I don't know anything about the prop count mod, I'll have to look into that.
To continue - so far, we've used three timed bearings, a ruler and an estimated speed of 11 knots to determine our target's estimated range, and most importantly, his actual heading.
PART IV
Once we have our target's heading, we're going to do one of two things - if he is at long range or receding, we'll want to use his course to either close with him or plot a surface end-around to get in front of him.
If we deem that he is likely close enough to attack - and with the amount of error I think is possible in this method, we'll want him pretty close - we'll plot a parallel course at our best speed. We want to make sure that we're well ahead of our target as he's likely faster than us (we're estimating that he is, certainly) and we're going to need some time to move and collect the last of our data.
First, we also have to enter some more data here. Along the target's course, we're going to plot his expected position at 3 minute intervals.
Remember that we left the clock running after our initial three bearings, and this is why. We're going to plot where he's going to be in three minutes (at 11 knots, that's 1017.72 metres further along his heading than the last timed bearing we took from him). Then three minutes after that, another 1017.72 metres. Keep doing this until you've marked his expected positions for the next 12 minutes or so.
I suppose you could pick whatever time you want, work out the distance he'll have traveled, and plot it. I just use the three minute intervals because I already have the distance worked out.
I really don't know what amount of time would be appropriate here. The longer you go, the more error that will probably creep in. We'll say that we're going to get our target's real speed and range in 12 minutes.
PART V
In a minute. I hope I'm being clear here, I feel like I'm writing a book and I could explain this to anybody in 2 minutes face to face. :P
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