Warning!
Do not read this post unless you want to know how the tests were conducted and what are the results. I warn you because I know that for some Kaleuns this would work as a spoiler (immersion killer) - many of us wish to gather such knowledge based on own experience.
Starting every patrol I conduct comprehensive set of tests to be sure everything works fine, my crew is combat ready and no French saboteur had access to my boat. Recently after being seriously bombed by British aircraft, I conducted tests of
crash dive times - the purpose was to find the fastest way of avoiding the airborne threat.
Tests were conducted in medium weather conditions (sky clear, precipitation none, visibility unlimited (aka fog none), wind 7 mps, direction 177) at deep seas.
Purpose: find the optimal
depth of cruising and
speed of cruising to make the crash dive time as short as possible.
Every single test was prepared in exactly the same start condition: 5 minutes after setting tested speed and depth, batteries and engines were checked (to be sure batteries are full and both the engines propell the boat) and then crash dive ordered. Time measured is the period between the moment of pressing C button and reaching depth of 15 metres as shown
below the Tiefenmesser (right bottom of the screen in default GWX 2.0 GUI).
Boat tested: VIIB with GW Kapselgeblase engine upgrade.
Results:
- [starting speed], [starting depth] - [average time of dive].
- 0 knots, surfaced - 37 s
- 0 knots, 6.9 metres - 21 s
- 0 knots, 7.9 metres - 28 s
- 8.5 knots, surfaced - 34 s
- 8.5 knots, 6.9 metres - 20 s
- 8.5 knots, 7.9 metres - 24 s
- flank speed, surfaced - 36 s
- flank speed, 6.9 metres - 19 s
- flank speed, 7.9 metres - 22 s
Interpretation is obvious: starting speed has very little impact on crash dive time; the faster the start speed, the faster you go down. The most important factor is the starting depth of your boat. At any speed the best results were achieved when the depth (set manually) was 6.9 m. I found it a bit surprizing, as I believed before that the deeper you go, the better. This belief however prooved to be false. Probably the reason is that 7.9 metres depth makes the boat acceleration too slow because of the drag, and the boat is unable to reach a high enough speed to dive efficiently (after ordering crash dive). 6.9 metres is a "compromise" depth - your tanks are allready partially flooded, so it takes less time to fully flood them, and at the same time the boat is still able to get enough speed before breaking the surface to dive efficiently. Depth of 7.9 metres is still much better for crash diving than 5 metres (surfaced), but it cannot compete with 6.9 m.
Some more exact test followed to find the very optimal depth. Speed of 8.5 knots was chosen as it's the optimal speed for everyday cruise with VIIB type with GW Kapselgeblase engine upgrade.
- 8.5 knots, 6.0 metres - 23 s
- 8.5 knots, 6.3 metres - 21 s
- 8.5 knots, 6.6 metres - 20 s
- 8.5 knots, 7.0 metres - 20 s
- 8.5 knots, 7.3 metres - 19 s (and the best time of 15 s!!)
- 8.5 knots, 7.6 metres - 26 s
Given the results I can quite safely asure you, that the best way of cruising areas heavily patrolled by enemy aircraft is to be at 7.0 depth and optimal speed. That, however, shortens the maximum range of your boat, as cruising decks awash consumes much more fuel than when surfaced. In my opinion shortening the crash dive time from 37 seconds to 20 seconds is worth that price.
EDIT: No Bernard or animal were killed or hurt during the tests.
