Can't estimate accurate range by RAOBF

[misha1967]

Originally Posted by Luken

Hello, I'm newbe and was playing tutorial about RAOBF to figure this out, and I have one simple question... What am I doing wrong??

To answer your question: You're not doing anything wrong, except you're not quite reading the RAOBF right.

If you look at the actual mast height (outer ring), you'll find that "41" is between the "40" tick and the next one, which is "42". So the result on the middle outer is actually 2050m.

I know, that's still not 1997.42m, but consider what you're using. The RAOBF is a device designed to give you a quick and adequate fix on a target, and getting within 50m on a target 2000m away isn't a bad result at all. Certainly good enough to start and even good enough to make a quick firing solution. At 2000m, you should probably think about salvo fire anyway. Again: This is trying to be realistic, it's a mechanical tool like a slide rule, not a GPS.

Also think about the one truly critical subjective observation you're using to determine the distance, which is the subjective height in graticules on the RAOBF. Yes, it certainly looks to be exactly 8, but how finely graded is that scale really? Also, is the target low in the water, bobbing on the water, is your baseline exactly at the waterline etc.

Here's another way to illustrate the historical limitations of the RAOBF: Reverse engineer a bit. What I mean is try it again, only this time rotate the inner middle (subjective height in "clicks" of mast) until the midpoint between "40" and "42" aligns perfectly with the "2000m" mark on the outer middle, since we have the luxury of knowing the exact distance to the target, which I'll round off to 2000m here since 2.5m really don't mean squat. See how little you have to change the subjective height (inner middle) to get that? If you'd looked at your RAOBF graticules and decided that the mast was about 8.2, for which there isn't an actual marking so you'd have to eyeball it, you'd be spot on? That's a perfect illustration of the built-in margins of human error.

All of those considerations are things you would have to compensate for in real life, which is what the RAOBF is simulating.

And still you get within 2.5% of the true distance to target. You've done pretty good for a "noob" if you ask me. Most real skippers would be proud to get within 5% at that distance. Aim amidships and you'd probably hit, but you've also learned why sub skippers were hesitant to fire at anything much farther than 1000m away.

So in this case, if it were in real life which is what we're trying to simulate here, you'd use that data to sketch up an initial firing solution in order to know where you'd need to be for the final shot and then, as the target closes, you'd make fresh readings and adjust, and each reading, because the distance would be less and less, would be more accurate.

That's how it worked in the real world and you're already off to a great start.

You've done good, "noob", just keep in mind that every tool here is based on what was available at the time, with all of the inaccuracies included.

Final piece of personal advice: Use the Stadimeter for distance. It's historically accurate and is much more precise and easy to use (at least in my opinion). Then use that distance for the rest. A good range fix is the foundation upon which every firing solution is based, and the RAOBF will take care of the rest admirably.

Happy Hunting!