Does anyone know what the theoretical advantage was for using inline rudders? The Germans, Italians, Russians and even British produced at least one battleship with an inline arrangement. The only advantage I can see is that they give one a spare incase of a torpedo hit on the main rudder. I have never seen any supporting evidence for this but the experience of the Bismark would tend to lend some credence to this. From every thing I have read the inline rudder added nothing to maneuverablity of the ship in question.
Really? I Would have thought it would have added quite a bit? On models the rudders are used primarily to change the jet streams coming from the props. IS this not the case with full size?
The Japanese put an aux (inline) rudder on Yamato, too. Everything I've read suggests that they did little. I expect that in our scale, a properly shaped aux rudder on ships that used them would help a lot in maneuvering whilst driving astern.
On many ships the smaller rudder was ahead of the main one. Sometimes this was actually in front of the screws. Clearly this would have no effect on the propwash. German Torpedoboats had a bow rudder in many of the classes.
One of the main reasons was redundancy... it is much less likely that a single torpedo hit or shell hit would disable both rudders... however, usually the rudder further away from the stern did not have the ability to turn the ship any where near as well (or in some cases much at all)...
In some of the German classes (Particularly Derfflinger) the larger rear rudder actually was put into turbulant flow during hard turns by the smaller forward one and turning force was reduced. This was the opposite of what was supposed to happen. I believe the designers desired a better tactical radius as high speeds but did't want to have side-by-side rudder control rooms. Obviously the concepts of fluid dynamics were still pretty young and the end result was not exactly what was hoped for. I don't think very many warships had inline rudders after 1920 or so.
None that I know of save for the Yamato's aux. rudder. The "R" class battleships had their aux rudders removed during the 1920's.
I beleive that due to the distrubance caused by the forward rudder as stated above that a lot of ship builders got a way from the in lines.That is proably why you didnt see any on later models.
I think that is probably it. The ships were all designed from 1909 to 1914 or so. There not time for the sea trials of the first ships to be reported before the later ones were laid down. I would have guessed that tank testing would have shown something but I am not sure if they tested for turning or not.
A buddy in the WWCC began building HMS Ramiles so he could also join the CalNeva Combat Club. He had both in-line rudders in place. He said he put them both in because the inline rudders help when maneuvering in reverse for our models. The project was put on hold in favor of an Omaha class light cruiser, and has since been sold to another member who likes building British ships for conversion to the WWCC.
Actually, the smaller rudder (in most cases...read not Yamato) was designed to turn in the opposite direction of the main rudder. This creates a suction effect which creates better flow over the primary rudder, and thus improves turning. There is a discussion thread with an illustration located here: http://www.bobhenneman.info/forum/viewtopic.php?t=443 which discusses this principle. Mike D
