The SDV should move faster with closed hatches, because of Hydrodynamic.
With closed hatches the SDV has an smoother surface area and will not build up as much water resistance as with opened hatches.
The additional speed won't be much, though (less then 10km/h would be my guess)
However I think it would have a gameplay impact and make the open/close feature of the hatches more useful.
Ditto. The last I experience of the SDV's speed rate several weeks ago, demonstrated the vehicle operated too slowly to be of use for any mission.
Shrugs. Personally, I say toss in nice big submarine! :-) ... and I can imagine a mod implementation as I type this!
I have made a mission where I have had to start 4.5km away from the landing place to avoid being spotted by the enemy helicopter. When covering that distance, any increase in speed, however small is welcome
Also, (add this to your ticket :P) the periscope being down should reduce the drag and increase speed as well.
Well, yes, but having 2 poles with a camera on top isn't exactly the most streamlined is it?
It looks like BIS already gave the SDV some bonus as it moves a bit faster than it's real-life counterpart. Nevertheless, I think the underwater combat could profit from small improvements as it brings something fresh to the game.
Gaining additional velocity by closing hatches and lowering the periscope would be a boon to anyone seriously interested in underwater missions.
FYI.
SDV in A3: 18 kph (9.8 knots)
Swimmer delivery vehicle: 7 knots