Please help with "fast 90 advanced" method

89 · 12-24-11, 03:18 PM

Merry Christmas dear subsimmers!

Could someone kindly help me? - I just do not get the "advanced fast 90" (Wazoo's term).
I plot my approach like he instructed, but I just can not understand at what bearing I should aim while waiting for the ship to come so I could press "fire".

I have found the required angle at intersection of perpendicular course and the u-boat course (24 degrees in my screenshots below), but I do not understand how this angle is to be used. Fire at 360-24? Does not make sense. Fire at 360+24=24? Does not make sense either. Please help!

Target's speed is 3knts, distance 1.7km. What do I enter into the TDC?

PS I've used search and could not come up with good answers- most people talk about "basic fast 90" which does not interest me

Mar01 · 12-24-11, 05:52 PM

That is not the angle to fire at, 360-24 is the bearing you will point the scope at, and then set the target's AoB to be 90 starboard. Then you set the TDC back to auto and just wait for the target to reach a bearing that makes the gyro angle as close to zero as you want, the TDC will automatically update the AoB.

89 · 12-27-11, 10:10 AM

Many thanks! Your answer has really helped - just shot my first ever 4km bullseye.

Just another quick question : is it true that distance is not important for "fast 90"? I saw video where someone blew up 3 or 4 ships and he just launched at them one after another as they passed his crosshair - without making any distance adjustment on the TDC. Is that really possible or was he using auto targeting?

12-27-11, 10:19 AM

It's possible. With a bit of training you even can fire and hit moving targets without TDC at a distance larger as 3 km. All you need is a eye for speed and heading.

Pisces · 12-27-11, 11:17 AM

It has nothing to do with being perpendicular to the target track (or 'fast 90' or whatever you want to call it). The range does not matter (much) if the gyro angle is close to 0. (within 10 degrees or so) In other words, if the torpedo moves pretty much straight out of the tube. If it needs to turn quite a bit then the offset position of the torpedo tubes from the periscope, together with the straight and circular section of the torpedo path will require it to turn a bit more than from the periscope vantage point. Especially if the target is near.

Setting the right speed is much more important to get a good hit. This is the prime factor in the amount of lead of the torpedo.

12-24-11, 03:18 PM	#1
89 Mate Join Date: Nov 2011 Posts: 58 Downloads: 46 Uploads: 0	Please help with "fast 90 advanced" method Merry Christmas dear subsimmers! Could someone kindly help me? - I just do not get the "advanced fast 90" (Wazoo's term). I plot my approach like he instructed, but I just can not understand at what bearing I should aim while waiting for the ship to come so I could press "fire". I have found the required angle at intersection of perpendicular course and the u-boat course (24 degrees in my screenshots below), but I do not understand how this angle is to be used. Fire at 360-24? Does not make sense. Fire at 360+24=24? Does not make sense either. Please help! Target's speed is 3knts, distance 1.7km. What do I enter into the TDC? PS I've used search and could not come up with good answers- most people talk about "basic fast 90" which does not interest me

12-24-11, 05:52 PM	#2
Mar01 Sovereign Join Date: Nov 2011 Posts: 13 Downloads: 85 Uploads: 0	That is not the angle to fire at, 360-24 is the bearing you will point the scope at, and then set the target's AoB to be 90 starboard. Then you set the TDC back to auto and just wait for the target to reach a bearing that makes the gyro angle as close to zero as you want, the TDC will automatically update the AoB. __________________ A sliver of glass somewhere in the water...

12-27-11, 11:17 AM	#5
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,904 Downloads: 304 Uploads: 0	It has nothing to do with being perpendicular to the target track (or 'fast 90' or whatever you want to call it). The range does not matter (much) if the gyro angle is close to 0. (within 10 degrees or so) In other words, if the torpedo moves pretty much straight out of the tube. If it needs to turn quite a bit then the offset position of the torpedo tubes from the periscope, together with the straight and circular section of the torpedo path will require it to turn a bit more than from the periscope vantage point. Especially if the target is near. Setting the right speed is much more important to get a good hit. This is the prime factor in the amount of lead of the torpedo. __________________ My site downloads: https://ricojansen.nl/downloads

12-27-11, 10:10 AM	#3
89 Mate Join Date: Nov 2011 Posts: 58 Downloads: 46 Uploads: 0	Many thanks! Your answer has really helped - just shot my first ever 4km bullseye. Just another quick question : is it true that distance is not important for "fast 90"? I saw video where someone blew up 3 or 4 ships and he just launched at them one after another as they passed his crosshair - without making any distance adjustment on the TDC. Is that really possible or was he using auto targeting?

12-27-11, 10:19 AM	#4
gmuno Stowaway Posts: n/a Downloads: Uploads:	It's possible. With a bit of training you even can fire and hit moving targets without TDC at a distance larger as 3 km. All you need is a eye for speed and heading.