SUBSIM Radio Room Forums - View Single Post - (Yet another) Attempt to make sense of gyro angles

Von Due · 03-01-17, 04:52 PM

Test procedure and results so far:

I mark on the map a representation of the periscope.

Due north of this mark, 135-136 meters north I mark the advance line for a 90* gyro angle. This line is extended west and east so that it intersects the 87.4* and 272.6* marks at the 3000 meters circle on Pato's bearing tool.

I fired torpedos at slow speed setting with 90* turns and timed when the torpedo reached each of the 100 meter marks out to 3000 meters.

Plotting the range from periscope vs time, I did a linear regression and found the expressions for torpedo run time for 30kts, 40 kts and 44 kts for distances between 200 and 3000 meters from the periscope.

t(30) = 0.06543472906*R + 1.683743842
t(40) = 0.0490760468*R + 1.262807882
t(44) = 0.044614588*R + 1.148007165

These regressions had an r^2 apprx = 0.9999 which is very good. Still it should be mentioned that the times can be off by apprx 1 second but for targets 70 meters long, 1 second is within limits even for target speeds of 12 kts.

I then drew a line L from the periscope mark to the advance line and used the distance from the periscope in the above equations to find run time. I noted down the true bearing of this line.

Set target speed to zero in the TDC, and adjusted the range until the attack map displayed the time I calculated while keeping the gyro angle locked at 90*, the actual periscope bearing now matched the measured true bearing of L

I calculated how far the target would travel at 8 kts before reaching the intercept point and drew the target course line for this calculated distance, to find the aim point.

Now I drew the lead angle line from the perscope to the aim point and measured the true bearing to get the lead angle bearing for the periscope.

This bearing did NOT match the TDC suggestion. The two disagreed by several degrees.

I will attempt these manual plots for 90* shots and see if they will give me consistent results.
After setting distance and gyro angle, I will disengage the auto update and set the perscope to the measured bearings.

03-01-17, 04:52 PM	#33
Von Due Sea Lord Join Date: Jul 2012 Posts: 1,691 Downloads: 30 Uploads: 0	Test procedure and results so far: I mark on the map a representation of the periscope. Due north of this mark, 135-136 meters north I mark the advance line for a 90* gyro angle. This line is extended west and east so that it intersects the 87.4* and 272.6* marks at the 3000 meters circle on Pato's bearing tool. I fired torpedos at slow speed setting with 90* turns and timed when the torpedo reached each of the 100 meter marks out to 3000 meters. Plotting the range from periscope vs time, I did a linear regression and found the expressions for torpedo run time for 30kts, 40 kts and 44 kts for distances between 200 and 3000 meters from the periscope. t(30) = 0.06543472906R + 1.683743842 t(40) = 0.0490760468R + 1.262807882 t(44) = 0.044614588R + 1.148007165 These regressions had an r^2 apprx = 0.9999 which is very good. Still it should be mentioned that the times can be off by apprx 1 second but for targets 70 meters long, 1 second is within limits even for target speeds of 12 kts. I then drew a line L from the periscope mark to the advance line and used the distance from the periscope in the above equations to find run time. I noted down the true bearing of this line. Set target speed to zero in the TDC, and adjusted the range until the attack map displayed the time I calculated while keeping the gyro angle locked at 90, the actual periscope bearing now matched the measured true bearing of L I calculated how far the target would travel at 8 kts before reaching the intercept point and drew the target course line for this calculated distance, to find the aim point. Now I drew the lead angle line from the perscope to the aim point and measured the true bearing to get the lead angle bearing for the periscope. This bearing did NOT match the TDC suggestion. The two disagreed by several degrees. I will attempt these manual plots for 90* shots and see if they will give me consistent results. After setting distance and gyro angle, I will disengage the auto update and set the perscope to the measured bearings. Last edited by Von Due; 03-01-17 at 05:04 PM.