Rates of climb and descent

Bellman · 07-12-05, 08:41 PM

Its a great pity my 'sheep counting' got in the way of the discussion - put it down to hunger.

Anyways extending my point about Depth changes and Course Changes in an earlier post (Xab) - here is an excellent post last night from Marconi at the Battlefront forum :-

'' No new posts in this topic for quite awhile. Here're a few musings from a 688/637 class qualified Diving Officer of the Watch:

SPEEDING UP
Acceleration of the SSNs in DW is a bit optimistic, but not as much as you might think. Attack boats CAN build speed very rapidly in an
emergency, such as torpedo evasion, but will nearly always cavitate, regardless of depth. In addition to making alot of noise,
cavitation wastes power, like a car burning rubber. Under normal circumstances the throttlman builds turns more slowly, following the
cavitation curves, which vary significantly with depth.

DEPTH CHANGES
Ordered depth excursions in DW are terrible, and the virtual DOOW needs to go back to Submarine School for retraining. Real depth changes are made with good use of ship's angle to drive the ship to the ordered depth. A common rule-of-thumb is 5 degrees up/ down angle for each 100 ft/30 mt of depth, upto a max of 15 degrees (25-30 degrees during an emergency blow). In DW the depth excursions are done with stern planes flailing around to keep the boat at zero bubble +/- 1 degree. PITIFUL.

COURSE CHANGES
Sonalysts have significantly underestimated the effectiveness of the SSN's rudder, which is huge in proportion to the ship's size. Submarine course changes in DW aren't handled very well, almost as badly as depth changes. One glaring error--at high speed (>20 kts) no sane Officer of the Deck would order a turn using full rudder, except to avoid an imminent collision. The drag of the rudder at full throw is enough to slow the ship by 50-60% during the turn. At >20 kts you can turn very quickly with 5~10 degrees rudder, while keeping most of your speed in the turn. DW's virtual OOD needs to learn this. Also, the rudder is much less effective then the ship is surfaced,
since almost half of it is out of the water.''

Bellman.

'Never send to know for whom the bell tolls...'

07-12-05, 08:41 PM	#20
Bellman Sea Lord Join Date: Feb 2004 Posts: 1,945 Downloads: 220 Uploads: 0	Its a great pity my 'sheep counting' got in the way of the discussion - put it down to hunger. Anyways extending my point about Depth changes and Course Changes in an earlier post (Xab) - here is an excellent post last night from Marconi at the Battlefront forum :- '' No new posts in this topic for quite awhile. Here're a few musings from a 688/637 class qualified Diving Officer of the Watch: SPEEDING UP Acceleration of the SSNs in DW is a bit optimistic, but not as much as you might think. Attack boats CAN build speed very rapidly in an emergency, such as torpedo evasion, but will nearly always cavitate, regardless of depth. In addition to making alot of noise, cavitation wastes power, like a car burning rubber. Under normal circumstances the throttlman builds turns more slowly, following the cavitation curves, which vary significantly with depth. DEPTH CHANGES Ordered depth excursions in DW are terrible, and the virtual DOOW needs to go back to Submarine School for retraining. Real depth changes are made with good use of ship's angle to drive the ship to the ordered depth. A common rule-of-thumb is 5 degrees up/ down angle for each 100 ft/30 mt of depth, upto a max of 15 degrees (25-30 degrees during an emergency blow). In DW the depth excursions are done with stern planes flailing around to keep the boat at zero bubble +/- 1 degree. PITIFUL. COURSE CHANGES Sonalysts have significantly underestimated the effectiveness of the SSN's rudder, which is huge in proportion to the ship's size. Submarine course changes in DW aren't handled very well, almost as badly as depth changes. One glaring error--at high speed (>20 kts) no sane Officer of the Deck would order a turn using full rudder, except to avoid an imminent collision. The drag of the rudder at full throw is enough to slow the ship by 50-60% during the turn. At >20 kts you can turn very quickly with 5~10 degrees rudder, while keeping most of your speed in the turn. DW's virtual OOD needs to learn this. Also, the rudder is much less effective then the ship is surfaced, since almost half of it is out of the water.'' Bellman. 'Never send to know for whom the bell tolls...'