SUBSIM Radio Room Forums - View Single Post

Frederf · 09-07-09, 12:40 AM

You know I've been looking at the graph I posted and even half-arse using it in SH4 for a while now but I've always put off applying some greygoo power to it until you splattered against it first.

When I saw deflection angle on the plate I remembered it was back in that previous diagram in the same document about the angle between the periscope and pseudo-winkler-bajoob or something and never bothered to look it up. It turns out the deflection angle is more or less what we've been used to thinking of as the "shoot lead angle" or the angle between the direction to the target visually at the moment of firing and the direction of torpedo travel.

Oddly enough I've been using the concept of "optimal track angle" for ages in Silent Hunter but in a totally different context. I never thought of it as the most error-tolerant or the least rate of change of deflection angle but simply the best chance to hit another ship in a convoy row if I missed the first target.

If you try to hit a convoy target squarely and miss astern there's no chance to hit his neighbor traveling abreast of him. So instead of perfectly abreast of a convoy row I'll skew the shot (or spread) several degrees beyond 90° impact then a miss of the first can hit the second or even third. The improvement in hit percentages is very noticeable! For example if the convoy is going 10 kts I would shoot at a torpedo track angle of ( ArcTan (10/46 ) = 12.3°) 90 + 12.3 = 112.3°.

I had the suspicion but never a firm understanding that when firing in this way not only was I increasing my chances of hitting a 2nd or 3rd target I was actually increasing my chances of hitting the 1st or single target.

Let's check this method vs. the plate and see if they agree.

D'OH WRONG: TORPEDO TRAVELS ALONG THE HYPOTENUSE

Code:

ArcTan(8/46)+90° = 99.9°
ArcTan(12/46)+90° = 104.6°
ArcTan(16/46)+90° = 109.2°
ArcTan(20/46)+90° = 113.5°
ArcTan(24/46)+90° = 117.6°

What's with me and Tangent vs Sine lately?

BETTER

Code:

ArcSin(8/46)+90° = 100.0°
ArcSin(12/46)+90° = 105.1°
ArcSin(16/46)+90° = 110.4°
ArcSin(20/46)+90° = 115.8°
ArcSin(24/46)+90° = 121.4°

Plate
8kts: 102
12kts: 108
16kts: 111
20kts: 118
24kts: 122

Hmm I was hoping those would come out closer. It's probably just a coincidence that these values are close.

I think of it this way: If you know the enemy's course very, very exactly and know the enemy's speed very, very poorly my best shot is against the target's bow or stern to rule out errors in speed. However if you know the speed very well and the course not so well it's better to shoot into his sides as his ( angular speed ) x ( target angular width) is not so strongly tied to his AoB the closer you get to 90°/270° AoB. Somewhere between these two extremes must be a balance for an equal uncertainty both with speed and course.

This of course all goes out the window because with these darn faulty impact pistols I am habitually shooting from 50-60° torpedo track angle or 120-130° to avoid the square-shot pistol jam dud-amabobber!

09-07-09, 12:40 AM	#100
Frederf Seasoned Skipper Join Date: Apr 2005 Posts: 665 Downloads: 79 Uploads: 1	You know I've been looking at the graph I posted and even half-arse using it in SH4 for a while now but I've always put off applying some greygoo power to it until you splattered against it first. When I saw deflection angle on the plate I remembered it was back in that previous diagram in the same document about the angle between the periscope and pseudo-winkler-bajoob or something and never bothered to look it up. It turns out the deflection angle is more or less what we've been used to thinking of as the "shoot lead angle" or the angle between the direction to the target visually at the moment of firing and the direction of torpedo travel. Oddly enough I've been using the concept of "optimal track angle" for ages in Silent Hunter but in a totally different context. I never thought of it as the most error-tolerant or the least rate of change of deflection angle but simply the best chance to hit another ship in a convoy row if I missed the first target. If you try to hit a convoy target squarely and miss astern there's no chance to hit his neighbor traveling abreast of him. So instead of perfectly abreast of a convoy row I'll skew the shot (or spread) several degrees beyond 90° impact then a miss of the first can hit the second or even third. The improvement in hit percentages is very noticeable! For example if the convoy is going 10 kts I would shoot at a torpedo track angle of ( ArcTan (10/46 ) = 12.3°) 90 + 12.3 = 112.3°. I had the suspicion but never a firm understanding that when firing in this way not only was I increasing my chances of hitting a 2nd or 3rd target I was actually increasing my chances of hitting the 1st or single target. Let's check this method vs. the plate and see if they agree. D'OH WRONG: TORPEDO TRAVELS ALONG THE HYPOTENUSE Code: ArcTan(8/46)+90° = 99.9° ArcTan(12/46)+90° = 104.6° ArcTan(16/46)+90° = 109.2° ArcTan(20/46)+90° = 113.5° ArcTan(24/46)+90° = 117.6° What's with me and Tangent vs Sine lately? BETTER Code: ArcSin(8/46)+90° = 100.0° ArcSin(12/46)+90° = 105.1° ArcSin(16/46)+90° = 110.4° ArcSin(20/46)+90° = 115.8° ArcSin(24/46)+90° = 121.4° Plate 8kts: 102 12kts: 108 16kts: 111 20kts: 118 24kts: 122 Hmm I was hoping those would come out closer. It's probably just a coincidence that these values are close. I think of it this way: If you know the enemy's course very, very exactly and know the enemy's speed very, very poorly my best shot is against the target's bow or stern to rule out errors in speed. However if you know the speed very well and the course not so well it's better to shoot into his sides as his ( angular speed ) x ( target angular width) is not so strongly tied to his AoB the closer you get to 90°/270° AoB. Somewhere between these two extremes must be a balance for an equal uncertainty both with speed and course. This of course all goes out the window because with these darn faulty impact pistols I am habitually shooting from 50-60° torpedo track angle or 120-130° to avoid the square-shot pistol jam dud-amabobber!