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ichso · 05-23-09, 05:46 AM

Thanks and you're welcome

__________________________________________

I researched a little bit as one issue still frequently struck me to be dealt with. And that is turning the boat and how much that will offset you from your current position.
I'm going to describe it here because it mainly deals with the paper bag issue and my first post here was already concerning that.

So, when I'm doing a approach on a target sometimes I want to or I am forced to use the stern tubes. When I think that I'm a decent position I will turn around but afterwards all following marks on the map would feel a bit out of place because I never really knew where my boat was after a 180° turn compared to my position before. So I did a little research to find a constant I can use in such a situation.

On starting a new patrol I made use of the realtime update map feature, that means the sub marker on the map

. I made the assumption that I'm at periscope depth, travelling at full speed. So around 7-8 knots in a Gato sub. This would be the usual setting when I'm doing a 180-turn during my approach.
I made a mark of my position right before hitting the rudder, set it hard port and started the stopwatch (just out of curiousity) and made additional markings when I reached a course 90° off my initial one and when I finally hit the 180° off the initial course.
Then I just measured how far and in which direction I've travelled during this time, and here is the outcome:

The red mark being the first one, then green, then blue. I deleted the pencil marks afterwards to make it more readable. My initial course was 10° and as you can see my new position was off by 400 yards in a direction ~80° off of the old course. It took about 3 minutes to make this turn.

So, if I ever have to make a 180° turn during an approach to use the tubes on the opposite, this would be how far I can estimate my new position without tracking it during the turn and while still wearing my bag.

Maybe somebody else is also concerned with this and gathered some useful information from this thread.

Happy sailing

05-23-09, 05:46 AM	#5
ichso Ace of the Deep Join Date: Jul 2005 Location: Germany's oldest city alive Posts: 1,066 Downloads: 57 Uploads: 0	Thanks and you're welcome __________________________________________ I researched a little bit as one issue still frequently struck me to be dealt with. And that is turning the boat and how much that will offset you from your current position. I'm going to describe it here because it mainly deals with the paper bag issue and my first post here was already concerning that. So, when I'm doing a approach on a target sometimes I want to or I am forced to use the stern tubes. When I think that I'm a decent position I will turn around but afterwards all following marks on the map would feel a bit out of place because I never really knew where my boat was after a 180° turn compared to my position before. So I did a little research to find a constant I can use in such a situation. On starting a new patrol I made use of the realtime update map feature, that means the sub marker on the map . I made the assumption that I'm at periscope depth, travelling at full speed. So around 7-8 knots in a Gato sub. This would be the usual setting when I'm doing a 180-turn during my approach. I made a mark of my position right before hitting the rudder, set it hard port and started the stopwatch (just out of curiousity) and made additional markings when I reached a course 90° off my initial one and when I finally hit the 180° off the initial course. Then I just measured how far and in which direction I've travelled during this time, and here is the outcome: The red mark being the first one, then green, then blue. I deleted the pencil marks afterwards to make it more readable. My initial course was 10° and as you can see my new position was off by 400 yards in a direction ~80° off of the old course. It took about 3 minutes to make this turn. So, if I ever have to make a 180° turn during an approach to use the tubes on the opposite, this would be how far I can estimate my new position without tracking it during the turn and while still wearing my bag. Maybe somebody else is also concerned with this and gathered some useful information from this thread. Happy sailing __________________ My Subskins: http://www.subsim.com/radioroom/showthread.php?t=164169