SUBSIM Radio Room Forums - Sub turn rates?

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- - Sub turn rates? (https://www.subsim.com/radioroom/showthread.php?t=232705)

I have modified MANY variables in the game. From own ship, various targets, weapon performance and sonar buoy/dipping sonar performance.

When I do not want to play the campaign, I have created two standalone scenarios.

One is with a 12 to 15 ship SAG with SSN support. Having SSN support so close to the SAG (AI limitations) is not realistic but it is fun. It may take you two hours to play.

The other is a very unrealistic submarine Wolfpack scenario.. 8-10 submarines. This scenario may become much harder with V1.06b. I am not sure if some of my offline recommendations on Russian return fire have been implemented. Although, V1.06b will make some things much easier since torpedoes do not home in on sunken vessels..

Quote:

Originally Posted by shipkiller1 (Post 2503170)

Why would you expect any type of damage from a high speed turn?
This line of thinking is just like those who think you cannot launch a torpedo a flank.

These boats are designed to do this.

We (US boats) practice this. I would assume the Russians do also.

If your hull bends during a high speed turn then I would not want to go to sea on that type of vessel.

I did not say or expected damage in high speed turn but only wanted to know that submarine can do such fast turn without any consequences (damage, loss of control). I know that commercial cargo ships are totally different story from submarines but my question is based on past experience when I was reading about commercial cargo ships and I stumbled upon some informations that some high speed cargo ships(container ships) can experience rudder damage (rudder stock, turning mechanisme etc..)or even hull bending if they perform high speed - full rudder turns.
On end I asked one engineer who work in engine room of one big container ship about this and he told me this,
"If the ship were to try and turn as fast as possible at full speed (say another ship was stranded in her path) this would cause significant bending forces on the ships hull which can lead to permanent deformation and damage to the hull and sub structure".

Quote:

Originally Posted by Bubblehead Nuke (Post 2503174)

You experienced a situation that we called a 'snap roll'. It is more prominent in teardrop hulls that have a sail set farther back on the hull than more forward. The Permit and Sturgeon class had it but it was not too bad. The 688 class on the other hand almost lost boats due to it. I know of two incidents where control was regained only when they blew the tanks and went to the roof.

This is what happens:

(ramble mode on)

When you throw a hard rudder on the stern (back of the boat) swings out opposite direction of the turn. That is, if turning to port the stern swings to starboard.

Now this is the interesting part. If you look at sub from a side view what do you notice. You have a sail on TOP of the hull and nothing below. So the stern swings out there is more resistance to the turn on top due to the side of the sail having more dynamic pressure on the side of the sail opposite the turn. This causing a twisting of the hull around its center of rotation.

This has the effect of rolling the boat into the turn. Now the rudder that was straight up and down now has a tilt and functions as a rudder AND a stern plane. This will cause the bow to pitch down and your stern planes now act partially as a rudder when used. The causes even more forced to act on the sail and cause FURTHER rotation INTO the turn. At about 30 degrees or so roll things start to get scary, This is because your bow/fairwater planes ALSO have this tilt to them and they no longer have a up/down force but a diagonal/lateral force making recovery even more problematic.

Oh.. and this happens FAST, as in SECONDS. You will go from a nice bank and turn to 45+ down with a 60+ roll rapidly if the Vernier rudder fails. At flank speed you have VERY little time to recover.

We had premade speed/depth operation charts. Basically it was an operating envelope. At this depth go no faster than this speed without reason. It took into account the ability to recover from certain casualties.

You CAN use it to your advantage. Torpedo evasion is the best ride in the world when you have someone who knows how to use it to get the most out of maneuvers.

When you rig for high speed the planesmen , dive and COOW put on seatbelts and they activate the vernier rudder.

Bubblehead Nuke, thank you on fine explanation about this effect.:up:

Bubblehead notes that snap rolling was seen on 688's, and he's correct... right up until they were all back-fit with dihedrals... a pair of additional 'rudder-like' appendages on the 45 degree angles between the stern planes and the lower rudder. At this point, as far as I'm aware, no '88 I-flights experience this, nor do the SEAWOLF or VIRGINIA classes.

OHIO's don't either, but that's more a function of their size and top speed than anything else. Had a skipper on the ALABAMA who spent the entirety of his first patrol trying to get it to happen - lots of good high-speed operations training ensued, but no snap-rolls. We were kinda bummed about that.

Quote:

Originally Posted by Shadriss (Post 2504329)

Bubblehead notes that snap rolling was seen on 688's, and he's correct... right up until they were all back-fit with dihedrals... a pair of additional 'rudder-like' appendages on the 45 degree angles between the stern planes and the lower rudder. At this point, as far as I'm aware, no '88 I-flights experience this, nor do the SEAWOLF or VIRGINIA classes.

OHIO's don't either, but that's more a function of their size and top speed than anything else. Had a skipper on the ALABAMA who spent the entirety of his first patrol trying to get it to happen - lots of god high-speed operations training ensued, but no snap-rolls. We were kinda bummed about that.

Always wondered what those were for. They relocated the countermeasure launchers to the dihedrals, too, didn't they?

On some platforms (but not all), they have been added, but the original launchers are still in their original locations. IIRC, there are now some non-reloadable (obviously) 6-Inch CMs out there.

I created a spreadsheet to estimate sub speeds among other things.

If we assume that turn rate is inversely proportional to length, and if we use the skipjack as a baseline, we get turnrate = 231/Length.

https://docs.google.com/spreadsheets...vBU/edit#gid=2

Wow, nice! Where did the streamlining data come from?

Quote:

Originally Posted by Capt Jack Harkness (Post 2505617)

Wow, nice! Where did the streamlining data come from?

That is totally out of nowhere. My eye more than anything. Things in red are calculated. Things in blue are inputs.