Dive time in v1.3 screwy?
 

I noticed yesterday that my Tambor dives better when lying still (0 kts) then when under speed. This seems strange to me, since when diving under speed uses the diveplanes, where as diving at zero speed only utilizes the ballasttanks.

Did a timing with my tambor (calm weather) from surface to PD:
speed = 0kts: 25 seconds
speed = 9 kts: 38 seconds

Shouldn't this at least be the other way around?

IT should be...the momentum of the ship and diving planes forcing the ship downward should make it dive quicker.

I would be curious to see what the response is on this one. :up:

When I first started looking at the SHIV side of these forums I was browsing through the screenshot thread a lot. I noticed a large amount of shots showing the downing of aircraft. In SHIII, I almost ALWAYS dove as soon as I spotted aircraft as did most other players that shared their stories.

When I finally got SHIV I figured out why. The subs dive terribly slow, even when crash diving. It like your only choice is to stay up and fight instead of rendering yourself so defenseless as you wait for your boat to sink below the waves.

This was true until patch 1.3 was released. Now you always get a warning when aircrafts are near you giving you plenty of time to crash dive.

Radar warning, yes. You're usually able to dive before they get on scene and in a bombing run.

US subs did take longer to dive but how long? Compared to U-boats?

Dive or crash dive?
 

In wartime, there was no casual "take her to periscope depth." EVERY dive was a crash dive and if desired they caught the sub at periscope depth as best they could. If you're just pushing "p" to dive, the real sub jockeys would laugh at you. There's only two kinds of subs: those who crash dive and those that die.

In practice, the gold standard was 60 seconds to periscope depth. Dives were practiced several time per day and if a dive was performed in over 60 seconds, woe unto the crew, for they would drill mercilessly until they could meet that standard. Good skippers tolerated grumbling crews who thought they were overdrilled because grumbling crews are still alive. A little action and a freighter or two in Davie Jones' locker will fix that just fine.

I find the dive time in acceptable limits now with 1.3. Big improvement over earlier model.

Guys, focus.

I'm not making assumptions about which sub should dive faster than the other, how that was done in a purely technical sense, or if divingspeed is altogether correct.

I am merely stating that in the current state in v1.3 (haven't tested this in earlier versions), divetime is much shorter when speed is 0 compared to when the sub is at speed. In my opinion, shouldn't this be the other way around?

Since a moving sub has added advantage of water flowing over the diveplanes as the sub is moving in the horizontal plane. A non-moving sub should therefor change depth much slower than a moving sub.

In SH3 (+GWX ofcourse), this is the case. In SH4, it seems reversed.

Moving should absolutely be faster. That's why a crash dive rings up flank. Subs in general don't seem to use the dive planes at all. All dives seem level instead of being steep.

tater

Funny, I thought the S boats dived ridicously fast and the others 'felt' right.

But its just a 'feeling' I have no real life comparisons.

Agreed, all subs should dive much faster at flank than when stationary. That's what the dive planes are for -- translate speed into downward momentum.

If they're not behaving accordingly, that's a serious problem. I think I'll add this to my investigation "to-do" list... ;)

nomad_delta

I've posted a number of times on this subject of dive behaviour. I even went so far as to test time taken to dive/rise in 50' brackets from surface to 250' and back at various speeds, from ahead 1/3 to flank.

My conclusion was this:

The dive times are hardcoded. You take x seconds to go from 50 to 100, y from 100 to 150 etc. Those times remain unaffected by your forward speed, which is totally unrealistic. The dive angle is also purely 'visual' in effect. At slow speed this is apparent as you travel more quickly vertically than horizontally, while the reverse should always be true unless you are using excessive blowing/pumping. Look at your stern planes and then look at the pitch of the sub - the two are unrelated. Changing depth once already submerged involves your stern remaining near horizontal with the stern planes on full dive/rise.

Just another 'realism' thing that's out the window.....

Thanx Nomad. I'll see if I have the time to test more subs and post my findings here. I'm a mod-noob, so I don't think i'll look into any of the files.

Ok, I've run some tests, and here's the data I've come up with so far. All tests were performed on a clean install of SH4 1.3 with no mods applied. All timing was done w/ a real stopwatch (not the one in the game) and no time compression. All commands were issued via the keyboard shortcuts, not by clicking on the depth meter. So here's the data:

http://img53.imageshack.us/img53/819...vetimeskk0.png

Here's where it gets really interesting: you'll notice in the chart there I have some of the dive times marked as "DRY" and some marked as "WET". There may be a proper term for this that I'm unaware of, but in my chart "DRY" specifies that the submarine has been surfaced for at least 20 minutes, while "WET" specifies that the submarine has been underwater very recently -- within the last couple of minutes.

You can see in the chart there that DRY vs WET makes a huge difference in overall dive times.

It took me quite a while to figure out what was happening, but it appears that it takes approximately 20 minutes for the water to "drain" out of the limber holes in your sub after you surface. You can actually watch the water draining out of the sides of the sub -- it will stop completely after about 20 minutes. If you dive again before 20 minutes is up, you'll be able to dive much faster than you would otherwise. It's not an on/off thing, either -- there's a gradual progression between the WET/DRY dive times I show in the chart during that 20 minutes.

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I don't have enough time to write up a detailed analysis of the dive times and speeds right now, but at first glance it appears that Tobus is right -- something is screwy, even once we have the 'wet' vs. 'dry' thing accounted for.

What's odd is that it's not consistent: the 'dry' normal dive times look right with Flank being faster than Stop, while the 'dry' crash dive times are about the same for Flank and Stop.

The 'wet' dive times are what really don't make any sense. Here we're seeing exactly what Tobus was talking about: both subs dive faster at "All Stop" than they do at "Flank" speed.

Another interesting thing I've learned from this is that there really is a difference between "Crash Dive" and normal "Dive" that goes beyond the fact that "Crash Dive" rings up Flank for you. Same goes for "Emergency Surface" as opposed to normal "Surface" -- definitely faster.

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I plan on collecting the same data for the remaining subs and I'll update the chart once I'm done; should be pretty interesting, I think.

nomad_delta

(edit - almost forgot something else I found that's probably important: I tried all of the above tests both a Battle Stations and not, and saw no significant difference between dive or surface times at all!)