View Single Post
Old 10-10-2020, 11:25 AM   #51
Silent Hunter
Join Date: Dec 2004
Location: AN9771
Posts: 4,782
Downloads: 283
Uploads: 0


Originally Posted by Captain Prise View Post
neat app but how does the clock work? could anyone help me? thanks
Be stopped, or only move forward while the periscope is pointing forward or aft and you are turned facing or away from the target.

Start the clock when the target starts crossing the line with it's bow.
Stop the clock when it leaves the line with the stern.

Look at the scales which are closest to the length of the target:
The needle crosses the scale where that length of target would have that speed. On the other length scale it would have a different speed. If your target has a speed somewhere in between you need to adjust the result to best reflect it.

If it has length 125m, then take the average of the crossing points on the 100m and 150m scale.

If it has length 110m, then take the difference in speeds indicated on both scales, divide by 5 (or shift the decimal to the left and multiply by 2), then add that to the speed indicated on the lower length scale.

It's not as useful if you want precision. But it indicates a quick ballpark.

Using the calculator side of the attackdisk can be much more straight forward quickly. Align target length on the yellowish distance scale with the time in seconds on the white time disk. Pointer on the time disk points to speed in knots on the yellowish speed scale (in the middle of it).
Pisces is offline   Reply With Quote