Introduction:
These rules are designed to speed up surface ship and submarine torpedo attack resolution for large-scale CaS games. While it allows faster game play, there is a cost in accuracy. This model uses the same 3-minute Tactical Turn as CaS, but eliminates the intercept angle calculation, the movement of the torpedo counter, and target aspect determination during the actual attack.
These are draft rules, not an official change, and we would like players to use these and tell us whether or not they like them or not.
Procedure:
During the Plotting Phase, the firing player designates the target to be attacked and the number of torpedoes to be launched. The number of torpedoes in a single salvo depends on the number of launch tubes on a particular mount. A single salvo can have a maximum of six torpedoes, although for most ships the number of torpedoes in a single salvo will be three, four or five. The player places a torpedo datum counter by his ship to mark a torpedo launch during the Planned Fire Phase. The player being attacked can immediately attempt to detect the launch, provided he has ships within range. The torpedoes will begin their movement in the next Tactical Turn. This much is as prescribed in the standard CaS rules. The only change is that the datum marker should show the turn of launch.
As the torpedoes speed to their intended target, it may be necessary to check to see if they intercept a ship along the way. This check is done in the Movement Phase. The players create a "Torpedo Attack Box," whose size is based on the length of the weapons' run. The length of the box is the last half of the torpedo's movement. Its width is taken from the following table, based on the length of the run, measured from the datum marker to the torpedo's present position:
Torpedo Box Width
0-5,000 yds 500 yds
5,001-10,000 yds 1,000 yds
10,000+ yds 2,000 yds
Example: A 45-knot torpedo that has moved for two turns has covered 9000 yards. The box is 1000 yards wide, centered on the torpedo's track, and is 2250 yards long (half of 4500 yards) If there is more than one target in the box, resolve the attacks one at a time, beginning with the ship closest to the launch datum counter. Any torpedoes that miss the first target will be able to attack ships further away. Once a torpedo salvo reaches a ship, targeted or accidental, measure the torpedo run from the launch datum counter to the target's position. Find out the base chance of a hit by cross-referencing the torpedo run with the size class of the target.
For multiple torpedo salvos, there is a Salvo Modifier for each additional torpedo up to a maximum of six. This modifier is also range- and size class-dependent. Multiply the Salvo Modifier by the number of torpedoes in the salvo minus one and add this to the base chance to hit. The maximum modified chance of a hit is 0.90.
Example: A size class "A" battleship is attacked by a four-weapon salvo after a torpedo run of 4,500 yards. The base chance of a hit is 0.19 for a Size Class A target after a torpedo run of 4,100 to 5,000 yards. The salvo modifier is +0.10 for each additional torpedo over one. Base Ph = 0.19 Salvo Modifier = .10 x (4-1) = 0.30 Modified Ph = 0.49 If the torpedo attack was detected and the ship was able to change course by at least 45°, it is considered to be evading. The evasion modifier reduces the probability of hit by -0.30. Speed also plays an important, but less critical role. The model assumes that the target ship is traveling at a speed of 16 to 30 knots. Anything outside this speed range has a modifier since the target is now either easier or harder to hit.
Example: The battleship above visually detected the launch of the torpedoes and was able to change course by 90°. Ship's speed is 33 knots. Evasion Mod = -0.30 Speed Mod = -0.10 Final Ph = 0.49 - 0.40 = 0.09 In a multiple-weapon salvo, there is a chance of more than one torpedo hitting the target. Once the final Ph has been calculated, the attacking player rolls D100 to see if he hits the target. Multiple hits occur if the die roll is less than or equal to the final Ph minus the multiple hit value.
Example: In the first example, the total Ph was 0.49 which represents a non-evading target doing between 16 and 30 knots. To see how many hits are possible, take the Ph and subtract the multiple hit value for a size class A target. 1 Hit = 0.49 2 Hits = 0.49 - 0.40 = 0.09 3 Hits = 0.49 - 0.70 = -0.21 No chance for three or more hits. In some circumstances, it is possible that the final modified Ph will be greater than 1.00. While the maximum allowed Ph for a single hit never exceeds 0.90 for any one torpedo, when seeing if multiple weapons have hit the target use the actual final Ph value - even if it is greater than 1.00.
Example: A daring Asashio-class DD manages to get within 2,000 yards of USS Maryland and fires two salvos of four Type 93 Long Lance torpedoes. Because of a thick smoke screen, Maryland doesn't detect the torpedoes in time to evade and continues on a steady course at 23 knots. The torpedoes intercept Maryland after a run of 900 yards. Base Ph = 0.80 (Size class A and a torpedo run between 0.5 - 1.0 kyds) Salvo Mod = 0.10 x (4-1) = +0.30 (Size class A and a torpedo run between 0.5 - 5.0 kyds) Speed Mod = 0.0 (Target speed of 23 knots) Evasion Mod = 0.0 (Target has not met Evasion criterion) Final Ph = 0.80 + 0.30 = 1.10
| Torpedo | Hits | Probability of Hit |
| 1 | 0.90 | (1.10) |
| 2 | 0.70 | (1.10 - 0.4) |
| 3 | 0.40 | (1.10 - 0.7) |
| 4 | 0.20 | (1.10 - 0.9) |
Model Assumptions:
Turn Length = 3 minutes (Standard CaS Tactical Turn).
Aspect independent. Quarter aspect for all targets was used in Base Ph.
Target speed is between 16 and 30 knots for Base Ph purposes.
Speed modifiers taken from CaS Aerial Torpedo Attack Table.
Evasion based more on aspect change than completely avoiding the spread.
Probability of hit is primarily dependent on torpedo run, followed by target size and the number of weapons in the salvo. (Based on CaS Torpedo CRTs)
Model Advantages:
The major advantage with this method is that it significantly reduces the time to resolve torpedo attacks.
1) Removes the requirement to calculate an intercept course along with the need to measure target angle on the bow carefully.
2) Players no longer have to move torpedo counters on the playing surface. This is probably the single most time-consuming part of the tactical-level torpedo attack model in CaS. It is especially advantageous as Proportional Movement is not used which can really slow down game play.
3) Target aspect doesn't have to be determined when the torpedo attack is resolved.
Torpedo attacks will be a little more covert without counters on the playing surface.
Model Disadvantages:
Model accuracy is decreased. This is not so much of a problem with one to three weapons hitting out of a salvo, but four or more hits start to deviate from the CaS Torpedo CRTs
The simplified torpedo attack model has more room to be "gamed" as it has distinct boundaries where performance can vary considerably.
[Ed: Please try these rules out and let us know how they work for you.]
Simplified CaS Torpedo Attack Tables
| Base Probability of Hit | ||||
|---|---|---|---|---|
| Torpedo Run (kyds) | Size Class A | Size Class B | Size Class C&D | Size Class E |
| 0.5 - 1.0 | 0.80 | 0.56 | 0.33 | 0.18 |
| 1.1 - 2.0 | 0.55 | 0.30 | 0.16 | 0.10 |
| 2.1 - 3.0 | 0.32 | 0.17 | 0.08 | 0.06 |
| 3.1 - 4.0 | 0.23 | 0.14 | 0.06 | 0.04 |
| 4.1 - 5.0 | 0.19 | 0.09 | 0.05 | 0.03 |
| 5.1 - 6.0 | 0.16 | 0.08 | 0.04 | 0.03 |
| 6.1 - 7.0 | 0.13 | 0.07 | 0.04 | 0.02 |
| 7.1 - 8.0 | 0.12 | 0.06 | 0.03 | 0.02 |
| 8.1 - 9.0 | 0.11 | 0.05 | 0.03 | 0.02 |
| 9.1 - 10.0 | 0.10 | 0.05 | 0.03 | 0.01 |
| 10.1 - 12.0 | 0.09 | 0.04 | 0.02 | 0.01 |
| 12.1 - 14.0 | 0.08 | 0.03 | 0.02 | - |
| 14.1 - 16.0 | 0.07 | 0.03 | 0.01 | - |
| 16.1 - 18.0 | 0.06 | 0.02 | - | - |
| 18.1 - 20.0 | 0.05 | 0.01 | - | - |
| 20.1 - 24.0 | 0.04 | - | - | - |
| 24.1 - 28.0 | 0.03 | - | - | - |
| 28.1 - 32.0 | 0.02 | - | - | - |
| 32.1 - 36.0 | 0.01 | - | - | - |
| Torpedo Salvo Size Modifier (per each additional torpedo) | ||||
|---|---|---|---|---|
| Torpedo Run (kyds) | Size Class A | Size Class B | Size Class C&D | Size Class E |
| 0.5 - 5.0 | 0.10 | 0.09 | 0.06 | 0.04 |
| 5.1 - 10.0 | 0.07 | 0.05 | 0.03 | 0.02 |
| 10.1 - 15.0 | 0.03 | 0.02 | 0.01 | 0.01 |
| 15.1 - 20.0 | 0.01 | 0.01 | 0.00 | 0.00 |
| 21.1 - 36.0 | 0.00 | 0.00 | 0.00 | 0.00 |
| Speed & Evasion Modifiers | |
|---|---|
| Target Speed | Modifier |
| 0 - 5 knots | 0.20 |
| 6 - 15 knots | 0.10 |
| 16 - 30 knots | 0.00 |
| 31+ knots | -0.10 |
| Target Evades | -0.30 |
| Multiple Torpedo Hits in a Salvo | ||
|---|---|---|
| # of Hits | Size Class A/B | Size Class C/D/E |
| 2 Hits | -0.40 | -0.50 |
| 3 Hits | -0.70 | -0.60 |
| 4 Hits | -0.90 | -0.70 |
| 5 Hits | -1.00 | -0.80 |
| 6 Hits | -1.10 | -0.90 |
BT
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© Copyright 1998 by Larry Bond and Clash of Arms.
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