Old fashion method for determining SPEED

[don1reed]

1. Get on a Collision course with the Target.
Constant bearing plus closing Range = Collision Course.
Adjust your own course and/or speed.

2. Formula: Own Speed : Sin Target AoB : : Target Speed : Sin Target Bearing
3. If you have a sliderule hidden in the desk drawer, dust it off, this method is extreme fast.

Here are two views, one is of a regular sliderule, and the second is a circular sliderule. The logrithmic characteristic and function of sliderules makes this an easy problem. (apologies for the bit of blurriness)



Here's the same thing with a sliderule that I made from heavy card stock and covered in clear plastic at Kinko's used with the original Silent Hunter.

One side is sliderule the other is whiz-wheel.



Here's a pic of a rare WWII Uboat whiz-wheel