SUBSIM Radio Room Forums - [Video] stoianm video tutorials

Very instructive videos, congrats :up:
I find the 'Intercepting convoys' and the 'Multiplication Factor' very helpful, it can be used for best interception of *any* target that is further away.

For anyone interested, I have made my personal written version of this vid, it's complex stuff to write down, but once you get it you will never use a different method I think :)

Here it is:

----------------------------------------------------------

Fastest interception of a target
*************************

Let's say that the BDU has transmitted to you the position, heading and speed of a convoy, or: you already know this data of a target which is far away.

Question:
Which heading do you have to take at a set speed to intercept the target as fast as possible?

Lets see this question in a grafic:

- - - - - - - - - - - - - - - - - - - - - *A
- - - B*- - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - - -*C - - - - - - - - - -

You are at point C. A ship or convoy is moving from A to B and you know its speed.
The most secure method to intercept the target is to head perpendicular to the target's heading, you will never be wrong by doing so but this will most likely not be the fastest interception, you will arrive early and need to wait for the target, just imagine that point A is very far on the right and then you'll understand that there must be a better interception course more at the right of the perpendicular heading.

Now, you could do some guessing work and draw lines with the ruler and find out that if you head in a specific direction and speed for a specific time, then the target would have moved a specific distance along the AB heading and you can see if you are close enough. Then you eventually repeat the drawings to improve the solution, however, this is not a precise method to use and it will not avoid you to do some calculations either.
A good approximation method is done with the help of the...

Multiplication Factor Formula, or Multiplication Factor called MF.

MF = [(Distance between you and target) / 100] x 3.33

The procedure is as follows:

a)
You plot the heading line of your target and calculate the MF in your situation.
In your head, take 3 times the target distance, add one third of target distance, divide by 100.

b)
You multiply the target's speed with MF...

MF x (target speed) = MF1
No need to be accurate to the decimals, just make a good rounding. (2,86 = 3; 1,44 = 1 + 1/2 etc.)

You take this value and mark it on the target's heading line starting from target's initial position. (Mark 1).

c)
You multiply your desired interception speed with MF...

MF x (Your interception speed) = MF2

and you draw a circle from Mark 1 with a radius of MF2.
Now you take note and mark the intersection of the circle with your bearing to the target (Mark 2).

d)
With the protractor, You measure the angle at Mark 2 between the target's position and Mark 1.
This plotted angle is your solution and will tell you how much you have to deviate from the target's bearing and head to that course, this will be the exact interception course to intercept the target as fast as possible at that specific speed.
For better visualisation, you can draw the exact same angle at your ship position, the angle going from the bearing to the target towards the heading line, the angle amount being the same than the angle at Mark 2, all lines being parallel.

Final note:

This approximation method comes close to the exact calculation which would require a nasty sinus/cosinus math function with changing triangles to solve, and which would require too much time to be useful even with a calculator.

All this explanation above sounds very complex (especially the final point d), but try these steps more times and you find the procedure very easy, fast and accurate for intercepting far away targets. Once you get used to it you won't read here again...
This MF method will give the shortest ETA on target, so you will be able to modify your heading - or your speed - in order to meet the target at a specific time, for example at sunset or sunrise for best weapon usage and less chance to be detected. You will find it easy to make these corrections once you have plotted the initial drawings, especially because in the SH series you can adjust the circles and lines without re-plotting them from zero.

And finally, at the beginning I said: "Fastest interception of a target". Doesn't it remind you of something, he? Yes: a TORPEDO...
----------------------------------------------------------