Bearing change tables for speed

[derstosstrupp]

Originally Posted by Pisces

Derstosstrup, do you have templates for those slideruler disk for Auswanderungsverfahren and Ausdamphverfahren? I feel a creative urge coming up.

And once I figure them out, I might even redraw them in CAD software.

No problem I’ll see what I can track down.

[Pisces]

Ok, in the mean time I had another run through of your documents and the tvre.org site explanation of Auswanderung and Ausdamphverfahren. Seems very do-able to recreate these. However, is it me or does "Drawing 21. Rundschieber für Auswanderungsverfahren “B” [12]" have crooked scales? 170 hm distance with 2.5 degree bearing change should show 24 nm/h (according to conversion factor 6000/1852) instead of 23. When I compare different marks each takes another value for meters per nautical mile. Same goes for Drawing 22. Not to German standards if you ask me.

[derstosstrupp]

Originally Posted by Pisces

Ok, in the mean time I had another run through of your documents and the tvre.org site explanation of Auswanderung and Ausdamphverfahren. Seems very do-able to recreate these. However, is it me or does "Drawing 21. Rundschieber für Auswanderungsverfahren “B” [12]" have crooked scales? 170 hm distance with 2.5 degree bearing change should show 24 nm/h (according to conversion factor 6000/1852) instead of 23. When I compare different marks each takes another value for meters per nautical mile. Same goes for Drawing 22. Not to German standards if you ask me.

I agree. When I made my wheel used those images and I did notice that too, some results differed (albeit slightly) from the actual math. It must be an issue with the website creator’s scan. He appears to have had KM doctrine books in his possession and maybe the scan from the book was a bit distorted.

I suppose one could recalibrate the wheel, that’s beyond my capabilities at the moment!

Been using my excel file instead as my wheel needs some repair.

[Pisces]

At first I wondered if Germany adhered to a different nautical mile standard at that time. But there was a standard adopted in 1929 according to the wiki. And the other value for nm to km don't differ that much. So it's probably draftsman's error. I will just stick to the math formulas and make my own scales.

[derstosstrupp]

OK folks, another update to this file - I have added a tab for Ausdampfverfahren (method of calcing speed by achieving a constant bearing to target, then deriving target speed from own speed, that bearing, and AOB). I've been playing around with this method in WP while overtaking targets, and it works very well.

The long and short - While overtaking, pick a ship and a feature on that ship and adjust speed (use the 10 slower function on the EOT too!) so the bearing moves only a little, then fine-tune with course adjustments until the bearing line in the UZO stays on that spot on the ship over at least a couple minutes. Then, without moving the UZO:

1. Note the exact bearing per the TDC to the 10th of a degree.
2. Note exact own speed to the 10th of a knot.
3. Estimate the ship's AOB.

Input these values into the "Ausdampfen" tab and it will calc the target's speed.

Obviously the initial AOB estimate will likely be inaccurate - as the approach unfolds, you will be able to refine his course and thus will be able to "go back" and adjust the initial AOB (and thus the speed estimate) accordingly.

Please let me know if that doesn't make sense!

[Pisces]

I would say, being at parallel course initially, reduce speed first with the 10 slower option of the EOTs. Then turn in to fine adjust to constant bearing. Else you turn in with a larger angle and close too quickly.

[derstosstrupp]

Originally Posted by Pisces

I would say, being at parallel course initially, reduce speed first with the 10 slower option of the EOTs. Then turn in to fine adjust to constant bearing. Else you turn in with a larger angle and close too quickly.

I agree. I’ve been having success by first turning roughly parallel, dropping 1-2 EOT settings/10 slower until bearing barely moves, then fine-tuning course by turning 5-10 deg away at a time. You are right that the key is to reduce speed as much as you can to minimize the amount of course adjustments you do.

[derstosstrupp]

Alright folks, more updates to this file! See Bearing Change file in my sig, and simply click File - Download As - Excel to save a copy for yourself.

I have added the following:

1. A "how to use" tab detailing use from initial sighting to firing, step by step.

2. A Range Calculation section to tab 1 to compute range based on AOB, speed, bearing, and own speed. Purpose is to establish a plot by which to check initial estimates during overtaking.

3. An "attack disk" to tab 2 to allow the normal functionality of a hands-on one (derive AOB from course, and course from AOB, with the bonus of a lead angle generator for those diehards not wanting to use the TDC).

Those are the main changes, but please read through the How to Use tab for how all the pieces fit together. I have been spending time solo recently testing this out and it works.

[Elphaba]

Thanks for all your hard work!

[derstosstrupp]

Couple more updates to the Excel file tool in my sig:

1. Plot tab - Create a 15-min plot using ranges based on length and AOB (length is easier to measure at large distances). Fill in the section for the correponding observation as you go. The reason for keeping a record of previous observations is that, if and when you estimate a more-accurate AOB, you will need to go back and readjust the AOBs of the previous observations by the same amount, thus truing up your plot (because the ranges will change). This is what I ended up having to do in my "Day Full Engagement Video" between Parts I and II.

2. No TDC tab - Those of you familiar with the U-boat Commander's Handbook may remember that it has instructions on how to take shots in the case when the TDC is down. The handbook covers 4 types - the pure bow shot, the pure stern shot, the 45 deg angled shot, and the 90 deg angled shot. The scopes had trainable bearing rings at the top to assist in visualizing this, allowing the user to set the torpedo track (either 45 or 90 or the equivalent port bearings) as well as the lead angle. The tab "No TDC" replicates this, allowing you to designate the angled (or straight) shot desired, and computing attack course and lead angle. Simply turn Angle Tracking to Off, set the gyro angle by hand based on the angle of the shot, and set your scope to shoot bearing and wait for that sucker to cross the wire. The handbook limits the discussion of angled shots to 45 and 90 so as to not overcomplicate things, but with the magic of Excel formulas, any angle is readily possible. Win yourself bragging rights in the community if you get good at this method!