Free Navigation VS Map Path - Fuel Efficiency

CptGlub · 04-03-17, 12:49 PM

Was just wondering...Does the sub have to make many very small course corrections to stay on the waypoint nav path? If so, does this impact fuel efficiency? Would it be better mileage to draw out some nav paths with the ruler and navigate freely using the compass and rudder? No big deal, was sort of daydreaming on a long haul and the thought hit me.

Zero Niner · 04-03-17, 09:35 PM

In game? Probably not. Don't think effects of weather & environment are modeled, beyond the basics (e.g. night/day; visibility).

IRL? Probably. A sub's course will deviate from what's been plotted to environmental factors like ocean currents which will push the sub off-course.

BigWalleye · 04-04-17, 08:09 AM

It certainly wouldn't be very hard to try it out. I'm sure lots of people would be interested in your results. Fuel efficiency is always a concern. Why don't you check it out?

CptGlub · 04-09-17, 10:31 AM

Tests Complete

Conclusion:
There is no difference in fuel efficiency between auto-following a plotted course and navigating freely by compass.

Details:
s-boat
start point 30nm west of Fremantle
23% fuel
surface run (batteries at 100%)
standard speed (10kts)
time acceleration 1024 (see exceptions below)

First test:
Heading due west
Following plot - 1843.7nm
without plot - 1843.6nm

Second test:
Heading NW
Following plot - 1843.3nm
without plot - 1843.3nm

Time acceleration was interupted twice at 10 and 4 percent fuel by messages from the crew. Bumped back up to 1024 asap. When fuel was down to 1 percent, time accel was taken to 512 so I could catch the very end of the run.

Something interesting I learned was that zero fuel isn't really zero fuel. There is still just under one percent to go. So the next time you're cruising in to Fremantle on vapors and thinking about asking the men to piss in the fuel tank, keep in mind that when you hit zero on the guage, you've still got some juice left.

Here is something interesting that I discovered. During my test, I noticed that the plotted sub deviated from a line drawn by the ruler tool. To check this out, I did the following.

Turned sub to heading 315. Using the ruler and tool helper, I drew a line from the sub out 1843nm at a NW heading of 315. Then I used the "plot course" tool, zoomed all the way in to the end of the rulered line and dropped the end point of the plot line onto the little "x" at the end of the ruled line. As the sub advanced, it strayed port of the ruler line. At the 1/2 mark the sub was 6.6nm port of the ruled line. At 2/3 the distance, sub was port by 8.4nm. 3/4 distance, variance was 8.1nm. But then it started to close and by the time the sub got to the end of the plot line, he was back on the ruled line.
No big deal because we are only talking 8nm on a disatnce of 1800+nm but it is still interesting that one or both of those supposed straight lines are not truly straight.

Go figure.

END OF REPORT!

propbeanie · 04-09-17, 12:19 PM

Now, are they modeling the curve of the Earth with that, or the ocean currents, or the crew's plotting error?...

I vote for all of the above.

04-03-17, 12:49 PM	#1
CptGlub Mate Join Date: Oct 2011 Posts: 59 Downloads: 76 Uploads: 0	Free Navigation VS Map Path - Fuel Efficiency Was just wondering...Does the sub have to make many very small course corrections to stay on the waypoint nav path? If so, does this impact fuel efficiency? Would it be better mileage to draw out some nav paths with the ruler and navigate freely using the compass and rudder? No big deal, was sort of daydreaming on a long haul and the thought hit me.

04-09-17, 12:19 PM	#5
propbeanie CTD - it's not just a job Join Date: May 2016 Location: One hour from Music City USA! Posts: 9,761 Downloads: 441 Uploads: 2	Now, are they modeling the curve of the Earth with that, or the ocean currents, or the crew's plotting error?... I vote for all of the above. __________________ "...and bollocks to the naysayer/s" - Jimbuna

04-03-17, 09:35 PM	#2
Zero Niner Ace of the Deep Join Date: Apr 2005 Posts: 1,032 Downloads: 69 Uploads: 0	In game? Probably not. Don't think effects of weather & environment are modeled, beyond the basics (e.g. night/day; visibility). IRL? Probably. A sub's course will deviate from what's been plotted to environmental factors like ocean currents which will push the sub off-course.

04-04-17, 08:09 AM	#3
BigWalleye Sea Lord Join Date: Jul 2012 Location: On the Eye-lond, mon! Posts: 1,987 Downloads: 465 Uploads: 0	It certainly wouldn't be very hard to try it out. I'm sure lots of people would be interested in your results. Fuel efficiency is always a concern. Why don't you check it out?

04-09-17, 10:31 AM	#4
CptGlub Mate Join Date: Oct 2011 Posts: 59 Downloads: 76 Uploads: 0	Tests Complete Conclusion: There is no difference in fuel efficiency between auto-following a plotted course and navigating freely by compass. Details: s-boat start point 30nm west of Fremantle 23% fuel surface run (batteries at 100%) standard speed (10kts) time acceleration 1024 (see exceptions below) First test: Heading due west Following plot - 1843.7nm without plot - 1843.6nm Second test: Heading NW Following plot - 1843.3nm without plot - 1843.3nm Time acceleration was interupted twice at 10 and 4 percent fuel by messages from the crew. Bumped back up to 1024 asap. When fuel was down to 1 percent, time accel was taken to 512 so I could catch the very end of the run. Something interesting I learned was that zero fuel isn't really zero fuel. There is still just under one percent to go. So the next time you're cruising in to Fremantle on vapors and thinking about asking the men to piss in the fuel tank, keep in mind that when you hit zero on the guage, you've still got some juice left. Here is something interesting that I discovered. During my test, I noticed that the plotted sub deviated from a line drawn by the ruler tool. To check this out, I did the following. Turned sub to heading 315. Using the ruler and tool helper, I drew a line from the sub out 1843nm at a NW heading of 315. Then I used the "plot course" tool, zoomed all the way in to the end of the rulered line and dropped the end point of the plot line onto the little "x" at the end of the ruled line. As the sub advanced, it strayed port of the ruler line. At the 1/2 mark the sub was 6.6nm port of the ruled line. At 2/3 the distance, sub was port by 8.4nm. 3/4 distance, variance was 8.1nm. But then it started to close and by the time the sub got to the end of the plot line, he was back on the ruled line. No big deal because we are only talking 8nm on a disatnce of 1800+nm but it is still interesting that one or both of those supposed straight lines are not truly straight. Go figure. END OF REPORT!