly I think if you actually find the contact using those it's luck. I don't think they have any bearing on whether the course your plotting will intercept or not. Anyway, if I'm wrong and they do accurately represent the estimated position of the convoy at different times, then that's ridiculous and they need to go. :D

[kylania]

Anyway, if I'm wrong and they do accurately represent the estimated position of the convoy at different times, then that's ridiculous and they need to go. :D

Of course they do represent that. It's the same math as in my example above there. It's just a handy way for those with map contacts on to skip all the triangle drawing, but if you plot out the intercept using the above methods or MOBO or whatever your preferred method, you'll end up with the same location on the map.

If you find it "ridiculous" just turn off map contacts.

[SabreHawk]

On using the ghost icon, it must be remembered that this projected path is only reliable when the contact first appears on the map. As the contact gets older, it's no good anymore cause the ghost's postion is calculated from the time at present, not on the time the contact actually first appeared.
So, if you see a contact show up do the plotting at that time based on the ghost's projection, but after this the projection should be ignored as it's no longer valid.
Now the map contacts after they first appear will then begin to fade over time, so dont rely on the ghost icon shown off an older somewhat faded contact. Only rely on this if you know the contact just now showed up right then at that momment.

[Westbroek]

Ah, that explains it.
PS done and done, map contacts off.

[SabreHawk]

Which is one reason why I'd love it if there was a time stamp on the contacts like in SH3, then I know when any contact first appeared and can project where that ship likely is at present time based on that.

As it is right now, I keep a very sharp eye on the map as im TC'ing anywhere and if a contact shows up I quickly stop TC and note the time on a notepad, and put a marker there and also note the number of that marker on my notepad along side the time.
This way I know, but of course there will be those contacts that show up and you dont notice it till later, and so best to simply ignore it as you have no way to calculate anything from it since you dont know what time it showed up.