Anyone have a spread angle chart?

[looney]

How does the chart work anyway? What does it show??

Cause IMHO it should be a 3d diagram: Range, length of target, AOB.. or am I wrong?

[Sigurd]

Originally Posted by looney

How does the chart work anyway? What does it show??

Cause IMHO it should be a 3d diagram: Range, length of target, AOB.. or am I wrong?

I would think that would be correct. It probably wouldnt be too hard to figure out the formula to make the chart. I dont remember my Geometry or Trig very well, but it shouldn't be too hard to derive if you're math inclined.

[MarkShot]

The cell values are in feet, but the range is yards.

[Sigurd]

Ok, I just did a little work, and I think I managed to come up with something. It does involve Sines and inverse sines, so grab a calculator. I dont have the ability to check to see if this works, but here it goes:

Let:
l be the length of the target ship
d be the range to the ship
S be the spread angle
a be AoB

Then:
S = Sin ^-1 ((sin d * l)/d)

Sin^-1 is the inverse sin for those who arent aware. Should this formula work, a table could be easily generated. The only real requirement for this is that both 'l' and 'd' must be the same unit (i.e. meters).

[Abd_von_Mumit]

Originally Posted by Sigurd

Ok, I just did a little work, and I think I managed to come up with something. It does involve Sines and inverse sines, so grab a calculator. I dont have the ability to check to see if this works, but here it goes:

Let:
l be the length of the target ship
d be the range to the ship
S be the spread angle
a be AoB

Then:
S = Sin ^-1 ((sin d * l)/d)

Sin^-1 is the inverse sin for those who arent aware. Should this formula work, a table could be easily generated. The only real requirement for this is that both 'l' and 'd' must be the same unit (i.e. meters).

I don't think we need such a complicated formula. In fact preparing a sheet containing as much as 4 different variables would be too much. The chart itself would have to be really huge.

Instead we could prepare just two separate sheets, each of a tolerable seize, and also easier to use I think:
1. for finding relative length of the ship (variables: real length, AOB),
2. for calculating desired spread angle (variables: distance, spread angle).

Formulas for both the tables are:
L - length
S - distance,
A - spread angle,
AOB - AOB
The exact formulas would then be:
1. for finding relative ship length:

relative ship length = sin(AOB) L

2. for finding offset of torpedoes after a certain distance with a certain spread angle:

offset = 2 tg(A) S

These two formulas can be easily used in OpenOffice's Calc. Tangent function is: "=tan()" and sinus function is "=sin()".

[MarkShot]

So, how do most people set their spread setting?

Or do you just do it manually by:

(1) Shooting a different spots on the hull.

(2) Introducing a firing delay between launches.

[Abd_von_Mumit]

Noone knows what "most people" do. But I could tell you what I do.

I just set the spread angle on the TDC screen, usually 1-2 deg, 3 deg at most, never more than 2 torpedoes at once (even if I am to fire all of them, because of sudden bouyancy change problem). And I shoot. I always take I-III and II-IV pairs, as I believe this will shoot one torpedo per each side of the boat (steer and back).

[looney]

I normaly use the scope to c what is lenth of target in degrees (measure bearing at bow, than rapidly move to stern read bearing) and subtract 2 degrees.

[Abd_von_Mumit]

As Sigurd said, that's easy to prepare. I think much faster to make it anew than remake the US yards/feet version.
Could you place whole the US chart here, so that we see the min/max distance and max spread angle?

[Sigurd]

I forgot to mention, my formula is based on an assumed shot in which the gyro angle is 0. I'm not sure if gyro angle would have any bearing on the spread angle, but testing would be able to clear that up.