Quote of the Day
A torpedo?...You don't really know what you're askin'. You see, there ain't nothin' so complicated as the inside of a torpedo. It's got gyroscopes, compressed air chambers, compensating cylinders...
— From the movie The African Queen. Charlie is answering Rose's question "Could you make a torpedo?" As an old torpedo engineer, I appreciate that answer.
I read quite a bit of World War 1 (WW1) and World War 2 (WW2) naval history. Recently, I have tried to specialize my readings to torpedo launch platforms. I have seen scant little on torpedo fire control on PT boats during WW2 (Figure 1). While doing some history-related searches on Youtube, I discovered this video (Figure 2) that does an excellent job of showing how torpedoes were launched from PT boats – start watching at 30:45 minutes.
|Figure 2: Good Video Showing How PT Boats Launched Torpedoes.|
It is interesting that standard torpedo tubes (i.e., launch the torpedo with a black powder charge) were replaced with a simple cradle that dropped the torpedo off of the side of the boat (Figure 3).
WW2 PT boats generally carried four torpedoes when configured for anti-ship duty. A single torpedo sight was used to aim all four torpedoes. The torpedoes were launched when the PT boat had been steered in the direction you wanted the torpedoes to go. Attacks were normally made with multiple torpedoes that were launched with their gyro angles set to provide a slight spread off of the ship's course to help compensate for any errors and to provide a higher probability of a hit. Figure 4 shows how the torpedo gyro angles are used provide the required spread.
There are some excellent documents on how the torpedo fire control problem was solved using mechanical calculators. These mechanical calculators are very similar to those I discussed in this post on torpedo fire control during WW1.
- Torpedo Angle Solver Mark 7
- Mk8 Torpedo Angle Solver (Used on Submarines)
- General Torpedo Firing Procedures
- Manuals on Basic Fire Control Mechanisms
- Basic Torpedo Math
Figure 5 shows a typical torpedo director, which I think of as an analog trigonometry calculator.
The stationary arm of the director is mounted parallel to the centerline of the PT boat. The stationary arm is toward the top of Figure 5.
Figure 6 shows a photograph of a Torpedo Director Mark 31 for a PT boat.
Figure 7 shows the Torpedo Director Mark 31 on a PC boat.
In theory, a PT boat could accurately fire its torpedoes without a director by using the following procedure:
- set the PT boat speed equal to the torpedo speed.
- adjust the course of the PT boat so that the target maintains a constant bearing.
- launch when the target is within the operating range of the torpedoes; the closer the better.
- Steer away from the torpedo immediately after launch.
I read this procedure within a PT board document, but I do not recall where.