WHY the angle of bow?????

Thanks to many youtube videos I understand HOW to calculate the angle of bow

But nobody taught me WHY I need to know the angle of bow. Sure, it has to do with the firing of the torpedo, but WHAT is the relationship between the firing of the torpedo and the angle of bow? Would someone please explain this to me, if possible, in "plain" English without abbreviations?

[razark]

You need to know where the ship is going, so you will know where to put the torpedo so that both the ship and torpedo are at that point at the same time. If you know where the target is relative to you and how fast it is moving, you can make a triangle, one leg being the sight line to the target, one being the torpedo travel, and the final being the target's course.



Angle on the bow is just a way of relating the target's course to your position.

[KaleunMarco]

Originally Posted by razark

You need to know where the ship is going, so you will know where to put the torpedo so that both the ship and torpedo are at that point at the same time. If you know where the target is relative to you and how fast it is moving, you can make a triangle, one leg being the sight line to the target, one being the torpedo travel, and the final being the target's course.



Angle on the bow is just a way of relating the target's course to your position.

well put.

AOB is especially needed for unguided munitions as you need to put the munition in the path of the target in order for it (the munition) to have maximum effectiveness. this became abundantly important during the Pacific submarine theatre when US skippers determined by hard experience that they had more success when shooting from certain angles.

good luck!

[Ataraxzy]

Here's another explanation that might be of assistance.

It's a geometry problem. You're trying to find all the interior angles and leg lengths of a triangle, known as 'solving' it.

Triangles have 3 interior angles and 3 legs, and with any combination of 3 out of those 6 pieces of information, you can figure out the other 3 and fully solve the triangle.

By using your stadimeter you know the distance from your boat to the ship. That's one leg of the triangle.

By looking at the bearing to the target, you know the angle between the line pointing directly out of your bow and the line from the prow of your boat to the ship.

You've got two pieces of information, NICE!

There are 4 pieces of information left to discover, 2 legs and 2 angles:


1. The length of the two legs that intersect ahead of you, the meeting point between your straightline travel and the ship's straightline travel.

2. The angle created by those two legs, and finally,

3. The angle from the ship's bow to YOUR bow, AKA AoB (I like to make sure to always call it Angle off the Target's Bow to remember)

Here's the thing, 1. and 2., above depend entirely on two more things: the ship's speed and the speed of your torpedoes, GREATLY complicating the calculations of those three pieces of information. That's a calculus problem involving finding the minimum value of a system of equations. Possible, but a pain in the butt. Let a computer do that for you.

AoB, on the other hand, is pretty easy. So, you grab THAT, and BOOM, you have the three necessary pieces to solve the triangle. Plug them into the TDC (where the C stands for Computer) and the TDC figures the two missing legs and the missing angle out for you, and it does it continuously, allowing you to fire pretty much whenever you want to (within limits, for example, impact torpedoes REALLY don't like sharp angles of impact, the closer to 90deg you can get an impact torpedo to hit, the happier it is)

So there you go! The reason you need to find AoB is because it's the easiest of the 4 remaining things to find to solve the triangle after you've determined one leg and one angle.


Edit:

To solve the calculus problem, you need two additional pieces of information as stated above: the speed of the ship and the speed of your torpedo.

So, to completely fill out a TDC, you need all of the following:

1. Target's distance (Leg 1)
2. Target's bearing (Angle 1)
3. Your bearing from the target (Angle 2: Angle on bow)
4. Target's speed (Calculus 1)
5. Torpedo's speed (Calculus 2)
6. Target's depth of keel (Independent variable)


So, your procedure should be something like this:

1. Identify the ship. This gives you 6 immediately.
2. Use the stadimeter to determine range. Plug that into your TDC.
3. Determine bearing to target. Plug that into your TDC.
4. Determine your bearing from target (AoB). Plug that into your TDC.
5. Determine speed of target. Plug that into your TDC.
NOTE: So far, there's no real 'choice' involved here, except for method used to determine what the values of the above variables are. The next steps all depend on what torpedo you're going to use to attack the target.


6. Determine torpedo(s) to be used and their trigger types.
7. Set depth according to type and weather/sea conditions. Plug that into your TDC.

a. Magnetic detonators don't hit the ship, they go under the ship, so set them a meter or two LOWER than the keel.
b. Impact detonators do hit the ship, so set them a couple of meters HIGHER than the keel.
c. Choppy seas really affect impact detonators badly, so in bad weather, use magnetic detonators. A torpedo that breaches the water because the wave troughs are deeper than the torpedo's depth setting could impact the following wave and detonate, because the impact was hard enough for it to think it was the hull of a ship. Even if it doesn't actually breach, the jostling can do it anyway.


8. Set torpedo speed for variable speed torpedoes. Enter that into your TDC.
This setting will depend on the distance between the ship and your boat. The relationship between a torpedo's available fuel and its speed is nonlinear: the faster you go, the higher the rate of fuel usage. So, twice the speed is less than half the range of a slower speed, and half as slow is longer than twice the range of a higher speed.

That's it. When you're ready to fire, open the tubes and LOS!