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one.zero
12-24-2004, 01:04 AM
I recently located an interesting bit of history related to fast turns for U-boats. I knew the could go in reverse, but never really understood what mechanical design made that possible. I hope SHIII will allow independant controll of the engines. I belive the vid's or still photos from the developer showed two engine telegraphs. Based on that observation it should be possible for independant controls.

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Begin source qoute
A great number of the diesels were equiped with a second set of cams for reversing the directions of rotation of the drive shaft in order to slow the boat or move it backwards. Switching from normal cams to the reversing cams was a simple operation which required only stopping the engines and throwing a lever at each end of the cylinder bank.

Source Type VII uboats by Robert Stern

one.zero
12-24-2004, 01:04 AM
I recently located an interesting bit of history related to fast turns for U-boats. I knew the could go in reverse, but never really understood what mechanical design made that possible. I hope SHIII will allow independant controll of the engines. I belive the vid's or still photos from the developer showed two engine telegraphs. Based on that observation it should be possible for independant controls.

*********
Begin source qoute
A great number of the diesels were equiped with a second set of cams for reversing the directions of rotation of the drive shaft in order to slow the boat or move it backwards. Switching from normal cams to the reversing cams was a simple operation which required only stopping the engines and throwing a lever at each end of the cylinder bank.

Source Type VII uboats by Robert Stern

Drebbel
12-24-2004, 01:25 AM
You mean 1 fw and 1 backwards ?

Is there any proof this was ever done and that it had an reasonable effect ?

Capt.LoneRanger
12-24-2004, 01:55 AM
It was done by the Titanics Captain, who realised, that this technique was not as effective, as he estimated. - Infact it slows the turnrate down. http://forums.ubi.com/images/smilies/10.gif

one.zero
12-24-2004, 03:19 AM
yes..one forward and one reverse.

In my research thus far, consisting of ship's logs and various books the method was employed by various captains in tactical manuvering as well as dock manuvering. I cannot however detail what speeds are optimal and what subs work better or worse.

Capt.LoneRanger
12-24-2004, 03:38 AM
I doubt that. I was in the navy myself and we never ever did a thing like that, especially not under very slow speed.

The propellers cause a constant waterflow over the rudders. These rudders control the direction of the waterflow. If you are in port, this vector-based maneuvering has even a bigger effect (since this is about repulse, the bigger the difference between surrounding and accelerated water, the bigger the effect).

If you reverse one engine, the movin engine still directs the water, the other one has little more effect than to slow the ship down. Since the flow is no longer over the rudder, the steering effect is minimized.

You can use this method for breaking, yes, but not for maneuvering.

Bowfin
12-24-2004, 08:14 AM
hello

i think the only way to increase the speed
of your turn is from a standstill,run both
engines in reverse and set the rudder in the
opposite direction (left to go right) i'm not
100% sure but its seams to turn the boat faster
As for Titanic her rudder was too small for her
size,which made her turn rate very poor aswell

fherathras
12-24-2004, 08:49 AM
I have been in boats since i was born.



and sure! if you run the port(left) one in slow speed, and the starboard(right) one at slow reverse, the boat/ship will turn to starboard.



I have done it many times,
but the most efective method is ofcourse the bowthrusther. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

one.zero
12-24-2004, 10:44 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Capt.LoneRanger:
I doubt that. I was in the navy myself and we never ever did a thing like that, especially not under very slow speed. <HR></BLOCKQUOTE>

You served in diesel electrics, U-boats or S-boats? What was it like?

I can understand your hydrodynamic references made when applied to larger and sleeker hulls of today, but I belive different forces where at play with the older boats.

I can only qoute or recall what was written and what I have read. I have a very large diesel sub library and have located the mention of this tactical manuver. I will attempt to recall the specifc text where this manuver was used. It may take a bit of time but will serve as good refresher.

Have a smashing day..

Yarrick_
12-24-2004, 11:12 AM
I think that this maneuver is only available for larger boats, I supose it must be absolutely incontrlable with a small motor boat.

I also think that the risk would be that at high speed the boat keeps turning after you stop the engines going backwards.

In any case, a noisy maneouver, isn't it?

SailorSteve
12-24-2004, 12:45 PM
Steering with the propellors is a very handy thing when maneuvering in a harbor. In combat it's a problem, mainly because of the time involved in transmitting the order, stopping the proper engine, reversing the proper engine-by the time you've actually accomplished all that, it's too late for it to have any effect.

Titanic is an interesting case. If they had reversed the enginges, they still would have hit the iceberg, but head on, which would have caused damage but almost certainly less that they did recieve, and it would have been confined to the bow area; they would have had a much better chance. Had they gone to full rudder without slowing down, they might have avoided it altogether. Reversing both engines (which is what they did-not just one) and going to full rudder meant that the rudders had less effect and reduced their chance of avoiding the berg. An interesting phenomenon of ships is that they turn tighter the faster they are going.

jeroen-79
12-24-2004, 01:48 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by one.zero:
I knew the could go in reverse, but never really understood what mechanical design made that possible. <HR></BLOCKQUOTE>A gearbox?

one.zero
12-24-2004, 02:50 PM
After digging through my hard drive, I found my tactical notes for SHII.

Check out this tip for SHII tighter turns.

Pulling a Tighter Turn - (Types VII & II are best for this - type IX the worst):

(Practice this in a non-combat situation first of course) Whether running surfaced or submerged (better utilized submerged), at Full or Flank speed, set rudder to Full left or right. Right in the middle of this hard turn, set speed to Back Emergency for several seconds- until your forward speed decreases to 3 or 4 knots- then set speed to ahead Full or Flank again. You may have to zoom fairly close in to see any change - but you should see a tighter turn as you slow the boat down- and then speed up again. Seemingly comparable to real ocean dynamics.


I would include the link for the zip file from which this info came, but I cannot find an active link at this time. The source was at subsim.com as follows:

WPL member Rommel McDonald

Pr0metheus 1962
12-24-2004, 06:36 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by SailorSteve:
Titanic is an interesting case. If they had reversed the enginges, they still would have hit the iceberg, but head on, which would have caused damage but almost certainly less that they did recieve, and it would have been confined to the bow area; they would have had a much better chance. <HR></BLOCKQUOTE>

I wonder if, had they done that, anyone would have realised the awful catastrophe that was averted? Any captain who steered his ship straight into an iceberg would have faced severe criticism from people who perhaps wouldn't understand the horrifying implications of trying to avoid it.

SailorSteve
12-24-2004, 06:45 PM
Good point.

Jose.MaC
12-25-2004, 05:47 AM
I remember that, in 1998, I read an article in Scientific America about group managament. There were some examples of good and bad collaboration between people. Both of those examples were about airplanes. In one case, a passanger aircraft had a major malfuntion in the hidraulic system, so the rudder wasn't able to work. The officers knew that they could use the water in the toilet system to drive the plane, but they were pretty far from any airport, and had to save water -only had for few minutes. So to keep the bearing, they began to give different power to the engines, to get the correct angle. This way, they survived. Seems that they called other pilots that were on board.

u2336
12-26-2004, 10:12 AM
about 1 motor fw and 1 motor backw., this technic was used for manouvering in harbour.
As it was stated here, this was not effective at high speed (not effective at all indeed) even if it was written in the manuals for emergency manouverings.

Scientists showed that if the titanic quart officer had ordered a full speed ahead and rudder full starboard it could have avoided the iceberg. But you were right too, a direct hit would have certainly saved many lives.

About Beeryus comment (very good point indeed) just think of what we would have thought of the concorde captain if he had "forgotten" his procedures and if he had aborted the take off instead of continuing the take off after V2 reached. The concorde would have certainly finished its course outside the runaway, causing some damages, maybe some hurts but it would have saved many lives too. I am NOT telling the captain did a mistake, he just applied his procedures by the book. As a train driver myself I can say this dilemna is very BIG when facing a dangerous situation.

Yarrick_
12-26-2004, 10:28 AM
I had a class where our professor talked us about the Titanic incident. It seems that the desing of the ship was good enough to resist almost any problems as it was claimed, but there were a problem with the steel used in building it. Developement in chemicals in the 1900's was not good enough for scientists to discober that the steel used had an erroneus quantity of carbonide inside, so it was not flexible enough to resist damage properly, actually, taking damage made it much less resistant afterwards, so after hitting the iceberg the steel plates became to break itself, as the molecular tension between them was too high to keep on. (thus increasing the amount of water which became to enter into the ship by moments).
This also helps to explain why it break itself by half long afterwards it became to sunk.

Leif...
12-26-2004, 12:57 PM
There are no gearboxes, you have to stop the diesels, adjust the cams and restart them backwards. There are clutches however and I don€t think they would appreciate to clutch in the diesels at relatively high speed backwards while the free running propellers are turning fast the other way. Perhaps you could unclutch the diesels and turn the props backwards with the electric motor though.

However the props are so close to the centreline of the boat so the turning torque would be quite small at the same time as the propeller wash over the rudder becomes a lot smaller. As a result I think you lose both turning speed and forward speed.

Tests showed that even Bismarck with its three propellers had problems manoeuvring with props only.

Leif€¦